Selective antimonite removal from water by montmorillonite-immobilized nanoscale zero-valent iron.

This study investigated the antimony (Sb) adsorption behavior on newly prepared montmorillonite (Mt)-immobilized nanoscale zero-valent iron (nZVI) (hereafter Mt-nZVI) in aqueous solution. Mt-nZVI showed the highest Sb adsorption capacity (71-76 mg·Sb·g^-1 adsorbent) at pH 4-8. The pseudo-first-order and pseudo-second-order kinetic models fitted well (R^{2 3} 0.992) with the experimental data on Sb adsorption onto Mt-nZVI. The Langmuir isotherm model (R² = 0.99) was more suitable than the Freundlich isotherm model (R² = 0.95) for describing the adsorption of Sb on Mt-nZVI. Mt-nZVI had an almost 7 times higher theoretical Sb adsorption capacity than nZVI when calculated in terms of Fe. Neither 0.01 M phosphate nor 0.01 M sulfate had a significant effect the Sb adsorption capacity of Mt-nZVI, and more than 80% of the Sb adsorption capacity remained in the presence of 0.001-0.1 M NaCl or 1-30 mg·L^-1 humic acid. However, the presence of 0.01 M silicate or carbonate or 0.0001 M arsenate significantly affected the Sb adsorption capacity of Mt-nZVI. [ABSTRACT FROM AUTHOR]