Removal of As(V) by iron-based nanoparticles synthesized via the complexation of biomolecules in green tea extracts and an iron salt

Highlights: • Polyphenols and L-theanine participated in the formation of GT-1. • During GT-1 synthesis caffeine in plant extracts acted as a capping agent. • Mössbauer spectroscopy confirmed that an organo-Fe(III) complex was formed. • The maximum adsorption capacity of GT-1 for As(V) was 19.9 mg g⁻¹. • A mechanism of nFe formation and As(V) removal was proposed. While iron-based nanoparticles (nFe) prepared using green tea extracts have been successfully used to degrade many organic contaminants, their application to remove As(V) remains limited. Thus, in this work, nFe (GT-1) prepared using a green tea extract was used to removal As(V). The maximum adsorption capacity of GT-1 for As(V) was 19.9 mg g⁻¹ at 298 K. The formation of GT-1 and the removal mechanism of As(V) by GT-1, was examined using XRD, TEM and SEM, which showed that GT-1 was composed of amorphous particulates sized between 50 and 100 nm. GC–MS and LC-MS analysis also showed that biomolecules presented in the green tea extract, including polyphenols and L-theanine, participated in the formation of GT-1. Mössbauer spectral analysis confirmed that an organo-Fe(III) complex was formed due to the reaction between biomolecules and Fe(III). FTIR and XPS showed that the adsorption of As(V) by GT-1 occurred both via complexation with Fe(III) in GT-1 and via coordination of As(V) with free hydroxyl groups on the surface of GT-1. Batch experiments showed that adsorption was spontaneous and conformed to the pseudo-second order kinetic model. Finally, mechanisms for the formation of GT-1 and the removal of As (V) by GT-1 were proposed.