This paper sets out to observe the changes occurring during thermal processing of Na2CO3 and FePO4 · 2H2O in control trials, then analyses the influence on availability of phosphorus compounds in comparison with pure FePO4 · 2H2O.
Control trials of Na2CO3/FePO4 · 2H2O with molar ratios in the range 0.5‐5.0 were heated to a temperature of 850°C, then calcined within 3 hours without mixing. Cooled products were submitted for chemical analysis regarding the content of phosphorus soluble in cold water, 0.4 percent HCl, 2 percent citric acid and aqua regia as well as crystallographic identification.
The addition of Na2CO3 significantly increases the availability of phosphorus compounds from FePO4 · 2H2O. The total amount of phosphorus in control trials after the calcining process is soluble in cold water, citric acid and HCl. The molar ratios used affect the type of crystalline phase formation only in the case of a molar ratio near to 1.0. Near‐perfect phosphorus availability in hematite phase formation was observed.
These preliminary results confirm the necessity for further investigation of the addition of Na2CO3 into industrial sewage sludge before the calcining process. The results may allow for a decrease in energy use during the combustion process and may create the possibility of recovering phosphorus compounds from ash using only cold water instead of mineral acids during the extraction process.
This paper is a new source of information about phosphorus recovery from sewage sludge.
Wzorek, Z., Gorazda, K., Minda, D. and Kulczycka, J. (2005), "Influence of thermal processing of FePO4 · 2H2O with Na2CO3 on solubility of phosphorus compounds in mixtures after sintering", Management of Environmental Quality, Vol. 16 No. 6, pp. 639-646. https://doi.org/10.1108/14777830510623709Download as .RIS
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