Abstract:

The dynamic surface dilational properties of C12E8 aqueous solution were investigated by the damped longitudinal wave method. The comparison between the experimental resultant and the three adsorption models (diffusion controlled, adsorption-desorption controlled and mixted model) shows that bellow the cmc the adsorption and desorption rate is rapid and the rate of adsorption is controlled by the diffusional exchange between bulk and subsurface with the diffusion coefficient which is dependent on the concentration at lower concentration and independent of concentration at higher concentration. The effects of the increase of the limiting dilational modulus at high frequency and the characteristic frequency of relaxation when the concentration of C12E8 increase has been related to the restoration mechanism of surface tension gradient due to the stretched surface.

Key words: Surface adsorption model, Frumkin state equation, Diffusion coefficient, Relaxation characteristic frequency, Limiting dilational modulus