Optimized adsorption of xylenol orange dye in water systems employing CTAB-treated montmorillonite composite

In this study, a cetyltrimethylammonium bromide–modified montmorillonite composite (CTAB‑MMT) was prepared by treating natural montmorillonite with a cationic surfactant. The morphological and crystal structural properties of CTAB‑MMT were thoroughly characterized using SEM, XRD, FT‑IR, TGA and BET analyses. The synthesized CTAB‑MMT was subsequently applied to remove xylenol orange (XO) from aqueous solutions. To evaluate their effects on removal efficiency, key parameters—including CTAB loading ratio, solution pH, temperature, contact time, adsorbent dosage, and initial XO concentration—were systematically investigated. And MMT-5 exhibited an adsorption capacity of 95.94 mg/g at pH 4.0 and an adsorbent dosage of 0.10 g for an initial XO concentration of 200 mg/L at 25 °C and a contact time of 30 min. The kinetic results demonstrated that the adsorption behavior of CTAB‑MMT followed the pseudo‑second‑order model. Analysis of the equilibrium data indicated that the Langmuir model provided a better fit, suggesting that the adsorption process involves multilayer accumulation on heterogeneous surfaces. Thermodynamic calculations revealed that the positive ΔH value confirms that the adsorption experiment is endothermic, whereas the negative ΔG values indicate that the process is spontaneous under the given experimental conditions. These results demonstrate that CTAB‑MMT is an effective adsorbent for dye removal from wastewater and holds significant potential for applications in industrial effluent treatment.