Activated carbon fiber-supported nano zero-valent iron on Cr(VI) removal

Abstract

Nanoscale zero valent iron (nZVI) was adsorbed on activated carbon fiber (ACF) for efficient removal of hexavalent chromium. The composite materials were characterized by XRD, SEM, FTIR, BET and XPS. Fe2+ was adsorbed by ACF and then restored by NaBH4. This sample was named ACF-nZVI-a. While Fe2+ was restored by NaBH4 and nZVI was adsorbed by ACF. That sample was named ACF-nZVI-b. BET analysis indicated that ACF-nZVI-a had a high specific surface area of 1087 m2/g, while ACF-nZVI-b had a low specific surface area of 928 m2/g, which indicated that it was easier for nZVI to go into the ACF pores than ionic condition Fe2+. Batch experiments showed that Cr (VI) removal rate was 98.9% for ACF-nZVI-b, which was higher than that for both ACF (33.7%) and ACF-nZVI-a (50.7%). Furthermore, the removal rate of Cr (VI) by ACF-nZVI-b showed strong dependence on initial solution pH. Low pH and initial Cr (VI) concentration favored both removal efficiency and rate constants. The reaction followed a pseudo first-order model under different initial Cr (VI) concentrations. The Cr (VI) removal was attributed to both the adsorption of ACF and the reducibility of nZVI, but the main cause was the reduction of nZVI. This study demonstrated that the ACF-nZVI-b had the potential to become an effective agent for the removal of Cr (VI) from polluted water.