Physicochemical and sorption properties of thermally-treated sediments with high organic matter content.

Sediment samples with high organic carbon contents (22.04% and 8.46%) were collected and thermally-treated using a method analogous to biochar production. The obtained thermally-treated sediments (TTSs) showed a much higher degree of carbon capture in comparison to biochar derived from common biomass, indicating potential use of TTSs in soil amendment and carbon sequestration. Their sorption with organic contaminants was also investigated using sulfamethoxazole (SMX) as a model sorbate. SMX sorption increased greatly with pyrolytic temperature. Desorption ratio of the adsorbed SMX in TTSs generally decreased with increased pyrolytic temperature and with decreased solid-phase concentrations. The thermodynamic analysis showed that the higher entropy increase (positive ΔS) was well related with the decreased desorption ratio with increased solid-phase concentration for the original sediments. The fate-controlling effect of contaminants in TTS application for soil amendment should be evaluated combining sorption/desorption and sorption thermodynamic studies.