Cr(VI) reduction by activated carbon and non-living macrophytes roots as assessed by Kβ spectroscopy

In this work, the behavior of cationic-exchange resin, activated carbon, and non-living aquatic macrophytes biomasses on the Cr(VI) and Cr(III) uptake and Cr(VI) reduction was investigated. The high-resolution X-ray fluorescence (HR-XRF) technique was used to study the adsorption process, as well as to study Cr(VI) reduction and removal from metal solutions. Batch Cr ions sorption experiments at pH 3.5 were carried out in order to speciate 3d-transition metal onto the surface of these types of adsorbents by a Kβ spectra analysis. Cr-Kβ satellite lines have been characterized for all Kβ spectra of Cr ions onto treated samples and reference material. Based on their energy position and intensity of Cr-Kβ satellite lines as well as their related to reference material shift energy, activated carbon and non-living aquatic macrophytes roots were found to act mainly as good adsorbents, first reducing Cr(VI) to Cr(III) and then followed by a Cr(III) adsorption. Although cationic-exchange resin was treated with Cr(VI) solution, no evidence of any Cr-Kβ spectral satellite lines was shown in it, suggesting that Cr(VI) was not removed in a cationic-exchange process. Evidence of reduction of hexavalent chromium by adsorbent materials was assessed by Kβ spectral lines analysis.