(152al) Selective Removal of Selenium from High-Salinity Water Using MOFs and MOF-Incorporated NF Membrane

Selenium shows the tendency of bioaccumulation in the food chain and shortens the life span of aquatic and wild animals. Concentration of selenium greater than 0.05 ppm is hazardous for human health, and hence, it is crucial to remove it from drinking water. In addition, selenium is one of the components of the produced water (the waste stream in the oil extraction process), which limits the reuse of the treated stream. Metal organic frameworks (MOFs) are gaining significant attention recently as adsorbents due to their high porosity, adsorptivity, and selectivity. In this study, the nickel-based ionic MOF (Ni-iMOF), zirconium-based MOF (MOF-808), iron MOF(Fe-MOF), copper MOF (Cu-MOF) and graphene oxide immobilized MOFs (GO-Fe-MOF and GO-Cu-MOF) were synthesized via solvothermal method using different metal salts and ligands and examined for the removal of selenium from water and saline water. Ni-iMOF, MOF-808 and Fe-MOF could remove selenite SeO₃^2- (upto 75 mg/g) and selenate SeO₄^2- (upto 43 mg/g) from water based on ion exchange and coordination adsorption mechanisms in the presence of competing ions, including SO₃^2- and SO₄^2-. Based on the acceptable removal performance of MOF-808 and Fe MOF, they were selected for immobilizing on the TFC membrane for the generation of MOF-adsorptive membranes. The mentioned MOFs were immobilized on the polyamide layer through chemical grafting. The Fe-MOF membrane showed 6.63 LMH/bar permeability with enhanced selenium removal (about 88%). The effect of MOFs on the physicochemical properties of MOF-NF membrane and the selective performance along with the salt rejection of the fabricated MOF-NF membrane at different operation conditions (temperature (25-45°C), pH (2-12) and varying ionic strength (SO₃^2- and SO₄^2-)) are studied.