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Abstract
The adsorption kinetics of the double‐chain surfactant AOT and NaDEHP are comparatively investigated by dynamic surface tension (DST) measurements. The parameters n and t* representing the diffusion speed of the surfactant molecules from bulky solution to the sublayer and from the sublayer to the surface are obtained according to the equation proposed by Rosen. The results show that the values of n and t* both decrease with the increase of the surfactant concentrations. While the n value of the AOT system is smaller than that of NaDEHP and the t* is the inverse, indicating the faster diffusion of AOT molecules and the larger adsorption potential for NaDEHP molecules. The effect of the salt on the dynamic adsorption course is also studied. The results show that the decreasing rate of the DST for the two surfactants both increase with the rise of NaCl concentration; however, the effect of NaCl on AOT is stronger than that on the NaDEHP system. This result is in agreement with the equilibrium surface tension result.
Acknowledgments
The authors gratefully appreciate the financial support from the NSF of Shandong Provice (Y2004B06) and the Key Project of China (2004BA313B20).