Toward scalable and sustainable CO₂ capture: RSM-Guided optimization of Mg(OH)₂ slurry bubble column reactor

The increasing concentration of atmospheric carbon dioxide (CO₂), driven by industrial activities and fossil fuel consumption, necessitates the development of efficient and scalable carbon capture technologies. In this study, the chemical absorption of CO₂ using a magnesium hydroxide [Mg(OH)₂] slurry was investigated in a semi-batch slurry bubble column reactor. The process was optimized using a Box-Behnken Design (BBD) within the Response Surface Methodology (RSM) framework, evaluating the effects of four key parameters: slurry initial concentration (0.001-0.003 mol/L), liquid volume (15-25 L), increase in liquid height within the column due to gas retention (1-4 cm), and temperature (30-50 °C). A total of 23 experimental runs were conducted, and CO₂ removal efficiency was selected as the response variable. The regression model developed showed excellent agreement with experimental data (R² = 0.9923), and the maximum CO₂ removal efficiency achieved was 82.10% under optimal conditions (25 L liquid volume, 0.001 mol/L Mg(OH)₂ initial concentration, 40 °C, 1 cm increasing the height of the liquid inside the column). The findings emphasize the critical roles of gas-liquid interfacial area, slurry alkalinity, and operating temperature in enhancing CO₂ absorption. This work contributes to the advancement of sustainable CO₂ capture technologies and provides a robust foundation for future industrial-scale implementations of Mg(OH)₂-based absorption systems.