Mg/Al and Mg/Fe layered double hydroxides derived from magnesite and chemicals: The effect of adsorbent features and anions chemistry on their removal efficiency

Owing to their anion exchange properties, layered double hydroxides (LDH) are promising candidates as ad-sorbents for the anions removal from industrial wastewaters. Therefore multiple attempts were made in order to substantially lower their production costs. In this work, LDH obtained via transformation of magnesite were compared to conventionally obtained LDH in terms of their affinity towards As(V), Cr(VI), P(V), Mo(VI), Se(VI) and V(V). The materials with different chemical compositions (Mg/Al and Mg/Fe) were tested in aqueous systems with different parameters such as initial concentration and pH. The minimum doses of adsorbents required for the efficient treatment were determined in the range of 0.1-4.0 g/L. The influence of the competitive anions (sulphates and nitrates) on removal efficiency and kinetics of the reaction was investigated and indicated the negative influence of sulphates. The results revealed, that the LDH obtained with the use of magnesite shows high efficiency and selectivity for the removal of low concentrations of anions (C-in = 0.05 mmol/L). Moreover, the tested LDH are effectively removing anions at low pH conditions.