A novel adsorbent (Fe3O4/HCO) was prepared via co-precipitation from a mix of ferriferrous oxide and a Ce-rich waste industrial sludge recovered from an optical polishing activity. The effect of system parameters including reaction time, pH, dose, temperature as well as initial concentration on the adsorption of Sb(III) were investigated by sequential batch tests. The Sb(III)/Fe3O4/HCO system quickly reached adsorption equilibrium within 2 h, was effective over a wide pH (3–7) and demonstrated excellent removal at a 60 mg/L Sb(III) concentration. Three isothermal adsorption models were assessed to describe the equilibrium data for Sb(III) with Fe3O4/HCO. Compared to the Freundlich and dubinin-radushkevich, the Langmuir isotherm model showed the best fit, with a maximum adsorption capacity of 22.853 mg/g, which exceeds many comparable absorbents. Four kinetic models, Pseudo-first-order, Pseudo-second-order, Elovich and Intra-particle, were used to fit the adsorption process. The analysis showed that the mechanism was pseudo-second-order and chemical adsorption played a dominant role in the adsorption of Sb(III) by Fe3O4/HCO (correlation coefficient R2 = 0.993). Thermodynamic calculations suggest that adsorption of Sb(III) ions was endothermic, spontaneous and a thermodynamically feasible process. The mechanism of the adsorption of Sb(III) on Fe3O4/HCO could be described by the synergistic adsorption of Sb (III) on Fe3O4, FeCe2O4 and hydrous ceric oxide. The Fe3O4/HCO sorbent appears to be an efficient and environment-friendly material for the removal of Sb(III) from wastewater.

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Antimony (Sb) and its compounds are considered as global priority pollutants. Elevated concentrations of antimony in natural and industrial process wastewater are of global concern, particularly given interest in the potential toxicity and harm to the environment from aquatic exposure. Iron-based materials for treatment by adsorption are widely regarded to have potential merit for the removal of trace contaminants from water and especially in the search for efficient and low-cost techniques. In this paper, we review the application of iron-based materials in the sorption treatment of antimony contaminated water. The interaction of Sb is discussed in relation to adsorption performance, influencing factors, mechanism, modelling of adsorption (isotherm, kinetic and thermodynamic models), advantages, drawbacks and the recent achievements in the field. Although iron-based adsorbents show promise, the following three aspects are in need of further study. Firstly, a select number of iron based binary metal oxide adsorbents should be further explored as they show superior performance compared to other systems. Secondly, the possibility of redox reactions and conversion between Sb(III) and Sb(V) during the adsorption process is unclear and requires further investigation. Thirdly, in order to achieve optimized control of preferential adsorption sites and functional groups, the mechanism of antimony removal has to be qualitatively and quantitatively resolved by combining the advantages of advanced characterization techniques such as Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy (XPS), Atomic force microscope(AFM), X-ray absorption near edge structure(XANES), and other spectroscopic methods. We provide details on the achievements and limitations of each of these stages and point to the need for further research.