Efficient dichloromethane and toluene removal via lignin derived oxygen and nitrogen-containing activated carbons with well-developed micro-mesopore structure

Abstract

Industrial lignin is a promising carbon precursor because it is abundant and renewable, with high carbon content. However, a large amount of lignin is used as low-value burning fuel, and even considered as environmental pollutant in some circumstances. In this work, a family of the porous activated carbon (PAC) are synthesized utilizing alkali lignin as the precursor by carbonization-activation methods. The obtained PAC display high specific surface area (2923 m2·g−1), large pore volume (1.51 cm3·g−1), and interconnected micro-mesopore structure as well as rich surface heteroatom content (7.53–10.22 at.% oxygen, 1.17–2.29 at.% nitrogen, and 0.84–0.96 at.% sulfur). When used as adsorbent for volatile organic compound (VOC) removal, the PAC show outstanding adsorption capacity of dichloromethane (171 mg·g−1) and toluene (518 mg·g−1). The porous characteristics of PAC improved along with the fluctuation of the proportions of carbonization temperature, activation temperature, and lignin/KOH mass ratio. In addition, the correlation between adsorption properties and pore structure suggests that the dichloromethane and toluene adsorption capacity are determined by nanopores (0.5–1.0 nm) and micropores (<2 nm) respectively. The Yoon and Nelson (YN) model of adsorption breakthrough curve reveals that PAC have the high adsorption rate k and fast mass transfer rate. The positive linear relationship (R2 > 0.80) between the k and mesopore confirms that mesopores play the role of mass transfer channel.