In situ formation of La(OH)3-poly(vinylidene fluoride) composite filtration membrane with superior phosphate removal properties

Abstract

It is of great practical interest to combine membrane filtration with the removal of phosphate, which is the key nutrient in waters causing the eutrophication. In this study, we report the first example of in situ formation of La(OH)3 nanorods in poly(vinylidene fluoride) (PVDF) membrane by adding LaCl3·7H2O precursor in the membrane casting solution, after a non-solvent induced phase separation process in alkaline solution. The structures, morphologies, and surface properties of the La(OH)3-PVDF composite membranes were characterized by SEM, TEM, XRD, FT-IR, XPS, and water contact angle measurements. The adsorption and filtration experiments demonstrated that the La(OH)3-PVDF composite membrane exhibited a molecular weight cut-off of 16 kDa and superior adsorption and filtration properties, i.e. high adsorption capacity (256.6 mg P/g (La)), fast adsorption kinetics, excellent regenerability, negligible lanthanum leakage, efficient phosphate removal under high filtration permeability and simultaneous removal of organic pollutants and phosphate. We hope that our work has presented a new direction for the design of filtration membrane with superior adsorption properties.