Adsorption Isotherm and Surface Tension Equation for a Surfactant with Changing Partial Molar Area. 1. Ideal Surface Layer

Abstract

An adsorption model is proposed which assumes a different partial molar surface ω for adsorbed molecules depending on the degree of saturation of the adsorption layer. Equations for an adsorption isotherm and a surface tension isotherm are derived for the adsorption of one single surfactant or of a mixture of surfactants. The model assumes that the molecules may adsorb in two different states, i.e. a large ω at smaller surface pressures Π and a smaller ω at large surface pressures Π. Adsorption data of (N-n-hexadecyl-N,N-dimethylammonio)acetic acid bromide at the air/solution interface are used to demonstrate the application of the theory. The experimental results are in very good agreement with the model.

Equilibrium and dynamic surface properties of trisiloxane aqueous solutions. Part 2. Theory and comparison with experiment

“…The theoretical two states models were used to describe the equilibrium surface tension and adsorption of surfactants and were described in earlier elsewhere [6,[7][8][9][10]. Therefore, only the main equations for each applied model are given below.…”

“…Assuming ideal enthalpy of mixing of the surface layer, the equations of state and adsorption isotherm read [7][8][9]:…”

Effect of impurities in the description of surface nanobubbles: Role of nonidealities in the surface layer

“…In our previous paper [19], we have compared the ideality-based model for nonionic impurities with the same experimental results. Corresponding values of the parameters K 1 (obtained directly from the corresponding estimate of b 1 ) and ω 1 are obtained from the literature [40,41] (see Table I for details). For the chosen value of K 1 , the results from the present simulation shows a much better fit to the experimental result as compared to our previous model [19].…”

“…2(a). The idea of the partition coefficient K 1 is obtained from the corresponding b 1 values provided in [40,41]. The partial molar areas ω 1 are obtained from [40,41].…”

“…The experimental result (obtained from [40,41]) is shown by open squares, whereas the simulation result is denoted by continuous lines (the case with nonideality is represented by bold lines whereas that without nonideality is represented by dashed lines). The different parameters used for obtaining the simulation plots are tabulated in Table I.…”