Cu(Ⅱ)印迹壳聚糖交联膜的表征及其吸附热力学特性

Characterization and Thermodynamic Properties of Cu(Ⅱ) Imprinted Chitosan Crosslinked Membrane

为处理低浓度重金属废水,采用分子印迹、化学预交联及交联方法,制备了一种新型的Cu(Ⅱ)印迹壳聚糖交联膜(IMCu(Ⅱ)-E-CTS),对该膜的孔隙率、溶胀率、氨基含量、表面形态、官能团以及结晶性等性能进行了表征.考察了该膜对低浓度(20～70 mg.L-1)Cu(Ⅱ)的吸附热力学特性.结果表明,IMCu(Ⅱ)-E-CTS孔隙率、溶胀率和氨基含量分别为76.9%、109%、4.26 mmol.g-1;与壳聚糖膜(CTS)相比,IMCu(Ⅱ)-E-CTS溶胀率降低了44.0%、孔隙率升高了528%、氨基含量降低了16.5%;与壳聚糖交联膜(E-CTS)相比,其氨基含量升高了24.6%;与CTS和E-CTS相比,IMCu(Ⅱ)-E-CTS的表面形态发生了显著的变化,内部结构变得疏松;与CTS相比,IMCu(Ⅱ)-E-CTS分子链具有不规整性,结晶能力降低.在含等浓度Cu(Ⅱ)、Ni(Ⅱ)、Zn(Ⅱ)混合溶液中,IMCu(Ⅱ)-E-CTS对Cu(Ⅱ)表现出具有良好的选择性.IMCu(Ⅱ)-E-CTS对Cu(Ⅱ)浓度为20～70 mg.L-1的吸附符合Freundlich等温曲线(R2>0.99),该吸附是自发、放热、熵减小的过程.

A new type of Cu（Ⅱ）-imprinted chitosan crosslinked membrane IMCu（Ⅱ）-E-CTS） was prepared via molecular imprinting technology, chemical pre-crosslinking and crosslinking methods for treatment of wastcwater containing low concentration of copper ion. IMCu（Ⅱ）-E-CTS was characterized by porosity, swelling ratio, amino group content, surface morphology, functional group and crystallinity. The thermodynamic properties of Cu （ II ） adsorption on the as-synthesized membrane at the low concentration （20-70 mg,L-1） were studied. It is found that porosity, swelling ratio and amino group contents of IMCu（Ⅱ）E-CTS are 76. 9% , 109% and 4.26 mmol.g-1, respectively. Compared to the pristine chitosan membrane （CTS）, 44. 0% lower swelling ratio, 528% higher of porosity, 16.5% lower of amino group content are found with IMCu（Ⅱ）-E-CTS. Compared to crosslinked chitosan membranes （E-CTS） , 24. 6% higher amino group content is found with IMCu（Ⅱ）-E-CTS. Compared to CTS and E-CTS, the membrane morphology of IMCu（Ⅱ）- E-CTS has undergone significant changes, and the internal structure became loose. Compared with CTS, molecular chain of IMCu（Ⅱ）-E- CTS is irregular and its crystallinity ability is lowered. IMCu（Ⅱ）-E-CTS adsorbs more IMCu（Ⅱ） than that of the other two metal cations [ Ni（Ⅱ） and Zn （Ⅱ） 1- The adsorption of copper ion on IMCu（Ⅱ）-E-CTS for 20-70 mg.L -1 of initial Cu （Ⅱ） concentration follows the Freundlich adsorption isotherm（R2 〉 0. 99）. The adsorption is a spontaneous, exothermic, and entropy-decreased process.