Demineralization of Oxalic Acid Solutions by Anodic Oxidation in a Stirred Tank Electrochemical Reactor: Experimental and Modeling Study

This study investigates the anodic oxidation of oxalic acid (OA) in wastewater by focusing on a stirred tank electrochemical reactor with a low-cost lead anode. The reactor design, which features a circular array of vertical lead cylinders, aims to enhance the current distribution and mass transfer. Response surface methodology (RSM) is employed to systematically explore the impact of the impeller rotation speed, current density, and initial OA concentration on the efficiency of OA removal. The investigation reveals that impeller rotation speed and current density significantly influence OA removal, while the initial OA concentration exhibits opposing effects. Notably, the study emphasizes the crucial role of contact time and reveals its significant influence on the overall process kinetics and adherence to first-order kinetics. The study also considers the role of sulfate ions in enhancing the electrochemical mineralization of OA. The derived empirical model provides insights into the interplay of operating parameters in influencing the oxidation kinetics. Additionally, the study employs RSM to optimize OA removal efficiency; in ideal circumstances, 96% of the acid was eliminated within a time frame of 2 h. Electrical energy consumed during electrolysis ranged from 2 to 11.4 kWh/kg contingent upon the specific operational parameters. The findings contribute to the design of efficient and environmentally friendly wastewater treatment processes for OA removal in diverse industrial applications. The merits of the present reactor compared with the traditional parallel plate cell are outlined.