Achieving high separation of cephalexin in a photocatalytic membrane reactor: What is the best method for embedding catalyst within the polysulfone membrane structure?

Abstract

The aim of this study is to achieve the best performance for the photocatalytic membrane reactor (PMR) in cephalexin removal. To this end, SrTiO3 photocatalyst with the bandgap of 2.85 eV and crystalline size 50 nm is embedded in the membrane structure using four methods, including blending with membrane matrix (BM), photograft polymerization (GP), interfacial polymerization (IP) and spin coating (SC). Investigation the PMR performance shows that, due to high porosity (68 %), the maximum drug flux (371 L/m2h) passes through the BMi membrane. Because of high flux, BMi membrane suffers from high fouling where presence of SrTiO3 can reduce it by at most 6 %. On the other hand, presence of SrTiO3 across the IPi surface, because of high surface area for performing photocatalytic degradation reactions, causes reduction of membrane fouling by 69 % compared to the raw membrane. The largest share of cephalexin membrane separation (80 %), due to the minimum MWCO (660 g/mol), is related to SCi membrane and the greatest share of the cephalexin photocatalytic degradation (59 %) as the shortest bandgap (3.19 eV) is associated with the GPi membrane. Overall, the highest rate of cephalexin removal (membrane separation plus photocatalytic degradation) is reported for SCi membranes, followed by IPi, GPi and BMi membranes, respectively. Hence, in order to achieve high flux, BMi; low fouling, IPi; high photocatalytic degradation, GPi and high separation, SCi membrane are suggested. Given the challenge ahead of any type of catalytic reactor, the proper method should be chosen for embedding the catalyst within the membrane structure.