Regulation of dopamine forward osmosis membrane via inorganic salt and macro-porous substrates for pharmaceutical concentration

Abstract

Dopamine (DA) with good designability could self-polymerize into polydopamine (PDA) with various polymerization states in alkaline solution. However, the poor structural controllability of PDA leads to serious PDA hyper-polymers, making DA difficulty to be used as sole aqueous phase monomer during conventional interfacial polymerization (IP) for membrane preparation. In this work, the organic solvent forward osmosis (OSFO) membranes were fabricated via substrate-floating interfacial polymerization (SFIP) method with DA as sole aqueous phase monomer and macro-porous polyether sulfone (PES) membrane with pore size of 0.1–0.22 μm as substrates. Inorganic salt such as NaCl was employed as aqueous phase additive, which not only effectively regulated the oligomeric polymerization state of PDA but also promoted DA diffusion. The macro-porous substrate could enlarge the reaction contact area and relieve the internal concentration polarization in support layer. The resulting OSFO membranes exhibited an excellent ethanol flux of ∼10.70 L m−2 h−1 and lower reverse LiCl flux of ∼0.53 g m−2 h−1, as well as a high tetracycline concentration efficiency of >15 % for 1 h run whatever the tetracycline concentration in the feed (500–2000 mg/L). This work provides new insights into the fabrication of high-performance OSFO membrane for solvent recovery and pharmaceutical concentration.