Cooperative adsorption of Sb(V) in water by magnetic MgFe2O4-biochar composite beads

Abstract

As the major form of antimony in the aqueous environment, the adsorption for the removal of Sb(OH)6- is a meaningful task. In this study, MgFe2O4-doped and iron(Ⅲ) alginate cross-linked biochar ternary composite adsorbents, Fe/(MgFeO-BC) beads, were synthesized. The typical characterization analysis showed the successful synthesis of Fe/(MgFeO-BC) beads with the significant synergistic effect on the adsorption activity of MgFe2O4, the foaming effect of BC and the dispersing effect of the bead skeleton. The adsorption experiments showed significantly increased adsorption capacity of Fe/(MgFeO-BC) compared to the comparative adsorbent with Qm= 125.65 mg/g. The adsorption was able to reach equilibrium within 350 min. At low initial Sb(OH)6- concentration, the adsorption of Fe/(MgFeO-BC) can still achieve the standard antimony concentration (≤0.02 mg/L), giving potential for practical applications. The introduction of MgFe2O4 enhanced the adsorption capacity while imparting magnetic properties of composite beads, resulting in significant improvement in separation efficiency. The -OH in the structure of MgFe2O4 is the adsorption active site of Fe/(MgFeO-BC), and the adsorption of Sb(OH)6- is accomplished mainly through ligand exchange and inner-sphere complexation. These results suggest that Fe/(MgFeO-BC) is a kind of promising Sb(OH)6- adsorbent with safe, green and recyclable properties, which provides a reference for the removal of Sb(OH)6- from wastewater, even at low concentrations.