Chitosan/modi ?ed montmorillonite beads and adsorption Reactive Red 120
Siriwan Kittinaovarat ?,Panida Kansomwan,Nantana Jiratumnukul
Department of Materials Science,Faculty of Science,Chulalongkorn University,Bangkok 10330,Thailand
a b s t r a c t
a r t i c l e i n f o Article history:
Received 10July 2009
Received in revised form 18December 2009Accepted 18December 2009Available online 4January 2010Keywords:Chitosan
Montmorillonite Dye adsorption
Different molar mass (―Mw )chitosans were prepared by the hydrolysis of commercial ―
Mw 480,000chitosan (CTS 480)with hydrogen peroxide at 4%(v/v)for 6and 24h and at 15%(v/v)for 24h,yielding new smaller
polymers of ―
Mw 130,000(CTS 130),69,000(CTS 69)and 14,000(CTS 14),respectively.The four chitosan preparations were used to modify montmorillonite (MMT),but all only slightly increased the basal spacing.In contrast,intercalation of octadecylamine at a 2:5(m/m)ratio of octadecylamine:MMT signi ?cantly increased the basal spacing.Therefore,octadecylamine was added to enhance the layer separation.The CTS 69chitosan preparation yielded the highest basal spacing.This mMMT (MMT:octadecylamine:CTS 69=5:2:5(m/m/m),respectively),was then used to prepare CTS 480:mMMT composite beads with different mass ratios of CTS 480to mMMT,which were then evaluated as an adsorbent of Reactive Red 120.Three factors,(i)pH of dye solution in the range of 4–6,(ii)increasing the mMMT ratio and (iii)the amount of adsorbent to dye ratio,improved the adsorption ef ?ciency.The adsorption isotherm of 1:1(m/m)CTS 480:mMMT composite beads agreed well with the Langmuir model.
?2009Elsevier B.V.All rights reserved.
1.Introduction
Chitosan is a polysaccharide based polymer (β-(1–4)-linked D -glucosamine with varying amounts of N-acetyl-D -glucosamine depending upon the degree of deacetylation)obtained from the deacetylation of chitin,which makes up the exoskeletons (shells)of crustaceans such as crabs and shrimps.Moreover,chitin is the second most plentiful natural polymer after cellulose and is a waste product from the crustacean-based food industry,making chitosan economi-cally attractive since it is cheap,plentiful and does not compete for human food resources.Chitosan has many interesting characteristics such as hydrophilicity,biocompatibility,biodegradability,antibacteri-al properties,and ?occulating regeneration ability.These properties of chitosan have led to its diverse applications and increasing research into new application areas.One such example is that chitosan has been regarded as a useful material to remove transition metal ions and organic substances from waste water because the amino and hydroxyl groups on chitosan chains serve as binding sites (Bekci et al.,2008;Chen et al.,2007;Hasan et al.,2007).Azo dyes account for some 60–70%of dyes used in the textile industry (Muruganandham and Swaminathan,2004),and include the reactive acid dyes which are highly water soluble and thus problematic to remove from textile waste water by traditional ?occulation,coagulation and activated sludge methods,leading to the development of new techniques for
their removal such as electrooxidation and photocatalytic oxidation (Aplin and Waite,2000;Moraes et al.,2000;Gurses et al.,2002).However,these processes have considerable energy requirements and thus impose both economic and environmental costs,and so alternative simple methods to work alongside these are sought.Taking advantage of the water soluble and charged nature of reactive azo dyes is the idea of developing improved,rechargeable,composite adsor-bents based upon readily available cheap and non-toxic constituents such as clays and biopolymers like chitosan.
Clay minerals are potential adsorbents.Montmorillonite (MMT)has a large speci ?c surface area and a high cation exchange capacity.The effects of different mass ratios of chitosan to mMMT,pH and reaction time on the adsorption of a reactive dye were evaluated.2.Experimental 2.1.Materials
Commercial grade high molar mass chitosan with a molar mass of 480K and a 90%degree of deacetylation,(CTS 480),was supplied from Bio-Line Co.,Ltd.Glacial acetic acid was purchased from Mallinckrodt Baker.,Inc.Hydrogen peroxide 50%(v/v)(H 2O 2),purchased from Thai Peroxide Co.,Ltd.,was used to hydrolyze chitosan.Sodium montmo-rillonite with a cation exchange capacity (CEC)of 50meq/100g and a speci ?c density of 2.3–2.4and moisture content of 8–12%was obtained from the Thai Nippon Chemical Industry Co.,Ltd.Octadecy-lamine (C 18H 39N)was purchased from Fluka Chemika.The Reactive Red 120dye (Fig.1)was supplied from Dystar Co.,Ltd.
Applied Clay Science 48(2010)87–91
?Corresponding author.Tel.:+6622185551;fax:+6622185561.E-mail address:ksiriwan@sc.chula.ac.th (S.
Kittinaovarat).0169-1317/$–see front matter ?2009Elsevier B.V.All rights reserved.doi:
10.1016/j.clay.2009.12.017
Contents lists available at ScienceDirect
Applied Clay Science
j o u r n a l h o me p a g e :w w w.e l sev i e r.c om /l o c a t e /c l ay
2.2.Preparation of hydrolyzed chitosan
Five grams of high molar mass chitosan(CTS480)was hydrolyzed by100ml of H2O2solution at room temperature with two different H2O2concentrations(4%and15%(v/v))for either6or24h.After the reaction,each sample was?ltered,washed with distilled water until the?ltrate was neutral and then dried at50°C for12h.
2.3.Modi?cation of MMT with chitosans
An aqueous solution of CTS480was prepared by dissolving2g of CTS480in50ml of distilled water containing1ml of conc.HCl and stirred with a magnetic stirrer until the chitosan was completely dissolved.MMT(2.5g)was dispersed in50ml of distilled water and stirred for20min.The chitosan solution was then added to the MMT dispersion and the mixture was stirred at2000rpm for1h to separate the MMT–chitosan complex from the solution.The precipitate was washed with distilled water and then dried at70°C for24h prior to being ground and sieved through a200mesh Sieve.In addition to CTS480,the three hydrolyzed chitosans,CTS130,CTS69and CTS14(see Table1),were used to modify MMT using the same procedure.
2.4.Modi?cation of MMT with octadecylamine
One gram of octadecylamine was dissolved in30ml of distilled water and then1ml of conc.HCl was added to this solution and stirred at80°C for20min.MMT(2.5g)was dispersed in70ml of distilled water by stirring for20min prior to addition of the octadecylamine solution and stirring at2000rpm for1h.The dispersion was then?ltered and washed with distilled water until the?ltrate was neutral and then dried in the oven at70°C for24h, prior to milling and then sieved through a200mesh sieve.
2.5.Modi?cation of MMT with octadecylamine and different molar mass chitosans
We used two methods to modify MMT with octadecylamine and chitosan.The?rst method was a simultaneous modi?cation,whilst the second was a two-step modi?cation?rst by octadecylamine and then by chitosan.Each of the four chitosan preparations were made as aqueous solutions by dissolving1g of each molar mass chitosan in 30ml of distilled water containing0.5ml of conc.HCl by stirring until the chitosan was completely dissolved.The octadecylamine solution was prepared by dissolving1g of octadecylamine with0.5ml of conc. HCl in30ml of distilled water and stirring at80°C for20min.MMT (2.5g)was dispersed in40ml of distilled water by stirring for20min. For the simultaneous modi?cation of MMT,both the chitosan and octadecylamine solutions were simultaneously added into the MMT dispersion and stirred at2000rpm for1h.For the two-step modi?cation,the octadecylamine solution was?rst added to the MMT dispersion and stirred at2000rpm for30min,and then the chitosan solution was added,stirred at2000rpm for30min,and separated by centrifugation.In both cases the precipitate containing the MMT–chitosan–octadecylamine(mMMT)was washed with distilled water and dried at70°C for24h prior to milling and then passed through a200mesh sieve.
2.6.Preparation of chitosan beads
Two grams of chitosan?akes(CTS480)was dissolved in48ml of water with2ml of glacial acetic acid with stirring until the chitosan had completely dissolved.The viscous solution was then dropped into neutralization solution(9:1(v/v)mix of8%(m/v)NaOH and ethanol) and left for one day to form chitosan beads.The beads were then washed with deionized water until the wash solution become neutral, and stored in distilled water before use.
2.7.Preparation of chitosan/mMMT beads
Chitosan/mMMT beads were formed as per mMMT(Section2.5) and chitosan beads(Section2.6above),except that the CTS480added was adjusted to take account of the amount of CTS x present in the mMMT such that the total of both equaled2g;and was used at chitosan:mMMT mass ratios of9:1,7:3and1:1.
2.8.Characterization
The molar mass of chitosan was characterized by Gel Permeation Chromatography(Waters,Water600E).Small-angle X-ray diffraction (XRD)patterns of the modi?ed MMT were performed using a Bruker AXS Model D8diffractometer at40kV and40mA,a scan range2θequal to0–15°,and a scan rate of
0.2°/min.
Fig.1.Structure of Reactive Red120.
Table1
Molar mass and polydispersity of hydrolyzed chitosans.
Hydrolysis conditions Label ―
Mn
―
Mw Polydispersity
No treatment CTS480100,000480 4.8 4%(v/v)H2O2for6h CTS13029,000130 4.5 4%(v/v)H2O2for24h CTS6922,00069 3.1 15%(v/v)H2O2for24h CTS14790014
1.8Fig.
2.XRD powder patterns of(a)original MMT and mMMT–chitosan complexes with (b)CTS480,(c)CTS130,(d),CTS69and(e)CTS14.
88S.Kittinaovarat et al./Applied Clay Science48(2010)87–91
2.9.Adsorption procedure
Reactive Red 120was dissolved in distilled water to 50mg/l,pH was adjusted by adding a few drops of dilute 0.1%(m/v)NaOH or 0.1%(v/v)HCl as appropriate.To each 50ml Reactive Red 120dye solution (50ml),1g of adsorbent beads (0.05g dry basis)was added and shaken for 8h at 120rpm and 30°C.Preliminary studies showed that the dye adsorption was completed within 8h.An aliquot was taken every hour and spectrophotometrically analyzed at 534nm by an UV/Visible spectrometer (Specord S 100).Each experiment was repeated ?ve times under the same controlled conditions.
2.10.Adsorption isotherms
Adsorption isotherms were performed as in Section 2.9except that 50ml solutions of Reactive Red 120dye were used at initial concen-trations of 60,80,100,120and 140mg/l.The amounts adsorbed were derived from the concentration changes.3.Results and discussion
3.1.Characterization of hydrolyzed chitosan
The average molar mass and polydispersity of hydrolyzed chitosans were characterized by GPC (Table 1).The higher concentration of H 2O 2and the longer reaction time both provided a lower molar mass of hydrolyzed chitosan,and so 15%(v/v)H 2O 2for 24h provided the
lowest ―Mw and ―
Mn ,and also polydispersity of hydrolyzed chitosan.3.2.Interlayer separation of MMT in the presence of hydrolyzed chitosans and octadecylamine
The typical re ?ection of MMT in Fig.2(line a)was 7.02°,corresponding to a basal spacing of 12.6?.After modi ?cation of MMT with each hydrolyzed chitosan,the re ?ection of the original MMT at 2θ=7.02°disappeared and was substituted by a new re ?ec-tion at around 2θ=5.66°,corresponding to a basal spacing of 15.6?for MMT –chitosan complexes with CTS 480,CTS 130and CTS 69,whilst the MMT –CTS 14complex showed a basal spacing of 16.2?.In the presence of octadecylamine (Fig.3),the basal spacing increased to 34.9?(line b).Octadecylamine was combined with the different chitosan preparations enlarging the interlayer separation of MMT.
3.3.The effect of the way of modi ?cation
The results of XRD analysis in Fig.4revealed that the simultaneous modi ?cation and the two-step modi ?cation of MMT led to the same basal spacing.The increase of the basal spacing might be indicative of the formation of an intercalated mMMT by both of modi ?cation processes.Therefore,the simultaneous modi ?cation of MMT by octadecylamine and chitosan (5:2:5(m/m/m))was chosen as the method for MMT modi ?cation throughout this study.
3.4.The effect of the simultaneous modi ?cation of MMT with octadecylamine and different molar mass hydrolyzed chitosans on the MMT interlayer separation
The results of XRD patterns are summarized in Fig.5.The basal spacing of MMT was increased to 35.6,36.0,and 36.0?when using CTS 480,CTS 130and CTS 69.In the case of the simultaneous modi ?cation with octadecylamine and CTS 69(line d)the re ?ection of MMT almost disappeared indicating highly disordered intercalated or nearly exfoliated MMT particles.However,the simultaneous modi ?
cation
Fig.3.XRD powder patterns of (a)MMT and (b)MMT modi ?ed with 40%(m/m)
octadecylamine.Fig.4.XRD powder patterns of mMMT (MMT:octadecylamine:CTS 480=5:2:5(m/m/m))after (a)the simultaneous modi ?cation and (b)the two-step modi ?
cation.
Fig.5.XRD powder patterns of (a)MMT and mMMT (MMT:octadecylamine:CTS x =5:2:5(m/m/m))with (b)CTS 480,(c)CTS 130,(d)CTS 69and (e)CTS 14.
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S.Kittinaovarat et al./Applied Clay Science 48(2010)87–91
with octadecylamine and CTS 14under otherwise the same conditions (line e)shifted the MMT re ?ection to a higher angle indicating that the small polymer chains of CTS 14had a lower ability to separate the MMT layers than that of the larger sized chitosans.Thus,mMMT formed by the simultaneous modi ?cation of MMT with octadecyla-mine and CTS 69provided the highest disordered intercalated or nearly exfoliated MMT particles and was,therefore,used to form composite beads with CTS 480.
3.5.Adsorption of Reactive Red by chitosan/mMMT beads
The adsorption rate and the removal of Reactive Red increased with increasing time during 8h (Fig.6).At this (equilibrium)time the maximum adsorption capacity of the three adsorbents was obtained.Both the CTS 480/MMT and CTS 480/mMMT beads provided a faster adsorption rate than that of pure chitosan beads.Adsorption at equilibrium was similar between the CTS 480/MMT and CTS 480/mMMT beads.The CTS 480/mMMT beads which provided the highest adsorp-tion rate was due to the enlarged basal spacing.Since the adsorption rate of the CTS 480/mMMT was the highest amongst the three adsorbents tested,these composite beads were used for studying the effect of different mass ratios of CTS 480to mMMT,the initial pH and the amount of adsorbent on the Reactive Red adsorption.3.6.The effect of the mass ratio of chitosan to mMMT on the dye adsorption Increasing the mass ratio of mMMT in the CTS 480/mMMT beads enhanced the adsorption of the reactive dye (Fig.7).Increasing the amounts of mMMT,more spaces (and so increased diffusion rates)and surface areas (and thus binding sites)were made available.However,the mass ratio of mMMT N 50%(m/m)in the CTS 480/mMMT mixture could not form stable composite beads (data not shown).
3.7.The effect of the initial pH on the dye adsorption
Dye uptake was higher in slightly acidic solutions (pH 4–5,optimal at pH 5)than in alkaline solution (Fig.8).At a lower pH,more amino groups of chitosan molecules (pKa ～6.5dependent upon the degree of deacetylation)were protonated,thereby increasing the electrostatic attraction between the negatively charged dye anions and the positively charged adsorption sites.Similar results were reported by Chiou and Li (2003)for the adsorption of RR 189on crosslinked chitosan beads and by Hasan et al.(2007)for crosslinked chitosan/oil palm.3.8.The effect of the amount of adsorbent on the dye adsorption Increasing the amount of adsorbent of 1:1(m/m)CTS 480:mMMT beads increased the adsorption rate and dye removal (Fig.9).At a higher dose of absorbent the time required to reach equilibrium was reduced,requiring,for example,only 4h with 2and 3g absorbent compared to over 8h with only 0.5and 1g absorbent.3.9.Adsorption isotherms
The linear form of the Langmuir isotherm is expressed as:q e =X m bC e =e1+bC e T
where q e is the amount of dye adsorbed per unit mass of adsorbent (mg/g)and C e is the equilibrium concentration of dye in solution (mg/l).The constant X m is the monolayer adsorption capacity (mg/g)and b is the Langmuir constant.
The Langmuir isotherms of CTS 480and 1:1(m/m)CTS 480:mMMT beads are shown in Fig.10for CTS 480and 1:1(m/m)CTS 480:mMMT beads,the absorption capacity (X m ),and the Langmuir constant derived from the linear regression plots are shown in Table 2
.
Fig.6.Dye removal;experimental conditions were 50mg/l of Reactive Red 120,pH 7,30°C and 1g of adsorbent (0.05g dry basis)in a total volume of 50
ml.
Fig.7.The effect of the mass ratio of chitosan to mMMT on the dye adsorption rate and dye removal;experimental conditions were 50mg/l of Reactive Red 120,pH 7,30°C,1g of adsorbent (0.05g dry basis)in a total volume of 50ml.MMT:octadecylamine:CTS 69=5:2:5
(m/m/m).Fig.8.The effect of pH on the dye adsorption rate after 6h;experimental conditions were of 50mg/l of Reactive Red 120,6h,1g of adsorbent (0.05g dry basis)of composite beads composed of 1:1(m/m)CTS 480/mMMT beads in a total volume of 50ml.MMT:octadecylamine:CTS 69=5:2:5
(m/m/m).
Fig.9.The effect of the amount of adsorbent on the dye adsorption rate;experimental conditions were 50mg/l of Reactive Red 120,30°C,pH 5,the indicated wet mass (1g wet mass equates to 0.05g dry mass)of composite 1:1(m/m)CTS 480/mMMT beads in a total volume of 50ml.MMT:octadecylamine:CTS 69=5:2:5(m/m/m).
90S.Kittinaovarat et al./Applied Clay Science 48(2010)87–91
The adsorption isotherms of CTS 480and 1:1(m/m)CTS 480:mMMT beads could be described very well by the Langmuir equation.The 1:1(m/m)CTS 480:mMMT beads had a higher adsorption capacity (X m =5.61)than that of CTS 480(X m =4.43).4.Conclusion
The aim of this study was to investigate the effect of chitosan with different polymer chain lengths (molar mass)on the interlayer separation of MMT to design dye adsorbents,for example,for textile industry waste water puri ?cation.Only the smaller sized chitosan did slightly enlarge the interlayer separation.Octadecylamine enhanced the interlayer separation of MMT much better,at least at 40%(m/m).Octadecylamine added together with hydrolyzed chitosan in the simultaneous procedure or in the two-step procedure improved the ability of chitosan to separate the MMT layers.The simultaneous modi ?cation of MMT with octadecylamine (mMMT)and the different chitosans in the mass ratios 5:2:5led to the formation of intercalated or exfoliated MMT particles.CTS 69imparted the highest basal spacing.Thus,mMMT (MMT:octadecylamine:CTS 69=5:2:5(m/m/m))was
used to form composite beads with CTS 480as an adsorbent for the water soluble reactive azo dyes.The dye adsorption rate and capacity depended on the mass ratio of CTS 480to mMMT,with increasing adsorption rates as the ratio of mMMT increased.The optimum pH for the dye adsorption was pH 5,where most of the chitosan amino groups (pKa ～6.5)were protonated.The adsorption capacity in-creased with increasing amounts of adsorbent under these conditions.The adsorption isotherm of 1:1(m/m)CTS 480:mMMT beads followed the Langmuir isotherm model very well.Acknowledgments
The authors acknowledge the CU Graduate School Thesis Grant from Chulalongkorn University,and thank Bio-Line Co.,Ltd.,for supplying chitosan,and the Thai Nippon Chemical Industry Cp.,Ltd.,for providing montmorillonite.References
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Fig.10.The Langmuir adsorption isotherm of CTS 480and 1:1(m/m)CTS 480/mMMT beads for Reactive Red 120dye.MMT:octadecylamine:CTS 69=5:2:5(m/m/m).The lines were the best ?t linear regression lines.
Table 2
Parameters of the Langmuir isotherm and the relative correlation coef ?cients for non-hydrolyzed chitosan (CTS 480),CTS 480:mMMT =1:1.The data were derived from ?ve repetitions.MMT:octadecylamine:CTS 69=5:2:5(m/m/m).Type of adsorbent
Langmuir equation
C e /q e =(1/bX m )+(C e /X m )X m (mg/g)
b R 2CTS 480
4.43260.03750.9283CTS 480/mMMT composite
5.6085
0.0595
0.9873
91
S.Kittinaovarat et al./Applied Clay Science 48(2010)87–91
壳聚糖抑菌性能研究 甲壳素－壳聚糖是一种极有前途的天然高分子聚合物，自20世纪60年代以来，人们对它们的研究、生产、应用变得十分活跃。特别是近几年，研究人员认识到它们的抑菌效能，通过深入研究，有些甲壳素 －壳聚糖的抑菌产品已经问世。 甲壳素脱乙酰基产物为壳聚糖。据研究，壳聚糖的抑菌作用可能有两种机理，一种是壳聚糖通过正电荷的－NH3吸附带负电荷的细胞壁，使壳聚糖吸附在细胞膜表面形成一层高分子膜，改变了细胞膜的选择透过性，阻止营养物质向细胞内的运输，致使细胞质流失、细胞质壁分离，从而起到抑菌杀菌作用；另外一种机理是壳聚糖通过渗入进细胞体内，吸附细胞体内带有阴离子的细胞质，并发生絮凝作用扰乱细胞正常的生理活动，从而杀灭细菌。近几年，随着对该特性认识的加深，人们不仅对能够影响其抑菌性能的机理进行了深入的研究，而且，也开始应用化学方法对其进行改性，从而提高壳聚糖的抑菌性能，最终达到扩大其应用范围的目的。目前，针对影响壳聚糖抑菌性能方面的研究主要有以下几个方面：分子量对壳聚糖抑菌性能的影响多数研究认为，寡聚糖和低分子量的壳聚糖的抑菌效果较好，随分子量上升效果逐渐下降。特别是对大肠杆菌，壳聚糖分子量越小，抑菌作用愈明显。例如：宋献周等就几种不同分子量的α－壳聚糖对几种常见菌（大肠杆菌、金黄色葡萄球菌、枯草杆菌、产气荚膜杆菌）的抑制研究表明，低分子量的α－壳聚糖的抑菌效果优于高分子量的α－壳聚糖。夏文水等采用E．coli作为试验菌株，测得分子量为1500的壳低聚糖抑菌效果最强。但是，也有一些研究利用不同的试验菌得出结论认为，壳聚糖分子量较大时，其抑菌能力更强。例如：Yousook等报导分子量为4万的壳聚糖在浓度为0．5％时，对S．taureus 和E．coli的杀灭率为90％：分子量为18万的壳聚糖在浓度为500PPM时，对S．taureus和E．coli的杀灭率为100％：分子量在30万以下时，壳聚糖对金黄色葡萄球菌的抑制作用随分子量减小而逐渐减弱。 pH值对壳聚糖抑菌性能的影响 严钦等人研究认为，壳聚糖因为具有质子化铵，能与细菌大负电荷的细胞膜作用，干扰细菌细胞膜功能，造成细菌体内细胞质流失，扰乱细胞的正常生理代谢，从而达到杀菌的目的。而在pH为中性时，壳寡糖中的氨基没有被质子化，因而不能抑制细胞的生长，反而是作为一种糖被细菌利用。由此可见，通常在微酸条件下，壳聚糖具有明显的抑菌作用，但是当pH值为7时，壳聚糖不但没有抑菌效果，反而还有一定的促进细菌生长的作用。晶体形状对壳聚糖抑菌性能的影响甲壳质有3种晶型，即α、β和γ－壳二糖聚合物，目前，人们对壳聚糖的研究绝大多是针对α晶型，对其他两种研究甚少。蒋霞云等通过对比α－壳聚糖和β－壳聚糖的抑菌性能得出，具有高黏度和高脱乙酰度的β－壳聚糖的抑菌性能强于α－壳聚糖， 从而填补了壳聚糖抑菌性能研究在该方面的空白。 辐射对壳聚糖抑菌性能的影响 目前，由辐射方法改变壳聚糖的抑菌性研究已经逐步深入进行，分别有金黄色葡萄球菌、酵母菌等多个菌种被测试，并分别得出了不同的作用效果及不同的作用浓度。王勇、张成刚等人将壳聚糖经 100Kgy60Coγ－射线辐射处理后，发现其对金黄色葡萄球菌抑菌效果最强，比为辐射前增加100倍，且最适作用浓度为0．01％。孟玲、张中泽通过对酵母菌的抑菌试验验证，经辐射处理后壳聚糖的抑菌活性明显增强，并且0．2g／L的辐射壳聚糖具有明显的抑菌活性。 化学改性对壳聚糖抑菌性能的影响 羧甲基化羧甲基壳聚糖是目前研究的较多一种物质，由于羧甲基化后其水溶性增强，因此大大拓宽了壳聚糖的应用范围。目前，羧甲基壳聚糖大多被用于食品保鲜方面。李治等人经实验证实，羧甲基壳聚糖在羧甲基化度小于0．6～0．8时，抗菌性均大于壳聚糖，当羧甲基化度0．3～0．6范围内，羧甲基壳聚糖具有较强的抗菌性，羧甲基化度大于或小于此范围，抗菌性均有所下降。 磺化由于壳聚糖上具有较多的活泼集团，因此较容易进行各类集团的转化与连接。黎碧娜等对磺化壳聚糖的抑菌性能进行了研究认为，磺化壳聚糖对大肠杆菌、枯草杆菌、葡萄球菌、黑曲霉、假丝酵母都有抑制作用，并且浓度越高，抑菌效果越好。此外，磺化羟丙基壳聚糖和黄原酸壳聚糖也具有一定的抑菌性。
Chitosan 1 Nonproprietary Names BP:Chitosan Hydrochloride PhEur:Chitosan Hydrochloride 2Synonyms 2-Amino-2-deoxy-(1,4)-b -D -glucopyranan;chitosani hydrochlori-dum;deacetylated chitin;deacetylchitin;b -1,4-poly-D -glucosamine;poly-D -glucosamine;poly-(1,4-b -D -glucopyranosamine).3Chemical Name and CAS Registry Number Poly-b -(1,4)-2-Amino-2-deoxy-D -glucose [9012-76-4] 4Empirical Formula and Molecular Weight Partial deacetylation of chitin results in the production of chitosan,which is a polysaccharide comprising copolymers of glucosamine and N -acetylglucosamine.Chitosan is the term applied to deacety-lated chitins in various stages of deacetylation and depolymeriza-tion and it is therefore not easily defined in terms of its exact chemical composition.A clear nomenclature with respect to the different degrees of N -deacetylation between chitin and chitosan has not been defined,(1–3)and as such chitosan is not one chemical entity but varies in composition depending on the manufacturer.In essence,chitosan is chitin sufficiently deacetylated to form soluble amine salts.The degree of deacetylation necessary to obtain a soluble product must be greater than 80–85%.Chitosan is commercially available in several types and grades that vary in molecular weight by 10000–1000000,and vary in degree of deacetylation and viscosity.(4)5 Structural Formula 6Functional Category Coating agent;disintegrant;film-forming agent;mucoadhesive;tablet binder;viscosity increasing agent. 7 Applications in Pharmaceutical Formulation or Technology Chitosan is used in cosmetics and is under investigation for use in a number of pharmaceutical formulations.The suitability and performance of chitosan as a component of pharmaceutical formulations for drug delivery applications has been investigated in numerous studies.(3,5–8)These include controlled drug delivery applications,(9–14)use as a component of mucoadhesive dosage forms,(15,16)rapid release dosage forms,(17,18)improved peptide delivery,(19,20)colonic drug delivery systems,(21,22)and use for gene delivery.(23)Chitosan has been processed into several pharmaceu-tical forms including gels,(24,25)films,(11,12,26,27)beads,(28,29)micro-spheres,(30,31)tablets,(32,33)and coatings for liposomes.(34)Furthermore,chitosan may be processed into drug delivery systems using several techniques including spray-drying,(15,16)coacerva-tion,(35)direct compression,(32)and conventional granulation processes.(36) 8Description Chitosan occurs as odorless,white or creamy-white powder or flakes.Fiber formation is quite common during precipitation and the chitosan may look ‘cottonlike ’.9Pharmacopeial Specifications See Table I. Table I:Pharmacopeial specifications for chitosan.Test PhEur 6.5Identification tCharacters tAppearance of solution t Matter insoluble in water 40.5%pH (1%w/v solution) 4.0–6.0Viscosity tDegree of deacetylation t Chlorides 10.0–20.0%Heavy metals 440ppm Loss on drying 410%Sulfated ash 41.0% 10Typical Properties Chitosan is a cationic polyamine with a high charge density at pH <6.5,and so adheres to negatively charged surfaces and chelates metal ions.It is a linear polyelectrolyte with reactive hydroxyl and amino groups (available for chemical reaction and salt forma-tion).(7)The properties of chitosan relate to its polyelectrolyte and polymeric carbohydrate character.The presence of a number of amino groups allows chitosan to react chemically with anionic systems,which results in alteration of physicochemical character-istics of such combinations.The nitrogen in chitosan is mostly in the form of primary aliphatic amino groups.Chitosan therefore undergoes reactions typical of amines:for example,N -acylation and Schiff reactions.(3)Almost all functional properties of chitosan depend on the chain length,charge density,and charge distribu-tion.(8)Numerous studies have demonstrated that the salt form,molecular weight,and degree of deacetylation as well as pH at which the chitosan is used all influence how this polymer is utilized in pharmaceutical applications.(7) Acidity/alkalinity pH =4.0–6.0(1%w/v aqueous solution)Density 1.35–1.40g/cm 3 Glass transition temperature 2038C (37) Moisture content Chitosan adsorbs moisture from the atmo-sphere,the amount of water adsorbed depending upon the initial moisture content and the temperature and relative humidity of the surrounding air.(38) Particle size distribution <30m m Solubility Sparingly soluble in water;practically insoluble in ethanol (95%),other organic solvents,and neutral or alkali solutions at pH above approximately 6.5.Chitosan dissolves readily in dilute and concentrated solutions of most organic C 159
壳聚糖特性及其应用 作者简介：孔佳琦，女，本科，西北民族大学化工学院，专业：制药工程。 力芬，女，本科，西北民族大学化工学院，专业：环境工程。 摘要：壳聚糖是自然界中储量丰富天然高分子化合物，壳聚糖及其衍生物具有各种优良的性质，本文主要介绍了壳聚糖的特性以及其在不同方面的应用情况，为壳聚糖的研究发展提供依据和思路。 关键词：壳聚糖；特性；应用 壳聚糖（chitosan）又称脱乙酰甲壳素，是由自然界广泛存在的几丁质（chitin）经过脱乙酰作用得到的，化学名称为聚葡萄糖胺（1-4）-2-氨基-B-D葡萄糖。纯甲壳素和纯壳聚糖都是一种白色或灰白色透明的片状或粉状固体，无味、无臭、无毒性，纯壳聚糖略带珍珠光泽。在特定的条件下，壳聚糖能发生水解、烷基化、酰基化、羧甲基化、磺化、硝化、卤化、氧化、还原、缩合和络合等化学反应，可生成各种具有不同性能的壳聚糖衍生物，从而扩大了壳聚糖的应用围。本文就壳聚糖的特性和应用进行阐述，为其研究和发展提供依据和思路。
1.特性 1.1抗菌性。壳聚糖是唯一一种天然的弱碱性多糖在弱酸溶剂中易于溶解，溶解后的溶液中含有氨基（NH2+），这些氨基通过结合负电子来抑制细菌。壳聚糖的抗菌性会随着其浓度的增加而增强。壳聚糖对大肠杆菌、金黄色葡萄球菌等有较强的抑制作用。 1.2吸附性。壳聚糖具有很强的吸附功能，特别是对重金属离子的吸附如对铜、汞、铅等离子的吸收。壳聚糖的吸附活性可以有选择地发挥作用。当然还可以吸附胆固醇、甘油三酯、胆酸、油脂[1]等。 1.3保湿性。壳聚糖衍生物分子中有许多活泼的亲水极性基团如-OH、-COOH及-NH2，这些基团可以使其显示出保湿性。对于羧基化壳聚糖，其羟基的含量远大于其他衍生物，且羧基的亲水性所以能够结合更多的水分。因此羧基化壳聚糖的吸湿、保湿性也就明显高于其他类型的壳聚糖衍生物。 1.4成膜性。壳聚糖是线性高分子聚合物，理化性能稳定，可生物降解，粘合性好，成纤成膜性能优良。吴国杰[2]等人研究了壳聚糖膜的制备方法和性能，探讨了壳聚糖溶液成膜的最佳工艺条件。 1.5调节作用。壳聚糖可激活体具有免疫功能的淋巴细胞，使其能分辨正常细胞和癌细胞，并杀死癌细胞。还能调
第24卷第1期菏泽医学专科学校学报VOL.24NO.1 2012年JOURNAL OF HEZE MEDICAL COLLEGE2012 doi:10.3969/j.issn.1008-4118.2012.01.01 躯干神经嵴干细胞壳聚糖纤维复合硅胶管治疗 坐骨神经损伤的实验研究 杨洁 (菏泽医学专科学校,山东菏泽274000) 摘要:目的探讨体外培养的躯干神经嵴干细胞在壳聚糖纤维上立体培养后复合硅胶管治疗坐骨神经损伤的实验研究。方法采用孕10.5d Wistar大鼠的胚胎神经管分离培养躯干神经嵴干细胞，将体外培养48h的躯干神经嵴干细胞接种在壳聚糖纤维材料上，观察两者的组织相容性。应用黏附有躯干神经嵴干细胞壳聚糖纤维复合硅胶管桥接了缺损的大鼠坐骨神经，术后进行电生理、组织学检测，观察了周围神经再生及神经通路重建的状况。结果从神经管取材的躯干神经嵴干细胞在无血清培养基内可以大量扩增；将躯干神经嵴干细胞接种在壳聚糖纤维支架材料上行扫描电镜观察，可见躯干神经嵴干细胞贴附在壳聚糖纤维表面，存活良好，表明躯干神经嵴干细胞与壳聚糖纤维支架材料有良好的相容性；桥接手术后，电生理检测结果显示，含躯干神经嵴干细胞的壳聚糖-硅胶管桥接组坐骨神经传导潜速率及波幅值显著好于单纯硅胶管桥接组(均P<0.01)；甲苯胺蓝染色光镜观察及图像分析结果均显示含躯干神经嵴干细胞的壳聚糖-硅胶管桥接组再生轴突的髓鞘化更明显，再生纤维密度及直径等各检测指标均优于单纯硅胶管桥接组（均P<0.01）。结论壳聚糖纤维支架材料与躯干神经嵴干细胞构建的桥接管具有良好的生物相容性，其中躯干神经嵴干细胞可分化为施万细胞，以此桥接缺损的周围神经，可促进其再生和修复。 关键词：躯干神经嵴干细胞；组织工程；壳聚糖纤维；神经再生 中图分类号：R616;R651.2文献标识码：A文章编号：1008-4118（2012）01-0001-05 An Empirical Study on Repairing the Injury of Sciatic Nerve with the Trunk Neural Creat Stem Cell and Chitosan Fiber to Compound the Slilica Gel-tube Yang jie (heze Medical College,heze,shandong,274000) Absrract:Objective We isolate and culture the trunk neural crest stem cell using tissue culture of neural tube in the E10.5 Wistar rat embryo in defined medium,then explore its’biological properties.Methods The trunk neural crest stem cells using tis?sure culture of neural tube in vitro were cultured on the chitosan https://www.doczj.com/doc/e03846203.html,ed immunofluoresecence to indentify the trunk neural crest cells.Observed the histocompatibility of them,the trunk neural stem cells were cultured with the chitosan-slilca sebific duct scaffold, the growth of cells was observed by scanning electron microscope.10mm sciatic nerve defects were bridged with chitosan-slilca sebif?ic duct scaffold cultured with trunk neural stem cells,sebific gel tubes without trunk neural stem cells served as controls.After grafting, the regenerated nerves were evaluated by electrophysiological examination,histological staining,retrograde tracing and electron mi?croscope observe.Results Using tissure culture of neural tube,we can isolate and culture the trunk neural crest stem cells.The trunk neural crest stem can grow adhered on the chitosan fiber after inoculation.Scanning elector microscope,the trunk neural crest stem cell were spindle.proliferated and migrated along fiber.There is good histocompatibibity between the chitosan fiber and the trunk neu?ral crest stem cells,the trunk neural crest stem cell can differentiate into Schwann cell..At8weeks after surgery,weak action potentials were found in the experiment group only.At14weeks after surgery,the conduction velocity and wave amplitude of experiment group was better than the control group,and the difference was evident（P<0.01）.Conclusion There is good histocompatibibity between the chitosan fiber and the trunk neural crest stem cells,the trunk neural crest stem cell can differentiate into Schwann cell.They con?tributed to the promotion of axonal regeneration. Key words:Neural crest；Stem cell;tissue engineering;chitosan;nerve regeneration 周围神经的损伤，再生和功能重建一直是外科领域中的难题之一。多年来临床常规的治疗方法是自体神经移植,但自体神经移植不仅会给供区带来新的创伤，而且常采用的供体—皮神经较细小，不能满足临床需要。绝大多数的周围神经是混合神经，它们含有多种纤维成分，所以当神经损伤后导致损伤近端及远端神经的对位关系紊乱从而影响神经的再生和功能修复[1]。虽然现在的显微外科技术十分 基金项目：菏泽医学专科学校基金研究课题（编号：H11K01）。1
壳聚糖和壳聚糖衍生物的抑菌作用 摘要：壳聚糖是一类有着广谱抑菌活性的天然多糖，其生物相容性好、易降解、无毒，因而作为一种可再生资源在抑菌领域受到了越来越多的关注。本文通过对壳聚糖来源、性质、壳聚糖衍生物的化学改性的方法和抑菌作用的分析，并对今后壳聚糖衍生物抑菌情况进行了初步的展望。为研制和开发新型的高抑菌活性的壳聚糖衍生物的开发提供理论参考。 关键词：壳聚糖；衍生物；抑菌；机理 引言 壳聚糖是无毒、无污染，具有可再生、无毒副作用，生物相容性和降解性良好的天然氨基多糖。目前已被广泛应用于医药[1-2]、农业[3]、食品[4-5]等领域，并成为最近生物新材料研究的热点[6-7]。壳聚糖具有抗菌活性，对多种植物病原细菌和真菌均抑制作用[8]。但由于其不溶于水和大多数有机溶剂，只溶于稀酸，在很大程度上限制了其应用范围。壳聚糖通过化学改性，可以得到具有一定官能团的壳聚糖衍生物。与壳聚糖相比，这些衍生物的性能往往有较明显的改善。对于壳聚糖的化学修饰研究较多的有壳聚糖的酰基化、烷基化、羟基化、醛亚胺基化、硫酸酯化、羧甲基化、季铵化等，其中季铵化、羧甲基化和硫酸酯化的产物由于具有良好的水溶性而备受重视[9]。有关壳聚糖的结构修饰和构效关系的研究已成为研究热点[10],因此，研究开发具有更高抗菌活性的壳聚糖衍生物，对于改善人们的生活质量具有重要意义。 1壳聚糖的来源和性质 1.1壳聚糖的来源 壳聚糖是自然界唯一的碱性天然多糖，壳聚糖的历史得追随到19世纪，当时Rouget 在甲壳素的天然聚合物中发现了其脱乙酰化的形式[11]。壳聚糖是白色或淡黄色无定型、半透明、略有珍珠光泽的固体。由于其原料和制备方法的不同，其分子量也有所不同，可以从数十万到数百万不等。甲壳素在浓碱中加热处理后，就可以脱去部分乙酰基，得到壳聚糖，反应路线如下。
［收稿日期］ ２０１２－０８－１４；２０１２－１１－１１修回 ［基金项目］ 贵州省烟草专卖局（公司）项目“控制烟叶农残监测体系研究”（２００９０８） ［作者简介］ 陈兴江（１９７７－），男，助理研究员，从事烟草植保及烟叶安全性研究。Ｅ－ｍａｉｌ：ｃｈｅｎｘｉｎｇｊｉａｎｇ １＠１６３．ｃｏｍ ＊ 通讯作者：商胜华（１９６８－），男，副研究员，从事烟草病虫害预测及防治研究。Ｅ－ｍａｉｌ：ｓｓｈ６６８８＠ｓｉｎａ．ｃｏｍ［文章编号］１００１－３６０１（２０１２）１２－０７４１－０１１１－ ０３几种植物诱抗剂对烟草农艺性状及抗病性的影响 陈兴江，邱雪柏，陆宁，商胜华＊ （贵州省烟草科学研究所，贵州贵阳５５００８１ ） ［ 摘 要］为了对开发和研制防治烟草黑胫病的抗逆诱导剂提供理论支持，以云烟８５为材料，进行了不同抗逆诱导剂对烤烟生长及烟草黑胫病的防效试验。结果表明：各种诱抗剂对烟草生长均有一定的促进作 用，能适当提高烟草农艺性状指标，以移栽灵、壳聚糖的效果较好；移栽灵与壳聚糖对黑胫病具有较好的抑制作用，推迟了发病始期，减缓了发病速率。 ［关键词］植物诱抗剂；烤烟；黑胫病；农艺性状；抗逆诱导［中图分类号］Ｓ４３２ ［文献标识码］ＡＥｆｆｅｃｔｓ ｏｆ Ｓｅｖｅｒａｌ Ｋｉｎｄｓ ｏｆ Ｐｌａｎｔ Ｅｌｉｃｉｔｏｒｓ ｏｎ Ａｇ ｒｏｎｏｍｉｃＴｒａｉｔｓ ａｎｄ Ｄｉｓｅａｓｅ Ｒｅｓｉｓｔａｎｃｅ ｏｆ ＴｏｂａｃｃｏＣＨＥＮ Ｘｉｎｇｊｉａｎｇ，ＱＩＵ Ｘｕｅｂａｉ，ＬＵ Ｎｉｎｇ，ＳＨＡＮＧ Ｓｈｅｎｇ ｈｕａ＊ （Ｇｕｉｚｈｏｕ Ｔｏｂａｃｃｏ Ｒｅｓｅａｒｃｈ Ｉｎｓｔｉｔｕｔｅ，Ｇｕｉｙａｎｇ， Ｇｕｉｚｈｏｕ５５００８１，Ｃｈｉｎａ） Ａｂｓｔｒａｃｔ：Ａ ｃｏｎｔｒｏｌ ｔｅｓｔ ｏｆ ｔｈｅ ｅｆｆｅｃｔｓ ｏｆ ｄｉｆｆｅｒｅｎｔ ｐｌａｎｔ ｅｌｉｃｉｔｏｒｓ ｏｎ ｔｏｂａｃｃｏ ｇ ｒｏｗｔｈ ａｎｄ ｔｏｂａｃｃｏ ｂｌａｃｋｓｈａｎｋ ｗａｓ ｃｏｎｄｕｃｔｅｄ ｔａｋｉｎｇ Ｙｕｎｙａｎ ８５ａｓ ｔｈｅ ｍａｔｅｒｉａｌ ｔｏ ｐｒｏｖｉｄｅ ａ ｔｈｅｏｒｅｔｉｃａｌ ｓｕｐｐｏｒｔ ｆｏｒ ｅｘｐｌｏｉｔｉｎｇ ａｎｄｄｅｖｅｌｏｐｉｎｇ ｐｌａｎｔ ｅｌｉｃｉｔｏｒｓ．Ｔｈｅ ｒｅｓｕｌｔｓ ｓｈｏｗｅｄ ｔｈａｔ ａｌｌ ｔｈｅ ｐｌａｎｔ ｅｌｉｃｉｔｏｒｓ ｃｏｕｌｄ ｐｒｏｍｏｔｅ ｔｏｂａｃｃｏ ｇｒｏｗｔｈ ｉｎｃｅｒｔａｉｎ ｄｅｇｒｅｅ．Ｍｅａｎｗｈｉｌｅ，ｔｈｅｙ ｃｏｕｌｄ ａｐｐｒｏｐｒｉａｔｅｌｙ ｅｎｈａｎｃｅ ｔｈｅ ｉｎｄｅｘｅｓ ｏｆ ａｇｒｏｎｏｍｉｃ ｔｒａｉｔｓ．Ｉｓｏｌａｎｅ ａｎｄｃｈｉｔｏｓａｎ ｈａｄ ｂｅｔｔｅｒ ｅｆｆｅｃｔ ａｎｄ ｔｈｅｙ ｃｏｕｌｄ ｐｒｅｆｅｒａｂｌｙ ｉｎｈｉｂｉｔ ｂｌａｃｋ ｓｈａｎｋ ａｎｄ ｄｅｌａｙ ｅｍｅｒｇｉｎｇ ｔｉｍｅ ａｎｄ ｓｌｏｗｄｏｗｎ ｔｈｅ ｉｎｃｉｄｅｎｃｅ ｒａｔｅ．Ｋｅｙ ｗｏｒｄｓ：ｐｌａｎｔ ｅｌｉｃｉｔｏｒｓ；ｆｌｕｅ－ｃｕｒｅｄ ｔｏｂａｃｃｏ；ｂｌａｃｋ ｓｈａｎｋ；ａｇｒｏｎｏｍｉｃ ｔｒａｉｔｓ；ｓｔｒｅｓｓ－ｒｅｓｉｓｔａｎｔ ｉｎｄｕｃ－ｔｉｏｎ 烟草黑胫病是由烟草疫霉Ｐｈｙｔｏｐ ｈｔｈｏｒａ ｎｉｃ－ｏｔｉａｎａｅ Ｂｒａｄａ ｄｅ Ｈａｎｎ引起的土传真菌性病害，俗称“黑根”、“黑杆疯”，多发生于烟草成株期。幼苗染病时茎基部出现黑色病斑，茎秆染病时茎基部初呈水渍状黑斑，严重时植株萎蔫死亡。烟草黑胫病是 烟草主要的毁灭性病害之一［ １－ ４］，由于烟田连作面积不断扩大，连作年限不断增长而加重了该病流行，目前，我国平均每年因烟草黑胫病造成的经济损失达 １亿元以上， 仅次于烟草病毒病［３，５－ ６］。生产上一般采用抗病品种、栽培措施及化学农药等综合防治措 施控制该病害，虽然取得了一定的防治效果，但同时也存在不少问题， 如化学农药造成的环境污染及抗性问题。植物的诱导抗病性又称系统获得抗性或植物免疫，是植物在一定的诱抗剂刺激下，使植物细胞内发生一系列反应，诱导植物对病原菌侵染具有抵抗性的特征，具有多抗、高抗和卫生安全等优点，是 现代植病防治的一条重要途径［７－ ９］。目前，植物诱导抗病性已在水稻稻瘟病［１０－ １１］、百合根腐病［１２］、烟草青枯病［１３］和黄瓜枯萎病［１４］ 等方面得到应用研究，但 有关植物诱导抗病性在烟草黑胫病上的研究尚未见报道。因此，笔者等进行了不同抗逆诱导剂对烟草 生长性状的影响及对黑胫病的防治研究，为研制防治烟草黑胫病的抗逆诱导剂开发提供理论支持。 １ 材料与方法 １．１ 供试材料 烤烟品种为云烟８５， 由贵州省烟草科学研究所提供，２０１１年种植于贵州福泉。 供试药剂包括脱落酸微胶囊（贵州省烟草科学研究所研制） 、甲壳胺低聚糖（北京雷力农用化学有限公司）、壳聚糖（沈阳市沈北新区绿色春天科技农资中心）、２０％移栽灵乳油（湖北移栽灵农业科技股份有限公司）、５８％甲霜灵锰锌可湿性粉剂（浙江禾本科技有限公司） 、水杨酸甲酯（苏州新凯恒化工）、植物激活蛋白（湖南长沙马坡岭高科技园）、芸苔素内酯（南京博士邦化工科技有限公司）、复硝酸钠（郑州信联生化科技有限公司）。１．２ 试验设计 试验共设１１个处理：处理１，移栽灵１ ５００倍液；处理２，０．５ｇ／Ｌ甲壳胺低聚糖８００倍液； 处理３，２５０ｍｇ／Ｌ的脱落酸微胶囊５０倍液；处理４，壳聚糖；处理５，水杨酸甲酯１ ０００倍液；处理６，植物激 贵州农业科学 ２ ０１２，４０（１２）：１１１～１１３ Ｇｕｉｚｈｏｕ Ａｇ ｒｉｃｕｌｔｕｒａｌ Ｓｃｉｅｎｃｅｓ
Electrochimica Acta 105 (2013) 378–383 Contents lists available at SciVerse ScienceDirect Electrochimica Acta j 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 /e l e c t a c t a Chitosan,a new and environmental benign electrode binder for use with graphite anode in lithium-ion batteries Lili Chai a ,Qunting Qu a ,Longfei Zhang a ,Ming Shen b ,Li Zhang a ,?,Honghe Zheng a ,? a School of Energy,Soochow University,Suzhou,Jiangsu 215006,China b Huasheng Chemical Corporation,Zhangjiagang,Jiangsu 215635,China a r t i c l e i n f o Article history: Received 22March 2013 Received in revised form 30April 2013Accepted 6May 2013 Available online 14 May 2013 Keywords: Lithium-ion batteries Graphite anode Electrode binder Chitosan a b s t r a c t Chitosan was applied as the electrode binder material for a spherical graphite anode in lithium-ion https://www.doczj.com/doc/e03846203.html,pared to using poly (vinylidene ?uoride)(PVDF)binder,the graphite anode using chitosan exhibited enhanced electrochemical performances in terms of the ?rst Columbic ef?ciency,rate capabil-ity and cycling behavior.With similar speci?c capacity,the ?rst Columbic ef?ciency of the chitosan-based anode is 95.4%compared to 89.3%of the PVDF-based anode.After 200charge–discharge cycles at 0.5C ,the capacity retention of the chitosan-based electrode showed to be signi?cantly higher than that of the PVDF-based electrode.Electrochemical impedance spectroscopy (EIS)and scanning electron microscopy (SEM)measurements were carried out to investigate the formation and evolution of the solid electrolyte interphase (SEI)formed on the graphite electrodes.The results show that a thin,homogenous and stable SEI layer is formed on the graphite electrode surface with chitosan binder compared with that using the conventional PVDF binder ? 2013 Elsevier Ltd. All rights reserved. 1.Introduction Electrode binder plays a very important role in fabricating high-performance electrodes as it holds active materials and conductive additives into a cohesive laminate and provides the adhesion between the laminate and the current collector.In the past two decades,poly (vinylidene ?uoride)(PVDF)was the most widely used binder material for Li-ion battery electrodes.This is attributed to its good electrochemical stability,binding capability and ability to absorb electrolyte [1–5].However,PVDF polymer is costly and it requires the use of environmentally unfriendly N-methyl pyr-rolidone (NMP)solvent in the processing.Besides,this polymer is very sensitive to the environmental humidity.It undergoes a severe degradation of viscosity after absorbing water.As a ?uorinated polymer,PVDF also shows a certain reactivity against lithium metal and lithiated graphite (Li x C 6),producing resistive LiF and C CF species on the electrode surface,especially at elevated tempera-tures [6,7].For these reasons,the development of greener,cheaper and more electrochemical stable electrode binder is considered as a goal of strategic importance for battery technologies.In recent years,many groups have been studying new electrode binder materials for the realization of greener battery processing and ?Corresponding authors. E-mail addresses:hhzheng@https://www.doczj.com/doc/e03846203.html, (L.Zhang),zhangli81@https://www.doczj.com/doc/e03846203.html, (H.Zheng). high performance Li-ion batteries.Among different binder systems,water-soluble binders are not only much cheaper than PVDF,but also allow electrode processing in aqueous slurries.These polymers can be easily disposed at the end of the life of the battery.Gelatin [8–11],sodium carboxy-methyl cellulose (CMC-Na)and styrene-butadiene rubber (SBR)[12–18],poly(acrylic acid)(PAA)[19–23],poly(methacrylic acid)(PMA)[24],poly(vinyl alcohol)(PVA)[25],alginate [26,27],poly(acrylamide-co-diallyldime-thylammonium chloride (AMAC)[28],poly (acrylonitrile-methyl methacrylate)(AMMA)[29],and polyimide (PI)[30],all have been reported as promising new binder systems replacing PVDF and some of them have been successfully used in commercial lithium ion batter-ies. In this paper,chitosan,as a water-soluble polymer,was adopted as a new electrode binder for a graphite anode.Chitosan is a polysaccharide composed mainly of ?-(1,4)-linked 2-deoxy-2-amino-d -glucopyranose units.The molecular structure of it is provided in Fig.1.This polymer is one of the most plentiful nat-ural biopolymers produced from poly (N-acetyl-d -glucosamine)(chitin)[31].Chitosan is widely used in many ?elds including molecular separation,food packaging ?lm,arti?cial skin,bone substitutes,water treatment and so on [32–34].In Li-ion battery ?eld,chitosan has also been attempted as the template for active material synthesis [35],and carbon coating precursor [36].How-ever,to the best of our knowledge,this polymer has never been adopted as an available binder material for Li-ion batteries up to today. 0013-4686/$–see front matter ? 2013 Elsevier Ltd. All rights reserved.https://www.doczj.com/doc/e03846203.html,/10.1016/j.electacta.2013.05.009