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测定了不同摩尔比的全氟辛酸钠(7CFNa)-十烷基硫酸钠(C_(10)SNa)混合水溶液(加NaCl,恒定离子强度μ=0.1m)的表面张力和界面张力(正庚烷-水溶液界面张力)。由表(界)面张力-浓度关系求出混合体系的表(界)面吸附和临界胶团浓度(cmc)。结果表明:(1)7CFNa和C_(10)SNa在μ=0.1m的溶液中,cmc相近,两者表面活性相近;但7CFNa降低水表面张力的能力较强,在cmc时的表面张力可低达～23mNm~(-1)。因此,在混合溶液的表面上,7CFNa的表面活性较高,优先吸附于表面。对于各种摩尔比的混合溶液,7CF~-在表面层中的比例皆大于在溶液内部的比例。(2)正庚烷-水溶液界面上的吸附与表面吸附截然不同。7CF~-在界面吸附层中的比例低于溶液内部,表明其吸附能力比C_(10)S~-为弱。这是由于界面一边的正庚烷与C_(10)SNa碳氢链之间的作用大于与7CFNa碳氟链之间的作用。亦即碳氟链与碳氢链“互憎”作用在界面上的表现。(3)在不同摩尔比的混合溶液中,各组分的cmc接近一恒值,进一步说明混合溶液中存在碳氟链与碳氢链间的互憎作用,以致两种表面活性剂在混合溶液中(有过量无机盐时)基本上各自形成胶团。
The surface tension and interfacial tension (n-heptane-water solution) of mixed aqueous solution of sodium perfluorooctanoate (CFC (10) SNa) with different molar ratio of sodium perfluorooctanoate Interfacial tension). The surface (boundary) surface adsorption and critical micelle concentration (cmc) of the mixed system were determined from the surface tension (tension) -concentration relationship. The results show that: (1) 7CFNa and C_ (10) SNa have the similar cmc in μ = 0.1m solution, but the surface activity of 7CFNa and C_ (10) SNa are similar, but the surface tension of 7CFNa is lower. Up to ~ 23mNm ~ (-1). Therefore, 7CFNa has a higher surface activity on the surface of the mixed solution, preferentially adsorbed on the surface. For the mixed solution with various molar ratios, the proportion of 7CF ~ - in the surface layer is larger than that in the solution. (2) The adsorption on the n-heptane-water interface is quite different from the adsorption on the surface. The proportion of 7CF ~ - in the adsorbed layer was lower than that in the solution, indicating that its adsorption capacity was weaker than that of C_ (10) S ~ -. This is because the interaction between the n-heptane and the C 10 Cl SNa on the interface side is larger than that between the 7 CFNa fluorocarbon chain. That fluorocarbon chain and hydrocarbon chain “mutual hate” role in the interface performance. (3) The cmc of each component is close to a constant value in the mixed solution with different molar ratio, which further explains the mutual hate between the fluorocarbon chain and the hydrocarbon chain in the mixed solution, so that the two surfactants in the mixed solution (In the case of excess inorganic salts) essentially form micelles.