Bimetallic synergistic degradation of chlorophenols by CuCoOx–LDH catalyst in bicarbonate-activated hydrogen peroxide system

Abstract

Catalytic wastewater treatment is confronted by varied challenges like catalyst stability and efficiency in aqueous media due to the complex chemistry during organic compound degradation. Herein, we attempt to address this challenge by creating a synergistically stable and active bimetallic CuCoO_x–LDH catalyst via facile copper ion hydrothermal impregnation in a CoO_x–LDH catalyst. Different instrumental techniques like BET, XRD, FTIR, SEM, XPS and electrochemical studies etc. were conducted to investigate the properties of the catalyst before and after impregnation of copper ions. It was found that the changes in the electrochemistry and redox properties of the CuCoO_x–LDH catalyst based on cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS) appeared in the form of enhanced activity and excellent stability. In the bicarbonate activation of hydrogen peroxide (BAP) system, the synthesized CuCoO_x–LDH catalyst can efficiently degrade 200 ppm 4-chlorophenol (4-CP) with 84% COD and 78% TOC removal in less than 40 minutes, and even 1000 ppm of 4-CP in hours, while the CoO_x–LDH and CuO_x–LDH catalysts or their physical mixtures are apparently sluggish. This catalyst can also effectively degrade various substituted phenols including 2,4-dichlorophenol (DCP), 2,4,4-trichlorophenol (TCP), 2-chlorophenol (2-CP), phenol, and chlorobenzene with significant COD removal. The findings from fluorescence, scavengers, electron paramagnetic resonance (EPR), XPS, and electrochemical studies suggest collectively the generation of ˙OH, ¹O₂, and ˙O₂⁻ species and that the regeneration of active sites may be part of the degradation process. This approach based on CV, EIS and XPS studies has provided novel knowledge about the intrinsic origins of synergetic acceleration of catalyst activity.