Characterization of Cr(VI) removal from water by Mg-Fe layered double hydroxides

Abstract

In the present study, Mg-Fe layered double hydroxides (Mg-Fe LDHs) are prepared by the co-precipitation method at pH: 10 and pH: 12 and used as adsorbents for Cr(VI) removal from aqueous solutions. The XRD analysis confirms the lamellar structure of the prepared hydroxides before calcination and shows the formation of spinel and magnesium oxide after calcination at 500°C. Cr(VI) removal by the prepared  LDHs is favorable at acidic pH. The adsorption process is spontaneous and endothermic. The uncalcined LDH prepared at pH 12 exihibites the lower removal equilibrium time. Whatever the prepared LDH used, the Cr(VI) removal  kinitics is well described by the second-order model and the adsorption isotherm is well described by the Langmuir model. The higher adsorption capacities calculated by Langmuir equation are obtained in the case of the uncalcined LDH(s) for the two preparation pH.