Mg and Fe co-loaded biochar prepared by microwave-synergized K₂FeO₄ of marine biomass for efficient CO₂ capture: Performance assessment and mechanism exploration

To overcome the limitations of complex preparation and suboptimal performance of CO₂ adsorbents, the present work synthesized a polymetallic oxide-loaded biochar (MgO·FeO_x@biochar) with good performance in one step using a green and simple method of microwave-synergized K₂FeO₄. MgO·FeO_x@biochar-700–10-0.1 with a hierarchical porous structure, abundant adsorption sites and well-distributed basic sites was obtained by optimizing the preparation parameters, which had a good CO₂ trapping performance of 4.92 mol/kg with a retention rate of 83.01 % over 20 cycles, and exhibited good selectivity for O₂ and N₂. CO₂ capture by MgO·FeO_x@biochar was predominantly driven by chemical interaction between surface adsorption sites and CO₂, supplemented by microporous filling. The adsorption kinetics revealed that the CO₂ adsorption rate of MgO·FeO_x@biochar was influenced by the combined effect of membrane diffusion resistance and intraparticle diffusion resistance. This study established a theoretical basis and technical insight for the environmentally friendly and efficient preparation of high-performance biochar-based CO₂ adsorbents.