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106

u

s

Fe

Figurę 4.11 SEM backscattered electron image and elemenial composition of

released condensed gas during thennal treatment.

4.4 Conclusion

Calamine processmg wastes were eharaeterized m order to their potential reuse as ceramic materiał. This type of waste is mainly composed of CaO. Fe:03 and Iow amounts of SiCb. The CPMT presents higher amounts of fluxing agent oxides (NaiO. K:0. PbO) which enhance the smtering and densifłcation of the derived fired products. The amounts of CaO and Na^O mcrease sligłitly afier thennal treatment. The mineralogical XRD analysis shows that gypsum (CaS04.2H20). ąuartz (SiCb) and calcite (CaC03) are the main crystalhne pliases present in the calamine process minę tailings. When fired to high temperatures, various trans format ions take place. Gypsum is transformed mto anliydrite (CaSOih amorphous iron hydroxides are transformed mto magnetite (Fe304) andhematite (Fe:03 K and carbonates minerals are decomposed. These transformations affect significantly the physical and mechanical properties of fired samples due to the amount of gas released which leads to high amounts of pores. At 1050^:‘C. new phases such as augite (Ca(Fe.Mg)Si20ć) andgehlenite (CmAliShOj) are formed.