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

doi:10.15541/jim20170157

Abstract

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

CLC Number:

X703

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.

Figures/Tables 9

Fig. 1 XRD patterns of EG and EG-ZVI

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

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

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

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

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

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

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

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

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