In-situ generation of anti-fouling TpPa/PVDF membranes showing excellent photocatalytic degradation and self-cleaning for dyes in water

Abstract

Covalent organic frameworks (COFs) have been widely studied in membrane separation technology due to their high porosity, high specific surface area, and tunable pore size. However, COF particles tend to aggregate in blend membranes. In this study, in-situ generation of 2,4,6-Triformylphloroglucinol p-Phenylenediamine (TpPa) was carried out in Polyvinylidene fluoride/N,N-dimethylacetamide (PVDF/DMAc), followed by nonsolvent-induced phase separation (NIPS) method to obtain TpPa/PVDF membranes. The introduction of hydrophilic TpPa resulted in improved hydrophilicity and increased roughness of the membrane. During the filtration of dyes including Methylene Blue, Congo Red, and Eriochrome Black T, the TpPa/PVDF membrane exhibited high rejection rates (>90 %) and improved permeation flux (6–8 times of the original PVDF membrane). Investigation of its photocatalytic ability revealed that the TpPa/PVDF membrane exhibited excellent photocatalytic degradation of dyes, making it suitable for self-cleaning of fouled membranes and allowing for multiple reuse (up to 8 times). In the 6-cycle filtrations of Bovine Serum Albumin (BSA) and Humic Acid (HA), the membrane showed not only high rejection and permeation but also superior flux recovery rate (FRR), indicating good anti-fouling ability. This study has achieved efficient treatment of dye wastewater through membrane separation technology and has provided a novel anti-fouling COFs-modified membrane with photocatalytic self-cleaning ability.