Novel distillation method for rapidly removing organic compounds from biochar while enhancing its electron exchange capacity

Biochar, known as “black gold”, has garnered wide attention in various applications. However, the potential release of toxic organic compounds has raised environmental concerns, thereby limiting its safe and sustainable application. Herein, we propose a distillation strategy to simultaneously detoxify biochar and enhance its redox functionality. Multi-factor correlation analysis identified 30 min as the optimal distillation time, which significantly increased the biochar’s Brunauer-Emmett-Teller (BET) surface area (by 143%), improved hydrophilicity (with contact angle decreased by 3.8%), and effectively reduced the dissolved organic carbon (DOC) content of the biochar. Regarding the effect of distillation solvent, both water and acetic acid significantly enhanced the electron exchange capacity (EEC) of the biochar, with lactic acid exhibiting the best performance in improving the electron donating capacity (EDC). Meanwhile, distillation with acetic acid achieved optimal detoxification by effectively removing toxic organic compounds such as naphthalene, amines, and aromatic hydrocarbons. Further validation confirmed the good generalizability of this method to biochars derived from various feedstocks. Techno-economic analysis showed a 98.7% reduction in water consumption and 22.9%‒62.5% cost savings compared to traditional washing methods. This work highlights distillation as an efficient, eco-friendly, and cost-effective method to enhance biochar safety and redox functionality, thereby advancing its sustainable applications.