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

doi:10.15541/jim20170157

摘要/Abstract

摘要：

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。

关键词: 铁-膨胀石墨复合材料, 铅离子, 去除性能, 去除机理

Abstract:

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.

Key words: EG-ZVI, lead ion, removal performance, removal mechanism

中图分类号:

X703

徐从斌, 杨文杰, 孙宏亮, 刘伟江, 杨苑钰, 林爱军. 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[J]. 无机材料学报, 2018, 33(1): 41-47.

XU Cong-Bin, YANG Wen-Jie, SUN Hong-Liang, LIU Wei-Jiang, YANG Yuan-Yu, LIN Ai-Jun. Performance and Mechanism of Pb(II) Removal by Expanded Graphite Loaded with Zero-Valent Iron[J]. Journal of Inorganic Materials, 2018, 33(1): 41-47.

图/表 9

图1 EG负载ZVI前后的XRD图谱

Fig. 1 XRD patterns of EG and EG-ZVI

图2 EG负载ZVI前后的FT-IR光谱图

Fig. 2 FT-IR spectra of EG and EG-ZVI

图3 不同理论ZVI负载量下EG的SEM照片

Fig. 3 SEM images of EG with different nominal ZVI mass ^(a) 0 g ZVI/gEG; (b) 0.50 g ZVI/gEG; (c) 1.50 g ZVI/gEG; (d) 3.00 g ZVI/gEG

图4 理论ZVI负载量对Pb(II)去除效果的影响

Fig. 4 Effect of nominal ZVI mass on the removal of Pb(II)

图5 溶液初始pH对Pb(II)去除效果的影响

Fig. 5 Effect of initial pH on the removal of Pb(II)

表1 各级动力学常数拟合结果

Table 1 Kinetic parameters for the removal of Pb(II) by EG-ZVI

Kinetic model	k/((mg·L)^1-ⁿ·min^-1)	R²
First-order model	0.0771	0.9885
Second-order model	0.0053	0.9450
Third-order model	0.0005	0.9340

图6 反应温度对Pb(II)去除效果的影响

Fig. 6 Effect of temperature on the Pb(II) ^removal Inset is plot of lnk versus 1/T on reduction kinetics of Pb(II)

图7 EG-ZVI反应前后XPS图谱

Fig. 7 XPS spectra of the EG-ZVI^(a) Fe2p before Pb(II) removal; (b) Fe2p after Pb(II) removal; (c) Pb4f after Pb(II) removal; (d) O1s after Pb(II) removal

图8 EG-ZVI去除Pb(II)的机理图

Fig. 8 Proposed mechanism of Pb(II) removal in water by EG-ZVI

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