Enhancing fuel characteristics and combustion performance of cellulose-rich straws through CO2-assisted torrefaction.

Cellulose-rich straws of corn and rice were torrefied under carbon dioxide, and the fuel characteristics and combustion performance of the obtained biochar were investigated. A high severity resulted in surface collapse, greater pore volume, elimination of oxygen, elevated calorific value, and improved hydrophobicity in biochar. Following carbon dioxide torrefaction, the cellulose content in solid biochar experienced a slight decrease when the temperature was raised to 220 °C for longer residence durations. At 300 °C, the cellulose content in the biochar was nearly eliminated, while the relative proportion of non-sugar organic matter in corn stover and rice straw increased to 87.40 % and 77.27 %, respectively. The maximum calorific values for biochar from corn and rice straws were 22.38 ± 0.03 MJ/kg and 18.72 ± 0.05 MJ/kg. The comprehensive combustion indexes of rice and corn straw samples decreased to 1.06 × 10-7 and 1.31 × 10-7 after torrefaction at 300 °C, respectively. In addition, the initial decomposition temperatures increased by 38 °C and 45 °C, while the ultimate combustion temperatures rose by 13 °C and 16 °C for corn and rice straws, respectively. These results imply an extended combustion timeframe for the torrefied samples.

Synthesis of lignin nanoparticle­manganese dioxide complex and its adsorption of methyl orange.

Lignin nanoparticles (LNPs) were synthesized using an anti-solvent method and subsequently loaded with manganese dioxide (MnO2) via potassium permanganate treatment, resulting in the formation of MnO2@LNPs. An extensive investigation was conducted to elucidate the influence of MnO2@LNPs on the decolorization of methyl orange solution. The LNPs were successfully obtained by adjusting the preparation parameters, yielding particles exhibited average sizes ranging from 300 to 600 nm, and the synthesis process exhibited a high yield of up to 87.3% and excellent dispersion characteristics. Notably, LNPs size was reduced by decreasing initial concentration, increasing stirring rate, and adding water. In the acetone-water two-phase system, LNPs self-assembled into spherical particles driven by π-π interactions and hydrogen bond forces. Oxidation modification using potassium permanganate led to the formation of nanoscale MnO2, which effectively combined with LNPs. Remarkably, the resulting MnO2@LNPs demonstrated a two-fold increase in methyl orange adsorption capacity (227 mg/g) compared to unmodified LNPs. The process followed the Langmuir isotherm model and was exothermic.