Design principles of catalytic reactive membranes for water treatment

Reactive nanofiltration membranes integrate catalytic transformation with molecular separation to remove diverse aqueous contaminants. However, their development is hindered by an incomplete understanding of the interplay between solute mass transport and chemical reactions. Here we introduce key design principles by systematically evaluating their performance using a modelling approach. Efficient oxidant transport is essential for maximizing contaminant degradation. For membranes with surface-loaded catalysts, avoiding mass transport limitations ensures effective catalyst utilization, whereas for membranes with interior-loaded catalysts, optimizing oxidant partitioning enhances oxidant utilization efficiency. In addition, selective solute rejection reduces interference from natural organic matter, facilitating more selective contaminant transformation inside membrane pores. Consequently, contaminant transformation is dominated by surface-catalysed reactions at low permeate water fluxes, while interior-catalysed reactions dominate at high fluxes. However, rejecting both oxidants and contaminants does not enhance surface-catalysed treatment performance under an optimally designed scenario, highlighting the need for strategic design of membrane rejection. Beyond organic contaminant removal, nanofiltration membranes also minimize secondary contamination by rejecting the produced salts during the catalytic reactions. Furthermore, strategic selection of oxidant-catalyst pairs can enhance treatment performance by generating suitable reactive species. By establishing a theoretical framework for designing and optimizing reactive nanofiltration membranes, this study provides critical insights into the development of advanced water treatment technologies.