Effect of high-content metals on the phosphorus forms and release of sludge-derived biochar
Municipal sludge was enhanced pretreated with high-content metal and then pyrolyzed to form various sludge-derived biochar at low temperature.Pearson's correlation analysis and characterization methods were employed to investigate the effects of high-content metal and pyrolysis temperature on phosphorus forms and phosphorus release from sludge-derived biochar.The results showed that the phosphorus release from sludge-derived biochar decreased with the increase of pyrolysis temperature,and a large amount of internal phosphorus was converted into ortho-P at 350℃.The enhanced pretreatment and pH had a greater effect on the phosphorus release and immobilization of metal element than pyrolysis temperature.Fe/Al-P and Ca-P competed for the coexistence of phosphorus,and Fe/Al-P was slightly dominant,while Ca-P had a significant effect on IP species.The ability of high-content metal to promote the conversion of OP to IP,inhibit phosphorus release,and hinder the conversion of HPO42-to H2PO4-was Fe>Al>Ca.The dominant phosphorus of calcium-based,and iron-and aluminum-based sludge-derived biochar were Ca-P and Fe/Al-P,respectively,of which Fe/Al-P was encapsulated by iron-aluminum oxides and was more difficult to release.Ca(H2PO4)2 was the primary form of phosphorus release.Fe-enhanced pretreatment has the greatest effect on the form and release of phosphorus in sludge-derived biochar,and Ca-enhanced pretreatment is conducive to the enhancement of bioavailable phosphorus,potentially providing new ideas for the resource utilization of municipal sludge-derived biochar.
municipal sludgehigh-content metalssludge-derived biocharphosphorus formsphosphorus release
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