Photoelectrolysis of clopyralid wastes with a novel laser-prepared MMO-RuO2TiO2 anode

Abstract This paper studies the applicability of a novel laser-prepared mixed metal oxide (MMO-RuO2TiO2) anode in the photoelectrochemical degradation of clopyralid, a toxic and biorefractory herbicide. Results are compared to those obtained using the well-known boron-doped diamond (BDD) anode and demonstrate that, although the electrolysis with diamond is more effective than that obtained with the new electrode, the irradiation of UVC light makes the novel MMO material more effective in chloride media. It was explained in terms of the homolysis of hypochlorous acid/hypochlorite to form chloride and hydroxyl radicals. Photoelectrochemical degradation with MMO produced a marked synergistic effect in TOC removal, especially in the presence of chloride ions. On the contrary, for the BDD anode, at the tested conditions, antagonisms were found in both sulfate and chloride media. These important synergisms allows finding conditions in which the novel anode can be competitive with the BDD.