Study of the Adsorption of Dodecylammonium Chloride on a Labradorite

Abstract

The adsorption isotherms of dodecylammonium chloride on silica and labradorite at natural pH and for various pH values were determined using a radioactive form of the reagent. The effect of Ca ion and Na ion on the adsorption of dodecylammonium chloride on silica and labradorite was also investigated.
The results of adsorption tests of dodecylammonium chloride on both silica and labradorite indicated that there is a significant difference between both adsorption mechanisms. Namely, dodecylammonium ions adsorb at Stern layer on quartz surface as counter ions, on the other hand, dodecylammonium ions mainly adsorb on the labradorite surface by ion exchange, viz, by exchanging Na ions or Ca ions which are lattice cations of labradorite.
The effect of pH on the adsorption of dodecylammonium ion on both silica and labradorite showed a similar tendency, however, the mechanisms differ from each other. On silica surface, H ion is potential determining ion and so controls adsordtion of dodecylammonium ion as counter ion in the Stern Layer. On the other hand, since Na ion and Ca ion which are lattice cations of labradorite are exchanged easily by H ion in acldic side, H ion is a competitor to the dodecylammonium ion for labradorite surface.
The effect of Ca ion on the adsorption of dodecylammonium chloride on silica and labradorite was less than the effecf of H ion, but it was signmcant.