Fabrication of carbon nanotubes-modified poly(ethyleneimine)/sodium lignosulfonate membranes for improved selectivity performance and antifouling capability in forward osmosis process

Current thin film nanocomposite membranes incorporated with microporous particles are demanding for improving membrane performance. In this study, carbon nanotubes (CNTs)-modified poly(ethyleneimine) (PEI)/sodium lignosulfonate (SL) membranes were prepared through layer-by-layer assembly by dispersing CNTs into PEI and/or SL solutions, in order to investigate the effects of CNTs on membrane structure and forward osmosis performance. The characterization results indicated that the CNTs can be well-incorporated in the PEI/SL membranes, which contribute to a slightly lower hydrophilicity of membrane surface and different membrane morphology. The forward osmosis performance of the PEI/SL and CNTs-modified PEI/SL membranes were investigated for application in separating NaCl from water. Compare with the PEI/SL membrane, PEI/(SL-CNTs) membrane prepared by dispersing CNTs into the SL solution exhibited the best water flux and membrane selectivity. The increase in the CNTs content of the PEI/(SL-CNTs) membrane can enhance the water flux, but cannot significantly impact on the reverse salt flux, resulting in the improvement in membrane selectivity. The PEI/(SL-CNTs) membrane containing 0.075 g L-1 CNTs in SL showed a 66.3% higher water flux of 7.32 LMH, also exhibited better antifouling and foulant-release properties. This study offers a new method to design novel FO membranes for desalination and water purification.