Sustainable gliadin - Metal oxide composites for efficient inactivation of Escherichia coli and remediation of cobalt (II) from water

Bio-based materials facilitate greener approach to engineering novel materials with multifunctional properties for various applications including water treatment. In this study, we extracted gliadin from wheat gluten using alcoholic solvent. The aggregation limitations of gliadin protein were overcome by functionalisation with metal oxides (MOs) TiO₂, AgFe₂O₃ and AgFe–TiO₂ prepared by chemical precipitations. The novel composites were characterised by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermogravimetry analysis (TGA), Brunauer Emmet–Teller (BET), and zeta potential. The multifunctionality of MOs-gliadin composites was tested through toxic Escherichia coli (E. coli) inactivation and Co²⁺ adsorption from water. The antibacterial results showed excellent inhibition under both dark and light conditions. The maximum Co²⁺ uptake, 101 mg/g was reached with TiO₂@gliadin after 24 h and best fitted the Langmuir isotherm model. The adsorption process followed pseudo-second order model with an equilibrium adsorption capacity, q_e2 = 89.86 mg/g closer to the experimental data. Thermodynamic investigations indicated that ΔG^°=−9.677kJ/mol,ΔH°=−123kJ/mol,and ΔS°=0.490J.K/mol, respectively, suggesting that adsorption was spontaneous and endothermic. The regenerated TiO₂@gliadin composite was still efficient after five consecutive cycles. This study demonstrates that MOs-gliadin blended composites are sustainable for water purification.