Porous Polymeric Membranes Doped with Halloysite Nanotubes and Oxygenic Polyoxometalates

Endowing anti-fouling capabilities to water treatment membranes is a key feature for their long lifetime, but it continues to be a challenging task. Herein, a strategy for preparing composite membranes is reported comprising halloysite nanotubes (HNTs) as scaffolds to support a ruthenium substituted polyoxometalate (Ru4POM), with the goal of using evolved O2, resulting from the Ru4POM-catalyzed H2O2 dismutation, as anti-fouling agent. Two different amino alkyl derivatives, that is, a phosphonate and a silane, are grafted, respectively, in the lumen and on the surface of HNTs to support Ru4POM, and the resulting hybrid nanostructures are compared, in terms of catalytic efficiency and stability, to establish the most promising membrane additive. Porous polyether sulfone-based membranes are thus prepared to obtain a first proof of concept for this doping strategy. With respect to the former Ru4POM-containing membranes, HNTs provide Earth-abundant and low-cost scaffolds for their efficient dispersion in the polymeric matrix. Preliminary tests on permeability and anti-fouling behavior are finally discussed.