Gold recovery from cyanideand chloride solution using activated carbon

Uusia keinoja kullan erottamiseksi malmista on etsitty viimeaikoina taloudellisista ja ympäristöllisistä syistä kautta maailman. Syanidointimenetelmä on hallinnut kullan talteenottoayli sata vuotta. Menetelmässä kulta liuotetaan laimeaan syanidiliuokseen, jostase otetaan talteen aktiivihiilen avulla. Syanidin käyttöä pyritään kuitenkin vähentämään sen myrkyllisyyden takia. Lisäksi nykyään louhitaan enenemässä määrin malmia, josta on hankala rikastaa kulta kustannustehokkaasti syanidia käyttäen. Kullan talteenottoa syanidi- ja kloridiliuoksesta on selvitetty kirjallisuuden avulla. Kullan kemiaan liuotuksen aikana on perehdytty ennen kullan talteenottoa aktiivihiilellä. Aktiivihiilen elinkaari kullan adsorbenttinaon käsitelty valmistuksesta hylkäämiseen mukaan lukien hiilen myrkyttyminen prosessissa ja regenerointi. Aktiivi-hiilen käyttäytyminen syanidi- ja kloridiliuoksessa on selvitetty erikseen. Kullan talteenottoa kuparipitoisista malmeista on käsitelty. Kullan talteenottoa kloridiliuoksesta aktiivihiiltä käyttäen on tutkittu kokeellisesti. Pääasialliset tutkimuskohteet ovat adsorption kinetiikka, kuparin vaikutus adsorptioon, aktiivihiilen vaikutus adsorptioonja adsorboituneiden metallien strippaus hiilestä selektiivisesti. Hapettavan stippauksen vaikutus kullan desorptioon hiilestä on tutkittu yksityiskohtaisesti. Kullan erotusmenetelmät kuparimalmista aktiivihiiltä käyttäen on selvitetty diplomityön tulosten pohjalta. Diplomityön keskeisten tulosten perusteella kulta ei välttämättä saostu aktiivihiilen pinnalle kloridiliuoksesta. Havainto varmistettiin ladattujen hiilipartikkelien pyyhkäisyelektronimikroskooppikuvista ja partikkeleille tehdyistä mikroanalyyseistä. Kullan pelkistyminen metalliseksi kullaksi aktiivihiilessä voitaneen välttää käyttämällä erittäin hapettavia olosuhteita. Aktiivihiili ilmeisesti hapettuu näissä olosuhteissa, mikä mahdollistaa kultakloridin adsorboitumisen hiileen.

Investigation of interaction between native and impurity defects in ZnSe

Zinc selenide is a prospective material for optoelectronics. The fabrication of ZnSe­based light-emitting diodes is hindered by complexity of p-type doping of the component materials. The interaction between native and impurity defects, the tendency of doping impurity to form associative centres with native defects and the tendency to self-compensation are the main factors impeding effective control of the value and type of conductivity. The thesis is devoted to the study of the processes of interaction between native and impurity defects in zinc selenide. It is established that the Au impurity has the most prominent amphoteric properties in ZnSe among Cu, Ag and Au impurities, as it forms a great number of both Au; donors and Auz„ acceptors. Electrical measurements show that Ag and Au ions introduced into vacant sites of the Zn sublattice form simple single-charged Agz„+ and Auzn+ states with d1° electron configuration, while Cu ions can form both single-charged Cuz„ (d1) and double-charged Cuzr`+ (d`o) centres. Amphoteric properties of Ag and Au transition metals stimulated by time are found for the first time from both electrical and luminescent measurements. A model that explains the changes in electrical and luminescent parameters by displacement of Ag ions into interstitial sites due to lattice deformation forces is proposed. Formation of an Ag;-donor impurity band in ZnSe samples doped with Ag and stored at room temperature is also studied. Thus, the properties of the doped samples are modified due to large lattice relaxation during aging. This fact should be taken into account in optoelectronic applications of doped ZnSe and related compounds.

Removal of Cadmium, Lead and Arsenic from Water by Lactic Acid Bacteria

A number of contaminants such as arsenic, cadmium and lead are released into the environment from natural and anthropogenic sources contaminating food and water. Chronic oral ingestion of arsenic, cadmium and lead is associated with adverse effects in the skin, internal organs and nervous system. In addition to conventional methods, biosorption using inactivated biomasses of algae, fungi and bacteria has been introduced as a novel method for decontamination of toxic metals from water. The aim of this work was to evaluate the applicability of lactic acid bacteria as tools for heavy metal removal from water and characterize their properties for further development of a biofilter. The results established that in addition to removal of mycotoxins, cyanotoxins and heterocyclic amines, lactic acid bacteria have a capacity to bind cationic heavy metals, cadmium and lead. The binding was found to be dependent on the bacterial strain and pH, and occurred rapidly on the bacterial surface, but was reduced in the presence of other cationic metals. The data demonstrates that the metals were bound by electrostatic interactions to cell wall components. Transmission electron micrographs showed the presence of lead deposits on the surface of biomass used in the lead binding studies, indicating involvement of another uptake/binding mechanism. The most efficient strains bound up to 55 mg Cd and 176 mg Pb / g dry biomass. A low removal of anionic As(V) was also observed after chemical modification of the cell wall. Full desorption of bound cadmium and lead using either dilute HNO₃ or EDTA established the reversibility of binding. Removal of both metals was significantly reduced when biomass regenerated with EDTA was used. Biomass regenerated with dilute HNO3 retained its cadmium binding capacity well, but lead binding was reduced. The results established that the cadmium and lead binding capacity of lactic acid bacteria, and factors affecting it, are similar to what has been previously observed for other biomasses used for the same purpose. However, lactic acid bacteria have a capacity to remove other aqueous contaminants such as cyanotoxins, which may give them an additional advantage over the other alternatives. Further studies focusing on immobilization of biomass and the removal of several contaminants simultaneously using immobilized bacteria are required.

Characterisation of pigment particles by scanning electron microscope and image analysis programs

Coating and filler pigments have strong influence to the properties of the paper. Filler content can be even over 30 % and pigment content in coating is about 85-95 weight percent. The physical and chemical properties of the pigments are different and the knowledge of these properties is important for optimising of optical and printing properties of the paper. The size and shape of pigment particles can be measured by different analysers which can be based on sedimentation, laser diffraction, changes in electric field etc. In this master's thesis was researched particle properties especially by scanning electron microscope (SEM) and image analysis programs. Research included nine pigments with different particle size and shape. Pigments were analysed by two image analysis programs (INCA Feature and Poikki), Coulter LS230 (laser diffraction) and SediGraph 5100 (sedimentation). The results were compared to perceive the effect of particle shape to the performance of the analysers. Only image analysis programs gave parameters of the particle shape. One part of research was also the sample preparation for SEM. Individual particles should be separated and distinct in ideal sample. Analysing methods gave different results but results from image analysis programs corresponded even to sedimentation or to laser diffraction depending on the particle shape. Detailed analysis of the particle shape required high magnification in SEM, but measured parameters described very well the shape of the particles. Large particles (ecd~1 µm) could be used also in 3D-modelling which enabled the measurement of the thickness of the particles. Scanning electron microscope and image analysis programs were effective and multifunctional tools for particle analyses. Development and experience will devise the usability of analysing method in routine use.

Studies of Eu- and Yb-induced Reconstructions on the Si(100) Surface

This thesis presents experimental studies of rare earth (RE) metal induced structures on Si(100) surfaces. Two divalent RE metal adsorbates, Eu and Yb, are investigated on nominally flat Si(100) and on vicinal, stepped Si(100) substrates. Several experimental methods have been applied, including scanning tunneling microscopy/spectroscopy (STM/STS), low energy electron diffraction (LEED), synchrotron radiation photoelectron spectroscopy (SR-PES), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS), and work function change measurements (Δφ). Two stages can be distinguished in the initial growth of the RE/Si interface: the formation of a two-dimensional (2D) adsorbed layer at submonolayer coverage and the growth of a three-dimensional (3D) silicide phase at higher coverage. The 2D phase is studied for both adsorbates in order to discover whether they produce common reconstructions or reconstructions common to the other RE metals. For studies of the 3D phase Yb is chosen due to its ability to crystallize in a hexagonal AlB2 type lattice, which is the structure of RE silicide nanowires, therefore allowing for the possibility of the growth of one-dimensional (1D) wires. It is found that despite their similar electronic configuration, Eu and Yb do not form similar 2D reconstructions on Si(100). Instead, a wealth of 2D structures is observed and atomic models are proposed for the 2×3-type reconstructions. In addition, adsorbate induced modifications on surface morphology and orientational symmetry are observed. The formation of the Yb silicide phase follows the Stranski-Krastanov growth mode. Nanowires with the hexagonal lattice are observed on the flat Si(100) substrate, and moreover, an unexpectedly large variety of growth directions are revealed. On the vicinal substrate the growth of the silicide phase as 3D islands and wires depends drastically on the growth conditions. The conditions under which wires with high aspect ratio and single orientation parallel to the step edges can be formed are demonstrated.

Tautomerism and Fragmentation of Biologically Active Hetero Atom (O, N)-Containing Acyclic and Cyclic Compounds Under Electron Ionization

In this thesis a total of 86 compounds containing the hetero atoms oxygen and nitrogen were studied under electron ionization mass spectrometry (EIMS). These compounds are biologically active and were synthesized by various research groups. The main attention of this study was paid on the fragmentations related to different tautomeric forms of 2- phenacylpyridines, 2-phenacylquinolines, 8-aryl-3,4-dioxo-2H,8H-6,7-dihydroimidazo- [2,1-c][1,2,4]triazines and aryl- and benzyl-substituted 2,3-dihydroimidazo[1,2-a]pyrimidine-5,7-(1H,6H)-diones. Also regio/stereospecific effects on fragmentations of pyrrolo- and isoindoloquinazolinones and naphthoxazine, naphthpyrrolo-oxazinone and naphthoxazino-benzoxazine derivatives were screened. Results were compared with NMR data, when available. The first part of thesis consists of theory and literature review of different types of tautomerism and fragmentation mechanisms in EIMS. The effects of tautomerism in biological systems are also briefly reviewed. In the second part of the thesis the own results of the author, based on six publications,are discussed. For 2-phenacylpyridines and 2-phenacylquinolines the correlation of different Hammett substituent constants to the relative abundances (RA) or total ion currents (% TIC) of selected ions were investigated. Although it was not possible to assign most of the ions formed unambiguously to the different tautomers, the linear fits of their RAs and % TICs can be related to changing contributions of different tautomeric forms. For dioxoimidazotriazines and imidazopyrimidinediones the effects of substituents were rather weak. The fragmentations were also found useful for obtaining structural information. Some stereoisomeric pairs of pyrrolo- and isoindoloquinazolines and regiomeric pairs of naphtoxazine derivatives showed clear differences in thir mass spectra. Some mechanisms are suggested for their fragmentations.

Electric field calibration method for scanning electron microscope

This paper proposes a calibration method which can be utilized for the analysis of SEM images. The field of application of the developed method is a calculation of surface potential distribution of biased silicon edgeless detector. The suggested processing of the data collected by SEM consists of several stages and takes into account different aspects affecting the SEM image. The calibration method doesn’t pretend to be precise but at the same time it gives the basics of potential distribution when the different biasing voltages applied to the detector.

Electric field measurements using scanning electron microscope

The main idea of this diploma work is to study electric field distribution on the micro level. For this purpose a silicon edgeless detector was chosen as the object of investigation and scanning electron microscope as an investigation tool. Silicon edgeless detector is an important part of installation for studying proton-proton interactions in TOTEM experiment at Large Hadron Collider. For measurement of electric field distribution inside scanning electron microscope a voltage contrast method was applied.

Leaf-Targeted Ferredoxin-NADP+-Oxidoreductase (FNR): Electron Transfer Properties and Thylakoid Association in Arabidopsis thaliana

Photosynthetic reactions are divided in two parts: light-driven electron transfer reactions and carbon fixation reactions. Electron transfer reactions capture solar energy and split water molecules to form reducing energy (NADPH) and energy-carrying molecules (ATP). These end-products are used for fixation of inorganic carbon dioxide into organic sugar molecules. Ferredoxin-NADP⁺ oxidoreductase (FNR) is an enzyme that acts at the branch point between the electron transfer reactions and reductive metabolism by catalyzing reduction of NADP+ at the last step of the electron transfer chain. In this thesis, two isoforms of FNR from A rabidopsis thaliana, FNR1 and FNR2, were characterized using the reverse genetics approach. The fnr1 and fnr2 mutant plants resembled each other in many respects. Downregulation of photosynthesis protected the single fnr mutant plants from excess formation of reactive oxygen species (ROS), even without significant upregulation of antioxidative mechanisms. Adverse growth conditions, however, resulted in phenotypic differences between fnr1 and fnr2. While fnr2 plants showed downregulation of photosynthetic complexes and upregulation of antioxidative mechanisms under low-temperature growth conditions, fnr1 plants had the wild-type phenotype, indicating that FNR2 may have a specific role in redistribution of electrons under unfavorable conditions. The heterozygotic double mutant (fnr1xfnr2) was severely devoid of chloroplastic FNR, which clearly restricted photosynthesis. The fnr1xfnr2 plants used several photoprotective mechanisms to avoid oxidative stress. In wild-type chloroplasts, both FNR isoforms were found from the stroma, the thylakoid membrane, and the inner envelope membrane. In the absence of the FNR1 isoform, FNR2 was found only in the stroma, suggesting that FNR1 and FNR2 form a dimer, by which FNR1 anchors FNR2 to the thylakoid membrane. Structural modeling predicted formation of an FNR dimer in complex with ferredoxin. In this thesis work, Tic62 was found to be the main protein that binds FNR to the thylakoid membrane, where Tic62 and FNR formed high molecular weight complexes. The formation of such complexes was shown to be regulated by the redox state of the chloroplast. The accumulation of Tic62-FNR complexes in darkness and dissociation of complexes from the membranes in light provide evidence that the complexes may have roles unrelated to photosynthesis. This and the high viability of fnr1 mutant plants lacking thylakoid-bound FNR indicate that the stromal pool of FNR is photosynthetically active.

Charge transport in disordered materials : simulations, theory, and numerical modeling of hopping transport and electron-hole recombination

Min avhandling behandlar hur oordnade material leder elektrisk ström. Bland materialen som studeras finns ledande polymerer, d.v.s. plaster som leder ström, och mer allmänt organiska halvledare. Av de här materialen har man kunnat bygga elektroniska komponenter, och man hoppas på att kunna trycka hela kretsar av organiska material. För de här tillämpningarna är det viktigt att förstå hur materialen själva leder elektrisk ström. Termen oordnade material syftar på material som saknar kristallstruktur. Oordningen gör att elektronernas tillstånd blir lokaliserade i rummet, så att en elektron i ett visst tillstånd är begränsad t.ex. till en molekyl eller ett segment av en polymer. Det här kan jämföras med kristallina material, där ett elektrontillstånd är utspritt över hela kristallen (men i stället har en väldefinierad rörelsemängd). Elektronerna (eller hålen) i det oordnade materialet kan röra sig genom att tunnelera mellan de lokaliserade tillstånden. Utgående från egenskaperna för den här tunneleringsprocessen, kan man bestämma transportegenskaperna för hela materialet. Det här är utgångspunkten för den så kallade hopptransportmodellen, som jag har använt mig av. Hopptransportmodellen innehåller flera drastiska förenklingar. Till exempel betraktas elektrontillstånden som punktformiga, så att tunneleringssannolikheten mellan två tillstånd endast beror på avståndet mellan dem, och inte på deras relativa orientation. En annan förenkling är att behandla det kvantmekaniska tunneleringsproblemet som en klassisk process, en slumpvandring. Trots de här grova approximationerna visar hopptransportmodellen ändå många av de fenomen som uppträder i de verkliga materialen som man vill modellera. Man kan kanske säga att hopptransportmodellen är den enklaste modell för oordnade material som fortfarande är intressant att studera. Man har inte hittat exakta analytiska lösningar för hopptransportmodellen, därför använder man approximationer och numeriska metoder, ofta i form av datorberäkningar. Vi har använt både analytiska metoder och numeriska beräkningar för att studera olika aspekter av hopptransportmodellen. En viktig del av artiklarna som min avhandling baserar sig på är att jämföra analytiska och numeriska resultat. Min andel av arbetet har främst varit att utveckla de numeriska metoderna och applicera dem på hopptransportmodellen. Därför fokuserar jag på den här delen av arbetet i avhandlingens introduktionsdel. Ett sätt att studera hopptransportmodellen numeriskt är att direkt utföra en slumpvandringsprocess med ett datorprogram. Genom att föra statisik över slumpvandringen kan man beräkna olika transportegenskaper i modellen. Det här är en så kallad Monte Carlo-metod, eftersom själva beräkningen är en slumpmässig process. I stället för att följa rörelsebanan för enskilda elektroner, kan man beräkna sannolikheten vid jämvikt för att hitta en elektron i olika tillstånd. Man ställer upp ett system av ekvationer, som relaterar sannolikheterna för att hitta elektronen i olika tillstånd i systemet med flödet, strömmen, mellan de olika tillstånden. Genom att lösa ekvationssystemet fås sannolikhetsfördelningen för elektronerna. Från sannolikhetsfördelningen kan sedan strömmen och materialets transportegenskaper beräknas. En aspekt av hopptransportmodellen som vi studerat är elektronernas diffusion, d.v.s. deras slumpmässiga rörelse. Om man betraktar en samling elektroner, så sprider den med tiden ut sig över ett större område. Det är känt att diffusionshastigheten beror av elfältet, så att elektronerna sprider sig fortare om de påverkas av ett elektriskt fält. Vi har undersökt den här processen, och visat att beteendet är väldigt olika i endimensionella system, jämfört med två- och tredimensionella. I två och tre dimensioner beror diffusionskoefficienten kvadratiskt av elfältet, medan beroendet i en dimension är linjärt. En annan aspekt vi studerat är negativ differentiell konduktivitet, d.v.s. att strömmen i ett material minskar då man ökar spänningen över det. Eftersom det här fenomenet har uppmätts i organiska minnesceller, ville vi undersöka om fenomenet också kan uppstå i hopptransportmodellen. Det visade sig att det i modellen finns två olika mekanismer som kan ge upphov till negativ differentiell konduktivitet. Dels kan elektronerna fastna i fällor, återvändsgränder i systemet, som är sådana att det är svårare att ta sig ur dem då elfältet är stort. Då kan elektronernas medelhastighet och därmed strömmen i materialet minska med ökande elfält. Elektrisk växelverkan mellan elektronerna kan också leda till samma beteende, genom en så kallad coulombblockad. En coulombblockad kan uppstå om antalet ledningselektroner i materialet ökar med ökande spänning. Elektronerna repellerar varandra och ett större antal elektroner kan leda till att transporten blir långsammare, d.v.s. att strömmen minskar.

Readout Electronics for Gas Electron Multiplier Detectors

The European Organization for Nuclear Research (CERN) operates the largest particle collider in the world. This particle collider is called the Large Hadron Collider (LHC) and it will undergo a maintenance break sometime in 2017 or 2018. During the break, the particle detectors, which operate around the particle collider, will be serviced and upgraded. Following the improvement in performance of the particle collider, the requirements for the detector electronics will be more demanding. In particular, the high amount of radiation during the operation of the particle collider sets requirements for the electronics that are uncommon in commercial electronics. Electronics that are built to function in the challenging environment of the collider have been designed at CERN. In order to meet the future challenges of data transmission, a GigaBit Transceiver data transmission module and an E-Link data bus have been developed. The next generation of readout electronics is designed to benefit from these technologies. However, the current readout electronics chips are not compatible with these technologies. As a result, in addition to new Gas Electron Multiplier (GEM) detectors and other technology, a new compatible chip is developed to function within the GEMs for the Compact Muon Solenoid (CMS) project. In this thesis, the objective was to study a data transmission interface that will be located on the readout chip between the E-Link bus and the control logic of the chip. The function of the module is to handle data transmission between the chip and the E-Link. In the study, a model of the interface was implemented with the Verilog hardware description language. This process was simulated by using chip design software by Cadence. State machines and operating principles with alternative possibilities for implementation are introduced in the E-Link interface design procedure. The functionality of the designed logic is demonstrated in simulation results, in which the implemented model is proven to be suitable for its task. Finally, suggestions that should be considered for improving the design have been presented.

Regulation of photosynthetic electron transfer in plant chloroplasts

This thesis focuses on the molecular mechanisms regulating the photosynthetic electron transfer reactions upon changes in light intensity. To investigate these mechanisms, I used mutants of the model plant Arabidopsis thaliana impaired in various aspects of regulation of the photosynthetic light reactions. These included mutants of photosystem II (PSII) and light harvesting complex II (LHCII) phosphorylation (stn7 and stn8), mutants of energy-dependent non-photochemical quenching (NPQ) (npq1 and npq4) and of regulation of photosynthetic electron transfer (pgr5). All of these processes have been extensively investigated during the past decades, mainly on plants growing under steady-state conditions, and therefore many aspects of acclimation processes may have been neglected. In this study, plants were grown under fluctuating light, i.e. the alternation of low and high intensities of light, in order to maximally challenge the photosynthetic regulatory mechanisms. In pgr5 and stn7 mutants, the growth in fluctuating light condition mainly damaged PSI while PSII was rather unaffected. It is shown that the PGR5 protein regulates the linear electron transfer: it is essential for the induction of transthylakoid ΔpH that, in turn, activates energy-dependent NPQ and downregulates the activity of cytochrome b6f. This regulation was shown to be essential for the photoprotection of PSI under fluctuations in light intensity. The stn7 mutants were able to acclimate under constant growth light conditions by modulating the PSII/PSI ratio, while under fluctuating growth light they failed in implementing this acclimation strategy. LHCII phosphorylation ensures the balance of the excitation energy distribution between PSII and PSI by increasing the probability for excitons to be trapped by PSI. LHCII can be phosphorylated over all of the thylakoid membrane (grana cores as well as stroma lamellae) and when phosphorylated it constitutes a common antenna for PSII and PSI. Moreover, LHCII was shown to work as a functional bridge that allows the energy transfer between PSII units in grana cores and between PSII and PSI centers in grana margins. Consequently, PSI can function as a quencher of excitation energy. Eventually, the LHCII phosphorylation, NPQ and the photosynthetic control of linear electron transfer via cytochrome b6f work in concert to maintain the redox poise of the electron transfer chain. This is a prerequisite for successful plant growth upon changing natural light conditions, both in short- and long-term.

Modeling Front End Electronics for a Gas Electron Multiplier Detector

The Large Hadron Collider (LHC) in The European Organization for Nuclear Research (CERN) will have a Long Shutdown sometime during 2017 or 2018. During this time there will be maintenance and a possibility to install new detectors. After the shutdown the LHC will have a higher luminosity. A promising new type of detector for this high luminosity phase is a Triple-GEM detector. During the shutdown these detectors will be installed at the Compact Muon Solenoid (CMS) experiment. The Triple-GEM detectors are now being developed at CERN and alongside also a readout ASIC chip for the detector. In this thesis a simulation model was developed for the ASICs analog front end. The model will help to carry out more extensive simulations and also simulate the whole chip before the whole design is finished. The proper functioning of the model was tested with simulations, which are also presented in the thesis.

Inverting ionospheric D-region electron density pro-file from riometer measurement

The aim of this work is to invert the ionospheric electron density profile from Riometer (Relative Ionospheric opacity meter) measurement. The newly Riometer instrument KAIRA (Kilpisjärvi Atmospheric Imaging Receiver Array) is used to measure the cosmic HF radio noise absorption that taking place in the D-region ionosphere between 50 to 90 km. In order to invert the electron density profile synthetic data is used to feed the unknown parameter Neq using spline height method, which works by taking electron density profile at different altitude. Moreover, smoothing prior method also used to sample from the posterior distribution by truncating the prior covariance matrix. The smoothing profile approach makes the problem easier to find the posterior using MCMC (Markov Chain Monte Carlo) method.