High-performance magnetic activated carbon from solid waste from lignin conversion processes. Part I: Their use as adsorbents for CO2

Lignin is a naturally abundant and renewable precursor with a potential use in the production of both chemicals and materials. As many lignin conversion processes suffer from a significant production of solid waste (hydrochar), this study focused on transforming the hydrochars into magnetic activated carbons (MAC). The hydrochar was produced via hydrothermal treatment of lignin in the presence of formic acid as is being described elsewhere. The hydrochar was chemically activated with KOH. A focus was held on the optimization of the MACs as adsorbents for CO2. MACs are potentially relevant to carbon capture and storage (CCS) and gas purification processes. In general, the MACs exhibited high specific surface areas (up to 2875 m(2)/g) with high specific pore volumes and CO2 adsorption capacities of up to 6.0 mmol/g (1 atm, 0 degrees C). The textual properties of the MACs depended on the activation temperature. MACs activated at 700 degrees C had very high ultramicropore volumes, which are important for potential adsorption-driven separation of CO2 from N-2. Activation at 800 degrees C led to larger pores and very high specific surface areas. This optimization option, combined with the magnetic properties, provided numerous potential applications of the MACs besides of CCS. The hydrochar derived from eucalyptus lignin, and the corresponding MACs displayed soft magnetic behavior with coercivities of < 100 Oe and saturation magnetization values of 1-10 emu/g.