Determination of As(V), Se(VI) and Mo(VI) bonding environments in MgAlFe(III)CO3SO4 Hydrotalcites relevant to Uranium mill neutralization processes and tailings

The removal of toxic elements (AsO4, SeO4, and MoO4) from wastewater by Hydrotalcites (HTLCs) has been noted, demonstrated, and implemented during mill neutralization processes of Uranium and other mining industries. Unfortunately, the exact knowledge of how these complex to commonly occurring MgAlFe(III)CO3SO4 HTLCs has remained uncertain. In this work, the use of K-edge Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS), Density Functional Theory (DFT), Powder X-ray Diffraction (PXRD), and Vibrational Spectroscopy (Infrared and Raman) were combined to answer this question. Based on this data, it was found that all these toxic elements formed surface outer-sphere like complexes with our MgAlFe HTLC. These results clear up the debate with respect to how these toxic elements interact with the MgAlFe HTLCs produced during such mill neutralization processes to correct current geochemical models and build a fundamental basis to create lacking surface complexation models of HTLCs.