Polyethylene-supported nanofiltration membrane with in situ formed surface patterns of millimeter size in resisting fouling

Abstract

Membrane surface properties play important roles in determining the rate and severity of membrane fouling. This paper reported an innovative nanofiltration (NF) membrane called PENF which had a poly(piperazine-amide) active layer formed on a polyethylene (PE) support layer. The PENF membrane was very attractive in that millimeter-sized surface patterns could be automatically formed by the pressing effect of applied pressure for which permeate spacer acted as the in situ imprinter. This was attributed to the thin and tough PE support layer, which could be easily deformed under the applied pressure for NF applications. The surface-patterned PENF membrane (PENF-P) demonstrated greatly enhanced resistance to organic, inorganic and scaling fouling as well as combined fouling, when compared to either the original PENF membrane or commercial NF membranes like NF270. Without surface patterns, the PENF membrane along with other NF membranes followed a same general rule in resisting membrane fouling; a more hydrophilic NF membrane was generally more resistant to fouling. Membrane integrity breaches caused by surface deformation and patterning were negligible in terms of glucose rejection and water permeability coefficient. The PENF-P membrane could reject glucose by >80% at an applied pressure of 3.5 bar and had a water permeability coefficient of >11 L/m2/h/bar. A continuous running of a small-size spiral-wound element of the membrane (0.85 m2) for over 3000 h confirmed that the PENF membrane had a long-time consistently high performance in terms of water permeation and solute rejection. The innovative PENF membrane and the involved surface patterning technique are expected to have a bright application prospect for water treatment and wastewater reclamation.