Preparation of hybrid porous carbon using black liquor lignin impregnated with steelmaking slag and its performance in SO₂ removal

A hybrid porous adsorbent was produced by mixing black liquor lignin (BL) with basic oxygen furnace steelmaking slag (SS) followed by carbonization at 860°C for removal of trace sulfur dioxide (SO₂) from air. The effects of BL percentage, carbonization temperature, carbonization duration and the binary combined effect of each individual process parameter on the removal of SO₂ have been statistically analyzed. The optimal preparation conditions were 48% = BL/(BL + SS), carbonized at 860°C for 50 minutes (labeled BL-SS-48-860-50). The crystallite CaO and MgO phases remained in the hybrid matrix. A carbonization temperature over 800°C facilitated gasification reaction between the carbon matrix and the CO₂ emitted from the decomposition of calcium and magnesium carbonate, which led to the pore formation and enlargement in the carbon matrix. The prepared hybrid adsorbent showed good SO₂ removal performance. The kinetic model demonstrated satisfying results in predicting SO₂ adsorption kinetics with good prediction within a relative large range of SO₂ inlet concentration. The mass transfer coefficient k = 537 (s⁻¹) was obtained by fitting the model to the experimental breakthrough curve.