Removal of protein, histological dye and tetracycline from simulated bioindustrial wastewater with a dual pore size PPSU membrane

Abstract

Wastewater from production of active pharmaceutical ingredients (APIs) often contains proteins, azo dyes or antibiotics, which cause severe water eutrophication and growth of drug-resistant bacteria. A series of polyphenylsulfone (PPSU) membranes was prepared to determine the relationships between pore structures and the abilities of different membranes to separate foulants, and the characteristics and performance of the ultrafiltration membranes were investigated. The structure of the skin layer and the cross-sectional texture were converted from dense and finger-like macrovoids to porous sponge shapes because of a delayed liquid–liquid (L-L) demixing time. Formation of novel PPSU membranes via noncovalent bonding interactions was evaluated, and this selectively affected the membrane surface pore structure, layer thickness, surface polarity and electronic repulsive force. All PPSU membranes demonstrated excellent rejection of organic foulants, including bovine serum albumin (BSA) (~100% rejection) and acid red 1 (AR1) (~90% rejection). Additionally, M5 provided an excellent tetracycline (TC) rejection efficiency of 89% in the 1st cycle. Due to the small size of TC, pore size effects were displayed. Moreover, the pure water flux recovery rate (FRR) increased from 85% (M1, water/ethanol: 100/0) to 99.9% (M4, water/ethanol: 30/70) after BSA filtration because the weak nonsolvent decreased the roughness of the membrane surface, and the membrane made with added EtOH yielded excellent FRR values (99.9%) after AR1 filtration. Therefore, PPSU membranes successfully achieved over 90% rejection of organic foulants and excellent FRRs, indicating that they may be suitable for purifying wastewater from API plants that generate organic foulants with a wide range of sizes.