胰腺内副脾误诊2例报告张孟哲，饶洁，张正乐武汉大学人民医院胰腺外科，武汉 430060通信作者：张正乐，**************（ORCID： 0000-0003-1895-4366）摘要：副脾是指正常脾脏以外存在的，与主脾结构相似，有一定功能的脾脏组织，其中完全被胰腺包裹的胰腺内副脾（IPAS）发生率仅为2%，因其临床症状不典型，影像学特征与胰腺神经内分泌肿瘤、胰腺实性假乳头状瘤以及其他胰腺占位性病变较为相似，临床上容易误诊。
本文报道了2例分别被误诊为胰腺神经内分泌肿瘤和胰腺实性假乳头状瘤的IPAS患者，并分析误诊原因，总结诊疗经验，以期提升临床对IPAS明确鉴别诊断的认识。
关键词：脾疾病；胰腺；误诊；神经内分泌瘤；乳头状瘤Misdiagnosis of intrapancreatic accessory spleen： A report of two casesZHANG Mengzhe， RAO Jie， ZHANG Zhengle.（Department of Pancreatic Surgery， Renmin Hospital of Wuhan University， Wuhan 430060， China）Corresponding author： ZHANG Zhengle，**************（ORCID： 0000-0003-1895-4366）Abstract：Accessory spleen refers to the spleen tissue that exists outside of the normal spleen， with a similar structure to the main spleen and certain functions. Intrapancreatic accessory spleen （IPAS） completely enveloped by the pancreas has an incidence rate of only 2%， and it is easily misdiagnosed in clinical practice due to its atypical clinical symptoms and similar radiological features to pancreatic neuroendocrine tumor，pancreatic solid pseudopapillary tumor，and other pancreatic space-occupying lesions. This article reports the clinical data of two patients with IPAS who were misdiagnosed as pancreatic neuroendocrine tumor and pancreatic solid pseudopapillary tumor， respectively， analyzes the reasons for misdiagnosis， and summarizes the experience in diagnosis and treatment， in order to improve the ability for the differential diagnosis of IPAS in clinical practice.Key words：Splenic Diseases； Pancreas； Diagnostic Errors； Neuroendocrine Tumors； Papilloma1 病例资料病例1：患者女性，58岁，以“体检发现胰腺尾部占位3天”于2019年3月4日入本院，患者2年来体质量下降5 kg，增强CT检查示：胰腺尾部动脉期以及门静脉期显著强化结节，动脉期CT值为198 HU，考虑神经内分泌肿瘤（图1）。
Carbohydrate Polymers 131(2015)280–287Contents lists available at ScienceDirectCarbohydratePolymersj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /c a r b p olMicrowave preparation of triethylenetetramine modified graphene oxide/chitosan composite for adsorption of Cr(VI)Huacai Ge ∗,Ziwei MaCollege of Chemistry and Chemical Engineering,South China University of Technology,Guangzhou 510640,Chinaa r t i c l ei n f oArticle history:Received 13February 2015Received in revised form 4June 2015Accepted 6June 2015Available online 16June 2015Keywords:Graphene oxide Modified chitosan Microwave Adsorption Cr(VI)a b s t r a c tA novel triethylenetetramine modified graphene oxide/chitosan composite (TGOCS)was successfully synthesized by microwave irradiation (MW)method and compared with one prepared by conventional heating.This composite was characterized by FTIR,XRD,SEM,BET and elemental analysis.Adsorption of Cr(VI)on the composite was studied.The experimental results indicated that the product obtained by MW had higher yield and uptake than one obtained by the conventional and uptake of TGOCS for Cr(VI)was higher than that of the recently reported adsorbents.The effects of various variables on adsorption of Cr(VI)by TGOCS were further researched.The highest adsorption capacity of 219.5mg g −1was obtained at pH 2.Adsorption followed pseudo-second-order kinetic model and Langmuir isotherm.The capacity increased as increasing temperature.The adsorbent could be recyclable.These results have important implications for the application expansion of microwave preparation and the design of new effective composites for Cr(VI)removal in effluents.©2015Elsevier Ltd.All rights reserved.1.IntroductionChromium (VI)(Cr(VI))has been commonly used in a number of industrial processes,such as leather tanning,electroplating,metal polishing,paint manufacturing,and textile coloring (Bhattacharya,Naiya,Mandal,&Das,2008;Li et al.,2013;Ouaissa,Chabani,Amrane,&Bensmaili,2013).Due to its high toxicity and bioac-cumulation,the Cr(VI)from effluents must be removed.Various methods of removing Cr(VI)have been developed,such as chem-ical precipitation (Carlos,Violeta,&Bryan,2012),adsorption (Hu et al.,2011;Huang,Yang,&Liu,2013),electrodeposition (Golder,Samanta,&Ray,2011),membrane systems (Gherasim &Bourceanu,2013),and ion exchange process (Rengaraj,Joo,Kim,&Yi,2003).Among these methods,adsorption is one of the most economically favorable and a technically easy method (Hu et al.,2011).Chitosan (CS),a bio-adsorber,is a biocompatible polysaccha-ride obtained from deacetylation of chitin (Ge &Wang,2014).It can chemically or physically entrap various metal ions due to the presence of amine and hydroxyl groups that can serve as the chelating and reaction sites (Aydın &Aksoy,2009;Ge &Fan,2011;Repo,Koivula,Harjula,&Sillanpää,2013;Wang &Ge,2015).Therefore,chitosan presents as a very promising starting mate-rial for chelating resins (Kandile &Nasr,2009).Several metals are∗Corresponding author.Tel.:+862087112900;fax:+862022236337.E-mail address:chhcge@ (H.Ge).preferentially adsorbed in acidic media while chitosan can dis-solve in acid condition.To overcome this problem,chitosan must be chemically modified with different crosslinking reagents,such as epichlorohydrin and glutaraldehyde (Ge &Huang,2010;Ngah,Endud,&Mayanar,2002).However,the adsorption capacity of crosslinked chitosan would be largely reduced due to the con-sumption of amine groups and hydroxyl groups after chemical modification.Hence,the crosslinked chitosan must be further mod-ified to improve the adsorption performance (Ge,Chen,&Huang,2012;Wu,Li,Wan,&Wang,2012;Zhang,Xia,Liu,&Zhang,2015).Graphene,which can be prepared from the low cost material graphite,is intensively investigated as adsorbents for heavy metal ions (Chowdhury &Balasubramanian,2014;Jabeen et al.,2011).Graphene oxide (GO)obtained by the oxidation of graphene con-tains a wide range of oxygen functional groups both on the basal planes and at the edges of GO sheets,such as –COOH,and –OH.These functional groups are essential for the high sorption of heavy metal ions,and allows GO to participate in a wide range of bond-ing interactions (Guo et al.,2014;Zhang et al.,2014).However,GO is a nano-material with high dispersibility in aqueous solution (Cheng et al.,2013)and has the potential toxicity in environment (Sanchez,Jachak,Hurt,&Kane,2011).These problems may restrict the practical applications of GO as an adsorbent.To overcome these problems,various methods have been investigated,such as for-mation of ethylenediamine modified GO and magnetic graphene nanocomposites (Wang et al.,2014;Zhu et al.,2011).However,these methods revealed low adsorption capacity due to the reduced/10.1016/j.carbpol.2015.06.0250144-8617/©2015Elsevier Ltd.All rights reserved.H.Ge,Z.Ma /Carbohydrate Polymers 131(2015)280–287281adsorption area and oxygen-containing functional groups.Hence,the GO functionalized with magnetic cyclodextrin–chitosan was studied (Li et al.,2013).Recently,microwave irradiation (MW)as a means of chem-ical reaction has been widely applied in polymer synthesis due to higher conversion and shorter reaction times under MW than those of conventional heating (Ge &Luo,2005;Ge,Pang,&Luo,2006;Ge et al.,2012).In this work,microwave technology has been used to prepare a new chitosan-based composite.This work is to serve as not only an expansion of microwave irradiation in applica-tion of polymer synthesis,but also an expansion of chitosan-based nanocomposites as a high-efficient adsorbent for Cr(VI)removal.Considering that amine groups in triethylenetetramine could sig-nificantly enhance the adsorption ability,the triethylenetetramine modified graphene oxide/chitosan composite (TGOCS)was pre-pared by MW and compared with one prepared by conventional heating.The adsorption of TGOCS for Cr(VI)was systematically studied.2.Materials and methods2.1.MaterialsBiochemical reagent grade chitosan (degree of deacetyla-tion:90%,viscosity average molecular weight:400,000),standard reagent potassium dichromate,analytical grade triethylenete-tramine and graphite were purchased from China National Medicine Corporation Ltd.(Shanghai,China).All other agents were used on analytical grade and all solutions were prepared with dis-tilled water.2.2.PreparationGO was prepared from graphite powder by modified Hum-mers method (Chen,Chen,Bai,&Li,2013;Hummers &Offeman,1958).Graphite (1g),NaNO 3(0.5g)and KMnO 4(3g)were sequen-tially added into the stirred concentrated H 2SO 4solution (23mL)at 277K.After kept at below 293K for 1h,the mixture was vigorously stirred at 308K for 30min and slowly diluted with distilled water (46mL).The reaction temperature was rapidly increased to 371K and kept for 30min.Then,an additional 140mL of water was added,followed by a slow addition of 30%H 2O 2(15mL),turning the color of the solution from brown to yellow.The mixture was purified by centrifuging with 5%HCl and distilled water.The resulting solid (GO)was dispersed in distilled water by ultrasonic treatment for 3h.4g L −1GO aqueous dispersion was prepared by diluting with water and stored for the following preparation.Microwave preparation of TGOCS was done in a modified microwave oven equipped with a stirrer and constant-temperaturecirculating water (Ge &Huang,2010).Triethylenetetramine (5mL)was added to 4g L −1GO aqueous dispersion (50mL)under stirring at room temperature and the pH of the solution was adjusted to 8by adding dilute NaOH solution.The mixture was transferred to the microwave reaction system and was radiated for 15min at 343K under stirring.Then,epichlorohydrin (5mL)and CS (1g)were suc-cessively added and the mixture was radiated for 45min at 343K under stirring.After reaction,the mixture was cooled and filtered.The filter residue was successively washed with 5%HCl,ethanol and distilled water,and dried in vacuum at 333K.(1.37±0.04)g of com-posite was obtained and named as TGOCS.The probable prepared routes were given in Fig.1.As comparison (1.21±0.04)g of composite was prepared by conventional heating and named as C TGOCS.Except for using oil-bath heating instead microwave radiation,all the conditions and processes of the preparation were same as the above microwave preparation.2.3.CharacterizationFourier-transform infrared (FTIR)spectra were recorded on a Bruker FTIR spectrometer (Tensor 27,Germany)using KBr pellets.The morphology was examined by scanning electron microscope (SEM)(LEO 1530VP,Germany).The surface of the sample was coated with gold to be observed and photographed.X-ray diffrac-tion (XRD)patterns were determined with a Rigaku diffractometer (D/max-IIIA,Japan).The specific surface area was measured by N 2adsorption at 77.15K using a Micromeritics surface analyzer (Tri-star 3000,USA).Elemental analysis was done on a Bruker element analyzer (Vario ELCube,Germany).2.4.Adsorption experimentsThe adsorption of Cr(VI)was done using batch method.Batch adsorption experiments were conducted by placing 20mg of adsor-bent with 50mL of Cr(VI)aqueous solutions (200mg L −1)at pH 2in 250mL conical flasks.The flasks were agitated at 180rpm using a mechanical rotary shaker at 303K for 2h to reach adsorption equilibrium.The concentration of Cr(VI)in the solution was deter-mined spectrophotometrically at 540nm using diphenyl carbazide as the complex agent.The adsorption capacities were calculated as follows:q e =(c 0−c e )Vm(1)where q e is the equilibrium adsorption capacity (mg g −1),c 0and c e are the initial and equilibrium concentration of Cr(VI)in the liquid phase (mg L −1),respectively.V is the volume of the solution (L)and m is the mass of adsorbent(g).Fig.1.The probable prepared routes of TGOCS.282H.Ge,Z.Ma/Carbohydrate Polymers131(2015)280–287The initial pH of the solution was adjusted by adding either 0.1mol L−1NaOH or0.1mol L−1HCl.To determine sorption kinet-ics,the initial test solution with pH2was sampled at various time intervals.The adsorption thermodynamics was determined at different temperatures(303K,313K,323K and333K).In order to obtain the adsorption isotherms,solutions with various initial Cr(VI)concentrations(16–206mg g−1)at pH2were treated at 303K.2.5.Regeneration and reuseThe adsorption was done in50mL of200mg L−1Cr(VI)solu-tion at pH2with20mg of TGOCS at303K for2h.Afterfiltration, the TGOCS was immersed in50mL of1mol L−1KOH or HCl aque-ous solution and agitated at303K for2h.Then,the TGOCS was removed from the solution and washed with water.The adsorbent was reused in the next cycle.The adsorption-regeneration cycles were repeated forfive times with the Cr(VI)uptake analysis.3.Results and discussion3.1.CharacterizationThe FTIR spectra of CS,GO,C TGOCS and TGOCS were shown in Fig.2(a).The major bands of CS could be assigned as fol-lows:3419cm−1(–OH and–NH2stretch),2876cm−1(–CH stretch), 1644cm−1(amide band),1617cm−1(–NH2bend),1382cm−1(–CH bend),1105cm−1(C–O stretch),and897cm−1(pyranoid ring stretch)(Ge&Wang,2014).The major bands of GO could be assigned as follows:3431cm−1(–OH stretch),1724cm−1(C O of COOH),1624cm−1(COOH asymmetry stretch)and1401cm−1 (COOH symmetry stretch)(Kumar,Kakan,&Rajesh,2013).For TGOCS and C TGOCS,their spectra were similar and showed the major bands of GO and CS.However,the COOH peak of GO at 1724cm−1and the–NH2group peak of CS at1617cm−1disap-peared and new amide peak at1522cm−1appeared.Hence,the products TGOCS and C TGOCS prepared by microwave and conven-tional methods had similar structures which could be crosslinked by epichlorohydrin with–NH2groups of CS and–NH2groups of graphene oxide-triethylenetetramine monoamide(as shown in Fig.1).The XRD patterns of CS,GO,C TGOCS and TGOCS were depicted in Fig.2(b).The XRD pattern of CS represented the distinct crys-talline peaks at12.8◦and20◦.The distinct crystalline peak of GO appeared at12.4◦.For C TGOCS,the peak at20◦decreased and the peak at about12.8◦became unapparent.For TGOCS,the peaks at 20◦and12.8◦disappeared almost.The crystallinities of GO,CS, C-TGOCS and TGOCS calculated from the peak areas were83.8%, 91.1%,61.4%and50.6%,respectively.The decrease in crystallinity of the composite should be attributed to the deformation of the strong hydrogen bond in original chitosan due to the reaction of amine groups with the grafted GO.This implied that the compos-ites were substantially more amorphous than chitosan and GO and TGOCS was more amorphous than C TGOCS.SEM graphs(20,000×)of CS,GO,C TGOCS and TGOCS were shown in Fig.2(c).The surfaces of CS had some holes and crevasses. The surfaces of GO showed wrinkle fabrics with someflakes.For the composites,their surfaces were similar to those of GO.However, the surfaces of TGOCS had more crevasses than those of C TGOCS.parison of Cr(VI)adsorptionThe adsorption of Cr(VI)on the conventional product C TGOCS, MW product TGOCS and reactants(CS and GO)was conducted by placing20mg of adsorbent in250mL conicalflasks with50mL of200mg L−1Cr(VI)solutions at pH2and303K.The uptake capacities were listed in Table1.The order of capacity was TGOCS>C TGOCS>CS GO.This might be attributed to that the adsorption of Cr(VI)on the adsorbent was partly by the electro-static attraction.At pH2,the amine group existed in the cation and Cr(VI)existed mainly in the HCrO4−anion.The action of active –COOH and–OH groups in GO for Cr(VI)was weak and the action of active amine groups in CS for Cr(VI)was strong.Hence,the capac-ity of CS for Cr(VI)was significantly higher than that of GO.As for TGOCS and C TGOCS,however,the graft of triethylenetetramine increased the amount of amine groups which led to the increase of uptake.The results of elemental analysis and surface area were also summarized in Table1.The N content and surface area of TGOCS were larger than that of C TGOCS.These might be the main rea-son why the uptake of TGOCS was higher than that of C TGOCS. In this preparation,the product obtained by MW had higher yield and uptake than one obtained by the conventional.Hence,the microwave preparation was a better method and adsorption of Cr(VI)on the TGOCS produced by MW was systematically studied in the following.3.3.Microwave mechanism of the preparationBased on the above characteristic results of the products obtained by the microwave and conventional methods,the struc-tures and morphologies of the products were similar.Hence,the probable prepared routes(as showed in Fig.1)should be simi-lar.The higher yield and uptake of the product obtained by the microwave should be related to the interaction of the reactants with microwave.Microwave energy was transferred directly to the reaction mixture,through the molecular dielectric interaction with the electromagneticfield,generating the heat throughout the entire mixture volume simultaneously(Singh,Kumar,&Sanghi, 2012).However,the conventional heating is the heat transfer pro-cess from the outer surface of the mixture to the inner.In our reactive systems,the active groups of reactants such as carboxylic and amine groups were polar.Microwave could interact with these polar groups which might reduce the active energies of reactions (Vergara,de Sarrionandia,Gondra,&Aurrekoetxea,2014).These might led to that the yield and N content of the product obtained by the microwave were higher than by the conventional.The higher N content of the microwave product would be favorable for the uptake of Cr(VI).3.4.Effect of pHThe effect of pH was studied in the pH range of1–7.As shown in Fig.3(a),the pH of solution strongly affected the adsorption performance of TGOCS.The adsorption capacity increased with the increase of the pH value till a maximum value at pH2and then decreased slowly with further increase of pH while decreased markedly with pH>6.This was because Cr(VI)existed mainly in the form of HCrO4−in present study(Hena,2010).In acidic solu-tion,the amine groups of TGOCS could form protonated cations. The extent of protonation of amine group would be reduced with rising pH.The amine group cations in TGOCS would be in favor of forming complexes with Cr(VI)anions by the electrostatic attrac-tion.These resulted in that the adsorption of Cr(VI)on TGOCS hada maximal value at pH2.3.5.Effect of contact time and kinetic studiesAdsorption kinetics was an important constant for the evalua-tion of a good sorbent.As shown in Fig.3(b),the Cr(VI)uptake on TGOCS was rapid in thefirst20min,contributing to about85%ofH.Ge,Z.Ma/Carbohydrate Polymers131(2015)280–287283Fig.2.(a)FT-IR spectra of CS,GO,C TGOCS,TGOCS and TGOCS-Cr(VI);(b)XRD curves of CS,GO,C TGOCS and TGOCS;(c)SEM graphs(20,000×)of CS,GO,C TGOCS and TGOCS.the ultimate adsorption amount for Cr(VI),and then augmented gradually.In present study,the adsorption equilibrium was achieved within about2h.The pseudo-first-order and pseudo-second-order models were used to investigate the adsorption mechanism.The linear forms of pseudo-first-order and the pseudo-second-order equations are expressed as follows(Ge et al.,2012):ln(q e−q t)=ln q e−k1t(2) tq t=1k2q2e+tq e(3) where k1(min−1)and k2(g mg−1min−1)are successively the pseudo-first-order and pseudo-second-order rate constants;q t is the amount adsorbed at time t(min),and q e denotes the amount284H.Ge,Z.Ma /Carbohydrate Polymers 131(2015)280–287Table 1The results of elemental analysis,surface area and uptake capacity of Cr(VI)for CS,GO,C TGOCS and TGOCS.Materialwt (%)Surface area (m 2g −1)q e (mg g −1)CNHCS 40.187.5117.776 6.20131.4GO99.570.0080.04511.95 3.653C TGOCS 36.21 6.0237.52110.58178.8TGOCS34.746.2297.47111.69216.9adsorbed at equilibrium,both in units of mg g −1.The values of k 1and q e (namely q e cal )are calculated from the slope and intercept of the linear fit of ln (q e exp −q t )versus t ,and q e exp is the exper-imental value of q e .The values k 2and q e can be calculated from the linear fit of t /q t versus t .The pseudo-first-order and pseudo-second-order kinetics models were shown in Fig.3(b).The results of kinetic constants and correlation coefficients (R 2)were listed in Table 2.Based on the R 2values and Fig.3(b),the pseudo-second-order model could give the best fit for the experimental data.The results connoted that the adsorption was a chemical process.The intraparticle diffusion model was also selected to fit the kinetic data and it can be formulated as (Ge &Fan,2011):q t =k i t 1/2+C(4)where k i (mg g −1min −1/2)is the intraparticle diffusion rate con-stant and C (mg g −1)is a constant.Values k i and C can be obtained by the linear fit of q t against t 1/2.The intraparticle model kinetics was also shown in Fig.3(b).Taken as a whole,the linear relation of q t versus t 1/2was not good.However,the linear relation was better in the initial 20min of Cr(VI)adsorption,and the constants were also listed in Table 2.The positive value of C indicated that the ini-tial stage of the adsorption process was governed by the boundary layer diffusion (Annadurai,Ling,&Lee,2008).The kinetic plots inFig.3(b)exhibited the two-stage linearity and the latter was the final equilibrium stage where the intraparticle diffusion slowed down.3.6.Effect of initial Cr(VI)concentration and adsorption isothermAdsorption isotherm was important to evaluate the adsorption capacity of TGOCS.Fig.4(a)showed the adsorption equilibrium isotherm of Cr(VI)on TGOCS.Obviously,the uptake of Cr(VI)on TGOCS increased as the initial concentration increased up to 120mg L −1thereafter uptake reached the ngmuir,Freundlich and Temkin isothermic models were used to fur-ther understand the adsorbate–adsorbent ngmuir,Freundlich and Temkin models can be represented as follows (Ge et al.,2012;Kumar et al.,2013):q e =q mK L c e 1+K L c e or c e q e =c e q m +1q m K L,R L =1(1+K L c 0)(5)q e =K F c 1/n eor ln q e =1nln c e +ln K F(6)q e =RT b Tln(K T c e )or q e =RT b Tln(K T )+RT b Tln(c e )(7)where c e (mg L −1)is the equilibrium concentration of adsorbate in solution and q e (mg g −1)is the amount adsorbed at equilibrium.K L (L mg −1)is the Langmuir constant,q m (mg g −1)is the maximum adsorption capacity for monolayer formation on adsorbent,R L is the separation factor.K F (mg g −1(L mg −1)1/n )is a constant represent-ing the sorption capacity and n is a constant depicting the sorption intensity.R (8.315J K −1mol −1)is the universal gas constant,T (K)is the absolute temperature,and b T is related to the heat of adsorp-tion.The Langmuir constants,q m and K L ,could be calculated from the linear fit of c e /q e versus c e .The Freundlich constants,K F and n ,4080120160200q e (m g g -1)pH(a)q (m g g t-1)t (min)(b)Fig.3.(a)The effect of pH on Cr(VI)adsorption by TGOCS;(b)adsorption kinetics of Cr(VI)onto TGOCS.Table 2Constants of kinetic and isotherm models for Cr(VI)adsorption on TGOCS.Kinetic model constantsIsotherm model constantsPseudo-first-orderq e cal (mg g −1)83.59Langmuirq m (mg g −1)219.5k 1(min −1)0.02460K L (L mg −1)0.5524R 20.9522R 20.9997Pseudo-second-orderq e (mg g −1)218.6FreundlichK F (mg g −1(L mg −1)1/n )78.86k 2(g mg −1min −1) 1.103×10−3N 3.939R 20.9996R 20.9178Intraparticle diffusion ak i (mg g −1)42.34Temkinb T (g kJ mg −1mol −1)88.31C (g mg −1min −1)21.34K T (L mg −1)26.52R 20.8796R 20.9828aLinear fitting results at the initial 20min.H.Ge,Z.Ma /Carbohydrate Polymers 131(2015)280–2872854080120160200240q e (m g g -1)c e (mg L -1)(a)q e (m g g -1)Temperat ure (K)(b)Fig.4.(a)Adsorption isotherms of Cr(VI)onto TGOCS;(b)effect of temperature on the adsorption of Cr(VI)by TGOCS.Table 3Adsorption comparison of TGOCS and reported studies on adsorbents for Cr(VI).No.Adsorbentq max (mg g−1)Reference 1TGOCS219.5This work2Cyclodextrin–chitosanmodified GO61.31Li et al.(2013)3Protonated crosslinked chitosan189.3Huang et al.(2013)4Ethylenediamine-modified cross-linked magnetic chitosan51.813Hu et al.(2011)5Cross-linked chitosan86.81Wu et al.(2012)6Ti–CTS171Zhang et al.(2015)7CD-E-MGO68.41Wang et al.(2014)8Chitosan22.09Aydın and Aksoy (2009)9Graphene nanosheets43Jabeen et al.(2011)can be obtained from the linear fit of ln q e versus ln c e .The Temkin constants,K T and b T ,can be obtained from the linear fit of q e versus ln c e .The isotherm constants were summarized in the Table 2and the three models were shown in Fig.4(a).The R 2values (in Table 2)and Fig.4(a)manifested that the Langmuir isotherm could give the best fit for the experimental data.The maximum adsorption capacity of Cr(VI)on the TGOCS from Langmuir model was 219.5mg g −1,which was higher than that of the recently reported adsorbents (listed in Table 3).The R L values were 0.008721–0.09908(0<R L <1),indicating that the adsorption processes were favorable.3.7.Thermodynamic studiesThe influence of temperature for the adsorption of Cr(VI)on TGOCS was given in Fig.4(b).The Cr(VI)uptake increased with increasing temperature.The thermodynamic parameters such as enthalpy change ( H ),entropy change ( S ),and Gibbs functionchange ( G )of the adsorption process were obtained from exper-iments using the following equations (Ge et al.,2012):lnq ec e=S R − H R 1T(8) G = H −T S(9)where q e ,c e ,R and T are the same as indicated above.The S and H values could be calculated from the linear fit of ln(q e /c e )versus 1/T .The calculated values of H and S were 22.02kJ mol −1and 42.26J K −1mol −1,respectively.The positive H indicated an endothermic nature for the adsorption process.The positive S showed the increasing randomness at the solid/liquid interface during the sorption of Cr(VI)onto TGOCS.Meanwhile,the values of G at 303K,313K,323K and 333K were −2.238,−2.761,−3.183and −3.606kJ mol −1,respectively.The negative G revealed the spontaneity of uptake process for Cr (VI).It was noteworthy that the value of H approached the general reaction enthalpy (≥40kJ mol −1)and the value of S was also large (Ge et al.,2012).These meant that the adsorption process should be predominantly chemical.3.8.Effect of adsorbent dosageThe effect of TGOCS dosage on the removal of Cr (VI)was con-ducted in 50mL of Cr (VI)solution with pH 2at 303K for 2h and the result was shown in Fig.5.Obviously,the removal percentage of Cr (VI)increased with the increase of adsorbent dosage.For the initial Cr(VI)concentrations of 80and 200mg L −1,98%removal for Cr(VI)required about 40mg and 100mg of TGOCS,respectively.These results indicated that the Cr(VI)in solution could be effec-tively removed when the dosage of TGOCS was about 10times amount of Cr(VI).3.9.Effect of coexisting ionsBy contacting 20mg of TGOCS with 50mL of Cr (VI)solution (200mg L −1)at pH 2and 303K for 2h,effects of coexisting salts (50mmol L −1of NaCl,KCl or K 2SO 4)were evaluated.The capac-ities in absence of coexisting salt,coexisting NaCl,KCl or K 2SO 4were 213.2,205.8,207.9and 72.27mg g −1,respectively.The result showed that the presence of Na +or K +had no significant effect for the Cr(VI)adsorption.However,SO 42−had greater inhibitory effect than Cl −.This was because the sorbent (TGOCS)had posi-tive charge due to the protonation of amine groups (–NH 3+)in acid solution,causing the electrostatic attractions between anion and286H.Ge,Z.Ma /Carbohydrate Polymers 131(2015)280–287R e m o v a l p e r c e n t a g e (%)Absorbent dos age (m g)Fig.5.The effect of adsorbent dosage on the removal of Cr (VI)by TGOCS.The initialCr(VI)concentration was 80and 200mg L −1,respectively.sorbent.Therefore,the anions such as SO 42−and Cl −in the solution could result in a competitive adsorption with Cr(VI)(mainly in form of HCrO 4−)on the sorbent.In contrast,the electrostatic repulsion could occur between cation (Na +and K +)and the sorbent,leaving the adsorption site of sorbent still available for Cr(VI).3.10.Regeneration of TGOCSThe regeneration and reuse of TGOCS for Cr(VI)removal were also evaluated.1mol L −1NaOH or 1mol L −1HCl was tried to use as a solvent of desorption and the desorption percentages of Cr(VI)on TGOCS were 92.25%and 82.82%,respectively.Hence,1mol L −1NaOH was further selected as a solvent of desorption in adsorp-tion/desorption/regeneration cycles.After five cycles,the uptake of Cr(VI)on TGOCS was still maintained above 80%of initial uptake.This result suggested that TGOCS could be used repeatedly for the treatment of Cr(VI)in wastewater.3.11.Mechanism of Cr(VI)adsorptionFrom the results of the pH and coexisting ion studies,the active groups on the surface of TGOCS composite could be protonated in an acidic medium.The protonated surface had a stronger electrostatic attraction for chromium anions (HCrO 4−).On the other hand,the kinetic and thermodynamic studies indicated that the adsorption on TGOCS was a chemical process.This could be further confirmed by FTIR analysis.The FTIR spectra of TGOCS-Cr(VI)obtained after adsorption of Cr(VI)on TGOCS was also given in Fig.2(a).For com-parison with TGOCS,two new peaks at 930cm −1(Cr O stretch)and 750cm −1(Cr–O stretch)(Kumar et al.,2013)appeared and the peak (N–H and O–H stretch)was shifted from 3417cm −1to 3373cm −1.These indicated that the adsorption of Cr(VI)on TGOCS was a chemical process partly by electrostatic attraction.4.ConclusionsThe triethylenetetramine modified graphene oxide/chitosan composites (TGOCS and C TGOCS)were synthesized by microwave irradiation and conventional heating method.These composites were characterized by FTIR,XRD,SEM,BET and elemental analy-ses.The adsorption of Cr(VI)on these composites were studied and compared.The probable mechanism of the microwave preparation had been discussed.The results indicated that the product obtained by MW had higher yield and uptake than one obtained by the con-ventional.The microwave preparation was a better method than the conventional.The effects of various variables on the adsorptionof Cr(VI)by TGOCS were further discussed.The maximum uptakeof Cr(VI)with 20mg TGOCS at 303K was 219.5mg g −1at pH 2.The adsorption was a fast process which could reach 85%of maximal uptake in 20min.The adsorption followed the pseudo-second-order model and Langmuir isotherm.The Cr(VI)uptake increased with increasing temperature.The adsorption was an endothermic and spontaneous chemical process partly by electrostatic interac-tion.The TGOCS with 10times amount of Cr(VI)could effectively remove the Cr(VI)of solution and the composite could be recycled with 1mol L −1NaOH.Thus the composite may be promising for application in the removal of Cr (VI)from the wastewater.AcknowledgementsThe authors gratefully acknowledge the financial support from the National Nature Science Foundation of China (No.21077034).Additionally,students Na-na Wu and Zhao-xin Wang took part in some work on this research.ReferencesAnnadurai,G.,Ling,L.Y.,&Lee,J.F.(2008).Adsorption of reactive dye from anaqueous solution by chitosan:Isotherm,kinetic and thermodynamic analysis.Journal of Hazardous Materials ,152,337–346.Aydın,Y.A.,&Aksoy,N.D.(2009).Adsorption of chromium on chitosan:Optimiza-tion,kinetics 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大孔树脂吸附分离黑胡萝卜红色素的研究赵昕1，于一帆1，苏婉莹1，阿米娜·艾尔肯1，武敏1，常秀莲1，*，展亚莉2（1.烟台大学生命科学学院，山东烟台264005；2.青岛鹏远康华天然产物有限公司，山东莱西266612）摘要：采用酸性水溶液浸提法提取黑胡萝卜红色素。
用6种大孔树脂（LS-610B 、BM3、D101、LSA-40、AB-8、LSA-305）对粗提液进行初步分离纯化，预选出两种（LS-610B 、BM3）吸附性能较好的树脂，进行了黑胡萝卜红色素的吸附等温线和静态吸附/解吸动力学实验研究。
研究结果表明，树脂吸附的最适宜的料液pH 值为2.0；LS-610B 树脂适合Langmuir 模型和Freundlich 模型拟合，相关系数分别为0.9799和0.9740；BM3树脂更适合Langmuir 模型拟合，相关系数为0.9662，属于单分子层吸附机理；这两种树脂的吸附过程特征都能用拟一阶动力学模型能很好地描述，主要因素是内外膜扩散影响吸附的；最佳解吸条件为65%乙醇水溶液（含0.3%的柠檬酸）。
关键词：大孔树脂；黑胡萝卜红色素；吸附；解吸；分离纯化Study on Adsorption and Separation of Red Color from Daucus carota L.by Macroporous Resins ZHAO Xin 1，YU Yi-fan 1，SU Wan-ying 1，ERKEN A-mina 1，WU Min 1，CHANG Xiu-lian 1，*，ZHAN Ya-li 2（1.School of Life Sciences ，Yantai University ，Yantai 264005，Shandong ，China ；2.Qingdao PengyuanKanghua Natural Products Co.，Ltd.，Laixi 266612，Shandong ，China ）Abstract ：Acidic aqueous solution was used as the extractant for the extraction of red color from black carrot.Adsorption of black carrot red color onto six macroporous resins （LS-610B ，BM3，D101，LSA-40，AB-8，LSA-305）was screened to develop a potential approach for large-scale production of black carrot red color ，and two promising resins （LS-610B ，BM3）were selected for the following static and dynamic adsorption/desorption ex -periments.Results showed that the optimal adsorption pH of the extracted solution was 2.0，the adsorption data of resin LS-610B could be well fitted both by Langmuir and Freundlich equations ，with correlated coefficient of 0.9799and 0.9740，respectively.The adsorption data of resin BM3could be better fitted by Langmuir equa -tion ，with correlated coefficient of 0.9662，exhibiting mono -layer adsorption mechanism ，and them pseudo first-order model could describe the dynamic model better for the two resins ，internal and external diffusioncontrolling the adsorption rate.The optimal desorption condition was 65%ethanol aqueous solution containing 0.3%citric acid.Key words ：macroporous resin ；black carrot red color ；adsorption ；desorption ；separation and purification食品研究与开发F ood Research And Development圆园17年12月第38卷第23期DOI ：10.3969/j.issn.1005-6521.2017.23.007基金项目：国家级星火计划项目（2014GA741008）；烟台大学研究生科技创新基金（YDYB1716）；烟台大学开放实验室作者简介：赵昕（1991—），女（汉），硕士研究生，研究方向：天然产物的分离提取。
ReviewRemoval of heavy metal ions from wastewater by chemicallymodified plant wastes as adsorbents:A reviewW.S.Wan Ngah *,M.A.K.M.HanafiahSchool of Chemical Sciences,Universiti Sains Malaysia,11800Penang,Malaysia Received 3April 2007;received in revised form 18June 2007;accepted 18June 2007Available online 27July 2007AbstractThe 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 affected upon chemical treatment.In general,chemically modified plant wastes exhibit higher adsorption capacities than unmodified forms.Numerous chemicals have been used for modifications 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 treatment1.IntroductionHeavy 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 refining,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-troflotation,membrane separation,reverse osmosis,elec-trodialysis,solvent extraction,etc.(Namasivayam andRanganathan,1995)are attracting attention of scientists.Adsorption is one the physico-chemical treatment pro-cesses found to be effective 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 (Hanafiah et al.,2007),rubber (Hevea brasili-ensis )leaf powder (Hanafiah 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-0960-8524/$-see front matter Ó2007Elsevier Ltd.All rights reserved.doi:10.1016/j.biortech.2007.06.011*Corresponding author.Tel.:+6046533888;fax:+6046574854.E-mail address:wsaime@usm.my (W.S.Wan Ngah).Available online at Bioresource Technology 99(2008)3935–3948cessing,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 modified 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-ification were discussed.A comparison of adsorption effi-ciency between chemically modified and unmodified adsorbents was also reported.2.Chemically modified plant wastesPretreatment of plant wastes can extract soluble organic compounds and enhance chelating efficiency(Gaballah et al.,1997).Pretreatment methods using different 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 efficiency of metal adsorption have been performed by many research-ers(Hanafiah 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 hullsRice 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 modified using different modification 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 modified or treated rice husk exhibited higher adsorption capacities on heavy metal ions than unmodified 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 unmodified 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 modified 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-ified rice husk.Esterified tartaric acid modified rice husk however significantly reduced the uptake of Cu and Pb. The maximum adsorption capacities for Pb and Cu were reported as108and29mg gÀ1,respectively.Effect of che-lators on the uptake of Pb by tartaric acid modified 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 significant suppressing effect on the uptake of Pb.Dyestufftreated 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%of3936W.S.Wan Ngah,M.A.K.M.Hanafiah/Bioresource Technology99(2008)3935–3948W.S.Wan Ngah,M.A.K.M.Hanafiah/Bioresource Technology99(2008)3935–39483937 Table1Summary of modified plant wastes as adsorbents for the removal of heavy metal ions from aqueous solutionAdsorbent Modifying agent(s)Heavy metal Q max(mg gÀ1)SourceRice husk Water washed Cd(II)8.58Kumar and Bandyopadhyay(2006) Sodium hydroxide20.24Sodium bicarbonate16.18Epichlorohydrin11.12Rice husk Tartaric acid Cu(II)31.85Wong et al.(2003b)Pb(II)120.48Sawdust(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)15.8Sawdust(Fir tree)Cu(II)12.7Zn(II)13.4Sawdust(Oak tree)Hydrochloric acid Cu(II) 3.60Argun et al.(2007)Ni(II) 3.37Cr(VI) 1.74Sawdust(Pinus sylvestris)Formaldehyde in Sulfuric acid Pb(II)9.78Taty-Costodes et al.(2003)Cd(II)9.29Walnut sawdust Formaldehyde in sulfuric acid Cd(II) 4.51Bulut and Tez(2003)Ni(II) 6.43Pb(II) 4.48Sawdust Reactive Orange13Cu(II)8.07Shukla and Pai(2005b)Ni(II)9.87Zn(II)17.09Peanut husk Sulfuric acid Pb(II)29.14Li et al.(2006a)Cr(III)7.67Cu(II)10.15Cr(VI)11.4Dubey and Gopal(2006) Groundnut husk Sulfuric acid followed by silverimpregnationCassava 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)90.9Zn(II)83.3Wheat bran Sulfuric acid Cu(II)51.5O¨zer et al.(2004)Wheat bran Sulfuric acid Cd(II)101O¨zer and Pirinc¸c¸i(2006)Juniperfibre Sodium hydroxide Cd(II)29.54Min et al.(2004)Indian barks Hydrochloric acid Cu(II)Reddy et al.(1997)–sal51.4–mango42.6–jackfruit17.4Jutefibres Reactive Orange13Cu(II)8.40Shukla and Pai(2005a)Ni(II) 5.26Zn(II) 5.95Hydrogen peroxide Cu(II)7.73Ni(II) 5.57Zn(II)8.02Unmodified Cu(II) 4.23Ni(II) 3.37Zn(II) 3.55Banana 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 grainSpent 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)SourceCork powder Calcium chloride Cu(II)15.6Chubar et al.(2004)Sodium chloride19.5Sodium hydroxide18.8Sodium hypochlorite18.0Sodium iodate19.0Corncorb Nitric acid Cd(II)19.3Leyva-Ramos et al.(2005)Citric acid55.2Imperata cylindrica leaf powder Sodium hydroxide Pb(II)13.50Hanafiah et al.(2006a) Alfalfa biomass Sodium hydroxide Pb(II)89.2Tiemann et al.(2002)Azollafiliculoides (aquatic fern)Hydrogen peroxide–MagnesiumchloridePb(II)228Ganji et al.(2005)Cd(II)86Cu(II)62Zn(II)48Carrot residues Hydrochloric acid Cr(III)45.09Nasernejad et al.(2005)Cu(II)32.74Zn(II)29.61Sugarcane bagasse Sodium bicarbonate Cu(II)114Junior et al.(2006)Pb(II)196Cd(II)189Ethylenediamine Cu(II)139Pb(II)164Cd(II)189Triethylenetetramine Cu(II)133Pb(II)313Cd(II)313Sugarbeet pulp Hydrochloric acid Cu(II)0.15Pehlivan et al.(2006)Zn(II)0.18Bagassefly ash Hydrogen peroxide Pb(II) 2.50Gupta and Ali(2004)Cr(III) 4.35Nipah palm shoot biomass Mercaptoacetic acid Pb(II)52.86Wankasi et al.(2006)Cu(II)66.71Groundnut shells Reactive Orange13Cu(II)7.60Shukla and Pai(2005b)Ni(II)7.49Zn(II)9.57Terminalia 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.Hanafiah/Bioresource Technology99(2008)3935–3948rium 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 effect of organic ligands (EDTA,nitrilotriacetic acid and salicylic acid)on adsorp-tion efficiency 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 affect adsorption of lead.2.3.Sugarcane bagasse/fly ashJunior et al.(2006)reported the use of succinic anhy-dride modified 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 modified 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 different chemicals mainly NaHCO3,ethylenediamine and triethylenetetramine to produce new properties of adsorbent materials which showed different 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 modified sugarcane bagasse has a higher increasing extent. The presence of amide group was also detected in ethylene-diamine and triethylenetetramine modified 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 modified sugarcane bagasses were slower than that for adsorbent modified with NaHCO3. Triethylenetetramine modified 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 unmodified sugarcane bagasse.This was prob-ably caused by the higher number of nucleophilic sites introduced in triethylenetetramine modified sugarcane bagasse.When sugarcane bagasse was modified 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 fly 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 bagassefly 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 bagassefly ash was not discussed,but it was thought that adsorption was controlled byfilm diffusion at lower metal concentra-tion and particle diffusion at higher concentration of metal ions.2.4.SawdustSawdust,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 different mechanisms.An experiment on the efficiency of sawdust in the removal of Cu2+and Zn2+ions was conducted by Sˇc´i-ban et al.(2006a).Two kinds of sawdust,poplar andfir wood were treated with NaOH(fibre-swelling agent)and Na2CO3solutions and the adsorption capacities were com-pared with the untreated sawdusts.For unmodified 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 different 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(fir saw-dust)for Cu2+,and15.83mg gÀ1(poplar sawdust)and 13.41mg gÀ1for Zn2+(fir 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 modification purpose how-ever did not cause a significant increase of the adsorption capacity.The authors suggest that no greater than1%of concentration of NaOH solution should be used for mod-ification.The temperature of modification was also not a significant factor for the main increase of adsorption capacities of modified sawdusts.It was observed that only a slight increase in Cu2+and Zn2+adsorption occurred when thefir sawdust was treated with NaOH at higher tem-perature(80°C).The study on adsorption capacity byW.S.Wan Ngah,M.A.K.M.Hanafiah/Bioresource Technology99(2008)3935–39483939treatment with Na2CO3revealed the modified sawdusts had two times higher adsorption for Cu2+ions and six times higher for Zn2+ions compared to unmodified saw-dusts.The application of Na2CO3for chemical modifica-tion is less efficient 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 modification. (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 effect 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 thefirst 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 efficiency 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 detergentfibre(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 tofilter 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 was73.62mg gÀ1.A detail analysis on the ideal concentration of NaOH for modifying juniperfibre 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 saponification or the conversion of an ester group to carboxylate and alco-hol,as shown in the equation below:RCOOR0þH2O!OHÀRCOOÀþR0OHð1ÞBased 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 saponification process.After base treatment,the max-imum adsorption capacity of cadmium increased by about three times(from9.18to29.54mg gÀ1)compared to un-treated juniperfibre despite a decrease in specific surface area for the treated adsorbent.Data obtained from pseu-do-second-order kinetic study also revealed that base trea-ted juniperfibre 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.Hanafiah/Bioresource Technology99(2008)3935–39482004).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 affected 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 significantly 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 withfixed 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-terfitted than pseudo-first-order and intraparticle diffusion 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-first-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 modified cork powder shows greater adsorption capacity than the unmodified 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 different 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,modification 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 branWheat 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 significant effect on the surface area of the adsorbent,which eventually results in better efficiency 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 adsorptionfitted 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.Hanafiah/Bioresource Technology99(2008)3935–39483941。
