Study on design strategies and on new structure-performance relationships for CO₂ capture in gas-liquid hollow fiber membrane contactors

The urgent need for carbon dioxide (CO₂) capture technologies motivates this chemical engineering study, which systematically investigates the influence of macroscopic and microscopic structure on the CO₂ absorption performance of hydrophobic alumina (Al₂O₃) hollow fiber membrane (A-HFMs) contactors. Six different A-HFMs prepared using the non-solvent-induced phase separation (NIPS) method with select solvents followed by sintering at 1300°C were then tested for chemical CO₂ absorption in an A-HFM contactor using a monoethanolamine (MEA) solution. The hydrophobicity of the coatings applied on the A-HFM surfaces was confirmed by the water contact angle and thermogravimetric (TGA) analysis. Pearson's statistical analysis of a correlation matrix revealed the strength of relationships between nine variables, including outer diameter (mm), inner diameter (mm), percentage of sponge layer (%), pore size (nm), maximum pore size (nm), mechanical strength (MPa), surface porosity (m⁻¹), overall porosity (%), and CO₂ absorption flux (mol m⁻² s⁻¹). Building upon these findings, this study unveils a novel non-linear function linking three specific microscopic characteristics— pore size, surface porosity, and a geometric sponge layer factor—to CO₂ absorption flux, offering valuable insights for optimizing hydrophobic A-HFM design and enhancing CO₂ capture efficiency. The A-HFM, characterized by the combination of three factors (higher pore size, increased surface porosity, and a thicker sponge layer), achieved a CO₂ absorption flux of 6.36 ×10⁻³ mol m⁻² s⁻¹ at room temperature, showcasing its exceptional performance in capturing CO₂. The resulting empirical morphological factor provides a novel approach for enhancing the performance of CO₂ absorption through A-HFM design optimization.