Simultaneous removal of Cr(VI) and phenol by persulfate activated with bentonite-supported nanoscale zero-valent iron: Reactivity and mechanism

Abstract

The applicability of bentonite-supported nanoscale zero-valent iron (B-nZVI) as a catalyst to activate persulfate (PS) for the simultaneous removal of Cr(VI) and phenol was systematically investigated in this study. Experimental results demonstrated that phenol degradation was significantly enhanced under acidic condition and with oxygen supply, whereas the Cr(VI) reduction was not obviously declined. The removal efficiencies of Cr(VI) and phenol in B-nZVI/PS combined system were 99.8 and 72.3%, respectively. Cr(VI) reduction and phenol oxidation was simultaneously achieved in B-nZVI/PS combined system, which provided a promising environmental treatment for industrial wastewater containing metal ions and organic compounds. An acidic condition was more favorable to the decomposition of persulfate for the production of sulfate radicals. Radical scavenging tests revealed that the predominant reactive oxygen species for phenol degradation was SO4(-), neither HO nor O2(-). A reaction mechanism, which involves the Cr(VI) removal mainly by the reduction of nZVI and the degradation of phenol mainly by the SO4(-) from the decomposition of persulfate, was proposed. These findings revealed that B-nZVI/PS combined system has a potential in the environmental remediation polluted jointly by organic compounds and/or heavy metals.

Keywords: Cr(Ⅵ); Fenton-like process; Nano zero-valent iron; Phenol; Synergistic effect.