Adsorption of carotene and free fatty acid from palm oil onto raw and activated montmorillonite clay has been studied. Acid activation lead to the leaching of exchange cations (Ca 2+ , K + , Na + , Mg 2+ ) and of ferric ions (Fe 3+ ).Acid activated clay has better carotene and free fatty acid adsorption capacities than raw clay. However, leaching of clay with high concentrated acid solution reduced its adsorption efficiency. The amount of carotene adsorbed per gram of adsorbent also increased with temperature, notwithstanding the acid treatment of clay.The kinetics of carotene and free fatty acid were best described by pseudo-second order and intraparticle diffusion models. The activation energies obtained by applying Arrhenius equation to the pseudo-second order kinetic constant were all lower than 24 kJ.mol -1 . It was concluded that there are different types of adsorption sites for carotene adsorption as the adsorption isotherms did not fit Langmuir equation, but they fit very well Freundlich and Temkin models. These observations were also valid for free fatty acids adsorption. The small values of Freundlich constant n, and of Temkin constant B, show the loose bonding of carotene and free fatty acids on clay surface. Hence the adsorption of these 2 compounds is a physisorption.
In the present study, a Cameroonian smectite was used as an adsorbent to model the adsorption kinetics of three textile dyes (malachite green, methyl red and acid blue 74) from aqueous solution in a batch system. The effects of pH and temperature were evaluated on the adsorption capacities, the times required to reach adsorption equilibrium and the adsorption mechanisms involved. It can be seen that, although the times required to reach the adsorption equilibrium are independent of the pH of the medium, the adsorption process studied is favourable in acidic media and is globally independent of temperature. Among the pseudo-first and pseudo-second-order kinetic models used to analyse the experimental data, the pseudo-secondorder model was the best suited to describe the adsorption of the three dyes onto the clay. The mechanism involved, independently of the dye, is therefore a two-step process: the transfer of dye molecules from the solution to the clay surface followed by the interaction between the molecules and the surface. The low value of activation energies indicates that the adsorption of Methyl red, Malachite green and Acid blue 74 on the studied clay is a physisorption process.
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