Catalysts to improve the abatement of sulfamethoxazole and the resulting organic carbon in water during ozonation

Sulfamethoxazole (SMX), one pharmaceutical compound, has been treated in aqueous solutions with catalysts (copper and cobalt type perovskites and cobalt–alumina) and promoters (activated carbons). Hydrogen peroxide and saturated carboxylic acids were identified as intermediates. The effects of adsorption and pH have been investigated. Removal of the starting SMX accomplished with ozone alone is a fast process but catalytic or promoted ozonation is needed to significantly reduce the resulting organic carbon. SMX is, thus, mainly removed through direct ozone reaction while hydroxyl radical oxidation is the mechanism of removal the remaining TOC. The kinetics of the process has also been investigated. Perovskite catalytic ozonation resulted to be a chemical control process and apparent rate constants for homogeneous and heterogeneous ozonation were determined. For activated carbon ozonation, external diffusion of ozone to solid particles controlled the process rate.