Temperature-Dependent Speciation Study Using X-Ray Absorption Fine Structure Spectroscopy to Develop a Green Immobilization Route for Chromium

Abstract

To develop a green, rapid and energy-efficient route for the toxic waste immobilization, chromium was captured from aqueous system and subsequently solidified using calcium hydroxyapatite (HA) powder. The effect of sintering temperatures on the inter-conversion of Cr(III/VI) species in the HA matrix was investigated by synchrotron X-ray absorption fine structure spectroscopy. The results of X-ray absorption near edge structure showed the gradual transformation of Cr(III) to Cr(VI) oxides from ~ 0 % to ~100 % at sintering temperatures of 100 °C to 1150 °C. The extended X-ray absorption fine structure results revealed a typical Cr(III) oxide as the dominant structure at a temperature lower than 500 °C and Cr(VI) oxide structure at higher temperatures. Oxidation behavior of Cr(III) is strongly dependent on sintering temperatures. Rapid of Cr(III) may be avoided by adopting low-temperature sintering techniques and adding selective binders to Cr-HA Composite.