Antimony removal by a magnetic TiO2/SiO2/Fe3O4 nanosphere and influence of model dissolved organic matter

Abstract

• The TSF synthesized is a novel magnetic nanosphere for effective Sb(III) removal. • Lysine, glutamate, and arginine did not alter Sb(III) removal by TSF at pH = 2–11. • Cysteine greatly reduced Sb(III) removal by TSF, and the influence is pH-dependent. • Amino acids with -SH had stronger impact on Sb(III) removal than with –NH 2 or –COOH. • Hydrogen bond network of DOMs greatly influences Sb(III) removal by TSF from water. Antimony (Sb) pollution is attracting increasing international concerns. In this work, a novel magnetic nanosphere TiO 2 /SiO 2 /Fe 3 O 4 (TSF) was synthesized for antimony removal. The influence of four amino acids on antimony removal by TSF and the associated mechanisms were systematically investigated. The results showed that TSF has high Sb removal efficiency reaching up to 96%. The presence of lysine, glutamate, and arginine did not alter antimony removal at pH = 2-11, because they were not sorbed to TSF and did not bind antimony in the aqueous phase. In contrast, cysteine-led reduction in antimony removal by TSF tended to be more pronounced when pH increased from 2 to 11, with reduction percentage increasing from 0 at pH 2 to 79% at pH 11. XPS and RAMAN analysis showed the weak interaction between antimony and –NH 2 and –COOH, but strong interaction with –SH. When solution pH increased from 2 to 11, the speciation changes of antimony, TSF, and cysteine thus their interaction changes caused antimony removal reduction. At pH = 2, cysteine formed intermolecular hydrogen bond network, limiting the coordination between -SH and antimony. When pH increased to 6 and finally to 11, the hydrogen bond network was gradually broken, and the -SH group gradually lost H + and became –S − which more readily complexed with antimony. Therefore, competition of cysteine in liquid phase with TSF for antimony was enhanced. The complexation of antimony and cysteine in solution increased with increasing cysteine concentration, hence antimony removal efficiency by TSF gradually decreased.