Surfactants modification of kaolin for enhanced mercury adsorption

Clay minerals treated with surfactants are well-known for their excellent ability to adsorb both inorganic and organic substances from aqueous solutions. In this research, we synthesized three different types of organically modified kaolin (K) using two anionic surfactants: sodium lauryl sulfate (SLS) and sodium dodecylbenzene sulfonate (SDBS). Additionally, a combination of both surfactants (M = SLS + SDBS) was developed to enhance the adsorption of mercury from waste water. The samples were characterized using various analytical methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. The results indicated that modifying kaolin with surfactants was effective, leading to significant increases in the specific surface area, reaching 38.3, 31.9, and 17.5 % for K-SLS, K-SDBS, and K-M, respectively. Additionally, the FTIR spectra of the kaolin modified by SLS showed changes in intensity, and two new peaks at 2θ = 21.00° and 42.58° were observed. Furthermore, the kaolin modified by the SDBS surfactant showed a new peak at 2θ = 8.85°, indicating the presence of surfactants. The adsorption of mercury was found to be greater on a kaolin modified with the anionic surfactant SLS than on a kaolin modified with a combination of both surfactants (SLS + SDBS). Finally, kaolin was modified with the anionic surfactant SDBS with values of 17.77, 15.77, and 13.45 mg.g⁻¹, respectively. The results obtained from this study demonstrate that anionic surfactant modification enhances kaolin's surface properties and Hg(II) adsorption capacity, with K-SLS exhibiting the most optimal performance. These findings underscore surfactant-treated kaolin as a promising mercury adsorbent for water treatment applications.