Liu Qi, Zang Guo-Long, Zhao Quan
Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University No. 92 Weijin Road, Nankai District Tianjin 300072 China
RSC Adv. 2021 Jul 27;11(42):25880-25891. doi: 10.1039/d1ra04156h.
Copper is widely present in the natural environment and inevitably poses a risk to both human health and the natural environment. Biochar is an inexpensive, clean and sustainable sorbent material that can be used as a resource for copper removal, and there is interest in new ways to chemically treat biochar to tune its unique properties and modify its atomic structure. In this study, biochar was oxidized, and then polyethyleneimine (PEI) modified chitosan and carboxylated biochar were economically compounded through a multicomponent Ugi reaction to effectively remove Cu(ii). PEI enhances the adsorption of Cu(ii) within an optimum solution pH range of 3.5-5.5. The adsorption process follows a pseudo-second-order kinetic model. When the dosage of BC-NH2 was 4 g L and the temperature was 303 K, the maximum adsorption capacity calculated by the Langmuir model was 26.67 mg g. The adsorption process of Cu(ii) on BC-NH2 was heat-trapping and spontaneous. BC-NH2 showed good selectivity for K and Mg, and BC-NH2 desorbed by NaOH showed better adsorption performance than HSO in the adsorption-desorption cycle. Characterization by SEM, EDS, BET, FTIR, TGA and XPS showed successful coupling and that the amide group of BC-NH2 had chelated with Cu(ii). This atomically economical multicomponent Ugi reaction provides a new option for preparing composite materials that effectively remove heavy metals.
铜广泛存在于自然环境中，不可避免地对人类健康和自然环境构成风险。生物炭是一种廉价、清洁且可持续的吸附剂材料，可作为去除铜的资源，人们对通过化学方法处理生物炭以调节其独特性能和改变其原子结构的新方法很感兴趣。在本研究中，对生物炭进行氧化处理，然后通过多组分乌吉反应将聚乙烯亚胺（PEI）改性壳聚糖与羧化生物炭进行经济复合，以有效去除Cu（II）。PEI在3.5 - 5.5的最佳溶液pH范围内增强了对Cu（II）的吸附。吸附过程遵循准二级动力学模型。当BC-NH2的投加量为4 g/L且温度为303 K时，通过朗缪尔模型计算的最大吸附容量为26.67 mg/g。Cu（II）在BC-NH2上的吸附过程是吸热且自发的。BC-NH2对K和Mg表现出良好的选择性，在吸附 - 解吸循环中，用NaOH解吸的BC-NH2比HSO表现出更好的吸附性能。通过扫描电子显微镜（SEM）、能谱仪（EDS）、比表面积分析仪（BET）、傅里叶变换红外光谱仪（FTIR）、热重分析仪（TGA）和X射线光电子能谱仪（XPS）表征表明复合成功，且BC-NH2的酰胺基团已与Cu（II）螯合。这种原子经济的多组分乌吉反应为制备有效去除重金属的复合材料提供了一种新选择。
