Heterogeneous photocatalytic degradation of pharmaceuticals in water by using polycrystalline TiO2 and a nanofiltration membrane reactor

Abstract

A study of the photodegradation of different pharmaceuticals [furosemide, ranitidine (hydrochloride), ofloxacine, phenazone, naproxen, carbamazepine and clofibric acid] in aqueous medium at various pHs by using a batch photoreactor and a photocatalytic membrane reactor working in recirculation regime was carried out. Polycrystalline TiO2 was used as the photocatalyst, and different membranes (NTR 7410, PAN GKSS HV3/T, N 30 F, NF PES 10) were tested. A different adsorption of the substrates onto the catalyst surface was observed owing to the hydrophilic/hydrophobic character of the catalyst, depending on the pH. The photodegradation of the seven molecules in the batch reactor was successfully carried out and the behaviour was in accordance with pseudo-first order kinetics. Furosemide and ranitidine were selected to carry out the study of rejection and photodegradation in the hybrid membrane system. The permeate flux of the treated water was in the 31.5–60.0 L/(h m2) range for NTR 7410 membrane, whereas rejection values in the range 10–60% for furosemide and 5–30% for ranitidine in the dark (without photoreaction) were found. The degradation in the hybrid membrane photoreactor showed that the photocatalyst was retained by the membrane in the reaction ambient, while the membrane rejection towards the pollutants was not very satisfactory. A net decrease of the rejection down to 0 was observed in the contemporary presence of light, photocatalyst and oxygen.