Elemental Characterization and Removal of Heat-Stable Salt Precursors from Aqueous MDEA Solutions Used in Acid Gas Treatment

Aqueous methyldiethanolamine (MDEA) solutions are extensively used in industrial acid gas sweetening processes for selective removal of H₂S and CO₂. However, long-term operation leads to the accumulation of inorganic impurities, corrosion products, and heat-stable salt (HSS) precursors, which negatively affect solvent performance, increase foaming tendency, and accelerate equipment corrosion. In this study, a comprehensive elemental characterization of fresh, contaminated, and regenerated MDEA samples was carried out using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). Macro- and micro-elements including Na, K, Ca, Mg, Fe, Al, Zn, Pb, Ni, Cr, and trace toxic elements were quantitatively determined. The results revealed significant accumulation of alkali and alkaline-earth metals in contaminated samples, indicating progressive salt formation and solvent degradation during industrial circulation. Elevated concentrations of iron and aluminum confirmed corrosion-related contamination. After applying the purification procedure, substantial reductions in Ca²⁺, Mg²⁺, Fe³⁺, and other metal ions were observed, demonstrating effective removal of HSS-associated inorganic species. Analytical precision was confirmed by low relative standard deviation (RSD < 5%) for major elements. The combined ICP-MS and ICP-OES approach proved to be a reliable tool for monitoring solvent health and evaluating regeneration efficiency. The findings provide important insights for optimizing amine solvent management strategies and improving operational stability in industrial gas treatment units.