A Comparative Kinetics and Thermodynamics Sorption Analysis on The Impact of Molecular Architecture of Palmitate, Oleate And Laureate Adsorption on Barite in Aqueous Solution

This study comparatively investigated the sorption of sodium laureate, sodium palmitate and sodium oleate on barite in aqueous solution taking into consideration the effect of molecular architecture (hydrocarbon chain length and degree of unsaturation) on the sorption mechanism. The effects of initial concentration, pH, adsorbent dosages, temperature and contact time for each of the adsorbates were investigated and the results obtained were analyzed using Langmuir and Freundlich isotherms and Pseudo first and Second orders. Adsorption of sodium laureate, sodium palmitate and sodium oleate on barite increases with increase in contact time, pH, temperature and initial concentration while increase in adsorbent dosage decreases spontaneously in all cases. Values of the correlation coefficients, shows that Langmuir isotherm is best for describing the adsorption of sodium laureate and sodium oleate onto barite in aqueous solution as compared to the Freundlich isotherm. For sodium palmitate, the Freundlich isotherm is best for describing the adsorption. From the R2 values of pseudo-first and pseudo-second orders, it can be observed that pseudo-second order is the best fit kinetic model for describing the adsorption of all three soap molecules on barite. Specifically, in terms of correlation, Napalmitate>Naoleate>Nalaureate. The adsorption capacity qe values for the pseudo-second order are 1.02, 2.05 and 1.13 for each of the soap similar to the K2 respectively. It has been confirmed in this study that molecular architecture of fatty acids (specifically sodium laureate, palmitate and oleate) significantly influences their adsorption behavior on barite surfaces in aqueous solutions. Chain length promotes stronger hydrophobic interaction, while unsaturation introduces (cis-double bonds) structural kinks that reduce packing density. Palmitic acid, due to its long, saturated chain, exhibits the highest adsorption affinity and stability, while oleic acid offers a balance of surface activity and molecular flexibility. Lauric acid, though more soluble, demonstrates lower adsorption potential due to its short chain and weaker interactions. The positive change in showed that the reactions were endothermic and the increasing randomness of soap molecules is driven by the positive values of with the highest form of randomness in pamitate>oleate>laureate. The values of the standard free energy are beyond 0 and -20 kJ/mol, asserting that the adsorption is physico-chemical sorption mechanism, reflecting the influence of physico-chemical interactions between the soap molecules and barite. This can also be asserted to the molecular architecture which favours the adsorption of the three acids in order of palmitate>oleate>laureate due to the influence of chain length and degree of saturation. The finding of this study underlines the importance of understanding the interaction between different surfactants and barite surfaces, which can have implication in mineral.