Revealing carbon-iron interaction characteristics in sludge-derived hydrochars under different hydrothermal conditions

Hydrothermal conversion is seen as a potential sustainable solution for the disposal and utilization of sewage sludge. One-step hydrothermal carbonization was used to prepare iron-based sludge hydrochars, and the microstructure properties of hydrochars under different hydrothermal conditions were investigated, with emphasis on the inherent interaction mechanisms between carbon and iron. The aromaticity of hydrochars increased with increasing hydrothermal temperature and time, whereas the specific surface area and pore volume as well as magnetic characteristics of hydrochars were only contingent on temperature. Once the temperature reached 160 degrees C, Fe3O4 in sludge was completely transformed into Fe3O4 in hydrochars. Simulated experiments suggest that glucose is more advantageous than protein in the iron transformation and mesopore formation. The coexistence of glucose, protein, and FeCl3 improved the aromaticity as well as specific surface area and pore volume of hydrochars. This study provides a basis for designing high performance iron-based sludge hydrochars.

Automated summary

Hydrothermal conversion is a potential sustainable solution for sewage sludge disposal and utilization. This study used one-step hydrothermal carbonization to prepare iron-based sludge hydrochars and investigated the properties of hydrochars under different hydrothermal conditions. The results showed that the properties of hydrochars are influenced by temperature, and glucose has a more advantageous effect on iron transformation and pore structure formation.