Polyethylene based nanofiltration membranes with internally confined polyamide separating layers from cross substrate interface polymerization

Abstract

Cross substrate interface polymerization (CSIP) processes were developed to construct polyethylene (PE) based thin film composite nanofiltration (NF) membranes with internally confined polyamide (i-PA) separating layers protected by external covering PE filaments, possessing rougher top surfaces, more negative surface zeta potential, reduced and narrowly distributed pore sizes. Cationic surfactant CTAB reacted with TMC and formed hydrophilic but insoluble BTC(CTA)_n/CTAB coating inside the PE substrate to facilitate water permeation. The contact time of monomer solutions on PE substrates affect the membrane performance by controlling the quality of i-PA layers and amount of BTC(CTA)_n/CTAB coating underneath. PE(O/W) NF membranes from CSIP processes with i-PA layers had rougher surface, lower zeta potential, smaller average radius μ_p (0.374 nm) and lower geometric deviation (1.43), leading to higher Na₂SO₄ rejection (96.4 %) and water permeance (20.36 L m⁻²·h⁻¹·bar⁻¹), maintaining excellent anti-wearing, flux recovering and operating stability.