Bimetallic Fe/Ni nanoparticles derived from green synthesis for the removal of arsenic (V) in mine wastewater

Since the incidences of arsenicosis have significantly increased worldwide in the last decade, remediation of arsenic (As) pollution is now imperative. In this study, calcined green synthesized Fe/Ni nanoparticles (C-Fe/Ni NPs) were evaluated for their efficacy for As (V) removal from aqueous solution. Under optimal experimental conditions As (V) removal efficiency reached 87.3%. Analysis of changes in the surface properties of C-Fe/Ni NPs before and after interaction with As (V) using a range of advanced characterization techniques including IC-AFS, SEM-EDS, XPS and XRD revealed that the As removal mechanism involved only adsorption. Adsorption kinetics followed a pseudo-second order rate model (R2 > 0.986) and adsorption best fit the Langmuir isotherm model (R2 > 0.958). Thermodynamic studies indicated that adsorption was a spontaneous endothermic process. On the basis of these results, a removal mechanism of As (V) by C-Fe/Ni NPs was proposed. Finally, the efficacy of the material for practical remediation of As from aqueous solution was assessed, including the influence of coexisting anions. While Cl-, NO3- and SO42- had little influence on As (V) removal, both H2PO4- and HCO3- significantly negatively affected removal.