COMPREHENSIVE EVALUATION OF HEAT-STABLE SALT REMOVAL FROM MDEA/DEA AMINE SOLUTIONS USING ICP-OES AND NANO-LC-MS/MS

Heat-stable salt (HSS) accumulation is a critical factor limiting the efficiency and lifetime of amine-based gas treatment systems. In aqueous monoethanolamine (DEA) and methyldiethanolamine (MDEA) solutions, HSS are formed through irreversible interactions between inorganic cations and organic degradation products, leading to reduced absorption capacity, increased corrosion, and higher regeneration costs. Reliable evaluation of HSS removal therefore requires analytical methods capable of characterizing both inorganic and organic components. In this study, HSS removal from MDEA/DEA solutions was investigated using a combined analytical approach based on inductively coupled plasma optical emission spectrometry (ICP-OES) and nano-liquid chromatography tandem mass spectrometry (nano-LC-MS/MS). ICP-OES quantified inorganic cations and corrosion-related metals, while nano-LC-MS/MS provided molecular-level insight into organic degradation in reference, fresh, and operational amine samples. The ICP-OES results revealed pronounced enrichment of sodium, potassium, calcium, and magnesium in HSS-rich samples, with sodium and calcium concentrations reaching 17.6 g/kg and 31.0 g/kg, respectively. Corrosion-related metals including iron, copper, chromium, and zinc also increased significantly, with iron rising from approximately 50 mg/kg in less degraded samples to over 430 mg/kg in concentrated fractions. Nano-LC-MS/MS analysis showed low spectral complexity in reference and fresh MDEA, whereas operational samples exhibited increased signal density and intensity across a broad m/z range, indicating advanced organic degradation. The combined results demonstrate a strong correlation between inorganic salt accumulation and organic degradation pathways in HSS formation. The applied purification process effectively reduced both inorganic and organic HSS components, restoring the chemical integrity of the amine solvent. This integrated analytical strategy provides a robust basis for assessing HSS removal efficiency and improving solvent management in industrial gas treatment systems.

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