Comparison of Physicochemical Properties of Camellia Oleifera Shell Biochar Prepared under Different Carbonization Conditions

Objective A comparative analysis of the physicochemical properties of camellia oleifera shell biochar prepared under different carbonization conditions was carried out to provide a reference basis for the production and application of biochar.

Method Nine types of biochar were made from camellia oleifera shell at different carbonization temperatures (T: 400℃, 500℃ and 600℃), constant temperatures (t: 2 h, 4 h and 6 h) and heating rate (v: 150℃ h⁻¹) to study their heat loss characteristics, morphological structure, surface functional group species and organic component content, drawing on material science methods.

Result With the increase of carbonization temperature, the cellulose, hemicellulose and lignin components were decomposed successively, and the thermal weight loss stabilization stage was entered after 600℃. 400℃ → 600℃ during the warming up charring process, the nitrogen adsorption-desorption isotherm of camellia oleifera shell biochar was changed from type IV to type III. The mesopores were abundant at 400℃, and the total pore volume was 0.00309-0.00351 cm g⁻¹. The macropores were abundant at 500℃ and 600℃, and the average total pore volumes were 0.00352 cm g⁻¹ and 0.00390 cm g⁻¹. The -CH₂, C=C, C=O, O-H and Si-O-Si stretching vibrational peaks were gradually narrowed. Meanwhile, the gradual decomposition or reorganisation of C=O, -OH and C-O-C groups leads to the reduction of H and O elements and the enrichment of C elements in the camellia oleifera shell biochar, and the H/C, O/C and (N + O)/C were also significantly reduced.

Conclusion The charring process of camellia oleifera shell is a C-rich devolatilisation process with enhanced aromaticity and reduced hydrophilicity and polarity. The charring temperature is the main factor affecting the C, H, O and N elemental contents, microscopic characteristics and nitrogen adsorption-desorption isotherm configuration of camellia oleifera shell biochar, while the constant temperature time is the main factor affecting the pore size distribution of oil tea fruit shell biochar. Among them, the micro-, meso- and macropore structures of the T₄₀₀t₆ V₁₅₀ treatment are abundantly distributed in the system, the mesoporous structure is the most abundant and the pore size distribution is narrow.