Influence of Divalent Cations on the Performance of Fe(III)‐Based Layered Double Hydroxides for Anionic Dyes Removal: A Comparative Study

ABSTRACT Layered double hydroxides (LDHs) are promising for cleaning wastewater. Their effectiveness depends on the cations in their layers. Although LDHs have been studied a lot, there is not much research on how well Fe(III)‐based LDHs work with different divalent cations, especially for removing anionic dyes. This study explored new methods to create and compare Mg–Fe and Ca–Fe LDHs using the coprecipitation technique. The aim is to remove methyl orange (MO) from water. We focused on low‐cost, Fe‐rich LDH combinations that leverage the strong charge of Fe 3 + to enhance anion adsorption. Tests using TGA, FTIR, and SEM showed that the LDH structures are formed successfully. In experiments, the Mg–Fe LDH performed much better than the Ca–Fe LDH. It could absorb up to 211.86 mg/g and removed 92.44% MO, while the Ca–Fe LDH absorbed 76.98 mg/g and removed only 20.60%. The adsorption process followed the Freundlich isotherm, and the adsorption rate is best described by a pseudo‐second‐order model, indicating chemisorption. The intraparticle diffusion model describes a multistep adsorption process. The main new idea in this work is the direct comparison of Mg–Fe and Ca–Fe LDHs. It shows how the type of divalent cation affects the stability and adsorption ability of Fe(III)‐based LDHs.