Polyvinyl alcohol and methyl cellulose composite membrane for efficient degradation of methylene blue

Abstract

To resolve the challenges of difficult recovery and secondary pollution posed by powder catalysts in advanced oxidation processes (AOPs), cobalt/sulfur (Co/S) co-doped carbon-based powder catalysts are embedded into a composite membrane incorporating polyvinyl alcohol (PVA) and methyl cellulose (MC). The catalytic membrane is crosslinked via hydrogen bonding at an optimal PVA (10 wt% solution) to MC (2 wt% solution) volume ratio of 4:6 (P4) and cured at 130 °C. Meanwhile, P4 possessed superior methylene blue (MB) solution flux (954 L/m²h), swelling rate (221.9 %, 24 h), and elongation at break (2.02 %). P4 completed three filtration cycles within 10 min, achieving a MB degradation efficiency of over 99.5 %. This exceptional performance is attributed to the well-balanced hydrogen bonding crosslinking between PVA and MC in P4, which ensures uniform membrane morphology, enhanced mechanical properties, and optimal water flux. In contrast, samples with imbalanced ratios (e.g., P3 and P5) indicated that excessive PVA or MC triggered unilateral and intramolecular crosslinking (UI-crosslinking), ultimately causing non-uniform morphology, reduced mechanical strength, and diminished water flux. This work not only analyzes the effectiveness of Co/S co-doped catalytic membranes on MB degradation, but also explores the mechanism of how the PVA:MC ratio influences the membranes’ crosslinking, morphology, and mechanical properties. These findings present a promising approach for the efficient removal of organic dyes using catalytic membranes.