Adsorption isotherms for oleic acid removal from ethanol plus water solutions using the strong anion-exchange resin Amberlyst A26 OH

摘要

Adsorption isotherms for the removal of oleic acid from ethanol + water solutions using a strong anion-exchange resin (Amberlyst A26 OH) were experimentally determined. The equilibrium data were correlated using the Langmuir model by adjusting the parameters q(m)/(g of acid-g of dry resin(-1)), maximum content that can be adsorbed on solid phase, and K-d/(g of acid(.)g of solvent(-1)), the equilibrium constant. The Freundlich and Redlich-Petersen models were also used, but the Langmuir model shows the lower average deviations between experimental and calculated results. The behavior and the capacity of the resin to remove the fatty acid from the liquid phase were evaluated at different experimental conditions: the water content in ethanol was varied within the range (0 to 15) mass %, and two equilibrium temperatures were investigated: (298.15 and 313.15) K. It was observed that both variables, water content in ethanol and equilibrium temperature, do not significantly influence the equilibrium behavior. It was also observed that the strong anion-exchange resin (Amberlyst A26 OH) has a good performance in the removal of the fatty acid from the liquid phase. To determine exactly the mechanism for the uptake of oleic acid by the resin, equilibrium experiments were done with different oleic acid concentrations (7, 9, and 11) mass % in solution with water content in ethanol (0.57 +/- 0.01) mass % at 298.15 K. In this way the concentration of oleic acid in resin phase was determined, and it was observed than the most important mechanism of uptake is the ion exchange.