Iron valence state evolution and hydrochar properties under hydrothermal carbonization of dyeing sludge. (October 2022)

• Record Type: Journal Article
• Authors: Xiao, Yao; Ding, Lu; Yang, Yu; Areeprasert, Chinnathan; Gao, Yunfei; Chen, Xueli; Wang, Fuchen
• Is Part Of: Waste management. Volume 152(2022)
• Page Start: 94
• Page End: 101
• Publication Date: 2022-10
• Subjects: Fe migration -- Hydrochar properties -- Dyeing sludge -- Hydrothermal carbonization -- HNO3 addition; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2022.07.009
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: The effect of HTC on hydrochar properties and Fe migration behavior were studied. The yield of HHC (60.70%∼69.62%) was much lower than that of WHC (66.77%∼80.91%) The content of total Fe and Fe 3+ of hydrochar decreased with increasing temperature. Fe could more easily entered the internal pores of the hydrochar. Fe3 O4 peak appeared in HHC and the intensity was enhanced with higher temperature. Abstract: Iron (Fe) migration mechanisms and hydrochar properties in dyeing sludge hydrothermal carbonization (HTC) are important topics in wastewater treatment. HTC treatment of sludge produces wastewater containing Fe so it is necessary to study the migration behavior of Fe during HTC treatment. This study investigated the basic properties and Fe migration behavior of hydrochar during HTC treatment supplemented with nitric acid (HNO3 ). The results showed that the carbonization degree and yield of hydrochar treated with the HNO3 solution (HHC) were much lower than those of hydrochar treated with ultrapure water (WHC). The variation of total Fe (TF) concentration indicated that the decomposition of organic material and dissolution of minerals in the aqueous release of Fe during the liquid phase, led to much lower TF concentrations compared to the original dyeing sludge. Fe release was further enhanced with the addition of HNO3 and increase of temperature, rendering a much lower TF concentration of the HHC compared to the WHC. The variations of Fe 3+ and Fe 2+ concentrations indicated that the HTC-treated hydrochar contained more Fe 2+, caused by Fe 3+ reduction with hydroxyl methyl-furfural and glucose in the liquid and subsequent Fe 2+ /Fe 3+ transferral to the solid hydrochar phase. X-ray diffraction (XRD) showed that the main Fe content in WHC was FeO(OH), while HHC contained mainly Fe(SO4 )(OH)2H2 O and Fe3 O4 . XPS and XRF showed that Fe could more easily enter the internal pores of the hydrochar instead of being deposited on the surface. This study provided more insights on Fe migration behavior during HTC treatment.