Separation of propionic acid with anion exchangers from aqueous solutions

In this MS thesis, the recovery of propionic acid from aqueous solutions by two different commercial anion exchangers was investigated. Kinetic effects of several parameters on the process efficiency were probed while thermodynamic, and equilibrium studies were performed. Lewatit MP-62 and Lewatit M-600 were tested in the study. The pH of the media significantly influenced the efficiency. The highest separation efficiency was obtained at the natural pH of the solution (pH = 2.5) with Lewatit MP-62 and at pH = 5 with Lewatit M-600. Both systems reached the equilibrium by 35 min. In addition, both systems were observed to follow the pseudo second order kinetic model. The adsorption percent decreased with the increase in temperature and the ΔH˚ and ΔG˚ had negative values. This means that the process was spontaneous and had an exothermic nature with these resins. Separation efficiency was seen to increase with the increase in resin dose and decrease with the propionic acid concentration. The maximum adsorption capacity (362,99 mg PA/g resin) and separation efficiency (96,8%) were obtained with Lewatit MP-62. The equilibrium were observed to be in agreement with the Freundlich isotherm model. Howewer, a more detailed isotherm should be performed in order to understand the mechanism with there resins. Keywords: Adsorption, Anion exchange resins, Kinetic, Ion exchange, Propionic acid, pH, Thermodynamic