WS2 deposition on cross-linked polyacrylonitrile with synergistic transformation to yield organic solvent nanofiltration membranes

Abstract

Using liquid phase exfoliation (LPE) methods established in literature, several different tungsten (IV) disulfide (WS2) dispersions were prepared in solvents ranging from NMP, ethanol/water to pure water via sonication under ambient conditions. These various dispersions were then deposited directly onto cross-linked ultrafiltration-level polyacrylonitrile (PAN) flat sheet membranes through a pressure-assisted filtration process to produce ready-to-use membranes without any additional modifications. To evaluate and compare the performances of the various membranes produced, organic solvent nanofiltration (OSN) was utilized as the testing method while also representing a potential application of these fabricated membranes. After observing and comparing the outcomes of depositing different WS2 dispersions, deposition of the NMP dispersion was found to yield a promising membrane due to a concurrent synergistic densification effect with positive impacts on membrane performance. Thus, further emphases were placed on studying the use of different initial WS2 concentrations and longer sonication times in NMP dispersions. After the optimization, the composite membrane consisting of WS2 on cross-linked PAN substrates shows impressive performance with a high pure ethanol permeance of 43.35 L m−2 h−1 bar−1, a rejection of 86% towards Remazol Brilliant Blue R (Mw = 626.54 g/mol) and a long-term sustained rejection of 99% towards Evans Blue (Mw = 960.81 g/mol) in ethanol.