| 1. |
- Alakangas, Lena, et al.
(författare)
-
StopOx : Utilization Of Industrial Residuals For Prevention Of Sulfide Oxidation In Mine Waste
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is the outcome of the SIP STRIM projectStopOx-Utilization of industrial residuals for prevention of sulfide oxidation in mine waste implemented at Applied geochemistry, Luleå University of Technology running from 2015 to 2018. Boliden Mineral has been partner and co-funder of the project. Other partners in the project were Cementa, Dragon Mining, MEROX, Nordkalk, and SP Processum. The overall aim of the project was to develop prevention technologies to reduce the sulfide oxidation in mine waste, during and after operation, and thereby reduce the generation of acid mine drainage. The StopOx project has been focusing on sulfidic mine waste from the Boliden area which were disposed of and are causing acid mine drainage or have the potential. Industrial residues/products were supplied by BillerudKorsnäs, Cementa, MEROX, and Nordkalk. The report consists of chapters based on three subprojects.Chapter 1. IntroductionChapter 2. Inhibition technology with aim to minimize waste rock oxidation during operations by using residues from other industries (passivation of sulfidic surfaces by the formation of secondary minerals)Chapter 3. The suitability of green liquor dregs as substitutes for or additives to till in a sealing layer as part of a cover systemChapter 4. Weathering of waste rock under changing chemical conditionsThe research described in chapters 2 and 3 was performed by Ph.D. students and will continue until 2021, while the subproject in chapter 2 ended in 2018.
|
|
| 2. |
- Kaasalainen, Hanna, et al.
(författare)
-
Chemical analysis of sulfur species in geothermal waters
- 2011
-
Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 85:4, s. 1897-1903
-
Tidskriftsartikel (refereegranskat)abstract
- Analytical methods have been developed to determine sulfur species concentrations in natural geothermal waters using Reagent-Free™ Ion Chromatography (RF™-IC), titrations and spectrophotometry. The sulfur species include SO 4 2-, S 2O 3 2-, and ∑S 2- with additional determination of SO 3 2- and S xO 6 2- that remains somewhat semiquantitative. The observed workable limits of detections were ≤0.5 μM depending on sample matrix and the analytical detection limits were 0.1 μM. Due to changes in sulfur species concentrations upon storage, on-site analyses of natural water samples were preferred. Alternatively, the samples may be stabilized on resin for later elution and analysis in the laboratory. The analytical method further allowed simultaneous determination of other anions including F -, Cl -, dissolved inorganic carbon (DIC) and NO 3 - without sample preservation or stabilization. The power of the newly developed methods relies in routine analysis of sulfur speciation of importance in natural waters using techniques and facilities available in most laboratories doing water sample analysis. The new methods were successfully applied for the determination of sulfur species concentrations in samples of natural and synthetic waters. © 2011 Elsevier B.V. All rights reserved.
|
|
| 3. |
|
|
| 4. |
- Kaasalainen, Hanna, et al.
(författare)
-
Geochemistry and speciation of Fe(II) and Fe(III) in natural geothermal water, Iceland
- 2017
-
Ingår i: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 87, s. 146-157
-
Tidskriftsartikel (refereegranskat)abstract
- The geochemistry of Fe(II) and Fe(III) was studied in natural geothermal waters in Iceland. Samples of surface and spring water and sub-boiling geothermal well water were collected and analyzed for Fe(II), Fe(III) and Fetotal concentrations. The samples had discharge temperatures in the range 27–99 °C, pH between 2.46 and 9.77 and total dissolved solids 155–1090 mg/L. The concentrations of Fe(II) and Fe(III) were determined in the <0.2 μm filtered and acidified fraction using a field-deployed ion chromatography spectrophotometry (IC-Vis) method within minutes to a few hours of sampling in order to prevent post-sampling changes. The concentrations of Fe(II) and Fe(III) were <0.1–130 μmoL/L and <0.2–42 μmoL/L, respectively. In-situ dialysis coupled with Fe(II) and Fe(III) determinations suggest that in some cases a significant fraction of Fe passing the standard <0.2 μm filtration method may be present in colloidal/particulate form. Therefore, such filter size may not truly represent the dissolved fraction of Fe but also nano-sized particles. The Fe(II) and Fe(III) speciation and Fetotal concentrations are largely influenced by the water pH, which in turn reflects the water type formed through various processes. In water having pH of ∼7–9, the total Fe concentrations were <2 μmoL/L with Fe(III) predominating. With decreasing pH, the total Fe concentrations increased with Fe(II) becoming increasingly important and predominating at pH < 3. In particular in waters having pH ∼6 and above, iron redox equilibrium may be approached with Fe(II) and Fe(III) possibly being controlled by equilibrium with respect to Fe minerals. In many acid waters, the Fe(II) and Fe(III) distribution may not have reached equilibrium and be controlled by the source(s), reaction kinetics or microbial reactions
|
|
| 5. |
- Kaasalainen, Hanna, et al.
(författare)
-
Impact of declining oxygen conditions on metal(loid) release from partially oxidized waste rock
- 2019
-
Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:20, s. 20712-20730
-
Tidskriftsartikel (refereegranskat)abstract
- The best available technology for preventing the formation of acid drainage water from the sulfidic waste rock at mine closure aims to limit the oxygen access to the waste. There is, however, a concern that contaminants associated with secondary minerals become remobilized due to changing environmental conditions. Metal(loid) mobility from partially oxidized sulfidic waste rock under declining and limited oxygen conditions was studied in unsaturated column experiments. The concentrations of sulfate and metal(loid)s peaked coincidently with declining oxygen conditions from 100 to < 5 sat-% and to a lesser extent following a further decrease in the oxygen level during the experiment. However, the peak concentrations only lasted for a short time and were lower or in the similar concentration range as in the leachate from a reference column leached under atmospheric conditions. Despite the acid pH (~ 3), the overall quality of the leachate formed under limited oxygen conditions clearly improved compared with atmospheric conditions. In particular, the release of As was two orders of magnitude lower, while cationic metals such as Fe, Cu, Mn, and Zn also decreased, although to a lesser extent. Decreased sulfide oxidation is considered the primary reason for the improved water quality under limited oxygen conditions. Another reason may be the immobility of Fe with the incorporation of metal(loid)s in Fe(III) minerals, in contrast to the expected mobilization of Fe. The peaking metal(loid) concentrations are probably due to remobilization from solid Fe(III)-sulfate phases, while the relatively high concentrations of Al, Mn, and Zn under limited oxygen conditions were due to release from the adsorbed/exchangeable fraction. Despite the peaking metal(loid) concentrations during declining oxygen conditions, it is clear that the primary remediation goal is to prevent further sulfide oxidation.
|
|
| 6. |
|
|
| 7. |
- Kaasalainen, Hanna, et al.
(författare)
-
Sulfur speciation in natural hydrothermal waters, Iceland
- 2011
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:10, s. 2777-2791
-
Tidskriftsartikel (refereegranskat)abstract
- The speciation of aqueous dissolved sulfur was determined in hydrothermal waters in Iceland. The waters sampled included hot springs, acid-sulfate pools and mud pots, sub-boiling well discharges and two-phase wells. The water temperatures ranged from 4 to 210°C, the pHT was between 2.20 and 9.30 at the discharge temperature and the SO4 and Cl concentrations were 0.020-52.7 and <0.01-10.0mmolkg-1, respectively. The analyses were carried out on-site within ~10min of sampling using ion chromatography (IC) for sulfate (SO42-), thiosulfate (S2O32-) and polythionates (SxO62-) and titration and/or colorimetry for total dissolved sulfide (S2-). Sulfite (SO32-) could also be determined in a few cases using IC. Alternatively, for few samples in remote locations the sulfur oxyanions were stabilized on a resin on site following elution and analysis by IC in the laboratory. Dissolved sulfate and with few exceptions also S2- were detected in all samples with concentrations of 0.02-52.7mmolkg-1 and <1-4100μmolkg-1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394μmolkg-1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3μmolkg-1. Thiosulfate and SO32- were not detected in <100°C well waters and S2O32- was observed only at low concentrations (<1-8μmolkg-1) in ~200°C well waters. In alkaline and neutral pH hot springs, S2O32- was present in significant concentrations sometimes corresponding to up to 23% of total dissolved sulfur (STOT). In steam-heated acid-sulfate waters, S2O32- was not a significant sulfur species. The results demonstrate that S2O32- and SO32- do not occur in the deeper parts of <150°C hydrothermal systems and only in trace concentrations in ~200-300°C systems. Upon ascent to the surface and mixing with oxygenated ground and surface waters and/or dissolution of atmospheric O2, S2- is degassed and oxidized to SO32- and S2O32- and eventually to SO42- at pH >8. In near-neutral hydrothermal waters the oxidation of S2- and the interaction of S2- and S0 resulting in the formation of Sx2- are considered important. At lower pH values the reactions seemed to proceed relatively rapidly to SO42- and the sulfur chemistry of acid-sulfate pools was dominated by SO42-, which corresponded to >99% of STOT. The results suggest that the aqueous speciation of sulfur in natural hydrothermal waters is dynamic and both kinetically and source-controlled and cannot be estimated from thermodynamic speciation calculations. © 2011 Elsevier Ltd.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Nyström, Elsa, et al.
(författare)
-
Prevention of sulfide oxidation in waste rock by the addition of lime kiln dust
- 2019
-
Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:25, s. 25945-25957
-
Tidskriftsartikel (refereegranskat)abstract
- During the operation of a mine, waste rock is often deposited in heaps and usually left under ambient conditions allowing sulfides to oxidize. To focus on waste rock management for preventing acid rock drainage (ARD) formation rather than ARD treatment could avoid its generation and reduce lime consumption, costs, and sludge treatment. Leachates from 10 L laboratory test cells containing sulfide-rich (> 60% pyrite) waste rock with and without the addition of lime kiln dust (LKD) (5 wt.%) were compared to each other to evaluate the LKD’s ability to maintain near neutral pH and reduce the sulfide oxidation. Leaching of solely waste rock generated an acidic leachate (pH < 1.3) with high concentrations of As (21 mg/L), Cu (20 mg/L), Fe (18 g/L), Mn (45 mg/L), Pb (856 μg/L), Sb (967 μg/L), S (17 g/L), and Zn (23 mg/L). Conversely, the addition of 5 wt.% LKD generated and maintained a near neutral pH along with decreasing of metal and metalloid concentrations by more than 99.9%. Decreased concentrations were most pronounced for As, Cu, Pb, and Zn while S was relatively high (100 mg/L) but decreasing throughout the time of leaching. The results from sequential extraction combined with element release, geochemical calculations, and Raman analysis suggest that S concentrations decreased due to decreasing sulfide oxidation rate, which led to gypsum dissolution. The result from this study shows that a limited amount of LKD, corresponding to 4% of the net neutralizing potential of the waste rock, can prevent the acceleration of sulfide oxidation and subsequent release of sulfate, metals, and metalloids but the quantity and long-term stability of secondary minerals formed needs to be evaluated and understood before this method can be applied at a larger scale.
|
|
| 11. |
- Nyström, Elsa, 1987-, et al.
(författare)
-
Prevention of Sulfide Oxidation in Waste Rock using By-products and Industrial Remnants : a Suitability Study
- 2017
-
Ingår i: Mine Water & Circular Economy. ; , s. 1170-1178
-
Konferensbidrag (refereegranskat)abstract
- Prevention and mitigation of acid rock drainage from mining are decisive for limiting environmental impact. Five by-products and industrial remnants (lime kiln dust, blast furnace slag, granulated blast furnace slag, cement kiln dust and fly ash) were investigated for their suitability to prevent acidity and metal(loid)s during leaching from highly sulfidic (50wt%, sulfide) waste rock in small scale laboratory test cells. Variations in pH and electrical conductivity in leachate allowed differentiation between the different materials. Lime kiln dust (5wt%) and fly ash (1 and 2.5wt%) were observed to be the most suitable materials to prevent acidity and metal(loid)s leaching.
|
|
| 12. |
|
|
| 13. |
- Nyström, Elsa
(författare)
-
Suitability of industrial residues for preventing acid rock drainage generation from waste rock
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the main and most challenging environmental problems related to mining is the generation of acid rock drainage (ARD), a leachate characterized by low pH and elevated concentrations of sulfate, metals, and metalloids formed when sulfide-bearing minerals are subjected to oxygen and water. During the operation of a mine, waste rock is often deposited in heaps and usually left under ambient conditions, enabling sulfides to oxidize. Generated ARD is commonly treated actively with alkaline material in an attempt to raise the pH and precipitate metals, with subsequent formation of sludge, which requires additional treatment. To focus on the treatment of waste rock rather than the ARD could prevent the generation of ARD; reduce the lime consumption, costs, and sludge treatment. This thesis aims to identify and evaluate the potential of different industrial residues to maintain circumneutral pH in a sulfide oxidation environment, allowing secondary minerals to form on the reactive sulfide surface to prevent sulfide oxidation and generation of ARD.Five different industrial residues (blast furnace slag, granulated blast furnace slag, cement kiln dust, bark ash, and lime kiln dust) were selected in a feasibility study performed prior to this study. The selection was based primarily on their alkaline properties, availability, and early yield. The waste rock was selected due to its high content of sulfides (>50%) and potential to generate ARD. Initial characterization of the industrial residues included combining mineralogical and chemical composition with batch testing (L/S 10). Sulfide oxidation in the leaching of the waste rock accelerated after week 29 resulting in high concentrations of major elements such as Al, Fe and S but also extremely high concentrations of e.g. As, Cu, Mn, Pb, Sb and Zn despite their relatively low content in the waste rock. Leaching was conducted during 14-153 weeks. The initial characterization implied that all of the studied industrial residues has the potential to prevent ARD generation. However, the enrichment and leachability of Pb in the cement kiln dust, as well as Cr and Zn in the bark ash, suggested the presence of elements of potential concern that could limit the use of the materials. When the industrial residues were added to the waste rock surface in small-scale laboratory test cells, blast furnace slag, granulated blast furnace slag, and cement kiln dust self-cemented and failed to maintain circumneutral pH, whereas bark ash (1wt.%) prevented acidity, metal and metalloid leaching. However, the use of bark ash may prove problematic due to the release of Cl, K, and Na likely related to salt dissolution. Lime kiln dust (5wt.%), the most promising of the industrial residues, maintained a circumneutral pH throughout the time of leaching, with an overall decrease of metal and metalloid concentrations by more than 99.9%. Results from investigations of secondary minerals formed combined with element release during the leaching period suggest that the addition of LKD to the waste rock led to decreasing concentrations of S in the leachate due to decreased sulfide oxidation, which subsequently led to gypsum dissolution. Moreover, the addition of LKD to the waste rock generated a lower amount of secondary minerals compared to when no addition was made.The results from these studies increase the understanding of advantages and limitations of using selected industrial residues in the treatment of mine waste. Moreover, it shows that a rather small amount of alkaline material, corresponding to 4% of the net neutralizing potential of waste rock, can prevent the acceleration of sulfide oxidation and subsequent release of sulfate, metals, and metalloids. However, the quantity and long-term stability of the formed secondary minerals need to be evaluated and understood before this method can be applied at larger scale.
|
|
| 14. |
|
|
| 15. |
- Nyström, Elsa, et al.
(författare)
-
Suitability study of secondary raw materials for prevention of acid rock drainage generation from waste rock
- 2019
-
Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 232, s. 575-586
-
Tidskriftsartikel (refereegranskat)abstract
- Prevention and mitigation of acid rock drainage (ARD) from mine wastes are crucial for limiting environmental impact. However, preventive measures are often too expensive, potentially harmful to the environment or not applied early enough. This study aimed to test the potential of different secondary raw materials for maintaining a circumneutral pH (6–7) in a sulfide oxidation environment, allowing secondary minerals to form on reactive sulfide surfaces to prevent release of acid, metals and metalloids, and thereby ARD generation. Five materials (blast furnace slag, granulated blast furnace slag, cement kiln dust, bark ash, lime kiln dust) were selected based on their alkaline properties, availability and yearly yield. High sulfidic (>50 wt%, sulfide) waste rock from an active Cu–Zn–Au–Ag open pit mine in northern Sweden was leached in small-scale laboratory test cells under ambient condition for 4–8 weeks before adding secondary raw materials on the surface in an attempt to prevent ARD generation. During 52 subsequent weeks of leaching, the pH and electrical conductivity in the leachate from the waste rock varied between 1.7-4.6 and 2.1–22.8 mS/cm, respectively. All secondary raw materials were able to increase the pH to circumneutral. However, blast furnace slag, granulated blast furnace slag and cement kiln dust were not able to maintain a circumneutral pH for an extended time due to self-cementation or carbonation, whereas bark ash (1 wt%) and lime kiln dust (5 wt%) prevented acidity, metal and metalloid leaching. Materials such as cement kiln dust and bark ash contained elevated concentrations of, e.g., Cd and Zn, but the release of metals and metalloids was generally low for most elements, except for Cl, K and Na, most likely due to salt dissolution.
|
|
| 16. |
- Planer-Friedrich, Britta, et al.
(författare)
-
Relative Abundance of Thiolated Species of As, Mo, W, and Sb in Hot Springs of Yellowstone National Park and Iceland
- 2020
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:7, s. 4295-4304
-
Tidskriftsartikel (refereegranskat)abstract
- Geothermal waters often are enriched in trace metal(loid)s, such as arsenic, antimony, molybdenum, and tungsten. The presence of sulfide can lead to the formation of thiolated anions; however, their contributions to total element concentrations typically remain unknown because nonsuitable sample stabilization and chromatographic separation methods convert them to oxyanions. Here, the concurrent widespread occurrence of thioarsenates, thiomolybdates, thiotungstates, and thioantimonates, in sulfide-rich hot springs from Yellowstone National Park and Iceland is shown. More thiolation was generally observed at higher molar sulfide to metal(loid) excess (Iceland > Yellowstone). Thioarsenates were the most prominent and ubiquitous thiolated species, with trithioarsenate typically dominating arsenic speciation. In some Icelandic hot springs, arsenic was nearly quantitatively thiolated. Also, for molybdenum, thioanions dominated over oxyanions in many Icelandic hot springs. For tungsten and antimony, oxyanions typically dominated and thioanions were observed less frequently, but still contributed up to a few tens of percent in some springs. This order of relative abundance (thioarsenates > thiomolybdates > thiotungstates ≈ thioantimonates) was also observed when looking at processes triggering transformation of thioanions such as mixing with non-geothermal waters or H2S degassing and oxidation with increasing distance from a discharge. Even though to different extents, thiolation contributed substantially to speciation of all four elements studied, indicating that their analysis is required when studying geothermal systems.
|
|
| 17. |
|
|
| 18. |
- Stefánsson, Andri, et al.
(författare)
-
Quantifying mixing, boiling, degassing, oxidation and reactivity of thermal waters at Vonarskard, Iceland
- 2016
-
Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 309, s. 53-62
-
Tidskriftsartikel (refereegranskat)abstract
- The chemical composition of geothermal fluids may be altered upon ascent from the reservoir to surface by processes including boiling, degassing, mixing, oxidation and water-rock interaction. In an attempt to quantify these processes, a three step model was developed that includes: (1) defining the composition of the end-member fluid types present in the system, (2) quantifying mixing between the end-members using non-reactive elemental concentrations and enthalpy and (3) quantifying the changes of reactive elements including degassing, oxidation and water-rock interaction. The model was applied to geothermal water at Vonarskard, Iceland, for demonstration having temperatures of 3-98°C, pH of 2.15-9.95 and TDS of 323-2250ppm, and was thought to be produced from boiled reservoir water, condensed steam and non-thermal water. Most geothermal water represented mixture of non-thermal water and condensed steam whereas the boiled reservoir water was insignificantly mixed. CO2 and H2S degassing was found to be quantitative in steam-heated water, with oxidation of H2S to SO4 also occurred. In contrast, major rock forming elements are enriched in steam-heated water relative to their mixing ratios, suggesting water-rock interaction in the surface zone. Boiled reservoir water observed in alkaline hot springs have, however, undergone less geochemical changes upon ascent to surface and within the surface zone.
|
|
| 19. |
- Stefánsson, Andri, et al.
(författare)
-
The geochemistry and sequestration of H2S into the geothermal system at Hellisheidi, Iceland
- 2011
-
Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273 .- 1872-6097. ; 202:3-4, s. 179-188
-
Tidskriftsartikel (refereegranskat)abstract
- The geochemistry and mineralization of H2S in the geothermal system hosted by basaltic rock formation at Hellisheidi, SW Iceland, was studied. Injection of mixtures of H2S with geothermal waste water and condensed steam into the >230°C geothermal aquifer is planned, where H2S will hopefully be removed in the form of sulphides. The natural H2S concentrations in the aquifer average 130ppm. They are considered to be controlled by close approach to equilibrium with pyrite, pyrrhotite, prehnite and epidote. Injection of H2S will increase significantly the reservoir H2S equilibrium concentrations, resulting in mineralization of pyrite and possibly other sulphides as well as affecting the formation of prehnite and epidote. Based on reaction path modelling, the main factors affecting the H2S mineralization capacity are related to the mobility and oxidation state of iron. At temperatures above 250°C the pyrite mineralization is greatly reduced upon epidote formation leading to the much greater basalt dissolution needed to sequestrate the H2S. Based on these findings, the optimum conditions for H2S injection are aquifers with temperatures below ~250°C where epidote formation is insignificant. Moreover, the results suggest that sequestration of H2S into the geothermal system is feasible. The total flux of H2S from the Hellisheidi power plant is 12,950tonnesyr-1. Injection into 250°C aquifers would result in dissolution of ~1000tonnesyr-1 of basalt for mineralization of H2S as pyrite, corresponding to ~320m3yr-1. © 2011 Elsevier B.V.
|
|
