Tourmaline as versatile additive to improve the performance of thin-film composite forward osmosis membrane

Modified tourmaline (TM) minerals were prepared using hydrothermal method, followed by surface coating with sorbitan monostearate (SPAN-60), as well as characterization of FTIR, XRD, zeta potential, and antibacterial property analysis. The as-synthesized TM particles were incorporated with polyethersulfone (PES) substrate of thin-film composite forward osmosis (TFC-FO) membrane for alleviated structural resistance and biofouling tendency based on two different approaches, polymer blending into and polymer coating onto the inorganic deposited layer, respectively. To investigate the micromorphology of the prepared membranes, SEM was used to obtain the surface and cross-section images, and elemental mapping with EDS was applied to analyze the dispersion state of TM particles in PES matrix. In comparison to the control membrane, the water flux in FO mode of the nanocomposite membranes significantly increased with TM loading content, which is attributed to the optimization of microstructure and enhancement of inner osmotic pressure resulted from the ions released by TM. More importantly, the results showed TM endowed antibacterial activity in the membrane when TM deposited layer combined with the bottom surface of substrate. It is confirmed by our work that TM is a versatile additive for FO membrane with high performance.