Adsorption Behaviour of Cr(VI) from Ternary Mesoporous Mg/Fe/Al Oxide Using Glucose as a Soft Template

The ternary mesoporous MgFeAl oxide (MgFeAlO) material was designed and prepared using glucose as a soft template by calcination of its MgFeAl hydrotalcite precursor. The MgFeAlO showed significantly better Cr(VI) adsorption performance than binary MgAlO. The effect of Fe³⁺ on Cr(VI) removal in simulated wastewater was studied by researching the microstructure, adsorption properties and mechanism of the material. The results showed that the addition of Fe³⁺ affected the microstructure of MgAlO, where the partial substitution of Al³⁺ by Fe³⁺ into the host layers resulted in an increase in the interlayer region and specific area (S_BET) as well as an enlargement in mesoporous feature into the MgFeAlO. The Cr(VI) adsorption process, taking place by the reconstruction of the MgFeAlO oxide with water (memory effect) companying with the intercalation of CrO^2-₄ anions, was much more efficient than that occurring in the binary MgAlO. MgFeAlO's adsorption of Cr(VI) follows the pseudo-second-order model and it is controlled by intra particle diffusion. The adsorption isotherm was better fitted by the Langmuir model, suggesting that the Cr(VI) adsorption was a monolayer adsorption onto the homogeneous support surface. All thermodynamic and kinetic calculations suggested that the Cr(VI) adsorption process on the MgFeAlO was of chemisorption nature, in which activation energy (E) and enthalpy change (ΔH) were 30.01 and 193.58 kJ·mol^-1, respectively.