Kinetics of catalytic ozonation of oxalic acid in water with activated carbon

The ozonation kinetics of oxalic acid in water in the presence of an activated carbon has been investigated at acid pH. The presence of the activated carbon significantly enhances the degradation rate of oxalic acid if compared to single ozonation and single adsorption. According to total organic carbon measurements, nearly complete mineralization of oxalic acid can be achieved depending on the experimental conditions. The presence of tert-butyl alcohol, which scarcely adsorbs on the carbon surface at the conditions investigated, led to a significant reduction of the oxalic acid removal rate. Consequently, experimental results suggest that the reaction proceeds in the water phase between oxalic acid and oxidant species, likely hydroxyl radicals, coming from the ozone decomposition on the carbon surface. The proposed mechanism yielded a first-order kinetics with respect to ozone, close to the 0.8 order experimentally observed. Also, the energy of activation was found to be approximately 15 kcal mol(-1).