Active sulphide mine tailings impoundments as sources of contaminated drainage: controlling factors, methods of characterisation and geochemical constraints for mitigation

Low quality mine drainage from tailings facilities persists as one of the most significant global environmental concerns related to sulphide mining. Due to the large variation in geological and environmental conditions at mine sites, universal approaches to the management of mine drainage are not always applicable. Instead, site-specific knowledge of the geochemical behaviour of waste materials is required for the design and closure of the facilities. In this thesis, tailings-derived water contamination and factors causing the pollution were investigated in two coeval active sulphide mine sites in Finland: the Hitura Ni mine and the Luikonlahti Cu-Zn-Co-Ni mine and talc processing plant. A hydrogeochemical study was performed to characterise the tailingsderived water pollution at Hitura. Geochemical changes in the Hitura tailings were evaluated with a detailed mineralogical and geochemical investigation (solid-phase speciation, acid mine drainage potential, pore water chemistry) and using a spatial assessment to identify the mechanisms of water contamination. A similar spatial investigation, applying selective extractions, was carried out in the Luikonlahti tailings area for comparative purposes (Hitura low-sulphide tailings vs. Luikonlahti sulphide-rich tailings). At both sites, hydrogeochemistry of tailings seepage waters was further characterised to examine the net results of the processes observed within the impoundments and to identify constraints for water treatment. At Luikonlahti, annual and seasonal variation in effluent quality was evaluated based on a four-year monitoring period. Observations pertinent to future assessment and mine drainage prevention from existing and future tailings facilities were presented based on the results. A combination of hydrogeochemical approaches provided a means to delineate the tailings-derived neutral mine drainage at Hitura. Tailings effluents with elevated Ni, SO₄ ^2- and Fe content had dispersed to the surrounding aquifer through a levelled-out esker and underneath the seepage collection ditches. In future mines, this could be avoided with additional basal liners in tailings impoundments where the permeability of the underlying Quaternary deposits is inadequate, and with sufficiently deep ditches. Based on the studies, extensive sulphide oxidation with subsequent metal release may already initiate during active tailings disposal. The intensity and onset of oxidation depended on e.g. the Fe sulphide content of the tailings, water saturation level, and time of exposure of fresh sulphide grains. Continuous disposal decreased sulphide weathering in the surface of low-sulphide tailings, but oxidation initiated if they were left uncovered after disposal ceased. In the sulphide-rich tailings, delayed burial of the unsaturated tailings had resulted in thick oxidized layers, despite the continuous operation. Sulphide weathering and contaminant release occurred also in the border zones. Based on the results, the prevention of sulphide oxidation should already be considered in the planning of tailings disposal, taking into account the border zones. Moreover, even lowsulphide tailings should be covered without delay after active disposal ceases. The quality of tailings effluents showed wide variation within a single impoundment and between the two different types of tailings facilities assessed. The affecting factors included source materials, the intensity of weathering of tailings and embankment materials along the seepage flow path, inputs from the process waters, the water retention time in tailings, and climatic seasonality. In addition, modifications to the tailings impoundment may markedly change the effluent quality. The wide variation in the tailings effluent quality poses challenges for treatment design. The final decision on water management requires quantification of the spatial and seasonal fluctuation at the site, taking into account changes resulting from the eventual closure of the impoundment. Overall, comprehensive hydrogeochemical mapping was deemed essential in the identification of critical contaminants and their sources at mine sites. Mineralogical analysis, selective extractions, and pore water analysis were a good combination of methods for studying the weathering of tailings and in evaluating metal mobility from the facilities. Selective extractions with visual observations and pH measurements of tailings solids were, nevertheless, adequate in describing the spatial distribution of sulphide oxidation in tailings impoundments. Seepage water chemistry provided additional data on geochemical processes in tailings and was necessary for defining constraints for water treatment.

Counter-current Washing of Filter Cakes

The main objective of this thesis was to compare the efficiency of counter-current and co-current filter cake washing techniques. Filter cake washing is a common unit operation which is used in the chemical process industry for improving the recovery of the liquid phase or for purifying the solid phase of the filter cake. Counter-current displacement washing is more difficult to arrange and it requires additional process equipment but the advantage of counter-current method is that the consumption of wash water that is required for achieving certain filter cake purity may be considerably decreased when compared to the co-current washing method. This is true especially for materials that are difficult to wash. The literature part of this thesis consists of a review of filter cake washing in general, including the basic principles of co-current and counter-current techniques, and a description of the structure and operation of a horizontal vacuum belt filter, which is the equipment considered in the experimental part of this thesis. Also the most common cake washing models are introduced. The experiments were performed by washing wheat apatite filter cakes in a laboratory scale vacuum filter by using both co-current and counter-current washing methods. The main results of these tests were the washing curves that relate the purity of the filter cake to the amount of wash liquid used. Comparison between the obtained washing curves showed that both washing methods could be efficiently applied for achieving good washing results. The differences between the wash liquid consumptions in the co-current and counter-current washing methods were found to be surprisingly small but this is most probably explained by the relatively good washing characteristics of the apatite cakes. The washing models introduced in the literature part were compared with the results obtained from the experiments and it was found out that the studied cake washing processes could be described

Detection of Illicit Drugs and Drug Precursors with Cantilever-Enhanced Photoacoustic Spectroscopy

In this study, cantilever-enhanced photoacoustic spectroscopy (CEPAS) was applied in different drug detection schemes. The study was divided into two different applications: trace detection of vaporized drugs and drug precursors in the gas-phase, and detection of cocaine abuse in hair. The main focus, however, was the study of hair samples. In the gas-phase, methyl benzoate, a hydrolysis product of cocaine hydrochloride, and benzyl methyl ketone (BMK), a precursor of amphetamine and methamphetamine were investigated. In the solid-phase, hair samples from cocaine overdose patients were measured and compared to a drug-free reference group. As hair consists mostly of long fibrous proteins generally called keratin, proteins from fingernails and saliva were also studied for comparison. Different measurement setups were applied in this study. Gas measurements were carried out using quantum cascade lasers (QLC) as a source in the photoacoustic detection. Also, an external cavity (EC) design was used for a broader tuning range. Detection limits of 3.4 particles per billion (ppb) for methyl benzoate and 26 ppb for BMK in 0.9 s were achieved with the EC-QCL PAS setup. The achieved detection limits are sufficient for realistic drug detection applications. The measurements from drug overdose patients were carried out using Fourier transform infrared (FTIR) PAS. The drug-containing hair samples and drug-free samples were both measured with the FTIR-PAS setup, and the measured spectra were analyzed statistically with principal component analysis (PCA). The two groups were separated by their spectra with PCA and proper spectral pre-processing. To improve the method, ECQCL measurements of the hair samples, and studies using photoacoustic microsampling techniques, were performed. High quality, high-resolution spectra with a broad tuning range were recorded from a single hair fiber. This broad tuning range of an EC-QCL has not previously been used in the photoacoustic spectroscopy of solids. However, no drug detection studies were performed with the EC-QCL solid-phase setup.

Entsyymien talteenotto ja kierrätys selluloosaetanolin valmistuksessa

Bioetanolin valmistus selluloosapitoisista raaka-aineista vaatii selluloosapolymeerien pilkkomisen liukoisiksi sokereiksi. Tämä voidaan toteuttaa entsymaattisella hydrolyysillä. Selluloosan pilkkomiseen tarkoitetut entsyymit, sellulaasit, ovat entsymaattisen hydrolyysin jälkeen sitoutuneet joko kiintoainefaasiin tai ovat nestemäisessä faasissa ns. vapaina entsyymeinä. Prosessin taloudellisuuden kannalta on erityisen tärkeää minimoida siinä käytettävien entsyymien tarve, sillä tehokkaat entsyymivalmisteet ovat suhteellisen kalliita. Yksi varteenotettava vaihtoehto bioetanoliprosessin saamiseksi taloudellisemmaksi on käytettyjen entsyymien talteenotto ja kierrätys. Työn tarkoituksena oli selvittää kirjallisuudesta, millaisia menetelmiä on kehitetty entsyymien talteenottoon ja kierrätykseen lignoselluloosasta valmistettavan bioetanolin valmistuksessa. Työssä on keskitytty tuoreisiin tutkimuksiin ja menetelmien käyttökelpoisuuteen ja taloudellisuuteen. Viime vuosina sellulaasien talteenotto- ja kierrätysmenetelmiä koskevat tutkimukset ovat keskittyneet pääasiassa käsittelemään nanopartikkelien avulla tapahtuvaa entsyymien immobilisointia, ultrasuodatusta, erilaisia desorptiomenetelmiä, kiinteän hydrolyysijäännöksen kierrättämistä, tuoreen substraatin lisäämistä sekä myös tislausvaiheen jälkeistä entsyymien kierrättämistä. Jotta kierrätysmenetelmä olisi tehokas, tulisi sen pyrkiä säilyttämään entsyymien aktiivisuuksia, sokerisaantoa menettämättä ja sisältää sekä neste-, että kiintoainefaasista tapahtuva kierrätys. Jokaisella kierrätysmenetelmällä on hyvät ja huonot puolensa. Entsyymien talteenottoastetta saadaan kuitenkin parannettua yhdistämällä erilaisia menetelmiä. Useista tutkimuksista huolimatta, taloudellisinta ja käyttökelpoisinta entsyymien talteenotto- ja kierrätysmenetelmää ei ole vielä saavutettu.

Synthesis of Short Oligonucleotides on a Soluble Support by the Phosphoramidite Method

In the last decades, the chemical synthesis of short oligonucleotides has become an important aspect of study due to the discovery of new functions for nucleic acids such as antisense oligonucleotides (ASOs), aptamers, DNAzymes, microRNA (miRNA) and small interfering RNA (siRNA). The applications in modern therapies and fundamental medicine on the treatment of different cancer diseases, viral infections and genetic disorders has established the necessity to develop scalable methods for their cheaper and easier industrial manufacture. While small scale solid-phase oligonucleotide synthesis is the method of choice in the field, various challenges still remain associated with the production of short DNA and RNA-oligomers in very large quantities. On the other hand, solution phase synthesis of oligonucleotides offers a more predictable scaling-up of the synthesis and is amenable to standard industrial manufacture techniques. In the present thesis, various protocols for the synthesis of short DNA and RNA oligomers have been studied on a peracetylated and methylated β-cyclodextrin, and also on a pentaerythritol-derived support. On using the peracetylated and methylated β-cyclodextrin soluble supports, the coupling cycle was simplified by replacement of the typical 5′-O-(4,4′-dimethoxytrityl) protecting group with an acid-labile acetal-protected 5′-O-(1-methoxy-1-methylethyl) group, which upon acid-catalyzed methanolysis released easily removable volatile products. For this reason monomeric building blocks 5′-O-(1-methoxy-1-methylethyl) 3′-(2-cyano-ethyl-N,N-diisopropylphosphoramidite) were synthesized. Alternatively, on using the precipitative pentaerythritol support, novel 2´-O-(2-cyanoethyl)-5´-O-(1-methoxy-1-methylethyl) protected phosphoramidite building blocks for RNA synthesis have been prepared and their applicability by the synthesis of a pentamer was demonstrated. Similarly, a method for the preparation of short RNAs from commercially available 5´-O-(4,4´-dimethoxytrityl)-2´-O-(tert-butyldimethyl-silyl)ribonucleoside 3´-(2-cyanoethyl-N,N-diisopropylphosphoramidite) building blocks has been developed