Preparation of activated biochar with adjustable pore structure by hydrothermal carbonization for efficient adsorption of VOCs and its practical application prospects

Porous-activated biochars with abundant pores have great potential for the treatment of volatile organic compounds (VOCs). However, the lack of cost-effective pore-modulation methods for these materials has hindered their feasibility for large-scale use as adsorbents. In this study, hydrothermal carbonization (HTC) of glucose, the basic unit of cellulose, was investigated, and the pore structure of the obtained hydrochar was precisely determined by controlling the main factors of the hydrothermal process. Orthogonal experiments were conducted to determine the most suitable conditions for a hierarchical porous structure, and the water ratio was considered the main regulating factor. The range of possible carbon precursors was extended to all biomasses by proposing an innovative model to explain the formation of pore structures during the conversion of basic biomass components to biochar in the HTC process. The results revealed that the water ratio significantly affected the decomposition and carbonization of biomass in HTC, which further affected the microdomain unit size and, thus, the biochar pore structure. Further, the graded porous structure substantially enhanced the biochar adsorption capacity. HTC was found to have a greater potential for practical applications, as it presented a substantially higher yield, compared to direct carbonization processes. Overall, this work provides guidance and an effective reference for the pore size adjustment of porous-activated biochar developed for the adsorption of pollutants.