Catalytic and photocatalytic ozonation with activated carbon as technologies in the removal of aqueous micropollutants

Clopyralid degradation by different treatment processes combining olive stone activated carbon (OSAC), ozone and Solar-Simulated Radiation (SSR) were studied. Firstly, a detailed study of clopyralid adsorption onto OSAC was carried out. The fitted experimental data suggest pseudo-first order kinetics and Freundlich equilibrium isotherm models to describe the process. Secondly, the application of catalytic ozonation was explored. The combination of ozone and OSAC significantly improved the generation of hydroxyl radicals. Moreover, the catalyst showed higher stability and kept efficiency in reuse cycles, if compared to adsorption. Thirdly, the combination of O-3, OSAC, and SSR was applied, and different systems were compared, focusing on pH as the main variable. At basic pH (pH = 9), the best removal rate was achieved by O-3/OSAC/SSR. Finally, all systems were applied for the treatment of the target compound in an urban wastewater matrix, focusing on the effect of inorganic carbon. The presence of carbonates inhibited only the mineralization rate, not affecting the compound removal.