重金属吸附剂巯基丙酰化小麦秸秆的制备与表征

Preparation and Characterization of Mercaptopropionyl Wheat Straw as Heavy Metal Adsorbent

该文以小麦秸秆(WS)、氢氧化钠(NaOH)、L-半胱氨酸(L-Cys)、碳二亚胺盐酸盐(EDC·HCl)、N-羟基琥珀酰亚胺(NHS)为原料,通过化学预处理、酰化反应在WS中引入巯基官能团,制备出重金属吸附剂巯基丙酰化小麦秸秆(MPWS)。通过吸附实验考察了MPWS对水中Cd(Ⅱ)的去除性能,采用单因素实验法确定了MPWS的制备条件,借助红外分析(FTIR)、扫描电镜及能谱分析(SEM-EDS)等表征手段探讨了MPWS的制备机理和吸附机理。结果表明,在WS粒径为0.60 mm,化学预处理NaOH溶液浓度为0.1 mol/L,n(EDC·HCl)∶n(L-Cys)为0.05∶1,m(NHS)∶m(EDC·HCl)为1∶1,m(CWS)∶m(L-Cys)为1∶5,反应介质pH值为10,反应温度为35℃,反应时间为3 h的制备条件下,MPWS对水中Cd(Ⅱ)的吸附性能最好,Cd(Ⅱ)的最高去除率可达94.20%。FTIR和SEM-EDS分析表明,NaOH溶液预处理除去了一定量的半纤维素、木质素,MPWS中成功引入了巯基、胺基、羧基,Cd(Ⅱ)被吸附到MPWS结构中;MPWS对Cd(Ⅱ)的吸附机理主要包括配位作用、离子交换作用、静电吸附作用和物理吸附作用。

A novel heavy metal adsorbent,called mercaptopropionyl wheat straw(MPWS),was prepared by chemical pretreatment and acylation reaction by using wheat straw(WS),sodium hydroxide(NaOH),L-cysteine(L-Cys),carbondiimide hydrochloride(EDC·HCl)and N-hydroxysuccinimide(NHS)as raw materials,and the sulfhydryl groups were introduced in MPWS.The removal performance of MPWS for Cd(Ⅱ)in water was investigated by adsorption experiment,and the preparation conditions of MPWS were determined by single factor experiment.The preparation and adsorption mechanism of MPWS were discussed by means of FTIR,SEM and EDS.The results showed that the preparation conditions for MPWS were as follows:the size of WS was 0.60 mm(through 30-mesh screen),NaOH solution concentration of chemical pretreatment was 0.1 mol/L,the molar ratio of EDC·HCl and L-Cys was 0.05∶1,the mass ratio of NHS and EDC·HCl was 1∶1,the mass ratio of WS and L-Cys was 1∶5,pH value in reaction medium was 10,the reaction temperature was 35℃,and reaction time was 3 h.Under the preparation conditions,MPWS had the best removal performance of Cd(Ⅱ)in water,and the maximum removal rate could reach 94.20%.FTIR and SEM-EDS analysis showed that NaOH pretreatment removed a certain amount of hemicellulose and lignin.Sulfhydryl,amino and carboxyl groups were successfully introduced into MPWS,and Cd(Ⅱ)was adsorbed by MPWS.The adsorption mechanism of MPWS for Cd(Ⅱ)mainly include coordination,ion exchange,electrostatic adsorption and physical adsorption.