Optimizing CO2 capture: Effects of chemical functionalization on woodchip biochar adsorption performance
Antonio Faggiano, Angela Cicatelli, Francesco Guarino, Stefano Castiglione, Antonio Proto, Antonino Fiorentino, Oriana Motta
Abstract
As atmospheric CO 2 concentrations rise, primarily due to fossil fuel combustion and deforestation, the urgent need for effective carbon capture solutions becomes increasingly critical to mitigate global warming. This study investigates the enhancement of CO 2 adsorption in woodchip biochar (WBC) through targeted chemical functionalization with potassium hydroxide (KOH), sodium hydroxide (NaOH), and ferrous sulfate (FeSO 4 ). Using Central Composite Design (CCD) and Response Surface Methodology (RSM), it is systematically possible to identify optimal functionalization conditions to maximize the biochar's adsorption efficiency. The KOH-treated biochar exhibited the highest adsorption capacity (Qmax of 9.89 mmol/g), substantially improving over untreated biochar (Qmax of 4.54 mmol/g). Adsorption analysis through Langmuir and Freundlich isotherm models highlighted a strong alignment with the Langmuir model, suggesting a predominantly monolayer adsorption surface. Additionally, kinetic studies using pseudo-first-order (PFO) and pseudo-second-order (PSO) models indicated a favourable chemisorption process, with the PSO model showing a superior fit. These results demonstrate the potential of chemically functionalized biochar, especially when treated with KOH, as a viable material for CO 2 capture, presenting an environmentally sustainable pathway for addressing the pressing issue of atmospheric CO 2 . Utilizing biochar derived from organic waste also promotes waste valorisation and supports a circular economy. Optimised biochar could mitigate CO 2 emissions, potentially serving as a complementary solution in climate change mitigation strategies, especially in scenarios where biochar can be deployed at scale in industrial or agricultural settings. • KOH-treated biochar absorbs up to 5.29 mmol of CO 2 per gram. • Chemical treatment is crucial for enhancing biochar's performance. • Biochar treated with NaOH and FeSO 4 is effective but not as much as KOH. • The RSM method identifies the best conditions for CO 2 capture with biochar. • Chemisorption is proven to be the main capture mechanism through the PSO model fit.