Municipal solid waste and green chemistry

Recovery of phosphorus as struvite from sewage sludge ash

Huacheng Xu , Pinjing He , Weimei Gu , Guanzhao Wang , Liming Shao


Received October 16, 2011,Revised March 11, 2012, Accepted , Available online August 02, 2012

Volume 24,2012,Pages 1533-1538

Phosphorus (P) is an element vital for all living organisms, yet the world's reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite precipitation. Results showed that more than 95% of the total P content was extracted from sludge ash by applying 0.5 mol/L HCl at a liquid/solid ratio of 50 mL/g. Although heavy metal leaching also occurred during P extraction, cation exchange resin efficiently removed the heavy metals from the P-rich solution. Orthogonal tests showed that the optimal parameters for P precipitation as struvite would be a Mg:N:P molar ratio of 1.6:1.6:1 at pH 10.0. X-ray diffraction analysis validated the formation of struvite. Further investigations revealed that the harvested precipitate had a high struvite content (97%), high P bioavailability (94%), and low heavy metal content, which could be considered a high quality fertilizer.

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