Removal of triclosan by conductive-diamond electrolysis and sonoelectrolysis

BACKGROUND: Removal of triclosan by conductive-diamond electrochemical oxidation (CDEO) and sonoelectrochemical oxidation (CDSEO), either in methanol/water or methanol solutions is studied in the range of concentration 0.1 to 100 mg dm3. Effects of current density and of electrolyte on the process efficiency are assessed. RESULTS: Concentration of triclosan can be removed below the detection limit of HPLC. In methanol/water solutions, there are two stages: a rapid decrease in the concentration and a less efficient process in which the rate is slower. In methanol solutions, experimental results clearly fit first-order kinetics. Mediated oxidation plays a significant role. Electrolyses in sulphate media are more efficient than in chloride media and the second low-rate stage in methanol/water solution appears for higher triclosan removal. The main intermediates are catechol, chlorohydroquinone, 4-chlorocatechol, acetic acid and dichloroacetic acid. They were only detected during the electrolysis of highly concentrated solution, suggesting a very energetic oxidation. CONCLUSIONS: CDEO and CDSEO are very efficient for the removal of triclosan. CDSEO improves mass-transfer processes and gives a more efficient removal at lower concentrations. The removal of methanol is improved significantly, in spite of its concentration being well over the limiting value for mass transport control. The reaction sequence for triclosan mineralization is consistent with literature reports. (c) 2012 Society of Chemical Industry