A new submerged photocatalytic membrane reactor based on membrane distillation for ketoprofen removal from various aqueous matrices

The removal of ketoprofen from simulated sea, brackish and surface water as well as secondary effluent of a municipal wastewater treatment plant in a submerged photocatalytic membrane reactor (SPMR) coupling photocatalysis and direct contact membrane distillation was investigated. TiO2 photocatalyst was suspended in a feed. The investigations revealed almost complete photooxidation of ketoprofen (initial concentration of 10 mg·L−1) after 5 h, regardless of the matrix, and mineralization ranging from 19 to 56%. For comparison, ketoprofen mineralization in deionized water reached about 86%. No ketoprofen was found in distillate, however, the type of the feed affected the amount of total organic carbon (TOC) and total inorganic carbon (TIC). The highest TOC content in distillate was observed for the secondary effluent. The type of the aqueous matrix affected the concentration of dissolved oxygen in feed, which decreased to the highest extent in the case of surface water (61% after 5 h). The analysis of toxicity towards Aliivibrio fischeri revealed that regardless of the feed type the distillate was non-toxic. A slight increase of permeate flux was observed during the process compared to pure water flux which was explained in terms of thermal conductivity of the TiO2 layer on a membrane surface.