Chem. J. Chinese Universities ›› 2025, Vol. 46 ›› Issue (4): 20240421.doi: 10.7503/cjcu20240421

• Physical Chemistry • Previous Articles     Next Articles

Micellar Behavior of Sodium Dodecyl Sulfate in NaCl/NH4Cl-C2H5OH-H2O Solution

CHENG Wenting(), ZHAI Ying, LI Qianqian, CHENG Fangqin   

  1. Institute of Resourees and Environental Engineering,Shanxi University,Taiyuan 030031,China
  • Received:2024-09-09 Online:2025-04-10 Published:2025-01-18
  • Contact: CHENG Wenting E-mail:wtcheng@sxu.edu.cn
  • Supported by:
    the National Key Research and Development Program of China(2022YFC3901305);the National Natural Science Foundation of China Youth Project(22208198)

Abstract:

In the recycling treatment of NaCl and NH4Cl type pesticide waste salts, the crystalline separation of the salts is often regulated by the surfactant sodium dodecyl sulfate(SDS) micelles and ethanol, so the study of the micellization behaviour of SDS in the waste salt system is crucial to achieve the precise regulation of this process. Among them, the critical micelle concentration(CMC) of SDS in waste salt system is an important parameter for its micellization behaviour. The critical micellar concentration values of SDS in four systems, NaCl-H2O, NH4Cl-H2O, NaCl-C2H5OH-H2O and NH4Cl-C2H5OH-H2O, were determined using the surface tension method in the temperature range of 293.15—323.15 K. The effects of temperature, salt solution concentration and ethanol content on the micellar behavior of SDS were studied. The results showed that the CMC values of SDS in both salt solutions increased with the increase of temperature without adding ethanol, while the CMC values of SDS decreased with the increase of salt concentration at the same temperature. After the addition of ethanol, the CMC values of SDS in NH4Cl solution increased significantly, while it showed a tendency to decrease first and then increase in NaCl solution. Three standard thermodynamic parameters for the micellar behavior of SDS were calculated by mass action model: standard molar Gibbs free energy changes(ΔGm 0 ), standard molar enthalpy change(ΔHm 0 ) and standard molar entropy change(ΔSm 0 ). From the calculation results, it is clear that the micellar behaviors of SDS are all spontaneous and exothermic. In the NaCl-C2H5OH-H2O system, the addition of ethanol first promotes and then inhibits the formation of SDS micelles. While in the NH4Cl-C2H5OH-H2O system, the addition of ethanol always inhibits the formation of SDS micelles.

Key words: Sodium dodecyl sulfate, Critical micellar concentration, Surface tension, Thermodynamic parameter

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