Separation of Formic Acid from Aqueous Solutions onto Anion Exchange Resins: Equilibrium, Kinetic, and Thermodynamic Data

Wastewaters containing organic compounds such as acids, ketones, phenols, and amines can cause critical environmental problems depending on their concentration and composition. Efficient and low-cost separation of these components may also bring their reuse in industry while cleaning the aqueous streams. Formic acid (FA) is an important raw material in industry and is widely seen in wastewaters. In this study, two different anion exchangers were compared for the separation of FA from aqueous solutions. Effects of process parameters and the mechanism were discussed. Kinetic, equilibrium, and thermodynamic studies were performed, and the data were interpreted using the relevant isotherm and kinetic models. The results showed that Lewatit MP-64 was more efficient than Amberlite IRA-96 in the range of the parameters studied. The maximum adsorption capacity obtained with Lewatit MP-64 (442.75 mg/g) was significantly higher than that were previously reported in the literature for FA separation. The data were well explained by the Langmuir isotherm model. However, relatively high R-2 values were obtained with Temkin and Freundlich isotherms. Therefore, further studies are ongoing to clarify the mechanism.