Caracterização tecnológica do minério aurífero de Riacho dos Machados - MG para fins de cianetação e estudo da utilização de agentes oxidantes na lixiviação

Este trabalho consistiu na caracterização tecnológica do minério primário de Riacho dos Machados (MG) para fins de seu tratamento por métodos de lixiviação por solução cianetada. O minério foi sujeito às seguintes etapas de estudo: (1) extração do ouro/prata por cianetação, em diferentes frações granulométricas para avaliar o grau de exposição do ouro cianetável, (2) ensaios de bottle roll test da cinética de extração do ouro em minério britado e moído e (3) comparação do desempenho de lixiviação em função do agente oxidante adicionado (ar, oxigênio e peróxido de hidrogênio) em condições ambiente. Os ensaios foram realizados em escala de laboratório. A amostra de minério estudada apresentou teores na faixa de 7 ppm de ouro e 2 ppm de prata. Os metais preciosos encontram-se na forma de partículas microscópicas e submicroscópicas. A extração máxima de ouro obtida foi de 90%. O uso de oxigênio e peróxido de hidrogênio adicionados à polpa representou um incremento apreciável na velocidade de dissolução do ouro.This work evaluates the behavior in the cyanide leaching of primary gold ore from Riacho dos Machados (MG), central Brazil. This deposit belongs to Cia. Vale do Rio Doce. It was studied: (1) the extraction of gold/silver in different ore size to determine the liberation of precious metais, (2) the rate of extraction in bottle roll test with crushed and ground ores and (3) the effect of oxidants addition (air, oxigen and hydrogen peroxid) on gold/silver leaching at atmosphere pressure. The experiments were carried out in laboratory scale. The ROM ore had about 7 ppm of gold and 2 ppm of silver. The gold/silver particles had microscopic and submicroscopic sizes and in the leaching of ore of gold extraction was obtained 90%. The use of oxygen and hydrogen peroxide mixed with air increase the rate of gold dissolution

Evaluation of Soil Re-mineralizer from By-Product of Volcanic Rock Mining: Experimental Proof Using Black Oats and Maize Crops

This study was focused on physical, petrographical, mineralogical, and chemical characterization of a volcanic-rock mining by-product (dacite rock), as well as on greenhouse experiment with black oats and maize crops to evaluate the potential use of the by-product as soil re-mineralizer. The by-product sample was obtained from a quarry in the Nova Prata mining district in southern Brazil. The particle size distribution of the by-product and soil was determined by sieving. Dacite rock petrographic description was performed on a polished thin section by optical microscopy. The soil and dacite rock mineralogical phases were identified by X-ray diffraction. The by-product and soil chemical composition was determined by X-ray fluorescence. Inductively coupled plasma mass spectrometry was performed to determine potentially toxic elements, As, Cd, Hg and Pb in by-product. Additional chemical compositions of the by-product and soil were analyzed using a scanning electron microscope equipped with an energy dispersive X-ray detector. Black oats and, sequentially maize, crops were cultivated in a typical Hapludox soil treated with the by-product in a greenhouse. Five by-product doses (0, 906, 1813, 3625, and 7251 kg ha−1) were added into pots containing soil, each with seven replications. Responses to treatments were evaluated from dry matter production, nutritional status of the crops, and in the changes in soil properties after 70 days of each cultivation. The results showed that the by-product is composed of plagioclase, K-feldspar, quartz, clinopyroxene, smectites, and opaque minerals with apatite as accessory mineral. The addition of 3625 and 7251 kg ha−1 doses of the by-product substantially increased the dry matter yield in maize leaves. The Ca uptake by maize leaves cultivated in soil with 7251 kg ha−1 dose of the by-product was significantly higher in soil with other doses, and all by-product doses promoted high concentrations of Mg and Ca. The accumulated amounts of Ca, K, Mg and P indicated that they were enough to supply maize nutritional needs. Improvements in soil properties, such as high levels of Ca, K and P and low levels of exchangeable Al and Al saturation were observed. The results of the study suggest that the by-product can be used as soil re-mineralizer. The dacite rock by-product studied here has potential to be an environmental solution to soil fertilization problem because it does not require chemical processing and can be used as it is mined

Caracterização tecnológica do minério aurífero de Riacho dos Machados - MG para fins de cianetação e estudo da utilização de agentes oxidantes na lixiviação

Este trabalho consistiu na caracterização tecnológica do minério primário de Riacho dos Machados (MG) para fins de seu tratamento por métodos de lixiviação por solução cianetada. O minério foi sujeito às seguintes etapas de estudo: (1) extração do ouro/prata por cianetação, em diferentes frações granulométricas para avaliar o grau de exposição do ouro cianetável, (2) ensaios de bottle roll test da cinética de extração do ouro em minério britado e moído e (3) comparação do desempenho de lixiviação em função do agente oxidante adicionado (ar, oxigênio e peróxido de hidrogênio) em condições ambiente. Os ensaios foram realizados em escala de laboratório. A amostra de minério estudada apresentou teores na faixa de 7 ppm de ouro e 2 ppm de prata. Os metais preciosos encontram-se na forma de partículas microscópicas e submicroscópicas. A extração máxima de ouro obtida foi de 90%. O uso de oxigênio e peróxido de hidrogênio adicionados à polpa representou um incremento apreciável na velocidade de dissolução do ouro.This work evaluates the behavior in the cyanide leaching of primary gold ore from Riacho dos Machados (MG), central Brazil. This deposit belongs to Cia. Vale do Rio Doce. It was studied: (1) the extraction of gold/silver in different ore size to determine the liberation of precious metais, (2) the rate of extraction in bottle roll test with crushed and ground ores and (3) the effect of oxidants addition (air, oxigen and hydrogen peroxid) on gold/silver leaching at atmosphere pressure. The experiments were carried out in laboratory scale. The ROM ore had about 7 ppm of gold and 2 ppm of silver. The gold/silver particles had microscopic and submicroscopic sizes and in the leaching of ore of gold extraction was obtained 90%. The use of oxygen and hydrogen peroxide mixed with air increase the rate of gold dissolution

Avaliação de resinas de troca iônica para emprego na hidrometalurgia de minérios auríferos

O emprego de resinas trocadoras de íons na adsorção de ouro dissolvido em soluções cianetadas, típicas de processos hidrometalúrgicos de cianetação de minérios auríferos foi avaliada para alguns tipos de resina com propriedades base fraca de estrutura macroporosas e fibrosas. Três tipos de resinas receberam um maior aprofundamento de estudo em referência ao desempenho de extração do Au(CN)2- e cianocomplexos de Ag, Ni, Cu, Fe e Hg: (1) resinas Hypersol Macronet produzidas pela Purolite, Inglaterra, (2) resina Fiban (AK22) em base a material fibroso tecido na forma de manta produzidas por Ecofil-Delco, Bielorussia, e (3) resina em base a grupo piperazina (em fase de desenvolvimento) sintetizada nos laboratórios do Departamento de Química Orgânica do Instituto de Ciências Weizmann, Israel. Este trabalho contém ao final alguns resultados iniciais dos trabalhos de avaliação com resinas impregnadas, resinas protótipos e resinas comerciais, com características e propriedades potencialmente de interesse à hidrometalurgia de minérios auríferos. As principais características e propriedades avaliadas foram: pKa, carregamento, seletividade, cinética e eficiência de eluição. Os testes foram realizados em escala de laboratório, utilizando predominantemente soluções sintéticas e lixívias minerais de amostras de minérios brasileiros. Os resultados deste estudo mostraram a potencialidade do uso de resinas base fraca para extração de ouro em solução principalmente quanto aos aspectos de carregamento, seletividade e eluição. Estes comportamentos podem ser determinados pela combinação de fatores, tais como: a) propriedade ácido-base do grupo funcional, b) balanço do grau de hidrofobicidade da matriz polimérica e c) alta área superficial da resina. Não foram obtidos comportamentos ideais de extração de ouro frente a pH moderadamente alcalino, mas os resultados se aproximaram àqueles esperados quando empregados grupo funcional de alto pKa, como para a resina-piperazina ou guanidina. Por outro lado ganhos de eficiência em capacidade de carregamento em ambientes alcalinos podem ser alcançados com a introdução de grupos amina base forte, como observado para resinas Hypersol Macronet. A resina fibrosa AK22 demonstrou interessante comportamento seletivo em função da faixa de pH na extração dos cianocomplexos de ouro (pH11).The use of ion exchange resins for gold recovery from typical cyanide leach solutions in hydrometallurgy process was evaluated for some weak base resins with macroporous and fibrous structure. More extensive investigations were carried out on three types of resins, respect their performance of Au(CN)2- and cyanide complexes of Ag, Ni, Cu, Fe e Hg extraction: (1) Hypersol Macronet resin made from Purolite, England, (2) Fibrous resin Fiban (AK22) textile form as mantle made from Ecofil-Delco, Bielorussian, and (3) resin with piperazin functional group (development stage) sintetized in the laboratory of Department of Organic Chemistry of Weizmann Cientific Institute, Israel. This work also presents some initial results about the evaluation in other resins with potential interest to gold hydrometallurgy. To evaluate which resins might show promising results determined characteristics and proprieties were measured as: pKa, loading, selectivity, kinetic and elution efficiency. For experimental measurement, small-scale dynamic contacts between resin and metal-cyanide complexes were effected, used both synthetic and real cyanide solutions, the last obtained from the leaching of a gold mineral ore from Brazil. Resins with a weak base functionality show promising results when applied to the extraction of goldcyanide from cyanide media mainly in terms of loading, separation and stripping factors. These behaviours can be determined by the combination of factors, among then the following could be pointed out: a) the suitable functional group’s acid-base properties, b) the balanced degree of hydrophobicity of the polymer matrix and c) the high surface area of the resin. The best results of gold extraction weren’t yet achieved in moderately alkaline pH values, but results are close to those expected when functionalised with groups as piperazine or guanidine extracting, are empoyed. n the other hand, gains in loading efficiency, independently of pH, were reach with the introduction a few percent the strong amino groups in resin, as Hypersol Macronet. Fibrous resin AK22 presented the interesting selectivity behaviour between gold and mercury cyanide where the gold was extract at pH11

Soybean crops cultivated with dacite rock by-product: a proof of a cleaner technology to soil remineralization

Peer ReviewedPostprint (author's final draft

Propagation of the gasoline compounds in the soil: 1. unsaturated zone

Esse trabalho descreve o estudo da propagação de tolueno na zona não saturada do solo. Mostram-se o procedimento experimental desenvolvido em colunas de laboratório, os resultados experimentais obtidos, uma análise dos resultados aplicando-se modelagem matemática, a análise estatística aplicada ao denominado modelo de puffs de simulação da dispersão e uma discussão do prosseguimento desse trabalho.This work describes the study of the propagation of toluene in the unsaturated zone of the ground. It is shown the experimental procedure in laboratory columns. The gotten experimental results and their analysis with a mathematical modeling are shown. Also is shown an analysis statistics applied to the called the puffs’ models of the dispersion simulation and a quarrel of the continuation of this work

Propagation of the gasoline compounds in the soil: 1. unsaturated zone

Esse trabalho descreve o estudo da propagação de tolueno na zona não saturada do solo. Mostram-se o procedimento experimental desenvolvido em colunas de laboratório, os resultados experimentais obtidos, uma análise dos resultados aplicando-se modelagem matemática, a análise estatística aplicada ao denominado modelo de puffs de simulação da dispersão e uma discussão do prosseguimento desse trabalho.This work describes the study of the propagation of toluene in the unsaturated zone of the ground. It is shown the experimental procedure in laboratory columns. The gotten experimental results and their analysis with a mathematical modeling are shown. Also is shown an analysis statistics applied to the called the puffs’ models of the dispersion simulation and a quarrel of the continuation of this work

Ion exchange resins for gold cyanide extraction containing a piperazine functionality, 1 : synthesis and physico-chemical properties

The synthesis of two types of metal-chelating resins incorporating gold-specific piperazine groups is described. PS-PIP is a styrene-divinylbenzene macroporous network. MC-PIP is a (glycidyl methacrylate)-co-(ethylene dimethacrylate) network. The nominal functional group concentrations are 1.84 mmol/g for PS-PIP and 1.14 mmol/g for MC-PIP. The proton exchange capacity is 1.95 mmol/g for PS-PIP and 0.91 mmol/g for MC-PIP. Accurate titration curves were used to determine pKa values (pKH = 7.05 ± 0.12). XPS analyses of PS-PIP resin were followed as a function of pH (cf. Fig. 8) demonstrating that the protonation of the amine is observable by a shift in binding energy of the N (1s) peak (±1.6 eV) moving from tertiary amine form (N (1s) 399.7 eV) to the protonated tertiary amine form (N (1s) 401.3 eV). Additionally, the presence of quaternary ammonium groups was detected at a N (1s) peak at 402.3 eV (cf. Fig. 9). Metal extraction from cyanide solutions, including Brazilian mine leach solution, showed considerable preference for gold (cf. Fig. 11–12). The piperazine resins extract gold via two mechanisms: (a) ligand substitution reactions at pH > 7.05 (pKH(a)) or (b) anion exchange reactions via the quaternary ammonium groups at high pH values. Extraction profiles were S-shaped (cf. Fig. 10) with 50% extraction ability at pH 8.0. Cyclic experiments involving extraction, elution, regeneration and recomplexation (cf. Tab. 6 and 7) showed the ability of MC-PIP to perform consistently at high extraction efficiencies from pH 8.6