The water generated during oil extraction, characterized by high salinity (~35000 ppm) and elevated selenium (Se) concentrations (500 ppm-300 ppt), presents significant challenges for reuse. Selenium, known for its propensity to bioaccumulate, poses risks to aquatic life, wildlife, and humans if ingested at levels exceeding 50 ppb. Nanofiltration membranes demonstrate over 93% efficiency in removing Se oxyanions; however, they also eliminate other contaminants, necessitating further treatment. Se-selective adsorptive membranes facilitate adsorption during filtration. This study introduces MOF-adsorptive membranes utilizing metal-organic frameworks (MOFs) to extract Se from high-salinity, oily waste streams. MOF-808, with a satisfactory removal capacity (~75 mg/g selenite), was selected for chemical grafting onto TFC membranes to develop MOF-membranes. The research investigated the impact of salts, oils, and organic matter on MOF-membrane performance. The bare TFC membrane exhibited rejection rates of ~95%, ~20%, and ~12% for 2000 ppm Na2SO4, NaCl, and 35000 ppm NaCl, respectively. The MOF-membrane demonstrated ~92%, ~8%, and ~5% rejection at the same concentrations. Although MOF-membranes showed slightly lower salt rejections, their water permeability increased from ~3 LMH/bar to ~10.5 LMH/bar compared to the bare TFC membrane. The bare TFC membrane rejected ~86% and ~83% of 3 ppm selenite and selenate, respectively, while the MOF-membrane removed ~53% and ~74% of these ions from water. Despite the MOF-membrane's lower rejection of selenite, it achieved ~25% adsorption of 3 ppm selenite within 60 minutes at room temperature. When used in series, three MOF-membranes achieved an overall adsorption of ~85% of 0.6 ppm selenite within a total filtration time of 9 hours. Breakthrough curves were generated at various initial Se concentrations to evaluate the membrane's efficiency. The MOF-membrane demonstrated excellent regenerability, maintaining consistent adsorption efficiency of 25% after five adsorption/desorption cycles.
