Enhanced and Stable Carbon Capture through Hierarchical Sorbent and Process Optimization Using Biochar from Deoiled...

In this study, a novel functionalized biochar derived from deoiled cake biomass was developed using an integrated multiparameter optimization framework for effective carbon dioxide (CO₂) captured under a simulated flue gas mixture. Unlike conventional synthesis that focus on individual parameters, this work systematically integrates various process variables within a single framework to establish a clear structure-property-performance relationship. The results demonstrate the synthesis pathways and chemical activation conditions play a decisive role in tuning the key physicochemical properties of the adsorbent, which directly influence CO₂ capture efficiency. Statistical optimization was carried out using response surface methodology (RSM). Under optimized conditions of 30 °C, 200 mL/min, 3 g, and 180 min, a maximum CO₂ uptake of 4.9 mmol/g was achieved. Among the investigated variables, adsorbent amount and contact time were identified as the most influential factors, whereas temperature and flow rate showed comparatively weaker effects. Kinetic analysis confirms that the pseudo-second order (PSO) model provided the best fit with an R ² of 0.98 and a rate constant (k ₂) of 0.092 g mmol^-1 h^-1, indicating that the adsorption process involves a combination of physisorption and chemisorption with strong adsorbate-surface interactions. The adsorption isotherm data were well described by the Langmuir model with an R ² of 0.99, indicating monolayer adsorption behavior. The isosteric heat of adsorption, around 40.02 kJ/mol, further supports strong CO₂ adsorbent interactions. In addition, the adsorbent exhibited stable cyclic performance over 20 adsorption-desorption cycles with marginal capacity loss, demonstrating its potential for practical flue gas CO₂ capture applications.