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

Abstract

• Enhancing hydrolysis was a key step to improving dehydration, decarboxylation, deamination and oxidation reaction for SS during HTC. • FN can notably decrease TOC, NH 3 -N and TN and decrease elemental content in hydrochar especially at high temperatures. • Formation Fe 2 O 3 also could catalyze hydrochar combustion. • The role of oxidation also can be limited by the amount of FN. Fe(NO 3 ) 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(NO 3 ) 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 Fe 2 O 3 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.