Modification of hydrophobic commercial PVDF microfiltration membranes into superhydrophilic membranes by the mussel-inspired method with dopamine and polyethyleneimine

Polymeric membranes have not been widely used to treat oily wastewater due to their susceptibility to fouling. The aim of the present work is to develop a low-cost, facile modification technique to achieve superhydrophilicity and fouling resistance of hydrophobic PVDF membranes in oil-water separation applications. PVDF microfiltration membranes with 0.1, 0.2 and 0.45 µm pore size were modified with mixtures of different concentrations of dopamine (DA) and polyethyleneimine (PEI) using different deposition times (6, 12 and 24 h). The modified membranes were characterized for their surface physicochemical properties, pH tolerance, and performance in filtration of a model oil emulsion. The PDA/PEI coating was shown to produce superhydrophilic membrane surfaces with very high oil rejection (>98% with 1 µm nominal pore size), and greatly reduced irreversible fouling by oily wastewater. The excellent oil rejection and fouling resistance is attributed to the hydration water layer formed by the PDA/PEI coating both on the membrane surface and inside membrane pores.