Fly ash and H2O2 assisted hydrothermal carbonization for improving the nitrogen and sulfur removal from sewage sludge. (March 2022)

• Record Type: Journal Article
• Authors: Wang, Xiaobo; Shen, Yu; Liu, Xuecheng; Ma, Tengfei; Wu, Jin; Qi, Gaoxiang
• Is Part Of: Chemosphere. Volume 290(2022)
• Publication Date: 2022-03
• Subjects: Sewage sludge -- Hydrothermal carbonization -- Hydrochar -- Fly ash -- Hydrogen peroxide; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.133209
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this study, fly ash and hydrogen peroxide (H2 O2 ) assisted hydrothermal carbonization (HTC) was used to improve the removal efficiency of nitrogen (N) and sulfur (S) from sewage sludge (SS). The removal rate and distribution of N and S in hydrochar were evaluated, and properties of the aqueous phase were analyzed to illustrate the N and S transformation mechanism during fly ash and H2 O2 assisted HTC treatment of SS. The results suggested that during HTC process assisted by fly ash (10% of raw SS), dehydration, decarboxylation and hydrolysis of SS were strengthened due to the catalysis effect. The N and S removal were promoted marginally. For hydrochar achieved from HTC process with H2 O2 addition, the N and S removal were improved slightly due to the biopolymer oxidization by ‧OH released from H2 O2 decomposition. While for HTC treatment with fly ash and H2 O2 supplementation, a positive synergistic effect on N and S removal was observed. The N and S removal obtained from fly ash (10% of raw SS) and H2 O2 (48 g/L) assisted HTC increased to 81.71% and 62.83%, respectively, from those of 69.53% and 49.92% in control group. N and S removal mechanism analysis suggested that hydroxyl radicals (‧OH) produced by H2 O2 decomposition will destroy SS structure, and the biopolymers such as polysaccharides and proteins will be decomposed to release N and S into the liquid residue. In addition, the fly ash acts as the catalyst will decrease the energy need for denification and desulfartion. Consequently, N and S removal efficiency was enhanced by fly ash and H2 O2 assisted HTC treatment. Graphical abstract: Image 1 Highlights: Fly ash and H2 O2 assisted HTC was used to remove N/S from sewage sludge. C, N and S yield and distribution in hydrochar was investigated. N and S removal increased by 36.02% and 25.40% by fly ash and H2 O2 assisted HTC. Fly ash and H2 O2 assisted HTC facilitated N/S removal from sewage sludge. Catalysis and oxidization effect contributed to the low N/S contents in hydrochar.