Removal of anionic ions from single material solution by bauxite tailings modified with FeCl₃·6H₂O

Abstract

The adsorbabilities of the unmodified and modified bauxite tailings for Cr(VI), As(V) and F(I) ions were investigated. Batch experiments were carried out to determine the removal rate as a function of adsorbent dosage, solution pH value and shaking time. The results show that the maximum removal rates of Cr(VI), As(V) and F(I) are respectively 99%, 99% and 90% by using the modified bauxite tailings. The isoelectric point of the unmodified bauxite tailings is 3.6, and that of the modified bauxite tailings is 5.0, which shifts to lower pH values in Cr(VI) solution. This indicates a specific adsorption of the anionic species on the modified bauxite tailings. A new band of Cr₂O₇²⁻ appears in the FTIR, showing that Cr(VI) is adsorbed on the modified bauxite tailings in the form of chemistry adsorption. The adsorption data of Cr(VI) on the modified bauxite tailings are well described by Freundlich model. The investigations of kinetic models show that pseudo-second-order kinetic model provides the best correlation for the experimental data.

Keywords

bauxite tailings / adsorption / anionic ions / modification