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Wildfires in polluted areas: mineralogical transformations and remobilization of metal(loid)s
Tuhý, Marek ; Ettler, Vojtěch (advisor) ; Navrátil, Tomáš (referee) ; Campos, Isabel (referee)
Wildfires contribute to the global emissions of trace elements. This Ph.D. thesis focuses on highly polluted areas near smelting/mining polluted sites in Africa, where wildfires are frequent. Experimental samples corresponding to both representative biomass-rich topsoils and grass were investigated using a combination of mineralogical and geochemical methods. Wildfires were simulated using a thermodesorption (TD) technique (75-670 řC; Hg) and newly introduced experimental set-ups (250-850 řC), enabling the online detection of the released contaminants and the sampling the aerosols and ashes. The subsequent investigation revealed the mineralogical and chemical transformations necessary for understanding the temperature- dependent releases of the metal(loid) contaminants during the simulated wildfire. The thermodesorption experiments indicated that >90 % of Hg was released at ~340 řC. A comparison with the Hg reference compounds' TD curves confirmed that the Hg in the biomass- rich topsoils occurs as a mixture of the Hg bound to the organic matter and nanocrystalline black HgS, which exhibited similarities with the TD pattern of smelter flue dust residue. The release of the other metal(loid)s from the topsoils (As, Cd, Cu, Pb, Zn) is dependent on their solid-state speciation, which was determined by...
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Geochemistry and mineralogy of Cu-Co smelting slags from Luanshya, Zambian Copperbelt
Natherová, Vendula ; Ettler, Vojtěch (advisor) ; Kříbek, Bohdan (referee)
This diploma thesis focuses on bulk chemical and mineralogical compositions of modern slags from Cu metallurgy at the Luanshya site in the Zambian Copperbelt. The aim of this thesis was to describe the formation of these slags, distribution of trace elements and their leachability. Slag samples were characterized using a combination of analytical methods (optical microscopy, scanning electron microscopy, X-ray diffraction analysis, quantitative microanalysis, electron microprobe analysis and leaching test designed to assess the environmental risk . Slags are mainly composed of silicates (clinopyroxene and fayalite) and silicate glass. Less common are melilite, leucite and monticellite. Grains of quartz were occasionally found in the slag matrix and correspond to a non-melted gangue. Copper is bound in sulfides or forms small inclusions trapped within in the silicate matrix. The crystallization process was probably relatively fast as revealed by skeletal crystals of olivine and the presence of glass. Copper concentrations in slags range from 1321-95 300 mg/ kg, Co concentrations in slags range from 247-5990 mg/kg. The EN 12457-2 leaching test demonstrated that harmful elements are not substantially released into the environment.
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Perspectives of flue-gas desulphurisation gypsum and rock gypsum in the Czech Republic
Nymsa, Zdeněk ; Přikryl, Richard (advisor) ; Ettler, Vojtěch (referee)
Flue gas desulphurisation (FGD) gypsum makes one of the so-called coal combustion by-products. FGD gypsum is the mostly used type of synthetic gypsum. In many applications, it can fully substitute natural rock gypsum (e.g. in wallboard production or as setting retarder in cement industry). Production and usage of FGD gypsum is directly connected with electricity generation based on coal combustion. In a broad scale, FGD gypsum appeared in Japan, USA, and Western Europe in 1970s-1980s, a bit later (in 1990s) also in Central Europe. During recent decades, the technology quickly spreads in Asia (China, India, etc.) as well. Ironically, the countries which used FGD gypsum technology as the first, will be probably also the first one which will cease the technology due to demise from energy generation in coal power stations. With a certain delay, similar trend is expected in the Czech Republic as well. Based on this presumption, this BSc. thesis discusses various scenarios, including possibility of long-term deposition of FGD gypsum in order to allow its usage over longer period in the future. Besides this, the thesis also strengthens the importance of natural gypsum, which will replace FGD gypsum in the future.
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Pb-Zn slags from Kabwe (Zambia): mineralogy and gastric bioaccessibility of contaminants
Štěpánek, David ; Ettler, Vojtěch (advisor) ; Jarošíková, Alice (referee)
This bachelor thesis focuses on slags originating from Imperials Smelting Process (ISP) and Waelz metallurgical process in Kabwe, Zambia, where Pb-Zn ores have been historically processed. The aim of this thesis was to characterize the chemical and mineralogical compositions of the slags and to assess the bioaccessibility of contaminants (Cd, Pb, V, Zn) from the slag dusts in simulated gastric conditions to evaluate the potential health risks for humans. Slags are particularly enriched in Pb (up to 62700 mg/kg) and Zn (up to 190300 mg/kg). Main contaminants (Pb, Zn, V) are bound in the slag glass, Fe and Mn oxides and hydroxides and carbonates. Vanadium is largely bound in complex phases such as vanadates, phosphates and sulphates. Contaminant concentrations are higher in slag dust (fractions <48 µm and <10 µm) than in the original granulated slag samples and ISP slags generally exhibit higher concentrations than the Waelz slags. During the leaching in simulated gastric conditions (0.4 M glycine, pH 1.5, 1 hour at 37 řC), abundant slag glass, (phyllo)silicates and carbonates were dissolved. In contrast, Fe oxides and hydroxides remained in the residue and were therefore stable during the leaching. Relative bioaccessibility of contaminants was rather high (up to 82 % Cd, 92 % Pb, 100 % V and 81 %...
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Geomaterials from mining and hydrometallurgical processing of Zn ores at Skorpion (Namibia): bioaccessibility of dust particles and variability in Zn isotope signal
Raus, Karel ; Ettler, Vojtěch (advisor) ; Vaněk, Aleš (referee)
This study is focused on the bioavailability of contaminants in dust particles from geomaterials from the extraction and hydrometallurgical processing of non-sulphide Zn ores at the site of Skorpion (Namibia) and the change of isotope signal in geomaterials and drill core samples. Mineralogical composition and bioaccessibility of contaminants were studied with RTG, SEM / EDS, EPMA and simple in vitro leaching test in simulated gastric fluid for fractions <48 μm and <10 μm representing the dust particles. Based on results from chemical analysis, Cd, Cu, Pb and Zn were identified as the main contaminants and their concentrations also significantly increased in the finer fractions compared to the original samples. The bioaccessible fraction (BAF) values ranged from 36-97% for Cd, 17-78% for Cu, 2-100% for Pb and 27-100% for Zn. Daily intake via oral exposure, calculated for an adult (70 kg, ingestion 100 mg / day), exceeded tolerable daily intake (TDI) limits for Cd (up to 1.95), Pb (up to 21.96) and Zn (up to 2.02). Ores originating from Turkey and Taiwan, used to adjust feed ore Zn concentration, were identified as the most hazardous materials. The bioavailability of contaminants depends on the mineralogical composition of the geomaterials and the particle size, but the risks for humans are...
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