In situ incorporation of arsenic, molybdenum, and selenium during precipitation of hydrotalcite-like layered double hydroxides

Magnesium (Mg2 +) and iron (Fe3 +) are common cations and their precipitation as MgFeCO3-type hydrotalcite-like layered double hydroxide (HTlc) may influence contaminant mobilization in, for example, mine drainage sites. The extent of As(V), Mo(VI), and Se(VI) incorporation during HTlc precipitation in alkaline media under normal atmospheric conditions was evaluated and its effect on physico-chemical properties was examined. Even after solute entrapment, the HTlcs were characterized by strong agglomeration. The affinity for solute inclusion in the HTlcs varied in the order As(V) > Mo(VI) > Se(VI). The incorporation of solutes resulted in slight decreases in interlayer thickness, degree of crystallinity, and crystallite size compared to the solute-free MgFeCO3-type HTlc. Open air conditions allowed a substantial mass of CO32 − to occupy the HTlc interlayer together with the metal(loid)ic oxyanions. The incorporation of As(V), Mo(VI), and Se(VI) into the HTlcs resulted in the addition of Raman spectral vibrations at ~ 810, ~ 898, and ~ 835 cm− 1, respectively. With solute incorporation, additional mass loss occurred in multiple stages upon heating; however, the thermal stability of the solute-incorporated HTlcs was unchanged compared to solute-free counterpart. Additional surface absorption of H2O and structural incorporation of CO32 − were evident in the solute-incorporated HTlcs.