Preparation of novel polyvinylidene fluoride (PVDF)-Tin(IV) oxide (SnO₂) ion exchange mixed matrix membranes for the removal of heavy metals from aqueous solutions

Global consideration has been growing recently to tackle the toxic and carcinogenic effects of heavy metal presence in water streams. In this work, novel polyvinylidene fluoride (PVDF)/tin(IV) oxide (SnO₂) ion exchange membranes were prepared via the phase inversion method and their performance and properties were analyzed. The results showed that the addition of SnO₂ nanoparticles (SnNPs) led to an improvement in the pure water flux from 25.5 ± 1.5 L/m².h in the pristine PVDF membrane to 250.5 ± 12.5 L/m²·h in the 1.00 wt% PVDF/SnNPs membranes. This was related to the increase in the overall porosity and hydrophilicity of the membranes. Additionally, the 0.25 wt% PVDF/SnNPs membrane reported the highest tensile strength equal to 21.3 ± 0.6 MPa compared to only 14.3 ± 0.4 MPa in the pristine PVDF membrane. Lastly, the maximum removal of Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Ni²⁺ was achieved by the 0.25 wt% PVDF/SnNPs membrane with around 93.9 ± 1.7, 92.8 ± 1.3, 82.3 ± 2.0, 70.7 ± 1.1, and 63.9 ± 1.5%, respectively, compared to 93.5 ± 1.3, 92.9 ± 1.7, 68.3 ± 2.1, 50.3 ± 1.8, and 50.3 ± 1.4% in the pristine PVDF membrane. The mechanism of removal was predicted to be a combination of ion exchange/adsorption, inner-sphere complexations and electrostatic attraction between the metal ions and the SnNPs. Such a PVDF/SnNPs membranes have great potential in the field of wastewater treatment.