Investigation of internal concentration polarization reduction in forward osmosis membrane using nano-CaCO3 particles as sacrificial component

Calcium carbonate (CaCO3) nanoparticles were used as sacrificial additives to fabricate PSf substrate membranes and based on which thin film composite (TFC) membranes were prepared using m-Phenylenediamine (MPD) and 1, 3, 5-trimesoylchloride (TMC) as the monomers. Then CaCO3 nanoparticles dispersed in PSf matrix were effectively etched with hydrochloric acid to increase the substrate porosity. The effect of CaCO3 loading (ranging from 0 to 10.0 wt%) was systematically investigated. The results showed that the substrate membranes fabricated with CaCO3 incorporation exhibited higher porosity and smaller structural parameter, which is advantageous for improving water permeability and reducing mass transfer resistance. As for forward osmosis (FO) performance, the TFC membranes fabricated using modified substrates exhibited much higher water flux than the control TFC membrane prepared by substrate without CaCO3 incorporation in both AL-FS and AL-DS mode when using DI water as the feed and 2 M NaCl as draw solution. The optimized TFC21 membrane also had better performance than other commercial TFC membranes in simulated seawater desalination. Moreover, the reduced membrane structural parameter indicated that the internal concentration polarization (ICP) could be mitigated via the etching method. This study provides a low cost and feasible way to reduce the ICP in FO membranes.