Fabrication of a cost-effective metal oxide-based adsorbent from industrial waste slag for efficient CO2 separation under flue gas conditions

Efficient and affordable adsorbents for CO2 capture are essential in implementing carbon capture technology to mitigate the negative impact of greenhouse gas emissions. This study focuses on synthesizing new nanoporous adsorbents from industrial waste slag using a simple and cost-effective coprecipitation method. In this method, raw slag was milled for 48 h and used as a benchmark for comparing two newly synthesized adsorbents. Selectivity and pure gas isotherm experiments were conducted for all adsorbents in the 25-65 degrees C temperature range and under harsh industrial conditions of 65 degrees C and 15 % CO2. This study utilized the response surface methodology (RSM) to optimize the CO2 adsorption parameters. Specifically, the optimized adsorption conditions were determined for the 15/85 % CO2/N-2 condition, and the optimal values for pressure and temperature were found to be 5 bar and 45 degrees C, resulting in CO2/N-2 selectivity of 5.65. The NH3-slag adsorbent was identified as the superior choice based on its selectivity and maximum adsorption capacity. The maximum adsorption capacity and cyclic efficiency were determined to be 4.15 mmol/g and 98.1 %, respectively, at a temperature, pressure, and composition of 45 degrees C, 5 bar, and 15 % CO2. Isotherm and thermodynamic models were employed to further investigate the adsorption process. The isotherm results indicated that the adsorption of CO2 by adsorbents occurred heterogeneously in patch-wise sites. Meanwhile, the thermodynamic parameters showed that the process was exothermic and spontaneous, with Delta H degrees falling below 20 (kJ/mol), showing physisorption phenomena.