Preparation of Biochar through Low-Temperature Carbonization of Hydroxyl-Rich Biopolymers Using N-Bromosuccinimide†

In this study, an alternate and simpler method of carbonizing hydroxyl-rich biopolymers at low temperatures (100–150 °C) is presented. This method involves the direct heating of a mixture of a biopolymer with N-bromosuccinimide in the absence of a solvent. This method is simpler compared to carbonization of biomass through pyrolysis, which necessitates high reaction temperatures, and hydrothermal carbonization that employs water as the solvent, resulting in lower output per reactor, increased energy requirements and costs, additional processing steps, and generation of waste streams. The carbonization likely occurred due to the in situ-generated hydrogen bromide, which acted as a dehydrating and reducing/deoxygenating agent. The resulting biochars exhibit strong potential for environmental remediation, with chitin-derived biochar achieving 98.13% removal of Rhodamine B from a 5 ppm aqueous solution within 1 h.