Carboxymethylated PVA/PVDF ultrafiltration membrane for removing Cu(II) from water

Abstract

The ultrafiltration membrane serves to sieve macromolecules but is unable to eliminate heavy metal ions in water, and is prone to be polluted by macromolecules. To achieve the multifunctional and anti-fouling of polyvinylidene fluoride (PVDF) ultrafiltration membrane, we employed the chemical grafting method to synthesize carboxymethyl polyvinyl alcohol (CPVA). Subsequently, we blended CPVA with the PVDF membrane, employing the non-solvent co-induced phase separation (NIPS) method to fabricate the carboxymethylated PVA modified PVDF (CPVA/PVDF) ultrafiltration membrane, which demonstrated significant Cu(II) absorbance capability alongside anti-fouling properties. By observing the sieve-adsorption process, we observed a substantial enhancement in permeate flux, increasing from 1.21 L m⁻² h⁻¹ for the pure PVDF membrane to 53.37 L m⁻² h⁻¹ for the CPVA/PVDF membrane. The static adsorption of the ultrafiltration membrane satisfied the Langmuir and Freundlich isothermal models and followed pseudo-second-order kinetic model. Moreover, the blended membrane effectively removed Bovine Serum Albumin (BSA) and Cu(II) simultaneously, achieving BSA rejection efficiency of 92.00 % and Cu(II) removal rate of 90.89 %. After 10 cycles of sieving and adsorption, the BSA rejection efficiency remained consistently above 91.00 %, while the initial Cu(II) removal rate exceeded 81.00 %, indicating excellent reproducibility. In addition to the filtration of BSA, the blended membrane exhibited a low irreversible fouling of 2.59 % and a high fouling recovery rate of 97.41 %, underscoring its robust anti-fouling properties. The developed sieve-adsorption ultrafiltration membrane lays a solid foundation for the effective treatment of complex wastewater streams.