Iron Solubility Measurements in Aqueous MEA for CO₂ Capture

Solvent degradation is one of the major challenges for amine-based carbon capture development. Oxidative degradation appears to be influenced by the combined presence of oxygen and dissolved metals, particularly iron. The maximum amount of dissolved iron corresponds to its solubility in amine solvents. However, the current literature is very limited in providing such data. This work aims to provide a comprehensive method, developed through an investigative process, capable of providing valuable and reliable data on iron solubility in amine solvents. This method is based on precipitation, where an excess concentration of iron salt must precipitate to reach the solubility limit, coupled with analytical methods such as microwave plasma atomic emission spectroscopy and ICP-MS. This work highlights the main limitation of any work on this topic, i.e., the difficulty to determine the oxidation state composition of iron at any time in the solvent. Despite these limitations, the results seem consistent, providing insight into the solubility of iron(II) and iron(III) ions using deduction and highlighting the influence of temperature, CO₂ loading, and amine concentration. In addition, experiments were conducted using degraded solvent to investigate what to expect in a CO₂ capture plant. These results open the door for further experiments to improve the general understanding of the catalytic potential of iron and other metals on amine oxidative degradation.