Siberian Federal University

This paper examines the composition and structure of hydrochars obtained by hydrothermal carbonization (HTC) of aspen wood, as well as porous carbon materials formed during their thermochemical activation at 800 °C using KOH, Fe(NO3)3, and K3[Fe(CN)6]. It was established by chemical and elemental analysis, IR spectroscopy, X‑ray diffraction, and scanning electron microscopy methods that increasing the hydrothermal carbonization temperature from 180 °C to 240 °C leads to the destruction of wood hemicelluloses and cellulose. Hydrochars obtained at temperatures 230 °C and 240 °C consist of so-called “pseudolignin.” Carbon-containing microspheres are formed on the surface of the hydrochars, the number of which increases with HTC temperature. As the hydrochar production temperature increases, their thermal stability is becoming higher. Thermochemical activation of hydrochars at 800 °C using KOH, Fe(NO3)3, and K3[Fe(CN)6] significantly develops the porous structure of the carbon product. The specific surface area of the carbon samples increases in the following order of activators: Fe(NO3)3 (up to 310 m2/g) < K3[Fe(CN)6] (up to 586 m2/g) < KOH (up to 1381 m2/g). Metallic iron compounds and iron carbides Fe3C are uniformly distributed on the surface of the sample activated with Fe(NO3)3, while iron oxides and iron carbides Fe3C and FeC are present on the surface of the sample activated with K3[Fe(CN)6]. Pseudolignin microspheres forming on the surface of the hydrochars remain on the surface of the activated carbon materials as carbon microspheres. With sizes 1–8 μm ron-containing samples have magnetic hysteresis and the saturation magnetization value allows them to be isolated from a liquid medium using a magnet