Aliphatic polyketone-based thin film composite membrane with mussel-inspired polydopamine intermediate layer for high performance osmotic power generation

Polydopamine (PDA), formed from self-polymerization of dopamine, was coated on aliphatic polyketone membrane substrate prior to interfacial polymerization (IP), preparing a pressure retarded osmosis (PRO) thin film composite (TFC) membrane with a PDA interlayer. The effect of the formation of two types of PDA interlayers - smooth and particulate - on substrate morphology, polyamide formation, and PRO osmotic performance were investigated. Also, the effect of pH on the particulate PDA interlayer was studied. It was found that the introduction of both smooth and particulate PDA contributes to enhanced water flux and power density of the PRO membranes. pH was found to have significantly affected the formation of particulate PDA and the polyamide formation, as well. At higher pH, PDA self-polymerization led to the formation of more nanoparticles, the subsequent increase in surface roughness and decline in the polyketone substrate porosity. The particulate PDA interlayer formed looser polyamide, compared to the thinner and denser polyamide formed on pristine and smooth PDA-interlayer-coated TFC membranes. The membrane performance was evaluated using deionized water and 1.0 M NaCl as feed and draw solutions, respectively. The TFC membrane with nanoparticulate PDA layer formed at pH 9.0 exhibited the best initial water flux of 40.8 L m-2 h-1, and this membrane also showed the highest power density of 17.1 W m-2 at 25 bar. The results of this study indicate that nanoparticulate PDA interlayer formation is a simple and scalable TFC membrane development method for engineered osmosis.