壳聚糖改性生物炭的制备及其对水溶液中Cd^(2+)的吸附机制

Preparation of Chitosan-modified Biochar and Its Adsorption Mechanism for Cd^(2+)in Aqueous Solution

以猕猴桃枝为原料,壳聚糖作为胺基表面改性剂,制备了一种绿色环保、对环境中重金属有良好吸附效果的功能性生物炭材料.采用批量吸附实验研究了改性前后生物炭的吸附性能.借助SEM-EDS、FTIR和XPS表征方法,分析了改性前后生物炭的形貌结构和官能团变化,探究了其对溶液中Cd^(2+)的吸附机制.结果表明,改性后的生物炭表面,引入了羟基(—OH)、羰基(—C=O)和氨基(—NH_(2))等基团,显著提高了吸附性能,对Cd^(2+)的吸附量较改性前增加107.12%.Lagergren准二级动力学模型和Langmuir等温吸附方程能较好地描述吸附过程,说明吸附速率由材料表面活性位点决定,吸附过程以化学吸附为主.对Cd^(2+)的吸附机制主要是配位作用、表面沉淀作用、离子交换作用和阳离子—π键作用,吸附过程为自发的吸热过程.经过5次吸附-解吸循环后,改性后生物炭对Cd^(2+)的吸附容量仍保持在初始吸附量的80%以上,表现出良好的可重复利用性.研究成果体现绿色化学的理念,所制备的壳聚糖改性生物炭可应用于镉污染水体和土壤的修复.

Chitosan-modified biochar(CBC)was prepared as a low-cost and highly efficient adsorbent for Cd^(2+)in aqueous solutions.Batch adsorption experiments were conducted to evaluate the adsorption performance.Characterization experiments with SEM-EDS,FTIR,and XPS were used to analyze the surface microstructure and chemical composition of the adsorbent.The results showed that the adsorption performance of CBC was remarkably improved by the introduction of surface functional groups(—OH,—C=O,and—NH_(2)).The pseudo-second-order kinetic model and Langmuir model were better for describing the kinetics and isotherms for Cd^(2+)adsorption onto CBC,indicating that the adsorption rate was determined by the active sites and controlled by monolayer chemisorption.The adsorption process was endothermic spontaneous,and the key mechanisms involved complexation,precipitation,cation exchange,and cation-π bonds.After five instances of adsorption-desorption cycles,the adsorption capacity of CBC for Cd^(2+)still remained above 80% of the initial adsorption capacity,indicating that CBC had a favorable recyclability.The current work embodies the concept of green chemistry,and the prepared chitosan-modified biochar was a promising adsorbent for the removal of Cd^(2+)in wastewater and soil.