纤维素甲基丙烯酸酯水凝胶的制备及重金属离子吸附性能研究

Study on Preparation of Cellulose Methacrylate Hydrogels and Their Adsorption Performance of Heavy Metal Ions

水体和土壤是生态环境健康安全发展的基础,重金属含量超标则严重污染了土壤和水体,对人体健康和生态环境构成威胁。具有高吸附性的凝胶材料通过重金属高吸附性及多孔性将水体和土壤中重金属离子富集于自身中,实现水体和土壤中重金属离子的有效去除。以杨木木粉中提取的纤维素为原料,利用离子液体在均相条件下通过酯化反应合成可溶于二甲基亚砜的纤维素甲基丙烯酸酯(CM)。以CM为原料,首先通过碳碳双键交联制备了CM有机凝胶。然后通过巯基-烯点击化学反应分别将3-巯基丙酸(MA)和L-半胱胺盐酸盐(CH)接枝到CM有机凝胶中的未反应碳碳双键上,制备了2种分别具有羧基或氨基活性吸附基团CM基水凝胶,分别命名为CM-MA和CM-CH。在化学结构与形貌分析基础上,系统研究了2种水凝胶对重金属离子的吸附性能,并对其吸附机理进行了探究。研究结果表明,在本研究选用的6种重金属离子,CM-MA水凝胶对Pb2+吸附效果最好,最大吸附量可达148.44 mg/g。CM-CH水凝胶对Hg2+展现出优异的特异性吸附性能,最大吸附量为112.55 mg/g。2种水凝胶对重金属离子的吸附均属于单分子层的化学吸附,吸附动力学模型更符合准二级吸附动力学模型。本研究不仅为重金属污染的处理提供一条有效途径,同时实现了农林废弃物的高值化利用,对资源利用和环境保护具有一定的指导意义。

Water and soil are the basis for the healthy and safe development of ecological environment. Heavy metal content exceeding the standard will seriously pollute the soil and water and pose a threat to human health and ecological environment. Gels with high adsorption ability can enrich heavy metal ions from water and soil through their high adsorption ability and porosity, and effectively remove heavy metal ions in water and soil. In this paper, cellulose methacrylate(CM) soluble in dimethyl sulfoxide was synthesized from cellulose extracted from poplar wood by esterification reaction with ionic liquid under homogeneous conditions. Using CM as raw material, CM organogels were prepared by cross-linking carbon and carbon double bonds. Then, 3-mercaptopropionic acid(MA) and L-cysteamine hydrochloride(CH) were grafted to the unreacted carbon-carbon double bond in CM organic gel by thiol-ene click reaction, respectively. Two kinds of CM hydrogels with carboxyl or amino active adsorption groups were prepared, named CM-MA and CM-CH, respectively. On the basis of chemical structure and morphology analysis, the adsorption properties of two hydrogels for heavy metal ions were systematically studied, and their adsorption mechanism was explored. The results showed that among the six heavy metal ions selected in this study, CM-MA hydrogel had the best adsorption effect on Pb2+, and the maximum adsorption capacity can reach 148.44 mg/g. The CM-CH hydrogel showed excellent selective adsorption performance for Hg2+, and the maximum adsorption capacity was 112.55 mg/g. The adsorption of heavy metal ions by the two hydrogels belonged to monomolecular chemisorption, and the adsorption kinetics model was more consistent with the quasi-second-order adsorption kinetics model. This study not only provides an effective way for the treatment of heavy metal pollution, but also realizes the high-value utilization of agricultural and forestry wastes, which has certain guiding significance for resource utilization and environmental protection.