Photocatalytic mineralization of dimethoate in aqueous solutions using TiO2: Parameters and by-products analysis

Photocatalytic mineralization of dimethoate using nanosized TiO2 at different conditions has been investigated. The objective of this work was to study the influence on the photocatalytic mineralization of dimethoate, of various parameters and identify intermediates formed during photocatalytic treatment. The mineralization efficiency of dimethoate increased with elevated concentration of humic acid up to 5 mg/L, while the efficiency reduced when the concentration was above 5 mg/L due to competitive adsorption. The presence of CH3COCH3 can significantly inhibit dimethoate mineralization and the half-life of mineralization efficiency was increased by about 3 times. The photo mineralization efficiency changed with increasing concentrations of inorganic ions. With respect to the ions of Fe3+, Cu2+, Zn2+, HCO3− and NO3−, the mineralization efficiency increased with increasing concentration of ions and reached a maximum at optimal concentrations, which was followed by a decrease with a further increase in ion concentrations. By contrast, the mineralization of dimethoate was strongly inhibited by Cl− and Cr3+ ions. Intermediate products from dimethoate were identified by means of GC–MS and four possible by-products were identified. A proposed mineralization pathway for dimethoate is presented.