Adsorption of Palmitate on Calcite in Aqueous Solution: An Initial Rate and Thermodynamics Study

This study demonstrates the importance of understanding the thermodynamic and kinetics aspects of adsorption processes considering the attention drawn towards improving the adsorptive behaviours of fatty-acids soaps onto calcite. In view of the nexus between the surface tension of solutions of fatty acid soaps, traveling microscope was used to measure the concentrations of adsorbate filtrates with which parameters for five adsorption isotherm models namely; Langmuir, Fruendlich, D-R, Temkin and Elovich were employed in assessing the adsorption behaviour of sodium palmitate on calcite in aquous solution. Despite the high correlation R2 values of 0.9466 and 0.9732 shown by Langmuir and Fruendlich isotherms respectively, the Temkin isotherm having the highest R2 value of 0.9821 indicates an excellent fit between the experimental data, suggesting that the model accurately describes the adsorption process of palmitate on calcite. The Temkin isotherm assumes a uniform adsorption energy, implying that the adsorption process occurred with a consistent energy distribution with the AT value of 0.205 L/mg signifying a moderate adsorption capacity and that palmitate molecules were effectively adsorbed from the solution. The bT value (0.986 L/g) point to a strong interaction between palmitate and calcite, suggesting that the adsorption process is favorable and the adsorption process occurred with a consistent energy distribution. The initial rate increased with increase in initial concentration. The high frequency factor and the low activation energy values determined were 8.58 x and 9.14 J/mol.K respectively inferring that the the reaction proceeds relatively fast due to increased collision and low steric hindrance in the adsorption reaction. Palmititate therefore, is a reliable adsorbate for the concentration of calcite in mineral beneficiation and/or flotation.