Increasing Oil Fouling Resistance of PVDF Microfiltration Membranes Via Surface Modification Using Polydopamine Combined with Hyperbranched Polyol

In the face of climate change, reclaiming freshwater from oil-in-water emulsions produced by
industrial processes has become an area of increasing interest. Membrane-based filtration
techniques offer an efficient solution for filtering these emulsions. Hydrophobic poly(vinylidene)
fluoride (PVDF) membranes are widely used for their superior chemical, mechanical, and thermal
properties in filtration applications compared to hydrophilic membranes. However, the inherent
hydrophobicity of these polymers often causes membrane fouling: the adsorption and deposition
of oil-droplets and surfactants onto the surface and within the pores of membranes. This work aims
to modify the surface of PVDF membranes using polydopamine (PDA) with reduced pore
blockage, which is accomplished in the presence of hyperbranched-polyol BoltornTM H40 (HBP,
H40) creating an oil-fouling-resistant surface. It is hypothesized that polymerizing dopamine in
the presence of hyperbranched-polyol controls PDA aggregate size while creating an effective
fouling-resistant surface with reduced pore blockage. Using scanning electron microscopy (SEM),
it was observed that modifying PVDF membrane surfaces with PDA in the presence of H40
resulted in larger surface pores and higher surface porosity, in contrast to membrane surfaces
bearing the PDA layer alone. The PDA and PDA/H40 modifications of the surface of PVDF films
resulted in a significant decrease in the water contact angle of the film surface, indicating improved
hydrophilicity. The deposition of polydopamine in the presence of H40 demonstrated a remarkable
boost in the separation of oil from water in tight oil-in-water emulsion while displaying high
resistance to fouling over multiple runs versus unmodified and PDA modified PVDF membranes.