Removal of herbicide 1-chloro-2,4-dinitrobenzene (DNCB) from aqueous solutions by electrochemical oxidation using boron-doped diamond (BDD) and PbO2 electrodes

Abstract

The electrochemical removal of the 1-chloro-2,4-dinitrobenzene (DNCB) herbicide, a potentially carcinogenic agent from aqueous solutions, was performed at PbO2 and BDD electrodes by bulk electrolysis under galvanostatic control (300 and 400 A m−2) and under two pH conditions (3 and 9). Results clearly indicated that a 62 % of mineralization was achieved with BDD anode at pH 3, while only a 46 % of electrochemical oxidation (EO) was achieved at PbO2 electrode. The mineralization current efficiency (MCE) depended on the electrode material, current density, and pH conditions; but, for both PbO2 and BDD, high MCE was achieved at pH 3 and 300 A m−2, obtaining 2.54 % and 1.99 % for BDD and PbO2, respectively. The EO pathway depended on the electrocatalytic properties of each one of the anodes to produce hydroxyl radicals which attacked the DNCB molecule as well as the deactivating effects of the chlorine and nitro groups attached to the aromatic ring on the DNCB structure. Finally, HPLC analyses also showed that phenolic intermediates as well as carboxylic acids were formed, at a different extent, during the electrolysis process on both electrodes.