Adsorption Kinetics of C₁₂E₈ at the Air−Water Interface:  Adsorption onto a Clean Interface

Abstract

The adsorption of C12E8 onto a clean air-water interface is studied by using a video-enhanced pendant bubble tensiometry. The controlling mechanism for mass transfer changes as a function of bulk concentration; it shifts from diffusion control at dilute concentration to mixed diffusion-kinetic control at more elevated bulk concentration. The adsorption of C 12E8 is found to be anticooperative from the equilibrium surface tension data compared with the prediction of the (generalized) Frumkin model. Relaxation profiles of surface tension for C12E8 molecules absorbing onto a freshly created air-water interface for 21 different bulk concentrations are obtained. Comparison is made for the entire relaxation period of the tension data and the model predictions. Values of the diffusion coefficient and the adsorption/ desorption rate constants of C 12E8 are calculated from these dynamic surface tension profiles.

Microscale tipstreaming in a microfluidic flow focusing device

“…Surface tension values measured for the air-water interface agree well with values reported in the literature. 41 Values of the CMC obtained from both air-water and oil-water surface tension measurements are in good agreement, as expected. To ensure that the surface tension has reached an equilibrium value, we also measure the interfacial tension after 12 h and we observe very little change.…”

Adsorption Behavior of Oxyethylated Surfactants at the Air/Water Interface

“…that the data given in (15) for C 12 EO 8 are in satisfactory agreement with those presented in (13,17) only in the concentration range above 3 × 10 −6 mol/L. For lower concentrations the values given in (15) (not shown in Fig.…”

“…1 and 2 for a broad range of n C (13,16,17). For some compounds, data from different authors are presented, which are in good mutual agreement.…”

“…This tendency is observed also with an increasing number of oxyethylene groups in the C n EO m molecule. The experimental surface pressure isotherms of C n EO m for various m and fixed n (n = 10 and n = 12, respectively) obtained in (13,14,(16)(17)(18)(19)(20)(21) are shown in Figs. 3 and 4.…”

Estimation of Trioctylphosphine Oxide (TOPO) Diffusion Coefficients by Dynamic Adsorption Measurements in Model Extraction Systems

“…On the other hand, Lin et al (30,31) in studies on polyoxyethylene alcohols in air/water systems concluded that the controlling mechanism for mass transfer can change from diffusion to mixed kinetic-diffusion control as a function of bulk concentration. By examining how D changes with concentration they suggested a diffusion-controlled mechanism at dilute bulk concentrations, where the equilibrium surface coverage is low, and a mixed kinetic-diffusion control as the bulk concentration becomes higher and the equilibrium surface coverage is increased.…”