Characteristics of Dissolved Organic Matter from Feces-Based Biochar: Effects of Pyrolysis Temperature and Extraction Solution pH

Pyrolysis enables resource recovery from human feces, yet the mechanisms of release of dissolved organic matter (DOM) from the resulting biochar remain poorly understood. This study investigated how extraction solution pH influences DOM release from feces-derived biochar prepared at different pyrolysis temperatures (280-580 °C), using multispectral techniques, PARAFAC modeling, and two-dimensional correlation spectroscopy (2D-COS). Results showed that dissolved organic carbon (DOC) concentrations ranged from 6.77 to 36.52 mg·g^-1, with higher DOM release under alkaline conditions. PARAFAC identified three humic-like components and one protein-like component. Protein-like substances were preferentially released under acidic conditions, while humic-like components dominated under weakly acidic to alkaline environments. 2D-COS analysis further revealed a sequential release of DOM components at the molecular level, influenced by the pyrolysis temperature through modifications in DOM functional groups. These findings provide a theoretical basis and practical insight for employing feces-derived biochars in environmental remediation.