Cationic Organo-Montmorillonite for Efficient Concomitant Removal of Anionic Dyes in Single and Multi-components' solutions: Adsorption Characteristics and Mechanism Study

This study aimed to create an organoclay [MMT@CTAB] by mixing the naturally occurring mineral montmorillonite [MMT] with the cationic surfactant cetyltrimethylammonium bromide [CTAB]. FTIR spectroscopy, elemental analysis and scanning electron microscopy [SEM] have been employed to analyze both the unmodified MMT and the MMT that has been modified using CTAB [MMT@CTAB]. The MMT@CTAB adsorbent was investigated for the removal of methyl orange (MO) and Rose Bengal (RB) anionic dyes (in single and/or in multi-components solutions) and additionally, in batch and column modes. Certain variables that impact the adsorption process, such as initial dye concentration, contact time, temperature, pH, and adsorbent dose, are evaluated. The kinetic investigation, which is characterized by a pseudo-second-order kinetic model, reveals that equilibrium adsorption of MO and RB dyes onto MMT@CTAB may be attained in 60 and 120 minutes, respectively. MO and RB were expected to achieve maximum adsorption efficiencies of 98.7 and 98.4%, respectively, at 100 and 150 mgL-1 concentrations, a dosage of 0.5 gL-1 adsorbent, and an initial pH of 7. In addition, Langmuir model best fits the sorption isotherm data, with the maximum adsorption capacity at 303 K being 203.25 mg g-1 for MO and 304.878 mg g-1 for RB, as shown by the non-linear form of Langmuir isotherm. Regenerated MMT@CTAB may be used for at least four more adsorption/desorption cycles, with ethanol indicating to be the most effective regeneration eluent. Each anionic dye was subjected to a binary systematic analysis. Since the adsorption of these anionic dyes onto MMT@CTAB was reduced when the temperature was increased, thermodynamic evidence suggests that adsorption is an exothermic, spontaneous process. The prepared cationic organoclay MMT@CTAB was successfully applied for the removal of MO and RB from real water samples and synthetic effluents with a recovery % more than 95%. The plausible adsorption mechanism of MO and RB onto MMT@CTAB is proposed to be due to electrostatic interaction and hydrogen bond formation. Finally, our study shows that MMT@CTAB may be employed efficiently and effectively to remove anionic dyes from a wide range of the collected real water samples.