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Our current study experimentally evaluates the impacts of surface hydrophilicity of supports on the properties of polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes. A series of “carboxylated polyethersulfone” (CPES) copolymers with an increasing “molar ratio” (MR) of carboxyl units were used to prepare supports with diverse surface hydrophilicities by the classical nonsolvent-induced phase separation (NIPS) method. Then, the PA-TFC NF membranes were finely fabricated atop these supports by conventional interfacial polymerization (IP) reactions. The linkages between the surface hydrophilicity of the supports and the characteristics of the interfacially polymerized PA layers as well as the permselectivity of NF membranes were investigated systematically. The morphological details of the NF membranes indicate that the growth of PA layers can be adjusted through increasing the surface hydrophilicity of the supports. Moreover, the separation results reveal that the NF membrane fabricated on the relatively hydrophobic support exhibits lower permeability (7.04 L·m−2·h−1·bar−1) and higher selectivity (89.94%) than those of the ones prepared on the hydrophilic supports (14.64~18.99 L·m−2·h−1·bar−1 and 66.98~73.48%). A three-stage conceptual scenario is proposed to illustrate the formation mechanism of the PA layer in NF membranes, which is due to the variation of surface hydrophilicity of the supports. The overall findings specify how the surface hydrophilicity of the supports influences the formation of PA layers, which ultimately defines the separation performances of the corresponding NF membranes.

Water‐in‐oil emulsions separation plays a critical role in industrial wastewater treatment. Membrane technology has attracted much interest in water‐in‐oil emulsions separation field for its excellent separation performance and facile processing method. However, versatile membrane with better solvent‐resistance is still absent in chemical industry. In this work, oxidized polyarylene sulfide sulfone (O‐PASS) membrane was severed as substrate, on which a hydrophobicity surface was built via coating of octadecyltrichlorosilane (OTS). And polydopamine (PDA) layer was employed and acted as connector between OTS and O‐PASS membrane due to its abundant active hydroxyl group. The maximum water contact angle was 132.6° indicating good hydrophobicity of the membrane. Finally, the OTS/PDA/O‐PASS composite membranes showed good separation performance for corrosive emulsions: the rejection and flux were 93.0% and 10.0 L/m2h for water‐in‐dichloromethane emulsions, and the rejection and flux were 92.3% and 34.6 L/m2h for water‐in‐n‐hexane emulsions. The OTS/PDA/O‐PASS composite membrane is a new candidate membrane for water‐in‐oil emulsions separation. In addition, the superior performance of the composite membrane under harsh environment conditions ensures its usefulness in resistance aggressive solvent.

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