Mechanism and Process Optimization in the Electrooxidation of Oxalic Acid Using BDD Electrode under Nitric Acid Environment

Various electrochemical tests were carried out to elucidate the electrolytic oxidation mechanism of oxalic acid on a boron-doped diamond electrode in a nitric acid environment. These included cyclic voltammetry, AC impedance, constant current electrolysis, and electron paramagnetic resonance spectroscopy. The impact of electrode potential, current density, nitric acid concentration, and electrode plate spacing on the oxidation of oxalic acid was investigated. In the electrolysis mechanism, indirect oxidation of^{· •}OH plays a major role and direct oxidation at the electrode plays a minor role. Excessive nitric acid concentration will reduce the electrooxidation rate of oxalic acid. The optimal process conditions for electrolyzing oxalic acid are obtained as follows: the plate spacing is 2 cm, and the current density is 60 mA cm^-2. Finally, the BDD electrode can electrolyze the oxalic acid concentration to below 0.001 mol/L, which can meet the process requirements.