Highly efficient arsenic adsorption onto Mg/Al/Fe layered double hydroxides: Kinetics, isotherm, XPS and Mössbauer spectroscopies

LUENGO, CARINA; LOPEZ, NICOLAS; RAMOS CINTHIA; AVENA, MARCELO

Journal of Water Process Engineering

Elsevier Ltd

Año: 2023 vol. 56

The adsorption of arsenate onto a Mg/Al/Fe layered double hydroxide (Fe-LDH) was studied at different anionconcentration, pH, temperature and stirring rate. Different characterization techniques such as FT-IR, X-raydiffraction, XPS and M¨ossbauer spectroscopies, and zeta potential measurements were used for determining themechanism of arsenate adsorption onto the studied solid. Two mechanisms are postulated: a) anion exchangereactions with chloride and hydroxyl ions of the interlayer space, and b) ligand exchange reactions with formationof inner-sphere complexes on the Fe-LDH surfaces, with participation of Fe(III) ions from the structure.Arsenate adsorption on Fe-LDH was dependent on the initial pH and the concentration, but was independent ofthe stirring rate and temperature. Fe-LDH exhibited excellent As(V) removal capacity, much higher than otheradsorbents reported in the literature. A dose of 10 g L􀀀 1 Fe-LDH was sufficient to reach a percentage removalhigher than 95 % for a concentration of arsenic of 1 × 10􀀀 4 M found in certain places in Argentina, obtainingresidual arsenate values below the recommended World Health Organization limit (0.01 mg L􀀀 1). Although thematerial dissolves at low pH, its high arsenate removal efficiency, the low cost and the green and sustainablecharacteristics of the material make it an effective adsorbent for the treatment of arsenic contaminated waters.