A novel nano zero-valent iron biomaterial for chromium (Cr6+ to Cr3+) reduction.

This research work aims to develop a biomaterial entrapped with iron nanoparticles by green synthesis method in which biomass act as both reducing and capping agent. Iron nanoparticles embedded in Citrus limetta peels were characterised using ICP-MS for determination of metal loading, XRD, XPS for crystallinity and oxidation states, TEM followed by FESEM-EDS for particle size and morphology. Sizes of nanoparticles were found to be in the range of 4–70 nm. Batch experiments were conducted to study the effect of different parameters such as contact time, amount of biomaterial and volume of chromium(VI) solution for 2500 mg L⁻¹ of Cr(VI). Complete reduction was attained for a contact time of 5 min with 1.5 g of biomaterial for initial concentration of 2500 mg L⁻¹. The experimental results inferred that 1 g of biomaterial completely reduced 33 mg of hexavalent Cr to trivalent Cr. XRD and XPS revealed that iron nanoparticles are in amorphous form while XPS confirms Fe⁰ state. The transition of Fe⁰ to Fe²⁺/Fe³⁺ during the treatment with chromium solution confirms the reduction of Cr⁶⁺ to Cr³⁺. [ABSTRACT FROM AUTHOR]