Evaluation of thin film nanocomposite reverse osmosis membranes for long-term brackish water desalination performance

Nanoparticle addition in the currently widely used thin film composite (TFC) membranes is a promising technology to advance separation performance and bring novel functionality in membrane desalination processes. These thin film nanocomposite (TFN) membranes boast many advantages over their TFC counterparts such as increased water flux without compromising salt rejection and bacterial resistance. However, the stability of TFN membranes is unknown in industrial, long-term applications. Via interfacial polymerization, we synthesized a series of polyamide TFC and TFN membranes with different nanoparticle content, 0 wt%, 0.15 wt%, 0.30 wt%, in the casting solutions. At the United States Bureau of Reclamation's Water Quality Improvement Center in Yuma, AZ, the membranes were tested for ~ 3000 h in a lab-scale testing system. We characterized the physico-chemical nature and morphology of the membranes before and after the testing. All membranes exhibited relatively stable long-term separation performances. At the highest zeolite loading tested, in comparison with the TFC membrane, water permeance increased from 3.7 ± 0.6 μm MPa^{− 1} s^{− 1} to 5.3 ± 0.5 μm MPa^{− 1} s^{− 1} and solute rejection slightly increased from 97.4 ± 0.3% to 97.9 ± 0.1%. In this study, TFN membranes exhibited long-term desalination stability and improved separation performance compared to TFC membranes.