Fe(NO₃)₃ assisted hydrothermal carbonization of sewage sludge: Focusing on characteristics of hydrochar and aqueous phase

Fe(NO₃)₃ was selected as a typical nitrate (5, 10 wt.%) to analyze its effects on the hydrothermal carbonization (HTC) of sewage sludge (SS). Enhancing hydrolysis was a key step to improving dehydration and decarboxylation of SS HTC. Fe(NO₃)₃ could notably decrease the total organic carbon, ammonia nitrogen, and total nitrogen of the aqueous phase and elemental content of the hydrochar especially produced at high temperatures. Formation Fe₂O₃ could also catalyze hydrochar combustion. At different HTC temperatures, the difference between dehydration and decarboxylation could also be observed. The results would give more help to the treatment of protein-rich organic waste, particular using HTC method.