Adsorptive separation of propionic acid from aqueous medium using efficient anion exchange resins in batch and fixed bed column systems

The recovery of propionic acid (PA) from aqueous medium using a strongly basic, Lewatit M-600 (LM-600), and a weakly basic, Lewatit MP-62 (LMP-62), anion exchanger was investigated. Medium conditions such as pH, temperature, PA concentration, and resin dose affected the performance of the process. The highest capacities were achieved at pH 5 and 2 with LM-600 and LMP-62, respectively. Equilibrium was reached in 35 min, and the process followed the pseudo-second-order kinetics for both anion exchangers. LMP-62 was more effective at pH values lower than 5. The exothermic process was found to be spontaneous. The maximum capacities of the strong and weak basic exchangers in batch experiments were 135.7 and 363 mg/g, respectively. However, the breakthrough capacities obtained in fixed bed systems were lower than those attained in batch systems (94.75 and 123.73 mg/g for LM-600 and LMP-62, respectively), and the column was successfully regenerated using 0.6 M NaOH. The Freundlich isotherm model yielded the highest determination coefficients in the isotherm analysis, suggesting that physical forces between PA and resins primarily drive the process.