Canadian Journal of Chemical Engineering, Vol.72, No.3, 551-553, 1994
Adsorption of Sodium Dodecyl-Sulfate on Cassiterite Surface
Measurements of the adsorption of sodium dodecyl sulphate (SDS) onto cassiterite were made. It was found that at SDS concentrations below 10(-3) mol/L the adsorption depended on the manner of preparation of the cassiterite and the pH of solution. However, the adsorption isotherms showed a point of inflection at 10(-3) mol/L corresponding to an occupied area per molecule of about 0.8 nm2. This value is close to the surface area covered by one dodecyl sulphate ion (DS-) as evaluated from the molecular structure of SDS. Near the critical micelle concentration (cmc), a plateau was found which corresponded to the adsorption of two statistical monolayers of DS- ions vertically oriented to the surface.