ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 50, (3) 178 - 184 (2006)

Kaziliunas Antanas 1, Leskeviciene Violeta 2, Vektaris Bronius 1, Valancius Zenonas 2
1 Institute of Architecture and Construction, Kaunas University of Technology, Tunelio Str. 60, LT-44405 Kaunas, Lithuania
2 Department of Silicate Technology, Faculty of Chemical Technology, Kaunas University of Technology, Radvilenu Str. 19, LT-50254 Kaunas, Lithuania

Keywords: Phosphogypsum, Impurities, Neutralization, Properties, Binding materials

The paper presents the characterization of dihydrate phosphogypsum impurities, both in laboratory and in industrial scale, and chemical process of their neutralization in the lime suspension. The fastest and controlling processes of transfer water soluble impurities to insoluble compounds of calcium orthophosphates {Ca₃(PO₄)₂ ·nH₂O and Ca₅(PO₄)₃OH·mH₂O}, CaF₂, CaSiF₆, Ce(OH)₃ were determined. The impurities in the phosphogypsum crystals were neutralized under hydrothermal conditions (in an autoclave). The increased quantity of alkalies in the recycling water did not have influence on the phosphogypsum neutralization process and on the properties of the plaster made from phoshpogypsum. Neutralized phosphogypsum may be used in the production of gypsum binding materials.

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