Interfacial design of support substrate for a continuous mesophase-templated active layer with adjustable pore size

Abstract

Nano-porous active layers templated by hexagonal lyotropic liquid crystal (HLLC) offer a continuous water pathway, rendering them promising for membrane separation applications of high performance. The surface properties, such as surface roughness, hydrophilicity and pore size, of commercially available ultrafiltration membranes usually need to be optimized to better support the active layer. Here, we apply a facile yet potent thermal treatment process to a polyacrylonitrile ultrafiltration (UPAN) substrate and form a continuous HLLC separation layer. The enhancement in water filtration performance is largely influenced by the surface roughness of the substrates. As the temperature increases, the UPAN substrates become rougher due to approaching the glass transition temperature of polyacrylonitrile. This leads to a denser HLLC active layer with smaller pores. For the membranes treated at a temperature of 100 °C, their water flux reaches 17 L/m2h, which is 10 times higher than that of the membranes treated at 85 °C, and the PEG4000 rejection increases by almost 50 % from 42 % to 59 %. This heat treatment process offers a novel approach to fabricate mesophase-templated active layers with adjustable pore sizes, thus advancing membrane separation techniques.