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Interaction between dye (ECAB), nonionic surfactant (TX-100) micelle in aqueous solution and TX-100 hemimicelie at solid (SiO2)/liquid interface has been investigated quantitatively. There are linear relationships between concentrations of free ECAB(Ca), ECAB bound with TX-100 micelles in solution(Cm) and ECAB bound with TX-100 hemimicelles at interface of solid/liquid(Chm). The slopes of the three straight lines are 0.32 for Chm∼Ca -1.32 for Cm∼Ca and -1.00 for (Cm+Chm∼Ca respectively. The linear relationships can be described by three linear equations as follows: Chm=0.32 (Ca−O.88×10−5),Cm.=4.0×10−5-l.33 Ca and Chm+Cm=3.742×l0−5-Ca,. It is inferred that the interaction between ECAB, TX-100 micelles and TX-100 hemimicelles is essentially partition of ECAB molecules in solution, TX-100 micelles and hemimicelles. The concentration of ECAB bound with TX-100 micelles well as electronic repulsion. Additionally, A quantitative method to determine adsorbance of surfactant TX-100 on silica gel by spectr...

The effects of added inorganic salts (NaCl and NaBr), alcohols (C2H5OH and n-C4H9OH) and urea on the adsorption of alkylpyridinium halides from aqueous solution on silica gel have been investigated at 25 °C. The results show that all the adsorption isotherms exhibit two plateaux either with or without various additives. In the first plateau the surface-active cations are adsorbed as individual ions on the negatively charged silica gel surface through both electrostatic attraction and specific adsorption. Then, at a particular concentration known as the hemimicelle concentration (h.m.c.), the adsorption increases dramatically as hemimicelles form on the adsorbent through association between hydrocarbon chains of the adsorbed molecules. As the concentration increases further, the adsorption reaches the second plateau somewhere above the c.m.c. of the surfactant. Based on the assumption that each adsorbed surface-active cation in the first plateau is an active centre for surface aggregation, the minimum average aggregation number of hemimicelle, nhm, is equal to the ratio between the adsorption amounts of two plateaux, Γ∞2nd and Γ∞1st, or, more generally, between Γcmc and Γhmc, the values of adsorption at the c.m.c. and h.m.c. respectively. The results show that the nhm for alkylpyridinium halides in various media studied in this work is mostly in the range 6–18. The addition of inorganic salts and alcohols will increase and decrease the value of nhm, respectively. The approach for determination of the number of surfactant ions in a hemimicelle from the adsorption isotherms proposed by Chander et al. [S. Chander, D. W. Fuerstenau and D. Stigter, in Adsorption From Solution, ed. R. H. Ottewill, C. H. Rochester and A. L. Smith (Academic Press, London, 1983), p. 197] has been questioned.