In situ polymerization of PDA with the simultaneous incorporation of La-EDTA MOFs to endow polysulfone membranes with UF-level water permeance and NF-level lead removal efficiency

Water scarcity is a global issue; both natural and anthropogenic practices contribute to the release of pollutants into the environment. Specifically, exposure of water reservoirs to heavy metals has become a critical challenge due to their toxicity and bio-accumulation. Thus, the advancement of water treatment technologies has become crucial to avoid its negative effects while guaranteeing the supply of clean water. Adsorptive membrane filtration has emerged as a viable option because of its simplicity, cost-effectiveness, and high efficiency. In this study, a novel lanthanum (La)-EDTA MOF was synthesized and incorporated into the polysulfone (PSF) membrane surface with the assistance of polydopamine (PDA) adhesive to form a PDA@La-EDTA MOF nanocomposite membrane. According to the adsorption kinetics and isotherm studies, the PDA@La-EDTA MOF was found to follow monolayer chemisorption with a high maximum adsorption capacity (356 mg g⁻¹). Inspired by this, three types of PDA@La-EDTA MOF nanocomposite membranes were prepared via in situ polymerization of PDA with the simultaneous incorporation of La-EDTA MOFs by varying their amounts (i.e., x = 0.05, 0.1, and 0.2 w/v%). The best-performing PPM_0.1 membrane, in which PDA@La-EDTA MOF of 0.1 w/v% was incorporated, achieved Pb²⁺ removal rate of 94.7% (∼1.8 times of the pristine PSF membrane) and pure water flux and permeate flux of 100 and 93.3 LMH at 1 bar, proving the potential of PDA@MOF hybrid membranes as a highly effective alternative for alleviating lead contamination during wastewater treatment. The UF-level water permeance was attained due to the large pore size of PSF membranes, while the NF-level Pb²⁺ removal rate was attributed to the adsorption sites stemming from the functional groups of both PDA and La-EDTA MOFs.