Facile co-removal of As(V) and Sb(V) from aqueous solution using Fe-Cu binary oxides: Structural modification and self-driven force field of copper oxides

Abstract

Currently, the environmental and ecological damage caused by As(V) and Sb(V) co-contamination has attracted widespread attention worldwide. Due to the similar intrinsic structure configuration and electrostatic repulsion of As(V) and Sb(V), the long-standing issue of their low co-removal capacity remains unresolved. In this study, novel Fe-Cu (FC) binary materials with varied Fe/Cu proportions were synthesized via a simple co-precipitation method to co-eliminate aquatic As(V) and Sb(V). A 2/1 ratio of Fe/Cu was determined to be a suitable proportion with a higher co-adsorption capacity, specifically 70.9 mg·g−1 for As(V) and 94.3 mg·g−1 for Sb(V). Detailed morphological and structural analyses indicated that the FC material gradually changed from microscale aggregates to nanoscale spheres with increasing Cu content, accompanied by an increasing crystalline degree and higher surface area. Additionally, the transformation of amorphous ferrihydrite (FO) into FeO(OH) was suppressed by Fe-Cu complexion during the co-adsorption process, in which ferrihydrite (FO) had more adsorption sites than FeO(OH). In addition, the addition of Cu promoted the pHpzc of FC materials from the acidic range into the neutral or alkaline range. The increased potential difference of FC materials accelerated the As(V) and Sb(V) diffusion rate and effectively offset native electrostatic repulsion, which exhibited a considerable effect than the adsorption sites. Through detailed kinetic data analysis, it was determined that the proportion of the diffusion layer thickness around Sb(V) was suppressed to the As(V) level, and the adsorption kinetics of the two species were both promoted by the self-driven force field. All the results indicated that the co-adsorption capacity depended on the coupling contribution of Fe and Cu, where Fe oxide acted as the major adsorption potential and Cu provided a self-driven force for As(V) and Sb(V) diffusion. This study may provide a novel prospective for homogeneous metal ion co-removal.