A nanofiltration membrane fabricated on a surfactant activated substrate with improved separation performance and acid resistance

Abstract

An acid-resistant nanofiltration (NF) membrane with high permeability and rejection is of great significance. A NF membrane was prepared via interfacial polymerization with the assistance of surfactants, where three different common surfactants were used: sodium dodecyl sulfate (SDS), sodium lauryl sulfonate, and sodium dodecyl benzenesulfonate. The addition methods of SDS were optimized, with the results showing that using SDS to activate the substrate surface significantly affects the membrane performance. The surfactant was firstly deposited on a poly(ether)sulfone (PES) support layer prior to the interfacial polymerization of polyethyleneimine (PEI) and cyanuric chloride (CC) to form an active layer. The presence of SDS on the surface of the PES support membrane improves the retention of PEI in the process of the membrane preparation, thus affecting the morphology and cross-linking degree of the membrane, and ultimately affecting its performance. The NF membrane prepared under optimized conditions exhibits a water flux of 144.7 L m⁻² h⁻¹, while its rejection of MgCl₂ was 92.2%, with a decline in the rejection after one-month of acid soaking tests to give a value that is lower by 1.7%. The prepared NF membrane has good water flux and rejection properties, and exhibits long-term acid resistance.