Aqueous arsenic (As) and antimony (Sb) removal by potassium ferrate

• Fe(VI) removed As and Sb individually and simultaneously from solution effectively.
• IR and XRD defined the amorphous characterization of DP/Ferrate.
• Synergistic effect on simultaneous sorption of As and Sb by DP/Ferrate were found.
• IR and XPS demonstrated the presence of arsenato antimonates.
• Configuration of the adsorbed As and Sb speciation onto DP/Ferrate was postulated.

Priority pollutants arsenic (As) and antimony (Sb) were removed from aqueous solution by potassium ferrate. As(III) and Sb(III) were oxidized, then separated from solution by the adsorption of Fe(VI) decay product (DP/Ferrate). XRD and FTIR results revealed the “amorphous” characteristics of DP/Ferrate. Adsorption studies in single-solute and bi-solute systems were conducted. The maximum adsorption capacity (Qmax) of single As was 162.02 mg (g K2FeO4)−1 at pH0 6.5 and of single Sb was 129.93 mg (g K2FeO4)−1 at pH0 4.0. Regarding bi-solute adsorption, a synergistic effect between As and Sb was demonstrated. Compared to single-solute adsorption, the adsorption rates of both elements were enhanced significantly. The adsorption isotherm of Sb in the presence of As was reproduced well by the Brunauer–Emmett–Teller (BET) model, indicating heterogeneous multilayer adsorption. The FTIR spectra featured the appearances of new peaks compared to the blank spectrum of DP/Ferrate, indicating that the surface speciation contained Fe–O–As and Fe–O–Sb bonds in the corresponding single-solute system; As–O–Sb binding was found in the bi-solute system. Furthermore, high-resolution XPS analysis pointed to the formation of arsenato antimonates of a polymer-like configuration, which was believed to account for the synergistic effect on simultaneous adsorption of As and Sb by DP/Ferrate. This paper demonstrated that using potassium ferrate is a viable water treatment technology to remediate arsenic and antimony combined pollution.

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