Activated carbons and low cost adsorbents for remediation of
Journal of Hazardous Materials B137(2006)762–811
Review
Activated carbons and low cost adsorbents for remediation of
tri-and hexavalent chromium from water
Dinesh Mohan a,b,?,Charles U.Pittman Jr.a
a Department of Chemistry,Mississippi State University,Mississippi State,MS39762,USA
b Environmental Chemistry Division,Industrial Toxicology Research Centre,Post Box No.80,Mahatma Gandhi Marg,Lucknow226001,India
Received12May2006;received in revised form16June2006;accepted19June2006
Available online29June2006
Abstract
Hexavalent chromium is a well-known highly toxic metal,considered a priority pollutant.Industrial sources of Cr(VI)include leather tanning, cooling tower blowdown,plating,electroplating,anodizing baths,rinse waters,etc.The most common method applied for chromate control is reduction of Cr(VI)to its trivalent form in acid(pH～2.0)and subsequent hydroxide precipitation of Cr(III)by increasing the pH to～9.0–10.0 using lime.Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal.Far less attention has been paid to adsorption.Herein,we provide the?rst review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation.
After an overview of chromium contamination is provided,more than300papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation.Efforts to establish the adsorption mechanisms of Cr(III)and Cr(VI)on various adsorbents are reviewed.Chromium’s impact environmental quality,sources of chromium pollution and toxicological/health effects is also brie?y introduced.Interpretations of the surface interactions are offered.Particular attention is paid to comparing the sorption ef?ciency and capacities of commercially available activated carbons to other low cost alternatives,including an extensive table.
?2006Elsevier B.V.All rights reserved.
Keywords:Adsorption;Chromium;Hexavalent chromium adsorption;Trivalent chromium adsorption;Chromium removal;Chromium adsorption;Adsorbents; Solid waste utilization;Activated carbons;Low cost adsorbents
Contents
1.Introduction (763)
2.What is activated carbon? (765)
2.1.Activation (766)
2.1.1.Physical or thermal activation (766)
2.1.2.Chemical activation (767)
3.Evaluation/comparison of adsorptive properties (767)
3.1.Freundlich isotherm (768)
https://www.wendangku.net/doc/5d13481395.html,ngmuir isotherm (768)
3.3.BET isotherm (768)
4.Activated carbons (768)
https://www.wendangku.net/doc/5d13481395.html,mercial activated carbons (769)
4.2.Synthetic activated carbons (770)
5.Low cost adsorbents (778)
?Corresponding author.Tel.:+16623257616;fax:+16623257611.
E-mail address:dm1967@https://www.wendangku.net/doc/5d13481395.html,(D.Mohan).
0304-3894/$–see front matter?2006Elsevier B.V.All rights reserved.
doi:10.1016/j.jhazmat.2006.06.060
D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811763
5.1.Agricultural by-products and seeds (778)
5.2.Zeolites (781)
5.3.Nano-technology (782)
https://www.wendangku.net/doc/5d13481395.html,anic resins (782)
5.5.Fibers (783)
5.6.Carbon steel (784)
5.7.Lignite,peat,chars,and coals (784)
5.8.Hydroxide/hydrotalcite (784)
5.9.Clay minerals and oxides (785)
5.9.1.Bauxite (785)
5.9.2.Titanium(IV)oxide (785)
5.9.3.Aluminum oxide (785)
5.10.Alginate–goethite beads (785)
5.11.Gels (787)
5.12.Polymers (787)
5.13.Industrial waste/by-products (788)
5.13.1.Fly ash (788)
5.13.2.Waste sludges (788)
5.13.3.Biogas residual slurry (789)
5.13.4.Red mud (789)
5.13.5.Fertilizer waste or carbon slurries (789)
5.13.6.Blast furnace slag (789)
5.13.7.Lignin (790)
5.13.8.Miscellaneous (790)
5.14.Biosorbents (791)
5.14.1.Algae (791)
5.14.2.Fungi (792)
5.14.3.Bacteria (795)
5.14.4.Plants (796)
5.14.5.Wood,grasses,compost,peat moss (797)
5.14.6.Chitin and chitosan (797)
6.Chromium sorption mechanisms (799)
https://www.wendangku.net/doc/5d13481395.html,parative evaluation of sorbents (801)
8.Cost estimation (801)
9.Conclusions (803)
Acknowledgment (804)
References (804)
1.Introduction
Chromium was discovered in1797by the French chemist Louis Vauquelin.It was named chromium(Greek chroma,“color”)because of the many different colors found in its com-pounds.Chromium is the earth’s21st most abundant element (about122ppm)and the sixth most abundant transition metal. The principal chromium ore is ferric chromite,FeCr2O4,found mainly in South Africa(with96%of the world’s reserves),Rus-sia and the Philippines.Less common sources include crocoite, PbCrO4,and chrome ochre,Cr2O3.The gemstones emerald and ruby owe their colors to traces of chromium.
Chromium occurs in2+,3+and6+oxidation states but Cr2+is unstable and very little is known about its hydrolysis. The hydrolysis of Cr(III)is complicated.It produces mononu-clear species CrOH2+,Cr(OH)2+,Cr(OH)4?,neutral species Cr(OH)30and polynuclear species Cr2(OH)2and Cr3(OH)45+ [1–3].The hydrolysis of Cr6+produces only neutral and anionic species,predominately CrO42?,HCrO42?,Cr2O72?[2,3].At low pH and high chromium concentrations,Cr2O72?predomi-nates while at a pH greater than6.5,Cr(IV)exists in the form of CrO42?[2].Cr(III)is classi?ed as a hard acid and forms relatively strong complexes with oxygen and donor ligands. Chromium(VI)compounds are more toxic than Cr(III)due to their high water solubility and mobility.On the other hand,triva-lent chromium is insoluble and thus immobile under ambient conditions.The most soluble,mobile and toxic forms of hex-avalent chromium in soils are chromate and dichromate.The hexavalent form is rapidly reduced to trivalent chromium under aerobic conditions[4].Insoluble trivalent hydroxides and oxides form which cannot leach.
Chromium has both bene?cial and detrimental properties. Chromium(III)is an essential trace element in mammalian metabolism.In addition to insulin,it is responsible for reducing blood glucose levels,and is used to control certain cases of dia-betes.It has also been found to reduce blood cholesterol levels by diminishing the concentration of(bad)low density lipopro-teins“LDLs”in the blood.Cr(III)is supplied in a variety of
764 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)
762–811
Fig.1.Eh–pH diagram for chromium.Source:Palmer and Puls[309]. foods such as Brewer’s yeast,liver,cheese,whole grain breads and cereals,and broccoli.Chromium is claimed to aid in muscle development.In fact,dietary supplements containing chromium picolinate(its most soluble form)are very popular with body builders.In contrast,Cr(VI)is hazardous by all exposure routes.
The redox potential Eh–pH diagram(Fig.1)presents equi-librium data and indicates the different oxidation states and chemical forms which exist within speci?ed Eh and pH ranges. Cr(III)is the most thermodynamically stable oxidation state under reducing conditions(Fig.1).Cr(VI)can remain sta-ble for signi?cant periods of time.Cr(III)predominates at pH<3.0.At pH>3.5,hydrolysis of aqueous Cr(III)yields triva-lent chromium hydroxy species[CrOH2+,Cr(OH)2+,Cr(OH)30 and Cr(OH)4?].Cr(OH)30is the only solid species,exist-ing as an amorphous precipitate[5].Hexavalent chromium exists primarily as salts of chromic acid(H2CrO4),hydro-gen chromate ion(HCrO4?)and chromate ion(CrO42?
),
Fig.2.Speciation diagram of Cr(VI).Source:Dionex[6]. depending on the pH.H2CrO4predominates at pHs less than about1.0,HCrO4?at pHs between1.0and6.0,and CrO42?at pHs above about 6.0(Fig.2)[6].The dichromate ion (Cr2O72?),a dimer of HCrO4?,minus a water molecule,forms when the concentration of chromium exceeds approximately 1g/L.
Acute exposure to Cr(VI)causes nausea,diarrhea,liver and kidney damage,dermatitis,internal hemorrhage,and respira-tory problems[3].Inhalation may cause acute toxicity,irritation and ulceration of the nasal septum and respiratory sensitization (asthma)[2,3,7].Ingestion may affect kidney and liver func-tions.Skin contact may result in systemic poisoning damage or even severe burns,and interference with the healing of cuts or scrapes.If not treated promptly,this may lead to ulceration and severe chronic allergic contact dermatitis.Eye exposure may cause permanent damage.The drinking water guideline recom-mended by Environmental Protection Agency(EPA)in US is 100?g/L.
Industrial processes that produce aqueous ef?uents rich in chromium and other heavy metals are given in Table1. Chromium compounds are widely used in electroplating,metal ?nishing,magnetic tapes,pigments,leather tanning,wood pro-
Table1
Heavy metals in some major industries
Industry source Al Zn As Sn Ag Sb Cd Cr Cu Fe Hg Mn Pb Ni Bi Automobile X X X X X X X Petroleum re?ning X X X X X X X
Pulp and paper X X X X X X
Textile X
Steel X X X X X X X X Organic chemicals X X X X X X X X X
Inorganic chemicals X X X X X X X X
Fertilizer X X X X X X X X X X X
Plastic and synthetics X
Leather tanning and?nishing X
Steel power plants X X
Mining X X X X X X
Acid mine drainage X X X X X
Metal plating X X X X
Glass X
Nuclear power X Coal and gasoline X X X
D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811765
Table2
Global discharges of trace metals(1000metric tonnes/year)[287]
Metals Water Air Soil Arsenic411982 Cadmium9.47.422 Chromium14230896 Copper11235954 Lead138332796 Mercury 4.6 3.68.3 Nickel11356325 Selenium41 3.841 Tin ND 6.4ND Zinc2261321372 tection,chemical manufacturing,brass,electrical and electronic equipment,catalysis and so on(Table1)[7].Contaminants from industrial wastewater rich in heavy metal ions remain an impor-tant environmental issue.Although control technologies have been applied to many industrial and municipal sources,the total quantity of these agents released to the environment remains staggering(see Table2).
Several treatment technologies have been developed to remove chromium from water and https://www.wendangku.net/doc/5d13481395.html,mon meth-ods include chemical precipitation[8],ion exchange[9–14], membrane separation[15,16],ultra?ltration[17],?otation[18], electrocoagulation[19],solvent extraction[20],sedimentation [21],precipitation[22],electrochemical precipitation[22],soil ?ushing/washing[22],electrokinetic extraction[22],phytore-mediation[22],reduction[23],reverse osmosis[24],dialy-sis/electrodialysis[25],adsorption/?ltration[2,3,26–30],evap-oration,cementation,dilution,air stripping,steam stripping,?occulation,and chelation[31].Chemical precipitation has tra-ditionally been the most used method.The most often used precipitation processes,include hydroxide precipitation,sul-?de precipitation,carbonate precipitation and phosphate pre-cipitation.The disadvantage of precipitation is the production of sludge.This constitutes a solid waste a disposal problem. Ion exchange is considered a better alternative.However,it is not economically appealing because of high operational costs.
Most remediation methods more effectively remove chromium from water/wastewater containing relatively high ini-tial chromium concentrations(usually above100mg/L).Advan-tages and disadvantages of various treatment methods are sum-marized in Table3[32].Adsorption has evolved as the front line of defense for chromium removal.Selective adsorption by bio-logical materials,mineral oxides,activated carbons,or polymer resins has generated increasing excitement[1,26,30,32–39]In general,activated carbons are broadly applied effective adsor-bents for wastewater treatment.
The origin of carbon use extends so far back into history that it is impossible to document.Charcoal was?rst used for drinking water?ltration by ancient Hindus in India,and carbonized wood was used as a medical adsorbent and purifying agent by the Egyptians as early as1500b.c.[40].
A number of review articles have appeared on activated carbon adsorption,and the use of other low cost adsorbents [1,33–35].Allen et al.[34]reviewed the production and charac-terization of activated carbon from many carbonaceous sources. Characterization by porosimetry,sorptometry,topography,pore size distribution,isotherms,and surface area measurements was reviewed and the speci?c data from activated carbons derived from lignocellulosic materials(peat and lignite)were also presented.Pollard et al.[33],reviewed low cost alterna-tives to activated carbon for water/wastewater treatment.Car-bon selection criteria and activation methods were discussed [33].Similar types of review articles later appeared on low cost alternatives to activated carbons[30,32,36].Davis et al.
[37]presented an excellent review of the biochemistry of heavy metal biosorption by brown algae.Gavrilescu[41]dis-cussed the removal of heavy metals by biosorption.Biosorp-tion of heavy metals by fungal biomass and its modeling was also reviewed[39].Mui et al.[42]reviewed the production of active carbons from waste tires.Kapoor and Viraraghvan [38]reviewed fungal biosorption as an alternate treatment option for heavy metal bearing wastewaters.However,to the best of our knowledge,no review exists of activated carbons or alternative adsorbents used for chromium adsorption from water/wastewater.
Compiling the research on chromium removal by adsorp-tion is important because this topic has advanced signi?cantly.
A large number of publications appear every year.Many sig-ni?cant papers published during last two decades are reviewed herein.The term“signi?cant”is,of course,our interpretation with which others may differ.Particular attention has been paid to comparing the sorption ef?ciency of commercially available activated carbons with other low cost alternatives.An extensive table summarizing the sorption capacities of various activated carbons and/or other adsorbents is included.
2.What is activated carbon?
The basis for modern industrial production of active carbons was established in1900–1901to replace bone char in the sugar re?ning process[43].Powdered activated carbon was?rst pro-duced commercially in Europe in the early19th century,using wood as a raw material.The use of activated carbon for the water treatment in the United States was?rst reported in1930, for the elimination of taste and odor from contaminated water [44].Activated carbon is a crude form of graphite with a ran-dom or amorphous structure,which is highly porous,exhibiting a broad range of pore sizes,from visible cracks,crevices and slits of molecular dimensions[45].Active carbons have been prepared from coconut shells,wood char,lignin,petroleum coke,bone char,peat,sawdust,carbon black,rice hulls,sugar, peach pits,?sh,fertilizer waste,waste rubber tire,etc.(Table4). Wood(130,000tonnes/year),coal(100,000tonnes/year),lignite (50,000tonnes/year),coconut shell(35,000tonnes/year),and peat(35,000tonnes/year)are most commonly used[33].Acti-vated carbons adsorptive properties are due to such factors as surface area,a micro-porous structure,and a high degree of sur-face reactivity.
The starting material and the activation method used for activated carbon production determine surface functional
766 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811
Table3
Advantages and disadvantages of commercial activated carbons,synthetic ion-exchange resins and polysaccharide-based sorbents for solution remediation Adsorbent Advantages Disadvantages
Activated carbon ?The most effective adsorbent?Expensive
?Very high surface areas?The higher the quality,the greater the cost ?Porous sorbent?Performance is dependent on the type of carbon
used
?High capacity and high rate of adsorption
?Requires complexing agents to improve its
removal performance
?Great capacity to adsorb a wide range of pollutants
?Fast kinetics
?A high quality-treated ef?uent is obtained?Non-selective
?Problems with hydrophilic substances
?Ineffective for disperse and vat dyes
?High reactivation costs
?Reactivation results in a loss of the carbon
Ion-exchange resin ?Wide range of pore structure and physicochemical characterization?Expensive
?Good surface area?Derived from petroleum-based raw materials ?Effective sorbent?Sensitive to particle
?Excellent selectivity towards aromatic solutes?Performance is dependent on the type of resin used ?Regeneration:no adsorbent loss?Not effective for all dyes
?pH-dependence
?Poor contact with aqueous pollution
?Requires a modi?cation for enhanced the water
wetability
Chitosan-based material ?Low cost natural polymer?Nonporous sorbent
?Environmentally friendly?The sorption capacity depends of the origin of the
polysaccharide and the degree of N-acetylation ?Extremely cost-effective
?Outstanding metal and dye-binding capacities?Variability in the bead characteristics
?High ef?ciency and selectivity in detoxifying both very dilute or
concentrated solutions excellent diffusion properties
?pH-dependence
?Requires chemical modi?cation to improve its
performance
?High quality-treated ef?uent is obtained
?Versatile sorbent?Low af?nity for basic dyes
?Easy regeneration if required
Starch-based material ?Very abundant natural biopolymer and widely available in many countries?Low surface area
?Renewable resource?Requires chemical derivatization to improve its
sorption capacities
?Economically attractive and feasible
?Easy to prepare with relatively inexpensive reagents?Variability in the bead characteristics
?Its use in sorption columns is limited since the
characteristics of the particles introduce
hydrodynamic limitations and column fouling ?A remarkably high swelling capacity in water
?Good removal of wide range of pollutants
?Important selectivity for different concentrations
?Fast kinetics
?Amphiphilic crosslinked adsorbent
?Applicable to a wide variety of process
?Easy regeneration if required
Source:Crini[32],with permission from Elsevier.
groups.Carbon surface chemistry has been studied extensively [1,43,46].The carbon surface chemistry depends upon the acti-vation conditions and temperatures employed.Activation also re?nes the pore structure.Mesopores,micropores and ultrami-cropores are formed yielding large surface areas up to2000m2/g [1,35].
2.1.Activation
During the activation process,the spaces between the ele-mentary crystallites are cleared by removal of less organized loosely bound carbonaceous material.The resulting channels through the graphitic regions,the spaces between the elemen-tary crystallites,together with?ssures within and parallel to the graphite planes constitute the porous structure,with a large inter-nal surface area[47].Two types of activation,thermal/physical or chemical activation,impart a porous structure within a start-ing material of relatively low surface area.
2.1.1.Physical or thermal activation
Physical or thermal activation involves carbonization at 500–600?C to eliminate the bulk of the volatile matter followed by partial gasi?cation using mild oxidizing gas such as CO2, steam or fuel gas at800–1000?C to develop the porosity and surface area[35,48].
2.1.2.Chemical activation
Chemical activation involves the incorporation of inorganic additives,metallic chlorides such as zinc chloride or phos-
D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811767
Table4
Alternative feedstocks proposed for the preparation of activated carbons[33,35] Bones Lampblack
Bagasse Leather waste
Bark Municipal waste
Beat-sugar sludges Molasses
Blood Nut shells
Blue dust News paper
Coal Oil shale
Coffee beans Olive stones
Coconut shell Petroleum acid sludge Coconut coir Pulp-mill waste
Cereals Palm tree cobs Carbohydrates Petroleum coke Cottonseed hulls Petroleum acid sludge
Corn cobs Potassium ferrocynide residue Distillery waste Rubber waste
Fuller’s earth Rice hulls
Fertilizer waste slurry Re?nery waste
Fish Ref?nation earth
Fruit pits Scrap tires
Graphite Sun?ower seeds
Human hairs Spent Fuller’s earth
Jute stick Tea leaves
Kelp and seaweed Wheat straw
Lignin Wood
Lignite
phoric acid into the precursor before the carbonization[34]. Carbons with well-developed meso-and microporous struc-ture can be produced by ZnCl2incorporation.KOH activation successfully increased active carbon surface area and pore vol-ume[49].Ammonium salts,borates,calcium oxide,ferric and ferrous compounds,manganese dioxide,nickel salts,hydrochlo-ric acid,nitric acid and sulfuric acid have also been used for activation.
The basic differences between physical and chemical acti-vation is the number of stages required for activation and the activation temperature.Chemical activation occurs in one step while physical activation employs two steps,car-bonization and activation.Physical activation temperatures (800–1000?C)are higher than those of chemical activation (200–800?C).
According to Steenberg’s classi?cation[50],acidic and basic activated carbons exist:
(a)Carbon activated at200–400?C,called L carbons,generally
develop acidic surface oxides and lower solution pH values.
They adsorb bases,are hydrophilic,and exhibit a negative zeta potential.
(b)The carbons activated at800–1000?C,termed H carbons,
develop basic surface oxides and raise solution pH.They adsorb acids and exhibit a positive zeta potential.However, cooling H carbons in contact with air changes the zeta poten-tial to a negative value due to the formation of acidic surface oxides.
The acidic groups on activated carbons adsorb metal ions[51].The L carbons are stronger solid acids than the Table5
List of low cost adsorbents used in wastewater treatment[33,35]
Bagasse Red mud Bagasse?y ash Rubber waste Bark Rice hulls
Coal Re?nery waste Coconut shell Scrap tires
Corn cobs Slag
Clay minerals Sludge
Fuller’s earth Sun?ower seeds Fertilizer waste slurry Spent Fuller’s earth Ferrocynides Tea leaves
Fly ash Old tires
Lignin Wheat straw Lignite Wood Lampblack Wool waste Leather waste Zeolites
Olive stones
H carbons and more ef?ciently adsorb metal ions.Sur-face area may not be a primary factor for adsorption on activated carbon.High surface area does not necessarily mean high adsorption capacity[52]due to the following factors:
(a)Only the wetted surface adsorbs ions.The total surface area
is seldom wetted.
(b)Sometimes the material to be adsorbed is too large to enter
the smallest pores where the bulk of the surface area may exist.
(c)Surface area,pore volume and surface chemistry are not
usually correlated with species adsorbed.
The adsorption of metal ions on carbon is more complex than uptake of organic compounds because ionic charges affect removal kinetics from solution.Adsorption capacity depends on activated carbon properties,adsorbate chemical properties, temperature,pH,ionic strength,etc.Many activated carbons are available commercially but few are selective for heavy metals. They are expensive.
Despite carbon’s proli?c use to treat wastewater,it remains expensive,requiring vast quantities of activated carbon. Improved and tailor-made materials are sought.Substitutes should be easily available,cheap and,above all,be readily regen-erated,providing quantitative recovery.
Industrial or agricultural by-products can be converted into activated carbons or low cost adsorbents.Table5lists various materials,which have been investigated.
3.Evaluation/comparison of adsorptive properties
Adsorption equilibrium measurements are used to determine the maximum or ultimate adsorption capacity.Six types of adsorption isotherms[35,53]exist including types I–VI.Equi-librium isotherm data are formulated into an adsorption isotherm model.
768 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 Feed solution is contacted in stirred vessels with a de?nite
quantity of activated carbon/adsorbent in batch experiments.The
important design parameters are calculated from batch adsorp-
tion isotherms,which model full-scale batch processes.The
most commonly used models include Freundlich,Langmuir,and
BET isotherms.The batch adsorption processes are inef?cient
and capital intensive so column adsorption processes are used
commercially.
3.1.Freundlich isotherm
This isotherm developed by Freundlich[54]describes the
equilibrium on heterogeneous surfaces and does not assume
monolayer capacity.
The Freundlich equation is
q e=K F C1/n e(nonlinear form)(1)
log q e=log K F+1
n log C e(linear form)(2)
where q e is the amount of solute adsorbed per unit weight of activated carbon(mg/g),C e the equilibrium concentra-tion of solute in the bulk solution(mg/L),K F a constant indicative of the relative adsorption capacity of the adsor-bent(mg/g)and the constant1/n indicates the intensity of the adsorption.
https://www.wendangku.net/doc/5d13481395.html,ngmuir isotherm
The Langmuir adsorption isotherm describes the surface as homogeneous assuming that all the adsorption sites have equal adsorbate af?nity and that adsorption at one site does not affect adsorption at an adjacent site[55,56].The Langmuir equation may be written as
q e=Q0bC e
1+bC e
(nonlinear form)(3)
C e q e =1
Q0b
+1
Q0
C e(linear form)(4)
where q e is the amount of solute adsorbed per unit weight of adsorbent(mg/g),C e the equilibrium concentration of solute in the bulk solution(mg/L),Q0the monolayer adsorption capacity (mg/g)and b is the constant related to the free adsorption energy.
b is the reciprocal of the concentration at which half saturation of the adsorbent is reached.
3.3.BET isotherm
The BET(Brunauner,Emmett,Teller)isotherm assumes the partitioning of a compound between liquid and solid phases. This isotherm assumes multi-layer adsorption of solute occurs [56,57]:
q e=
BCQ0
(C s?C)[1+(B?1)(C/C s)]
(nonlinear form)
(5)
https://www.wendangku.net/doc/5d13481395.html,parative evaluation of adsorbents.
q e=
C
(C s?C)q e
=1
BQ0
+
B?1
BQ0
C
C s(liner form)(6)
where q e is the amount of adsorbate adsorbed per unit weight
of activated carbon,B the constant related to the energy of
interaction with the surface,C the equilibrium concentration
of adsorbate in solution(mg/L or mol/L),Q0the number of
moles of adsorbate per unit weight of carbon to form a com-
plete monolayer,and C s is the saturation concentration of the
adsorbate.
Various sorbents have been compared based on percent
removal.This is a crude and rather inaccurate misleading
approach.Isotherms are always(Langmuir)more accurate than
percentage removal to compare two sorbents because isotherms
have more experimental points.
Fig.3shows four different adsorption experiments.Each
curve gives different results depending upon equilibrium con-
centration where the percent removal was calculated.If the
sorption capacities were calculated at point1,the capacity order
is D>B>C>A while at point2the order is D>C>B>A.
Thus,it is dif?cult to compare various sorbents in terms of per-
cent removal.Sorption capacity should be calculated in mg/g
using sorption models,particularly the Langmuir adsorption
model.
Activated carbons,waste materials,industrial by-products,
agricultural waste products,biosorbents,etc.,have been used for
the removal and recovery of chromium[Cr(III)and Cr(VI)]from
water/wastewater.For simplicity,in this review article,adsor-
bents are divided into two classes:
(1)activated carbons;
(2)other low cost adsorbents.
4.Activated carbons
Activated carbons can be further subdivided into commercial
activated carbons and synthetic activated carbons.
D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811769
https://www.wendangku.net/doc/5d13481395.html,mercial activated carbons
Many commercial activated carbons have been used as received and also after chemical modi?cations for Cr(VI)and Cr(III)adsorption.Important contributions in this direction were made by Huang and coworkers[58–61]and also by other groups [62–74].The dominating mechanism for Cr(VI)removal in most of the studies is surface reduction of Cr(VI)to Cr(III)followed by adsorption of Cr(III).
Cr(VI)adsorption from aqueous solutions by lab-made high surface area(HSA)-activated carbons exhibited higher sorption capacities than commercial carbons[63].A pH of～3.0was optimum for Cr(VI)adsorption.Both micropores and meso-pores make important contributions to Cr(VI)adsorption but desorption is more dependent on the mesoporosity.Thus,regen-eration was easier for carbons having high mesoporosity.Cr(VI) adsorption mechanism was not discussed.
Huang and Wu[61]showed that Cr(VI)adsorption by acti-vated carbon,?ltrasorb400(Calgon),occurred by two major interfacial reactions:adsorption and reduction.Cr(VI)adsorp-tion reached a peak value at pH5.0–6.0.Carbon particle size and the presence of cyanide do not change the magnitude of chromium removal.Cr(III)is less adsorbable than Cr(VI).The free energy of speci?c chemical interaction, G chem,was com-puted by the Gouy–Chapman–Stern–Grahame model. G chem was?5.57RT and?5.81RT,respectively,for Cr(VI)and CN. These values were large enough to in?uence the magnitude of both Cr(VI)and CN adsorption.HCrO4?and Cr2O72?were the major Cr(VI)species involved in surface association.
Rivera-Utrilla and Sanchez-Polo[67]analyzed the effect of oxygenated surface groups on Cr(III)sorption using a series of ozonized activated carbons[carbon F,carbon F10,carbon F120(Calgon Carbon Corp.)].The adsorption capacity of the oxidized carbon was greater than that of the original carbon. This effect is due to the formation of surface oxygen groups that,through their ionization,increase the attractive electrostatic interactions between the surface of the activated carbon and the metallic cations present.At pH2.0,almost all the Cr(III) was found as Cr3+cation(hexahydrated),whereas at pH12.0 it was found as Cr(OH)4?anion.At pH6.0where the adsorp-tion isotherms were obtained,the predominant species were: Cr(OH)2+(60.61%)and Cr(OH)2+(38.24%).The adsorption of cationic Cr(III)species on basic carbons with surface posi-tive charge density was explained by C?–cation interactions.In these processes,the ionic interchange of C?–H3O+-interaction protons for metallic cations plays a determinant role.According to the pH PZC values of the carbon samples,the mean surface charge density at pH6.0is positive(carbon F),near zero(car-bon F10)or negative(carbon F120).The attractive electrostatic interactions between the Cr(III)species and the carbon would increase in the order:F Park and Jang[64]studied hydrochloric acid-and sodium hydroxide-treated activated carbons(ACs)for Cr(VI)reduc-tion.The surface pH and acid–base values were measured and FT-IR,and X-ray photoelectron spectrometer(XPS)analyses were performed.Porosity was characterized by N2/77K adsorp-tion.Cr(VI)adsorption and reduction depended on both micro-porous structure and surface functionality.Cr(VI)was more effectively adsorbed by acid-treated activated carbons.How-ever,base-treated activated carbons were not effective Cr(VI) adsorbents,probably due to the decrease of speci?c surface area. Fluka carbons(particle size of100–150?m;speci?c surface area1100m2/g)were modi?ed by immobilizing tetrabutylam-monium iodide(TBAI)and sodium diethyl dithiocarbamate (SDDC)on their surfaces[68].These carbons were used for cop-per,zinc,chromium and cyanide removal.TBAI(417?mol/g) and SDDC(295?mol/g)were adsorbed.TBAI and diethyl dithiocarbamate-treated carbons adsorbed more CN?,Cu,Zn and Cr than unmodi?ed carbon. The effect of anodic surface treatment of activated carbons on their Cr(VI)adsorption properties under reaction-treatment time conditions with35wt.%HCl solution was investigated[75].The acidic surface functional groups increased with increasing HCl reaction-treatment time.Speci?c surface area,total pore volume, net heat of adsorption,and BET’s,slightly decreased during anodic surface treatments of activated carbons.Adsorption was controlled more by the acid–base interactions between electron-donor substances and acidized activated carbons as electron acceptor than by the pore structures. Aggarwal et al.[65]reported Cr(III)and Cr(VI)adsorption on activated carbon?bers and activated carbons in20–1000mg/L concentration range.Activated carbon surfaces further modi?ed by oxidation with nitric acid,ammonium persulfate,hydrogen peroxide or oxygen gas at350?C were used after degassing at different temperatures.Cr(III)removal increased when the oxidized carbons were used decreased on degassing.Con-versely,adsorption of Cr(VI)ions decreased on oxidized car-bons and increased on degassing.The increase of Cr(III)and the decrease of Cr(VI)on oxidized carbons was due to acidic groups on the carbon surface.The decrease of Cr(III)and the increase of Cr(VI)on degassed carbons occurred because degassing removed these acidic groups.Acidic surface groups enhanced the Cr(III)adsorption and suppressed Cr(VI)adsorp-tion.Chromic ions exist in aqueous solutions as[Cr(H2O)6]3+. These associated water molecules are exchanged with the hydroxyl ions.The number exchanged depends on the pH of the solution as shown in Fig.4.pH changes are caused by changes in amount of acidic carbon–oxygen surface groups.These,in turn,change the extent of the positive charge on the chromic ion.These changes in the surface negative charge resulting from oxidation and the changes in the positive charge on the Cr(III) ions in solution favor the adsorption of Cr(III)ions because attractive electrostatic interactions between the carbon surface and the chromium ions present in the solution are enhanced. Degassing reduces electrostatic attractive interactions,resulting in a decrease in the Cr(III)adsorption.When all the surface oxy-Fig.4.Aqueous Cr(III)species present versus pH. 770 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 gen complexes are thermally desorbed on degassing at950?C, little or no Cr(III)adsorption occurs. Commercial activated carbon was treated with HNO3to intro-duce surface oxygen complexes,and subsequently heated up to 873K in N2to eliminate some of the these complexes[76]. The three samples used for Cr(III)and Cr(VI)adsorption gave enhanced removal.Leyva-Ramos et al.[70]investigated Cr(III) adsorption on commercial activated carbon in the pH range of2.0–6.0.At pH<2.0Cr(III)was not adsorbed and at pH values>6.4Cr(III)precipitated as Cr(OH)3.Maximum adsorp-tion occurred at pH5.0.The adsorption capacity increased by about20%as the temperature was raised from25to40?C. Cr(VI)removal by two commercial granular activated carbons (GACs)in batch and continuous-?ow modes was investigated [72].Cr(VI)removal decreased with increase in pH from4.0to 7.5.Dissolved oxygen(DO)removal from experimental systems enhanced GAC performance,but pretreatment of the GACs with reductants(ferrous iron or dithionite)did not improve Cr(VI) removal.Regeneration of spent carbons was accomplished by equilibration with0.01M dibasic potassium phosphate to extract adsorbed Cr(VI)followed by a wash with0.02N sulfuric acid to remove precipitated-sorbed Cr(III). Cr(VI)removal from water by coconut shell,wood and coal dust based activated carbons was studied[77].The coconut shell and coal dust activated carbons have protonated hydroxyl groups on the H-type carbons surface,while the surface of the wood-based activated carbon has ionized hydroxyl groups(L-type carbons).The optimum pH was2.0for wood-based activated carbon,while for coconut shell and coal dust activated car-bons,the optimum pH was～3.0–4.0.Babel and Kurniawan [73]investigated coconut shell charcoal(CSC)and commer-cial coconut shell activated carbon(CAC)for Cr(VI)removal. Surface modi?cations of CSC and CAC with chitosan and/or oxidizing agents(such as sulfuric acid and nitric acid)were car-ried out.The oxidized adsorbents performed better.Nitric acid oxidized CSC and CAC had higher Cr adsorption capacities (CSC:10.88mg/g,CAC:15.47mg/g)than sulfuric acid oxi-dized(CSC:4.05mg/g,CAC:8.94mg/g)and non-treated CSC coated with chitosan(CSCCC:3.65mg/g)carbons,respectively. It was assumed that the following physicochemical interactions occurred during chromium removal M n++n(–COOH) (–COO)n M+n H+(7) where(–COOH)represents the CSC surface functional groups and n is the coef?cient of the reaction component,depending on the oxidation state of metal ions,while M n+and H+are Cr(III) and hydrogen ions,respectively. Thus,reduction of Cr(VI)oxyanions is accompanied by a large amount of proton consumption in the acidic solution.This con?rms the decisive role played by H+in Cr(VI)removal.It was also reported that the Cr(VI)/Cr(III)redox potential strongly depends on pH.At pH≈1.0,E0≈1.3V and at pH≈5.0, E0≈0.68V,indicating that improving the redox potential of the oxidant extends the oxidation towards the more resistant surface functionalities.The pH of synthetic wastewater ranges from5.0 to6.0,where Cr(III)mostly exists as[Cr(OH)]2+,formed by the hydrolysis of Cr(III)as follows Cr3++H2O [Cr(OH)]2++H+(p K1=3.85)(8) The second mechanism controlling the adsorption of Cr(III)on the carbon surface of CSC is represented as Cr3++H2O [Cr(OH)]2++H+(9) HA+[Cr(OH)]2+ ([Cr(OH)]2+–A?)+H+(10) where A represents an adsorption site on the acidic surface of CSC. Combining these two equations gives on overall Cr(III) adsorption reaction: Cr3++H2O+HA ([Cr(OH)]2+–A?)+2H+(11) Chromium(VI)adsorption from dilute aqueous solutions onto modi?ed activated carbons at natural pH values was achieved[69].As expected surface reduction of Cr(VI)to Cr(III) appeared to be the principal chromium adsorption mechanism for the activated carbons studied.Oxidizing agents changed the adsorption capacity of Cr(VI)on the carbons.Cr(VI)removal from water on a commercial activated carbon occurred through reduction Cr(VI)to Cr(III)and adsorption,resulting in predom-inant attachment of Cr(VI)species with less Cr(III)species[60]. 4.2.Synthetic activated carbons As discussed in Sections2.1.1and2.1.2,the production of activated carbon involves carbonization and activation.Car-bonization consists of slow heating in the absence of air to the pyrolysis temperature,usually below600?C,where volatiles are removed.Then chemical or physical activation is performed. Physical activation involves of treating chars with steam,carbon dioxide,or oxygen at elevated temperature.Chemical activa-tion is carried out in the presence of chemical activants such as ZnCl2,H2PO4,H2SO4,KOH,K2S,and KCNS[33,35].These chemical activants promote the formation of cross-links giving a rigid matrix less prone to volatilization and volume contrac-tion when heated to a high temperature.Zinc chloride is the most widely used chemical dehydrating agent(catalyst)[33,35].Post-activation is also required to remove residual catalyst,which may be reclaimed for the subsequent reuse.Some important feedstocks containing an activant and other conditions used for activated carbons development are listed in Table6.The most commonly used feed stocks include fertilizer waste[28,78,79], coconut shells and coconut shell?bers[2,3],wood[80],nuts [81],sawdust[82–85],waste tires[85],cow dung[86];rice hulls[87]bagasse[88],coir pith[89]and lignin[66]. Waste carbon slurry generated in fertilizer plants in India was converted into a low cost activated carbon[28,78,79]and utilized for the removal of heavy metals from water/wastewater.Kinetic studies were also conducted to determine various parameters necessary to design?xed bed reactors[79].To establish opti-mum deign parameters,mini column adsorption studies were performed and a mass transfer kinetic approach was success-fully applied[28].The length of the primary adsorption zone D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811771 (δ),total time involved for the establishment of primary adsorp-tion zone (t x ),mass rate of ?ow to the absorber (F m ),time for primary adsorption zone to move down its length (t δ),amount of adsorbate adsorbed in the primary adsorption zone from break-point to exhaustion (M s ),fractional capacity (f ),time for initial formation of adsorption zone (t f )and per cent saturation of col-umn at break point were all studied.Chemical regeneration was achieved with 1M HNO 3. A variety of low cost activated carbons were developed from coconut shell ?bers and coconut shells [2,3].The car-bons are designated as FAC (activated carbon derived from coconut ?bers),SAC (activated carbon derived from coconut shells),ATFAC (activated carbon derived from acid-treated coconut ?bers),and ATSAC (activated carbon derived from acid-treated coconut shells).These were characterized,and utilized for hexavalent chromium removal [2].A commer-cial activated carbon fabric cloth was also tested.Trivalent chromium adsorption from water was restricted to ATFAC and ACF [3].The optimum pHs for Cr(VI)and Cr(III)adsorp-tion were 2.0and 5.0,respectively.The Langmuir adsorp-tion model ?tted the Cr(III)and Cr(VI)adsorption data better than the Freundlich model.At 25?C,Cr(VI)removal followed the order ACF (96.30mg/g)>FAC (21.75mg/g)>ATSAC (11.51mg/g)>ATFAC (9.87mg/g)>SAC (9.54mg/g)[2]while the maximum adsorption capacities of ATFAC and ACF at 25?C were 12.2and 39.56mg/g,respectively [3].Overall,the activated carbon fabric cloth performed best.The adsorption capacities of these carbons and the activated carbon fabric cloth were comparable to those of the available adsorbents/activated carbons (Table 7). Aqueous Cr(VI)uptake onto activated carbons (AC)pro-duced from wood was investigated [80].A KOH-activated car-bon and a commercial H 3PO 4-activated carbon (Acticarbone CXV)were tested.Cr(VI)removal was maximized at pH 3.0and increased with temperature for both adsorbents.The KOH-activated carbon had a higher Cr(VI)sorption capacity than Acticarbone.Favorable adsorption at low pH was due to the neu-tralization of negative surface charges by excess hydrogen ions.This facilitates diffusion of hydrogen chromate ions (HCrO 4?)and their subsequent adsorption.HCrO 4?was the dominant Cr(VI)anion between pH 1.0and 4.0.This ion was preferen-tially adsorbed on the carbon surface.The negative charges could result from basic oxygenated functions,chemisorbed at pore surfaces.Under acidic conditions,Cr(VI)could be reduced to Cr(III)in the presence of activated carbon.The authors failed to explore the dominating mechanism. Several activated carbons were prepared from Terminalia arjuna nuts,an agricultural waste,by chemical activation with zinc chloride and then tested for aqueous Cr(VI)remediation [81].The most important chemical activation parameter was the activating agent/precursor (g/g).A high surface area (1260m 2/g)was obtained at a chemical ratio of 3,after 1h of carbonization at 500?C.The isotherm equilibrium data ?t well to both the Lang-muir and Freundlich models.The maximum Cr(VI)uptake was obtained at pH 1.0.Authors failed to explain the dominating Cr(VI)adsorption mechanism. Table 6 Some chemical activant–feedstock couples to prepare activated carbon for chromium removal from water/wastewater Feed stock Carbonization Activation Reference Agent Conditions Coconut shells H 2SO 4,150–65?C,24h –600?C/1h [2,3]Coconut shell ?bers H 2SO 4,150–65?C,24h –600?C/1h Leather N 2/900?C/5h CO 2825?C/8h [95] N 2/900?C/5h CO 2825?C/45h Olive stone N 2/900?C/2h H 3PO 4480?C/3h N 2/900?C/2h ZnCl 2725?C/3h N 2/900?C/2h H 2O 860?C/2h N 2/900?C/2h CO 2 820?C/72h Almond shell N 2/900?C/2h ZnCl 2+CO 2(3:1)agent:raw material;820?C/69h Norit CA-1 –H 3PO 4–Proqui?Andujar 39– H 3PO 4– Casurina equisetifolia leaves H 2SO 4and 10%Na 2HPO 4(1:1)425?C for 1h in the absence of air –850?C/30min [92] ZnCl 2/425?C for 1h in the absence of air – 850?C/30min Hazelnut shell (Corylus avellana )H 2SO 4/150?C for 24h – – [90]Eucalyptus grandis sawdust 800?C in a N 2atmosphere CO 2(D);air (A)800/400?C [84]Cornelian cherry (CC),apricot stone (AS)and almond shells (ASC)1:1(w/w)with concentrated H 2SO 4for 24h –200?C/24h [91]Fertilizer slurry H 2O 2/H 2O N 2450?C,1h [28,78,96]Used tires/sawdust 900?C/N 2/2h CO 2900?C/2h [85]Cow dung 1:1(w/w)with concentrated H 2SO 4for 24h ––[86]Hevea brasiliensis sawdust 1:2(w/w)with phosphoric acid/24h/110?C – 400?C/1h [82]Lignin H 3PO 4 350–600?C [66] 772 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 Table 7 Comparison of activated carbons and other low cost adsorbents for chromium [Cr(III)and Cr(VI)]removal Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)Composite alginate–goethite beads 2.020Langmuir 27.18.9[169] 3.020Langmuir 23.420.7 4.020Langmuir 20.530.43.040Langmuir 27.124.13.060Langmuir 29.52 5.3Raw rice bran 5.025Freundlich 0.070.1[112]Hevea brasiliensis (rubber wood)sawdust activated carbon 2.030Langmuir 44.1–[82]2.040Langmuir 59.2–2.050Langmuir 65.8–Coir pith 3.327Langmuir –11.6 [103]Palygorskite clay 7.025Langmuir 58.5[164] Activated carbons (CKW) 3.025Langmuir 180.3[80] 6.025Langmuir 95.19.025Langmuir 33.43.033Langmuir 281.33.040Langmuir 315.6Activated carbon (Acticarbone CXV) 3.025Langmuir 12 4.66.025Langmuir 32.49.025Langmuir 17.53.033Langmuir 144.43.040Langmuir 186.1Maghemite nanoparticles 2.522.5Freundlich 7.8–[126] 3.522.5Freundlich 6.3–5.022.5Freundlich 3.4–8.022.5Freundlich 1.9–10.022.5Freundlich 1.5–2.510.0Freundlich 1.4–2.522.5Freundlich 1.4–2.535.0Freundlich 1.4–Soybean hulls 3.025Langmuir 58.2–[136] Sugarcane bagasse 3.025Langmuir 103–Corn stover 3.025Langmuir 83.7–Native saltbush (stems) 5.0–Langmuir 0.0016.3[255] Native saltbush (leaves) 5.0–Langmuir 0.122.7Native saltbush (?ower) 5.0–Langmuir 0.127.0Esteri?ed saltbush (stems) 5.0–Langmuir 3.4 5.5Esteri?ed saltbush (leaves) 5.0–Langmuir 4.1 6.1Esteri?ed saltbush (?ower) 5.0–Langmuir 3.17.1Hydrolyzed saltbush (stems) 5.0–Langmuir 0.020.8Hydrolyzed saltbush (leaves) 5.0–Langmuir 0.425.1Hydrolyzed saltbush (?ower) 5.0–Langmuir 0.326.2Cross-linked (glutaraldehyde) 4.0 –Langmuir 2156[275] A.?avus biomass (live) 30Langmuir 0.2–[273] A.?avus biomass (autoclaved)30Langmuir 0.3–A.?avus biomass (acid-treated)30Langmuir 0.1–A.?avus biomass (alkali-treated)30Langmuir 0.2–A.?avus biomass (detergent-treated) 30Langmuir 0.2–Native biomass of N.crassa (ATCC 12526) 1.025Freundlich 0.4–[234] Heat inactivated of N.crassa (ATCC 12526) 1.025Freundlich 9.2–Sodium hydroxide of N.crassa (ATCC 12526) 1.025Freundlich 7.4–Acetic acid of N.crassa (ATCC 12526) 1.025Freundlich 15.9–Ground nut shell (GS) 4.010Langmuir 5.9–[115] 4.010Langmuir ––Walnut shell (WS) 4.010Langmuir 2.3–4.010Langmuir 18.4–Almond shell (AS) 4.010Langmuir 22.0–4.010Langmuir 2.4–T.indica seed (TS) 2.050Langmuir 98.0–4.050Langmuir 55.3–6.0 50 Langmuir 80.0 – D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 773 Table 7(Continued )Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)8.050Langmuir 23.0–Native algae (Chlamydomonas reinhardtii ) 2.025Langmuir 25.0–[288] Heat-treated algae (Chlamydomonas reinhardtii ) 2.025Langmuir 30.2–Acid-treated algae (Chlamydomonas reinhardtii ) 2.025Langmuir 25.6–Activated carbon prepared from Terminalia arjuna nuts 1.025Langmuir 28.4–[81]Isparta–Yalvac ?–Yarikkaya (YK)coal 4.525Langmuir –16.2[152]Kasikara (KK)coal 4.525Langmuir – 5.4Agave lechuguilla biomass 2.010Langmuir 25.9–[253] 2.022Langmuir 34.6–2.040Langmuir 35.6–M.hiemalis 2.027Langmuir 47.4–[235]2.040Langmuir 51.0–2.050Langmuir 5 3.5–B.thuringiensis (vegetative cell) 2.025Langmuir 28.6–[247]B.thuringiensis (spore–crystal mixture) 2.025Langmuir 34.2–Lewatit MP 62anion exchange resin 5.025Langmuir 21.6–[131] Lewatit M 610anion exchange resin 5.025Langmuir 22.1–Lentinus sajor-caju (untreated) 2.025Langmuir 19.6–[230]Lentinus sajor-caju (heat-treated) 2.025Langmuir 33.1– Lentinus sajor-caju (HCl-treated) 2.025Langmuir 25.8Lentinus sajor-caju (NaOH-treated) 2.025Langmuir 27.7Carrot residues 4.525Langmuir –4 5.1[116]Ferric chloride impregnated-sponi?ed sugar beet pul 4.425Langmuir 5.1–[289] 4.435Langmuir 4.9–4.445Langmuir 4.6–Carboxymethylcellulose (CMC) 2.025Langmuir 5.1–[212] Free mycelia of Lentinus sajor-caju 2.025Langmuir 18.9–Immobilized mycelia (in carboxymethylcellulose (CMC))of Lentinus sajor-caju 2.0 25 Langmuir 32.3 – Sawdust ––Freundlich 1.5–[102]Rice husks ––Freundlich 0.6–Coir pith ––Freundlich 0.2–Raw stevensite 3.025Dubinin–Radushkevich 0.7–[159]Fe-stevensite 3.025Dubinin–Radushkevich 2.6–Cone biomass of Thuja oriantalis 1.517Langmuir 49–[256]Quaternary chitosan salt (QCS) 4.525Langmuir 68.3–[276]9.025Langmuir 30.2–Uncalcined hydrotalcite 2.0–2.125Freundlich 4.6–[35]Amberlite IR-120resin –20Langmuir –67.7[129]Pantoea sp.TEM18 3.025Langmuir 204.1–[248]Bauxite 2.020Langmuir 0.5–[167]2.035Langmuir 0.5–2.050Langmuir 0.4–Hydrous titanium(IV)oxide 2.025Langmuir 5.0[165]Aeromonas caviae ,a gram-negative bacteria 2.520Langmuir 284.4–[245] 2.540Langmuir 181.5–2.560Langmuir 169.1–Activated carbon from co-mingled natural organic wastes 3.730Langmuir –56.7[95] 3.735Langmuir –56.23.740Langmuir –56.63.745Langmuir –43.5Norit carbon (oxidized) 3.722Langmuir –25.63.730Langmuir –52.53.740Langmuir –53.03.750Langmuir –45.9Beech (Fagus orientalis L.)sawdust ～1.025Langmuir 16.1 – [252] 774 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 Table 7(Continued )Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)Wine processing waste sludge 4.020Langmuir –10.5[186]4.030Langmuir –13.54.040Langmuir –1 5.44.050Langmuir –1 6.4Polyacrylonitrile ?bers (APANFs) 5.0–– ～16～5[137]Peat 4.022–25Extended Langmuir –22.4[267]Bio-polymeric beads of cross-linked alginate and gelatin 8.925Langmuir 0.8–[169]Ocimum basilicum seeds 1.525Langmuir 205–[119]Bagasse ?y ash 5.030Langmuir – 2.5[176]5.040Langmuir – 2.35.050Langmuir – 2.1Protonated dry alginate beads 3.525Langmuir –57.0[170] 4.525Langmuir –77Fe-modi?ed steam exploded wheat straw 3.025Langmuir 9.1–[105]Solvent impregnated resins 4.025Langmuir 50.4–[134]Persimmon tannin (PT)gel 3.025Langmuir 274.0–[172]Distillery sludge 3.025Langmuir 5.7–[187]Ion exchange resin 1200H 3.825Langmuir 8 4.0–[12]Ion exchange resin 1500H 3.825Langmuir 188.7–Ion exchange resin IRN97H 3.825Langmuir 58.1–Hydrotalcite 6.025Freundlich 120.0–[158]Maple sawdust 6.025Langmuir 5.1– [101]Pitch-based activated carbon ?bers,ACF30M 3.025Langmuir 23.7[138] Pitch-based activated carbon ?bers,ACF45M 3.025Langmuir 2 4.9–Activated carbon,FS-100 3.0–Langmuir 69.3–[63] Activated carbon,GA-3 3.0–Langmuir 101.4–Activated carbon,SHT 3.0–Langmuir 69.1–Activated carbon,CZ-105 3.0–Freundlich 40.4–Activated carbon,CZ-130 3.0–Freundlich 44.9–Activated carbon,CK-22 3.0–Freundlich 47.4–Activated carbon,CK-26 3.0–Freundlich 45.6–Free biomass 2.030Freundlich 27.6–[231] Polysulfone entrapped biomass 2.030Freundlich 17–Polyisoprene immobilized biomass 2.030Freundlich 15.6–PV A immobilized biomass 2.030Freundlich 1 3.4–Calcium alginate entrapped biomass 2.030Freundlich 9.6–Polyacrylamide biomass 2.030Freundlich 2.3–SI resin prepared using HP-20 4.030Langmuir 38.0–[133]SI resin prepared HP-2MG 4.030Langmuir 40.0–Dunaliella alga (sp.1) 2.025Langmuir 111.0–[213]2.025Langmuir 102.5–Inorganic–organic silicon hybrid matrices ––– –29.12[156]Cone biomass of Pinus sylvestris 1.025Freundlich 38.4–[257]PAC 2.025Langmuir 0.03– [177]Bagasse 6.025Langmuir 0.0005Flyash 6.025Langmuir 0.001Immobilized dried activated sludge 1.025Langmuir 18.9[197] Granular activated carbon 1.025Langmuir 147.1–Wool 2.030Langmuir 41.2–[100] Olive cake 2.030Langmuir 33.4–Sawdust 2.030Langmuir 15.82–Pine needles 2.030Langmuir 21.5–Almond 2.030Langmuir 10.6–Coal 2.030Langmuir 6.78–Cactus 2.030Langmuir 7.08–Soya cake <1.020Langmuir 0.00028–[120]Activated sludge 1.025Langmuir 294.0–[188]Activated sludge 4.525Langmuir 9 5.2–Cation-exchange resin,IRN77 3.5 25 Freundlich 35.4 – [11] D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 775 Table 7(Continued )Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)Untreated R.nigricans 2.030Langmuir 123.5–[232]CTAB-treated R.nigricans 2.030Langmuir 140.8– PET-treated R.nigricans 2.030Langmuir 161.3APTS-treated R.nigricans 2.030Langmuir 200.0Biomass of ?lamentous algae Spirogyra species 2.018Langmuir 14.7–[211] Carbonaceous adsorbent from waste tires (TAC) 2.022Langmuir 48.1–[85] 2.030Langmuir 55.3–2.038Langmuir 58.5–Carbonaceous adsorbent from sawdust (SPC) 2.022Langmuir 1.9–2.030Langmuir 2.2–2.038Langmuir 2.3–Carbon,F-400 2.022Langmuir 44.4–2.030Langmuir 48.5–2.038Langmuir 5 3.2–IRN77resin 3.525Freundlich –35.4[10]SKN1resin 3.525Freundlich –46.3Dried anaerobic activated sludge 1.025Langmuir 577.0–[198]Red mud 2.030Langmuir 22.7–[29] 2.040Langmuir 21.6–2.050Langmuir 21.1–Tannin gel (66%water content) 2.030–192.020.0[173]Tannin gel (72%water content) 2.030–224.028.0Tannin gel (75%water content) 2.030–235.038.0Tannin gel (77%water content) 2.030– 287.050.0Cow dung carbon 3.430Langmuir 10.0–[86]Carbon C3 3.025Langmuir 35.0–[92]Carbon C4 3.025Langmuir 15.0–Algae,Chlorella vulgaris 2.025Langmuir 27.3–[214]Insoluble straw xanthate (ISX) 3.6–3.925Langmuir – 1.9[118]Alkali-treated straw (ATS) 3.6–3.925Langmuir – 3.9Algae,C.vulgaris 2.025Langmuir 79.3–[215]Algae,S.obliquus 2.025Langmuir 58.8–Algae,Synechocystis sp. 2.025Langmuir 15 3.6–Algae,C.vulgaris 2.025Freundlich 6.0–[217]Peat 2.025–30.7–[268]4.025– –14.0Free biomass of R.arrhizus 2.0–Freundlich 11.0–[226] Immobilized biomass of R.arrhizus 2.0– Freundlich 8.6–GAC-S –Langmuir –13.3[65] GAC-E –Langmuir –10.5ACF-307–Langmuir –7.1ACF-310 –Langmuir – 3.5Polymer-grafted sawdust 3.030Langmuir 12.2–[97]3.040Langmuir 9.4–3.050Langmuir 7.6–3.060Langmuir 6.2–Dithizone-anchored poly(EGDMA-HEMA)microbeads 5.025Langmuir –62.2[171]Aspergillus biomass 5.028Langmuir 23.615.6[229]R.arrhizus 2.025Langmuir 58.1–[227]Leaf mould 2.525Column capacity 25.9–[107]Activated carbon 2.52575.6–Biogas residual slurry 1.5030Langmuir 5.87–[193]Peat moss 2.025Column capacity 65.8–[269]Irish sphagnum peat 2.525Column capacity 35.5–[270]2.025Column capacity 4 3.9–Chitosan impregnated with a microemulsion 3.530Langmuir 61.4–[277]3.540Langmuir 81.9–3.550Langmuir 85.6–Lignocellulosic substrate 2.1–Langmuir 35.0–[108]Chitosan 4.0 25 Langmuir 154 – [278] 776 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 Table 7(Continued )Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)Sargassum wightii Seaweed 3.5–3.825Langmuir 35.0–[220]Surface-modi?ed jacobsite (MnFe 2O 4) 2.025Langmuir 31.5–[127]Protonated brown seaweed Ecklonia sp. 2.020–25– 233.5–[294]Aeromonas caviae biomass 2.520Langmuir 284.4–[245] Activated carbon,FAC 2.010Langmuir 16.0–[2] Activated carbon,SAC 2.010Langmuir 1.4–Activated carbon,ATFAC 2.010Langmuir 1.1–Activated carbon,ATSAC 2.010Langmuir 1.6–Activated carbon fabric cloth 2.010Langmuir 116.9–Activated carbon,FAC 2.025Langmuir 21.8–Activated carbon,SAC 2.025Langmuir 9.5–Activated carbon,ATFAC 2.025Langmuir 10–Activated carbon,ATSAC 2.025Langmuir 11.5–Activated carbon fabric cloth 2.025Langmuir 96.3–Activated carbon,FAC 2.040Langmuir 24.1–Activated carbon,SAC 2.040Langmuir 32.6–Activated carbon,ATFAC 2.040Langmuir 15.6–Activated carbon,ATSAC 2.040Langmuir 16.4–Activated carbon fabric cloth 2.040Langmuir 42.1–Activated carbon,ATFAC 5.010Langmuir –11[3] 5.025Langmuir –12.25.040Langmuir –1 6.1Activated carbon fabric cloth 5.010Langmuir –3 6.15.025Langmuir –39.65.040Langmuir –40.3Activated carbon,A 3.030Langmuir –0.8[84]Activated carbon,D 3.030Langmuir –0.4Activated carbon,OA 3.030Langmuir –31.5Activated carbon,OD 3.030Langmuir –26.3PEI-modi?ed biomass of P .chrysogenum 4.625Langmuir 279.2–[228]Fleshing from animal hides/skins 4.025Langmuir 51.0–[202]Treated ?eshing from animal hides/skins 4.025Langmuir 9.0–Carbon slurry 2.530Langmuir 24.1–[290]2.545Langmuir 2 5.2–2.560Langmuir 25.6–Biogas residual slurry 2.530Langmuir –7.8[194]Coniferous leaves 3.030Freundlich 6.3–[262]London leaves 3.020Langmuir 68.0–[261]3.030Langmuir 75.8–3.040Langmuir 83.3–Brown seaweed (Turbinaria spp.) 3.530Langmuir –31[223]Cork powder 4.022Langmuir – 6.3[109]Hazelnut shell activated carbon 1.030Langmuir 170–[90]Kendu fruit gum dust (KGD) 1.0 30Freundlich 218–[110]Carbon slurry 30Langmuir 24.1–[195]45Langmuir 25.2–60Langmuir 25.6–Cationic surfactant-modi?ed yeast 4.5–5.520Langmuir 94.3–[244] Amine-modi?ed polyacrylamide-grafted coconut coir pith 3.0 20Langmuir 127.3–[104] 30Langmuir 123.4–40Langmuir 111.4–50Langmuir 108.4–Dowex 3.030Langmuir 109.3–Sawdust (SD)of rubber wood (Hevea brasiliensis )was grafted with polyacrylamide 3.020Langmuir 14 4.2–[99] 3.030Langmuir 153–3.040Langmuir 158.7–3.050Langmuir 166.7–3.060Langmuir 172.4–As received CSC 6.025Langmuir 2.2–[73] CSC coated with chitosan 6.025Langmuir 3.7–CSC oxidized with sulfuric acid 6.0 25 Langmuir 4.1 – D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 777 Table 7(Continued )Adsorbents pH Temperature (?C) Model used to calculate adsorption capacities Adsorption capacity (mg/g)Reference Cr(VI)Cr(III)CSC oxidized with sulfuric acid and coated with chitosan 6.025Langmuir 9–CSC oxidized with nitric acid 6.025Langmuir 11–As received CAC 6.025Langmuir 4.7–CAC oxidized with sulfuric acid 6.025Langmuir 8.9–CAC oxidized with nitric acid 6.025Langmuir 10.4–Agave lechuguilla biomass 2.010Langmuir 2.5–[259] 2.022Langmuir 3.3–2.040Langmuir 3.4–Fly ash 2.030Langmuir 1.4[179] Fly ash impregnated with aluminum 2.030Langmuir 1.8–Fly ash impregnate with iron 2.030Langmuir 1.7–Japanese ceder (Cryptomeria japonica ) 3.030Langmuir 71.9–[263]3.040Langmuir 80.0–3.050Langmuir 90.9–Larch bark 3.030Langmuir 31.3–[264]Fly ash-wollastonite 2.025Langmuir 2.9[291]Sawdust 2.025Langmuir 39.7–[292]Sugar beet pulp 2.025Langmuir 17.2–Maize cob 1.525Langmuir 13.8–Sugarcane bagasse 2.025Langmuir 1 3.4–Dried Chlorella vulgaris 2.025Langmuir 27.8–[217]Chitosan cross-linked with epichlorohydrin 3.025Langmuir 11.3–[293]Chitosan coated on perlite 4.025Langmuir 153.8–[280]Metal ion imprinted chitosan 5.525Langmuir 51.0–[281] Chitosan cross-linked with epichlorohydrin 5.525Langmuir 52.3–Metal ion imprinted chitosan cross-linked with epichlorohydrin 5.525Langmuir 51.0–Chitosan cross-linked with ethylene glycol diglycidyl ether 5.525Langmuir 5 6.8–Bagasse ?y ash 1.030Langmuir 259.0–[27]1.040Langmuir 123.7–Activated carbon developed from fertilizer waste slurry 2.027Langmuir 371.0–[78]2.045Langmuir 17 3.0–Blast furnace slag 1.030Langmuir 1.45–[181]1.040Langmuir 1.76– Activated carbon obtained from black liquor lignin 7.025Langmuir 40.0–56.0[66] 3.025Langmuir 80.0–92.6Cement kiln dust ––Langmuir 33.3– [204]Activated carbon,F 6.025Langmuir 7.3[67]Activated carbon,F10 6.025Langmuir 10.7Activated carbon,F120 6.025Langmuir 19.2Brown coal,YK 3.025Langmuir 47.83[153] Brown coal,KK 3.0 25 Langmuir 50.95 Hazelnut shell activated carbon was developed from Corylus avellane species for Cr(VI)removal from water [90].Cr(VI)adsorption was best achieved in the pH range of 1.0–2.0.The maximum adsorption capacity calculated using Langmuir model was 170mg/g at pH 1.0.Under acidic conditions Cr(VI)reduced to Cr(III).Cornelian cherry (CC),apricot stone (AS)and almond shells (ASC)were converted into activated carbons and used for Cr(VI)removal from aqueous solution [91].The optimum pH was 1.0.Sorption capacities for various activated carbons were not reported. Rubber wood sawdust [82],sawdust [83],eucalyptus sawdust [84]were converted to activated carbons.Sawdust carbons were characterized and used for Cr(VI)[82,83]and Cr(III)[84]reme-diation.Karthikeyan et al.[82]examined Cr(VI)adsorption onto activated carbon from Hevea brasiliensis (rubber wood)saw-dust.Cr(VI)removal peaked at pH https://www.wendangku.net/doc/5d13481395.html,ngmuir,Freundlich and Temkin isotherms were used to describe the adsorption equi-librium data.Maximum adsorption in acidic pHs indicated that an increase in the surface H +ion concentration resulted in strong electrostatic attractions between the surface and chromate ions.No consideration was given to the reduced Cr(III).Bishnoi et al.[83]concluded that the improved chromium removal at low pH (2.0)by sawdust activated carbon was due to Cr(VI)reduction to trivalent chromium.No adsorption capacity was reported.Eucalyptus sawdust was converted into activated carbon by CO 2[84].These carbons were then treated with concentrated 778 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 70wt.%HNO3at80?C to obtain and the corresponding oxi-dized carbons were used for Cr(III)remediation.HNO3oxida-tion enhanced the ability to retain Cr(III)due to a signi?cant increase in oxygenated surface groups.Other non-acidic func-tions,which evolve CO upon temperature programmed desorp-tion,contributed to Cr(III)uptake.Signi?cant adsorption into the micropores took place although oxidation of the active car-bons leads to a narrowing of the average micropore widths. Casurina equisetifolia leaves.C.equisetifolia leaves were carbonized and then activated with sulfuric acid(1:1),a phos-phate salt(10%)or zinc chloride(25%)[92].Different tem-peratures were employed to get these activated carbons[92], which were then used to remove Cr(VI).Data were?tted with the Freundlich model.Adsorbed chromium was65–80%des-orbed by alkali followed by acid treatments.Carbon recycling was achieved without changing in the sorption ef?ciency.Rice husk-based activated carbons were prepared using KOH and NaOH as activation agents[93].The porous carbon prepared with KOH(RHCK)had higher surface area(3000m2/g)than the carbon(2500m2/g)prepared using NaOH.Reduction of Cr(VI) into Cr(III)was not considered at low pH.Neither data set was modeled by Langmuir/Freundlich equations nor were the max-imum sorption capacities(monolayer)determined.Chromium removal by rice hull-based activated carbon(RHAC)and Cal-gon’s F-400was investigated[87].Chromium was successfully removed only by F-400. A variety of activated carbons in powder and granular form were developed from leather,olive stone,almond shells by different activation procedures[94].These carbons were used for Cr(VI)removal.The porous texture of the activated car-bons was characterized by adsorption of N2/77K and methy-lene blue/298K.Cr(VI)adsorption increased with increasing pH and initial Cr(VI)concentration.At pH<1.0,the retention of Cr(VI)was due to its reduction to Cr(III).The lower the pH the greater the reduced tendency.The extent of adsorption and reduction depended on the porous texture,and procedure used to prepare the activated carbons.Physical activation gives the best performance.Cr(VI)removal by carbonaceous adsor-bents produced from pyrolysis/activation of waste tires(TAC), pyrolysis of sawdust(SPC)and a commercially available car-bon(F400)was investigated[85].Pyrolysis was carried out at a heating rate of20?C/min for2h to reach the pyrolysis temperature(900?C).After pyrolysis,the product was acti-vated by CO2at900?C for2h.The sawdust was pyrolyzed at650?C at the same conditions used for tires.Maximum adsorption occurred at pH2.0for all carbons(Table7)because Cr(VI)was adsorbed as HCrO4?which predominates between pH1.0and4.0.Reduction of Cr(VI)to Cr(III)was not con-sidered.The sorption data were modeled using the Langmuir isotherm. Activated carbons prepared from co-mingled natural organic wastes[95]and a commercially available carbon(Norit)were used for Cr(III)removal.Total chromium uptake by the co-mingled waste activated carbon was higher then by Norit acti-vated carbon under similar conditions(1.09and1.01mmol/g, respectively,at30?C)(Table7).The operating adsorption mechanism at pH3.7was a rapid ion exchange of aque-ous chromium ions followed by their surface hydrolysis and slow chemisorption and/or an outer-sphere complexation.The ?rst hydrolytic species probably converts to inner-sphere com-plexation with time.Cr(VI)removal from aqueous medium by cow dung activated carbon was achieved[86].Cow dung was carbonized and activated by treating with concentrated H2SO4and heating for24h at120?C.At lower pH(<3.5), this carbon removed～90%of Cr(VI)present at5ppm in a synthetic aqueous solution.No adsorption mechanism was explored. Activated carbon produced by graphite electrode arcing in an inert atmosphere was employed for aqueous Cr(VI)and Cr(III)removal[96].This carbon selectively removed hexava-lent chromium anions from solution,whereas,little or no uptake of[Cr(III)]was observed versus solution pH. High BET surface area activated carbons with well-developed porosity by pyrolysis of H3PO4-impregnated lignin precipitated from kraft black liquors.These lignin-derived carbons were used for Cr(VI)remediation[66].H3PO4/lignin(w/w)impreg-nation ratios between1and3and activation temperatures of 350–600?C were used.Higher activation temperatures and the impregnation ratios widen the pore structure,producing a higher contribution of mesoporosity.Impregnation ratios of～2and activation temperatures around425?C were recommended as the best operating conditions to prepare activated carbons for chromium remediation. 5.Low cost adsorbents 5.1.Agricultural by-products and seeds Agricultural wastes have been applied as adsorbents for hexa and trivalent chromium remediation from water.The most commonly used agricultural by-products include sawdust [97–100,102],coir pith[102–104]straw[105],husks[106],leaf mould[107],wheat bran[108],cork powder[109],fruit gum dust[110],sugar beet pulp[111],rice bran[112],rice hulls [113],bark[114],and nut shells[115]. Tamarindus indica seeds(TS),crushed coconut shells (CS),almond shells(AS),ground nut shells(GS)and wal-nut shells(WS)were used for Cr(VI)removal[115].Hex-avalent chromium sorption capacity followed the sequence (TS)>(WS)>(AS)>(GS)>(CS)(Table7).Cr(VI)sorption by TS decreased with rising pH,and dropped slightly with higher ionic strengths.Cr(VI)removal occurred by chemisorption on TS.Desorption of Cr(VI)from Cr(VI)laden TS was quite favored by NaOH versus distilled water and HCl.Whether Cr(VI)adsorption occurred as chromate anions or reduced Cr(III)at low pH is not known.Recently,baggase,charred rice husks,activated charcoal and eucalyptus bark(EB)were tested for chromium removal[114].EB provided the highest Cr(VI) removal capacity.The maximum Cr(VI)adsorption occurred at pH2.0.The sorption capacity was45mg/g of adsorbent at a Cr(VI)concentration of250mg/L in the ef?uent. The anion exchange properties of soybean hulls after quat-ernizion with N-(3-chloro-2-hydroxypropyl)trimethylammo-nium chloride,in a strongly alkaline environment was inves- D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811779 tigated[113].This modi?cation converted the hulls to an anion exchanger.Modi?ed hulls exhibited a larger uptake of anions compared with the unmodi?ed hulls. Raw rice bran adsorbed chromium and nickel from aqueous solutions[112].Capacities were calculated using the Freundlich isotherm(Table7).Cr(III),Cu(II)and Zn(II)were all removed from aqueous solution by carrot residues[116].These lignocel-lulosic residues contained up to12%of the weight of the original fruit.Metals cations were bound by carboxylic acid and pheno-lic groups.The Freundlich and Langmuir models described the sorption equilibria of Cr(III),Cu(II)and Zn(II).No adsorption mechanism was discussed. An adsorbent from sugar beet pulp by iron(III)hydroxide loading was used for Cr(VI)removal[111].Sugar beet pulp was subjected to saponi?cation,ferric chloride impregnation, hydrolysing and heating.Cr(VI)adsorption and reduction to Cr(III)occur using sugar beet pulp-based materials.Cr(VI) reacts with organic matter leached from pulp to produce Cr(III). The following reduction mechanism was proposed HCrO4?+organic matter+H+→Cr3++H2O(12) or CrO42?+CO2(and/or oxidized products)(13) Sawdust,rice husks,coir pith,charcoal and vermiculite were used for aqueous Cr(VI)removal[102].Cr(VI)adsorp-tion capacities followed the order sawdust=coir pith>rice husks>charcoal and vermiculite(Table7).Chromate anions and reduced Cr(III)both adsorbed but no quanti?cation of Cr(VI)and Cr(III)was attempted.Formaldehyde and sulfuric acid-treated Indian Rosewood sawdust,a timber industry waste, was employed for Cr(VI)adsorption[117].Maximum removal occurred at an initial pH of3.0.Neither sorption capacities nor the sorption mechanisms were reported. Heavy metals removal using alkali-treated straw(ATS)and insoluble straw xanthate(ISX)were explored[118].Insoluble straw xanthate consisting of4.1%total sulfur was also applied for the simultaneous removal of several metal ions.Potentiomet-ric data from alkali-treated straw and xanthated straw con?rmed their polyfunctionality.Diffuse re?ectance IR(DRIFT)spec-tra of ISX exhibited characteristic xanthate peaks.Removal of Cr3+from aqueous solutions using ATS and ISX followed the Langmuir model and both the materials removed>80%of the chromium.Pore adsorption preceded the surface adsorption with chromate and dichromate.Detailed spectroscopic(DRIFT and EPR)and sodium release studies conducted on ISX suggested that Cr3+is removed through an adsorption-exchange mecha-nism involving alkoxide or xanthate groups.Xanthate groups bind Cr3+aqua complexes via unidentate monosulfur chelation. Basic groups on ATS and ISX participated in the interaction with Cr3+.Removal of Cr3+via an ion-exchange route takes place according to the following reactions: 3(–CH2O–Na+)+Cr3+→(–CH2O)3Cr+3Na+(14)3(–CH2OCS2?Na+)+Cr3+→(–CH2OCS2)3Cr+3Na+ (15)–CH2O?Na++Cr3+→–CH2OCr2++Na+(16)–CH2OCS2?Na++Cr3+→–CH2OCS2Cr2++Na+(17) –CH2O?Na++[Cr(H2O)6]3+ →–CH2O?Cr(H2O)52++Na++H2O(18) –CH2OCS2?Na++[Cr(H2O)6]3+ →–CH2OCS2–Cr(H2O)52++Na++H2O(19) Three equivalents of Na+are released into solution(Eq.(15)) for each Cr3+exchanged.One equivalent of Na+was released for each Cr3+exchanged(Eqs.(16)and(17)).However,the exchange ratio for ATS and ISX was close to one.This indi-cates that exchange took place according to Eqs.(16)and(17). If Cr3+is considered to exist as[Cr(H2O)6]3+in aqueous solu-tions,Eqs.(16)and(17)can be rewritten as Eqs.(18)and(19). [Cr(H2O)6]3+was exchanged as a dicationic aqua species with the participation of–CH2O?Na+or–CH2OCS2?Na+. Polymer-grafted sawdust was synthesized and used it for Cr(VI)removal from aqueous solution[97].An empirical rela-tionship was obtained to predict the percentage Cr(VI)removal at any time for known values of adsorbent and initial adsor-bate concentration.Other ions had little effect on the sorption of Cr(VI).The data?tted the Freundlich model.This adsorbent was effectively regenerated using0.2M NaOH and0.5M NaCl. Variations in adsorption were explained by taking into account this adsorbent’s af?nities for the different Cr(VI)species of coex-isting at acidic pH(Cr2O72?,HCrO4?,Cr3O102?,Cr4O132?). Above pH8.0,only CrO42?is stable.As the pH decreased to 3.0–6.0,the equilibrium shifts to dichromate according to the overall equilibrium: 2CrO42?+2H+?Cr2O72?+H2O(20) At lower pH values,Cr3O102?and Cr4O132?species are formed. In summary,decreasing of the pH resulted in the formation of more polymerized chromium oxide species. At the pH of highest sorption ef?ciency(pH3.0),the dom-inant species were HCrO4?and Cr2O72?.Thus,HCrO4?and Cr2O72?are most easily exchanged with Cl?from the periph-eral–NH3+Cl?groups present in the polymer-grafted sawdust. Cr3O102?and Cr4O132?were also formed at highly acidic pH(<2.5)but were dif?cult to exchange with Cl?ions from the adsorbent surface with dif?culty.The adsorption capacities decreased with increase in temperature(Table7). Maple sawdust was also utilized for Cr(VI)remediation [101].Adsorption increased in the pH range of3.0–10.0.Sorp-tion was explained in terms of the pH zpc(zero point of charge) of the adsorbent.The pH zpc of sawdust was6.0.Surface charge of the adsorbent is positive at pH<6.0.At pH 780 D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811 is a H+–M n+exchange process.The possible sites on sawdust for speci?c adsorption include groups which are the source of H+ ions(···C6H5···OH and···COOH functional groups)where protons can be exchanged for cations: S···COOH+M n+→S···COOM(n?1)++H+(21) S···C6H5···OH+M n+→S···C6H5···OM(n?1)++H+ (22) S···COOH+M(OH)(n?1)+ →S···COOM(OH)(n?2)++H+ (23) S···C6H5–OH+M(OH)(n?1)+ →S···C6H5···OM(OH)(n?2)++H+(24) S denotes the surface.Adsorption is not exclusively due to the ···COOH and phenolic–OH groups.Other sites also contribute. In an acidic medium,sawdust’s amide group’s protonate,gen-erating net surface positive charge.Surface protons are also exchanged with positively charged sorbate species leading to metal ion coordination.A small increase in adsorption occurred at pH>pH zpc.The surface becomes negatively charged while the sorbate species are still positively charged.Thus,the elec-trostatic attraction between sorbate and adsorbent causes metal ion adsorption.At lower pH,the higher proton concentration competes with the M2+ions for adsorption sites.This reduces metal ion sorption.The decrease in adsorption at still higher pH was due to the formation of soluble hydroxyl complexes. Phosphate-treated and-untreated sawdust was exploited[98] for aqueous Cr(VI)removal.Almost100%Cr(VI)removal was achieved in the pH range<2.0for the initial Cr(VI)concentra-tion of8–50mg/L.Furthermore,100%removal of Cr(VI)from synthetic wastes as well as from electroplating waste containing 50mg/L Cr(VI)was achieved by both batch and column pro-cesses.The Cr(VI)adsorbed on phosphate-treated sawdust was recovered(87%)using0.01M sodium hydroxide. The iron(III)complex of a carboxylated polyacrylamide-grafted sawdust proved to be an effective adsorbent for the removal of aqueous Cr(VI)[99].Sawdust of rubber wood(Hevea brasiliensis)was grafted with polyacrylamide.About20.0g of dried sawdust(1)was treated with300mL of a solution containing5.0g of N,N -methylenebisacrylamide(2)and per-oxydisulfate(2.0g).Next,7.5g of acrylamide(3)was added, and the mixture was re?uxed at70?C.The polyacrylamide-grafted sawdust(PGSD)was washed with water and dried at 80?C.The desired carboxylate-functionalized polymer product was produced by re?uxing PGSD with ethylenediamine[(en)2] in toluene and then with succinic anhydride in1,4-dioxane at pH4.0After reaction,carboxylic-acid-bound PGSD(PGSD-COOH)was separated,washed with1,4-dioxane and ethanol and dried.PGSD-COOH was sieved to obtain?80to+230mesh size particles.The production of and structure of PGSD-COOH is represented in Fig.5. The carboxylate group loading in PGSD-COOH was 2.03mmol/g.Maximum Cr(VI)removal(>99.0%)by PGSD-COOH took place at an initial Cr(VI)concentration of25.0mg/L in the pH range2.0–3.0.Unsaturated coordination sites on the polymeric Fe(III)complex were the adsorption sites for Cr(VI)species(predominant species was HCrO4?).Adsorption isotherm data were interpreted by the Langmuir and Freundlich equations.Cr(VI)uptake increased from144.20mg/g at20?C to172.74mg/g at60?C.Kendu fruit gum dust(KGD)was also Fig.5.Preparation of carboxylated polyacrylamide-grafted sawdust and its iron(III)complex.Source:Unnithan and Anirudhan[99]with permission. D.Mohan,C.U.Pittman Jr./Journal of Hazardous Materials B137(2006)762–811781 tested for Cr(VI)removal from aqueous solutions[110].As expected,at low pH Cr(VI)adsorption was high.The presence of cyanide ion decreased the Cr(VI)adsorption ef?ciency of the KGD.Only～20%loss of ef?ciency occurred after six cycles. Thermogravimetric analysis of original KGD and the frust KGD with adsorbed Cr(VI)suggested the thermal stability of KGD increased due to metal ion adsorption. Coir pith solid waste was investigated for Co(II),Cr(III) and Ni(II)adsorption in both single and multicomponent sys-tems[103].The optimum pH value for maximum chromium removal was3.3.The Langmuir model?t the data better than Freundlich model.The maximum coir pith sorption capac-ity was11.56mg Cr/g.The amine-modi?ed polyacrylamide-grafted coconut coir pith carrying–NH3+Cl?functional groups at the chain end(PGCP–NH3+Cl?)was also examined for aque-ous batch Cr(VI)removal[104].Grafting polyacrylamide onto the coir pith improved this adsorbent’s thermal stability and enhanced the apparent activation energy for the thermal degra-dation of PGCP–NH3+Cl?.Adsorbent crystallinity and mor-phology were examined using XRD and SEM.The decrease in crystalline domains in PGCP–NH3+Cl?results in the loss of ten-sile strength of the grafted chain.This enhances the free mobility grafted chain.Maximum Cr(VI)adsorption(99.4%;12.43mg/g) was achieved at an initial concentration of25.0mg/L Cr(VI)at 30?C,pH3.0,and an adsorbent concentration of2.0g/L.The Cr(VI)sorption kinetics were described by a pseudo-second-order kinetic model.Quantitative removal of22.7mg/L Cr(VI) in50mL of electroplating industry wastewater by125mg of PGCP–NH3+Cl?was achieved at pH3.0. Polysaccharides bound to bacteria or in isolated form can bind heavy metals.Ocimum basilicum seeds,which swell upon wet-ting,could serve as natural immobilized source of agriculturally based polysaccharides[119].The seeds consist of an inner hard core and a pectinous?brillar outer layer.Pre-treating the seeds with acid,alkali,periodate or boiling in water altered the metal binding capacity.Of these various treatments,seeds boiled in water were superior in terms of mechanical stability and exhib-ited optimal Cr(VI)uptake kinetics.The maximum adsorption capacity at pH1.5as calculated from the Langmuir isotherm was205mg Cr/g dry seeds.Sorption was not affected by the presence of other metal ions such as Cd2+,Cu2+,Ca2+and Na+. Daneshvar et al.[120]reported the reduction of Cr(VI)to Cr(III) followed by Cr(III)adsorption.A high ef?ciency for reduction of Cr(VI)to Cr(III)took place at pH<1.0.Cr(VI)also adsorbed on soya cake at pH<1.0. Cr(VI)from synthetic and actual electroplating wastewaters was removed by Fe-modi?ed steam exploded wheat straw(Fe-SEWS)[105].Removal of Cr(VI)was higher at pH≤3.0.The removal was～96%.No attempts were made to explain the sorption mechanism.Wool,olive cake,sawdust,pine needles, almond shells,cactus leaves and charcoal were employed to remove Cr(VI)[100].The in?uence of pH,contact time,metal concentration,adsorbent nature and concentration on the selec-tivity and sensitivity of the removal process was investigated. Cr(VI)adsorbed as HCrO4?.No measurements were made to check if there was any reduction of Cr(VI)into Cr(III).Further, Cr(III)was not adsorbed at pH≤3.0because positive Cr(III)ions were repulsed by positively charged active centers on the adsorbents.Therefore,Cr(III)adsorption was carried out at pH 5.0.At this pH,the number of negatively charged groups on the adsorbent matrix increased and enhanced the Cr(III)removal by columbic attraction.Cr(III)adsorption capacities were not reported. Eromosele et al.[106]utilized shea butter(Butyrospermum parkii)seed husks for aqueous Cr(III)removal.The effects of agitation and counter-ions on the sorption process were inves-tigated.Sorption was enhanced by a factor of2by agitation but was independent of its speed.Addition of isopropanol to aqueous solutions of Cr(III)ions depressed Cr(III)adsorption. Carboxymethylation of the seed husk reduced its adsorptive capacity for Cr(III)ion by60%.Sharma and Forster[107]tried using leaf mould as biosorbent for the treatment of wastewaters contaminated with Cr(VI)in a column system.The results were compared with an activated carbon column.Both columns were operated at a pH of2.5and a?ow-rate of74mL/min.Cr(VI) adsorption capacities of the leaf mould were only26mg/g com-pared to76mg/g for the activated carbon.The leaf mould caused little or no reduction of Cr(VI)and produced an ef?uent with very low concentration of Cr(III).The activated carbon,on the other hand,reduced a lot of chromium. Dupont and Guillon[108]utilized a lignocellulosic substrate derived from the industrial treatment of wheat bran as an adsor-bent.The air-dried,coarsely powdered wheat bran(30g)was subjected to acid hydrolysis by2mol/L H2SO4(1:1(w/w)dry matter,at100?C for30min)to remove starch,proteins,and sugars.This was followed by alkali treatment with0.5mol/L NaOH(5:1ratio of bran/sodium hydroxide,stirring for24h at room temperature)to remove the low molecular weight lignin compounds after?ltration.The solid was stirred with0.04mol/L HNO3in order to protonate all acidic sites and then it was washed with deionized water until the pH reached a constant value close to neutrality.Adsorption consumed a large number of protons accompanying the reduction of Cr(VI)into Cr(III).Concur-rent oxidation of lignin moieties took place during chromium reduction.This led to the formation of hydroxyl and carboxyl functions.The latter contribute to an increase in the number of ion-exchange sites for the reduced chromium.The maxi-mum adsorption capacity for Cr(VI)was～35mg/g in an acidic medium. Trivalent chromium biosorption was investigated on cork powder[109].Chromium was reduced from10mg/dm to less than1.5mg/dm in2h at22?C using a solid–liquid ratio of 4g/dm.Fifty percent of the chromium bound to the cork was eluted using0.5mol/dm H2SO4and that cork maintained its binding capacity over four biosorption/elution cycles. 5.2.Zeolites Zeolites are crystalline,hydrated aluminosilicates of alkali and alkaline earth cations,having in?nite,three-dimensional structures[121,122].Zeolites have been received increasing attention for pollution control.There are more than30natural zeolites known.Only seven(mordenite,clinoptilolite,chabazite, erionite,ferrierite,phillipsite,and analcime)occur in suf?cient 入职资料登记表 申请职位：入职日期：年月日 基本资料 姓名性别民族出生年月 学历身份证号 联系电话身高体重政治面貌 是否有驾照及类型婚姻及生育状况 户口所在地现居住地 紧急联系人联系电话 电子邮箱社会统筹情况□养老□医疗□失业□生育□工伤□公积金 教育背景 起止时间毕业院校专业学历/学位教育性质 □统招□函授□自考□其他 □统招□函授□自考□其他职业资格证书或其他相关证书： 时间工作单位、职位离职原因工作 经历证明人姓名及联系方式 家庭关系姓名年龄工作单位职务联系方式主要 关系 招聘渠道：□网络招聘□员工推荐（员工姓名）□人才市场□其他方式其他是否有朋友、亲戚在我公司工作？□是，请说明：□否 其他说明事项： 公司承诺：此资料将进入公司人才库严格保密，并仅作招聘使用。为全面了解您的优劣势，安排合适的岗位 使您扬长避短，请您认真、完整、如实填写。 本人承诺：本人授权公司向本人曾任职的公司、介绍人或咨询人查询所有记录，且申明以下提交的一切资料 绝对真实，如有不实，可作为被公司辞退的理由，而公司无须做出任何赔偿。 填表人确认签名： 新员工录用工资确认表 姓名录用部门录用岗位入职时间年月日发放日期每月20 日，遇节假日顺延薪酬标准执行①试用期工资：元/ 月；转正后元/月。 第种； 本岗位工资按公司规定暂实行足额发放。②实行年薪制 ③其他 年薪元，试用期工资：元/ 月；转 正后元/月；余额根据公司内部规定发放。 ①社会保险 福 利 待 遇③其它补助自年月开始缴纳社会保险。（备注说明：） 补贴①： 试用期发元/月；转正后发元/ 月。 补贴②： 试用期发元/月；转正后发元/ 月。 以上信息由人力资源部填写，填写人签字确认： 确认日期：年月日人力资源部主管领导意见： 确认日期：年月日领导签批确认： 确认日期：年月日 以下信息由新入职员工填写 新入职员工身份证号码 银行卡号 开户行 以上薪资及福利内容本人已经知晓，身份证号码、银行卡号、开户行信息由本人自已填写，并确保 信息准确无误；因自已填写错误造成的损失由本人承担一切责任。同时本人承诺对自已的薪资福利绝 对保密，如自已泄露愿接受公司的一切处理，直至解除劳动合同给予辞退。 新入职员工确认签字：确认日期：年月日 本表一式一份，仅供人事部与新录用员工核对薪资福利信息用，在经领导核定并经新录用员工签字 备注说明 确认后作为发放工资的依据。领导核定签批后原件留存于财务部门，人力资源部留存复印件。 入职登记表 个人基本信息 姓名性别民族 相 片籍贯学历政治面貌 婚姻状况□已婚有子女□已婚无子女□未婚□其他 现住地址 身份证号 本人 联系电话 身份证住址 提交资料 (复印件) □身份证□学历证□其他 紧急联系人 紧急联系人（请填写常住地的亲友） 姓名关系工作单位和现住址紧急联系人电话 家 庭 成 员 姓名关系工作单位家人联系电话 健康信息利手：□左□右是否怀孕：□无□有 是否曾被认定工伤或持有残疾人证明：□无□有： 是否有重大疾病或家族病史：□无□有： 是否从事过特别繁重体力劳动及有毒有害工种：□无□有：是否有职业病或慢性影响工作的疾病：□无□有： 教 育 培 训 起止时间就读学校学历专业持有证书 工 作 经 历 起止时间工作单位职位离职原因证明人/电话 单位意见： 员工签名： 年月日 入职承诺书 本人 , 男/女，学历：，身份证号码： , 1.本人在填写本《入职登记表》时，已保证自己符合国家法定的劳动年龄的标准，且与其他任何用人单位、机构、 组织、团体无劳动关系；若违反前述承诺，导致用人单位被追究有关经济责任的，所有责任均由本人承担。 2.本人在填写《入职登记表》时，用人单位已如实告知工作内容、工作地点、工作条件、职业危害、安全生产状况、劳动报酬以及本人所需要了解的所有情况。 3.本人如有传染病、精神病或其他可能影响用人单位工作的病史，本人应以书面形式向用人单位说明。 4.本人承诺已与原单位解除劳动关系，且无仍然生效的保密协议、竞业限制协议。 5.本人填写的《入职登记表》所有信息真实有效，如有任何虚假，用人单位可按严重违反规章制度解除劳动合同， 同时承担因此引起的所有责任。 6.本人承诺对用人单位相关信息（包括但不限于工资）承担保密责任。 7.如《入职登记表》中的信息有变化，本人有责任以书面形式向用人单位人事部门提交最新的信息。 8.本人承诺在试用期满经考核合格后即与用人单位签订劳动合同，本人将认真阅读并遵守各项规章制度。 9.本人承诺在用人单位任职期间不从事任何兼职行为。 10.本人所填写的通讯方式（包括地址、手机）均为有效，用人单位向任一通讯方式寄送或发出的文件或物品，如 果发生收件人拒绝签收和已发送成功均视为送达。 11.本人承诺无被追究刑事责任记录，如有应以书面形式告知用人单位，如隐瞒事实真相，一切法律后果由本人承担。 12、本人承诺，遵守以下各项入职时的甲乙双方达成的约定：： ①新入职员工的试用期范围为一至三个月，用人单位将视试用期绩效考核确定转正期限。 ②员工在试用期需提前3日书面申请辞职，试用期满后离职必须提前一个月以书面形式向用人单位递交辞职申 请，待用人单位批准后按指定日期办理工作交接，双方确认无误后方可离职。 ③凡未经批准或未办理正式离职交接手续而自行离职的员工，均视为自动离职，用人单位有权停发其工作期间 的工资，作为离职后给公司带来损失的补偿。 ④自愿遵守公司规章制度，若在试用期3天内（含3天）不合适或自离的，不予工资结算。 本人已充分了解上述资料的真实性是双方订立劳动合同的前提条件，本人填写的以上任何信息虚假 新员工入职流程New employee orientation process 入职准备 1、人力中心向合格者发送《录用通知书》； 2、确认新员工报到日期,通知新员工在报到之前来公司明确报到需注意事项：所需资料、体检以 及其他须知； 3、通知人事助理新员工报到日期，人事助理准备好新员工入职手续办理所需表单并负责依据《新 员工入职通知单》内容落实各项工作： --用人部门负责安排办公位，申领电脑、电话； --行政办负责发放办公用品； --信息组负责开通邮箱、帐号、调试电脑设备等。 2入职报到 1、人力中心向新员工发放《新员工报到工作单》，并按要求办理入职手续： --员工填写《应聘登记表》，并交验各种证件： 一寸免冠照片3张； 身份证原件或户口复印件； 学历、学位证书原件（学生提供学生证原件）； 资历或资格证件原件； 与原单位解除或终止劳动合同的证明； 体检合格证明； --与员工签订劳动合同、保密协议、职位说明书； --建立员工档案、考勤卡； --介绍公司情况，引领新员工参观公司、介绍同事； --将新员工移交给用人部门； --OA网上发布加盟信息更新员工通讯录。 2、用人部门负责的工作 --负责安置座位，介绍并帮助熟悉工作环境； --制定专人作为新员工辅导员，介绍岗位职责和工作流程[1]。 3入职手续 1、填写《员工履历表》。 2、发放向新员工介绍公司情况及管理制度的《制度汇编》，使其具备基本公司工作知识，要求 其通过公司内部网络了解进一步情况。 3、按照《新员工入职手续清单》逐项办理入职手续。 4、确认该员工调入人事档案的时间。 5、向新员工介绍管理层。 6、带新员工到部门，介绍给部门总经理。 一、新员工入职办理流程 第1步：新员工报到，人事专员接待（谁招聘谁办理）。 第2步：人事专员先收集：员工应提供的资料，核对并复印。 第3步：人事专员提供我方应准备的资料：劳动合同、保密协议、告知函、人事制度等，给新员工学习，并讲解，时间控制在15分钟以内。 第4步：告知其薪酬为面试时的约定，一周内由财务来核定其薪酬如何切分。 第5步：员工签订相关资料后，用手机钉钉通知IT部，开通邮箱/钉钉等权限，开通后由IT部发到其钉钉上。 第6步：人事讲解公司基本考勤制度。 第7步：人事介绍公司/部门/岗位基本情况。 第8步：人事协助员工安装钉钉，并讲解基本的钉钉使用技能。 第9步：引领员工，认识主要部门负责人，并熟悉公司环境。 第10步：引导员工：到IT部领取电脑设备，到行政部领取办公用品。 第11步：引导员工到部门负责人处报到，并安排好办公桌。 第12步：邮箱发送新员工报道通告，员工档案转交。 第13步：员工入职报到流程结束。 二、员工基本档案资料 员工提供资料： 1.身份证原件、复印件，公司核对原件，留存复印件； 2.学历证书原件、复印件、学位证书原件、复印件（一般为最高学历），公司核对原件， 留存复印件； 3.专业技术职称证书原件、职业资格证书原件、上岗证书原件，公司核对原件，留存复 印件； 4.上家公司离职证明（原件）； 5.上家公司劳动合同，公司核对原件，留存复印件； 6.体检报告：最近三个月内、三甲医院体检证明原件； 7.银行卡复印件（标配光大银行卡，入职一个星期后收取）； 8.就业失业登记证（上海户籍员工）； 9.公积金账号； 人事专员准备资料： 10.个人简历； 11.员工求职/入职信息登记表； 12.面试评估表（给入职者看薪资）； 13.劳动合同（需签收）； 14.保密协议（需签收）； 15.用人单位基本信息告知函。 入职资料审核标准 一、审核原则： 1、完整性：所有资料务必全部准备齐全，否则不予办理正式入职手续。 2、真实性：所有资料务必全部真实，如若查出伪造证件，不予办理入职手续。 二、详细内容 1.照片 A、规格：一寸彩色照片； B、数量：4张； C、要求：务必在每张照片背后写上姓名，以方便查询； D、范围：往届、应届毕业生、实习生、兼职等均需提供。 2. 身份证 A、规格：原件核查，只收取复印件； B、数量：4份； C、要求：身份证正反面复印在一张A4纸上； D、范围：往届、应届毕业生、实习生、兼职等均需提供。 3. 毕业证、学位证 A、规格：原件核查，只收取复印件； B、数量：各1份； C、要求：分开复印，均复印在A4纸上； D、范围：往届、应届毕业生、兼职等均需提供，实习生暂不提供。 4. 体检报告 A、规格：原件核查，只收取复印件； B、数量：1份； C、要求：必查项目健康，无其它严重疾病。注意传染性疾病的核实； D、范围：往届、应届毕业生、兼职等均需提供，实习生暂不提供。 5、E-HR个人信息 A、规格：外网登陆门户主页https://www.wendangku.net/doc/5d13481395.html,.“XXX”部分， 选择、进入“人才库”，进行在线录入； B、数量：1次； C、要求：所填的信息必须真实、完整，打印后签字确认； D、范围：往届、应届毕业生、实习生、兼职等均需提供。 6、原单位离职证明 A、规格：原件核查，只收取复印件； B、数量：1份； C、要求：必须有离现在最近的工作单位人事或公司公章盖章； D、范围：往届毕业生需提供，其他不提供。 7、户口本复印件1份，用于办理社会保险（要求：户口本首页和个人信息页复印到一张A4纸上，其中户口本首页说明了您的户籍性质；亦可提交户籍证明或户籍卡复印件）。 A、规格：户口本复印件或户籍证明、户籍卡复印件； B、数量：1份； C、要求：如果是户口本复印件，户口本首页和个人信息页复印到一张A4纸上 （其中户口本首页说明了您的户籍性质）； 如果是户籍证明，需要有户档保管单位的签章； 如果是户籍卡，只需要复印件即可。 D、范围：往届、应届毕业生等均需提供，实习生、兼职暂不提供。 企业新员工入职流程及六大步骤 企业新员工入职流程主要共分为六大步骤： 一、入职准备； 二、入职报到； 三、入职手续； 四、入职培训； 五、转正评估； 六、入职结束。 入职准备 1、人力中心向合格者发送《录用通知书》 2、用人部门助理负责依据《新员工入职通知单》内容落实各项工作 --用人部门负责安排办公位，申领电脑、电话； --行政办负责发放办公用品； --信息组负责开通邮箱、帐号、调试电脑设备等。 入职报到 1、人力中心向新员工发放《新员工报到工作单》，并按要求办理入职手续：--员工填写《员工登记表》，并交验各种证件： 一寸免冠照片3张； 身份证原件或户口复印件； 学历、学位证明原件； 资历或资格证件原件； 与原单位解除或终止劳动合同的证明； 体检合格证明 --与员工签订劳动合同、保密协议、职位说明书 --建立员工档案、考勤卡、 --介绍公司情况，引领新员工参观公司、介绍同事 --将新员工移交给用人部门； --OA网上发布加盟信息更新员工通讯录 2、用人部门负责的工作 --负责安置座位，介绍并帮助熟悉工作环境； --制定专人作为新员工辅导员，介绍岗位职责和工作流程 入职手续 1、填写《员工履历表》。 2、发放向新员工介绍公司情况及管理制度的《制度汇编》，使其具备基本公司工作知识，要求其通过公司内部网络了解进一步情况。 3、按照《新员工入职手续清单》逐项办理入职手续。 4、确认该员工调入人事档案的时间。 5、向新员工介绍管理层。 6、带新员工到部门，介绍给部门总经理。 7、将新员工的情况通过E-mail和公司内部刊物向全公司公告。 8、更新员工通讯录。 9、签订《劳动合同》 入职培训 1、组织新员工培训。 2、不定期举行由公司管理层进行的企业发展历程、企业文化、各部门职能与关系等方面的培训。 转正评估 1、转正是对员工的一次工作评估的机会，也是公司优化人员的一个重要组 入职登记表 入职承诺书 本人 , 男/女，学历：，身份证号码： , 1.本人在填写本《入职登记表》时，已保证自己符合国家法定的劳动年龄的标准，且与其他任何用人单位、机构、 组织、团体无劳动关系；若违反前述承诺，导致用人单位被追究有关经济责任的，所有责任均由本人承担。 2.本人在填写《入职登记表》时，用人单位已如实告知工作内容、工作地点、工作条件、职业危害、安全生产状况、劳动报酬以及本人所需要了解的所有情况。 3.本人如有传染病、精神病或其他可能影响用人单位工作的病史，本人应以书面形式向用人单位说明。 4.本人承诺已与原单位解除劳动关系，且无仍然生效的保密协议、竞业限制协议。 5.本人填写的《入职登记表》所有信息真实有效，如有任何虚假，用人单位可按严重违反规章制度解除劳动合同， 同时承担因此引起的所有责任。 6.本人承诺对用人单位相关信息（包括但不限于工资）承担保密责任。 7.如《入职登记表》中的信息有变化，本人有责任以书面形式向用人单位人事部门提交最新的信息。 8.本人承诺在试用期满经考核合格后即与用人单位签订劳动合同，本人将认真阅读并遵守各项规章制度。 9.本人承诺在用人单位任职期间不从事任何兼职行为。 10.本人所填写的通讯方式（包括地址、手机）均为有效，用人单位向任一通讯方式寄送或发出的文件或物品，如 果发生收件人拒绝签收和已发送成功均视为送达。 11.本人承诺无被追究刑事责任记录，如有应以书面形式告知用人单位，如隐瞒事实真相，一切法律后果由本人承担。 12、本人承诺，遵守以下各项入职时的甲乙双方达成的约定：： ①新入职员工的试用期范围为一至三个月，用人单位将视试用期绩效考核确定转正期限。 ②员工在试用期需提前3日书面申请辞职，试用期满后离职必须提前一个月以书面形式向用人单位递交辞职申 请，待用人单位批准后按指定日期办理工作交接，双方确认无误后方可离职。 ③凡未经批准或未办理正式离职交接手续而自行离职的员工，均视为自动离职，用人单位有权停发其工作期间 的工资，作为离职后给公司带来损失的补偿。 ④自愿遵守公司规章制度，若在试用期3天内（含3天）不合适或自离的，不予工资结算。 本人已充分了解上述资料的真实性是双方订立劳动合同的前提条件，本人填写的以上任何信息虚假 或没有履行以上特别说明的义务，无论任何时候被发现，本人均同意被用人单位视为严重违反《劳动合 同法》的诚实信用原则以及用人单位的规章制度，用人单位可以解除劳动合同且不用支付经济补偿金。 入职承诺人签名：日期：年月日 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 新员工入职所需携带资料： 1、一寸白底彩色照片4张，电子版数码照公司留底。 2、相关学历证书及复印件。 3、户口本复印件（首页及本人页） 4、原单位的离职证明。 5、二代身份证复印件（正反面）。 6、北京农村商业银行的银行卡。 7、健康证明或体检报告（一年以内的） 出生日期 1/2 FOR-120,A 员工入厂规定须知 一、入厂前辨理手续应缴交1.有效身份证 2.毕业证 3.未(已)婚证 4.相片三张 5.健康证明 缺少上列任何一项证件，未能辨理入厂手续者以试工不合格处理。 二、入厂后发现上列证件有不符或作假情形，以自动离厂处理。 三、工作不满十五天辞工及被解雇者，公司不发给工资。 四、试工期为三个月，试用未能达要求无条件接受厂方处理。(新进厂的时间以整月计，只要破月都 计)，满三个月再考核与考试，合格通过以成绩评估调薪额度。 五、本公司免费提供住宿及伙食于正式员工，新进员工入厂未满一年离职(含辞工、开除)本公司将追 扣试用期间之住宿伙食费(伙食费3元宿舍管理费2元每日5元人民币)，以进厂日累计至试工合格日止。 六、住宿与伙食依本公司员工干部住宿福利制度执行。 七、文員及主管離職需提前30日，普通作業員需提前15日遞交辭職申請單。经核准后即日生效， 未满時間離職者依劳工法扣除30日工资。 八、工资发放依照本公司薪资结构制度执行。 九、确实遵守厂规，自愿接受工作调度与加班安排，如有违反，皆依厂规处理，绝无异议。 十、有下列严重情节者，视情节轻重予以罚款或开除处分。 a. 无故旷工半日或一个月内无故旷工三日以上者。 b. 无故抗令或侮辱压迫干部主管人员者。 c. 厂内禁烟区吸烟、饮酒闹事、赌博或有伤风化行为者。 d. 聚众或先动手打架、煽动教唆怠工、停工、罢工之行为者。 e. 毁损盗窃公司或他人财物，文件及造谣生事敲诈行为者。 f. 未经主管人员书面同意，操作非本人之机器或本人操作之机器供他人操作者。 以上各项本人全部已看阅仔细并完全了解无误. 保证书 本人诚蒙xxx录用，于任用期间，愿意保证任职一年以上并遵守上列规定裁决，若造成公司一切损失，本人愿负赔偿责任，绝无怨言与异议，特立此书。 此致年月日身份证号： 签章： 2/2 FOR-120,A员工入职资料表格汇总26387
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