Electromembrane and pervaporation technologies for the production of highly concentrated formic acid from captured CO2 valorization

Abstract

Electro-membrane technologies to salt splitting chemicals such as potassium formate generated during the electrochemical conversion of captured CO₂ to obtain formic acid and potassium hydroxide represents a crucial pathway toward carbon neutrality and circular economy. The study demonstrated that the most effective configuration employed two cation exchange membranes (Nafion 324) to separate the anodic, cathodic and central compartments, with the feed solution circulated through the central compartment. This setup enabled potassium ions to migrate to the catholyte, where KOH was concentrated, while protons generated in the anodic compartment moved into the central compartment, maintaining an acidic pH (≈1) and allowing the concentration of formic acid. Optimal performance was achieved at 1500 A m⁻² and a circulated charge of 0.6715 F, yielding up to 100 g L⁻¹ of formic acid and 140 g L⁻¹ of potassium hydroxide. Additionally, pervaporation using a PERVAP 4101 membrane successfully broke the formic acid–water azeotrope, reaching concentrations up to 90%. This is the first study that demonstrates the production of highly concentrated formic acid from captured CO₂ by combining electrodialysis with monopolar membranes and pervaporation technologies.