Stability and stabilizing efficiency of Mg-Fe layered double hydroxides and mixed oxides in aqueous solutions and soils with elevated As(V), Pb(II) and Zn(II) contents

Although the mechanisms of metal(loid) removal from aqueous solutions using LDHs (layered double hydroxides) and mixed oxides (thermally treated LDHs; CLDHs) have been studied, research dealing with their stability, stabilizing efficiency and remediation potential for contaminated soils remains scarce. We present a complex study investigating the stabilizing efficiency of Mg-Fe LDHs and CLDHs at different conditions, including aqueous solutions and real soils with highly elevated As(V), Pb(II) and Zn(II) concentrations. All studied materials showed excellent (ad)sorption efficiency for As(V), Pb(II) and Zn(II) in aqueous solutions. Additionally, the reconstruction ability of CLDHs at different conditions that could improve their adsorption properties was also evaluated, and the dependence on time, pH and the concentrations of metal(loid)s was shown. In general, CLDHs showed higher stability and stabilizing efficiency in aqueous and soil solutions; however, LDHs were more efficient in contaminated soils. Furthermore, solid state analyses coupled with geochemical modeling showed the formation of new phases corresponding to Mg‑carbonates/silicates on the surfaces of LDH/CLDH after their incubation in soils. Both LDHs and CLDHs significantly decreased the bioavailable/labile fraction of As(V) and Zn(II) in the studied soils. In general, our work shows Mg-Fe LDHs and CLDHs as prospective materials for water and soil remediation.