Highly reactive iron-oxo intermediates play important roles as active oxidants in enzymatic and synthetic catalytic oxidation. Many transition metal catalysts are designed for biomimetic studies of the predominant oxidation catalysts in Nature, namely cytochrome P450 enzymes. In this work, a series of iron(IV)-oxo porphyrins [FeIV(Por)O] and manganese(IV)-oxo porphyrins [MnIV(Por)O] have been successfully produced in two electron-deficient ligands by photochemical and chemical methods, and spectroscopically characterized by UV-vis, and 1H-NMR. With iodobenzene diacetate [PhI(OAc)2] as the oxygen source, iron(III) porphyrin and manganese(III) porphyrin complexes converted to the corresponding metal(IV)-oxo species as oxygen atom transfer (OAT) agents. In addition, a new photochemical method was developed to generate the same species by visible light irradiation of highly photo-labile porphyrin-iron(III) bromate or porphyrin-manganese(III) chlorate precursors. Furthermore, the kinetics of oxygen transfer atom reactions with alkene, active hydrocarbons and aryl sulfides by photo-generated and chemical-generated [FeIV(Por)O]were studied in CH3CN solutions. Apparent second-order rate constants determined under pseudo-first-order conditions for sulfide oxidation reactions are (9.8 ± 0.1) × 102 − (3.7 ± 0.3) × 101 M-1s-1, which are 3 to 4 orders of magnitude greater in comparison with those of alkene epoxidations and activated C-H bond oxidations by the same oxo species.

It was recently shown that V-doped acid-prepared mesoporous silica (APMS) nanoparticles are active catalysts for the oxidation of the mustard gas analogue 2-chloroethyl ethyl sulfide (CEES) under ambient conditions in the presence of aldehydes, using O2 from air as the oxidation source. However, the vanadium ion leached from the surface when water was present, leading to decreased catalytic activity. Therefore, in this work, the environment around the vanadium is changed, using diethylenetriamine pentaacetic acid (dtpa) as a ligand and anchoring it to the surface of a mesoporous silica nanoparticle, to investigate its effect on vanadium’s ability to perform oxidation reactions. VO(dtpa)-APMS was synthesized by covalently linking the multi-dentate chelator dtpa onto the surface through peptide coupling of one of the acetate groups to aminopropyltriethoxysilane (APTES), condensing the dtpa-APTES molecule onto the mesoporous silica surface, and then exchanging a vanadyl salt into the resulting solid. Physical characterization of the material confirmed that the substrate retained its porosity after modification, and that the vanadium did not leach from the solid, in contrast to samples that did not contain dtpa. Solid-state EPR spectroscopy, combined with ongoing computational modeling, indicated that the vanadium was in a distorted five-coordinate environment. Various vanadium catalysts have been shown to oxidize alkanes, alkenes, alcohols and aromatic compounds. To further understand the catalyst’s ability to perform oxidation reactions, mechanisms of sulfides and alkenes were studied. Two model substrates were chosen for the investigation: CEES and cis-cyclooctene. The catalytic system effectively oxidizes CEES at room temperature in less than 15 minutes and cis-cyclooctene at 47 °C within 3 hours, using a peroxyacid generated in situ as the oxidant source. Kinetic experiments demonstrated that the mechanism of the sulfide reaction changed at higher temperatures, while the alkene reaction did not. In each reaction, a partial negative charge on the peroxyacid during the oxidation process was indicated. The confirmation of radical formation in the mechanism was experimentally shown by the appearance of an induction period when diphenylamine, a radical trap, was introduced into the reaction. VO(dtpa)-APMS performs two catalytic oxidations: the oxidation of propionaldehyde to make the peroxyacid and the oxidation of alkenes or sulfides. In the first reaction, O2 binds to the vanadium complex to form a superoxo eta-1-bound O2 radical. This species leads to the formation of peroxyacid through a radical process. The peroxyacid produced in this manner can then react with a sulfide or an alkene in a process also catalyzed by the VO(dtpa) complex. The peroxyacid coordinates with the vanadium center. Upon coordination, the sulfide or alkene directly reacts with the oxygen of the peroxyacid while the peroxyacid is being deprotonated. A 6-coordinate catalyst intermediate is formed prior to the release of the oxidation product and propionic acid to regenerate the VO(dtpa) complex.

The oxidation of sulfide minerals in mine waste rock has the potential to generate acidity and contribute sulfate, metals and other trace constituents to drainage. The rate and extent to which this process occurs are dependent upon climactic conditions and the overall hydrologic, geochemical and physical properties of the waste rock. A laboratory and field-based study is currently being conducted at the Diavik Diamond Mine in the Northwest Territories, Canada, which is investigating the evolution of waste rock exposed to subaerial conditions in the continuous permafrost region. Over the course of the mine life, Diavik is expected to generate a stock pile up to 120 Mt of low-sulfide waste-rock composed primarily of granite and granite pegmatite with smaller amounts of biotite schist which occurs as xenoliths, and trace contributions from diabase dykes. Waste rock is segregated based on sulfur content into Type I (< 0.04 wt % S), Type II (0.04-0.08 wt % S) and Type III (> 0.08 wt % S) rock. The Diavik Waste Rock Research Project includes four 2 m by 2 m lysimeter experiments, two each constructed with Type I and Type III waste rock. Also constructed were two well-instrumented, 15 m high test scale waste-rock piles, one composed of Type I and one composed of Type III uncovered waste rock, and one covered test pile based on a reclamation concept which consists of a Type III waste rock core, a 1.5 m glacial till layer, and a 3 m layer of Type I waste rock. In addition, instrumentation was installed in four locations of the operational waste-rock stockpile. The geochemical differences between the Type I and Type III lysimeters and test piles is discussed to compare the non-acid generating Type I waste rock with the potentially acid-generating Type III. The effluent from the Covered test pile retained the character of the Type III waste-rock core over the course of observation producing slightly acidic drainage, possibly due to a zone of unfrozen till on the crest as a result of heat trace within the test pile. Observations from the geochemistry of the Type III waste rock will also be compared to mineralogical analysis from Type III samples collected during installation of instruments in the full scale waste-rock stockpile. Due to the low concentration of sulfide minerals, advanced techniques such as SEM and synchrotron-based analyses were employed for in-depth characterization of initial sulfide-oxidation products. SEM images and elemental mapping reveal development of reaction rims on many pyrrhotite grains, but lower instances of weathering of pyrite. Distinct zonation of weathering trends between depths within the stockpile was also absent. These observations indicate that the waste rock is in the early weathering stages may not yet be affected by the formation of permafrost. These observations act as a baseline for future studies. Correlations between the mineralogical and geochemical analyses, in addition to future monitoring and continuation of these studies, will assist in understanding the evolution of waste rock stored in a permafrost environment.

This thesis is an investigation into biogenic sulfide oxidation and sulfate reduction associated with hydrothermal systems at oceanic spreading centers. First, the production of sulfur floc and 'snowblower' events due to sulfide oxidizing bacteria is investigated. The effects of sulfur floc on the pososity is shown to be negligible. 'Snowblower' events are shown to be sulfur floc that is stored over long periods of time mixed with a component of sulfur floc being created in a bloom event. Secondly, biogenic sulfate reduction in hydrothermal recharge zones is investigated and the effects on the concentration profiles is considered.

The oxidation of sulfide minerals in mine waste rock has the potential to generate acidity and contribute sulfate, metals and other trace constituents to drainage. The rate and extent to which this process occurs are dependent upon climactic conditions and the overall hydrologic, geochemical and physical properties of the waste rock. A laboratory and field-based study is currently being conducted at the Diavik Diamond Mine in the Northwest Territories, Canada, which is investigating the evolution of waste rock exposed to subaerial conditions in the continuous permafrost region. Over the course of the mine life, Diavik is expected to generate a stock pile up to 120 Mt of low-sulfide waste-rock composed primarily of granite and granite pegmatite with smaller amounts of biotite schist which occurs as xenoliths, and trace contributions from diabase dykes. Waste rock is segregated based on sulfur content into Type I (< 0.04 wt % S), Type II (0.04-0.08 wt % S) and Type III (> 0.08 wt % S) rock. The Diavik Waste Rock Research Project includes four 2 m by 2 m lysimeter experiments, two each constructed with Type I and Type III waste rock. Also constructed were two well-instrumented, 15 m high test scale waste-rock piles, one composed of Type I and one composed of Type III uncovered waste rock, and one covered test pile based on a reclamation concept which consists of a Type III waste rock core, a 1.5 m glacial till layer, and a 3 m layer of Type I waste rock. In addition, instrumentation was installed in four locations of the operational waste-rock stockpile. The geochemical differences between the Type I and Type III lysimeters and test piles is discussed to compare the non-acid generating Type I waste rock with the potentially acid-generating Type III. The effluent from the Covered test pile retained the character of the Type III waste-rock core over the course of observation producing slightly acidic drainage, possibly due to a zone of unfrozen till on the crest as a result of heat trace within the test pile. Observations from the geochemistry of the Type III waste rock will also be compared to mineralogical analysis from Type III samples collected during installation of instruments in the full scale waste-rock stockpile. Due to the low concentration of sulfide minerals, advanced techniques such as SEM and synchrotron-based analyses were employed for in-depth characterization of initial sulfide-oxidation products. SEM images and elemental mapping reveal development of reaction rims on many pyrrhotite grains, but lower instances of weathering of pyrite. Distinct zonation of weathering trends between depths within the stockpile was also absent. These observations indicate that the waste rock is in the early weathering stages may not yet be affected by the formation of permafrost. These observations act as a baseline for future studies. Correlations between the mineralogical and geochemical analyses, in addition to future monitoring and continuation of these studies, will assist in understanding the evolution of waste rock stored in a permafrost environment.

This research study's the use of biological sulfate reduction technologies for the treatment of Sasol Secunda's coal-mine drainage (CMD) using Fischer-Tropsch Reaction Water (FTRW) as a cost-efficient carbon source. The research aims to develop a prototype dynamic model that describes this co-treatment of FTRW and CMD in both a continuously stirred tank reactor (CSTR) biological sulfate reduction (BSR) system and a BSR gas-lift (BSR-GL) integrated system. The BSR-GL system recovers elemental sulfur (S0 ) from the H2S produced and stripped from the BSR unit. Furthermore, this study aims to use the prototype model for a quantitative comparison of the CSTR-BSR and BSR-GL systems. Two bench-scale 5-litre CSTR-BSR and a 20-litre BSR-GL system were operated, under varying feed COD concentrations and hydraulic retention times (HRTs), to generate datasets for use in verification and a rudimentary validation of the prototype model. The BSR-GL integrated system includes 1) a 1-litre H2S gas reactive absorption (ABS) unit utilising an aqueous ferric solution for the recovery of elemental sulfur (S0 ) from sulfide and 2) ferrous biological oxidation reactor to regenerate ferric from the ferrous for re-supply to the ABS unit. The datasets generated in the experimental study allowed for the identification, mathematical modelling and reaction verification of 32 components that interact as reactants and products in 23 reactions observed in the two BSR systems. The prototype model is presented in a mass and charge balanced Gujer matrix that includes, i) 5 SRB mediated processes, ii) 2 liquid-gas mass transfer processes, iii) 3 processes describing the ABS and Fe2+ bio-oxidation units, iv) 4 processes describing sulfide and elemental sulfur oxidation and v) the S0 and poly-sulfide aqueous equilibrium and vi) 9 processes describing death regeneration and BPO hydrolysis. This prototype model was implemented in the DHI WEST® software for initial stage simulation trials. The experimental datasets allowed for the first-stage estimation of the best-fit reaction rate equations and the calibration of the kinetic parameters related to the 23 reactions, using MATLAB® curve fitting toolbox. A pre-processor that describe the pH and equilibrium chemistry of the components of the artificially prepared FTRW+CMD feed mixture batches under varying total concentrations have also been developed in this research. This was done to generated influent file to the DHI WEST® simulations that incorporated the dynamics related to the FTRW+CMD feed mixtures. The sulfate utilisation rate (gSO4 -2 .l-1 .d-1 ) of the GL-BSR and CSTR-BSR systems were compared to determine which system had the best sulfate removal. The results were found to be as follows; a. On comparison it was found that the sulfate substrate utilisation rate for the CSTR_BSR system is 39.28% of that of the BSR-GL_N2 system, where both systems were fed at feed mixture of COD of 2500mgCOD/l, where the COD:SO4 2- was 0.7, b. For the same systems fed a feed mixture of COD at 5000mgCOD/l (COD:SO4 2- = 0.7), the sulfate substrate utilisation rate for the CSTR_BSR system was found to be 17.86% less than that of the BSR_GLN2 system. c. Finally, it was also found that the substrate utilisation rate for the CSTR_BSR system was 30.06% less than that of the BSR_GLN2 system at Se of 4gCOD/l, for both systems fed substrate at 5000mgCOD/l. Thus, it can be concluded that the sulfate substrate utilisation rate for the BSR-GL system is higher than that of the CSTR_BSR system, for systems fed COD feed mixtures at 2.5 or 5gCOD/l where both systems have the same effluent substrate concentrations. However, the difference in the comparative substrate utilisation rate is less at higher feed substrate concentrations. This is the influence of substrate inhibition on the active SRB biomass, which increases with higher effluent substrate concentrations. Finally, this research found that the use of gas-lift reactor technologies is superior to CSTR technologies in the treatment of coal-mine drainage utilising biological sulfate reduction (BSR). The CSTR-BSR system, fed sulfate between 1.6 to 14gSO4 2- /l, produced effluent with high dissolved H2S concentrations, on average 285mgS/l and maximum at >600mgS/l. Releasing this effluent to the environment would be hazardous to aquatic and human health and corrosive to infrastructure. As such, the effluent from the CSTR-BSR system requires further treatment to stabilise the water for any use. The BSR-GL technology allows for the conversion of the H2S produced during BSR reactions to form elemental sulfur, which is a resource recovered from this process, thus complying to the circular economy aim of this study.

The Swedish mining industry has changed from the historical situation with several smaller mines to the present situation with a few, bigger mines. This results in presence of abandoned mines around Sweden. Remediation of mines is regulated by legislation and the present demands are considerably higher than it was some decades ago.  The Storliden mine was a Zink- and Coppermine active between 2001-2008. Storliden is located in Malå municipality, Västerbotten county, and is included in the Skellefte district, known for its sulfide mineralizations.  The ore was broken underground with a technique called cut and fill mining. It was estimated that the ore was to be consumed in 2007, but due to rising ore prices, the mine was operated until 2008. Remediation was done through backfilling the mine with waste rock from Storliden and Boliden’s mines Renström, Kedträsk, and Kankberg. Also, tailings, concrete, and sludge from the sedimentation basins were backfilled. Today, the mine is filled with water.  High Arsenic concentrations in water is a serious health issue in parts of the world. Bangladesh is perhaps the most common example where Arsenic in groundwater has caused health problems for millions of people. In Sweden, the Skellefte field is known for its elevated Arsenic concentrations in the bedrock, related to sulfide mineralizations. Studies confirm a correlation between Arsenic-bearing bedrock and elevated concentrations in water.  This thesis work has been conducted together with the consultant company Golder Associates (Golder) in Luleå. Golder has performed environmental investigations in the Storliden area during the period 2018-2020. Installation and sampling of groundwater wells were included in this investigation. High concentrations of Arsenic was found in some of the groundwater wells. This thesis aims to review potential sources of Arsenic and their potential significance. The purposes are to be fulfilled by evaluating and interpreting the results from the sampling, Piper diagrams, ratios, and modeling in the program PHREEQC.  The results indicate that the presence of Arsenopyrite in the bedrock is the most likely source of the elevated concentrations of Arsenic in deep groundwater. Oxidation of Arsenopyrite is likely caused by mainly dissolved oxygen in groundwater. Further, the water quality differs from different depths, indicating that deep groundwater and water flow from the mine via the ramp do not have any immediate connection. It is likely that remains of tailings on the industrial area cause low pH and leaching of metals locally.  High concentrations of Arsenic can occur very locally, highlighting the importance of conducting sampling of groundwater used as drinking water in areas where sulfide mineralizations are confirmed or suspected. Further, a relation between the time that water is in contact with the bedrock/mineralization and the concentration of Arsenic is stated. Higher concentration HCO3- tends to correlate with elevated Arsenic concentration. / Sveriges gruvindustri har förändrats i snabb takt, från ett flertal mindre gruvor till dagens läge med ett mindre antal större gruvor. Detta resulterar i förekomst av nedlagda gruvor runt om i Sverige. Efterbehandling av gruvor regleras genom lagstiftning, och kraven idag är betydligt högre än för bara något decennium sedan.   Storlidengruvan var en zink- och koppargruva verksam mellan 2001–2008. Storliden ligger i Malå kommun och området ingår i Skelleftefältet, känt för sina sulfidmineraliseringar. Malmen bröts i en underjordsgruva med så kallad igensättningsbrytning, dvs. tomrum har succesivt fyllts ut med material under driften. Malmen beräknades vara förbrukad 2007, men när malmpriset ökade kunde gruvan leva vidare till 2008. Efterbehandlingen innebar att fylla igen gruvan med gråberg från Storliden men också gråberg från Bolidens gruvor Renström, Kedträsk och Kankberg. Dessutom användes anrikningssand, cement och slam från sedimentationsbassängerna för att fylla igen gruvan. Länshållning av gruvan upphörde och idag är gruvan vattenfylld. Höga arsenikhalter i vatten är ett hälsoproblem i delar av världen. Det kanske vanligaste exemplet är Bangladesh, där arsenik i grundvatten har orsakat hälsoproblem för miljontals människor. I Sverige är Skelleftefältet utmärkande för den höga arsenikhalten i berggrunden. Naturlig arsenikhalt i borrade brunnar har undersökts i flera studier som visar ett samband mellan arsenikhaltig berggrund och förhöjda halter i vatten.  Examensarbetet har utförts tillsammans med konsultföretaget Golder Associates i Luleå. Golder har fått i uppdrag att utföra miljötekniska undersökningar i Storlidenområdet, bland annat ingick installation och provtagning av grundvattenrör. Denna provtagning skedde under perioden 2018–2020. I några av grundvattenrören påträffades förhöjda halter av arsenik. Detta examensarbete syftar till att utreda förekomsten av Arsenik i grundvattnet, undersöka vilka källor som kan vara orsaken till arsenikhalterna samt källornas förväntade betydelse. Detta har gjorts genom att utvärdera och tolka resultaten från provtagningarna samt användningen av Piper-diagram, geokemiska kvoter och geokemisk modellering i programmet PHREEQC. Resultaten indikerar att förekomst av arsenikkis som mineralisering i berggrunden är den mest troliga källan till de förhöjda halterna av arsenik i djupt grundvatten. Oxidationen av arsenikkis sker troligtvis främst av löst syre i grundvattnet. Vidare skiljer sig vattenkvalitén åt från olika djup och delar av området som provtagits, dvs. det verkar inte finnas någon omedelbar koppling mellan djupt grundvatten och vatten som kommer via rampen som leder till gruvan. Det är troligt att rester av anrikningssand på industriområdet orsakar lågt pH och metallutlakning lokalt.  Höga arsenikhalter kan förekomma lokalt, vilket understryker vikten av att utföra provtagning av grundvatten som används för dricksvatten i områden där misstänkt eller konstaterade sulfidmineraliseringar förekommer, eftersom arsenik annars kan vara en mycket skadlig ”diffus” förorening. Vidare konstateras också samband mellan den tid som vatten är i kontakt med mineralisering och arsenikhalt. Högre halt HCO3- tenderar att korrelera med förhöjd arsenikhalt

Acid Sulfate soils (AS) are recognized for being a source of acidity in freshwaters in America, Europe, Australia, and Asia. Apart from the problematic acid leachate, AS soil serves as a possible source of toxic heavy metals in freshwaters, a problem which has received far less attention than problems related to acid leachate. This study assessed to what extent heavy metals enriched in sediments from the area around lake Persöfjärden (North-eastern Sweden) could be attributed to export from AS soils. I found that: i) Nickel (Ni), Zink (Zn), Copper (Cu) and Iron (Fe) in the sediments had a partial likely origin from AS soils; ii) vertical variations in Ni, Zn, Cu and Fe concentrations suggested events of increased metal transport in the past; and iii) there is a tendency that Zn and Ni assumed from AS soils have caused elevated metal concentration in marine sediment deposited in Persöfjärden. Inferred sediment rates suggest that elevated metal concentrations occurred in sediment deposited during the 18-19th and 20th century. I argue that these periods correspond to periods of increased drainage of the AS soils during past agricultural activities in the catchment.

Sulfide-bearing rock that is excavated in conjunction with construction projects can cause environmental and construction engineering problems. Sulfidic minerals oxidize when they are exposed to an oxidant and water, which can make them generate acid rock drainage (ARD) with high concentrations of metals and sulphate. Predicting the overall oxidation process and drainage properties is, however, difficult since these depend on various factors. In this master thesis the current state of a 20-year-old ARD case is studied and compared to early site conditions to improve the knowledge of how different sulfide-bearing rocks may behave over time. The study investigates the drainage water and its impact on a local watercourse, but also chemical and mineralogical properties of oxidized rock from the site. The concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, S, and Zn in the drainage and watercourse has been studied and compared to data from when the sulfide-bearing rock was excavated and deposited.  The chemical composition and occurrence of sulfides in different rock types from the area has been examined through chemical analysis, SEM-EDS techniques, and sequential extractions. XRD data has been collected but was not interpreted within this project. The results from the water chemistry investigations showed that the concentrations of Cd, Co, Cr, Cu, Ni, and Zn had decreased since 2004, while the concentrations of Al, Fe, and Mn had increased. These elements mainly originated from a drainage pipe below ground level and later precipitated in the watercourse; only nickel and sulphate concentrations remained elevated 800 meters downstream from the studied rock storage. It was also shown that other sources in the area contaminated the watercourse. Masses of the previously deposited sulfide-bearing rock were moved approximately 10 years ago, which increase the uncertainty of conclusions drawn from the drainage. However, the elevated electrical conductivity and metal content of the drainage are signs of sulfide oxidation. The high concentration of aluminium likely indicates that the pH is buffered by silicates in the rock storage, and the concentrations of iron and manganese could also originate from silicates, or from sulfide oxidation. Pyrite was found abundantly in clusters in metasedimentary rock. Mainly pyrite, but also sphalerite and pyrrhotite was found in less oxidized, mica rich metafelsic rock. Both pyrite and sphalerite appeared in conjunction with mica, whereof pyrite as crack fillings. In more oxidized samples of mica rich rock, close to no sulfides were observed. The substantial difference in this rock is likely because the sulfides in conjunction with mica are particularly exposed to oxidation since fractures tend to appear along mica, and the sulfides located there have large specific surface areas. The presence of sulfides in the mica poor rock grouping of this study proved to be very heterogenous. In future studies there is therefore a need to further divide this group and study the sulfide-bearing metasedimentary rock from this site separately. In addition, the mineralogical source of the manganese in the water should be investigated in further studies.

No description available.