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

Abstract In this study, the roles of polycarboxylates in synergistic Cr(VI) reduction and organic pollutant oxidation are investigated in glow discharge electrolysis (GDE). H 2 O 2 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 [H 2 O 2 ] 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.