Electrochemical removal of antibiotics from wastewaters

Electro-oxidation tests with different anodes (Ti/Pt, DSA^® type, graphite and three-dimensional (3D) electrode made of a fixed bed of activated carbon pellets) were performed on aqueous solutions containing the antibiotics Ofloxacin and Lincomycin. The effectiveness of the treatment of wastewater containing pharmaceuticals was assessed, as well as the electro-oxidation mechanism. The use of high electrode potentials (>2.8 V versus NHE) ensured either significant anodic surface activation or minimization of fouling by in situ generated polymeric material. The use of a membrane-divided cell showed positive aspects in terms of molecule demolition, and average power consumption. The electro-oxidation was found to occur with first order kinetics mainly at anode surface when using Na₂SO₄ at low concentration (0.02N). Under these conditions, Ofloxacin is efficiently oxidized over all tested anodes (e.g. 50 mgcm^-2 A^-1 h^-1 for the bi-dimensional Ti/Pt electrode), whereas Lincomycin is oxidized with slow overall kinetics mainly due to difficult deprotonation, a step that precedes the primary electron transfer stage of the oxidation process. The three-dimensional electrode would be the most appropriate for continuous industrial-scale process. However, at the used potential, unacceptable corrosion of the carbon based electrode was noticed.