Water-soluble ozonated lignin as a hydrophilic modifier for poly(vinyl alcohol) membranes for pervaporation desalination

Abstract

Poly (vinyl alcohol) (PVA)-based membranes are widely applied to pervaporation desalination. Further modification of the PVA-based membranes with suitable additives is attractive for increasing the water permeation fluxes. In this work, water-soluble ozonated lignin (Ws-OL) was prepared and used as an additive for preparation of Ws-OL-modified PVA membranes, which showed relatively high surface hydrophilicity, reduced crystallinity, and small crystallite sizes compared to the neat PVA membrane. The Ws-OL modification brought a 2.1 times of water permeation flux to the PVA membrane in pervaporation desalination on a 3.5 wt% NaCl(aq) solution at 25 °C. Under an optimum condition, the modified PVA membrane possessing 50 wt% Ws-OL and being crosslinked with 4-sulfophthalic acid (SPTA) exhibited a water permeation flux and a salt rejection of 78,630 g m-2 h-1 and 99.91%, respectively. The high efficiency of Ws-OL in modifying hydrophilic membranes is noteworthy and could be potentially applied to other membranes for pervaporation separation and oil-water separations.