Iron NPs Synthesised using Quercetin: characterization and application in Cr(VI) bioreduction

Chromium (VI) is a toxic metal ion, usually emanating from industrial activities such as tanning, electroplating, and textile, inimical to humans, animals, and the ecosystem at large. The pertinacious nature of this contaminant continues to be a problem despite several remediation strategies. In this study, iron NPs synthesised using quercetin were produced using with quercetin as a reducing and capping agent. The nanoparticles were characterized through UV-visible spectroscopy, Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and dynamic light scattering (DLS). In batch mode, the effect of process parameters viz contact time, bioreductant dosage, pH, temperature and initial Cr (VI) concentration were investigated. The kinetic order and thermodynamic of Cr (VI) reduction was also examined. Findings from this study shows that the nanoparticles were irregular in shape and agglomerated with an average hydrodynamic size of 41 nm. Strong iron signal was observed in the corresponding EDX spectra. The iron NPs did not require additional stabilization and have a great potential for further complexation. The optimal Cr (VI) reduction (96%) was attained at contact time of 40mins, pH 2, room temperature, 1mg/L bioreductant dosage, and 10mg/L initial Cr (VI) concentration. The reduction rate fits pseudo first order with correlation coefficient (0.9315), rate constant (0.0361 L.mg ^-1 .min ^-1 ) and pseudo second order with correlation coefficient (0.9166), rate constant (0.0361 L.mg ^-1 .min ^-1 ) kinetic model. Thermodynamic studies reveal that the reaction was spontaneous and exothermic (ΔG ^o <0 (-57.886 at 298K), ΔH ^o < 0 (-32.735), ΔS ^o >0 (0.0844)). Fe NPs (Q) efficiency dependent on contact time, nanoparticle dosage, pH and the reaction followed pseudo-first and pseudo-second order kinetic models and the thermodynamic studies indicate the reaction to be feasible.