Synthesis of sawdust-based porous carbon using Box–Behnken design for NO₂ adsorption: modeling, optimization, and study of interaction effects

In this research, an inexpensive porous carbon was synthesized by chemical activation of a thermally carbonized sawdust using KOH as an activation agent. The effect of three major process parameters—temperature, time, and KOH concentration—on the uptake of NO₂ and porous carbon yield were optimized using the Box–Behnken factorial design. The optimum operating conditions suggested were at a temperature = 746.18 °C, time = 73.08 min, and KOH concentration = 6.45 mol L⁻¹. The activated carbon synthesized at optimal conditions had a maximum BET surface area of 1460.64 m² g⁻¹ with NO₂ uptake capacity and yield of 449.64 mg g⁻¹ and 41.25%, respectively. Furthermore, the optimized activated carbon was analyzed using various analytical methods and the reusability of the spent activated carbon was investigated in several cycles. The study confirmed that the porous sawdust activated carbon is a promising adsorbent for the effective removal of NO₂ with a competitive yield.