Insights into the electrochemical degradation of triclosan from human urine: kinetics, mechanism and toxicity

Abstract Electrochemical degradation of triclosan in human urine was firstly studied by using Ti/SnO2-Sb/PbO2 anode doped with rare-earth elements. The results indicated that the Ti/SnO2-Sb/Gd-PbO2 anode demonstrated the best performance with the degradation rate constants being 0.095 min−1 in fresh urine and 0.045 min−1 in hydrolyzed urine at a current density of 10 mA cm−2. The electrochemical degradation was improved in the presence of phosphate and chloride, while the degradation was obviously inhibited by urea, bicarbonate and ammonia. Degradation mechanism mainly involved ether-bond cleavage, hydroxylation, cyclization, dehydrogenation and carboxylation. Quantitative structure-activity relationship model showed that ecological risks of cyclization products to fish, daphnid and green algae was higher than the parent compound, implying that the potential risks to aquatic organism should not be ignored before triclosan mineralized completely. Energy consumption for 90% triclosan degradation ranged from 4.5 to 47.8 Wh L−1, and the consumption increased along with the hydrolysis of urine. More than 390 tons triclosan can be eliminated from human urine per year around the world, which accounts for 26% of its annual production. The results indicate that electrochemical oxidation is a feasible and energy-saving technique to effectively remove triclosan from human urine.