Nanocomposite material from TiO2 and activated carbon for the removal of pharmaceutical product sulfamethazine by combined adsorption/photocatalysis in aqueous media

This work was dedicated to the elaboration of new composite materials based on activated carbon and titanium oxide as an ecological solution for the cleaning of water contaminated with pharmaceutical pollutants. Such new composite materials allowed the combining of adsorption and photocatalytic process, which allows a cleaning process that is low cost making them promising materials. The functionalization of the surface of activated carbon (AC) by TiO2 nanoparticles forms the core of the nanocomposite material. This was accomplished using sol-gel process with molar ratios R-n (n(Ti)/n(AC)) in the range of 1/10 to 7/10 followed by a calcination step (400 degrees C, N-2, 2 h). Using various characterization techniques, AC surface functionalization was confirmed and the formation of a TiO2 coating on the AC was noticed with TiO2 under its unique anatase crystallographic form. The study of adsorption and photocatalytic degradation of the sulfamethazine antibiotic demonstrated that the most photoactive nanocomposite corresponds to the one with R-n = 0.5. Freundlich model was proved to be a perfect fit with the experimental results stating that the adsorption is of multilayer nature on the surface of the adsorbent and with interactions between the pollutants adsorbed on its surface. The photocatalytic degradation of the remaining pharmaceutical pollutant in the solution was evidenced and essentially occurred through the involvement of hydroxyl radicals formed by the excitation of the photocatalyst. The formation of the photoproducts analyzed by the LC/MS technique implies the splitting of the sulfonamide bridge, and by the hydroxylation of the aromatic ring and the pyrimidine group.