Preparation of a novel double-skinned forward osmosis membrane by reserve draw solute in support layer
Forward osmosis (FO) is an emerging membrane separation technology, which has attracted wide attention in recent years. However, the performance of this technology is seriously restricted by internal concentration polarization (ICP) and fouling propensity. In this work, we report a double-skinned forward osmosis membrane that is fabricated on a hydrophilic nylon microfiltration support though interfacial polymerization to enhance the performance and anti-fouling property. In order to study the effect of reverse draw permeability in the double-skinned membrane, draw solute was reserved in the support layer to simulate solute diffusing into the support layer from the draw solution. The structure and performance of the forward osmosis membrane were studied by Fourier transform infrared spectroscopy, water conduct angle, scanning electron microscopy and forward osmosis experiments. The result showed that the retention of solute concentration has an effect on the water flux of the double-skinned FO membrane. The reserved solutes changed the effective driving force between the active layers, which improved the water flux. When the concentration of the reserved solute was close to that of the draw solution, the water flux of the double-skinned FO membrane which was immersed in a 0.45 M NaCl solution was enhanced by 14.58% compared to the double-skinned FO membrane without NaCl solution immersion process. Moreover, the double-skinned FO membrane exhibited a good anti-fouling property during a long-term forward osmosis operation. This research offers a promising approach to study the relationship between reverse solute diffusion and ICP in double-skinned FO membranes. And it also provides a new idea to enhance the performance of double-skinned FO membrane.