Reduction and Removal of Chromium VI in Water by Powdered Activated Carbon
Department of Environmental Science & Engineering, Fudan University, 220 Handan Road, Shanghai 200433, China
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, China
Author to whom correspondence should be addressed.
Materials 2018, 11(2), 269; https://doi.org/10.3390/ma11020269
Received: 18 January 2018 / Revised: 31 January 2018 / Accepted: 7 February 2018 / Published: 9 February 2018
(This article belongs to the Special Issue Green Activated Carbons)
Cr adsorption on wood-based powdered activated carbon (WPAC) was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The highest Cr(VI) adsorption (40.04%) was obtained under acidic conditions (pH 3), whereas Cr removal at pH 10 was only 0.34%. The mechanism of Cr(VI) removal from aqueous solutions by WPAC was based on the reduction of Cr(VI) to Cr(III) with the concomitant oxidation of C-H and C-OH to C-OH and C=O, respectively, on the surface of WPAC, followed by Cr(III) adsorption. Raman spectroscopy revealed a change in the WPAC structure in terms of the D/G band intensity ratio after Cr(VI) adsorption. SEM-EDS analysis showed that the oxygen/carbon ratio on the WPAC surface increased from 9.85% to 17.74%. This result was confirmed by XPS measurements, which showed that 78.8% of Cr adsorbed on the WPAC surface was in the trivalent state. The amount of oxygen-containing functional groups on the surface increased due to the oxidation of graphitic carbons to C-OH and C=O groups.