Termické chování vybraných minerálů/fází arzenu a jeho environmentální důsledky

Stonová, Kateřina

iii ABSTRACT This bachelor's thesis focuses on the thermal behaviour of the following arsenic-bearing minerals: enargite (Cu3AsS4), realgar (As4S4), orpiment (As2S3), mimetite [Pb5(AsO4)3Cl] and conichalcite [CaCu(AsO4)(OH)]. Additionally, the behaviour of a synthetic analogue of realgar and an organoarsenic compound (cacodylic acid) was investigated. The experiments were conducted in an argon atmosphere and the temperature range 20-800 řC, with a linear temperature increase. Emissions of arsenic and other elements (S and Pb) were detected using ICP-OES. The thermal behaviour was further analysed by simultaneous DSC and TGA, and the mineralogical composition of the residues was determined by X-ray diffraction analyses. The least stable minerals were realgar and orpiment, melting at 300-320 řC and subsequently releasing arsenic and sulphur (with the highest release at 400-450 řC). Enargite decomposed in the studied temperature range with a 40 % mass loss, emitting the most arsenic and sulphur around 600 řC. Conichalcite also underwent decomposition, losing ca. 3 % of mass and releasing arsenic especially around 700 řC. Mimetite proved the most stable, losing almost no mass and starting to emit arsenic, simultaneously with lead, near the upper limit of the temperature range. The results align with previously...

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