Towards improved protein anti-fouling and anti-microbial properties of poly (vinylidene fluoride) membranes by blending with lactate salts-based polyurea as surface modifiers

It is a big challenge to develop membrane fouling-resistant materials for long-term water filtration applications in order to reduce the operating cost. Herein, for the first time, we have proposed the utilization of lactate salts-based polyurea additives as surface modifiers (SMs) to endow anti-microbial and anti-protein activities which increase the life of poly (vinylidene fluoride) (PVDF) membrane filters in terms of attaining anti-fouling properties for prolonged and stable water flux in water treatment. Membrane fouling was examined by taking into account the important influencing factors such as surface hydrophilicity and functional lactate groups present on the surface. The results showed that the surface hydrophilicity was enhanced leading to higher water flux of the PVDF membrane blended with sodium lactate-based polyurea (Na-PVDF) (174.2 L m⁻² h⁻¹), which was almost 12 times higher than that of the neat PVDF membrane. The fabricated SMs-blended PVDF membranes displayed satisfactory rejection and fouling resistant performance for the bovine serum albumin (BSA) molecules. The PVDF membrane blended with zinc lactate-based polyurea (Zn-PVDF) ensured effective anti-microbial activity against bacteria and fungi. Besides, the SMs-blended PVDF membranes displayed a higher zone of inhibition (ZOI) and higher colony reduction than the neat PVDF membranes in the anti-microbial test. The long-term water filtration test carried out after 200 days showed that PVDF membranes blended with SMs retained more than 90% of the original water flux, suggesting the long-term stability of SMs in the PVDF matrix. Therefore, the synergistic effect of SMs can be considered as an important life enhancer of polymeric membrane materials in the field of membrane technology.