How solute-membrane interaction influences foulant formation in polymeric catalytic membrane: Competitive and sequential reactions

Abstract

Foulant-induced deactivation usually limits polymeric catalytic membrane performance, but the mechanisms governing foulant formation remain poorly understood. Recent research suggests that the interaction between solutes and the membrane plays a crucial role in foulant formation. This paper proposes a molecular theory to explain how reactant/product-membrane interactions influence foulant formation. This theoretical approach allows us to untangle the coupled competitive/sequential reaction–non-ideal diffusion phenomena in deactivating polymeric catalytic membranes. In other words, we include the reactant and product molecular information when describing their non-ideal reaction–diffusion behavior in confined polymeric environments; that is, they can interact (i) catalytically and (ii) non-catalytically with the membranes. We demonstrate how the non-catalytic reactant/product-membrane interactions control the partitioning process between the membranes and bulk solutions, allowing us to capture the formation of foulant locally and the global deactivation process. In our observations, we have found that attractive reactant-membrane interactions can enhance diffusion within the membrane, but this can come at the cost of reduced catalytic activity. Conversely, with the repulsive pair interaction, the reactants must overcome a more significant energy barrier to penetrate the membranes, simultaneously limiting the polymeric catalytic membrane performance and hindering foulant formation. In conclusion, our theory establishes a detailed understanding of reaction–diffusion phenomena governing foulant formation in polymeric catalytic membranes, considering the direct interaction between active reactants/products and reactive membranes.