Polydopamine modification of high-performance PVDF ultrafiltration membranes prepared by the combined crystallisation and diffusion (CCD) method

Polyvinylidene fluoride (PVDF) membranes produced by the recently developed combined crystallisation and diffusion (CCD) method have a magnitude higher in pure water fluxes than those produced via the conventional membrane manufacturing technology. However, in the research so far, most of the PVDF CCD membranes are hydrophobic, easy to be fouled in filtration applications. Herein, we apply the popular polydopamine (PDA) modification technique to improve the hydrophilicity of PVDF CCD membranes to ensure that their high permeation performance is maintained even in foulant-rich environments. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) analysis were used as characterisation techniques to understand the dynamics of the PDA deposition process. The results showed that an increase in modification time does clearly improve the membrane surface hydrophilicity, but suffers in its permeability, as an inevitable consequence of the increased pore blockage by the deposited PDA layer. Because of this, even in the fouling studies, the sample modified for a shorter duration (2 h) and not longer duration (12 h or 24 h) showed the best overall permeation performance. The permeation results from the fouling study present PDA-modified PVDF CCD membranes as promising alternatives to many of the well-established industry-standard membranes.