Facile zwitterionization of polyvinylidene fluoride microfiltration membranes for biofouling mitigation

Styrene maleic anhydride (SM) is a commercially available copolymer able to react with diamines. The ring-opening reaction results in the formation of a zwitterionic compound of prime interest to the development of fouling-resistant membranes. To this end, we designed microfiltration antifouling polyvinylidene fluoride (PVDF) membranes by blending PVDF with a copolymer obtained from the reaction of SM with N,N-dimethylamino-1,3-propanediamine, and then by inducing phase inversion of the casting solution from the vapor phase. The resulting membranes possess excellent surface and bulk hydrophilicity, compared to the pristine membrane. Besides, as adding copolymer shifts the zeta potential closer to electroneutrality, biofouling is alleviated, as tested in static conditions with Escherichia coli, blood cells or bovine serum albumin. Filtration of a bacterial solution also demonstrated the superior performances of the as-prepared membrane to those of a commercial hydrophilic PVDF membrane, with a higher flux recovery ratio (90% vs. 65%) and lower irreversible flux decline ratio (10% vs. 32%). Given also the stability of the design and the low costs involved in the making of the membranes (all materials are commercially available and inexpensive), the present membranes are suitable alternatives to commercial hydrophilic PVDF membranes, but with better fouling mitigation.