Abstract
Foam separation experiments were carried out in SDBS (sodium dodecylbenzene sulphonate)-MgCl2 solution system. For the surface excess of metallic ion, a model was derived on the basis of the Gouy-Chapman theory of the diffuse double layer in the same way as that by Rubin et al. In the model, the contribution of anions to the total charge density was taken into account between the distances of closest approach of two different cations. To obtain the values of surface excess of magnesium, ΓMg2+, the present model was numerically solved by introducing the experimental values of surface excess of DBS- (dodecylbenzene sulphonate ion), ΓDBS-, and by introducing the calculated values of TDBS-, respectively. Below the critical micelle concentration (CMC), there was a reasonably good agreement between these calculated values of ΓMg2+ and experimental ones. It was also indicated that the present model having the calculated ΓDBS- is equivalent to the Langmuir equation far below the CMC.
