Advancing CO2 separation and capture in post-combustion scenarios using resonant vibration techniques

Carbon dioxide (CO₂) requires specialized capture methods for effective mitigation. Biochar has garnered significant interest as a versatile, porous solid adsorbent due to its cost-effective production, thermal, chemical, and mechanical stability, and minimal environmental impact. However, its small surface area and diffusional issues result in slow CO₂ adsorption kinetics and limited capacity, hindering widespread adoption. To address this limitation, most research in the field focuses on chemical approaches to enhance biochar's adsorption capabilities. While these methods are effective, concerns remain about their overall carbon neutrality and environmental sustainability due to the production of toxic chemicals. In this work, an innovative Process Intensification technique—Low-Frequency High-Amplitude (LFHA) resonant vibratory mixing—is proposed to enhance selective CO₂ adsorption onto hemp-derived biochar under simulated post-combustion conditions (16 % V/V CO₂/N₂) representative of coal-fired power plant exhaust streams. By optimizing biochar's physical properties and facilitating CO₂ transport processes, the resonant vibrations are shown to increase the CO₂ selectivity factor by 25.49 %, from 9.61 in non-vibrational adsorption to 12.07 in vibrational adsorption. The calculated CO₂ working dynamic capacity from selective adsorption closely corresponded to the equilibrium capacity obtained through isothermal measurements at room temperature (25 °C) and a partial pressure of 0.16. The values were 9.12 % lower for non-vibrational adsorption and 20.64 % lower for vibrational adsorption, thereby demonstrating the efficiency of the developed method. The microstructure and the textural properties of biochar have been evaluated by means of Scanning Electron Microscopy (SEM), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and Raman spectroscopy. Experimental results also indicate the reusability and regeneration of biochar for cyclic CO₂ adsorption through two distinct methods.