Novel synthetic clays for the adsorption of surfactants from aqueous media

The aim of this work was to assess for the first time the use of two high-charge swelling micas (Na-Mica-4 and C₁₈-Mica-4) for the removal of four linear alkylbenzene sulfonates (LAS) from aqueous samples. To this end, Na-Mica-4 was synthesized and organically functionalized with cations of octadecylamine to obtain C₁₈-Mica-4. Na-Mica-4 and C₁₈-Mica-4 were characterized by X-Ray diffraction, Zeta potential, specific surface area and thermogravimetric analysis before and after the adsorption experiments. LAS removal studies were carried out in water samples spiked with a LAS mixture (10 mg L^-1). Removal rates with C₁₈-Mica-4 were between 94% and 97% at pH = 2, and between 98% and 99% at pH = 5 after 1 h. For the same amount of Na-Mica-4, removal rates were between 54% and 81% at pH = 2, and between 24% and 66% at pH = 5 after seven days. No significant effects on the removal rates of C₁₈-Mica-4 were observed for pH values between 0.5 and 9. The experimental equilibrium data were fitted to 30 min, with removal rates of up to 98% in all the experiments. C₁₈-Mica-4 characterization tests indicate that LAS adsorption occurs in the interlayer space. Finally, C₁₈-Mica-4 was applied successfully to the removal of the target compounds from influent and effluent wastewater, surface water and tap water samples.