Mining for silver, lead, zinc, and copper in Zimapan, Hidalgo State, Mexico has been ongoing since 1576. Unsecured tailings heaps and associated acid mine drainage have presented problems related to soil quality, water quality, and dust emission control in the Zimapan area. Objectives of the study of the mine tailings are (1) to determine mineralogy of the tailings in order to identify acid-producing minerals and heavy metals at risk for release in acidic conditions, and (2) to quantify carbonate minerals and (3) to determine heavy metal content that may be released by the products of sulfide mineral weathering. Representative mine tailings have been sampled from a site located north of Zimapan. Mineralogical characterization has been conducted with X-ray diffraction (XRD), and scanning and transmission electron microscopes (SEM and TEM). Total carbonates have been determined the Chittick procedure. X-Ray Fluorescence (XRF) has been utilized to determine total elemental composition. XRD and SEM analyses have confirmed the presence of pyrite and arsenopyrite indicating a potential for acid mine drainage. Calcite has been confirmed to have a significant presence in the unweathered samples by XRD and the Chittick procedure, with some samples containing an average of 19.4% calcite. NAA and XRF have revealed significant concentrations of toxic elements such as As, Pb and Zn in both the oxidized and unoxidized samples.

The oxidation of ferrous in acidic sulfate media by dissolved oxygen is an important reaction in any sulfide mineral leach process that uses ferric as a surrogate oxidant. Ferric is reduced as it oxidizes metal sulfides, and the resulting ferrous is re-oxidized by dissolved oxygen. The oxidation of ferrous to ferric by dissolved oxygen is quite slow outside of elevated pressure-temperature autoclaves. However, pyrite in solution has been found to have a catalytic effect on the reaction, speeding it up significantly. This effect is particularly significant in the context of the Galvanox™ acidic sulphate atmospheric leach process. To quantify the kinetics of this reaction and the effect of pyrite, tests were run in an atmospheric batch reactor with constant tracking of pH and redox potential. The kinetics of this reaction were quantified with respect to primary variables such as acidity, pyrite pulp density, temperature, and total iron concentration. Secondary factors such as copper concentration, gas liquid mixing rate and the source of pyrite mineral were also considered. Redox potential is a logarithmic function of the ratio of the activity of free ferric to free ferrous and is complicated by speciation within the Fe(III)-Fe(II)-H₂SO₄-H₂O system. Correlating redox potential data with extent of reaction was achieved by using permanganate redox titration and the isokinetic technique to link redox potential data directly to the fraction of ferrous reacted. This technique is effective over the potential range of interest – 360 to 510 mV vs Ag/AgCl. Under these conditions the leaching rate of pyrite is appreciable, so the rate of pyrite dissolution was predicted with the shrinking sphere model developed by Bouffard et al. Ferrous oxidation in solution was simulated with an adjusted version of the model of Dreisinger and Peters, which also accounts for the catalytic effect of dissolved copper. Oxygen solubility was predicted using the model of Tromans. Experimental data show a clear enhancing effect of pyrite on ferrous oxidation. A mathematical model of this effect applicable to the conditions of Galvanox™ leaching is presented.

Thèse de doctorat : cGéosciences de l'environnement : Vandoeuvre-les-Nancy, INPL : 2005. / Titre provenant de l'écran-titre. Bibliogr.

The oxidation of ferrous in acidic sulfate media by dissolved oxygen is an important reaction in any sulfide mineral leach process that uses ferric as a surrogate oxidant. Ferric is reduced as it oxidizes metal sulfides, and the resulting ferrous is re-oxidized by dissolved oxygen. The oxidation of ferrous to ferric by dissolved oxygen is quite slow outside of elevated pressure-temperature autoclaves. However, pyrite in solution has been found to have a catalytic effect on the reaction, speeding it up significantly. This effect is particularly significant in the context of the Galvanox™ acidic sulphate atmospheric leach process. To quantify the kinetics of this reaction and the effect of pyrite, tests were run in an atmospheric batch reactor with constant tracking of pH and redox potential. The kinetics of this reaction were quantified with respect to primary variables such as acidity, pyrite pulp density, temperature, and total iron concentration. Secondary factors such as copper concentration, gas liquid mixing rate and the source of pyrite mineral were also considered. Redox potential is a logarithmic function of the ratio of the activity of free ferric to free ferrous and is complicated by speciation within the Fe(III)-Fe(II)-H₂SO₄-H₂O system. Correlating redox potential data with extent of reaction was achieved by using permanganate redox titration and the isokinetic technique to link redox potential data directly to the fraction of ferrous reacted. This technique is effective over the potential range of interest – 360 to 510 mV vs Ag/AgCl. Under these conditions the leaching rate of pyrite is appreciable, so the rate of pyrite dissolution was predicted with the shrinking sphere model developed by Bouffard et al. Ferrous oxidation in solution was simulated with an adjusted version of the model of Dreisinger and Peters, which also accounts for the catalytic effect of dissolved copper. Oxygen solubility was predicted using the model of Tromans. Experimental data show a clear enhancing effect of pyrite on ferrous oxidation. A mathematical model of this effect applicable to the conditions of Galvanox™ leaching is presented.

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 2001. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Οι σύγχρονοι ρυθμοί ανάπτυξης και εξέλιξης του ανθρώπου και της κοινωνίας του διαταράσσουν τις δυναμικές ισορροπίες που επικρατούν στο περιβάλλον, με αποτέλεσμα την αποσταθεροποίηση των εδαφών και κατ’ επέκταση τη διάβρωση και ερημοποίηση τους. Αυτή η διαταραχή μπορεί να μετατρέψει ένα απαραίτητο θρεπτικό ανόργανο σε ρυπαντή λόγο την υπερβολικά μεγάλης διαθεσιμότητας του. Στην προσπάθεια του ο άνθρωπος να επαναφέρει το περιβάλλον την πρότερη κατάσταση του έχει εφαρμόσει διάφορες φυσικές και τεχνικές μεθόδους απομάκρυνσης των ρύπων και σταθεροποίησης των εδαφών. Σε αυτή την μεταπτυχιακή διατριβή μελετήθηκε μια πειραματική καλλιέργεια ηλίανθου, Helianthus annnus και H. giant, με στόχο να εξαχθούν χρήσιμα συμπεράσματα για την προστασία του περιβάλλοντος. Χρησιμοποιήθηκαν υποβαθμισμένα εδάφη διαφορετικής σύστασης (φρύγματα σιδηροπυρίτη, μηλαϊκή γη και γύψος σε διάφορες αναλογίες) και μελετήθηκε ο βαθμός ανάπτυξης των ηλίανθων σε σχέση με αυτά τα υποστρώματα. Τα αποτελέσματα των μετρήσεων έδειξαν ότι ο βαθμός ανάπτυξης των φυτών ανάλογα με την ποιότητα του υποστρώματος είναι ικανοποιητικός ανεξάρτητα από την σύσταση του, επιτρέποντας τα φυτά να ολοκληρώσουν τον βιολογικό τους κύκλο χωρίς να παρουσιάζονται συμπτώματα χλώρωσης. Αξίζει να σημειωθεί ότι τα υποστρώματα με προσθήκη γύψου έδωσαν κοντύτερα φυτά σε σχέση με αυτά που είχαν μηλαϊκή γη που έδωσαν τα πιο ψηλά φυτά. / Man and his modern rythms of growth and development disturb the dynamic balances that prevail in the environment, as a result the destabilisation, the erosion and the desertation of the soil. This disturbance can change an essential nutritious element to a polluter because of the excessively big availability. In the effort to restore the environment at previous situation man has applied various natural and technical methods to remove of pollutants and stabilize the soil. In this postgraduate thesis was studied a experimental culture of sunflower, Helianthus annnus and H. giant, in order to exported useful conclusions on the protection of environment. It was used downgraded soil of different constitution (burned pyrite, coarse ground and plaster in various proportions) and was studied the degree of growth of sunflowers. The results of measurements showed that the degree of growth of plants depending on the quality of sublayer, was satisfactory independent from its constitution, allowing the plants to complete their biological circle without symptoms of chlorination. It has to be mentioned that sublayers with addition of plaster gave shorter plants compared to coarse ground which gave the tallest plants.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.

The depositional environment that existed during the accumulation of Devonian - Mississippian black shales of the eastern US has been a topic of debate in recent decades. In this study, pyrite framboid size distribution was evaluated for four cores from the Devonian outcrop belt of central Kentucky to determine the role that anoxic-euxinic conditions may have played in the accumulation of these black shales. For samples from the Appalachian Basin, pyrite framboid size distributions suggest that the Sunbury Shale and the upper part of the Huron Shale Member of the Ohio Shale were deposited under predominantly euxinic conditions, whereas the lowermost part of the Huron Member and the Cleveland Member of the Ohio Shale were deposited under predominantly dysoxic to oxic conditions. For samples from the Illinois Basin, pyrite framboid size distributions suggest that the Clegg Creek and the Morgan Trail members of the New Albany Shale indicate dysoxic to oxic conditions were present, whereas data for the Camp Run Member suggest the sediments were deposited during repeated intervals of euxinic deposition followed by predominant dysoxic - oxic conditions which allowed development of the bioturbated fabric seen in these gray shales. These results are not completely in agreement with previous research that utilized C-S-Fe and trace element relationships to establish depositional conditions during organic-rich sediment accumulation. For example, previous research has indicated that the Cleveland Member of the Ohio Shale and the Clegg Creek Member of the New Albany Shale were deposited under euxinic conditions. Reasons for these differences in interpretation may include syngenetic and diagenetic processes including winnowing of framboids in the depositional environment and atypical growth of the framboids.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.