Journal of Environmental Chemical Engineering https://doi.org/10.1016/j.jece.2025.119913
Abstract
The substantial annual global production of Auricularia auricula waste medium (AWM) (≈70 million tonnes) poses significant environmental challenges. This study employed a custom-designed pyrolysis system operating under vacuum conditions (300–600 °C) to process AWM, systematically investigating the influence of temperature on the evolution mechanisms of pyrolytic products (char, liquid, gas). Multiple analytical techniques (EA, FT-IR, XRD, SEM, Raman, BET) revealed the raw material's semi-crystalline structure. Biochar produced at 450 °C (PC450) exhibited a well-developed mesoporous structure (specific surface area: 325.4 m2/g), significant graphitization (ID/IG=1.2), and good electrical conductivity (22.5 S/m), achieving maximum adsorption capacities of 384.2 mg/g for MB and 172.8 mg/g for Cu²⁺. Adsorption was spontaneous (ΔG < 0), involving both physical and chemical mechanisms, and showed good reproducibility (≥90 % efficiency after 5 cycles). PC450 also possessed a high calorific value (35.5 MJ/kg). Significant shifts in C/O and O/C ratios and enhanced C=O/C=C peak intensity confirmed increased sp² carbon content and a developed conjugated aromatic structure in SMS-BC450. GC-MS and Py-GC/MS analyses indicated that the vacuum environment suppressed deep cracking of macromolecules, enriching phenolic compounds (e.g., 4-ethylguaiacol) in the liquid and promoting combustible gases (CH₄, H₂), while concurrently inhibiting polycyclic aromatic hydrocarbons (e.g., benzofuran) and harmful substances, reducing ecotoxicity. Kinetic analysis (FWO, KAS models; R² > 0.98) established a two-stage competitive mechanism: initial macromolecule decomposition/polymerization followed by small-molecule condensation/cyclization. The low product ecotoxicity and operational feasibility of the vacuum system support industrial potential. This temperature-mediated strategy aligns with UN SDG 12 waste-recycling principles.
