Reactivity and mechanism of bromate reduction from aqueous solution using Zn–Fe(II)–Al layered double hydroxides

Abstract

In this study, for the first time, Zn–Fe(II)–Al layered double hydroxides (LDHs) with chloride intercalation were prepared and used in the removal of bromate from aqueous solutions. Batch experiments were performed, and the reactivity and mechanism were discussed with respect to the influence of various experimental such parameters as the effects of contact time, initial bromate concentration, the dose of Zn–Fe(II)–Al LDHs, pH and competing anions on bromate removal by Zn–Fe(II)–Al LDHs. The results show that bromate can be effectively removed by Zn–Fe(II)–Al LDHs. Starting from an initial concentration of 0.78μmol/L, nearly 100% of bromate was removed in 0.5h under neutral pH and with a dose of Zn–Fe(II)–Al LDHs of 0.5g/L. Equilibrium was achieved within 1.5h because bromide was adsorbed by the Zn–Fe(II)–Al LDHs samples during the reaction time. Mass balances provided strong evidence that bromide is the primary product via the reduction process. Moreover, results from materials characterization experiments indicated that the layered structures remained in the Zn–Fe(II)–Al LDHs samples collected after the reaction, indicating that Zn2+, Fe3+, Al3+ and interlayer chloride anions were not released.