Development of a whey protein adsorbent via a novel green electrospinning process: Optimization of synthesis parameters and evaluation of lead removal from water

Electrospun nanofibers are increasingly used in environmental applications, particularly for water remediation, but their sustainability is limited by the reliance on toxic organic solvents. This study investigates the electrospinning of a blended solution of whey protein fibrils (WPF), a residual by-product of the dairy industry, and polycaprolactone (PCL), using bromelain hydrolysis and green solvents to obtain nanofibers for the removal of lead (Pb) from water. Defect-free nanofibers with mean diameter of 97 nm were synthesized by optimization of polymer solution parameters and electrospinning conditions, with solution viscosity as a means to predict spinnability via the entanglement concentration. FT-IR, SEM-EDX, XRD and XPS analyses revealed that WPF/PCL fibers are rich in amine, amide, and oxygenated functional groups, facilitating lead adsorption through chemical complexation and physical interactions. Kinetic studies revealed that the pseudo-second-order model was the best fit for experimental data, with an equilibrium time of 4 h. Adsorption isotherms showed that the experimental data followed the Langmuir model, with a maximum adsorption capacity of 0.35 mmol g−1, while the thermodynamic analysis established the endothermicity of the adsorption. These results highlight the potential of whey protein and green electrospinning to produce nanofibers for heavy metal removal from water without a complex and environmentally harmful production process.