Advanced electrochemical treatment of tetracycline-contaminated water using Pt/Ti electrodes

Abstract

The electrochemical mineralization of tetracycline in chloride aqueous solutions using Pt/Ti anodes has been investigated. The mineralization process, oxidation efficiencies and oxidation products were characterized by UV-visible spectroscopy and HPLC-MS. Tetracycline oxidation efficiencies are 97 ± 2% in 0.64 wt% HCl and 85 ± 3% in 0.64 wt% NaCl within 15 minutes of electrolysis. UV-visible spectroscopy confirmed the degradation of the antibiotic's π-conjugated electron system and allowed the identification of active species (i.e., hydrogen peroxide and dissolved chlorine) that can potentially degrade tetracycline. The formation of these active species is due to the high positive potential of the Pt/Ti anode during electrolysis. HPLC-MS studies show the intensity of the tetracycline peak to gradually decrease during electrolysis, indicating its oxidation. Peaks corresponding to oxidation intermediates with a molecular weight above 70 were not detected, which indicates the absence of oxidation products with higher molecular mass. During electrochemical oxidation of tetracycline, small amounts of formaldehyde are formed, but its concentration can be brought to an acceptable level by diluting the solution. In negative mode, chlorate ions were detected in the NaCl solutions, which are likely formed from the stepwise oxidation of chloride ions; however, this phenomenon is not observed in HCl solutions.