Triple combination of natural microbial action, etching, and gas foaming to synthesize hierarchical porous carbon for efficient adsorption of VOCs.

Fungi residue, vinasse, and biogas residue differ from general biomass waste due to natural microbial action. Microbial fermentation helps create natural channels for the permeation of activators and produces proteins for natural nitrogen doping. Inspired by these advantages on porous carbon synthesis, this study adopted dual activators of KOH and KHCO 3 to synthesize porous carbon with different pore ratios for efficient adsorption of volatile organic compounds (VOCs). The fungi residue possessed the least lignin due to the most severe microbial action, contributing to the best pore structures after activation. The etching effect from potassium compounds and gas foaming from the carbonate decomposition contributed to creating hierarchical porous carbon with ultra-high surface area, ca. 1536.8–2326.5 m2/g. However, KHCO 3 addition also caused nitrogen erosion, such that lower adsorption capacity was attained even with a higher surface area when the mass ratio of KOH/KHCO 3 decreased from 2.5:0.5 to 2:1. The maximum adsorption capacities of chlorobenzene (CB) and benzene (PhH) reached 594.0 and 394.3 mg/g, respectively. Pore structure variations after adsorption were evaluated by freeze treatment to discover the adsorption mechanism. The surface area after CB and PhH adsorption decreased 40.3% and 34.5%, respectively. Most of the mesopores might transform into micropores due to the mono/multilayer stacking of adsorbates. The VOC adsorption kinetics were simulated by the Pseudo-first- and -second-order models and Y–N model. This paper provides a new approach for high-value biomass waste utilization after microbial action to synthesize efficient adsorbents for VOCs. • Biomass wastes after microbial action have loose structure and natural N sources. • Dual activators of KOH/KHCO3 produced the high porosity with hierarchical pores. • Mesopores act as transport channels and supplement for micropores after stacking. • The adsorption capacities of CB and PhH reached 594.0 and 394.3 mg/g, respectively. [ABSTRACT FROM AUTHOR]