Zugl.: Karlsruhe, Universiẗat, Diss., 1992.

Zugl.: Cottbus, Techn. Universiẗat, Diss., 1999.

Zugl.: Bayreuth, Universiẗat, Diss., 1997.

Freshwater shortages causes challenges in mineral processing in Chile, especially in arid regions. As a result, froth flotation; a mineral process, is shifting usage of freshwater to seawater. This has consequences in the consumption of flotation reagents and decreasing the flotation efficiency. Biotechnological developments allow conceptualising the use of bacterial cells and their metabolites as bioreagents in flotation; classified as bioflotation. In this thesis, 5 halophilic bacteria, namely, Halomonas boliviensis, Marinobacter spp., Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 have been screened for the potential use as pyrite biodepressants at micro- and batch-scale flotation. The effect of bioconditioning minerals with these bacteria was studied using zeta potential, fluorescence microscopy and contact angle. Experiments measuring zeta potential show the isoelectric point (IEP) of pyrite, chalcopyrite and molybdenite became more acidic post-bioconditioning. Fluorescence microscopy with Nile red; a hydrophobic stain, allowed for a method to visualize bacterial cells or collector potassium isopropyl xanthate (KIPX) on mineral particles of pyrite, chalcopyrite and molybdenite. Additionally contact angle experiments show that strains Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 had an influence on the contact angle of pyrite and chalcopyrite, inducing changes in their hydrophobicity. Microflotation experiments showed a decreased recovery of pyrite in presence of all strains, but notably, Halobacillus litoralis Hol-1 and Marinococcus halophilus KOR-3, also showed an increased recovery of chalcopyrite, making them ideal candidates as pyrite biodepressants. Halomonas eurihalina P6-1 showed low recoveries of both minerals, but a higher selectivity depressing more pyrite than chalcopyrite. Usage of autoclaved biomass from the three aforementioned strains in batch-flotation experiments resulted in the recovery of chalcopyrite improving, with a small decrease in the recovery of pyrite, overall showing a positive potential but not improving the system. Halophilic bacteria such as the ones used in this study show an influence on the floatability of pyrite, which could be commercially exploited to substitute lime as a pyrite depressant. Furthermore, the work in this thesis focused on studying the effects of cells in artificial seawater, both at micro and batch-scales which brings the laboratory experiments a step closer to industrially relevant conditions.

The neoidic sulphide mineralization located in tertiary sediments of Lom Bílina in Bílina's fault is of hydrothermal origin. The sulphidic mineralization is associated with fault systems of Eger rift and temperature of fluid crystallization was about 50řC. The mineralization of Bílina's fault is rather monotonous, the marcasite and pyrite is mostly found without a trace elements. In the crystals were also registered zones with the contents of trace elements, especially As and Ni. The contents of As enriched precipitation zones were fluctuating from 0,2 to 5,4 wt. %, Ni enriched zones were ranged from 1,6 to 5,9 wt. %. The precipitation zones with increased As and Ni content were very thin, there were very short time intervals of As and Ni enriched fluids precipitation. In the marcasite crystals were also found the porous zones of clay mineral microinclusions. These zones showed higher content of Al and Si. There is high abundance of Fe-disulfides at Bílina's fault-dispersed in coal bed, or bonded to tectonic zone of the Bílina's fault. Pyrite and marcasite are dispersed in the coal bed and genetially aren't related to sulphides bonded to Bílina's fault.

<p>Chemical stabilization of mine waste from Ljusnarsbergsfältet with sewage sludge and calcium carbonate residues</p><p>Mine waste from Ljusnarsbergsfältet in Kopparberg, Sweden, is considered to constitute a great risk for human health and the surrounding environment. Some of the waste rock consists of sulphide minerals. When sulphide minerals come into contact with dissolved</p><p>oxygen and precipitation, oxidation may occur resulting in acid mine drainage (AMD) and the release of heavy metals. The purpose of this study has been to characterise the waste material and try to chemically stabilize the waste rock with a mixture of sewage sludge and calcium carbonate. The drawback of using organic matter is the risk that dissolved organic matter can act as complexing agents for heavy metals and in this way increase their mobility. An additional study to examine this risk has therefore also been performed.</p><p>The project started with a pilot study in order to identify the material fraction that was suitable for the experiment. When suitable material had been chosen, a column test was carried out for the purpose of studying the slurry’s influence on the mobility of metals along with the production of acidity. To clarify the organic material’s potential for</p><p>complexation a pH-stat batch test was used. Drainage water samples, from the columns,</p><p>were regularly taken during the experiment. These samples were analyzed for pH, electrical conductivity, alkalinity, redox potential, dissolved organic carbon (DOC), sulphate and leaching metals. The effluent from the pH-stat-test was only analyzed on a few occasions and only for metal content and change in DOC concentration.</p><p>The results from the laboratory experiments showed that the waste rock from Ljusnarsberg easily leached large amounts of metals. The stabilization of the waste rock succeeded in maintaining a near neutral pH in the rock waste leachate, compared to a pH 3 leachate from untreated rock waste The average concentration of copper and zinc in the leachate from untreated waste rock exceeded 100 and 1000 mg/l respectively, while these metals were detected at concentrations around 0.1 and 1 mg/l, respectively, in the leachate from the treated wastes. Examined metals had concentrations between 40 to 4000 times lower in the leachate from treated waste rock, which implies that the stabilization with reactive amendments succeeded. The long term effects are, however, not determined. The added sludge contributed to immobilize metals at neutral pH despite a small increase in DOC concentration. The problem with adding sludge is that if pH decreases with time there is a risk of increased metal leaching.</p>

Die Arbeit entwickelt eine Methodik zur Gefährdungsprognose der Kippenumgegend durch stark mineralisierte, saure Kippengrundwässer. Für die Standorte Espenhain und Jänschwalde wurden Feld- und Laboruntersuchungen sowie Simulationen zur Wiederaufsättigung und zum reaktiven Stofftransport durchgeführt. Die geochemische Vorfeldbilanzierung ist ein wesentliches Werkzeug zum Verständnis der sich entwickelnden Kippenwasserbeschaffenheiten. Die Felduntersuchungen auf der Kippe Espenhain zeigen im Liegenden der Verwitterungszonen den Ablauf reduktiver Prozesse, verkoppelt mit der Umsetzung tertiärer organischer Substanz. Deren lokal nachgewiesene Abfolge bis zur Sulfatreduktion ist ein nachhaltiger Selbsthilfemechanismus bezüglich der durch Verwitterung freigesetzten Acidität und Metalle. Die weitere Untersuchung der Redoxsequenz und ihrer technischen Beeinflussbarkeit ist geboten. Innerhalb der Arbeit wird das reaktive Stofftransportprogramm PCGEOFIM verifiziert und für beide Standorte angewendet.

Chemical stabilization of mine waste from Ljusnarsbergsfältet with sewage sludge and calcium carbonate residues Mine waste from Ljusnarsbergsfältet in Kopparberg, Sweden, is considered to constitute a great risk for human health and the surrounding environment. Some of the waste rock consists of sulphide minerals. When sulphide minerals come into contact with dissolved oxygen and precipitation, oxidation may occur resulting in acid mine drainage (AMD) and the release of heavy metals. The purpose of this study has been to characterise the waste material and try to chemically stabilize the waste rock with a mixture of sewage sludge and calcium carbonate. The drawback of using organic matter is the risk that dissolved organic matter can act as complexing agents for heavy metals and in this way increase their mobility. An additional study to examine this risk has therefore also been performed. The project started with a pilot study in order to identify the material fraction that was suitable for the experiment. When suitable material had been chosen, a column test was carried out for the purpose of studying the slurry’s influence on the mobility of metals along with the production of acidity. To clarify the organic material’s potential for complexation a pH-stat batch test was used. Drainage water samples, from the columns, were regularly taken during the experiment. These samples were analyzed for pH, electrical conductivity, alkalinity, redox potential, dissolved organic carbon (DOC), sulphate and leaching metals. The effluent from the pH-stat-test was only analyzed on a few occasions and only for metal content and change in DOC concentration. The results from the laboratory experiments showed that the waste rock from Ljusnarsberg easily leached large amounts of metals. The stabilization of the waste rock succeeded in maintaining a near neutral pH in the rock waste leachate, compared to a pH 3 leachate from untreated rock waste The average concentration of copper and zinc in the leachate from untreated waste rock exceeded 100 and 1000 mg/l respectively, while these metals were detected at concentrations around 0.1 and 1 mg/l, respectively, in the leachate from the treated wastes. Examined metals had concentrations between 40 to 4000 times lower in the leachate from treated waste rock, which implies that the stabilization with reactive amendments succeeded. The long term effects are, however, not determined. The added sludge contributed to immobilize metals at neutral pH despite a small increase in DOC concentration. The problem with adding sludge is that if pH decreases with time there is a risk of increased metal leaching.

Die Arbeit entwickelt eine Methodik zur Gefährdungsprognose der Kippenumgegend durch stark mineralisierte, saure Kippengrundwässer. Für die Standorte Espenhain und Jänschwalde wurden Feld- und Laboruntersuchungen sowie Simulationen zur Wiederaufsättigung und zum reaktiven Stofftransport durchgeführt. Die geochemische Vorfeldbilanzierung ist ein wesentliches Werkzeug zum Verständnis der sich entwickelnden Kippenwasserbeschaffenheiten. Die Felduntersuchungen auf der Kippe Espenhain zeigen im Liegenden der Verwitterungszonen den Ablauf reduktiver Prozesse, verkoppelt mit der Umsetzung tertiärer organischer Substanz. Deren lokal nachgewiesene Abfolge bis zur Sulfatreduktion ist ein nachhaltiger Selbsthilfemechanismus bezüglich der durch Verwitterung freigesetzten Acidität und Metalle. Die weitere Untersuchung der Redoxsequenz und ihrer technischen Beeinflussbarkeit ist geboten. Innerhalb der Arbeit wird das reaktive Stofftransportprogramm PCGEOFIM verifiziert und für beide Standorte angewendet.

Technetium is the lightest element whose isotopes are all radioactive. Among them, 99Tc (hereafter simply referred as technetium or Tc) is the most abundant and raises great environmental concern due to its relatively long half-life of 2.14×105 years and the high mobility of pertechnetate, Tc(VII)O4, its most stable form under aerobic conditions. The reduction from Tc(VII) to Tc(IV) is one of the most successful strategies for Tc immobilization; however, the mechanism of this redox reaction is not yet fully understood. This presents a large gap in the general knowledge of technetium chemistry and a significant obstacle for the modeling of its reactivity in contexts like a nuclear waste repository. This thesis was developed in the frame of the BMWi funded VESPA II project, and it studies the surface-mediated reduction of 99Tc(VII) using a combination of fundamental chemistry and its application for remediation and nuclear waste management. First, spectro-electrochemical methods (cyclic voltammetry, rotating disk electrode, chronoamperometry coupled with UV-vis, Raman microscopy and nuclear magnetic resonance) were employed to study the reduction mechanism of 0.5 mM KTcO4 in non-complexing media (2 M NaClO4) in the pH range from 2.0 to 10.0. It was found that the mechanism depends on the pH. At pH 2.0 it splits into two steps: Tc(VII) gains 2.1 ± 0.3 electrons and becomes Tc(V) that rapidly reduces to Tc(IV) with the transfer of further 1.3 ± 0.3 electrons. In contrast, at pH ≥ 4.0 there is a direct transfer of 3.2 ± 0.3 electrons. The complete reduction of Tc(VII) yielded a black solid that was successfully characterized by NMR and Raman microscopy as Tc(IV) regardless of the initial pH at which the reaction occurred. Unfortunately, it was not possible to observe the Tc(V) species at pH 2.0 by the spectroscopic tools used. Second, the reductive immobilization of Tc(VII) by pure pyrite and a synthetic mixture marcasite-pyrite 60:40 (synthetic FeS2, with both minerals being polymorphs) was studied by a combination of batch sorption experiments (Tc-removal was studied varying pH, contact time, ionic strength and Tc concentration) and several spectroscopies and microscopies such as Raman microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and VIII X-ray absorption spectroscopy. It was found that both pyrite and the synthetic FeS2 promote the reduction of Tc(VII) to Tc(IV). In the case of pure pyrite, the Tc-removal is complete after one day in contact at pH ≥ 5.5. The spectroscopic analysis showed at pH 6.0 an inner-sphere complex between Tc(IV) dimers and hematite formed as secondary mineral on the pyrite surface. In contrast, at pH 10.0 Tc(IV) gets incorporated into surficial magnetite by replacing Fe3+ in octahedral position, with Fe2+ providing reasonable charge compensation for Tc4+. The presence of marcasite made the process slower and less efficient since the synthetic FeS2 was capable to remove 100% Tc from solution only after seven days in contact at 6.0 < pH ≤ 9.0 while the Tc-removal at pH 10.0 was only around 80%. At pH 6.0 the formation of hematite was also observed, suggesting that the formed Tc(IV) species at the surface is the same as with pure pyrite. However, at pH 10.0 the formation of sulfate minerals evidences a change of redox active species: S2- instead of Fe2+. This, combined with the fact that in both solids the formation of TcSx species was detected by XPS at pH 10.0, shows the potential of sulfur as another reducing agent for Tc(VII). The effect of polymorphism on the Tc removal is remarkable and this work shows the relevance of more studies on the interaction of radionuclei with other mineral polymorphs. Regardless of the kinetics of the Tc removal, both pyrite and synthetic FeS2 hindered the re-oxidation of Tc(IV) when exposed to ambient atmosphere for two months. This feature makes them good candidates for the remediation of technetium from contaminated waters. Moreover, natural attenuation effects can be expected for technetium in the near and far field of nuclear waste repositories wherever iron sulfide is present. The results presented in this work contribute to a better understanding of the fundamental aqueous chemistry of technetium and confirm pyrite, a ubiquitous mineral, as a very good candidate for technetium scavenging even in the presence of marcasite. These results close important gaps in thermodynamic databases that are needed for the safety assessment, i.e. modeling of fission products.