Styrene-acrylonitrile (SAN) nanofibrous membranes with unique properties for desalination by direct contact membrane distillation (DCMD) process

Abstract

In this work, novel, nanofibrous styrene-acrylonitrile (SAN) membranes were fabricated via the electroblowing technique. The dope solution (22.5 wt% SAN polymer in N,N-dimethylformamide) was electroblown at three times (30, 45 and 60 min) with the rate of 270 μL.min-1. Nanofibers with the average diameter of 168.2 ± 4.8 nm were fabricated. The self-sustained membranes were treated via the hot-press technique. The electroblown nanofibrous membranes (ENMs) were then characterized for their morphology and properties. Results showed that with increasing the spinning time, the membrane properties including mechanical durability, liquid entry pressure (LEP) and hydrophobicity enhanced. However, using hot-press treatment led to slight decrease in the surface contact angle. ENMs were then tested by different feeds (0, 35 and 70 g.L-1) and real seawater. A commercial PTFE membrane (0.22 μm) was used as the control for comparing the desalination results. The ENMs were used in the direct contact membrane distillation process (ΔT = 60 °C) using different feed flowrates (0.32, 0.48 and 0.64 L.min-1). Results indicated that the thinner membrane provided higher permeate flux (84.4 kg.m-2.h-1), while the thicker membrane performed more stable, even for seawater desalination (40.7 kg.m-2.h-1). In all conducted tests, the salt rejection of >99% was achieved.