Mg-Al layered double hydroxides (Mg-Al LDHs) doped with Fe2+ adsorbed As(V) (AsO43-) and Sb(V) (Sb(OH)6-) from an aqueous solution through anion exchange with Cl- intercalated in the LDH interlayer. Fe2+-doped Mg-Al LDH exhibited superior As(V) removal compared with Mg-Al LDH. The oxidation of Fe2+ doped in the Mg-Al LDH host layer to Fe3+ increased the positive layer charge of the LDH, thus increasing the anion-uptake capacity owing to stronger electrostatic attractive force between the positively charged layer and the anion. However, Fe2+-doped Mg-Al LDH was not superior to Mg-Al LDH in terms of Sb(V) removal. This was attributed to the preferential intercalation of OH- over Sb(OH)6-. The As(V) and Sb(V) removal by LDH followed Langmuir-type adsorption, which proceeded via a pseudo-first-order reaction. The equilibrium and kinetics studies confirm that the adsorption of As(V) and Sb(V) by Fe2+-doped Mg-Al LDH was the result of chemical adsorption, involving the anion exchange of AsO43- and Sb(OH)6- with the intercalated Cl-.
ASJC Scopus subject areas
- Environmental Engineering
- Waste Management and Disposal
- Management, Monitoring, Policy and Law