膨胀石墨负载零价铁的合成及其对水中Pb(II)去除效果与机制

以网络状孔型结构发达的膨胀石墨(EG)为载体, 采用化学沉积法制备负载零价铁(ZVI)的膨胀石墨(EG-ZVI)。利用SEM、XRD、FT-IR及XPS等对负载及反应前后的EG-ZVI进行表征, 探索了EG-ZVI对铅离子(Pb(II))的处理效果并对其反应产物及机理进行了分析。结果表明: 亚微米级ZVI成功负载到EG表面; 相比ZVI, EG-ZVI对Pb(II)的去除能力提升明显; EG-ZVI去除Pb(II)主要是吸附和还原作用的共同结果, 该过程符合一级动力学模型, 且控制步骤为化学反应过程。其还原过程是由负载在EG表面的ZVI腐蚀提供电子还原Pb(II)生成铅单质, 并进一步生成铅氧化物与氢氧化物; EG-ZVI能弥补ZVI在反应过程中生成惰性层导致去除效率低的不足, 使其在Pb(II)废水的实际修复中具有较高的应用前景。

Performance and Mechanism of Pb(II) Removal by Expanded Graphite Loaded with Zero-Valent Iron

Zero-valent iron (ZVI) loaded onto expanded graphite (EG) as a composite material (EG-ZVI) was prepared through chemical deposition method to remove lead ion (Pb(II)). EG-ZVI was characterized by XRD, SEM, FTIR and XPS. Results indicated that the EG was successfully loaded with sub-micron scale zero-valent iron, and showed that the removal rate of Pb(II) by EG-ZVI was 1.43 fold of that by ZVI. Galvanic cell effect and high specific surface area are the main reasons for enhancing removal of Pb(II) by EG-ZVI. The removal process mainly involved chemical reduction and physical adsorption which was well fitted the first-order kinetic model. XPS analyzing showed that the removed Pb(II) was reduced to Pb and then generated its oxides. In addition, EG-ZVI could overcome the shortcomings of forming undesirable precipitation of ferrous hydroxide on the surface when applied ZVI. These data indicate that EG-ZVI has high potential to remove Pb(II) in wastewater due to its high removal capability and stability.