Facile fabrication of PVB-PVA blend polymer nanocomposite for simultaneous removal of heavy metal ions from aqueous solutions : kinetic, equilibrium, reusability and adsorption mechanism

The available poly (vinyl butyral) (PVB)-based materials are potential media for wastewater treatment, however, their high butyral contents and low quantity of hydroxyl groups cause their low adsorption efficiency for heavy metals removal. Here, a new polymer blend nanocomposite of PVB-poly (vinyl alcohol), (PVB-PVA), incorporated with different contents of stearic acid-grafted epsilon-manganese oxide nanoflowers, (PVB-PVA/SA-ε-MnO₂), was prepared through blending, solution casting and solvent evaporation techniques. According to the results, PVB-PVA/SA-ε-MnO₂ nanocomposite containing 6 wt% SA-ε-MnO₂ showed the maximum efficiency of 99.88%, 94.26% and 87.12%, respectively, for the adsorptive removal of Cu²⁺, Cd²⁺ and Pb²⁺ metallic ions from aqueous solutions. The binary and ternary adsorption of the heavy metal ions in aqueous solutions indicated a high adsorption affinity towards Cu²⁺. Kinetic modeling revealed that the adsorption of Cu²⁺, Cd²⁺ and Pb²⁺ ions follow the diffusion–chemisorption model (R² = 0.99, RMSE = 0.31–0.56). The adsorption isotherms modeling confirmed that the Langmuir isotherm well-fitted the adsorption data of the target ions on the nanocomposite surface (R² = 0.96–0.99, RMSE = 3.20–9.68), suggesting a homogeneous monolayer surface adsorption with the maximum adsorption capacity of 172.54, 112.89 and 111.23 mg/g for Cu²⁺, Cd²⁺ and Pb²⁺ ions, respectively. The reusability of PVB-PVA/SA-ε-MnO₂ nanocomposite presented the removal efficiency of 94.50%, 92.05% and 88.60%, respectively, for Cu²⁺, Cd²⁺ and Pb²⁺ ions after five successive sorption/desorption cycles. The great adsorption performance of PVB-PVA/SA-ε-MnO₂ towards the heavy metal ions could be attributed to the important role of various types of physicochemical interactions (e.g., electrostatic interactions and surface complexation) in the adsorptive removal process.