<p>Most of the city of Uppsala rests on postglacial clay with a varying content of sulphur. The sulphur occurs naturally in the clay in reduced form as sulphide and the clay is for that reason usually called “sulphide clay”. Excavation during construction activities gives rise to large amounts of excavation material, of which the sulphide clay is a considerable part.</p><p>When the clay is exposed to air and water, an oxidation of the sulphides occurs which may produce an acid leachate and the mobilisation of heavy metals bound in the clay or underlying material. The aim of the work has been to improve our understanding of the behaviour of sulphide clays and produce a basis for risk assessment in the future handling of excavation material with high sulphide content. After sampling had been carried out in two places, batch tests were performed to examine the long-term acidification potential of clays with different calcium carbonate content. The tests were performed with continuous air supply and during the experiment leachate water was analysed with respect to pH, alkalinity, dissolved sulphate and mobilised metals. The results from the laboratory study showed that a clay with a high calcium carbonate content and thus a high net neutralisation potential (NNP) will consume the generated acid and prevent against a lowering of the pH.</p><p>In clay lacking calcium carbonate, the pH dropped significantly and caused a mobilisation of chiefly Cd, Mn, Co, Ni, Ca and As. Regardless of the changes in pH over time, a large production of sulphur was observed as a result of the sulphide oxidation. In a risk assessment, it is suggested that the NNP should be determined by methods agreed upon to facilitate future comparisons and because different methods may give different results. A clay with a NNP<5 kg CaCO3/ton should be further analysed with respect to metal content to establish the leachate generation potential and estimate the future environmental influence of the excavation material.</p> / <p>Uppsala stad vilar till stor del på postglacial lera med varierande svavelhalt. Svavlet finns naturligt i leran i reducerad form som sulfid och leran kallas därför vanligtvis för ”sulfidlera”. Vid schaktningsarbete i samband med byggnation uppkommer stora mängder schaktmassor varav en betydande del är sulfidlera.</p><p>Då leran exponeras för luft och nederbörd sker en oxidation av sulfiderna som kan ge upphov till surt lakvatten och läckage av tungmetaller bundna i leran eller underliggande material. Syftet med arbetet har varit att öka kunskaperna om hur sulfidleror beter sig och ta fram ett underlag för riskbedömning i samband med den framtida hanteringen av sulfidhaltiga schaktmassor i Uppsala. Efter genomförd provtagning på två platser utfördes skaktest för att undersöka den långsiktiga försurningspotentialen hos lera med varierande kalkinnehåll. Testerna utfördes med kontinuerlig tillförsel av luft och löpande under försökets gång togs lakvatten ut för analys avseende pH, alkalinitet, löst sulfat och utlakade metaller.</p><p>Resultaten från den laborativa studien visade att en kalkhaltig lera med hög nettoneutralisationspotential (NNP) kan förbruka den bildade syran och därigenom genereras ingen pH-sänkning. I lera som saknar kalk sjönk pH kraftigt och föranledde läckage av framförallt Cd, Mn, Co, Ni, Ca och As.</p><p>Oavsett utvecklingen av pH observerades en stor utlakning av svavel till följd av oxidationen av sulfider. I en riskbedömning föreslås att lerans NNP bestäms enligt överenskomna metoder för att underlätta framtida jämförelser och för att olika tekniker kan ge olika resultat. En lera med NNP-värde < 5 kg CaCO3/ton bör analyseras vidare avseende metallinnehåll för att fastställa den potentiella utlakningen och bedöma schaktmassans framtida naturpåverkan.</p>

Ph. D., Faculty of Science, University of the Witwatersrand, 2011 / Different cadmium, cobalt and zinc complexes of substituted thioureas, dithiocarbamates and thiuram di/monosulfides were synthesized using ethanol or water as solvents. The synthesis of dithiocarbamates complexes were performed at room temperature while the rest were refluxed at 70 oC. The complexes were easy to synthesize, of low cost and stable in air and were obtained in good yields. The complexes were characterized using various instruments, such as infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy, elemental analyzer, thermogravimetric analysis (TGA) and X-ray crystallography. The complexes were found to coordinate the ligands through sulphur atom, instead of nitrogen atom. This was concluded after shifts to higher or lower wavenumbers were observed from the infrared spectra of the complexes as compared to their free ligands. The 1H NMR also depicted formation of the complexes, with complexes peaks shifting to downfield as compared to the free ligands. There were also signs of broad NH peaks especially for substituted thiourea complexes. The crystals grown from complex II (diphenylthiourea cadmium complex) depicted a tetrahedral geometry, with two sulphur and two chlorine atoms binding to the central atom which is cadmium. The easily synthesized complexes were thermolysed in HDA, TOPO or a mixture of the two to form metal sulphide nanoparticles. The role of the above capping agents or ligands was to control particles growth and prevent them from aggregation. A single source precursor route was employed in synthesizing hydrophobic semiconductor nanoparticles, which are also known as (QDs) quantum dots. Various shapes, which are rods (mono-, bi- and tripods), spheres and hexagonal were revealed through transmission electron microscope (TEM). The sizes of these particles ranged from 1 to 12 nm in diameter. Other instruments used for characterising the as-synthesized semiconductor nanoparticles include X-ray diffractometer (XRD), UV-Visible and Photoluminescence spectroscopy. The optical properties of the particles as determined by the UV-Visible spectroscopy revealed some differences as compared to the bulk materials. All the absorption spectra were blue shifted to the bulk materials signifying finite size of the particles. The XRD peaks observed were broad as compared to the bulk ones, which also signified small particles size. Two phases, which are hexagonal and cubic, were revealed from the XRD. viii The hydrophobic semiconductor nanoparticles or quantum dots synthesized were then transferred into water soluble using ligand exchange method. The chloroform and pyridine routes were used to synthesize hydrophilic semiconductor nanoparticles, with pyridine route being preferred. The shape and size of the particles were not influenced by the transfer into water soluble since the experiments were performed at room temperature. This was confirmed by TEM analysis. The capping agents used after displacing water insoluble capping agents were sugars, which were soluble in water. The XRD pattern of the semiconductor nanoparticles/QDs (CdS) capped by sugars after ligand exchange through pyridine yielded multiple peaks which were difficult to assign. The attempt to employ ligand exchange method in transferring hydrophobic CoxSy and ZnS nanoparticles to hydrophilic CoxSy and ZnS nanoparticles proved unsuccessful. When the materials were centrifuged after the sugars were introduced as capping agents, some solid material settled at the bottom, with some floating on top of the solution. This was an indication that the materials were not miscible. The hydrophilic CdS, CoxSy and ZnS nanoparticles were also synthesized using direct method. In this method, the metal sources and capping (sugars) were dissolved in ethylene glycol at 100 oC. The sulphur sources were also dissolved separately in the same solvent. Upon completion, the latter solution was added to the former one. The particles were grown at 160 oC for an hour with ethylene glycol as a solvent. The morphology of the particles dominated through this method was spherical-like in shape. The crystallinity of CdS and ZnS nanoparticles depicted hexagonal and cubic phases depending on the complexes used. The XRD indicated the armophous nature of the cobalt sulphide nanoparticles, irrespective of the precursor used. Due to the toxicity problem of the quantum dots, especially CdS, the water soluble CdS capped by glucuronic acid, glucose and sucrose after ligand exchange were chosen for that study. However, results showed that the CdS used were not toxic. It was measured or deduced by checking the viability which remained above 90%. Add a bit of deductions about toxicity study here, just some of the general trends.

Neste trabalho foram estudados os fenômenos fotoinduzidos apresentados pelos vidros calcogenetos de composições: Ga IND.10Ge IND.25S IND.65 e Ga IND.5Ge IND.25As IND.5S IND.65. Estes vidros ao serem iluminados com luz que possui energia próxima a do bandgap apresentam vários fenômenos fotoinduzidos. Sendo assim um estudo sistemático em função da potência, tempo de iluminação e do comprimento de onda foi efetuado. Para energias acima da banda proibida ocorre a fotoexpansão, variação do índice de refração e fotoclareamento. Por outro lado, para energias abaixo da banda proibida não foi observada nenhuma variação do volume; no entanto foi detectado um fotoescurecimento. Estes fenômenos mostraram ser irreversíveis, visto que ao serem levados a tratamento térmico a temperatura próxima a temperatura de transição vítrea, os vidros não recuperaram sua forma original. Várias técnicas experimentais foram usadas tais como: microscopia de força atômica, perfilometria, espectro de absorção óptica, espectroscopia na região do infravermelho, espalhamento Raman, EDX, EXAFS e RBS para caracterização dos fenômenos fotoinduzidos e elucidar o mecanismo envolvido. Os resultados obtidos a partir de EXAFS, Infravermelho, RBS e EDX indicaram a incorporação de oxigênio na superfície dos vidros quebrando assim as ligações Ge-S. Foi observado que a magnitude da fotoexpansão depende da atmosfera usada durante a irradiação. Um estudo comparativo entre o vidro e o filme depositado foi realizado. Foi mostrado através de espalhamento Raman e Infravermelho que os tipos de ligações presente no filme depositado é diferente daquela do vidro original. Os mesmos fenômenos fotoinduzidos foram também detectados nos filmes depositados, os quais foram estudados e caracterizados também de maneira sistemática. Como aplicação destes fenômenos fotoinduzidos, a fotoexpansão foi usada para a produção de redes de difração. ) As medidas de eficiência de difração e as imagens de microscopia de força atômica demonstraram que a fotoexpansão cria uma rede de relevo na superfície do vidro / We report the photoinduced phenomena observed in two chalcogenide glass compositions: Ga IOGe2SS6eSGasGe2sAssS6s. These glasses present several photoinduced phenomena when exposed to light having energy comparable to bandgap energy. Systematic study has been carried out in function of power density, exposure time and wavelength. Samples exposed to energy above the bandgap the photoexpansion, photorefraction and photobleaching has been observed. Otherwise, to energy below the bandgap a photodarkening was detected without volume variation. These phenomena are irreversible since the surface does not restore the original structure when annealing to the glass transition temperature. To Characterize and understand the mechanism processes of the photoexpansíon effect, atomíc force mícroscopy, perfilometry, absorption spectra, ínfrared absorption, Raman, EDX, EXAFS and RBS has been used before and after illumination of the glass samples. The EXAFS, infrared, RBS and EDX data showed that íllumínatíon leads to an introduction of oxygen ín the glass structure breaking Ge-S intermolecular bonds followed by the formatíon of Ge-O bonds. We observed that the magnitude of the photoínduced expansíon of the GaGeS glass ís strongly dependent on the atmosphere used. Comparative study has been performed between glass and filmo Infrared and Raman data shown a different bonding behavior ín the film prepared prevíously from the glass. Under irradíation, the same photoínduced phenomenon already detected on the glass samples are observed on the thin film and also characterized systematically. As applícation of the photoinduced phenomenon, photoexpansíon effect has been used to produce díffraction gratíngs. Atomic mícroscopy images and diffractíon efficiency data indícate that photoexpansíon leads to relíef gratíng on the glass surface

This thesis ‘’An Investigation of Tin Chalcogenide Precursors and Thin Film Materials for Applications in Energy Harvesting Devices’’ encompasses a range of research areas. The report can be divided into two categories: The first is the design of novel heavy tin chalcogenide complexes and compounds that demonstrate the recent advances in main group chemistry and act as potential precursor candidates for CVD processes. The second category follows on from the previous, and focuses on materials deposited and their successive development, characterisation and optimisation for device applications. Subsequently, an array of metal chalcogenide thin films have been deposited and characterised within this project. By designing of a number of the tin chalcogenide precursors and precursor solutions it has been possible to selectively deposit thin films of Sn, α-SnS and cubic-SnS polymorphs, SnS2, SnSe, and SnTe via a low-cost deposition route known as aerosol assisted chemical vapour deposition (AA-CVD). It is proposed that the processes developed in this PhD can be adapted to deposit a wider spectrum of metal chalcogenide materials using cost effective techniques. Even though there is a wide scope of the possible applications for the aforementioned materials, the study has only been extended towards the characterisation of the optoelectronic properties of phase pure α-SnS and cubic-SnS samples, and SnS2 thin films deposited onto FTO, Mo and graphene substrates. The optimum deposition parameters for the application of these materials has been defined. In collaboration with a research group at the Institut de Recerca de Energia de Catalunya (iREC), Barcelona, Spain, an extended study of the photovoltaic properties of the α-SnS and Cubic-SnS samples is also presented, from which a series of SnS based thin film photovoltaic devices have been fabricated and characterised. This study present some of the few reports explicitly comparing the PV properties of the two α-SnS and Cubic-SnS polymorphs.

The aim of this study was to evaluate the quality of the groundwater around the Aitik copper mine- one of Europe’s largest copper mine located 15 km outside of Gällivare, Sweden - as well the placement of the groundwater pipes around the area. The study also included a survey of what kind of terms, regarding groundwater that may become relevant in the future for an activity of Aitik’s size and type. Monitoring data was analysed between the years 2014 – 2018 for the parameters; pH, SO4, Cd, Co, Cu, Zn, Ni and U. The correlation between the parameters where tested and the monitoring data where compared to the Swedish Environmental Protection Agency criteria for groundwater as well to the groundwater chemistry from a reference area nearby, Liikavaara Östra. The result of the study shows that low pH raises the mobility of the metals Cd, Co, Cu, Zn and Ni. The result also indicates that SO4, Ni and Co are higher than the reference area but that the groundwater overall shows small signs of being affected by sulphide weathering. Therefore, metals can’t be excluded from originating from high background contents. The geographic analyse shows that the groundwater pipes are well placed in compared with the water flow direction and that two of the pipes can be excluded from sampling. Future terms regarding groundwater will likely regard protective measures and quantity restrictions. Still monitoring groundwater quality is very important to control environmental impact of the activity and to prevent deterioration of quality in the future.

O H2S é um gás que causa preocupação devido aos efeitos que pode provocar a saúde, a corrosão sobre alguns materiais e a redução do poder calorífero no aproveitamento de biogás, mesmo quando presente em baixas concentrações. O uso de biogás como fonte energética tem crescido nos últimos anos, impulsionando a remoção do sulfeto de hidrogênio, uma vez que a presença de tal gás reduz a capacidade calorífica do biogás e causa danos às instalações. Diante disso, várias técnicas são utilizadas na remoção de H2S, sendo uma delas, a adsorção. Os processos de separação por adsorção são muito utilizados para a remoção de poluentes gasosos de misturas gasosas. Neste trabalho foram realizados experimentos da adsorção do H2S sobre lodo seco, em coluna de leito fixo, para obtenção da capacidade de adsorção dinâmica do lodo e como esta seria afetada pelas variáveis de processo: concentração de alimentação e vazão de alimentação. Para tanto, foi concebida e instalada uma unidade de bancada de adsorção em leito fixo, com facilidades experimentais necessárias para testes dinâmicos, com o emprego da técnica de interpretação de curvas de efluência, um método útil para a avaliação do desempenho de um adsorvente em colunas de leito fixo. Testes preliminares mostraram que a unidade de bancada apresentou versatilidade, podendo ser operada com vazões de até 5 L/ min e concentração de H2S na mistura gasosa de até 500 ppm. Os resultados obtidos mostraram que a capacidade de adsorção do lodo seco foi muito baixa, com valores variando de 3,30 x 10-5 a 2,54 x 10-3 mg de H2S/g de lodo seco e existência de caminhos preferenciais no leito. / It is widely known that H2S is a gas which causes preoccupation due to the potential risks to health, corrosion in materials and reduction of the calorific value, even when present in low concentrations. The application of biogas as an energetic source has increased in last years, promoting the hydrogen sulphide removal, so that H2S presence can reduce the biogas energetic capacity and cause damage in the installations. Therefore, many techniques are used to H2S removal, one them is adsorption. The adsorption separation processes are widely used in the removal of pollutants gaseous from gas mixtures. In this work, experiments were performed on the adsorption of H2S the dry sludge in a fixed bed column, aiming to obtain the dynamic adsorption capacity and how this would be affected by the process variables: feed concentration and feed flow rate . For that, we designed and installed a bench unit to fixed bed adsorption with necessary experimental facilities for dynamic tests with the use of the technique of interpretation breakthrough curves, an useful method for evaluating the performance of an adsorbent columns fixed bed . Preliminary tests showed that the bench unit has presented versatility and efficiency and it can be operated at flow rates up to 5 L/min and H2S concentration in the gas mixture up to 500 ppm. The results showed that the adsorption capacity of the dried sludge was very low , with values varied from 3.30 × 10-5 to 2.54 × 10-3 mg H2S/g of dry sludge and the existence of preferential paths in the bed .

Thesis (MSc. (Physics)) --University of Limpopo, 2009 / Calculations were carried out on transition-metal sulphides (TMS) and transitionmetal arsenides (TMA), in both pyrite- and marcasite-type structures, using planewave (PW) pseudopotential methods within density functional theory (DFT) in the local density approximation (LDA). The structural, electronic and optical properties for both pyrite- and marcasite-type structures (naturally occurring and converted) have been investigated. The equilibrium lattice parameters were investigated and are in good agreement with the experimental values. The heats of formation calculations predict that the naturally occurring pyrite- and marcasite-type structures are more stable than the converted ones. In particular, the calculated pyrite-type RuS2 compares well to the experimental value (with energy difference of 0.381 eV/atom). The bulk modulus and elastic properties were calculated. The predicted anisotropic ratio shows that the naturally occurring pyrite- and marcasite-type structures are more stable than the converted ones. Moreover, the electronic density of states and band structure calculations reveal that most compositions shows semiconducting behaviour except for the converted pyritetype structures, i.e OsAs2 and RuAs2 where a metallic behaviour was observed. The electronic charge density and charge density difference show charge accumulation on bonding atoms, predicting the charge gain/ loss and nature of bonding to be covalent/ weak ionic between the atoms. Lastly, optical properties are computed at equilibrium and predict that naturally occurring structures have lower absorption and reflectivity than the converted structures. At different pressures ranging from -10 GPa to 10 GPa, the absorption and reflectivity spectra show a shift from the 0 GPa spectrum for all the structures / National Research Foundation

No description available.

This thesis examines the bioleaching of six different Canadian nickel sulphide ores at pH levels above what is generally considered optimum (~ 2). The majority of work discussed in this thesis was conducted with a low-grade metamorphosed ultramafic nickel sulphide ore from Manitoba, Canada (Ore 3), which is not currently exploitable with conventional technologies. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as the serpentine mineral lizardite, making processing difficult with conventional pyro- and biohydrometallurgical techniques. The work with this ore has two equally important objectives: to minimize magnesium mobilization and to obtain an acceptable level of nickel extraction. Batch stirred-tank bioleaching experiments were conducted with finely ground ore ( 147 µm) with temperature and pH control. The first phase of experimentation examined the effect of pH (2 to 6) at 30 °C, and the second phase examined all combinations of three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C).

Most of the city of Uppsala rests on postglacial clay with a varying content of sulphur. The sulphur occurs naturally in the clay in reduced form as sulphide and the clay is for that reason usually called “sulphide clay”. Excavation during construction activities gives rise to large amounts of excavation material, of which the sulphide clay is a considerable part. When the clay is exposed to air and water, an oxidation of the sulphides occurs which may produce an acid leachate and the mobilisation of heavy metals bound in the clay or underlying material. The aim of the work has been to improve our understanding of the behaviour of sulphide clays and produce a basis for risk assessment in the future handling of excavation material with high sulphide content. After sampling had been carried out in two places, batch tests were performed to examine the long-term acidification potential of clays with different calcium carbonate content. The tests were performed with continuous air supply and during the experiment leachate water was analysed with respect to pH, alkalinity, dissolved sulphate and mobilised metals. The results from the laboratory study showed that a clay with a high calcium carbonate content and thus a high net neutralisation potential (NNP) will consume the generated acid and prevent against a lowering of the pH. In clay lacking calcium carbonate, the pH dropped significantly and caused a mobilisation of chiefly Cd, Mn, Co, Ni, Ca and As. Regardless of the changes in pH over time, a large production of sulphur was observed as a result of the sulphide oxidation. In a risk assessment, it is suggested that the NNP should be determined by methods agreed upon to facilitate future comparisons and because different methods may give different results. A clay with a NNP&lt;5 kg CaCO3/ton should be further analysed with respect to metal content to establish the leachate generation potential and estimate the future environmental influence of the excavation material. / Uppsala stad vilar till stor del på postglacial lera med varierande svavelhalt. Svavlet finns naturligt i leran i reducerad form som sulfid och leran kallas därför vanligtvis för ”sulfidlera”. Vid schaktningsarbete i samband med byggnation uppkommer stora mängder schaktmassor varav en betydande del är sulfidlera. Då leran exponeras för luft och nederbörd sker en oxidation av sulfiderna som kan ge upphov till surt lakvatten och läckage av tungmetaller bundna i leran eller underliggande material. Syftet med arbetet har varit att öka kunskaperna om hur sulfidleror beter sig och ta fram ett underlag för riskbedömning i samband med den framtida hanteringen av sulfidhaltiga schaktmassor i Uppsala. Efter genomförd provtagning på två platser utfördes skaktest för att undersöka den långsiktiga försurningspotentialen hos lera med varierande kalkinnehåll. Testerna utfördes med kontinuerlig tillförsel av luft och löpande under försökets gång togs lakvatten ut för analys avseende pH, alkalinitet, löst sulfat och utlakade metaller. Resultaten från den laborativa studien visade att en kalkhaltig lera med hög nettoneutralisationspotential (NNP) kan förbruka den bildade syran och därigenom genereras ingen pH-sänkning. I lera som saknar kalk sjönk pH kraftigt och föranledde läckage av framförallt Cd, Mn, Co, Ni, Ca och As. Oavsett utvecklingen av pH observerades en stor utlakning av svavel till följd av oxidationen av sulfider. I en riskbedömning föreslås att lerans NNP bestäms enligt överenskomna metoder för att underlätta framtida jämförelser och för att olika tekniker kan ge olika resultat. En lera med NNP-värde &lt; 5 kg CaCO3/ton bör analyseras vidare avseende metallinnehåll för att fastställa den potentiella utlakningen och bedöma schaktmassans framtida naturpåverkan.