Co-doped ZnO catalyst for non-thermal atmospheric pressure pulsating corona plasma degradation of reactive dye

Abstract

Reactive dyes in water are difficult to degrade due to their high stability. Plasma processes have a high potential for the degradation of dyes. In this work, Co-doped ZnO was prepared by electrodeposition and used as a catalyst for the degradation of RO 16 dye by non-thermal, positive pulsating corona discharge at atmospheric pressure. The catalytic mechanism and new insight into the interactions that enable the plasma catalysis were provided. The catalyst was characterized by cyclic voltammetry, SEM/EDX, XRD, FTIR, and BET. Doping with Co did not change the ZnO crystal structure, but caused slight changes in the lattice parameters, reduced the band gap, and increased the specific surface area. Co-doped ZnO improved the decolorization rate and energy yield by 17- and 21-fold, respectively. The dye degradation was caused by strong oxidizing agents generated in the plasma, mainly •OH radicals. Co-doped ZnO promoted the production of •OH radicals. The assumed catalytic mechanism, the role of the catalyst in the degradation reactions, and the degradation pathway were proposed. The decolorization rate and TOC removal were still high, but slightly lower in river water than in deionized water.