Study of the effect of the LDH cations precursors in the removal of arsenic in aqueous solution

Abstract

Layered double hydroxides (LDH) are anionic clays, mainly used as adsorbents, ion exchange material, and catalysts. Generally, they present high specific surface areas, alkaline character, high metallic dispersion, and high thermal stability. If they contain a transitional element in their structure, the solid may present redox properties. LDH were synthesized with the following combinations: MgAl, MgFe, and ZnMgFe, aiming to determine the effect of cationic nature in the structure and the functionality of the synthesized clay as adsorbents in polluted aqueous effluents. The textural properties were determined by nitrogen adsorption isotherms. Crystalline structure was studied by XRD and the presence of the anions of the interlayer was determined by FTIR spectroscopy. The studies of removal of As(III) and As(V) from aqueous solutions, using the LDH, show that after 24 h the solids reach a high removal efficiency. ZnMgFe solid removed both species of arsenic with values of 95 and 98% for As(II) and As(V), respectively. The MgFe solid showed some selectivity to the uptake of As(V), while the MgAl only removed As(V). This selective behaviour can be beneficial in studies of arsenic speciation. HIGHLIGHTS Al and Fe present different electrostatic interactions which modify the LDH activity.; The different chemical behaviour of the constituent metals has influenced the morphology.; The solids present more than 88% of removal of As(V) in less than 24 h.; MgAl mostly removed As(V).; ZnMgFe had an excellent performance for both arsenic species.;

Keywords

• as(iii)
• as(v)
• ldh
• mgal
• mgfe