Influence of calcining parameters of FePO 4 and CaO compositions on the solubility of phosphorus compounds

Influence of calcining parameters of FePO 4 and CaO compositions on the solubility of phosphorus... Purpose – To determine the influence of alkali components (especially Ca compounds) on the hematite phase formation during thermal processing of sewage sludge and the observation of transformations proceeding at different ratios of Ca to FePO 4 . Design/methodology/approach – The model compositions were heated to temperatures of 600°C and 950°C, then calcined within 3 hours without mixing. Cooled products were subjected chemical analysis regarding the content of phosphorus that was soluble in cold water, 0.4 per cent HCl, 2 percent citric acid and aqua regia as well as crystallographic identification. Findings – On calcining at 600°C, CaO reacts with FePO 4 , forming hydroxylapatite. The hematite phase which is insoluble in mineral acids crystallizes above 600°C. Further increasing the calcining temperature leads to transformations resulting in Ca 9 Fe(PO 4 ) 7 and hematite formation. Molar ratios of CaO to FePO 4 · 2H 2 O of 1.0 and 2.0 lead to hematite phase formation and increase the availability of phosphorus compounds (characterized by phosphate solubility in 0.4 percent HCl and 2 percent citric acid) in compositions after calcining. Practical implications – The addition of CaO to sewage sludge before the combustion process should be beneficial from the point of view of further extraction of phosphorus compounds from the ash obtained. Suitable CaO addition favours iron binding into the hematite phase and raises the solubility of the phosphorus compounds in the ashes formed. Originality/value – This paper is a new source of information which complements existing knowledge about phosphorus recovery from sewage sludge. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Management of Environmental Quality: An International Journal Emerald Publishing

Influence of calcining parameters of FePO 4 and CaO compositions on the solubility of phosphorus compounds

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Publisher
Emerald Publishing
Copyright
Copyright © 2005 Emerald Group Publishing Limited. All rights reserved.
ISSN
1477-7835
DOI
10.1108/14777830510623691
Publisher site
See Article on Publisher Site

Abstract

Purpose – To determine the influence of alkali components (especially Ca compounds) on the hematite phase formation during thermal processing of sewage sludge and the observation of transformations proceeding at different ratios of Ca to FePO 4 . Design/methodology/approach – The model compositions were heated to temperatures of 600°C and 950°C, then calcined within 3 hours without mixing. Cooled products were subjected chemical analysis regarding the content of phosphorus that was soluble in cold water, 0.4 per cent HCl, 2 percent citric acid and aqua regia as well as crystallographic identification. Findings – On calcining at 600°C, CaO reacts with FePO 4 , forming hydroxylapatite. The hematite phase which is insoluble in mineral acids crystallizes above 600°C. Further increasing the calcining temperature leads to transformations resulting in Ca 9 Fe(PO 4 ) 7 and hematite formation. Molar ratios of CaO to FePO 4 · 2H 2 O of 1.0 and 2.0 lead to hematite phase formation and increase the availability of phosphorus compounds (characterized by phosphate solubility in 0.4 percent HCl and 2 percent citric acid) in compositions after calcining. Practical implications – The addition of CaO to sewage sludge before the combustion process should be beneficial from the point of view of further extraction of phosphorus compounds from the ash obtained. Suitable CaO addition favours iron binding into the hematite phase and raises the solubility of the phosphorus compounds in the ashes formed. Originality/value – This paper is a new source of information which complements existing knowledge about phosphorus recovery from sewage sludge.

Journal

Management of Environmental Quality: An International JournalEmerald Publishing

Published: Dec 1, 2005

Keywords: Waste management; Sewage

References

  • Phosphorus Removal and Recovery Technologies
    Brett, S.; Guy, J.; Morse, G.K.; Lester, J.N.

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