Adsorption of Aqueous Phosphate by Thermally Aged MgFe Layered Double Hydroxides: Kinetics and Characterizations
Phosphate Adsorption by Thermally Aged MgFe LDH
Abstract
In layered double hydroxides (LDH) synthesis, calcination increasingly attracts attention because it increases adsorption capacity. Despite this, since the calcination process caused the layers of LDH to be disordered, the thermal treatment process used to improve LDH crystallinity before calcination seems unnecessary. This study elucidates the effect of thermal aging on the phosphate adsorption ability of MgFe- LDH which was previously unexplained. Uncalcined and calcined MgFe-LDH adsorbents with different Mg/Fe molar ratios (2-4) were prepared by co-precipitation. Thermally aged and calcined MgFe-LDH with an Mg/Fe ratio of 3 showed the most effective adsorption. The pseudo-second-order model provided the best description of the kinetic adsorption data. XRD analysis showed that thermal aging improves the crystallinity of MgFe-LDH before calcination, which results in high adsorption of LDH after calcination because it leads to better reconstruction possibility. This study provides additional insight into the preparation of the Mg-Fe-LDH for water phosphate removal.