Water treatment: Degradation of dimethoxybenzenes by the titanium dioxide‐UV combination

Abstract

Abstract Three dimethoxybenzenes (DMBs) have been chosen to further assess the capabilities of the TiO2‐UV system to destroy substituted aromatic pollutants in water. At λ > 290 nm and pH = 3, the disappearance of DMB (0.145 mM) is much more rapid in the presence of TiO2 (Degussa P‐25; 2.5 g/L) than by direct photolysis; the intermediates generated by both processes are different. At λ > 340 nm, which avoids any significant contribution of direct photolysis, the order of disappearance is meta > para > ortho. Possible origins for this order are discussed. The main aromatic intermediates correspond to the hydroxylation of the ring with or without the elimination of one or both methoxy groups, and to the para and ortho orientations. From 1, 4‐DMB, para‐benzoquinone is also formed. The temporal variations of 2, 3‐dimethoxyphenol (2, 3‐DMP), 3, 4‐DMP, 2‐methoxyphenol (2‐MP) and 3‐MP have been recorded. At their maximum concentrations, these intermediates correspond to only a few percents of degraded DMB and th...