Analysis of F− removal from aqueous solutions using MgO

MgO was found to take up F− from NaF aqueous solutions due to the electrostatic attractive force between the positively charged MgO and F−. The F− adsorption by MgO can be represented by pseudo first-order reaction kinetics, and the magnitude of the apparent activation energy (71.6 kJ mol−1) confirms that this is a chemisorption process. The thermodynamic behavior of this process follows Langmuir-type adsorption, with the maximum adsorption amount of 5.6 mmol g-1. The F− can be desorbed from MgO using NaOH solution. The regenerated MgO can still take up F− from the solution despite the lowered adsorption capacity. Therefore, it is possible to recycle the MgO for F− adsorption.