In this research, a local and pristine clay was evaluated for the adsorption of different dyes from an aqueous medium. In this sense, a systematic characterization of the adsorbent was carried out using different techniques. X-ray diffraction (XRD) analysis indicate the presence of phyllosilicates, primarily consisting of chlorite and muscovite. Silicon dioxide (49,12%) and aluminum oxide (22,84%) are the predominant oxides primarily associated with the phyllosilicates. The studied clay showed significant adsorption capacities for both Safranine (SF) and Methyl Green (MG) dyes, with maximum adsorption capacities \({q}_{max}\) of 101.09 mg/g and 86.87 mg/g, respectively. This was primarily attributed to a suitable morphology, as demonstrated by the Scanning Electron Microscopy (SEM), holding the dye molecules as verified directly by Energy-dispersive X-ray (EDX) and indirectly by Fourier Transform InfraRed (FTIR) analyses. Kinetic studies indicated that the adsorption are well described by the pseudo-second-order kinetic model, while the Langmuir model best described the experimental data. The thermodynamic variables exhibited an increase in the ΔG values as the temperature increase revealing the exothermic and thermodynamically favorable nature of the dyes adsorption mechanism. The theoretical investigation using the density functional theory (DFT) calculations on the structures of SF and MG dyes has demonstrated that SF cations exhibit higher electrophilicity and reactivity, with an increased aptitude for electron acquisition, enabling stronger adsorption onto the clay surface compared to the MG cations. These results highlight the capability of our clay as an effective and inexpensive adsorbent and pave the way for the decolorization of wastewater.
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