CO₂ activation promotes available carbonate and phosphorus of antibiotic mycelial fermentation residue-derived biochar support for increased lead immobilization

Recycling of antibiotic mycelial fermentation residue (AR), a hazardous waste material, into high-performance heavy metal remediation material is an emerging research hotspot. The inorganic composition of biomaterials represents their capacity to immobilize heavy metals. In this study, to improve the Pb immobilization capacity, lincomycin mycelial fermentation residue (LR, a type of AR) was pyrolyzed in CO₂ or N₂ gas under different temperatures to adjust the carbon and phosphorus composition of its biochar. Results indicate that both activation temperature and gas type can significantly influence the transformation of LR carbon and phosphorus-containing groups. At high temperatures, the activation gas significantly controlled changes in carbonate and available phosphorus; however, this process was less successful at low temperatures. CO₂ gas clearly inhibited the degradation of carbonate, but promoted consumption of the carbon matrix and released organism-combined phosphorus. Results suggest that CO₂-activated biochar at 700 °C exhibited the strongest Pb immobilization capacity of 454 mg/g in aqueous solution and the highest Pb immobilization rate of 60% in soil, due to its more sites (carbonate and available phosphorus) for Pb stabilization. This study provides an effective method for transforming waste AR into a high-performance material for metal stabilization.