Electrochemical destruction of thiourea dioxide in an undivided parallel plate electrodes batch reactor

The paper presents the results of a study on the electrochemical destructio n of pollutants present in a spent reducing bath of a textile factory. The investigations comprised the electro-oxidation of thiourea dioxide (TUD) (t he main component of the reducing bath), sulphites and urea, which are form ed during oxidation of TUD. The study performed in an undivided cell parall el plate electrodes reactor, using eight different anode materials under va rious hydrodynamic conditions, proved that electro-oxidation can be success fully applied for treatment of spent reducing baths. The best results of TU D and SO32- electro-oxidation were obtained with a Ti/Pt electrode, which s howed electrocatalytic effect for both the compounds, indicating a possibil ity of their direct electro-oxidation on the anode. Destruction of TUD and SO32- proceeded also via indirect electro-oxidation, mediated by chlorine e volved on the anode. The process kinetics was mass transport controlled til l Re = 5000. No electrocatalytic effects were observed for urea with any of the tested anode materials. The elimination of urea resulted to proceed on ly by indirect electro-oxidation, mediated by chlorine. For elimination of urea a Ti/Pt-Ir electrode proved to be the best anode, probably due to its high efficiency in electro-oxidation of chlorides into chlorine. (C) 2001 E lsevier Science B.V. All rights reserved.