Silica Xerogel Modified with Cetyltrimethylammonium Bromide as an Effective Adsorbent for Methyl Orange Dye

The study of water treatment technologies has been growing due to mounting concerns regarding dye contamination. Adsorption-based technologies that use porous materials have been proven useful in water decontamination. However, porous silica xerogels have not been extensively explored as adsorbents for the methyl orange (MO) dye. In this study, the MO-adsorptive behavior of silica xerogels was investigated. Two silica xerogels were synthesized using tetraethyl orthosilicate, and one was modified with cetyltrimethylammonium bromide (CTAB). The adsorptive capacities of the unmodified silica xerogel (SiO2-UN) and the CTAB-modified silica xerogel (SiO2-CTAB) were compared. Results showed a better fit to the Langmuir isotherm model, with maximum adsorbed amounts of 1.52 mg g-1 and 25.5 mg g-1 for SiO2-UN and SiO2-CTAB, respectively. The higher value for SiO2-CTAB is mainly attributed to the electrostatic interactions between MO and the ammonium groups present in the modified xerogel. A study of the porosities of both xerogels, using N2 adsorption and desorption isotherms, indicated the samples were mesoporous. These findings suggest that SiO2-CTAB exhibits favorable MO adsorption and could be employed in future wastewater treatment processes.