UiO-66 incorporated thin-film nanocomposite membranes for efficient selenium and arsenic removal

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 SeO32-, SeO42- and HAsO42-, 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.