Engineered Nanoparticle Interfaces Optimize Phase Change Behavior through Enhanced Mass- and Heat-Transfer for High-Efficiency Industrial CO ₂ Capture

Industrial carbon dioxide (CO₂) phase change absorbents often face challenges in initiating phase transition and exhibit slow phase separation and sluggish reaction kinetics, particularly under variable operating conditions. To overcome these limitations, this study develops a novel ionic liquid-based nanofluid absorbent engineered for enhanced performance and operational stability. The system integrates the functionalized ionic liquid [tetraethylenepentamine][1,2,4-triazole], which offers high CO₂ loading and reliable phase transition behavior along with titanium dioxide nanoparticles and an optimized solvent mixture of 1-methoxy-2-propanol and water. The nanofluid design dramatically reduces the phase separation time by 53.85% and increases the regeneration efficiency from 79.59% to 91.72%. The key to this enhancement lies in the nanoparticles, which suppress droplet coalescence and stabilize the phase interface through surface activation, Brownian motion, and microconvection effects while decreasing mass-transfer resistance in the liquid by 38.0% and enhancing both thermal conductivity and thermal diffusivity. Moreover, the nanofluid demonstrates exceptional stability over 60 consecutive cycles, exhibiting less than 20% total performance degradation throughout the entire testing period. A successful 168 h continuous 4 Nm³·h⁻¹ bench-scale operation confirms its more desirable CO₂ capture capability and phase change behavior, achieving a record-low regeneration energy consumption of 1.81 GJ·t CO₂⁻¹. Life-cycle assessment also confirms its superior environmental sustainability versus monoethanolamine technology.