Advancing activated carbon production: Utilizing pine pruning biochar via induction heating with CO₂and iron-based catalysts

This study introduces an induction heating approach for producing activated carbon from biochar obtained by thermal degradation of pine pruning waste from timber-related industries, using CO2 and iron-based catalysts as activation agents. Activation experiments were performed using a 10 kW high-frequency induction system (28-40 kHz) under continuous COQ flow (15 mL min- 1), with electric current intensities of 200, 300, 400, and 500 A (corresponding to 700-1100 degrees C) and durations of 30, 60, and 90 min, employing 45 g of iron-based catalysts (Fe-Ni-Ti-C, 85:6:3:6 wt%) per 3 g biochar (15:1 w/w). Mass loss increased from 13.7 % (200 A, 30 min) to 84 % (500 A, 90 min), inversely correlating with product yield, which ranged from 86.3 % to 16 %, respectively, highlighting the critical trade-off between porosity enhancement and material retention. Correspondingly, Brunauer-Emmett-Teller (BET) surface area was significantly enhanced, rising from 47.38 m2 g- 1 in the thermally processed biochar to 607.21 m2 g- 1 under milder activation conditions (200 A, 30 min), and further increasing to 865.07 m2 g- 1 at optimized conditions (500 A, 60 min) though with reduced yield (20.3 %). Fourier-transform infrared (FT-IR) spectroscopy confirmed the introduction of oxygen-containing functional groups, notably carbonyl and hydroxyl functionalities, while scanning electron microscopy (SEM) demonstrated substantial porosity development. X-ray diffraction (XRD) analysis further revealed crystallographic changes attributed to catalytic activity and carbon gasification reactions. These findings demonstrate that inductionassisted CO2 activation with iron-based catalysts offers a rapid (30-90 min vs. conventional 2-4 h), energyefficient, and scalable route for converting low-value pine pruning waste (biochar yield: 17 wt%) into highperformance activated carbon (BET up to 865 m2 g- 1), suitable for water treatment, gas adsorption, and energy storage applications, while reducing reliance on chemical activators and minimizing environmental impact.