Highly effective magnet-responsive LDH-Fe oxide composite adsorbents for As(V) removal

In this study the layered double hydroxide (LDH) with Mg:Al molar ratio of 2:1 synthesized using co-precipitation method was impregnated with iron oxide particles (10 and 25 wt% loading). The calcined and uncalcined composites application for As(V) removal from aqueous solutions was studied. The XRD, Mossbauer spectroscopy, SEM and vibrating sample magnetometry studies confirmed the presence of superparamagnetic maghemite (gamma-Fe2O3) particles having the size of similar to 30 nm on the LDH surface. The FTIR studies revealed co-intercalation of carbonates and sulfates in the interlayer space of LDH. The composites showed outstanding As (V) adsorption properties. For the calcined composites a slightly higher adsorption capacity was observed which was connected with incorporation of As(V) anions into interlayer space during LDH structure reconstruction. Moreover the experiments of As(V) removal at low concentrations (3.75-0.37 mg/L) showed high selectivity and efficiency in As(V) removal, when LDH was impregnated with iron oxide particles (< 10 mu g/L). The chemical stability of adsorbents, defined as percentage release of Mg, Al, Fe and As at pH range of 2-10 was investigated to estimate the possibility of their application in arsenic remediation. The measurements showed low release of elements. The kinetic experiments indicated fast adsorption with equilibrium achieved after 0.5-10 min. The Fe oxide loading did not affect the regeneration and reusability of the composites. Additionally, the experiments of spiked wastewaters treatment, revealed very high selectivity of the studied composites towards As(V).