Adsorptive Removal of Rhodamine B Dye from Aqueous Solutions Using Mineral Materials as Low-Cost Adsorbents

In this work, the potential adsorption abilities of mineral materials such as zeolite (Ze), halloysite (Ha), chalcedonite (Ch), and Devonian sand (DS) used as low-cost resources for the removal of Rhodamine B (RhB) from aqueous solutions were investigated in batch conditions. Adsorption kinetics and equilibrium and the effect of solution reaction (pH) were studied. Adsorption kinetic data were analyzed using two kinetic models: pseudo-first-order and pseudo-second-order models. Adsorption kinetics was better represented by the pseudo-second-order model. Equilibrium data were analyzed by the Freundlich, Langmuir, and Sips isotherms. The results show that equilibrium data fit well with the Freundlich equilibrium. Monolayer maximum adsorption capacities of RhB were assumed at 6.964, 4.252, 2.701, and 0.349 mg/g for Ze, Ha, Ch, and DS, respectively. Adsorption was strongly pH-dependent. The maximum RhB adsorption on all tested materials was observed at pH = 2.2 and decreased with further pH increase. The results of these investigations suggest that natural materials represented by certain minerals have a good potential for the removal of Rhodamine B from aqueous solutions. Graphical Abstract