Activated carbon from tea twig waste via KOH activation and carbonization by conventional furnace or ultrafast arc plasma for CO2 capture

Tea twig waste ( Camellia sinensis ), a lignocellulosic by-product of the tea industry, represents a promising renewable precursor for the production of high-performance activated carbon for CO 2 capture. In this study, activated carbon was prepared from tea twig biomass via chemical activation with potassium hydroxide (KOH), followed by two distinct heating methods: conventional furnace activation and rapid Arc Plasma activation. The plasma process, employing argon as the working gas and operated at 700°C with a current of 70 A for 10 minutes, selectively removed non-carbon species and promoted the development of microporosity together with oxygen- and nitrogen-containing surface functionalities. The sample activated using Arc Plasma under optimised conditions (AC 2 -B 8 C 10 ) exhibited a high specific surface area of 1236 m 2 g -1 and a micropore volume of 0.597 cm 3 g -1 , with ultramicropores well matched to the kinetic diameter of CO 2 . In contrast, samples activated by conventional heating (AC 1 -B 8 C 7 , 700°C for 2 h) displayed lower surface areas and more pronounced mesoporosity. CO 2 adsorption performance was evaluated using temperature-programmed desorption of CO 2 (TPD-CO 2 ), revealing an adsorption capacity of up to 6.6 mmol g -1 at 40°C and 1 bar for the plasma-activated sample, significantly outperforming its furnace-activated counterpart. Comprehensive characterisation by XRD, SEM, and FTIR confirmed an essentially amorphous carbon structure with abundant microporosity and polar surface functional groups favourable for CO 2 physisorption. These findings demonstrate that Arc Plasma activation enables ultrafast processing while enhancing pore development and CO 2 capture performance, and, based on a semi-quantitative laboratory-scale assessment, offers the potential for reduced specific energy input compared with conventional furnace activation.