Insights into the removal of Cr(VI) from aqueous solution using plant-mediated biosynthesis of iron nanoparticles

While many studies have successfully used plant extracts to biosynthesize iron nanoparticles as low-cost, sustainable and high-performance materials for removing Cr(VI) from aqueous solution, the exact removal mechanism involved remains poorly understood. In this research, a green tea extract was employed both as a reducing and coating agent to prepare iron nanoparticles (GT-nFe) via an environmentally friendly green synthesis method, where the material so produced was then used to remove Cr(VI) from aqueous solution. The efficiency in removing Cr(VI) using GT-nFe reached 90.2 % at an initial Cr(VI) concentration of 60 mg L-1 and pH of 5.0. Kinetic and thermodynamic analysis indicated that Langmuir isotherm and pseudo-second order models best described the adsorption of Cr(VI) by GT-nFe. Thermodynamic studies revealed that adsorption was spontaneous (Delta G(0)<0) and endothermic (Delta H-0>0). Application of advanced characterization techniques, including SEM-EDS, TEM and XPS, indicated a detailed Cr(VI) removal mechanism involving both adsorption and redox reactions. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Green tea extract was utilized as a reducing and coating agent in the synthesis of iron nanoparticles for the removal of Cr(VI) from aqueous solution. Kinetic and thermodynamic analysis suggested an adsorption mechanism best described by Langmuir isotherm and pseudo-second order models, with adsorption found to be spontaneous and endothermic. Advanced characterization techniques, such as SEM-EDS, TEM and XPS, revealed a detailed mechanism involving both adsorption and redox reactions.