A sustainable strategy for recovery of phosphorus as vivianite from sewage sludge via alkali-activated pyrolysis, water leaching and crystallization. (15th April 2023)

• Record Type: Journal Article
• Authors: Yang, Liang; Guo, Xiao; Liang, Sha; Yang, Fan; Wen, Mingxuan; Yuan, Shushan; Xiao, Keke; Yu, Wenbo; Hu, Jingping; Hou, Huijie; Yang, Jiakuan
• Is Part Of: Water research. Volume 233(2023)
• Publication Date: 2023-04-15
• Subjects: Sewage sludge -- Phosphorus recovery -- Alkali-activated pyrolysis -- Biochar -- Water-soluble phosphorus -- Vivianite; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119769
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: A sustainable strategy for recovering phosphorus (P) from sewage sludge is proposed. Alkali-activated pyrolysis enhances the generation of water-soluble P (Water-P). Fe element in the sludge conditioner enhances the Water-P content in biochar. The Water-P content in biochar by KHCO3-activated pyrolysis could reach 100%. 88.08% of the P in sewage sludge could be recycled as vivianite product. Abstract: A sustainable strategy for P recovery from sewage sludge via alkali-activated pyrolysis, water leaching and crystallization was proposed, and a high value-added product of vivianite was recovered. Effects of the type and dose of alkali activator on P transformation during sludge pyrolysis were investigated. 50 wt% dose of KHCO3 was determined as the alkali-activated pyrolysis condition. The content of water-soluble P (referred to as Water-P) in biochar derived from raw sludge (referred to as RS) and ferric sludge (Fenton's reagent conditioned sludge, referred to as FS) by KHCO3 -activated pyrolysis at different temperatures was compared. The Fe element in the Fenton's reagent enhanced the content of Fe-bound P in the dewatered sludge, which was readily transformed into potassium phosphate during KHCO3 -activated pyrolysis, thus increasing the Water-P content in the biochar derived from FS. The proportions of Water-P to total P in the biochar samples obtained by KHCO3 -activated pyrolysis of RS and FS at 600 °C were 72.5% and 96.2%, respectively, which were notably higher than those in the biochar samples obtained by direct pyrolysis of RS and FS (3.5% and 0.5%), respectively. The water leaching solution of biochar obtained by KHCO3 -activated pyrolysis of FS at 600 °C was purified to remove impurity elements, and vivianite with high purity was finally recovered by crystallization. A total P recovery efficiency of 88.08% was achieved throughout the process from sewage sludge to the final vivianite product. This study proposes a promising and sustainable approach for realizing the recovery of high value-added product vivianite from sewage sludge. Graphical abstract: Image, graphical abstract