Analytical and thermodynamic evaluation of reactive yellow dye removal from aqueous media using a novel montmorillonite-based hydrogel composite

In this study, a novel montmorillonite-based hydrogel composite (MMT/P(NaPAA-co-AM)) was synthesized and analytically evaluated for the removal of Reactive Yellow 145 (RY145) dye from aqueous solutions. The composite was prepared via polymerization and systematically characterized using field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) to confirm morphology, structure, and functional groups relevant to adsorption performance. The adsorption process was investigated under various experimental conditions, including contact time, pH, and temperature. The optimum conditions were found to be 45 min, pH 10, and 25 °C. The dye concentration was determined using UV–Vis spectrophotometry, enabling analytical precise monitoring of removal efficiency and adsorption capacity (LOD = 1.15, linearity = 5–50 mg L⁻¹, R² = 0.9993, RSD < 1.9 %). Adsorption isotherm modelling revealed that the experimental data were best fitted to the Langmuir and Temkin models, indicating monolayer adsorption on a homogeneous surface with interactions between adsorbate molecules. Thermodynamic parameters, including ΔG°, ΔH°, and ΔS°, were calculated, demonstrating that the adsorption process is spontaneous (negative ΔG°) and exothermic (negative ΔH°). Furthermore, key analytical performance indicators, including adsorption capacity, removal efficiency (%), and reproducibility (RSD%), were evaluated, confirming the reliability of the proposed system. The developed composite exhibited high adsorption efficiency and stability, highlighting its suitability for environmental remediation and analytical monitoring of dye pollutants in water matrices.