Synthesis and detailed characterization of hydrochars and biochars from chitosan

In this research study, the low-cost hydrothermally carbonized biomass (hydrochars) possessing microporous structures and tunable surface chemistry were synthesized from chitosan under various conditions, as well the investigation of the effects of carbonization times and temperatures on the structural, morphological, compositional, and textural characteristics of the resulting hydrochars. The synthesis temperature significantly influenced the crystallinity and the degree of amorphous carbon. Direct pyrolysis of chitosan resulted in the formation of a graphitic-type structure, with the intensities of the 002 and 100 peaks increasing as the temperature rose from 500 to 800 °C. Elemental analysis revealed that carbon content increased with both time and temperature of carbonization, while nitrogen content remained relatively constant at 5–6%, regardless of the synthesis parameters. Post-carbonization, the surface of the carbonaceous materials exhibited various oxygen-containing functional groups such as hydroxyls, amines, and amides. The surface areas and pore volumes of the hydrochars decreased with increasing pyrolysis temperatures. Among the hydrochars produced, those synthesized at the lowest temperature (160 °C for 24 h) demonstrated the best textural properties and defective structure formation, presenting a potentially low-cost and environmentally benign option.