Removal of antimony from water by potassium ferrate

The synthesized potassium ferrate (K2FeO4) was used to remove Sb(III) from water. The removal was accomplished via two steps: Sb(III) was first oxidized by ferrate, then Sb was adsorbed onto the ferrate decomposition product (DP/ferrate). XRD and FTIR characterized that ferrate decomposition product was amorphous 2-line ferrihydrite with large surface area and high porosity. Adsorption results shows that low pH favored Sb adsorption, whereas when studying the effect of ionic strength, different adsorption behaviors were found in the range of pH=3.5~5.5 and pH=5.5~7.0. Pseudo-second-order kinetic model described the sorption process very well. The values of correlation coefficient were extremely high (R2=0.999 1), indicating chemical adsorption was primary. The experimental data were found to follow the Freundlich isotherms with the best accuracy (R2=0.980 4). The value of Qmax obtained from the Langmuir-Freundlich model was 129.93 mg (g K2FeO4)-1. FTIR results revealed that in the adsorption of Sb by ferrate decomposition product, two forms of surface complexes: an inner-sphere and an outer-sphere surface complex were formed on the surface of ferrate decomposition product.