The effect of the sp3/sp2 carbon ratio on the electrochemical oxidation of 2,4-D with p-Si BDD anodes

Boron-doped diamond films on silicon substrates (p-Si BDD) with different sp(3)/sp(2) carbon ratios are systematically varied in electrodes used to oxidize 2,4-dichlorophenoxyacetic acid (2,4-D) in synthetic wastewater containing chlorides. 2,4-D is completely mineralized during the electrolysis. A higher sp(3)/sp(2) ratio in the anode results in a more rapid and efficient oxidative removal of 2,4-D. Chlorinated compounds such as 4-chlororesorcinol, 2-chlorophenol, and 2,4-dichlorophenol form as intermediates during the oxidative treatment. Although these compounds are completely depleted during the electrolysis, their maximum observed concentrations decrease as the sp(3) content increases in the anode. On the contrary, higher maximum concentrations are observed for non-chlorinated intermediates, especially hydroquinone, and there is a greater formation of chlorates and perchlorates in chloride-containing solutions as the sp(3) content increases in the anode. (C) 2015 Elsevier Ltd. All rights reserved.