Poly(vinylidene fluoride)/poly(acrylic acid)/calcium carbonate composite membranes via mineralization

Organic–inorganic composite membranes were prepared via calcium carbonate (CaCO3) mineralization induced by poly(vinylidene fluoride) (PVDF)/poly(acrylic acid) (PAA) blend membranes. PAA was used as a polyanionic macromolecule in the blend membranes to generate CaCO3 particles by an alternate soaking process (ASP). The mineralization condition was optimized based on the concentrations of calcium chloride (CaCl2) and sodium carbonate (Na2CO3) solutions used for ASP, the number of ASP cycles, and the PAA content in the blend membranes. Structures and surface hydrophilicity of the composite membranes were characterized in detail by FTIR-ATR, FESEM, EDX, XRD and water contact angle. Results confirm that CaCO3 particles consisting of calcite and vaterite dispersed uniformly in/on the membranes. The membrane hydrophilicity increased dramatically due to the intrinsic wettability of these CaCO3 particles. In addition, the CaCO3 particles also caused the collapse of PAA chains in the membrane pores. Therefore, pure water fluxes of the membranes were improved about three times. Furthermore, the mineralized membranes even showed a high rejection (99.85%) of Congo red, which makes them potential in dye-polluted wastewater treatment.