Micellar Effect on the Catalytic Co-Oxidation of Dimethyl Sulfoxide and Oxalic Acid by Chromium(VI) in Aqueous Acid Media: A Kinetic Study

Dual enhancement-inhibition roles of polycarboxylates in Cr(VI) reduction and organic pollutant oxidation in electrical plasma system

In this study, the roles of polycarboxylates in synergistic Cr(VI) reduction and organic pollutant oxidation are investigated in glow discharge electrolysis (GDE). H2O2 generated in GDE plays a primary role for Cr(VI) reduction, and the presence of polycarboxylates can significantly enhance the reduction of Cr(VI) to Cr(III) with less value of [H2O2](consumption)/[Cr(VI)](reduction). Simultaneously, polycarboxylates inhibit the production of ·OH via chromium-based Fenton-like reaction, leading to the retarded oxidation of other pollutant oxidation, i.e., RhB. The formation of peroxochromate(V) is a requisite both for Cr(VI) reduction to Cr(III) and ·OH formation via Fenton-like reaction. Polycarboxylates can form complexes with peroxochromate(V), which can transform to Cr(III) spontaneously, thereby interrupting the pathway for additional ·OH production. These influences induced by polycarboxylate were found closely relative to the number and position of -OH group in polycarboxylates. Besides, 162.7 mg L(-1) Cr(VI) in actual electroplating effluent can be rapidly and almost completely reduced in GDE with introducing polycarboxylate containing nickel electroplating effluent. Generally, the present study provides a versatile strategy for Cr(VI) reduction, exhibiting a bright application future for real wastewater treatment.