Mechanism of As(V) removal by green synthesized iron nanoparticles

The application of green synthesized iron nanoparticles (nFe) for the removal of arsenic (As) from contaminated sites has often been proposed as one of the most promising remediation methods. In this work, TEM analysis showed that As(V) was uniformly adsorbed on the surfaces of nFe, while FTIR analysis confirmed that adsorption was mainly via an Fe-O-As bond, and XPS analysis indicated that only As(V) was adsorbed. Hence, the removal mechanism proposed for As(V) is based on initially nFe reacting with As(V) to form a monodentate chelating ligand and subsequently a bidentate binuclear complex. The initially high surface area (51.14 m(2) g(-1)) of nFe was decreased by half (26.03 m(2) g(-1)) after As(V) adsorption, where the materials high As(V) adsorption capacity (21.59 mg g(-1)) was attributed to unique properties derived from the green synthesis. Adsorption isotherm modeling indicated that As(V) adsorption by nFe best fit the Langmuir equation (R-L(2) = 0.9903), and thus suggested chemisorption was occurring. The adsorption also fitted the pseudo second-order kinetic rate equation well, which confirmed that adsorption was via chemisorption. Overall, the green synthesis of nFe exhibited great application potential for As(V) removal due to high As(V) adsorption capacity and simplicity of synthesis.