糠醛渣木质素接枝聚丙烯酸水凝胶对Pb^(2+)、Cu^(2+)、Cd^(2+)吸附性能研究

Adsorption properties of lignin-g-polyacrylic acid hydrogel on Pb^(2+),Cu^(2+),Cd^(2+)

以糠醛渣木质素和丙烯酸为原料,制备了可有效去除水中Pb^(2+)、Cu^(2+)和Cd^(2+)离子的糠醛渣木质素-g-聚丙烯酸水凝胶(FRL-g-PAA水凝胶);研究了pH值、温度和离子强度对FRL-g-PAA水凝胶吸附Pb^(2+)、Cu^(2+)、Cd^(2+)性能的影响;分析了FRL-g-PAA水凝胶对Pb^(2+)、Cu^(2+)和Cd^(2+)的吸附动力学、吸附等温线及吸附热力学的相关数据;采用XPS谱图进一步分析了FRL-g-PAA水凝胶对重金属离子的吸附机制。结果表明:在PAA水凝胶结构中引入糠醛渣木质素提高了水凝胶对重金属离子的平衡吸附容量,吸附体系pH值为5,降低温度有利于FRL-g-PAA水凝胶对Pb^(2+)、Cu^(2+)、Cd^(2+)重金属离子的快速、高效吸附;在K^+的干扰下,FRL-g-PAA水凝胶对重金属离子的平衡吸附量顺序是Pb^(2+)>Cu^(2+)>Cd^(2+);FRL-g-PAA水凝胶和PAA水凝胶吸附Pb^(2+)、Cu^(2+)、Cd^(2+)均遵循准二级动力学方程和弗兰德里希模型的自发放热反应;XPS谱图证明了FRL-g-PAA水凝胶的羟基和羧基与重金属离子之间存在络合作用,FRL-g-PAA水凝胶对Pb^(2+)、Cu^(2+)、Cd^(2+)吸附过程兼具物理吸附和化学吸附的特点。

A new lignin-g-polyacrylic acid hydrogel （ FRL-g-PAA hydrogel ） was made from furfural residue lignin and polyacrylic acid, and it can effectively remove Pb2＋, Cu2＋ and Cd2＋ from water. The absorption behavior of prepared FRL-g-PAA hydrogel was characterized by various methods, including effects of pH value, temperature and K＋ interfering ions on its equilibrium adsorption capacity. Adsorption kinetics, isotherm, thermodynamics and XPS spectra were used to analyze the adsorption mechanism of FRL-g-PAA. The results showed that grafting of FRL could help the composite hydrogel to enhance adsorption capacity of Pb2＋, Cu2＋ and Cd2＋ ions. When adjusting pH value to 5, temperature reduction was beneficial for rapid and efficient adsorption on heavy metal ions. Under the interference of K＋, the adsorption capability of FRL-g-PAA hydrogel was Pb2＋ 〉Cu2＋ 〉Cd2＋. The adsorption process followed the pseudo-second-order model and the spontaneous exothermic reaction of Freundlich model. XPS spectra further indicated that Pb2＋, Cu2＋ and Cd2＋ were adsorbed mainly by the hydroxyl group and carboxyl group of FRL-g-PAA hydrogel. The complexation between heavy metal ion and FRL-g-PAA hydrogel is synergistic effect of physical and chemical adsorptions.