Acta Phys. -Chim. Sin. ›› 2001, Vol. 17 ›› Issue (12): 1122-1125.doi: 10.3866/PKU.WHXB20011213

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Surface Activity of Mixed System of Dodecyl Betaine and Sodium Dodecyl Sulphate

Zhang Zhi-Qing;Xu Gui-Ying;Ye Fan;Zheng Li-Qiang;Luan Yu-Xia   

  1. Key Laboratory for Colloid and Interface Chemistry of Education Ministry,Shandong University, Jinan 250100
  • Received:2001-05-07 Revised:2001-09-17 Published:2001-12-15
  • Contact: Xu Gui-Ying

Abstract: The ability of forming micell, the efficiency and the ability of reducing surface tension by the interaction of zwitterionic and anionic surfactants (C12H25N+(CH3)2 CH2COO-/C12H25SO4Na) has been investi- gated. It is found that when the molar fraction of C12BE is about 0.6, the surface activity shows a maximum. The influence of NaCl and alcohols on surface properties of the mixed system has also been studied. The surface activity is enhanced and the cmc value of C12BE/SDS system is reduced with the increase of NaCl concentration, because sodium ions induce a decrease of electrostatic repulsion between hydrophilic groups in surfactant molecules. The effect is more complex with the addition of alcohols, the surface activity improves with increasing the volume fraction of n-butanol. But no remarkble influence on surface activity has been observed for alcohols of short chain, for example ethanol.

Key words: Dodecyl betaine(C12BE), Sodium dodecyl sulphate(SDS), Critical micell concentration (cmc), Surface tension, Synergism