Inner-selective coordination nanofiltration hollow fiber membranes from assist-pressure modified substrate

This study aims to develop an inner selective coordination nanofiltration hollow fiber (CNHF) membrane for the efficient removal of antibiotics from groundwater. In the first step, a modified substrate with the controlled modification degree is achieved by pressure-assisted alkali modification of polyimide hollow fiber substrate to provide the active points for the construction of the dense active layer. Then, the high-performance active layer is dynamically built on the modified substrate by the coordination between Fe³⁺ and phytic acid. Compared to static synthesis, the pure water permeability (PWP) of the membrane is improved from 4.1 to 8.5 Lm⁻²h⁻¹bar⁻¹ and Na₂SO₄ rejection enhanced from 68.3% to 97.0% by the dynamic synthesis with a cross-flow system. The newly developed membranes exhibit high rejection to several pharmaceuticals (>99%). This work may provide insightful guidelines for improving the fabrication procedures and scaling up the inner-selective CNHF membrane modules for water purification and other applications.