Removal of the drug procaine from acidic aqueous solutions using a flow reactor with a boron-doped diamond anode

This article reports the electrochemical advanced oxidation treatment of 2.5 L of acidic aqueous solutions with 0.320 mM of the drug procaine hydrochloride in 0.050 M Na2SO4 using a pre-pilot flow plant. This was equipped with a cell, containing a boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 generation, which was connected to an annular photoreactor with a 160 W UVA lamp for the study of photoelectro-Fenton (PEF) process. Poor degradation and mineralization was attained by electrochemical oxidation with electrogenerated H2O2 due to the limited attack of both, hydroxyl radical (OH) formed at the BDD surface from water oxidation and H2O2 on organic matter. The electro-Fenton process became more effective thanks to the simultaneous oxidation with OH formed from Fenton's reaction in the presence of Fe2+. The most powerful process was PEF because of the additional photolysis of photoactive intermediates by UVA radiation. This method allowed achieving 91% mineralization after 360 min of electrolysis at 33.3 mA cm−2. The effect of current density and drug concentration on PEF performance was examined. The mineralization current efficiency and energy consumption were determined for each treatment. Two N-containing derivatives were identified by gas chromatography-mass spectrometry. The quantification of generated carboxylic acids revealed that the final solution in PEF was composed of a mixture of acetic and formic acids