O presente trabalho mostra os resultados obtidos no estudo da utilização do rejeito bruto da extração de carvão mineral como agregado miúdo na produção de blocos de concreto para pavimentação de vias públicas. Neste trabalho os blocos de concreto foram produzidos na fábrica da prefeitura de Criciúma, que está situada nas dependências do Presídio Municipal Santa Augusta. Esta fábrica proporciona uma opção de trabalho aos apenados que adquiriram o direito de cumprirem suas penas em regime semiaberto, cumprindo assim, um importante papel social na ressocialização destas pessoas, além de produzir o material de revestimento, que é aplicado nas vias públicas do município, a um custo bastante atraente. Durante a produção das amostras dos blocos de concreto com o rejeito de carvão, procurou-se ao máximo não alterar o processo desenvolvido na fábrica onde são produzidos os blocos de concreto empregados na pavimentação das vias públicas de Criciúma. Sendo assim, a única alteração imposta às amostras foi a substituição proporcional do agregado miúdo natural, areia lavada, pelo agregado de rejeito de carvão mineral, nas proporções de 25%, 50%, 75% e 100% O lote de estudo contou ainda com a produção de blocos de concreto sem adição de rejeito de carvão, que teve como função servir de base comparativa para as análises de compressão, abrasão e absorção de água. Posteriormente foi realizado um estudo para avaliar a possibilidade de geração, pelos blocos de concreto, de drenagem ácida de mina (DAM), que é a principal fonte de poluição do solo e dos corpos d’agua dos municípios pertencentes à AMREC – Associação dos Municípios da Região Carbonífera. Como resultado, aponta-se a viabilidade de utilização de rejeito de carvão nas proporções de 25% e 50% em substituição ao agregado miúdo natural (areia), criando assim, uma nova perspectiva às mineradoras de carvão da AMREC, que poderão dar um fim nobre ao rejeito de carvão, proporcionando uma produção mais limpa e sustentável, além de poderem contar com uma nova fonte de receita proporcionada pela comercialização do rejeito de carvão produzido na sua principal atividade comercial. / This document presents the results obtained in the study of using raw waste of coal extraction. In this work the concrete block for public roads paving were produced in a factory owned by Criciuma city hall, which is situated at the municipal Penitentiary Santa Augusta. During the concrete samples blocks production with the coal waste, it was tried its best in the way of not changing the process developed at the concrete blocks production site used in the paving of Criciuma´s streets. Thus, the only change that was proportionally imposed in the sample was the replacement of fine natural aggregate, washed sand, for the coal tailings aggregate in the proportions of 25%, 50%, 75% and 100%. The batch study also included the production of concrete blocks without adding coal tailing, which was to form the basis of comparative function for the compression tests, abrasion and water absorption. Afterwards, it was done a study to assess the possibility of generating, by concrete blocks, acid mine drainage (AMD), which is the main source of soil and water pollution in the municipalities belonging from AMREC - Association of Municipalities of the Coal Region. As a result, it points feasibility of using waste coal in the proportions of 25% and 50% to replace the natural aggregate (sand), thus creating a new perspective to AMREC coal mining companies, which may give a noble and to reject coal, providing a cleaner and sustainable production, besides being able to count on a new source of revenue provided by the commercialization of coal waste produced in its main commercial activity.

O presente trabalho mostra os resultados obtidos no estudo da utilização do rejeito bruto da extração de carvão mineral como agregado miúdo na produção de blocos de concreto para pavimentação de vias públicas. Neste trabalho os blocos de concreto foram produzidos na fábrica da prefeitura de Criciúma, que está situada nas dependências do Presídio Municipal Santa Augusta. Esta fábrica proporciona uma opção de trabalho aos apenados que adquiriram o direito de cumprirem suas penas em regime semiaberto, cumprindo assim, um importante papel social na ressocialização destas pessoas, além de produzir o material de revestimento, que é aplicado nas vias públicas do município, a um custo bastante atraente. Durante a produção das amostras dos blocos de concreto com o rejeito de carvão, procurou-se ao máximo não alterar o processo desenvolvido na fábrica onde são produzidos os blocos de concreto empregados na pavimentação das vias públicas de Criciúma. Sendo assim, a única alteração imposta às amostras foi a substituição proporcional do agregado miúdo natural, areia lavada, pelo agregado de rejeito de carvão mineral, nas proporções de 25%, 50%, 75% e 100% O lote de estudo contou ainda com a produção de blocos de concreto sem adição de rejeito de carvão, que teve como função servir de base comparativa para as análises de compressão, abrasão e absorção de água. Posteriormente foi realizado um estudo para avaliar a possibilidade de geração, pelos blocos de concreto, de drenagem ácida de mina (DAM), que é a principal fonte de poluição do solo e dos corpos d’agua dos municípios pertencentes à AMREC – Associação dos Municípios da Região Carbonífera. Como resultado, aponta-se a viabilidade de utilização de rejeito de carvão nas proporções de 25% e 50% em substituição ao agregado miúdo natural (areia), criando assim, uma nova perspectiva às mineradoras de carvão da AMREC, que poderão dar um fim nobre ao rejeito de carvão, proporcionando uma produção mais limpa e sustentável, além de poderem contar com uma nova fonte de receita proporcionada pela comercialização do rejeito de carvão produzido na sua principal atividade comercial. / This document presents the results obtained in the study of using raw waste of coal extraction. In this work the concrete block for public roads paving were produced in a factory owned by Criciuma city hall, which is situated at the municipal Penitentiary Santa Augusta. During the concrete samples blocks production with the coal waste, it was tried its best in the way of not changing the process developed at the concrete blocks production site used in the paving of Criciuma´s streets. Thus, the only change that was proportionally imposed in the sample was the replacement of fine natural aggregate, washed sand, for the coal tailings aggregate in the proportions of 25%, 50%, 75% and 100%. The batch study also included the production of concrete blocks without adding coal tailing, which was to form the basis of comparative function for the compression tests, abrasion and water absorption. Afterwards, it was done a study to assess the possibility of generating, by concrete blocks, acid mine drainage (AMD), which is the main source of soil and water pollution in the municipalities belonging from AMREC - Association of Municipalities of the Coal Region. As a result, it points feasibility of using waste coal in the proportions of 25% and 50% to replace the natural aggregate (sand), thus creating a new perspective to AMREC coal mining companies, which may give a noble and to reject coal, providing a cleaner and sustainable production, besides being able to count on a new source of revenue provided by the commercialization of coal waste produced in its main commercial activity.

Fanny Creek drains from Island Block opencast coal mine, near Reefton on the West Coast of the South Island of New Zealand, and is impacted by acid mine drainage (AMD). The objectives of this study were to characterise drainage chemistry in Fanny Creek catchment, and to determine optimal passive treatment strategies for Fanny Creek AMD for future pilot or full-scale application. This was undertaken by monthly monitoring in Fanny Creek catchment between February 2008 and January 2009 to collect drainage chemistry and flow data. Laboratory trials of suitable passive AMD treatment systems were conducted and their treatment performance assessed to select and design optimal passive treatment strategies for Fanny Creek AMD. Oxidation of pyrite in Brunner Coal Measure sediments at Island Block mine generates AMD. Fanny Creek originates from a number of AMD seeps on the eastern waste rock slope of Island Block mine. Seeps have low pH (<3.23) and a single detailed metal analysis indicates drainage is enriched with aluminium and iron, and contains elevated concentrations of manganese, copper, nickel, zinc and cadmium relative to applicable water quality criteria such as ANZECC guidelines. Acidity and metal loadings of drainage in the catchment indicates AMD from the northern waste rock slope contributes most of the acidity (~70%) and metal (60%) in Fanny Creek, and acts to re-dissolve additional metals upon mixing with drainage from other slopes. The most suitable location for a passive AMD treatment system in Fanny Creek catchment is on the Waitahu Valley floor, near monitoring site R12, because this allows for sediment removal prior to a treatment system. Fanny Creek AMD at site R12 was characterized in detail because this data assists with selection and design of passive AMD treatment systems. Fanny Creek at site R12 contains on average 6.0 mg/L aluminium, 1.3 mg/L iron, 3.1 mg/L manganese, 0.49 mg/L zinc, 0.14 mg/L nickel, 0.0071 mg/L copper and 0.00048 mg/L cadmium. Average pH at site R12 was 3.95, calculated acidity averaged 42.7 mg CaCO₃/L, and flow rate ranged from 1.5 L/s to about 30 L/s. Acidity and metal generation from Island Block mine increases linearly with flow in the catchment, and therefore Fanny Creek drainage chemistry is not significantly affected by rainfall dilution. Natural attenuation of AMD occurs by addition of un-impacted alkaline drainage from Greenland Group basement rocks, wetland ecosystem processes, and geochemical reactions along Fanny Creek that decrease acidity and metal concentrations before AMD discharges into the Waitahu River. During low flow conditions (summer months), surface flow of AMD into the Waitahu River does not occur because of subsurface flow loss. Three suitable passive AMD treatment options for Fanny Creek AMD were selected and trialed at ‘bench top’ scale in a laboratory. These included a sulfate reducing bioreactor (SRBR), a limestone leaching bed (LLB), and an open limestone channel (OLC). The potential to mix Waitahu River water with Fanny Creek to neutralize AMD was also investigated. Fanny Creek AMD was employed for laboratory trials, and influent flow rates into SRBR, LLB and OLC systems were regulated to assess performance at different hydraulic retention times (HRT). Optimal HRTs for future treatment system designs were determined from effective AMD treatment thresholds, and include 51 hours, 5 hours and 15 hours for SRBR, LLB and OLC systems, respectively. To determine optimal treatment options for Fanny Creek AMD the effectiveness of each trial option was compared to applicable water quality criteria, and scale up implications of treatment options was assessed. The SRBR system had most effective AMD treatment, with water quality criteria achieved for metals, greatest alkalinity generation, and highest pH increase. However, a full scale SRBR system has significant size requirements, and long term treatment performance may be limited. The LLB system decreased metals to below, or just slightly above criteria for all metals, and has significantly smaller size requirements compared to a SRBR system. The OLC system was least effective, with effluent above water quality criteria for all metals except iron, and with lowest alkalinity generation. The Waitahu River is capable of neutralizing AMD because it is slightly alkaline. The flow volume of river water required for neutralization is between 65 L/s and 140L/s, which can be gravity fed to mix with Fanny Creek. These results indicate that either a LLB treatment system or the Waitahu River Mixing option are the optimal passive treatment strategies for Fanny Creek AMD. On site pilot scale testing of SRBR and LLB systems, and the Waitahu River Mixing option is recommended because of AMD treatment uncertainty, and to more accurately select and design full scale passive treatment strategies.

Ce travail de thèse a pour objectif de développer une méthodologie permettant de prédire l’impact environnemental des futurs projets miniers, dès l’étape d’exploration. Le drainage minier acide, connu comme le principal problème environnemental des gisements sulfurés, se produit lors de l’oxydation des sulfures par l’oxygène et l’eau. Des échantillons de sulfures et sulfosels ont été soumis à des tests géochimiques afin d’étudier leur taux de réactivité. Les minéraux ont été classés par ordre décroissant: gersdorffite > pyrrhotite > arsénopyrite > Ni-pyrite > Ni-pyrrhotite > Fe-sphalérite > pyrite > galène > chalcopyrite. L’influence des interactions galvaniques sur le taux de réactivité de la pyrite, la chalcopyrite et la sphalérite a été étudiée. La pyrite est protégée galvaniquement en présence de chalcopyrite mais n’est pas complètement protégée en présence de sphalérite. Des mélanges synthétiques de minéraux purs ont permis la modification du calcul de potentiel de génération d’acidité par l’ajout d’un facteur cinétique, basée sur les équations de Paktunc (1999) et Bouzahzah et al. (2013). Dix minerais polymétalliques et aurifères ont été caractérisés selon une méthodologie pluridisciplinaire. La caractérisation minéralogique des minerais a permis de connaître leur composition minéralogique quantitative et de détecter les éléments contaminants ainsi que leur spéciation. Une méthode automatisée de quantification minéralogique basée sur la microscopie optique multispectrale a été développée. Cette innovation vise à développer la microscopie optique pour des applications métallurgiques et environnementales de routine / This thesis proposes the implementation of a reliable methodology, based on the characterization of ores at the exploration stage. The main environmental issues for the mining industry are acid mine drainage and contaminated neutral drainage. Sulfides and sulfosalts, when in contact with water and oxygen, oxidize at different rates, resulting in the production of acid and release of various contaminants. Samples of pure sulfides were submitted to geochemical testing to determine their oxidation rates. The pure minerals can be ordered from the highest to the lowest reactivity as: gersdorffite > pyrrhotite > arsenopyrite > Ni-pyrite > Ni-pyrrhotite > Fe-sphalerite > pyrite > galena > chalcopyrite. Galvanic interactions between pyrite, chalcopyrite, and sphalerite were geochemically investigated. Pyrite was galvanically protected in presence of chalcopyrite, and partially protected in presence of sphalerite. Five synthetic tailings, simulating realistic tailings sulfides compositions, were prepared to compare geochemical behaviors and produce a better assessment of the acid-generation potential (AP). A new method is proposed by adding a kinetic factor. Ten polymetallic and gold sulfide ores were fully characterized with multidisciplinary techniques. Mineralogical investigations allowed for the mineralogical quantification of the ores, and for the knowledge of trace elements and their speciation. A method was developed to automatically quantify sulfides by multispectral optical microscopy. Detailed mineralogical work can save time and money and allows detecting the problems at the beginning of mining developments, improving mine waste management and mine closure planning

Waste rocks (WRs) from coal mining and fly ash (FA) from coal combustion were studied to determine the potential of the WRs to generate AMD, FAs to neutralise it and estimate their impacts on environment. The ultimate goal was to develop a methodology based on co-disposal to mitigate the environmental problems associated to both wastes. Two methods for co-disposal were tested: i) Mixing WRs and FAs and ii) covering WRs with FAs. WRs were sampled from the Lakhra coal mines in Pakistan (PK), which has an estimated coal reserves of 1.3 Btonne, varying from lignite to sub-bituminous quality. The FA was sampled from a power plant utilising coal from Lakhra coal mines and is situated in close vicinity (15km) of the mine site. For comparative purposes a bituminous FA from Finland (FI) and biomass FA from Sweden (SE) were also characterised. The WRs and FA samples were characterised by mineralogical and geochemical methods. Besides organic material (coal traces), quartz, pyrite, kaolinite, hematite, gypsum and traces of calcite, lime, malladerite, spangolite, franklinite and birnessite were identified in WRs by XRD. The major elements Si, Al, Ca and Fe were in the range (wt. %) of 8 – 12, 6 – 9, 0.3 – 3 and 1 – 10, respectively, with high S concentrations (1.94 – 11.33 wt. %) in WRs. The AMD potential of WRs ranged from -70 to -492 kg CaCO3 tonne-1. All FAs contained quartz, with iron oxide, anhydrite and magnesioferrite in PK, mullite and lime in FI and calcite and anorthite in SE. The Ca content in SE was 6 and 8 times higher compared to PK and FI, respectively. FAs were enriched in As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn compared to continental crust. The acid neutralising potential of PK was equivalent to 20 kg CaCO3 tonne-1 compared to 275 kg CaCO3 tonne-1 (SE) and 25 kg CaCO3 tonne-1 (FI). During the period of 192 days in weathering cell experiments (WCE), the pH of leachates from most acidic WRs was maintained from 1 to 2.5, whereas, the less acidic WRs produced leachates of mildly acidic (2.7) to neutral (7.3) pH. The leachates from very acidic WRs ranged in the concentrations of Fe, SO24− and Al from mg L-1 to g L-1. The samples were subjected to column leaching experiments (CLE) in which mixture (FA:WR; 1:3) and cover (FA:WR; 1:5) cases were mimicked (with 10mm particle size) and effects of particle size (2, 5 and 10mm) on element leaching were studied. Despite having the lowest acid-neutralisation potential compared to FI and SE, co-disposal of PKFA as mixture readily provides acid buffering minerals, resulting in better start-up pH conditions and leachate quality. However, acidity produced by secondary mineralisation contributes towards the acidification of the system, causing stabilisation of pH at around 4.5−5. Secondary mineralisation (especially Fe- and Al-mineral precipitation) also removes toxic elements such as As, Pb, Cu, Zn, Cd, Co, Ni and Mn, and these secondary minerals can also buffer acidity when the pH tends to be acidic. In contrast, the pH of the leachates from the PKFA cover scenario gradually increased from strongly acidic to mildly acidic and circumneutral along with decrease in EC and elemental leaching in different WRs. Gradually increasing pH can be attributed to the cover effect, which reduces oxygen ingress, thus sulphide oxidation, causing pH to elevate. Due to the fact that pH~4–5 is sufficient for secondary Fe- and Al-mineral precipitation which also removes toxic elements (such as Cd, Co, Cu, Zn and Ni) by adsorption and/or co-precipitation, the FA cover performs well enough to achieve that pH until the conclusion of the CLE. However, due to the slower reactivity of the buffering system (additional to the initial flush-out), leaching in the beginning could not be restricted. The co-disposal of FA as cover and/or mixture possesses potential for neutralisation of AMD and improving leachate quality significantly. Particle size of the WRs affected the leaching of the sulphide related elements (such as Fe, S, Zn, Co, Cr, Cu, Mn and Ni) in CLE and WCE. Experiments with ≤1mm particle size constantly produced acidic and metal laden leachates. Co-disposal of FA and WRs as cover and mixture need to be investigated on pilot-scales before full-scale application.

Impacts from mining waste deposits on groundwater resources have been recognized invarious parts of the world; though varied in scale depending on the composition of mineralsbeing mined, the level of technology employed and environmental commitment of thedevelopers. Mining activities usually involve milling, concentrating, and processing of oreswhich will result in a huge amount of waste, called tailings, usually deposited inimpoundments as a slurry, composed of fine grained geological material (uneconomicalminerals), chemicals utilized in the processs, and water. Oxidation of these deposits, usuallycontaining sulphide minerals, may result in generation of an acidic, metal laden leachate,callled Acid Mine Drainage (AMD), which may have a devastating impact on thesurrounding groundwater resources. In this study, the stochastic LaSAR-PHREEQC reactive transport modeling approach is usedin order to evaluate the coupled effect of geochemical reactions and physical heterogeneity ofthe subsurface in the breakthrough of acidity and metal downstream of the source while theAMD transported in the water saturated zone of an impoundment. The tailings depositcalled Impoundment 1 at the Kristineberg mining site at the Skellefteå field, in northernSweden, is used as a case study to simulate pH buffering processes and attenuation of Zn.The objectives of the study are 1) to evaluate the relevance of different possible geochemicalprocesses in pH buffering and Zn attenuation; 2) to evaluate the effect of spatial variability ofthe physical processes of the groundwater system on the breakthrough of contaminants; and3) to evaluate the effect of the location and distribution of the source zone in terms of thedistance from the impoundment boundary. Simulation results of the presented model revealed that pH buffering from calcite andchlorite are important processes capable of counteracting the acidification from AMD.Dissolution of secondary Al(OH)3(s) is another important process capable of buffering pH.Precipitation of smithsonite, ZnCO3, is an important process for attenuation of Zn2+.Moreover, sorption of Zn2+ on ferric iron surfaces is found to be an important process forattenuation of the metal, depending on the available sorption surface sites. Flow variabilityhighly affects the breakthrough of the contaminants such that with increasing subsurfaceheterogeneity, earlier breakthrough of contaminants occurs. Moreover, increased variabilityresults in decreased peak loads, but longer duration of the load. / www.ima.kth.se

With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental CO2 . Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2 , CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2 . Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant changes were observed in the binding geometry of the adsorbed complexes on the Al/Fe mineral compared to single phase α-FeOOH, AlOOH, and FeOOH surfaces. ATR-FTIR results combined with vibrational frequency (DFT) calculations suggested the formation of multiple phosphate surface complexes via a variety of configurations such as inner-sphere/outer-sphere bidentate, monodentate depending on the solution pH and the Al mol% substituted into the Fe-oxyhydroxide. Studies investigated the adsorption of CO2 on FerriFh and compared those results to CO2 on ferrihydrite. The CO2 pressures used in these particular studies ranged from 1 to 57.8 bars. It is found that citrate bound species, resulting from the synthesis conditions used to make FerriFh, blocked surface sites for the formation of carbonate and bicarbonate species on the magnetic FerriFh and ferrihydrite oxyhydroxide minerals upon CO2 (gas) exposure. A bicarbonate or bent-CO2 like species (~1220 cm-1) formed at lower CO2 pressures (≤ 3.5 bars) but was absent at the higher pressures. Additional studies investigated the adsorption of various phospholipid molecules on pyrite, and iron sulfide with FeS2 stoichiometry. These studies were focused on suppressing the oxidative decomposition of pyrite to sulfuric acid, the root cause of AMD. Batch and column studies were employed to investigate the ability of phospholipids to reduce AMD over an extended period of time (up to 3 years). In studies that used actual coal mining refuse, which contained significant amount of pyrite, it was shown that the rate of acid production from pyrite decomposition could be reduced by as much as 70% due to the presence of surface bound phospholipid. Assembly of the phospholipid into a bilayer motif on the sulfide surface was hypothesized to form a hydrophobic barrier that kept dissolved O2 and bacteria from facilitating the oxidation of FeS2. Column experiments showed that when water at pH 7 was flowed over the coal mining waste, the effluent had a pH close to 3. In contrast when water at pH 7 was flowed over the pyrite containing waste, which was pretreated with lipid, the effluent had a pH closer to 7, and the total amount of Fe (Fe2+/Fe3+) and SO42- in the effluent waters was also reduced relative to the untreated pyrite containing waste circumstance. These studies showed that the application of phospholipid to pyrite containing coal mining waste could potentially be an environmentally friendly remediation technique. / Chemistry

Acid mine drainage (AMD) is a worldwide environmental problem associated with the mining wastes, generated from active and inactive mining sites from mineral processing activities. AMD is defined as the drainage that occurs as a result of oxidation of sulphide minerals/wastes/tailings when exposed to air and water in the presence of chemolithotrophs namely the Acidithiobacillus sp. AMD is characterised by low pH and increased acidity due to elevated heavy metals and sulphate concentration. The acid production potential was carried out for sulphide minerals such as pyrite and chalcopyrite and copper tailings sample in the absence and presence of bacteria namely Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Acidity was generated in all the cases due to the oxidation of the mineral samples. The oxidation was found to occur at a higher rate in the presence of the bacteria compared to the control samples. Bioremediation experiments were conducted on acid mine water collected from the Ingaldahl Mines, Chitradurga, Karnataka, India, using organic and inorganic substrates. In the experiments with rice husk, complete removal of metal ions from the acid mine water was achieved with an attendant increase in the pH of the acid mine water from 2.3 to 5.5. About 21% of sulphate could be removed using Dsm. nigrificans from acid mine water pretreated with rice husk at pH 5.5 and this was further increased to 40% by the supplementation of organic components. The rice husk filtrate was found to serve as a good growth medium for Dsm. nigrificans. About 96 % of Fe, 75 % of Zn, 92 % of Cu and 41 % of sulphate removal was achieved from the acid mine water of pH 2.4 with a concomitant increase in the pH value by two units after interaction with the tree bark. About 56 % and 71 % of sulphate reduction could be achieved at initial pH values of 4.1 and 5.5 respectively of the acid mine water pretreated with E. tereticornis (Sm) bark, after inoculation with Dsm. nigrificans. The complete removal of Fe2+ and Fe3+, 80% of Zn, 83% of Cu and 62% of sulphate could be removed from acid mine water using fly ash as the substrate with an increase in pH of acid mine water from 2.3 to 7. About 68% of sulphate reduction at pH 6.8 could be achieved in acid mine water pretreated with fly ash in the presence of Dsm. nigrificans. With red mud as the substrate, complete removal of all the metal ions namely Fe2+, Fe3+, Zn, and Cu from acid mine water was achieved with a concomitant increase in the pH from 2.3 to 8. The sulphate reduction was increased to about 51% at pH 7.2 when the acid mine water pretreated with red mud was inoculated with Dsm. nigrificans. The adsorption experiments carried out on the acid mine water using either organic or inorganic substrates indicated that the free energy of adsorption was negative for all the chosen metal ions attesting to favorable interaction. The adsorption isotherms of the metal ions for rice husk exhibited Langmuirian behaviour, while those for the other substrates adhered to both Langmuir and Freundlich relationships. The adsorption process was found to be endothermic in nature for rice husk, fly ash and red mud. On the contrary, the adsorption onto tree bark showed exothermic behaviour. The adsorption kinetics of the metal ions onto the various substrates adhered to the first order Lagergren equation. The metal uptake processes by the organic and inorganic substrates chosen for this study involve ionic, chemical and physical forces of adsorption. The different types of functional groups present on the surface of the substrates such as carboxyl, hydroxyl and carbonyl, as revealed by FTIR spectroscopic studies, partake in metal binding. The metal ions will also be adsorbed by complexing with the negatively charged reaction sites on the substrate surfaces. Furthermore, the complex solution chemistry of the metals as a function of pH has also to be taken into consideration. The mechanism of sulphate reduction by Dsm. nigrificans in the presence of organic carbon can be illustrated as: 2CH2O + SO42- + 2H+  2CO2 + 2H2O + H2S M2 + H2S  MS  + 2H+ where, CH2O represents the organic matter and M represents the metal ion.

No description available.

No description available.