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The decontamination of selenium (Se) and arsenic (As) from aqueous environments has been an emerging area for membrane technology. They are difficult to be removed because of various oxidation states, range of toxicity and solubility. In this work, three water stable zirconium metal-organic framework (MOF) UiO-66 nanoparticles with different diameters, i.e., 30, 100 and 500 nm, have been synthesized and incorporated into the selective layer to form thin-film nanocomposite (TFN) membranes. These membranes were tailored to remove the Se and As concurrently. Comparing to the thin-film composite (TFC) membranes, the TFN membranes exhibit higher pure water permeability (PWP) and rejections for both pollutants due to their smaller pore size and higher hydrophilicity. In addition, the TFN membrane comprising 30 nm UiO-66 has the best performance among the three TFN membranes. The effects of particle loading have also been investigated for the 30 nm UiO-66 TFN membranes. The TFN membrane containing 0.15 wt% UiO-66 has the highest PWP of 11.5 LMH/bar and remarkable rejections of 96.5%, 97.4% and 98.6% toward SeO 3 2- , SeO 4 2- and HAsO 4 2- , respectively. Higher rejections are also achieved in the concurrent removal of Se and As. Additionally, the TFN membrane exhibits robust long term stability. To our best knowledge, this is the first work to study the particle size and loading effects of UiO-66 particles in the selective layer of TFN membranes for Se and As removal. The results achieved in this work may provide promising insights for the development of next generation NF membranes with superior performance. [ABSTRACT FROM AUTHOR]

Thin film composite membranes (TFC) consisting of an ultra-thin polyamide layer made from interfacial polymerization remain to be of paramount importance for seawater desalination. Incorporation of nanoparticles into the polyamide layer has produced thin film nanocomposite (TFN) membranes with better performance than traditional TFC membranes. However, challenges of defect formation with the introduction of nanoparticles need careful adjustments in order to surpass the trade-off relationship between permeability and selectivity. Here, we explored the influential effects of nanoparticles, solvent and surfactant treatments on the desalination performance of TFN membranes under 55 bar using 35,000 ppm NaCl as the feed at 25 °C. TFN membranes with various loadings of polyhedral oligomeric silsesquioxane (POSS) and TiO 2 -SiO 2 core-shell nanoparticles were fabricated. Surfactant treatment was performed in two different ways: membrane soaking and in-tank addition. Unexpectedly, the latter endows the membrane with an improved rejection without sacrificing its flux possibly due to the formation of a surfactant monolayer to heal defects in TFN membranes. The newly developed TFN-T membrane with the aid of synergic effects from nanoparticles, ethanol and surfactant post-treatments shows comparable performance to most commercial membranes. This work may provide useful insights to overcome the trade-off relationship between permeability and selectivity of TFN membranes for seawater desalination. [ABSTRACT FROM AUTHOR]