Microbial synthesized iron nanoparticles after recovering rare earth elements used for removing arsenic in mine groundwater

Abstract

Recycling rare earth elements (REEs) from secondary sources such as mine wastewater has emerged as a sustainable economic strategy. In this study, microbial synthesized iron nanoparticles after the recovery of rare earth elements (FeNPs/REEs) have been used as an environmentally friendly material to remove arsenic from mine groundwater. The removal efficiencies of As(III) and As(V) were 94.5% and 96.0%, respectively, compared to that of As(III) (44.5%) and As(V) (66.5%) using only FeNPs. Indicated here is that the efficiency of FeNPs/REEs in removing arsenic was better than those of FeNPs. IC-AFS and XPS analysis showed that As(III) was partially oxidized to As(V) during the adsorption process via electron transfer. Electrochemical and BET indicated that FeNPs/REEs not only helped to expose more active sites but also the catalytic activity was enhanced. Meanwhile SEM-Mapping and FTIR demonstrated that arsenic was adsorbed onto the surface of FeNPs/REEs through complexation and ion exchange. Furthermore, Zeta potential analysis revealed electrostatic interactions between arsenic and FeNPs/REEs at pH = 6.0. Thus, the key physicochemical properties for the removal of As(III) and As(V) by FeNPs/REEs were statistically analyzed via Pearson correlation analysis, in order to understand the removal mechanism of arsenic involving surface complexation, oxidation, electrostatic and ion exchange. Finally, efficiency was consistently high in removing arsenic from mine groundwater using FeNPs/REEs with As (73.0%), Pb (76.0%), and Fe (36.0%). This study generates a new insight into FeNPs/REEs used in groundwater remediation.