Synergistic and sustainable chitosan-based biochar biocomposite for high-performance extraction of carbamazepine and its metabolites from environmental waters.

A novel chitosan-biochar biocomposite was engineered as a synergistic and sustainable sorbent phase for the extraction of carbamazepine and its metabolites from environmental waters. The material was prepared using citric acid as a green crosslinker and glycerol as a plasticizer. Its formulation was optimized through experimental design. Compared with crosslinked chitosan and biochar, the biocomposite exhibited superior extraction performance. Mathematical modeling, together with complementary characterization analyses, corroborated this enhancement, which revealed a synergistic hybrid effect involving multi-site interactions beyond surface area contributions. Sustainability was demonstrated by the use of renewable precursors, along with a comprehensive assessment of biodegradability, biocompatibility, and toxicity of the constituents, reusability over multiple extraction-desorption cycles, and the application of analytical greenness metrics. Applied in rotating-disk sorptive extraction, the optimized methodology achieved high recoveries (86-96 %), with low relative standard deviations (<16 %), and sub-μg L-1 limits of detection, performing comparably to commercial sorbent phases and outperforming others. The method enabled the determination of the analytes in river water, confirming the potential of this material as a cost-effective, sustainable, and high-performance material for environmental monitoring.