Titania nanocomposite polyethersulfone ultrafiltration membranes fabricated using a low temperature hydrothermal coating process

Thin mesoporous coatings of TiO2 nanoparticles were developed for in-house and commercial PES membranes of varying pore sizes using a low temperature hydrothermal (LTH) approach. Titania sol–gel particles were dip-coated onto membrane substrates, followed by heat and UV treatments to extract the residual organic templates. Dip-coating parameters such as drying and holding time, dipping and withdrawal velocities, and the number of coating cycles were varied to optimise the microstructure and surface properties of the coating. Coated membranes exhibit a dual level hierarchical roughness and hydrophilicity which was maintained without continuous UV illumination. The organic templating agent (Pluronics F127) enhanced adhesion of the particles; however the heat treatment collapsed some pores in the tighter ultrafiltration membranes. Results showed that the coatings were mechanically robust and photoactive. Passive protein adsorption was reduced significantly on the TiO2 coated surfaces. Filtration performance of coated and uncoated 500 kDa membranes was also investigated with humic acid as a model foulant, and an increase in flux recovery was observed during multiple fouling and cleaning cycles with the titania coated membrane. The LTH approach provides a platform for further surface functionalization of polymeric membranes to generate photoactive coatings, tuneable hydrophilicity, low fouling surfaces and novel surface architecture.