Investigation of the Adsorption Mechanism of Halogenated Anions in Industrial Wastewaters by Mg/AL Hydroxide Double Layer

In the wastewater of many industrial plants and mining industries, there are halogen compounds such as chlorine, fluorine, bromine and iodine, which can redce the quality of recycled water. One way to remove halogenated anions from wastewaters is to use layered double hydroxides, which have several advantages such as simplicity and low price. In this study, the adsorption properties of layered double magnesium / aluminum hydroxide is investigated by laboratory studies and molecular modeling for fluoride to iodine halogens. Laboratory studies have been performed to compare the ability to absorb different types of halogens by synthetic magnesium aluminum LDH (original and calcinated at 400 ˚C) and molecular modeling studies to understand effective mechanisms for different halogenated anions. The results of laboratory studies showed that both original and calcinated layered magnesium / aluminum hydrochloride have the highest absorption potential for fluoride ions and the lowest absorption for iodide ions. Calcination significantly increases absorption for all types of halogens. The predominant mechanism for the uptake of halogenated anions by non calcinated layered double hydroxides is ion-exchange and in calcinated products, surface and physical absorption. The electronegativity seems to be the determining parameter. The results of the energy calculation of the interaction obtained from the molecular modeling show that the preferred position for all halogens is the hollow hexagonal structure of the double-layer hydroxide. Also, the absorption rate in the hollow hexagonal position is the highest for the fluorine and the lowest for iodine. In addition to confirming the results of laboratory studies, these modelling results confirm the possibility of using molecular modeling methods as a powerful tool in examining the behavior and understanding the process mechanisms.