Advanced CO ₂ Capture by Novel Aqueous AEP/DMEA Blend: Thermodynamic Modeling, Absorption-Regeneration Energy, Kinetics, Toxicity and Spectroscopic Insights

The urgent demand for energy-efficient solvents in postcombustion CO2 capture motivates the search for novel amine blends that combine high absorption capacity with reduced regeneration energy. In this study, we explore the CO2 solubility and absorption–desorption behavior of an aqueous blend of 1-(2-aminoethyl)piperazine (AEP) and N,N-dimethylethanolamine (DMEA). AEP was selected for its multiple amine functionalities, offering fast kinetics as well as high CO2 uptake potential, while DMEA was introduced as a promoter for high CO2 solubility and to mitigate energy requirements during solvent regeneration. Experiments were conducted in a bubble column reactor over temperatures of 293.15–318.15 K, AEP mole fractions of 0.05–0.25, CO2 partial pressures of 7.09–20.27 kPa, and solution concentrations of 1–3 mol/L. The DMEA-AEP system exhibited remarkable performance, achieving a maximum loading of 1.0829 mol CO2/mol amine and a significantly lower average heat of absorption (−59.21 kJ/mol) compared with monoethanolamine (−85.13 kJ/mol). To correlate the experimental solubility data, both an empirical model and a modified Kent–Eisenberg model were developed, with average absolute deviations below 1%, underscoring their predictive reliability. At 3 mol/L, the blend demonstrated 133.33% higher cyclic loading and 36.95% higher cyclic capacity than monoethanolamine (MEA), while reducing heat duty to 2.74 GJ/ton CO2 and improving regeneration efficiency to 79.8%. Spectroscopic characterization (13C NMR and FTIR) confirmed the formation of key chemical species. Overall, this work introduces a new solvent system that not only outperforms MEA in absorption efficiency and energy demand but also establishes a framework for combining experimental evidence with robust modeling. These findings demonstrate the novelty and promise of the DMEA-AEP blend as a next-generation solvent for sustainable CO2 capture.