Kinetic and mechanistic aspects of ultrafiltration membrane fouling by nano- and microplastics

The mechanical and chemical breakdown of plastic litter increases the release of nano- and microplastics, which have the potential to impact the performance of membranes processes used in water treatment plants. In this work, the extent of fouling of a commercial ultrafiltration poly(sulfone) membrane induced by nano- and microplastics ranging from 13 to 690 nm in size was investigated. The cross-flow filtration of the plastic particles over 48 h at a 1 bar pressure reduced the permeate water flux by 38% compared to pure water filtration. Over 25% of the nano- and microplastics initially present in the feed were absorbed onto the membrane surface within the 48 h of filtration. Particulate fouling mechanism was sequentially modelled into intermediate and complete pore blockage, followed by cake layer formation. Hydrophobic interactions and surface repulsion forces were found to dictate the adsorption rate of the nano- and microplastics onto the membrane surface. This work opens the understanding of NPs/MPs interactions with water filtration processes and demonstrates the need to develop solutions limiting the impact of NPs/MPs on current treating units.