Preparation-of-activated-carbon-from-cattail-and-its-application-for-dyes-removal

Journal of Environmental Sciences2010,22(1)91–97

Preparation of activated carbon from cattail and its application

for dyes removal

Qianqian Shi1,Jian Zhang1,?,Chenglu Zhang1,Cong Li1,Bo Zhang1,

Weiwei Hu2,Jingtao Xu1,Ran Zhao1

1.School of Environmental Science and Engineering,Shandong University,Jinan250100,China.E-mail:shuipingdingding@https://www.sodocs.net/doc/a16448191.html,

2.State Key Joint Laboratory of Environmental Simulation and Pollution Control,College of Environmental Sciences

and Engineering,Peking University,Beijing100871,China

Received25February2009;revised14August2009;accepted28August2009

Abstract

Activated carbon was prepared from cattail by H3PO4activation.The e?ects in?uencing the surface area of the resulting activated

carbon followed the sequence of activated temperature>activated time>impregnation ratio>impregnation time.The optimum

condition was found at an impregnation ratio of2.5,an impregnation time of9hr,an activated temperature of500°C,and an activated

time of80min.The Brunauer-Emmett-Teller surface area and average pore size of the activated carbon were1279m2/g and5.585 nm,respectively.A heterogeneous structure in terms of both size and shape was highly developed and widely distributed on the carbon

surface.Some groups containing oxygen and phosphorus were formed,and the carboxyl group was the major oxygen-containing

functional group.An isotherm equilibrium study was carried out to investigate the adsorption capacity of the activated carbon.The

data?t the Langmuir isotherm equation,with maximum monolayer adsorption capacities of192.30mg/g for Neutral Red and196.08

mg/g for Malachite Green.Dye-exhausted carbon could be regenerated e?ectively by thermal treatment.The results indicated that

cattail-derived activated carbon was a promising adsorbent for the removal of cationic dyes from aqueous solutions.

Key words:cattail;activated carbon;H3PO4activation;dyes removal;regeneration

DOI:10.1016/S1001-0742(09)60079-6

Introduction

Cattail is one of the most common aquatic plants,and

it can be found worldwide in wetlands,fens,margins of

ponds and lakes,roadside ditches,irrigation canals,and

backwater areas of rivers and streams(Kim et al.,2003).

It is a very recognizable aquatic wetland plant that can

provide excellent cover and nesting habitat for certain

wildlife.Cattail can utilize solar energy e?ectively and

grow rapidly.Its rapid growth produces a large amount of

biomass,which can become a potential pollution resource

to the environment(Hu and Yu,2006).This motivates the

investigation of producing value-added products,such as

activated carbon,from this abundant material.

Activated carbon is a well-known material used in both

gas and liquid phases,including medicinal use,gas storage,

pollutant and odor removal,gas separation,and catalysis

(Nabais et al.,2008).However,commercially available

activated carbons are still considered expensive materials

for many countries due to the use of non-renewable and

relatively expensive starting materials such as coal(Martin

et al.,2003).Practically any carbonaceous material,natural

or synthetic,rich in carbon and low in ash,is theoretically

*Corresponding author.E-mail:zhangjian00@https://www.sodocs.net/doc/a16448191.html,

feasible for activated carbon production(Attia et al.,2008).

Therefore,in recent years,this has prompted a growing

interest in the research on the production of activated

carbons from cheaper and renewable precursors,which

are mainly industrial and agricultural byproducts,such as

rice hull(Guo and Rockstraw,2007),olive cake(Aljundi

and Jarrah,2008),corncob(Tseng et al.,2006),apricot

stone(Karagozoglu et al.,2007),date stone(Bouchelta et

al.,2008),coconut husk(Tan et al.,2008),rattan sawdust

(Hameed et al.,2008),and bagasse bottom ash(Aworn et

al.,2008).However,there are only a few reports on the

preparation of cattail-derived activated carbon.

The manufacture of activated carbons generally in-

volves two steps:pyrolysis and physical and/or chemical

https://www.sodocs.net/doc/a16448191.html,pared with physical activation,chemical

activation has a lower temperature and a higher carbon

product yield(Uˇg urlu et al.,2008).Chemical activation

consists of carbonization in the presence of a dehydrating

chemical agent(e.g.,ZnCl2,H3PO4,and H2SO4).These

chemical agents enhance carbonization,thus resulting in

the development of a desired pore structure.From both

economic and environmental perspectives,H3PO4is the

preferred chemical agent because it is recoverable(Guo

and Rockstraw,2006),and the activation temperature

92Qianqian Shi et al.V ol.22

involved is relatively low(around400–500°C).

The principal objective of this study is to prepare an activated carbon from cattail by H3PO4activation and mea-sure its dye adsorption properties.In order to optimize the experimental procedure,orthogonal array design(OAD) was employed.The theory and methodology of OAD as a chemometric method for the optimization of analytical procedures has been described in detail elsewhere(Sobhi et al.,2008;Yamini et al.,2008).OAD procedure with OA9(34)matrix was applied to study the e?ect of ex-perimental factors on the carbon surface area.The results of OAD experiment were then treated by range analysis. The sample under optimum condition was analyzed for a detailed study of its carbon characteristics,dye adsorption, and thermal regeneration.Two cationic dyes,Neutral Red and Malachite Green,were selected as absorbates in the adsorption and regeneration experiments.

1Materials and methods

1.1Raw material

Cattail used in this study was obtained from a local wetland near Jinan,China.All reagents were analytical grade.

1.2Preparation of activated carbon

Cattail was washed,dried,ground in a laboratory mill, and then impregnated with a40wt.%H3PO4solution at a certain ratio.The resulting wet mass was placed in a mu?e furnace and heated for several minutes with the ?nal activated temperatures.It was cooled down afterwards to room temperature.The carbonized material produced was washed with deionized water until its?ltrate reached neutral pH and then dried at120°C for2hr.

1.3Orthogonal experiment

OA9(34)matrix was employed to study the e?ect of four factors in?uencing the carbon surface area:impregnation ratio,impregnation time,activated temperature,and acti-vated time.Emphasis was placed on the main e?ect of the four factors;thus,the possible interactions between them were not in the matrix.The factors and levels of orthogonal experiment are presented in Table1.

1.4Characterization of activated carbon

The textural properties of activated carbon were deter-mined by N2adsorption(at–196°C)using QUADRA-SORB SI automated surface area and pore size analyzer (Quantachrome Corporation,USA).The surface area Table1Factors and levels of the orthogonal experiment

Level Impregnation Impregnation Activated Activated ratio time temperature time

(m H:m C)(hr)(°C)(min)

1 2.2640040

2 2.5945060

3 2.81250080

m H:amount of phosphoric acid;m C:amount of cattail.and pore size distribution were estimated following the Brunauer-Emmett-Teller(BET)method and Density Func-tional Theory(DFT)method,respectively.The total volume and average pore size were measured using Quadrawin software.The micropore volume and external surface area were calculated by the t-plot method.

The surface morphology of carbon was observed by scanning electron microscopy(SEM)(Hitachi S-520, Japan).The sample was gold coated prior to SEM ob-servation.The surface chemistry characterization of the sample was performed using Fourier Transform Infrared Spectroscopy(FT-IR)and Boehm titration.The infrared spectrum of carbon was recorded at room temperature by an Avatar370spectrometer(Nicolet Instrument Corpora-tion,USA)using the KBr disc method.Boehm titration was employed to determine the acidic surface groups of carbon qualitatively(Boehm,1966).

1.5Adsorption experiments

Two cationic dyes,Neutral Red(NR,C15H16N4HCl,λmax=530nm)and Malachite Green(MG,C23H25N2Cl,λmax=618nm),were used in the experiments.For each

experiment,100mg of activated carbon was added to a 100-mL dye solution,with an initial concentration ranging from80to200mg/L.Afterwards,the mixture was shaken for250min at10,26,and45°C.The residual concentration was determined by measuring its absorbance in a UV-Visible spectrophotometer(UV-754,Shanghai,China)at the maximum wavelength of the dye.The amount of dye adsorbed was calculated from the following mass balance equation(Eq.(1)):

q e=

(C0?C1)V

m

(1)

where,C0and C1are the initial and?nal dye concentra-tions,respectively;V is the volume of solution;and m is the mass of carbon.

1.6Thermal regeneration of spent activated carbon

In the experiment,300mg of carbon was added to a 300-mL dye solution(200mg/L),and the suspension was mechanically shaken for250min at26°C.The solution was then?ltered out,and the amount of dye adsorbed was calculated.The spent activated carbon was loaded into the furnace,heated at300°C for30min,and then allowed to cool down at room temperature.Subsequently,the adsorption experiment was carried out again to evaluate the regeneration e?ciency(R)of carbon,which was calculated according to the following expression(Eq.(2)):

R=

M rc

M vc

(2)

where,M rc and M vc are amounts adsorbed on regenerated and virgin carbon,respectively.

No.1Preparation of activated carbon from cattail and its application for dyes removal

93

Fig.1E ?ects of factors on the BET surface area of activated carbon.

2Results and discussion

2.1Range analysis

The results of designing the orthogonal experiment are shown in Table 2.Under the range analysis,the average of BET surface areas for each factor at di ?erent levels (K 1,K 2,and K 3)and the range R are given in Table 2.

The impregnation ratio (A),impregnation time (B),ac-tivated temperature (C),and activated time (D)all a ?ected the BET surface area.As shown in Fig.1,the mean values (K 1,K 2and K 3)reveal how the BET surface area will change when the level of that factor is changed as well.As shown in Table 2,with decrease sequence of R ,the order of factors in?uencing BET surface area was C >D >A >B.The results of K were K 2(A)>K 3(A)>K 1(A),K 2(B)>K 3(B)>K 1(B),K 3(C)>K 2(C)>K 1(C),and K 3(D)>K 2(D)>K 1(D).Therefore,the best combination was A 2B 2C 3D 3,that is,the optimum condition had an impregnation ratio 2.5,impregnation time 9hr,activated temperature 500°C,and activated time 80min.2.2Additional experiment

The optimum condition was not included in the experi-mental combinations.Therefore,an additional experiment under this condition was carried out to verify the combi-nation A 2B 2C 3D 3with the largest BET surface area.The result of the BET surface area in the additional experiment was 1279m 2/g,which was larger than any value of the BET surface area above,con?rming that the optimum condition was suitable.The result reported here may also be compared with that of commercially available carbons,which typically have a surface area in the range 400–1500m 2/g (Williams and Reed,2003).The activated carbon obtained under the optimum condition (named as AC-1)was then used for carbon characteristics,dye adsorption,and thermal regeneration.

2.3Surface area and pore size distribution

N 2adsorption is considered the standard procedure for the characterization of the porosity texture of carbona-ceous adsorbents.The isotherm can provide information on the porous structure of the adsorbent,heat of adsorp-tion,characteristics of physics and chemistry,and so on (¨Onal,2006).Figure 2shows the N 2adsorption /desorption isotherm (–196°C)of AC-1,which is classi?ed as a type IV according to International Union of Pure and Applied Chemistry.The isotherm indicates the micro-mesoporous structure of the carbon.The initial part of the isotherm

fol-

Fig.2Adsorption /desorption isotherm of nitrogen at –196°C for AC-1.

lows the same path as the corresponding type II isotherm,and thus resulting to the monolayer-multilayer adsorption on the mesopore walls (Ryu et al.,1999).

The adsorption measurement provides a useful “?nger-print”of the microstructure,and it is essential if the carbon is utilized as an adsorbent or catalyst support.The pore size distribution seems to provide especially useful information on porous solids (Seaton et al.,1989).Figure 3shows the pore size distribution of AC-1,the results of which and the BET surface area are presented in Table 3.It is observed that the activated carbon prepared from cattail has a high surface area,which is primarily attributed to the mesopores and macropores as the percent contribution of micropores is only 13.6%of the BET surface area.The total pore volume was as high as 1.786cm 3/g for AC-1,which could be compared with that of commercially activated carbons,that is,0.60and 0.52cm 3/g for carbons BPL and PCB produced by Calgon Carbon Co.,Pittsburgh,USA,respectively (Ioannidou and Zabaniotou,2007).The average pore size of 5.585nm was also obtained.These illustrate the notion that cattail is a suitable precursor for the preparation of meso-activated carbon by H 3PO 4activation.

2.4SEM analysis of microstructure

The microstructure of AC-1is shown in Fig.4.The scanning electron micrograph of AC-1showed an ir-regular and heterogeneous surface morphology with a well-developed porous structure.Pores of di ?erent sizes shapes could be observed.The external surface of the activated carbon was full of cavities and quite irregular.The development of the pore system in carbon depends on the structure of the starting material and the activated

94Qianqian Shi et al.

V ol.22

Table 2Design and results of the orthogonal experiment

Number Impregnation Impregnation Activated

Activated BET surface ratio (m H :m C )time (hr)temperature(°C)time (min)area (m 2/g)111114192122294831333112142132118252213109362321100373123102383231100093312812

K 1829.3874.7774.7807.3K 21092.71013.7991.3980.7K 3945978.711011079R

263.4

139

326.3

271.7

m H :amount of phosphoric acid;m C :amount of cattail.K (K 1,K 2,K 3)is the average of BET surface areas for each factor at di ?erent levels.

Table 3Surface area and porosity of AC-1

S BET (m 2/g)S ext (m 2/g)S ext (%)S mic (m 2/g)S mic (%)V t (cm 3/g)V mic (cm 3/g)V mic (%)D p (nm)1279

1105

86.4

174

13.6

1.786

0.088

4.93

5.585

S BET :BET surface area;S ext :external surface area;S mic :micropore surface area;V t :total pore volume;V mic :micropore volume;D p :average pore

size.

Fig.3Pore size distribution of AC-1.

process.The cavities resulted from the evaporation of the chemical reagent (H 3PO 4)during carbonization,leaving the space previously occupied by the reagent (El-Hendawy et al.,2008).

2.5Fourier transform infrared spectroscopy (FT-IR)

results In this study,FT-IR was used to obtain information on the chemical structure and functional groups of the prepared activated carbon (Fig.5).A broad band located around 3400cm ?1is typically attributed to the hydroxyl groups or adsorbed water.The band around 1700cm ?1is usually caused by the stretching vibration of C ==O in ketones,aldehydes,lactones,and carboxyl groups,while the band around 1600cm ?1is ascribed to the aromatic ring or C ==C stretching vibration.This indicates the formation of carbonyl-containing groups and the aromatization of the precursor (Guo and Rockstraw,2007).The band around 1220cm ?1is typically attributed to the C–O band.In H 3PO 4activation,the reagent (H 3PO 4)promotes depoly-merization,dehydration,and redistribution of constituent biopolymers,inducing important changes in the

pyrolytic

Fig.4

Scanning electron micrograph of AC-1.

decomposition of the lignocellulosic materials and thus favoring the conversion of aliphatic to aromatic com-pounds at low temperatures (Jagtoyen and Derbyshire,1993).For the FT-IR spectrum of carbon prepared by H 3PO 4activation,the band in the region of 1300–900cm ?1could be caused by the phosphorus-containing groups.The peak around 1220–1180cm ?1could be attributed to the stretching of P ==O bond in a phosphate ester,O–C bond in P–O–C linkage,or P ==OOH bond.This indicates the presence of phosphorus-containing groups in the carbon (Puziy et al.,2002).2.6Boehm titration

Boehm titration is one of the most widely used meth-ods to quantify acidic groups with di ?erent strengths on

No.1Preparation of activated carbon from cattail and its application for dyes removal 95

activated carbons.It is initially used for the di ?erentiation of oxygen-containing groups,including carboxyl,lactone,phenol,and carbonyl groups.On the surface of AC-1,carboxyl,lactone,and carbonyl groups were detected,the concentrations of which were 1.695,0.028,and 0.181meq /g,respectively.The concentration of carboxyl group was signi?cantly higher compared with the other two groups,indicating that carboxyl group was more prevalent on the surface of AC-1.

2.7Adsorption isotherms of AC-1for the dyes The produced activated carbon (AC-1)was tested for its adsorption capacity for NR and MG.The amount of dye adsorbed can be determined as a function of the concentration at a constant temperature,which can be explained by adsorption isotherms.In this study,analysis of the adsorption isotherms was carried out by applying

the

Fig.5FT-IR spectrum of AC-1.

linear Langmuir equation (Eq.(3)):C e q e =1Q m K L +C e

Q m

(3)

and the Freundlich equation (Thinakaran et al.,2008),log q e =log K F +1

n

log C e (4)

where,C e (mg /L)is the concentration of the dye solution at equilibrium;q e (mg /g)is the amount of dye adsorbed per unit weight of activated carbon at equilibrium;K L (L /mg)is a Langmuir constant related to the free energy of adsorption;and Q m (mg /g)is the maximum adsorption capacity.K F is a Freundlich constant indicating the relative adsorption capacity of the carbon,and 1/n is the adsorption intensity.

The Langmuir and Freundlich plots for the system stud-ied are presented in Fig.6,while the isotherm constants and correlation coe ?cients are given in Table 4.The Lang-muir and Freundlich isotherms of NR and MG were found to be linear over the whole concentration range studies,and the R 2values showed that the Langmuir model ?t better than the Freundlich model.The values of Q m increased as the temperature rose,thereby con?rming that the processes were both endothermic.At 45°C,the maximum adsorption capacities were determined as 192.30and 196.08mg /g for NR and MG,respectively.This can be compared with the data from the literature.For instance,Bas ?ar (2006)reported that the maximum adsorption capacity at 50°C was determined as 163.93mg /g for MG on apricot-derived activated carbon.Yuan et al.(2007)found that the maximum adsorption capacity at 20°C was approximately 113mg /g for NR on a microporous carbon.The values of 1/n in Table 4were found to be between 0and 1,indicating a favorable adsorption of NR and MG on

AC-1.

Fig.6Isotherm plots for the adsorption of Neutral Red (NR)and Malachite Green (MG)onto AC-1.

96Qianqian Shi et al.V ol.22 Table4Isotherm constants and correlation coe?cients for the removal of NR and MG by AC-1

Dye Temperature Langmuir Freundlich

(°C)Q

m(mg/g)K L(L/mg)R2K F((mg/g)(L/mg)1/n)1/n R2 Neutral Red10181.81 1.300.9995113.580.160.9261 26188.68 2.400.9956128.320.150.9442

45192.30 3.930.9988136.830.160.8819 Malachite Green10192.30 1.860.9971121.900.190.7967 26192.30 3.060.9987135.960.160.7679

45196.08 5.670.9957149.970.150.6818

2.8Regeneration of AC-1

To be a promising adsorbent,AC-1should be readily

regenerated.Experimental results showed that the adsorp-

tion capacities of the regenerated AC-1were determined

as161.68and157.64mg/g for NR and MG,and the

regeneration e?ciencies were82.96%and79.64%,re-

spectively.This demonstrates the e?ectiveness of thermal

treatment in the regeneration of dye-exhausted AC-1,and

it is expected that this method can be applied to regenerate

AC-1exhausted with other organic pollutants.

3Conclusions

In the study,an activated carbon with high surface area

was prepared from a commonly available hydrophyte-

cattail by H3PO4activation.Orthogonal analysis was used

to investigate the factors in?uencing the surface area,the

sequence of which was activated temperature>activated

time>impregnation ratio>impregnation time.The best

condition for the carbon production was as follows:im-

pregnation ratio=2.5,impregnation time=9hr,activated

temperature=500°C,and activated time=80min.At

the optimum condition,the activated carbon obtained was

essentially mesoporous with a BET surface area of1279

m2/g and average pore size of5.585nm.The SEM showed a heterogeneous surface with a well-developed porous

structure.FT-IR proved the presence of di?erent oxygen-

containing and phosphorus-containing groups.Carboxyl,

lactone,and carbonyl groups were measured by Boehm

titration,with the carboxyl group being the major oxygen

functional group on the carbon surface.The activated

carbon could e?ectively remove NR and MG from aqueous

solutions.The equilibrium data followed the Langmuir

model,showing the maximum monolayer adsorption ca-

pacities of192.30mg/g for NR and196.08mg/g for MG.

Thermal treatment e?ectively regenerated the adsorption

capacities of carbon,with the regeneration e?ciencies

being high.In conclusion,cattail is a potential and low-cost

natural material for the preparation of activated carbon. Acknowledgments

The work was supported by the National Key Tech-

nology R&D Program for the11th Five-year Plan of

China(No.2006BAC10B03),the National Natural Sci-

ence Foundation of China-Japan Science and Technology

Agency(NSFC-JST)Strategic Joint Research Project(No.

50721140017),and the National Natural Science Founda-

tion of China(No.50508019).References

Aljundi I H,Jarrah N,2008.A study of characteristics of activat-ed carbon produced from Jordanian olive cake.Journal of Analytical and Applied Pyrolysis,81(1):33–36.

Attia A A,Girgis B S,Fathy N A,2008.Removal of methylene blue by carbons derived from peach stones by H3PO4 activation:batch and column studies.Dyes and Pigments, 76(1):282–289.

Aworn A,Thiravetyan P,Nakbanpote W,2008.Preparation and characteristics of agricultural waste activated carbon by physical activation having micro-and mesopores.Journal of Analytical and Applied Pyrolysis,82(2):279–285.

Bas?ar C A,2006.Applicability of the various adsorption models of three dyes adsorption onto activated carbon prepared waste apricot.Journal of Hazardous Materials,135(1-3): 232–241.

Boehm H P,1966.Chemical identi?cation of surface groups.

Advances in Catalysis,16:179–274.

Bouchelta C,Medjram M S,Bertrand O,Bellat J P,2008.

Preparation and characterization of activated carbon from date stones by physical activation with steam.Journal of Analytical and Applied Pyrolysis,82(1):70–77.

El-Hendawy A N A,Alexander A J,Andrews R J,Forrest G,2008.E?ects of activation schemes on porous,surface and thermal properties of activated carbons prepared from cotton stalks.Journal of Analytical and Applied Pyrolysis, 82(2):272–278.

Guo Y,Rockstraw D A,2006.Physical and chemical properties of carbons synthesized from xylan,cellulose,and Kraft lignin by H3PO4activation.Carbon,44(8):1464–1475. Guo Y,Rockstraw D A,2007.Activated carbons prepared from rice hull by one-step phosphoric acid activation.Microp-orous and Mesoporous Materials,100(1-3):12–19. Hameed B H,Chin L H,Rengaraj S,2008.Adsorption of4-chlorophenol onto activated carbon prepared from rattan sawdust.Desalination,225(1-3):185–198.

Hu Z H,Yu H Q,2006.Anaerobic digestion of cattail by rumen cultures.Waste Management,26(11):1222–1228. Ioannidou O,Zabaniotou A,2007.Agricultural residues as precursors for activated carbon production–a review.

Renewable and Sustainable Energy Reviews,11(9):1966–2005.

Jagtoyen M,Derbyshire F,1993.Some considerations of the origins of porosity in carbons from chemically activated wood.Carbon,31:1185–1192.

Karagozoglu B,Tasdemir M,Demirbas E,Kobya M,2007.

The adsorption of basic dye(Astrazon Blue FGRL)from aqueous solutions onto sepiolite,?y ash and apricot shell activated carbon:kinetic and equilibrium studies.Journal of Hazardous Materials,147(1-2):297–306.

Kim C,Shin H,Choi H K,2003.A phenetic analysis of Typha in Korea and far east Russia.Aquatic Botany,75(1):33–43.

No.1Preparation of activated carbon from cattail and its application for dyes removal97

Martin M J,Artola A,Balaguer M D,Rigola M,2003.Activated carbons developed from surplus sewage sludge for the removal of dyes from dilute aqueous solutions.Chemical Engineering Journal,94(3):231–239.

Nabais J V,Carrott P,Carrott M M L R,Luz V,Ortiz A L, 2008.In?uence of preparation conditions in the textural and chemical properties of activated carbons from a novel biomass precursor:the co?ee endocarp.Bioresource Tech-nology,99(15):7224–7231.

¨Onal Y,2006.Kinetics of adsorption of dyes from aqueous so-lution using activated carbon prepared from waste apricot.

Journal of Hazardous Materials,137(3):1719–1728. Puziy A M,Poddubnaya O I,Mart′?nez-Alonso A,Su′a rez-Garc′?a F,Tasc′o n J M D,2002.Synthetic carbons activated with phosphoric acid:I.Surface chemistry and ion binding properties.Carbon,40(9):1493–1505.

Ryu Z,Zheng J,Wang M,Zhang B,1999.Characterization of pore size distributions on carbonaceous adsorbents by DFT.

Carbon,37(8):1257–1264.

Seaton N A,Walton J P R B,Quirke N,1989.A new analysis method for the determination of the pore size distribution of porous carbons from nitrogen adsorption measurements.

Carbon,27(6):853–861.

Sobhi H R,Yamini Y,Esra?li A,Abadi R H H B,2008.

Suitable conditions for liquid-phase microextraction using solidi?cation of a?oating drop for extraction of fat-soluble vitamins established using an orthogonal array experimen-tal design.Journal of Chromatography A,1196-1197(1-2): 28–32.

Tan I A W,Ahmad A L,Hameed B H,2008.Adsorption of basic dye on high-surface-area activated carbon prepared from

coconut husk:equilibrium,kinetic and thermodynamic studies.Journal of Hazardous Materials,154(1-3):337–346.

Thinakaran N,Panneerselvam P,Baskaralingam P,Elango D, Sivanesan S,2008.Equilibrium and kinetic studies on the removal of Acid Red114from aqueous solutions using activated carbons prepared from seed shells.Journal of Hazardous Materials,158(1):142–150.

Tseng R L,Tseng S K,Wu F C,2006.Preparation of high surface-area carbons from corncob with KOH etching plus CO2gasi?cation for the adsorption of dyes and phenols from water.Colloids and Surfaces A:Physicochemical and Engineering Aspects,279(1-3):69–78.

Uˇg urlu M,G¨u rses A,Ac??ky?ld?z M,https://www.sodocs.net/doc/a16448191.html,parison of textile dyeing e?uent adsorption on commercial activated carbon and activated carbon prepared from olive stone by ZnCl2 activation.Microporous and Mesoporous Materials,111(1-

3):228–235.

Williams P T,Reed A R,2003.Pre-formed activated carbon matting derived from the pyrolysis of biomass natural?ber textile waste.Journal of Analytical and Applied Pyrolysis, 70(2):563–577.

Yamini Y,Saleh A,Khajeh M,2008.Orthogonal array design for the optimization of supercritical carbon dioxide extraction of platinum(IV)and rhenium(VII)from a solid matrix using cyanex301.Separation and Puri?cation Technology,61(1): 109–114.

Yuan X,Zhuo S P,Xing W,Cui H Y,Dai X D,Liu X M et al.,2007.Aqueous dye adsorption on ordered mesoporous carbons.Journal of Colloid and Interface Science,310(1): 83–89.