Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (2): 445-452.doi: 10.3866/PKU.WHXB201512013

• ARTICLE • Previous Articles     Next Articles

Density Functional Theory Study of the Interaction between Sodium Dodecylbenzenesulfonate and Mineral Cations

Zhi-Hong LIU1,Cheng-Cheng FAN2,Tian-Tian ZHANG2,Xian-Jing JI2,Sheng-Hui CHEN2,Shuang-Qing SUN2,3,Song-Qing HU2,3,*()   

  1. 1 Geological Scientific Research Institute, Shengli Oilfield Company Ltd., Dongying 257015, Shandong Province, P. R. China
    2 College of Science, China University of Petroleum (East China), Qingdao 266580, Shandong Province, P. R. China
    3 Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong, Qingdao 266580, Shandong Province, P. R. China
  • Received:2015-07-28 Published:2016-01-30
  • Contact: Song-Qing HU E-mail:ccupc@upc.edu.cn
  • Supported by:
    the PetroChina Innovation Foundation, China(2015D-5006-0213);Fundamental Research Funds for the CentralUniversities, China(14CX02221A, 14CX06157A)

Abstract:

Investigating the interactions between anionic surfactants and cations is of great theoretical and practical significance to understanding the precipitation and solubility of anionic surfactant products but relevant theoretical interaction models are seldom reported. In this paper, the density functional theory (DFT) method was used to investigate the interactions of the dodecylbenzenesulfonate anion (DBS-) with Na+, Mg2+, and Ca2+ both in the solution and at the air/water interface. In the solution, DBS-/cation interaction models were built and optimized with consideration of two different solutions (i.e. water and n-dodecane). The results indicate that DBScan bind stably with the cations in a bidentate form. The binding energy of the DBS-/cation depends on the properties of both the participating cation and the solvent. At the air/water interface, DBS- formed a stable hydrated complex with six water molecules (i.e. DBS-·6H2O). However, the structure of DBS-·6H2O was greatly disturbed by the introduction of the cation. A dimensionless parameter, def, was proposed to evaluate the deformation extent of the hydration shell. The degree of disturbance by the cations follows the order: Ca2+ >Mg2+ > Na+. A charge analysis reveals that the hydration shell plays an important role in the interactions between the sodium dodecyl benzene sulfonate (SDBS) headgroup and the cation.

Key words: SDBS, Cation, Interaction, Air/water interface, Charge distribution, Density functional theory

MSC2000: 

  • O641