Catalytic activity of a composite metal electrode catalyst for the degradation of real dyeing wastewater by a heterogeneous electro-Fenton process

Abstract

CuO-ZnO-Pr2O3-La2O3-zeolite (CZPLz) were employed for electro-Fenton (CZPLz-electro-Fenton) degradation of real dyeing wastewater in an electrochemical reactor with an steel electrode cathode and a titanium ruthenium iridium electrode anode. A variety of metal oxide catalyst particles were synthesized by an impregnation method with zeolite as the carrier under the following conditions: different load materials, different doping ratios, different calcination temperatures, and different calcination times. The obtained heterogeneous catalysts were used to treat real dyeing wastewater using the electro-Fenton process in a fluidized bed and were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrode-gradation of real dyeing wastewater was performed at 30 V for 60 min. The dyeing wastewaters were analyzed by UV–vis spectrophotometry and the potassium dichromate method. The maximum decolorization ratio was 91.21%, and the maximum COD removal efficiency was 61.1%, and these values were obtained for a composite metal electrode catalyst for which the CuO, ZnO, Pr2O3 and La2O3 amounts were present at a ratio of 50:25:2:20 at 600℃ for 3 h. After 5 cycles of using the composite metal electrode catalyst, the decolorization ratio of the real dyeing wastewater was 86.67%. Therefore, it can be concluded that the catalyst under the optimum process parameters can be used many times. Additionally, it was confirmed that Cu2+/Zn2+/Pr3+/La3+ cations were successfully substituted in the zeolite, giving rise to the changes in the catalytic activity of the catalyst observed by XRD and SEM analyses of the composite metal electrode catalyst. Hence, the results of this experiment could establish a theoretical foundation for industrial applications.