In-situ growth of MOF-based composites on nylon membrane for effective phosphate removal

A membrane adsorbent has been rationally designed to simplify the solid-liquid separation process and avoid adsorbent loss and leakage. The iron-based MOF was grown in situ on the surface of nylon membrane substrates by layer-by-layer method, and the as-synthesized MIL@nylon was post-treated with sodium borohydride to generate iron oxide nanoparticles within the MOF, named HFO@MIL@nylon. SEM, XRD, FT-IR and XPS characterization confirmed successful loading of MOF and the generation of nanoparticles in the MOF. The adsorption properties of HFO@MIL@nylon were tested. The results show that the adsorption process of phosphate accords with Langmuir and quasi-second-order kinetic model, with an adsorption capacity of 63.3 mg/g based on the mass of HFO@MIL. HFO@MIL@nylon could maintain high performance in a wide pH range. And the common interference ions SO42-, NO3-, Cl- only extended minus effect on the removal which means HFO@MIL@nylon has a good selectivity towards phosphorus. In addition, HFO@MIL@nylon membrane could work as a filter membrane, purifying 550 mL water of 200 μg-P/L with a water permeance of 1054 L/m2 h MPa.