Valorization of Coal-Fired Slag for Sustainable Synthesis of Anti-Sintering CaO Composites With Enhanced Cyclic CO2 Capture Performance

Among high-temperature adsorbents, CaO is considered a promising material due to its high CO 2 absorption capacity and cost efficiency. This work reports the synthesis of CaO composite adsorbent using coal-fired slag (CFS) as an anti-sintering agent to enhance the cyclic stability of CO 2 capture. The precursor was prepared by a simple stirring protocol that incorporated a CO 2 -storage material (CO 2 SM) previously obtained by reacting CO 2 with a tetraethylene glycol (T4EG) and 1,2-propanediamine (PDA) mixture. Systematic optimization identified the optimal synthesis conditions as 10 wt% CFS, particle sizes of 500–800 mesh, synthesis temperature of 30°C, and reaction time of 2 h. The CaO/CFS precursor was obtained through stirring-induced precipitation and subsequently calcined at 900°C. The presence of CFS effectively inhibited CaO particle sintering and significantly improved cyclic stability. The optimized CaO/CFS composite absorbent exhibited an initial CO 2 adsorption capacity of 485.91 mg/g, maintaining 68.36% of the initial capacity after 20 cycles. In contrast, pure CaO typically maintains only 42.48% under identical conditions (99.99 vol% CO 2 , 650°C adsorption, 900°C regeneration). This work presents a viable and sustainable method for CO 2 capture utilizing low-cost waste materials, offering practical insights for the development of advanced CO 2 capture technologies. Graphical A CaO/CFS composite adsorbent was synthesized using coal-fired slag as an anti-sintering scaffold to enhance high-temperature CO 2 capture. The optimized material achieved a CO 2 uptake of 485.91 mg/g and maintained 68.36% capacity after 20 cycles, higher than pure CaO owing to suppressed sintering and preserved pore structure accessibility.