木质纤维素/火山灰基地聚合物表征及对Pb(Ⅱ)的吸附性能

Characterization of lignocellulose/volcanic tuff-based geopolymer and its adsorption properties for Pb(Ⅱ)

地聚合物(Geopolymer,简称GP)是一种具有三维立体网状结构的无机聚合物,对重金属有良好的吸附性能.以火山灰掺杂木质纤维素为原料制备了木质纤维素/火山灰基地聚合物,考察了投加量、pH、时间、温度和初始离子浓度等因素对掺杂木质纤维素前后的GP吸附Pb(Ⅱ)的影响,通过对比说明掺杂对吸附性能的提升作用.结果表明,在55℃,pH=5、投加量为0.6 g·L^(-1)、Pb(Ⅱ)初始浓度为400 mg·L^(-1)时,掺杂木质纤维素得到的GP(简称L-GP)对Pb(Ⅱ)最大吸附量可达460.83 mg·g^(-1),远优于仅用火山灰所得的GP的223.21 mg·g^(-1).两种GP对Pb(Ⅱ)的吸附均很好地符合二级动力学规律和Langmuir方程,且反应过程都是熵增吸热的过程.通过XRD等分析表明,木质纤维素掺杂火山灰作为原料而制备所得的复合材料保留了GP的结构特点,而且能够利用木质纤维素上丰富的官能团从而提升GP的吸附量,是一种优良高效的吸附剂.本文对利用火山灰和木质纤维素制备高性能GP及其潜在应用具有重要指导意义.

Geopolymer(GP)is an inorganic polymer with three-dimensional network structure,which has excellent adsorption capacity for heavy metals. In this study,a novel geopolymer adsorbent was prepared by using natural volcanic tuff and lignocellulose as raw materials. The effects of dosage,pH,time,temperature and initial ion concentration on the adsorption of Pb(Ⅱ)by GP,before and after lignocellulose doping,were investigated. The results show that a maximum Pb(Ⅱ)adsorption capacity of 460.83 mg·g^(-1)by the GP(L-GP for short)was achieved at 55 ℃,pH=5,dosage 0.6 g·L^(-1)and an initial Pb(Ⅱ)concentration of 200 mg·L^(-1),which is much higher than that of GP prepared with volcanic ash alone(223.21mg·g^(-1)). The adsorption of Pb(Ⅱ)by two kinds of GP was well fitted with the second-order kinetic model and Langmuir equation,and the reaction processes are entropy-increasing and endothermic. XRD analysis result shows that the composite adsorbant retains the structural characteristics of GP,and the adsorption capacity of GP can be improved by the rich functional groups on lignocellulose,leading to an excellent adsorption capacity. This study has an important theoretical significance for improving GP adsorption capacity for practical application.