Simultaneous adsorption of anionic alkyl sulfate surfactants onto alpha alumina particles: Experimental consideration and modeling
2021
Doan, Thi Hai Yen | Lê, Thị Thủy | Nguyễn, Thị Minh Thu | Chu, Thi Hue | Pham, Thi Ngoc Mai | Nguyen, Thi Anh Huong | Pham, Tien Duc
Simultaneous adsorption of four anionic alkyl sulfate (AS) surfactants, including sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate and sodium tetradecyl sulfate named as C8, C10, C12 and C14, onto alpha alumina (α-Al₂O₃) particles were systematically investigated. Concentrations of all mixtures of anionic AS surfactants in aqueous solution were quantified by capillary electrophoresis coupled with contactless conductivity detection (CE-C⁴D). Adsorption isotherms of the four anionic AS surfactant homologs increased with either the decrease of pH from 6.0 to 4.0 due to enhancement of electrostatic attractions between the positively charged α-Al₂O₃ surface and the anionic AS surfactants or the increase of carbon chain length due to enhanced hydrophobic interactions. At different salt concentrations, a common intersection point (CIP) obtained for adsorption isotherms demonstrated that the contributions of electrostatic and hydrophobic interactions were reversed. The ionic strength effect on anionic AS surfactant adsorption isotherms onto α-Al₂O₃ particles was thoroughly studied. Simultaneous adsorption of the four AS surfactants onto the α-Al₂O₃was controlled by both electrostatic and hydrophobic interactions that were in accordance with Langmuir and two-step models.
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