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修饰Sorption

Review

Removal of heavy metal ions from wastewater by chemically

modi?ed plant wastes as adsorbents:A review

W.S.Wan Ngah *,M.A.K.M.Hana?ah

School of Chemical Sciences,Universiti Sains Malaysia,11800Penang,Malaysia Received 3April 2007;received in revised form 18June 2007;accepted 18June 2007

Available online 27July 2007

Abstract

The application of low-cost adsorbents obtained from plant wastes as a replacement for costly conventional methods of removing heavy metal ions from wastewater has been reviewed.It is well known that cellulosic waste materials can be obtained and employed as cheap adsorbents and their performance to remove heavy metal ions can be a?ected upon chemical treatment.In general,chemically modi?ed plant wastes exhibit higher adsorption capacities than unmodi?ed forms.Numerous chemicals have been used for modi?cations which include mineral and organic acids,bases,oxidizing agent,organic compounds,etc.In this review,an extensive list of plant wastes as adsorbents including rice husks,spent grain,sawdust,sugarcane bagasse,fruit wastes,weeds and others has been compiled.Some of the treated adsorbents show good adsorption capacities for Cd,Cu,Pb,Zn and Ni.ó2007Elsevier Ltd.All rights reserved.

Keywords:Adsorption;Plant wastes;Low-cost adsorbents;Heavy metals;Wastewater treatment

1.Introduction

Heavy metals have been excessively released into the environment due to rapid industrialization and have cre-ated a major global concern.Cadmium,zinc,copper,nickel,lead,mercury and chromium are often detected in industrial wastewaters,which originate from metal plating,mining activities,smelting,battery manufacture,tanneries,petroleum re?ning,paint manufacture,pesticides,pigment manufacture,printing and photographic industries,etc.,(Kadirvelu et al.,2001a;Williams et al.,1998).Unlike organic wastes,heavy metals are non-biodegradable and they can be accumulated in living tissues,causing various diseases and disorders;therefore they must be removed before discharge.Research interest into the production of cheaper adsorbents to replace costly wastewater treatment methods such as chemical precipitation,ion-exchange,elec-tro?otation,membrane separation,reverse osmosis,elec-trodialysis,solvent extraction,etc.(Namasivayam and

Ranganathan,1995)are attracting attention of scientists.Adsorption is one the physico-chemical treatment pro-cesses found to be e?ective in removing heavy metals from aqueous solutions.According to Bailey et al.(1999),an adsorbent can be considered as cheap or low-cost if it is abundant in nature,requires little processing and is a by-product of waste material from waste industry.Plant wastes are inexpensive as they have no or very low eco-nomic value.Most of the adsorption studies have been focused on untreated plant wastes such as papaya wood (Saeed et al.,2005),maize leaf (Babarinde et al.,2006),teak leaf powder (King et al.,2006),lalang (Imperata cylindrica )leaf powder (Hana?ah et al.,2007),rubber (Hevea brasili-ensis )leaf powder (Hana?ah et al.,2006b,c ),Coriandrum sativum (Karunasagar et al.,2005),peanut hull pellets (Johnson et al.,2002),sago waste (Quek et al.,1998),salt-bush (Atriplex canescens )leaves (Sawalha et al.,2007a,b ),tree fern (Ho and Wang,2004;Ho et al.,2004;Ho,2003),rice husk ash and neem bark (Bhattacharya et al.,2006),grape stalk wastes (Villaescusa et al.,2004),etc.Some of the advantages of using plant wastes for wastewa-ter treatment include simple technique,requires little pro-

Corresponding author.Tel.:+6046533888;fax:+6046574854.E-mail address:wsaime@usm.my (W.S.Wan Ngah).

Available online at https://www.sodocs.net/doc/358561633.html,

Bioresource Technology 99(2008)

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cessing,good adsorption capacity,selective adsorption of heavy metal ions,low cost,free availability and easy regen-eration.However,the application of untreated plant wastes as adsorbents can also bring several problems such as low adsorption capacity,high chemical oxygen demand(COD) and biological chemical demand(BOD)as well as total organic carbon(TOC)due to release of soluble organic compounds contained in the plant materials(Gaballah et al.,1997;Nakajima and Sakaguchi,1990).The increase of the COD,BOD and TOC can cause depletion of oxygen content in water and can threaten the aquatic life.There-fore,plant wastes need to be modi?ed or treated before being applied for the decontamination of heavy metals. In this review,an extensive list of adsorbents obtained from plant wastes has been compiled and their methods of mod-i?cation were discussed.A comparison of adsorption e?-ciency between chemically modi?ed and unmodi?ed adsorbents was also reported.

2.Chemically modi?ed plant wastes

Pretreatment of plant wastes can extract soluble organic compounds and enhance chelating e?ciency(Gaballah et al.,1997).Pretreatment methods using di?erent kinds of modifying agents such as base solutions(sodium hydroxide,calcium hydroxide,sodium carbonate)mineral and organic acid solutions(hydrochloric acid,nitric acid, sulfuric acid,tartaric acid,citric acid,thioglycollic acid), organic compounds(ethylenediamine,formaldehyde,epi-chlorohydrin,methanol),oxidizing agent(hydrogen perox-ide),dye(Reactive Orange13),etc.for the purpose of removing soluble organic compounds,eliminating colour-ation of the aqueous solutions and increasing e?ciency of metal adsorption have been performed by many research-ers(Hana?ah et al.,2006a;Reddy et al.,1997;Taty-Cos-todes et al.,2003;Gupta et al.,2003;Namasivayam and Kadirvelu,1997;Sˇc′iban et al.,2006a;Min et al.,2004; Kumar and Bandyopadhyay,2006;Baral et al.,2006;Acar and Eren,2006;Rehman et al.,2006;Abia et al.,2006; Shukla and Pai,2005a,Low et al.,1995;Azab and Peter-son,1989;Lazlo,1987;Wankasi et al.,2006).The types of chemicals used for modifying plant wastes and their maximum adsorption capacities are shown in Table1. 2.1.Rice husks/rice hulls

Rice husk consists of cellulose(32.24%),hemicellulose (21.34%),lignin(21.44%)and mineral ash(15.05%)(Rah-man et al.,1997)as well as high percentage of silica in its mineral ash,which is approximately96.34%(Rahman and Ismail,1993).Rice husk is insoluble in water,has good chemical stability,has high mechanical strength and pos-sesses a granular structure,making it a good adsorbent material for treating heavy metals from wastewater.The removal of heavy metals by rice husk has been extensively reviewed by Chuah et al.(2005).Among the heavy metal ions studied include Cd,Pb,Zn,Cu,Co,Ni and Au.Rice husk can be used to treat heavy metals in the form of either untreated or modi?ed using di?erent modi?cation methods.

Hydrochloric acid(Kumar and Bandyopadhyay, 2006),sodium hydroxide(Guo et al.,2003;Kumar and Bandyopadhyay,2006),sodium carbonate(Kumar and Bandyopadhyay,2006),epichlorohydrin(Kumar and Ban-dyopadhyay,2006),and tartaric acid(Wong et al.,2003a; Wong et al.,2003b)are commonly used in the chemical treatment of rice husk.Pretreatment of rice husks can remove lignin,hemicellulose,reduce cellulose crystallinity and increase the porosity or surface area.In general,chem-ically modi?ed or treated rice husk exhibited higher adsorption capacities on heavy metal ions than unmodi?ed rice husk.For example,Kumar and Bandyopadhyay (2006)reported that rice husk treated with sodium hydrox-ide,sodium carbonate and epichlorohydrin enhanced the adsorption capacity of cadmium.The base treatment using NaOH for instance appeared to remove base soluble mate-rials on the rice husk surface that might interfere with its adsorption property.Tarley et al.(2004)found that adsorption of Cd increase by almost double when rice husk was treated with NaOH.The reported adsorption capaci-ties of Cd were7and4mg gà1for NaOH treated and unmodi?ed rice husk,respectively.

Meanwhile,most of the acids used for treatment of plant wastes were in dilute form such as sulfuric acid, hydrochloric acid and nitric acid.According to Esteghla-lian et al.(1997),dilute acid pretreatment using sulfuric acid can achieve high reaction rates and improve cellulose hydrolysis.Concentrated acids are powerful agents for cel-lulose hydrolysis but they are toxic,corrosive and must be recovered(Sivers and Zacchi,1995).However,in some cases,hydrochloric acid treated rice husk showed lower adsorption capacity of cadmium than the untreated rice husk(Kumar and Bandyopadhyay,2006).When rice husk is treated with hydrochloric acid,adsorption sites on the surface of rice husk will be protonated,leaving the heavy metal ions in the aqueous phase rather than being adsorbed on the adsorbent surface.Wong et al.(2003a)carried out an adsorption study of copper and lead on modi?ed rice husk by various kinds of carboxylic acids(citric acid,sali-cylic acid,tartaric acid,oxalic acid,mandelic acid,malic and nitrilotriacetic acid)and it was reported that the high-est adsorption capacity was achieved by tartaric acid mod-i?ed rice husk.Esteri?ed tartaric acid modi?ed rice husk however signi?cantly reduced the uptake of Cu and Pb. The maximum adsorption capacities for Pb and Cu were reported as108and29mg gà1,respectively.E?ect of che-lators on the uptake of Pb by tartaric acid modi?ed rice husk was also studied.It was reported that higher molar ratios of chelators such as nitrilotriacetic acid(NTA)and ethylenediamine tetraacetic acid(EDTA)caused signi?cant suppressing e?ect on the uptake of Pb.Dyestu?treated rice hulls using Procion red and Procion yellow for the removal of Cr(VI),Ni(II),Cu(II),Zn(II),Cd(II),Hg(II)and Pb(II) were studied by Suemitsu et al.(1986).More than80%of

3936W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–39483937 Table1

Summary of modi?ed plant wastes as adsorbents for the removal of heavy metal ions from aqueous solution

Adsorbent Modifying agent(s)Heavy metal Q max(mg gà1)Source

Rice husk Water washed Cd(II)8.58Kumar and Bandyopadhyay(2006) Sodium hydroxide20.24

Sodium bicarbonate16.18

Epichlorohydrin11.12

Rice husk Tartaric acid Cu(II)31.85Wong et al.(2003b)

Pb(II)120.48

Sawdust(cedrus deodar wood)Sodium hydroxide Cd(II)73.62Memon et al.(2007)

Sawdust(S.robusta)Formaldehyde Cr(VI) 3.6Baral et al.(2006)

Sawdust(Poplar tree)Sulfuric acid Cu(II)13.95Acar and Eren(2006)

Sawdust(Dalbergia sissoo)Sodium hydroxide Ni(II)10.47Rehman et al.(2006)

Sawdust(Poplar tree)Sodium hydroxide Cu(II) 6.92Sˇc′iban et al.(2006a)

Zn(II)15.8

Sawdust(Fir tree)Cu(II)12.7

Zn(II)13.4

Sawdust(Oak tree)Hydrochloric acid Cu(II) 3.60Argun et al.(2007)

Ni(II) 3.37

Cr(VI) 1.74

Sawdust(Pinus sylvestris)Formaldehyde in Sulfuric acid Pb(II)9.78Taty-Costodes et al.(2003)

Cd(II)9.29

Walnut sawdust Formaldehyde in sulfuric acid Cd(II) 4.51Bulut and Tez(2003)

Ni(II) 6.43

Pb(II) 4.48

Sawdust Reactive Orange13Cu(II)8.07Shukla and Pai(2005b)

Ni(II)9.87

Zn(II)17.09

Peanut husk Sulfuric acid Pb(II)29.14Li et al.(2006a)

Cr(III)7.67

Cu(II)10.15

Cr(VI)11.4Dubey and Gopal(2006) Groundnut husk Sulfuric acid followed by silver

impregnation

Cassava waste Thioglycollic acid Cd(II)NA Abia et al.(2006)

Cassava tuber bark waste Thioglycollic acid Cd(II)26.3Horsfall Jr.et al.(2006)

Cu(II)90.9

Zn(II)83.3

Wheat bran Sulfuric acid Cu(II)51.5O¨zer et al.(2004)

Wheat bran Sulfuric acid Cd(II)101O¨zer and Pirinc?c?i(2006)

Juniper?bre Sodium hydroxide Cd(II)29.54Min et al.(2004)

Indian barks Hydrochloric acid Cu(II)Reddy et al.(1997)

–sal51.4

–mango42.6

–jackfruit17.4

Jute?bres Reactive Orange13Cu(II)8.40Shukla and Pai(2005a)

Ni(II) 5.26

Zn(II) 5.95

Hydrogen peroxide Cu(II)7.73

Ni(II) 5.57

Zn(II)8.02

Unmodi?ed Cu(II) 4.23

Ni(II) 3.37

Zn(II) 3.55

Banana pith Nitric acid Cu(II)13.46Low et al.(1995)

Banana stem Formaldehyde Pb(II)91.74Noeline et al.(2005)

Spent grain Hydrochloric acid Cd(II)17.3Low et al.(2000)

Sodium hydroxide Pb(II)35.5

(continued on next page)

Cd(II),Pb(II)and Hg(II)ions were able to be removed by the two types of treated adsorbents,while Cr(VI)recorded the lowest percentage removal(<40%).

2.2.Spent grain

Spent grain obtained from brewery can be used to treat Pb(II)and Cd(II)ions as demonstrated by Low et al.,2000.Treatment of spent grain with NaOH greatly enhanced adsorption of Cd(II)and Pb(II)ions,whereas HCl treated spent grain showed lower adsorption than the untreated spent grain.The increase in adsorption of heavy metal ions after base treatment could be explained by the increase in the amount of galactouronic acid groups after hydrolysis of O-methyl ester groups.The best pH range for metal adsorption was4–6.Kinetic study reveals that the equilib-

Table1(continued)

Adsorbent Modifying agent(s)Heavy metal Q max(mg gà1)Source

Cork powder Calcium chloride Cu(II)15.6Chubar et al.(2004)

Sodium chloride19.5

Sodium hydroxide18.8

Sodium hypochlorite18.0

Sodium iodate19.0

Corncorb Nitric acid Cd(II)19.3Leyva-Ramos et al.(2005)

Citric acid55.2

Imperata cylindrica leaf powder Sodium hydroxide Pb(II)13.50Hana?ah et al.(2006a) Alfalfa biomass Sodium hydroxide Pb(II)89.2Tiemann et al.(2002)

Azolla?liculoides (aquatic fern)Hydrogen peroxide–Magnesium

chloride

Pb(II)228Ganji et al.(2005)

Cd(II)86

Cu(II)62

Zn(II)48

Carrot residues Hydrochloric acid Cr(III)45.09Nasernejad et al.(2005)

Cu(II)32.74

Zn(II)29.61

Sugarcane bagasse Sodium bicarbonate Cu(II)114Junior et al.(2006)

Pb(II)196

Cd(II)189

Ethylenediamine Cu(II)139

Pb(II)164

Cd(II)189

Triethylenetetramine Cu(II)133

Pb(II)313

Cd(II)313

Sugarbeet pulp Hydrochloric acid Cu(II)0.15Pehlivan et al.(2006)

Zn(II)0.18

Bagasse?y ash Hydrogen peroxide Pb(II) 2.50Gupta and Ali(2004)

Cr(III) 4.35

Nipah palm shoot biomass Mercaptoacetic acid Pb(II)52.86Wankasi et al.(2006)

Cu(II)66.71

Groundnut shells Reactive Orange13Cu(II)7.60Shukla and Pai(2005b)

Ni(II)7.49

Zn(II)9.57

Terminalia arjuna nuts ZnCl2Cr(VI)28.43Mohanty et al.(2005)

Coirpith ZnCl2Cr(VI)NA Namasivayam and Sangeetha(2006)

Ni(II)

Hg(II)

Cd(II)Kula et al.(2007)

Sulfuric acid and ammonium persulphate Hg(II)154Namasivayam and Kadirvelu(1999) Cu(II)39.7Namasivayam and Kadirvelu(1997) Hg(II)NA Kadirvelu et al.(2001a)

Pb(II)

Cd(II)

Ni(II)

Cu(II)

Ni(II)62.5Kadirvelu et al.(2001b)

NA–not available.

3938W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

rium time of adsorption was120min for both metal ions and adsorption followed pseudo-second-order model.The maximum adsorption capacity for lead was two times higher than cadmium.The e?ect of organic ligands (EDTA,nitrilotriacetic acid and salicylic acid)on adsorp-tion e?ciency was assessed and adsorption was greatly reduced by EDTA and nitrilotriacetic acid at molar ratio of1:1(metal:ligand).EDTA and nitrilotriacetic acid could chelate the heavy metal ions,therefore more metal ions would remain in the solutions rather than being adsorbed (Jeon and Park,2005).Salicylic acid on the other hand slightly reduced the percentage of cadmium adsorption but did not a?ect adsorption of lead.

2.3.Sugarcane bagasse/?y ash

Junior et al.(2006)reported the use of succinic anhy-dride modi?ed sugarcane bagasse for treatment of Cu, Cd and Pb from aqueous solutions.Sugarcane bagasse consists of cellulose(50%),polyoses(27%)and lignin (23%).The presence of these three biological polymers causes sugarcane bagasse rich in hydroxyl and phenolic groups and these groups can be modi?ed chemically to pro-duce adsorbent materials with new properties.The authors reported that the hydroxyl groups in sugarcane bagasse could be converted to carboxylic groups by using succinic anhydride.The carboxylic groups were later reacted with three di?erent chemicals mainly NaHCO3,ethylenediamine and triethylenetetramine to produce new properties of adsorbent materials which showed di?erent adsorption capacities for metal ions.It was found that sugarcane bagasse treated with ethylenediamine and triethylenetetra-mine shows a remarkable increase in nitrogen content com-pared to untreated sample,and triethylenetetramine modi?ed sugarcane bagasse has a higher increasing extent. The presence of amide group was also detected in ethylene-diamine and triethylenetetramine modi?ed sugarcane bag-asses as a result of the reaction between–COOH and–NH2groups.Kinetic studies showed that equilibrium time for adsorption of Cu,Cd and Pb onto tethylenediamine and triethylenetetramine modi?ed sugarcane bagasses were slower than that for adsorbent modi?ed with NaHCO3. Triethylenetetramine modi?ed sugarcane bagasse was the best adsorbent material for removal of Cd and Pb since the adsorption capacities for both metals are two times higher than unmodi?ed sugarcane bagasse.This was prob-ably caused by the higher number of nucleophilic sites introduced in triethylenetetramine modi?ed sugarcane bagasse.When sugarcane bagasse was modi?ed with meth-anol,however,the resulting adsorbent did not show a good uptake of cadmium as the maximum adsorption capacity was6.79mg gà1(Ibrahim et al.,2006).

The performance of hydrogen peroxide treated bagasse ?y ash,a solid waste of sugar industry for removal of lead and chromium was explored by Gupta and Ali(2004). Hydrogen peroxide is a good oxidizing agent and used to remove the adhering organic matter on the adsorbent.It was found that hydrogen peroxide treated bagasse?y ash was able to remove chromium in a shorter period of time (60min)compared to lead(80min).The isotherm study also revealed maximum adsorption capacity for chromium was higher than lead.However,the recorded values of maximum adsorption capacities for both metals were low (2.50and4.35mg gà1for Pb and Cr,respectively).The detail mechanism of adsorption by the treated bagasse?y ash was not discussed,but it was thought that adsorption was controlled by?lm di?usion at lower metal concentra-tion and particle di?usion at higher concentration of metal ions.

2.4.Sawdust

Sawdust,obtained from wood industry is an abundant by-product which is easily available in the countryside at negligible price.It contains various organic compounds (lignin,cellulose and hemicellulose)with polyphenolic groups that could bind heavy metal ions through di?erent mechanisms.An experiment on the e?ciency of sawdust in the removal of Cu2+and Zn2+ions was conducted by Sˇc′i-ban et al.(2006a).Two kinds of sawdust,poplar and?r wood were treated with NaOH(?bre-swelling agent)and Na2CO3solutions and the adsorption capacities were com-pared with the untreated sawdusts.For unmodi?ed saw-dust,both types of woods showed higher uptakes of Cu2+ions than Zn2+ions,and adsorption followed Lang-muir isotherm model.Equivalent amounts of adsorption capacities were recorded by both types of sawdust for Zn2+and Cu2+ions,although these two adsorbents have di?erent anatomical structure and chemical composition. After treating with NaOH,a marked increase in adsorption capacity was observed for both heavy metal ions,especially for Zn2+ions(2.5times for Cu2+and15times for Zn2+). The adsorption capacities shown by Langmuir model were 6.92mg gà1(poplar sawdust)and12.70mg gà1(?r saw-dust)for Cu2+,and15.83mg gà1(poplar sawdust)and 13.41mg gà1for Zn2+(?r sawdust),respectively.In another experiment,Sˇc′iban et al.(2006b)found that the leaching of coloured organic matters during the adsorption can be eliminated by pretreatments with formaldehyde in acidic medium,with sodium hydroxide solution after form-aldehyde treatment,or with sodium hydroxide only. According to Sˇc′iban et al.(2006a),NaOH improved the adsorption process by causing the liberation of new adsorption sites on the sawdust surface.An increase in the concentration of NaOH for modi?cation purpose how-ever did not cause a signi?cant increase of the adsorption capacity.The authors suggest that no greater than1%of concentration of NaOH solution should be used for mod-i?cation.The temperature of modi?cation was also not a signi?cant factor for the main increase of adsorption capacities of modi?ed sawdusts.It was observed that only a slight increase in Cu2+and Zn2+adsorption occurred when the?r sawdust was treated with NaOH at higher tem-perature(80°C).The study on adsorption capacity by

W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–39483939

treatment with Na2CO3revealed the modi?ed sawdusts had two times higher adsorption for Cu2+ions and six times higher for Zn2+ions compared to unmodi?ed saw-dusts.The application of Na2CO3for chemical modi?ca-tion is less e?cient than the use of NaOH.This is due to higher number of Na+ions in1g of NaOH compared to 1g of Na2CO3.In general,three possible reasons for the increase in adsorption capacities of heavy metal ions were given by the authors:

(i)Changes on wood surface-increase in surface area,

average pore volume and pore diameter after alkaline treatment.The surface area and average pore diame-ter increased about1.5–2times after modi?cation. (ii)Improvement in ion-exchange process especially with Na+ions.

(iii)Microprecipitation of metal hydroxides–Cu(OH)2 and Zn(OH)2in the pores of sawdust.

Although the work on adsorption of copper and zinc ions onto sawdust of poplar tree was reported by Sˇc′iban et al.(2006a),they did not carry out a detail experiment on the kinetic of adsorption.

The e?ect of sulfuric acid treatment on sawdust of pop-lar tree was studied by Acar and Eren(2006).Sulfuric acid poplar sawdust possessed good removal of92.4%Cu2+at pH5,while untreated sawdust could only removed47%. The kinetic of copper binding indicated that it is a rapid process and about70–80%of copper ions removed from the solution in10min.The percent of copper removal how-ever decreases as the metal concentration increases.The increase in percent of adsorption with adsorbent dose could be due to the increase in surface area and availability of more active sites.The treated poplar sawdust showed maximum adsorption capacity of13.945mg gà1against 5.432mg gà1for untreated sawdust which followed Lang-muir isotherm model.The maximum adsorption capacity for sulfuric acid treated poplar sawdust is higher than to the value recorded by NaOH treated poplar sawdust reported by Sˇc′iban et al.(2006a).Concentrated sulfuric acid was also used to modify coconut tree sawdust for removing mercury and nickel(Kadirvelu et al.,2003).It was reported that100%removal of mercury was achieved compared to81%for nickel and adsorption occurred in 1h.

Rehman et al.(2006)reported the removal of Ni2+ions by using sodium hydroxide treated sawdust of Dalbergia sissoo,a byproduct of sawmills.The treatment of sawdust with NaOH results in the conversion of methyl esters which are the major constituents in cellulose,hemicellulose and lignin to carboxylate ligands.The adsorption time study revealed that nickel ions were removed fast in the?rst 20min due to extra-cellular binding.The maximum adsorp-tion capacity of Ni2+ions was found to be10.47mg gà1at 50°C.Adsorption was more favourable at higher tempera-ture and adsorption followed both Langmuir and Freund-lich isotherm models.

A comparative study on the adsorption e?ciency of untreated and NaOH treated sawdust of cedrus deodar wood was conducted by Memon et al.(2007).They reported that cedrus deodar sawdust mainly consists of acid detergent?bre(cellulose and lignin),hydroxyl groups (tannins)and phenolic compounds.The acidimetric–alkali-metric titration study revealed that sawdust has four major groups responsible for cadmium binding which were car-boxylic,phosphoric,amines and phenolic.Cadmium removal was more favoured by NaOH treated sawdust as the value of adsorption capacity was four times greater than untreated sawdust.Maximum removal of cadmium occurred at pH above4for both types of adsorbents.When the pH of the solution is greater than4,carboxylic groups will be deprotonated and the adsorbent surface will be neg-atively charged resulting in higher adsorption of cadmium. However;at pH less than3,carboxylic groups become pro-tonated and adsorption sites are unable to attract Cd2+ ions.NaOH treated sawdust also shows good settling prop-erty,making it easy to?lter or separate the adsorbent from the solution.Ion-exchange was considered as the predom-inant mechanism of cadmium adsorption as the values of adsorption energy(E)determined from Dubinin–Radushk-evic plots are in the range of9–16kJ molà1.Maximum adsorption capacity recorded at temperature of20°C was

73.62mg gà1.

A detail analysis on the ideal concentration of NaOH for modifying juniper?bre for adsorption of cadmium ions was carried out by Min et al.(2004).Sodium hydroxide treatment of lignocellulosic materials can cause swelling which leads to an increase in internal surface area,a decrease in the degree of polymerization,a decrease in crys-tallinity,separation of structural linkages between lignin and carbohydrates and disruption of the lignin structure. Sodium hydroxide is a good reagent for saponi?cation or the conversion of an ester group to carboxylate and alco-hol,as shown in the equation below:

RCOOR0tH2O!

OHàRCOOàtR0OHe1T

Based on the FTIR analysis,it was found that as the con-centration of NaOH increases(from0to 1.0M),the amount of carboxylate was also increased.A maximum concentration of0.5M of NaOH was suitable to carry out saponi?cation process.After base treatment,the max-imum adsorption capacity of cadmium increased by about three times(from9.18to29.54mg gà1)compared to un-treated juniper?bre despite a decrease in speci?c surface area for the treated adsorbent.Data obtained from pseu-do-second-order kinetic study also revealed that base trea-ted juniper?bre had higher values of adsorption capacity, q e(mg gà1)and initial adsorption rate constant,h (mg gà1minà1)when compared to untreated adsorbent.

Hexavalent chromium adsorption by formaldehyde treated sawdust was studied by Baral et al.,2006.Formal-dehyde is a common compound used to immobilize colour and water soluble compounds from sawdust(Garg et al.,

3940W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

2004).The adsorption capacity of Cr(VI)determined from Langmuir isotherm was low(3.60mg gà1)and equilibrium adsorption time took about5h.Adsorption process was strongly a?ected by several physico-chemical parameters such as pH,adsorbent dose,temperature and initial con-centration of chromium solution.Maximum adsorption occurred at pH range3–6and reduced signi?cantly beyond pH6.The percentage adsorption of Cr(VI)increased with increase in adsorbent dose,but decreased with increase in metal concentration and temperature.Adsorption rate tends to increase with increase in adsorbent dose due to higher number of available adsorption sites.As concentra-tion of Cr(VI)increases with?xed amount of adsorbent dose,more Cr(VI)ions will remain in the aqueous phase, thus percentage adsorption will be small.The decrease in adsorption rate with increase in temperature indicates exo-thermic nature of adsorption,in which adsorption is more favourable at lower temperatures.

According to Taty-Costodes et al.(2003),treatment with formaldehyde induces a stabilization of the hydrosol-uble compounds of adsorbent by creating covalent bonds on the constitutive units.This could eliminate the problem associated with the release of polyphenolic compounds which could cause an increase in COD in wastewater.A research on the adsorption of Pb(II)and Cd(II)onto form-aldehyde treated sawdust of Pinus sylvestris shows that the two metal ions were successfully removed in less than 20min at low concentrations(<10mg là1).It was reported that metal ions could form complexes with the oxygen atom on carbonyl and hydroxyl groups(acting as a Lewis base).The maximum adsorption capacities of Pb(II)and Cd(II)were9.78and9.29mg gà1,respectively.Adsorption kinetic indicates that pseudo-second-order model was bet-ter?tted than pseudo-?rst-order and intraparticle di?usion is one of the rate determining steps.Nickel,cadmium and lead adsorption by walnut sawdust treated with formalde-hyde in sulfuric acid was studied and it was found that adsorption is dependent on contact time,metal concentra-tion and temperature(Bulut and Tez,2003).Equilibrium time was established in about60min for all heavy metals. The kinetic study reveals that adsorption followed pseudo-second-order model better than pseudo-?rst-order.The maximum adsorption capacities were 6.43, 4.51and 4.48mg gà1for Ni,Cd and Pb,respectively.Based on tem-perature study,adsorption was favaourable at higher tem-peratures as the values of D G°become more negative.

Chubar et al.(2004)studied the performance of various kinds of chemically treated cork powder obtained from cork oak tree for the removal of Cu,Zn and Ni.Treatment of cork powder with salts such as NaCl and CaCl2causes the conversion of active binding sites from the H+form to Na+and Ca2+form.The salt modi?ed cork powder shows greater adsorption capacity than the unmodi?ed cork especially at higher heavy metal concentrations.It was also noted that the Na+form cork recorded a higher adsorption capacity value than the Ca2+form.This obser-vation can be explained in terms of the di?erent charge of cations whereby the interaction of cork powder binding sites with divalent calcium ions is stronger than the mono-valent sodium ions.Hence,the biosorption reaction of cop-per will be hindered.Treatment of cork powder with an alkaline solution(NaOH)at high temperature increased the sorption capacity toward heavy metals by about33%.

A high concentration of NaOH however causes a decrease in copper removal due to the destruction of the biomass. Besides NaCl,CaCl2and NaOH,modi?cation of cork powder could be carried out using commercial laundry detergent and the amount of copper removed was found to increase,probably due to the exposure of new binding sites.The use of NaClO and NaIO3will increase the num-ber of active binding sites by oxidation of the some of func-tional groups of cork to carboxylic groups,hence more copper ions could be sorbed.An increase of70–80%in cork capacity for copper was achieved after treating cork powder with NaClO containing7%of active chlorine. 2.5.Wheat bran

Wheat bran,a by-product of wheat milling industries proved to be a good adsorbent for removal of many types of heavy metal ions such as Pb(II),Cu(II)and Cd(II).The application of a strong dehydrating agent like sulfuric acid (H2SO4)can have a signi?cant e?ect on the surface area of the adsorbent,which eventually results in better e?ciency of adsorption of copper ions as reported by O¨zer et al. (2004).It was found that upon treatment with sulfuric acid, wheat bran had a much higher surface area.The authors suggested that acid treatment caused changes in surface area by increasing the conversion of macropores to microp-ores.Maximum adsorption capacity for Cu(II)ions was reported as51.5mg gà1(at pH5)and equilibrium time of adsorption was achieved in30min.O¨zer and Pirinc?c?i (2006)conducted a study on the removal of lead ions by sulfuric acid treated wheat bran.It was reported that max-imum lead removal(82.8%)occurred at pH6after2h of contact time.Three isotherm models were analyzed for determining the maximum adsorption capacity of wheat bran particularly Langmuir,Freundlich and Redlich-Peter-son.Based on the non-linear plots,it was found that adsorption?tted well to the Redlich-Peterson than Lang-muir and Freundlich models.The Langmuir plots indicate that maximum adsorption capacities increased with an increase in temperature(79.37mg gà1at60°C and 55.56mg gà1at25°C).The decrease in the values of D G°suggests that adsorption was more favourable at higher temperatures and adsorption was endothermic in nature. The kinetic study showed that lead adsorption could be described well with n th-order kinetic model.O¨zer(2006) also examined the sulfuric acid treated wheat bran for cad-mium ion removal from aqueous solution.After4h of con-tact time,the maximum adsorption capacity that could be achieved for cadmium was101mg gà1at pH5.Therefore, in general the order of maximum removal of the above three metals follows:Cd(II)>Pb(II)>Cu(II).

W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–39483941

2.6.Corncobs

Besides carbonization at high temperature,an adsorbent can be activated by chemical treatment using a concen-trated acid.This method was demonstrated by Khan and Wahab(2006)in the study of adsorption of copper by con-centrated sulfuric acid treated corncobs.It was reported that upon treatment of corncobs with sulfuric acid and heated at150°C,the pH zpc of the adsorbent reduced from 5.2(untreated)to2.7(treated),and the functional groups present in the adsorbent are mainly oxygen containing groups such as–OH,–COOH and–COOà.The maximum adsorption capacity obtained from Langmuir isotherm was 31.45mg gà1.Adsorption was more favoured at higher pH value(4.5)due to low competing e?ect of protons for the adsorption sites.E?ect of interfering ions such as Zn(II), Pb(II)and Ca(II)was also studied.It was noticed that cop-per removal e?ciency was reduced by53%,27%and19% in the presence of Pb(II),Ca(II)and Zn(II),respectively. Regeneration study indicates that sulfuric acid treated corncobs can be regenerated by acidi?ed hydrogen perox-ide solution and as much as90%copper could be recovered.

The study on oxidation of corncob by citric acid and nitric acid was carried out by Leyva-Ramos et al.(2005). Upon oxidation of corncob,a signi?cant increase in the surface area of the adsorbent was observed.An increase in the amount of oxygen found in corncob was due to more oxygenated groups being introduced on the adsorbent sur-face after oxidation.After oxidation,a higher proportion of acidic sites(carboxylic,phenolic and lactonic)was detected,which results in a reduction in the pH ZPC value. It was also reported that the adsorption capacities for citric acid and nitric acid oxidized corncob were much higher than unmodi?ed corncob.

2.7.Weeds

The study on e?ectiveness of lead adsorption by sodium hydroxide treated lalang(one of the ten worst weed of the world)or Imperata cylindrica leaf powder was carried out by Hana?ah et al.(2006a).Maximum adsorption of lead occurred at pH range4–5and an adsorbent dose of 4g là1.Temperature study indicates that chemisorption was the main rate limiting step and pseudo-second-order kinetic model was?tted well.The value of maximum adsorption capacity obtained by NaOH treated Imperata cylindrica(13.50mg gà1)is much higher than untreated adsorbent(5.89mg gà1)(Hana?ah et al.,2007).A faster equilibrium time(20min)was observed for treated Imper-ata cylindrica compared to untreated(120min).The e?ect of metal concentration and thermodynamics on the sorp-tion of Pb(II)and Cd(II)ions by nitric acid treated wild cocoyam(Caladium bicolor)biomass was investigated by Horsfall and Spi?(2005).The biomass was?rst reacted with nitric acid before washed with distilled water,then suspended in hydroxylamine to remove all O-acetyl groups.It was noticed that the amount of Pb(II)sorbed was higher than Cd(II)ions.The smaller ionic radii of Cd(II)(0.97A?) compared to Pb(II)(1.20A?)means greater tendency of Cd(II)to be hydrolyzed,leading to reduced sorption.Sorp-tion capacity increased with increasing metal concentra-tions for both cations.The maximum sorption capacities were49.53and48.20mM gà1for Pb(II)and Cd(II), respectively.Freundlich and Langmuir models were found to be?tted well.The sorption was reported to occur by ion-exchange mechanism involving hydroxyl groups as repre-sented by the following equation:

M2tt2BOH$MeBOT

t2Hte2TSpontaneous sorption of Pb(II)and Cd(II)was noticed as the negative values of D G°were obtained in all concentra-tions studied.

2.8.Fruit/vegetable wastes

Adsorption of divalent heavy metal ions particularly Cu2+,Zn2+,Co2+,Ni2+and Pb2+onto acid and alkali trea-ted banana and orange peels was performed by Annadurai et al.(2002).The acid and alkali solutions used for modi?-cation of adsorbents were HNO3and NaOH.In general, the adsorption capacity decreases in the order of Pb2+>Ni2+>Zn2+>Cu2+>Co2+for both adsorbents. Banana peel exhibits higher maximum adsorption capacity for heavy metals compared to orange peel.The reported maximum adsorption capacities were7.97(Pb2+), 6.88 (Ni2+),5.80(Zn2+),4.75(Cu2+)and2.55mg gà1(Co2+) using banana peel;and were7.75(Pb2+), 6.01(Ni2+), 5.25(Zn2+), 3.65(Cu2+)and 1.82mg gà1(Co2+)using orange peel.Acid treated peels showed better adsorption capacities followed by alkali and water treated peels.Based on regeneration studies,it was reported that the peels could be used for two regenerations for removal and recovery of heavy metal ions.

Besides NaOH,Ca(OH)2is another good saponifying agent for the conversion of ester groups to carboxyl groups as demonstrated by Dhakal et al.(2005).In the study, orange waste(consists of cellulose,hemicellulose,pectin, limonene and other low molecular weight compounds) was treated with Ca(OH)2to form saponi?ed gel(SOW). Two forms of saponi?ed gels were prepared(Ca2+-form and H+-form)and their removal e?ciency for six heavy metal ions particularly Fe(III),Pb(II),Cu(II),Zn(II), Cd(II)and Mn(II)were compared.The authors suggested that cation exchange was the main mechanism for the removal of heavy metal ions as the pH of solutions decreased after adsorption.The order of removal for Ca2+-form SOW gel was Pb(II)>Fe(III)>Cu(II)>Cd-(II)>Zn(II)>Mn(II).In the case of H+-form SOW gel, the order of removal was Pb(II)>Fe(III)>Cu(II)> Zn(II)>Cd(II)>Mn(II).As the pH of solutions increases, the percent removal of heavy metal ions also increased except Fe(III).The percent removal of Fe(III)greatly reduced beyond pH3due to formation of soluble iron

3942W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

complexes such as Fe(OH)+,FeeOHTt

2,FeeOHT4t

and

FeeOHTà

4.The authors also suggested that ion-exchange

mechanism involves oxygen atom in the pyranose ring of pectin acids cooperating with carboxylic group to form a stable?ve-membered chelate ring.This study indicates that both types of SOW gels are e?ective for removing heavy metal ions in acidic solution.

Chemical modi?cation of cornelian cherry,apricot stone and almond shell by using concentrated sulfuric acid for the removal of Cr(VI)has been studied(Demirbas et al., 2004).All the three types of fruit wastes showed highest removal of Cr(VI)at pH 1.It was also reported that adsorption was highly dependent on the initial metal con-centration as the lowest concentration recorded fastest removal rate(shortest equilibrium time).The equilibrium time for cornelian cherry was20h at53mg là1Cr(VI)con-centration,increased to70h as the concentration increased to203mg là1.The removal rate increased with a decrease in adsorbent size,which indicates that smaller particle size has larger surface area.Four di?erent kinetic models par-ticularly pseudo-?rst-order,pseudo-second-order,Elovich and intraparticle di?usion were evaluated and results showed that pseudo-second-order model correlated well with the experimental data.Recently,Kula et al.(2007) reported the application of ZnCl2(a dehydrating agent) in the activation of olive stone for removal of Cd(II)ions. It was reported that treated olive stone shows a remarkable increase in surface area compared to untreated olive stone. However,the activated olive stone did not show good adsorption capacity for Cd(II)as the reported maximum adsorption capacity was only1.85mg gà1.

Li et al.(2006b)investigated orange peels as an adsor-bent for cadmium adsorption and the e?ect of di?erent cit-ric acid concentrations on the adsorbent characters was studied.Upon treatment with more concentrated citric acid solutions,orange peels showed lower values of pH of zero point charge(pH zpc)due to the increase number of total acidic sites while the total number of basic sites decreased. The increase in citric acid concentration results in more oxygenated groups being introduced to the adsorbent sur-face.Orange peels washed with0.6M citric acid at80°C has a much lower pH ZPC value indicating that the adsor-bent surface becomes more negative due to dissociation of weakly acidic oxygen-containing groups.Chemical treatment with citric acid at high temperature produced condensation product and citric acid anhydride.The reac-tive citric acid anhydride can react with cellulosic hydroxyl groups to form an ester linkage and introduce carboxyl groups to the cellulose(Marshall et al.,1999).The presence of more carboxyl groups will increase more cadmium ions to bind on the adsorbent surface.It was also reported that cadmium adsorption occurred via ion-exchange mecha-nism as the pH of the solution decreases after adsorption, which indicates the presence of more protons in the e?u-ents.Desorption experiment revealed that Cd(II)ions could be removed when the concentration of hydrochloric acid was increased and maximum percentage recovery of cadmium was94%with0.15M HCl solution.The reported value of maximum adsorption capacity was101.16mg gà1. The untreated orange waste however could only adsorb 0.43mmol gà1or48.33mg gà1Cd(Pe′rez-Mar?′n et al., 2007).Previously,Wartelle and Marshall(2000)reported an interesting?nding in which a linear relationship between total negative charge and amount of copper ions adsorbed was observed for12types of agricultural by-products(sugarcane bagasse,peanut shells,macadamia nut hulls,rice hulls,cottonseed hulls,corn cob,soybean hulls,almond shells,almond hulls,pecan shells,English walnut shells and black walnut shells)after modi?cation with citric acid.It was found that after washing with base (NaOH)and modi?ed with citric acid,the total negative charge of all12types of agricultural by-products increased signi?cantly.Among the12adsorbents,soybean hulls(a low density material)showed the highest copper uptake and had a high total negative charge value,which can be explained by the increase in carboxyl groups after thermo-chemical reaction with citric acid.On the other hand,nut-shells(high density materials)such as English walnut shells and black walnut shells displayed low total negative charge values indicating low number of carboxyl groups.Due to the high bulk density,the lignin in nutshells may block or allowed little penetration of citric acid to reactive sites, hence lower copper ion uptake was observed.Wafwoyo et al.(1999)also reported that citric acid treated peanut shells showed higher removal of Cu,Cd,Ni,Zn and Pb ions compared to untreated shells.The metal uptake gets even larger when the shells were treated?rst with NaOH followed by citric acid.Treatment with NaOH will de-esterify and removes tannins,leaving more active binding sites available for metal adsorption.

Heavy metals such as Cr(III),Cu(II)and Zn(II)were able to be removed from wastewater using HCl treated car-rot residues.Acid treatment was performed in order to remove tannins,resins,reducing sugars and coloured mate-rials.According to Nasernejad et al.(2005),adsorption of metal ions onto carrot residues was possible due to the presence of carboxylic and phenolic groups which have cat-ion exchange properties.Based on kinetic study,more than 70%metal ions were removed in the?rst10min and equi-librium was achieved in70min.More metals were adsorbed at higher pH values of the solutions(pH4for Cr(III)and pH5for Cu(II)and Zn(II)).Maximum adsorp-tion capacities were45.09,32.74and29.61mg gà1for Cr(III),Cu(II)and Zn(II),respectively.

2.9.Cassava waste

Chemically modi?ed adsorbent could also be prepared by thiolation(a process of introducing–SH group) method.Abia et al.(2003)carried out an experiment of determining the optimal concentration of thioglycollic acid (HSCH2COOH)for the removal of Cd(II),Cu(II)and Zn(II)ions by cassava waste.Cassava waste consists of ligands such as hydroxyl,sulfur,cyano and amino which

W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–39483943

could bind heavy metal ions.It was noticed that adsorptiv-ity of the cassava waste was greatly improved as the con-centration of modifying agent(thioglycollic acid)was increased from0.5to1.0M due to the increase in sulfhy-dryl groups,–SH.Adsorption was reported to take place on the cell wall of the biomass.Optimum adsorptions of all three heavy metals were achieved in less than30min. The order of maximum adsorption capacity among the three heavy metal ions after treating cassava waste with 1.0M thioglycollic acid follows:Zn(II)>Cu(II)>Cd(II). The authors however did not conduct a detail experiment on the kinetic model of adsorption.

E?ect of concentration of modifying agent on the adsorption of Cd(II)and Zn(II)ions onto thioglycollic acid treated cassava waste was investigated by Horsfall and Abia(2003).Cassava waste treated with1.0M thioglycollic acid showed highest removal of Cd(II)and Zn(II)ions compared to0.5M and untreated adsorbent but the time to reach equilibrium remained similar for treated and untreated adsorbent.It was observed that treated cassava waste had a much higher adsorption capacity for Cd(II) and Zn(II)ions compared to untreated sample.The adsorption capacities were reported as86.68mg gà1Cd, 55.82mg gà1Zn and647.48mg gà1,559.74mg gà1for untreated and treated cassava waste,respectively.The increase in adsorption capacity of Cd and Zn after acid treatment could be associated with the formation of micro-porosity,which leads to enhanced thiol(–SH)groups on the adsorbent surface.The relative ease of exchanging hydrogen atoms of the thiol groups with heavy metal ions results in improved level of adsorption.Desorption studies revealed that untreated cassava waste showed better recov-ery of Cd(II)and Zn(II).The authors suggest that the low recovery of heavy metal ions by acid treated cassava waste was due to enhancement in binding sites after acid treat-ment,which enables the metal ions to bind strongly to the adsorbent surface.Abia et al.(2006)explored di?erent kinetic models to account for the transport of Cd(II)from aqueous solution on to the surface of0.5and 1.0M thiolated cassava wastes.Six kinetic models were tested mainly pseudo-?rst-order,pseudo-second-order,intrapar-ticle di?usion,Elovich,mass transfer and intraparticle di?usivity models.Results indicate that adsorption fol-lowed pseudo-second-order better than the other kinetic models.

2.10.Plant?bres

Two types of chemical modi?cations on jute?bres and their e?ectiveness in the removal of Cu(II),Zn(II)and Ni(II)ions were reported by Shukla and Pai(2005a).The ?rst modi?cation involved a monochloro triazine type reactive dye,Reactive Orange13,which was covalently loaded to the cellulosic matrix of jute?bres.Another mod-i?cation involved oxidation of hydroxyl groups of cellulose present in jute?bres to carboxyl group(a weak cationic ion-exchanger)by using hydrogen peroxide.In the case of dye loaded jute?bres,the dye contains an azo linkage and hydroxyl groups(–OH),a situation favourable for for-mation of six membered ring chelate with metal ions.The presence of sodium sulphonate groups of the dye molecules attached covalently to the adsorbent also enhanced the metal adsorption capacity.The mechanism of ion-exchange between Na+of the dyed material and the heavy metal ions can be represented by the following equation:

ReSO3NaT

tM2t!ReSO3TMt2Nate3TFor oxidized jute,the high uptake of heavy metal ions was due to the generation of carboxyl groups(–COOH).The authors reported that oxidation process of jute?bres was carried out under alkaline condition,therefore the carboxyl groups are in the form of carboxylate.The adsorption of heavy metal ions could also take place by ion-exchange mechanism as shown below:

2RCOONatM2t!eRCOOT

Mt2Nate4TBased on the Langmuir plots,maximum adsorption capac-ity for Cu(II)ion was achieved by dye loaded jute,followed by oxidized jute and unmodi?ed jute.However,for Ni(II) and Zn(II)ions,maximum adsorption capacities were re-corded by oxidized jute and the lowest was by unmodi?ed jute.

Chemical modi?cation of cellulose?bre to improve its removal performance and adsorption capacity for Cu(II), Ni(II)and Zn(II)ions using ethylenediamine was con-ducted by Torres et al.(2006).Cellulose consists of active hydroxyl groups present on each monomeric unit of cellu-lose,therefore cellulose can react with carboxyl and amine groups of organic compounds.Based on the isotherm study,it was found that ethylenediamine modi?ed cellulose ?bre adsorbed Zn(II)more e?ciently than Ni(II)and Cu(II)ions.The reported values of maximum adsorption capacities were104.1,308.2and69.3mg gà1for Cu,Ni and Zn,respectively.The modi?ed adsorbent was also capable to adsorb metals100times more than unmodi?ed cellulose(Okieimen et al.,2005).Adsorption of heavy metal ions occurred through complexation mechanism in which the amine(–NH2)groups of ethylenediamine take part in the chelation process.

It is well known that adsorption of heavy metals by cellulosic wastes depends on the contact time and temper-ature.Ho and Ofamaja(2006)found that initial concentra-tion of Cu(II)has great e?ect on the equilibrium time for copper adsorption onto HCl treated palm kernel?bre. The time to reach equilibrium was only15min for 50mg là1copper,but increased to60min for200mg là1. The study reveals that copper adsorption increases with the increase of temperature which indicates that the mobil-ity of Cu(II)ions increases with a rise in temperature.The value of activation energy of22kJ molà1suggests that chemisorption was an important process in the adsorption of copper onto HCl treated palm kernel?bre.Adsorption follows pseudo-second-order kinetic model at all copper concentrations studied.

3944W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

2.11.Tree barks

Three di?erent kinds of tree barks mainly sal(Shorea robusta),mango(Mangifera indica)and jackfruit(Artocar-pus integri?oria)were modi?ed using hydrochloric acid solution in order to remove copper from aqueous solutions (Reddy et al.,1997).Treated barks were able to chelate more copper ions than untreated ones.Extraction of solu-ble organic compounds which coloured the decontami-nated solutions was also avoided after pretreatment process.The highest adsorption capacity of copper ions was shown by sal bark(51.4mg gà1),followed by mango (42.6mg gà1)and jackfruit(17.4mg gà1).Binding of cop-per to the bark occurred through cation exchange mecha-nism as the pH of the e?uent decreased after copper adsorption.It was reported that hydroxyl and carboxyl groups were involved in the adsorption process and the results indicate that chelation of1mol of copper generates about1.6–1.8mols of hydronium ions.Regeneration of adsorbent was more successful using higher concentration of HCl solution.

2.12.Azolla(water fern)

Azolla,a small aquatic fern is commonly used as fertil-izer in botanical gardens and as green manure in rice?elds. Binding or ion-exchange of heavy metal ions is possible due to the presence of charged groups such as carboxyl and phosphate in the Azolla matrix(Ganji et al.,2005).The percentage adsorption values of Pb,Cd,Cu and Zn by Azolla treated with MgCl2alone were approximately33, 29,40and24,respectively.These values however increased with increasing concentration of MgCl2due to better ion-exchange behaviour between heavy metals and Mg2+ions on the cell walls of Azolla.No remarkable e?ect on the heavy metal removal was observed when Azolla was trea-ted with H2O2alone.However,the highest metal removal was reported by treating Azolla with2M MgCl2in the presence of8mM H2O2.It was thought that upon treat-ment with H2O2,more hydroxyl groups can be oxidized to carboxyl groups(Robert and Barbati,2002),which later binds with Mg2+ions.The(RCOO)2Mg can act as a good ion-exchange group,hence more heavy metal ions could be exchanged/removed from wastewater.The maximum adsorption capacities for Pb(II),Cd(II),Cu(II)and Zn(II) were228,86,62and48mg gà1,respectively.Heavy metals could be desorbed from Azolla using HCl solution and the order of desorption follows:Zn(II)>Cu(II)>Cd(II)> Pb(II).

2.1

3.Alfalfa biomass

Tiemann et al.(2002)investigated the adsorption of lead ions by alfalfa(Medicago sativa)biomass.The biomass was modi?ed with a combination of methanol/concentrated HCl solution in order to esterify the carboxyl groups.Bind-ing of lead(II)ions on the biomass was not observed after esteri?cation,but adsorption capacity increased to 43mg gà1for unmodi?ed alfalfa and89.2mg gà1for hydrolyzed alfalfa by NaOH.This?ndings indicate that carboxyl groups played a major role for the binding of lea-d(II)ions from solution by alfalfa biomass.The adsorption mechanism for Pb(II)on alfalfa biomass was established using X-ray absorption near edge structure(XANES)spec-troscopy and extended X-ray absorption?ne structure (EXAFS)spectroscopy.The EXAFS data demonstrated that Pb(II)ions formed monodentate complex with oxygen atoms via carboxyl groups and the Pb-O bond distance was 2.60A?

2.14.Coirpith carbon

The combined application of concentrated sulfuric acid and ammonium persulphate for activation of coirpith for removal of mercury,copper and nickel was carried out by Namasivayam and Kadirvelu(1999);Namasivayam and Kadirvelu(1997);Kadirvelu et al.(2001b).The adsorption equilibrium time for all heavy metal ions stud-ied was less than60min and the order of maximum adsorption capacity follows:Hg(II)>Ni(II)>Cu(II). Treatment of coirpith with sulfuric acid and ammonium persulphate introduced more functional groups on the car-bon surface and the mechanism of adsorption involves ion-exchange between heavy metal ions and Na+/H+ions as shown below(Namasivayam and Kadirvelu,1997):

2C x OHttM2t!eC x OT

M2tt2Hte5T

C x OHt

tM2t!C x OM2tt2Hte6T

2C x ONattM2t!eC x OT

M2tt2Nate7T

C x ONat

tM2t!C x OM2tt2Nate8T

2C x SO3HtM2t!eC x SO3T

Mt2Hte9T

2C x SO3NatM2t!eC x SO3T

Mt2Nate10T

In another study,chemical activation of coirpith could also be carried out using ZnCl2for removing Cr(VI),Ni(II)and Hg(II)from wastewater(Namasivayam and Sangeetha, 2006).Coirpith activated with ZnCl2was found to have a much higher surface area compared to the coirpith pre-pared in the absence of ZnCl2.Hence,more heavy metal ions were able to be removed from the wastewater.

2.15.Cottonseed hulls and soybean hulls

Marshall and Johns(1996)studied the removal of Zn(II) ions by treating soybean hulls and cottonseed hulls with 0.1M NaOH and0.1M HCl solutions.The results obtained from acid and base treatments were compared with water washed adsorbents.For soybean hulls,a26% increase in adsorption capacity was observed after NaOH treatment compared with water washing.However,the capacity was greatly reduced(about78%)after washing

W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–39483945

the adsorbent with HCl.For cottonseed hulls,zinc adsorp-tion was also increased by79%after washing the adsorbent with NaOH,but reduced by89%after acid treatment.The authors reported that both adsorbents contain pectin sub-stances consisting primarily of galacturonic acid and O-methyl esters.Upon treatment with NaOH,the O-methyl esters are converted to methanol and additional galact-uronic acid.The adsorbent surfaces will have more nega-tive charge sites or greater number of metal adsorption sites,hence greater metal adsorption capacity.Acid-washed hulls however will cause the adsorbent surface to be protonated,causing Zn(II)ions more di?cult to be adsorbed(Kumar and Bandyopadhyay,2006).

3.Conclusion

This review shows that the study on chemically modi?ed plant wastes for heavy metal removal has attracted the attention of more scientists.A wide range of low-cost adsorbents obtained from chemically modi?ed plant wastes has been studied and most studies were focused on the removal of heavy metal ions such as Cd,Cu,Pb,Zn,Ni and Cr(VI)ions.The most common chemicals used for treatment of plant wastes are acids and bases.Chemically modi?ed plant wastes vary greatly in their ability to adsorb heavy metal ions from solution.Chemical modi?cation in general improved the adsorption capacity of adsorbents probably due to higher number of active binding sites after modi?cation,better ion-exchange properties and formation of new functional groups that favours metal uptake. Although chemically modi?ed plant wastes can enhance the adsorption of heavy metal ions,the cost of chemicals used and methods of modi?cation also have to be taken into consideration in order to produce‘low-cost’adsor-bents.Since modi?cation of adsorbent surface might change the properties of adsorbent,it is recommended that for any work on chemically modi?ed plant wastes,charac-terization studies involving surface area,pore size,poros-ity,pH ZPC,etc.should be carried out.Spectroscopic analyses involving Fourier transform infrared(FTIR), energy dispersive spectroscopy(EDS),X-ray absorption near edge structure(XANES)spectroscopy and extended X-ray absorption?ne structure(EXAFS)spectroscopy are also important in order to have a better understanding on the mechanism of metal adsorption on modi?ed plant wastes.

Acknowledgements

The authors wish to thank Universiti Sains Malaysia for ?nancial support(Grant No.:304/PKIMIA/638056)of this review.One of us(Megat Ahmad Kamal Megat Hana?ah) gratefully acknowledges?nancial support from the Malay-sian Public Service Department and Universiti Teknologi MARA.References

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3948W.S.Wan Ngah,M.A.K.M.Hana?ah/Bioresource Technology99(2008)3935–3948

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就可以一条条的打印了。 6、更快速的方法：点击“合并到新文档”，就会将所有的数据按一条数据一页文档的方法新建一个文档（即：“字母1”文档），或是点“合并到打印机”，就会全部打印出来了。 b、套印已有表格的空栏处。（如：学籍卡、义务卡等）首先、用扫描仪把表格扫描成图片文件，插入到文件，调整纸张大小与表格文件的原始尺寸一致，然后右击该图片并选择“设置图片格式”，在弹出的对话框中选择“版式”标签，然后选择“衬于文字下方”，调整图片使其正好覆盖整个页面。接着、在需要打印的空栏处插入文本框，调整其大小正好和表格图片的空栏尺寸一致。设置文本框为“无填充颜色”和“无线条颜色”。最后、按“a”的方法进行操作。篇二：用word排版来制作快递模板下面告诉(word套用图片模板)大家一种简单方便的方法：用word排版来制作快递模板（我是用的中通的）工具：1、针式打印机一台， 2、扫描仪一台（非必备，因为需要将快递单扫描到电脑中去。如果你没有，那么把快递单拿到其他有扫描仪的地方扫描一下，然后把文件复制到自己的电脑中去也行。） 3、小尺一个，用来量快递单的尺寸。步骤：1.用尺子

完整word版,个人储蓄业务操作指南

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4.23 版本：深圳市亚美达通讯设备有限公司目录 5 .......................................................................................................................... 1、系统登录6、主界面 ............................................................................................................................. 2 .............................................................................................................................. 62.1标题栏 .............................................................................................................................. 62.2菜单栏 .............................................................................................................................. 62.3工具栏 .............................................................................................................................. 6状态栏

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1目的指导文件编写者能够高效的编写出符合文件编写标准程序的文件来。 2范围此文件适合所有编写标准操作流程的文件编写人员。

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采用分餐进食，避免人员密集。餐厅每日消毒1次，餐桌椅使用后进行消毒。餐具用品须高温消毒。操作间保持清洁干燥，严禁生食和熟食用品混用，避免肉类生食。建议营养配餐，清淡适口。 6．下班路上如何做洗手后佩戴一次性医用口罩外出，回到家中摘掉口罩后首先洗手消毒。手机和钥匙使用消毒湿巾或75%酒精擦拭。居室保持通风和卫生清洁，避免多人聚会。 7．公务采购如何做须佩戴口罩出行，避开密集人群。与人接触保持1米以上距离，避免在公共场所长时间停留。 8．工间运动如何做建议适当、适度活动，保证身体状况良好。避免过度、过量运动，造成身体免疫能力下降。 9．公共区域如何做每日须对门厅、楼道、会议室、电梯、楼梯、卫生间等公共部位进行消毒，尽量使用喷雾消毒。每个区域使用的保洁用具要分开，避免混用。传递纸质文件前后均需洗手，传阅文件时佩戴口罩。 10．公务出行如何做专车内部及门把手建议每日用75%酒精擦拭1次。乘坐班车须佩戴口罩，建议班车在使用后用75%酒精对车内及门把手擦拭消毒。

简易常用-Word文档使用技巧方法大全(超全)

Word文档使用技巧方法大全 Word2000、2003、2007、2010快捷键使用大全总结常用快捷键快捷键作用一、字体类 Ctrl+B 使字符变为粗体 Ctrl+I 使字符变为斜体 Ctrl+U 为字符添加下划线 Ctrl+Shift+D 双下划线 Ctrl+Shift+< 缩小字号 Ctrl+Shift+> 增大字号

Ctrl+] 逐磅增大字号 Ctrl+[ 逐磅减小字号 Ctrl+Shift+F 改变字体 Ctrl+Shift+P 改变字号 Ctrl+D 改变字符格式（"格式"菜单中的"字体"命令） Shift+F3 切换字母大小写(一次首字母变成大写，两次单词变成大写) CTRL+SHIFT+A 将所选字母设为大写二、格式类 Ctrl+Shift+C 复制格式 Ctrl+Shift+V 粘贴格式 Ctrl+1 单倍行距（1为主键盘的数字键） Ctrl+2 双倍行距

Ctrl+5 1.5 倍行距 Ctrl+0 在段前添加一行间距 Shift+F1（单击）需查看文字格式了解其格式的文字Ctrl+E 段落居中 Ctrl+J 两端对齐 Ctrl+L 左对齐 Ctrl+R 右对齐 Ctrl+Shift+J 分散对齐 Ctrl+M 左侧段落缩进 Ctrl+Shift+M 取消左侧段落缩进 Ctrl+T 创建悬挂缩进 Ctrl+Shift+T 减小悬挂缩进量

Ctrl+Shift+S 应用样式 Ctrl+Shift+N 应用"正文"样式 Alt+Ctrl+1 应用"标题1"样式 Alt+Ctrl+2 应用"标题2"样式 Alt+Ctrl+3 应用"标题3"样式三、编辑和文字移动 Backspace 删除左侧的一个字符 Ctrl+Backspace 删除左侧的一个单词 Delete 删除右侧的一个字符 Ctrl+Delete 删除右侧的一个单词 F2（然后移动插入移动选取的文字或图形点并按Enter键）

完整word版用户操作手册模板

项目名称用户操作手册部门：项目：密级：日期：编写说明类别：项目文档

密级：撰稿人：修改人：存放位置：编辑软件：版本信息：版本修改点说明页1目录．目录 1 引言 .................................................................. ..................................................................... 1-1 1.1 编写目的................................................................................................................... 1-1 项目背景................................................................................................................... 1-1 1.2 术语定义................................................................................................................... 1-1 1.3 参考资料................................................................................................................... 1-1 1.4 软件概述 .2 ..................................................................... ......................................................... 2-3 2.1 目标........................................................................................................................... 2-3 功能.2.2 .......................................................................................................................... 2-3 性能 2.3 ........................................................................................................................... 2-3 3 运行环

2017年操作手册模板word版本

<项目名称> 操作手册年月日

修改记录

目录 1简介 (1) 1.1手册目的 (1) 1.2手册范围 (1) 1.3名词定义 (2) 1.4参考文件 (2) 2系统简述 (2) 3公共操作 (2) 3.1开关机 (2) 3.2注册 (2) 3.3主菜单操作 (3) 3.4退出 (3) 3.5屏幕画面的布局 (3) 3.6公共画面属性 (4) 3.7提示窗 (4) 3.8按钮定义 (5) 3.9键盘定义 (6) 4功能概述 (7) 5功能模块1 (7) 5.1子功能模块1 (8) 5.2子功能模块2 (8) 6功能2 (8) 7功能3 (8) 8附件 (8)

1简介本章将简要地说明软件操作手册(以下简称本手册)的目的、范围、名词定义和参考文件。 1.1 手册目的本手册的目的在于告诉XXXXXX系统(以下简称本系统)的使用者，本系统提供了哪些功能，以及如何正确地、有效地来使用这些功能。 1.2 手册范围本手册首先简要地介绍本系统结构以及软件环境，然后说明本系统为使用者提供的各项功能及其详细的操作步骤。关于系统详细软硬件结构、系统安装及系统运行维护方面的内容，请参考本系统的《系统安装手册》及《系统运行维护手册》。本手册的使用者包括：这里罗列手册的使用者。例如: 营业人员帐务人员网点操作员 … … … 本手册各章节内容安排如下：第一章简介: 简单说明本手册的目的、范围、名词定义和参考文件。第二章系统概述: 简单说明本系统的结构及其执行环境。第三章公共操作: 介绍系统注册与退出、关机等公共操作，并指明为系统中各项操作所共有的屏幕属性、按钮定义及键盘定义。第四章功能概述第五章操作说明: 逐一说明各项功能及其详细的操作步骤。其中“第四章功能概述”与“第五章操作说明”为本手册之重点，希望使用者能深入了解。 1 /9

快速套用IEEE Word模板方法

快速套用IEEE Word模板方法及注意事项（仅供参考）所谓套用IEEE Word模板，就是将自己论文的内容逐步替换模板中的相应内容（千万不要整体复制）具体方法与注意事项如下： 1、在屏幕上同时打开IEEE模版文档和自己已定稿论文的Word文档； 2、将IEEE模版文档中全部文字的字体改为红色字体（自己的论文还是黑色字体）； 3、标题与正文应分开替换，正文也应该逐段逐段替换以替换题目为例：将自己论文的题目复制到模版中题目的尾部（即，前面红色字体为模板中的题目，后面黑色字体为自己论文的题目），选择模板中题目的部分红色文字，使用工具栏中的格式刷，将复制过来的题目（黑色字体）刷红（目的是使题目字体与大小跟模板的一致），同时，再将其改为黑色字体，最后再删除前面的红色文字即可（文章标题为3号字加粗，实词首字母大写，其余小写）； 4、继续采用上述替换方法，依次替换其他内容； 5、注意事项：（1）引言中的第一个单词分两次替换，先替换首字母，再替换该单词的其他字母，在删除红色字体时使用Backspace 键删除比较保险；（2）一、二级标题不能与正文一起套用，套用后注意及时修改字号一级标题的每个实词的首字母是10号字体，其他字母是8号二级标题每个单词的首字母大写，其余小写，字号均为斜体10号；（3）首页左下角的作者信息需要单独替换，其中要注意人名的简写方式，例：Xiaoming Wang，简写为X Wang；（4）替换图片下方的文字说明时注意，格式为Fig+点+空格+点+两个空格+图片文字说明（首字母大写）；（5）替换表格上方的文字时注意，表的标题TABLE为大写8号字，后加空格加罗马数字，换行输入表的标题，标题全部大写，其中每个实词的首字母8号，其余字母6号；表头为实词首字母大写；（6）公式编号所在行应先选择右端对齐，然后在公式编号前加空格，直至公式“居中”；（7）引用文献编号时注意，参考文献按顺序引用，不用上标表示；引用的参考文献如果是第2和第3篇，表示为[2]，[3]；如果是第1到第3篇，则表示为[1]-[3]；（8）替换参考文献时，请按照下面的格式修改：首先非英文文献需要译成相应的英文后著录；人名按西文习惯，名前姓后，名只用首字母加点，姓用全称；列出全部作者，超过六位后用,et al. ①在线专著：作者.（出版年，月日）.书名（版本）[Online]. Available: 网址： ②在线期刊：作者.（出版年，月）.文章名.期刊名（期刊名为斜体，实词首字母大写）.[Online].卷(期).页码范围. Available: 网址： ③专著析出文献：作者,“文章名”（文章名加双引号，正体，实词首字母大写）, in 专著名（专著名为斜体，实字首字母大写）,版本.卷,编者.出版地:出版商,年份, pp.页码范围. ④专著：作者, 书名（书名为斜体，实词首字母大写）.出版地: 出版商,年份, pp.页码范围. ⑤期刊论文：作者,“文章名”（文章名加双引号，正体，实词首字母大写）,期刊名（期刊名为斜体，实词首字母大写）,卷,期,pp.引用页码,月份.年份. ⑥会议论文：作者, “文章名”（文章名加双引号，正体，实词首字母大写），in 会议名称（会议名称斜体，实词首字母大写）,举办地,年份,pp.引用页码. ⑦专利文献：作者, “专利名”（专利名加双引号，正体，实词首字母大写）,国家Patent 专利号, 月日, 年份. ⑧标准文献：标准名（标准名斜体，实词首字母大写），标准号, 年份. （9）文中需要强调的内容，使用斜体即可，不能采用其它方式（加粗或加下划线等）标注；（10）科技英语专家发现作者信息（首页左下角）的表述不统一，现规范如下，请作者对照修改：关于作者信息的规范文章标题下面按照名前姓后的顺序给出所有作者的全名，并以逗号间隔开，若有两个或以上的作者，在最后一个作者名前加and；若作者是IEEE会员，也请注明；举例如下： Yiyi Wang, Sansan Li and Wuliu Zhao, IEEE Member 请在第一页的左下角注明文章的资助项目和编号，然后给出作者信息，包括姓名（姓全拼，名只需首字母）、从小到大顺序的作者单位（到二级单位）、邮箱，通讯作者还需要注明联系电话，举例如下： This work was supported by the National Natural Science Foundation of China under Grant No. 60128008. Y Wang is with the Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, PRC(e-mail: author@https://www.sodocs.net/doc/358561633.html,). S Li, corresponding author, is with the Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, PRC(phone: 027-8754****; fax:027-8754****; e-mail: author@ https://www.sodocs.net/doc/358561633.html,) W Zhao is with the Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, PRC (e-mail: author@https://www.sodocs.net/doc/358561633.html,) , he is also with the Department of Electronic, Wuhan University of Science and Technology, Wuhan 430081, Hubei, PRC.

大疆御操作指南精编WORD版

大疆御操作指南精编 W O R D版 IBM system office room 【A0816H-A0912AAAHH-GX8Q8-GNTHHJ8】

一、功能亮点 MavicPro配备28mm（35mm格式等效）低畸变广角相机和高精度防抖云台，可拍摄1200万像素JPEG以及无损RAW格式的照片及4K超高清视频。信号传输距离最远可达7km。二、飞行模式 1、P模式（定位）：使用GPS模块和前视视觉系统和下视视觉系统以实现飞行器精确悬停、指点飞行以及高级模式等功能。P模式下，GPS信号良好时，利用GPS可精准定位；GPS信号欠佳，光照条件满足视觉系统需求时利用视觉系统定位。开启前视避障功能且光照条件满足视觉系统需求时，最大飞行姿态角为16°，最大飞行速度10m/s。未开启前视避障功能时最大飞行姿态角为25°，最大飞行速度16m/s。在GPS卫星信号差或者指南针受干扰、并且不满足视觉定位工作条件时，飞行器将进入姿态（ATTI)模式。姿态模式下，飞行器容易受外界干扰，从而在水平方向将会产生飘移；并且视觉系统以及部分智能飞行模式将无法使用。因此，该模式下飞行器自身无法实现定点悬停以及自主刹车，请尽快降落到安全位置以避免发生事故。同时应当尽量避免在GPS卫星信号差以及狭窄空间飞行，以免进入姿态模式，导致飞行事故。 2、S模式（运动）：

使用GPS模块以实现精确悬停。飞行器操控感度经过调整，最大飞行速度将会提升。当选择使用S模式时，前视视觉系统将自动关闭，飞行器无法自行避障。S模式下不支持地面站及高级模式功能。 3、注意：在使用S模式（运动）飞行时，前视视觉系统不会生效，飞行器无法主动刹车和躲避障碍物，用户务必留意周围环境，操控飞行器躲避飞行路线上的障碍物。三、飞行器状态指示灯说明四、自动返航（智能返航，智能低电量返航以及失控返航。） 1、记录返航点起飞时或飞行过程中，GPS信号首次达到（四格及以上）时，将记录飞行器当前位置为返航点，记录成功后，飞行器状态指示灯将快速闪烁若干次。 2、失控返航当GPS信号良好，指南针工作正常，且飞行器成功记录返航点后，当无线信号在RC 控制模式下中断3秒或以上，或在Wi-Fi控制模式下中断20秒或以上，飞控系统将接管飞行器控制权，控制飞行器飞回最近记录的返航点。如果在返航过程中，无线信号恢复正常，返航过程仍将继续，用户可短按遥控器智能返航按键以取消返航。注意： a.当GPS信号欠佳或者GPS不工作时，无法实现返航。

Word 操作指南

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小。 4、调整段落。选中正文的所有文字，在空白处单击右键，找到“段落…”，这里要进行两个设置。 1）首行缩进。也就是每段第一行空出两格的设置。在“段落”里找到“首行缩进”点击。它的值是“2字符”。 2）文字行与行之间的间距设置。，找到“行距”，你可以选择“单倍行距”，也可以选择“1.5倍行距”，这样，两行文字之间的空隙就开以调整了，一般情况下，“1.5倍行距”比较合适。 5、调整字体首先选中文字，，在这里选出想要的字体。“宋体”，“黑体”“楷体”都行。 6、调整字体颜色。题目和文字，可以设置不同的颜色。，找到上面工具条的大写A，点击后面的小三角，里面有很多颜色，你可以选择。 7、保存。

Word 文档操作指南

Word 文档操作指南在键盘的功能区有一个INSERT键，这个键可以调输入模式，你说的问题，是你的INSERT 处于覆盖状态了，也就是说你在前面打字的会覆盖掉后面的文字，如果出现这种情况你再按一下INSERT键，看问题解决了吧 ▲~~~~~~~~~~~~~~~~再告诉你一些Word快捷键吧，着些对你是很有帮助的虽然多，慢慢记 [F1]键：帮助 [F2]键：移动文字或图形，按回车键确认 [F4]键：重复上一次的操作 [F5]键：编辑时的定位 [F6]键：在文档和任务窗格或其他Word窗格之间切换 [F8]键：打开Word的选择模式 [F12]键：打开“另存为”对话框 [shift+F2]组合键：复制文本 [shift+F3]组合键：改变字母大小写 [shift+F4]组合键：重复查找或定位有 [shift+F12]组合键：选择“文件”菜单中的“保存”菜单项 [shift+F5]组合键：跳转文档中上一次编辑位置 [shift+←] 组合键：选中光标左侧一个字符 [shift+→] 组合键：选中光标右侧一个字符 [shift+↑] 组合键：选中光标当前位置至上一行之间的内容 [shi ft+↓] 组合键：选中光标当前位置至下一行之间的内容 [shift+Ena] 组合键：选中光标所在处至行尾 [shift+Home] 组合键：选中光标所在处至行首 [shift+pageup] 组合键：选中光标当前位置至上一屏之间的一行内容 [Shift+Pagedown] 组合键：选中光标当前位置至下一屏之间的一行内容 [ctri+F2] 组合键：打印预览 [ctri+F4] 组合键：关闭窗口 [ctri+F6] 组合键：在打开的文档之间切换 [ctri+F12] 组合键：打开“打开”对话框 [ctri+1] 组合键：单倍行距 [ctri+2] 组合键：双倍行距 [ctri+5] 组合键：1.5倍行距 [ctri+O] 组合键：段前添加一行间距 [ctri+A] 组合键：全选 [ctri+B] 组合键：字符变为粗体 [ctri+C] 组合键：复制 [ctri+shift+D] 组合键：分散对齐 [ctri+E] 组合键：段落居中 [ctri+F] 组合键：查找

word模块操作指南

1、设置页眉页脚。答：视图→页眉页脚→出现页眉页脚工具条。在工具条中的页面设置中，可以设置首页不同和奇偶页不同。如果要消除页眉的横线，选选定页眉然后在格式→样式和格式→选择正文。 2、批注答：在视图→标记点选的情况下，可以在需要加批注的部分，插入→批注。点算标记可以隐藏或显示批注。 3、如何进行简体、繁体之间的转换。答：工具→语言→中文简繁转换。 4、公式编辑器的使用。答：1.插入---对象----“microsoft 公式3.0” 2.进行公式的设置。 5、去除绘图时出现的画布。答：工具→选项→常规→去除“插入自选图形时自动创建画布”复选框6、使用索引和目录答：1.定位到放置的位置 2.选择“插入/引入/索引和目录”命令 3.打开“索引和目录”对话框，选择“目录”选项卡 4.设置完毕后，点确定 7、为汉字加注音 1.选定文字 2.格式---中文版式----拼音指南—确定 3.选择相应设置，字体、大小等

8、进行中文版式其他设置：带圈字符、纵横混排，双行合一、合并字符： 1.选定文字 2.格式---中文版式----带圈字符、纵横混排，双行合一、合并字符—确定9、快速输入特殊符号 1.选定位置 2.插入----特殊符号 3.选择对应符号 10、调整单元格中文字对齐方式选中需要调整的表格，点击鼠标右键，调整对齐方式. 11、设置表格标题行重复选中表格的第一行---选择表格菜单----标题行重复。 12、替换文章中内容：编辑菜单---替换---在查找内容中输入需要替换的内容----在替换为中输入新内容----点击全部替换----关闭。 13、设置“标题1”样式：选中需要设置的内容----点击格式菜单----样式和格式----选择标题一-----然后根据题目调整字体大小。 14、设置字体格式：选中需要设置的内容---格式---字体—设置字体、字形、字号等。 15、设置段落格式：选中需要设置的内容---格式----段落---设置段前段后间距、特殊格式里的首行缩进—行距里的1.5倍行距等。

word高级使用技巧操作指南

Word2007高级使用技巧 1.利用标题样式统一文档格式我们日常使用Word工作时，除了文档的录入之外，我们的绝大部分时间都花在文档的修饰上，样式则正是专门为提升文档的修饰效率而提出的。使用样式能够协助用户确保格式编排的一致性，从而减少很多重复的操作，并且不需要重新设置文本格式，就可快速更新一个文档的设计，在短时间内排出高质量的文档。我们常用的是为案例文档的标题设置相对应的标题样式。 (1) 打开word2007文档，选择菜单栏中的“开始”选项，在下面的工具栏中既有相对应的“样式”的任务窗格。打开之后，我们能够看到它的列表中列出了现有的几种样式，如“标题1”、“标题2”等。 (2) 把插入点定位于将要执行样式更改的标题段落，然后用鼠标点一下“样式”任务窗格中的“标题1”，这时能够看到插入点所在的标题段落被应用了“标题1”样式。 (3) 用同样的方法为案例文档中其它的标题指定相对应的标题样式，全部完成后请保存一下文件。此时，即可将案例文档中的所有标题设置了相对应等级层次的标题样式了。 2.基于样式快速生成目录要自动生成案例文档的目录，首先是要对目录的标题实行样式设置定义，然后再自动生成目录。创建目录最简单的方法就是使用内置的标题样式。 (1)打开案例文档，将文档中的各标题按照上述所讲的“标题样式”定义。 (2)点击word2007菜单栏中的“引用”按钮，找到“目录”选项，点击“目录”选项下面的倒三角，选择“自动目录”。这时候即可自动生成相对应的目录。 (3)如果对生成的目录需要调整，经调整后点击“更新目录”，即可将目录实行更新。

3.个性设置页眉页脚 (1)打开“页眉页脚”工具栏单击菜单栏中的“插入”按钮，便能够看到“页眉页脚”任务窗口。点击“页眉”/“页脚”选项，然后选择“编辑页眉”/“编辑页脚”选项，既能够进入编辑状态，如图： (2)编辑页眉页脚 A进入编辑状态将鼠标指针移至页眉框内，即可开始输入和编辑页眉页脚的内容。要回到主文档，可选择“页眉和页脚”工具栏上的“关闭”按钮，或者双击主文本区。要重新进入页眉和页脚编辑状态，可在主文档页眉或页脚区域内双击。当然，在“转至页眉”/“转至页脚”选项中，能够变换“页眉”或者“页脚”的编辑。 B设置文档奇偶页不同页眉有的文档可能需要给奇数页和偶数页设置不同的页眉或页脚。要使奇偶页的页眉和页脚不同，也是通过“页眉页脚”工具栏中来实现。方法是在出现的“设计”菜单中勾选“奇偶页不同”选择框。设置文档奇偶页不同页眉：“奇数页页眉”输入内容后，点击“页眉和页脚”工具栏的“显示下一项”按钮，即转换到“偶数页页眉”编辑状态。（“偶数页页眉”输入内容后，单击“显