Submerged photocatalytic membrane reactor utilizing ultrafiltration for ketoprofen removal from surface water

Abstract

The investigations on the removal of a nonsteroidal anti-inflammatory drug – ketoprofen from a synthetic surface water containing humic acid (HA) in a new submerged photocatalytic membrane reactor (SPMR) coupling photocatalysis and ultrafiltration are presented. The treated water circulated between a feed tank equipped with an ultrafiltration membrane and a labyrinth flow photoreactor irradiated with UVA radiation. TiO2 suspended in the feed (0.5–1.5 g L−1) was used as a photocatalyst. A positive influence of aeration on ketoprofen decomposition was observed. The investigations revealed a 75% degradation of the drug (initial concentration of 10 mg L−1) after 5 h of the SPMR operation at 1 g TiO2 L−1 and 14 NL min−1 of air flow rate. The concentration of dissolved oxygen during aeration remained on a constant level, while in the absence of bubbling decreased by almost 40% during 5 h of the process. No improvement of mineralization in the presence of aeration was observed, which was attributed to a slow degradation of complex HA molecules and their desorption from the photocatalyst under the action of air bubbles. A positive effect of the bubbling on membrane fouling mitigation was proved. The permeate flux in the absence of aeration decreased by 35%, while in the case of air flow rate of 7 and 14 NL min−1 - by 20% only. The efficiency of membrane cleaning using NaOCl solution was dependent on operational parameters of the membrane in SPMR. In 5 subsequent cycles a complete flux recovery after the cleaning was obtained for the membrane operated at -0.05 bar.