Bio-inspired deposition of polydopamine on PVDF followed by interfacial cross-linking with trimesoyl chloride as means of preparing composite membranes for isopropanol dehydration

Abstract

Polydopamine (PDA) simulates the adhesive properties of mussels and modifies the surface of hydrophobic materials. In this study, the mussel-inspired deposition of PDA on a polyvinylidene fluoride support was adopted. Afterward, the catecholamine in PDA was cross-linked with trimesoyl chloride (TMC). Attenuated total reflectance-Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy validated the success of the cross-linking process. Scanning electron microscopy illustrated that the cross-linking induced the reduction of nodules. Water contact angle measurements indicated that the cross-linked membrane exhibited a higher contact angle compared with the pristine membrane. Atomic force microscopy showed that the cross-linked membrane surface was smoother than that of the membrane without cross-linking. Pervaporation tests demonstrated that the cross-linked membrane could separate water from isopropanol. Several parameters were varied: dopamine concentration, buffer solution pH, self-polymerization time, TMC concentration, cross-linking time, and annealing time. At optimum conditions, the permeate flux was 2411 ± 33 g·m−2·h−1 and the water concentration in permeate was 95.72 ± 0.44 wt% (feed = 70 wt% isopropanol at 25 °C). At a feed temperature of 70 °C, the permeate flux was 11001 ± 989 g·m−2·h−1 and the water concentration in permeate was 93.61 ± 0.45 wt%. This indicates that a composite membrane containing cross-linked PDA is stable at a high feed temperature.