Adsorption of sodium dodecyl sulfate on layered double hydroxides

Layered double hydroxides (LDH), or the so-called anionic clays, are hydrotalcite-like compounds which can be represented by the general formula [M1-x2+Mx3+(OH)(2)](x+) X-x/m(m-) . nH(2)O. They can be used as adsorbents, catalysts and catalyst supports and they present many other industrial applications such as polymer stabilisers and anion exchangers. On the other hand, the surfactants have been widely applied in industrial and household uses, so they constitute an important class of materials of commercial interest. The study of the adsorption of surfactants on these clays is thus very important due to the potential application of these adsorbents in many industrial processes. The adsorption of dodecyl sulfate on a magnesium aluminium layered double hydroxide was studied. The results obtained agree well with those found in the literature for the adsorption of this surfactant on other solids. We could observe that the adsorption follows the two-step model, confirmed by zeta potential measurements. We also observed that the amount of adsorbed surfactant increases with temperature. (C) 1998 Elsevier Science B.V. All rights reserved.