Can we reversely filtrate the catalytic membrane when treating algae-laden water?

Abstract

During catalytic membrane filtration, algal cells and macromolecules in environmental aqueous conditions load on the surface of the catalytic material, leading to progressive deactivation of the catalytic membrane. Here, we synthesized catalytic membranes with outstanding water flux by anchoring catalyst (δ-MnO2 and sulfur-doped g-C3N4) on homoporous base membranes and immobilizing them by PIP-TMC interfacial polymerization. And the reverse filtration was used to pre-remove the hard-to-degrade foulings such as algal cells to enhance the degradation performance and antifouling performance of the catalyst membrane. The presence of reverse pre-filtration endowed the catalytic membrane to obtain 1.5 times higher water flux than normal filtration, reducing the contact of foulings with the catalyst and improving the catalytic efficiency and stability. Therefore, the operating conditions of the catalytic layer were optimized to obtain higher degradation rates and maintain long-term catalytic activity compared to normal filtration. Also, in the treatment of algae-laden water, reverse filtration allowed algal cells to be separated due to pore size sieving and catalytic material space, avoiding cell fragmentation and release of extracellular polymers caused by activated generated reactive oxygen species. In the catalytic removal of the refractory pollutants (APAP and SMX), the SK25 membrane was able to remove 100 % of the performance with degradation rates up to 0.36 mol·L−1·s−1. This study proposes a novel strategy for catalytic membrane filtration and promotes the application of catalytic membrane filtration technology in practical environmental problems.