Preparation of PVDF composite membrane reinforced by conductive knitted fabric

Polyvinylidene fluoride (PVDF) membrane prepared by nonsolvent-induced phase separation generally has low mechanical strength and is easily fouled. In this work, the PVDF membranes with enhanced mechanical strength, water flux, and significant electrical conductivity were prepared using conductive knitted fabrics with different stitch densities or construction types as the supporting matrix. The polyester fibers as the sheath yarn increased the peel strength between the composite layers to 3.4 N·cm−1. The interlock stitch fabric with a bending depth of 70 increased the composite membrane's high tensile strength to 12.7 MPa (i.e., 70.6 times higher than that of the original PVDF membrane). Compared to the PVDF membrane, this composite membrane exhibited a rejection rate of 76.1% and a water flux of 194.6 L·m−2·h−1 (i.e., enhanced 27.1 times). After 12-hour, 3 cycles of continuous filtration, the water flux of the composite membrane was reduced slightly by about 1.9%, which compared favorably to that of the PVDF membrane (i.e., reduced by 19.7%). Besides, the stainless-steel as the core yarn also gave the PVDF membrane good electrical conductivity (ρs = 272.7 Ω). This work highlights the potential of developing reinforced hydrophobic membranes using conductive knitted fabric to generate a robust filtration membrane for water treatment.