Ultrasonic assisted in-situ synthesis of photocatalytic ZnO on PVDF membrane surface for fouling degradation

Animal carcasses can be harmlessly treated through high-temperature and high-pressure hydrolysis, resulting in the production of bioactive polypeptides. The polypeptides can be effectively separated from other impurities by ultrafiltration (UF) membranes technology. However, membrane fouling is inevitable during filtrating process, which significantly impacts their lifespan and economic efficiency. In this study, the photocatalyst ZnO nanoparticles on the PVDF membrane surface (PVDF/Zn) were fabricated to degrade foulant. Firstly, tannic acid (TA) was blended into the membrane to provide coordination sites to fix Zn²⁺. Then, ZnO nanoparticles was synthesized exclusively on the membrane surface under ultrasonic assistance, where the ultrasonic energy generated by the cavitation bubbles was excluded by the pore size. Chemical composition and morphology characterization were conducted to prove the successful synthesis of ZnO on the membrane surface. The PVDF/Zn membrane demonstrated a flux of 42 L m⁻²h⁻¹ and a rejection of 97 % when filtering BSA solution, with a flux recovery rate (FRR) of 80 % after photocatalytic degradation. During the treatment of high-temperature and high-pressure hydrolyzed animal carcass solution (HHAS), the FRR exceeded 90 %, effectively separating impurities from polypeptides. This work provides a novel approach to enhancing the efficiency of treating HHAS and offers new insights into the preparation of photocatalytic membranes.