Development of photocatalytic titanium dioxide membranes for degradation of recalcitrant compounds

BACKGROUND: Immobilization of TiO₂ photoactive nanoparticles on a nanofiltration membrane without loss of permselectivity properties is currently a challenge. In this study, immobilization of TiO₂ nanoparticles on a ceramic commercial membrane surface by direct current reactive magnetron sputtering was addressed. The best membrane was compared with an unmodified membrane and a membrane modified by a generic chemical–physical method in terms of membrane permselectivity and photocatalytic properties. RESULTS: Magnetron sputtering was able to achieve similar photocatalytic activity to the chemical–physical method, where Evonik P25 TiO₂ nanoparticles were used, while maintaining membrane rejection and permeability. The layer formed by magnetron sputtering exhibits uniformly distributed nanostructured columns, aligned perpendicularly to the membrane surface. Furthermore, the membrane hydrophilicity increase achieved is promising for fouling control. A shorter sputtering time and distance between the titanium target and the membrane were preferable to effectively degrade the pesticides diuron and chlorfenvinphos. Under optimum sputtering conditions, 95% and 78% increases were attained for the degradation of diuron and chlorfenvinphos, respectively, compared with the unmodified membrane. CONCLUSION: The photocatalytic membranes developed are potential candidates for the simultaneous retention and photocatalytic degradation of recalcitrant micropollutants. However, if the purpose is to retain low molecular weight molecules, retentive properties should be improved.