The Valorisation of Biochar Produced from Black Liquor Pyrolysis for the Development of CO2 Adsorbents

The paper manufacturing process produces liquid and gaseous alternative fuels, as well as solid wastes. These can be subsequently treated through chemical processing, oxidation, and thermal activation, resulting in adsorbent materials with CO₂ adsorption capacities. The valorisation of black liquor waste resulting from paper manufacturing was achieved through a catalytic pyrolysis process using two catalysts previously prepared in house (Cu-Zn-MCM-41 and Ni-SBA-16). The HCl-treated adsorbent material, resulting from Ni-SBA-16-catalysed pyrolysis, was selected for use in CO₂ adsorption tests as it had the highest specific surface area (224.06 m²/g) and pore volume (0.28 cm³/g). The adsorption experimental setup was linked to a gas chromatograph in order to evaluate CO₂ adsorption efficiency using a binary gas mixture consisting of 81% CO₂ and 19% N₂. With a CO₂ adsorption capacity of 1.61 mmol/g, a separation efficiency of 99.78%, and a CO₂ recovery yield of 90.02%, it can be concluded that the developed adsorbent material resulting from Ni-SBA16-catalysed pyrolysis and HCl treatment represents a viable solution for black liquor pyrolytic solid waste removal and reduction in greenhouse gases.