Cationically modified membranes using covalent layer-by-layer assembly for antiviral applications in drinking water

In this work, a new approach towards virus reduction is taken, where modified membranes with large pore sizes (>450 nm) can reach high log10-unit virus reductions. Polyelectrolyte coatings were used to modify microfiltration (MF) membranes to impart antiviral properties. A stable covalent layer-by-layer (LBL) approach was used to create multilayers from a single polyelectrolyte, polyethyleneimine (PEI). Here terephthalaldehyde (TA) crosslinking was used to create crosslinked multilayers, both on model surfaces and on commercial polyether sulfone, (PES) MF membranes. The substrates were further coated with antiviral silver, and copper nanoparticles (Ag and CuNPs) stabilised with PEI. The specific fabrication during the LBL assembly was stepwise characterised using multi-surface analysis including Fourier transform infrared spectroscopy (FTIR), Atomic Force Microscope (AFM), ellipsometry, zeta potential and contact angle measurements. Model surfaces demonstrated a 4 log10-units reduction of MS2 viral titre, independent of the crosslinked PEI layer thickness. The crosslinked PEI and Ag/CuNPs-modified membranes efficiently reduced 4.5–5 log10-units of infectious MS2 bacteriophages by both adsorption and inactivation of viral particles. This was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR), which showed a stable performance over time. Pure water flux measurements on modified-membranes showed good long-term stability. Thus, 5000 L/m2 of virus-free water was produced in approximately 2 h, using gravity-based filtration. Furthermore, there was no observable leaching of nanoparticles from the membranes during filtration.