Hydrothermal and supergene uranium mineralization at the Osamu Utsumi mine, Poços de Caldas, Minas Gerais, Brazil

Waber, Niklaus; Schorscher, H.D.; Peters, T. J.

doi:10.1016/b978-0-444-89934-7.50006-2

Cited by 10 publications

(42 citation statements)

References 18 publications

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“…In addition to retarding the transport of U in contaminated soil and groundwater, sorption reactions also affect the formation of sediment-hosted U deposits. For example, U(VI) is trapped in the oxidised sandstone above the redox front in the Osamu Utsumi uranium deposit in Brazil (Read, 1992;Waber et al, 1992) and in the Nopal I deposit in Mexico (Prikryl et al, 1997). Sorption of U(VI) by iron (hydr)oxides also retards its mobility during the oxidative weathering of ore deposits (Murakami et al, 1997;von Gunten et al, 1999;Allard et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Surface complexation of U(VI) on goethite (α-FeOOH)

Sherman

Peacock

Hubbard

2008

Geochimica et Cosmochimica Acta

196

163

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Sorption of U(VI) to goethite is a fundamental control on the mobility of uranium in soil and groundwater. Here, we investigated the sorption of U on goethite using EXAFS spectroscopy, batch sorption experiments and DFT calculations of the energetics and structures of possible surface complexes. Based on EXAFS spectra, it has previously been proposed that U(VI), as the uranyl cation UO 2 2þ , sorbs to Fe oxide hydroxide phases by forming a bidentate edge-sharing (E2) surface complex, >Fe(OH) 2 UO 2 (H 2 O) n . Here, we argue that this complex alone cannot account for the sorption capacity of goethite (a-FeOOH). Moreover, we show that all of the EXAFS signal attributed to the E2 complex can be accounted for by multiple scattering. We propose that the dominant surface complex in CO 2 -free systems is a bidentate corner-sharing (C2) complex, (>FeOH) 2 UO 2 (H 2 O) 3 which can form on the dominant {101} surface. However, in the presence of CO 2 , we find an enhancement of UO 2 sorption at low pH and attribute this to a (>FeO)CO 2 UO 2 ternary complex. With increasing pH, U(VI) desorbs by the formation of aqueous carbonate and hydroxyl complexes. However, this desorption is preceded by the formation of a second ternary surface complex (>FeOH) 2 UO 2 CO 3 . The three proposed surface complexes, (>FeOH) 2 UO 2 (H 2 O) 3 , >FeOCO 2 UO 2 , and (>FeOH) 2 UO 2 CO 3 are consistent with EXAFS spectra. Using these complexes, we developed a surface complexation model for U on goethite with a 1-pK model for surface protonation, an extended Stern model for surface electrostatics and inclusion of all known UO 2 -OH-CO 3 aqueous complexes in the current thermodynamic database. The model gives an excellent fit to our sorption experiments done in both ambient and reduced CO 2 environments at surface loadings of 0.02-2.0 wt% U.

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Section: Introductionmentioning

confidence: 99%

Surface complexation of U(VI) on goethite (α-FeOOH)

Sherman

Peacock

Hubbard

2008

Geochimica et Cosmochimica Acta

196

163

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“…dos elementos-traço, é importante observar elevadas concentrações de mo (270 mg kg -1 ) e Zr (1771 mg kg -1 ). esses elementos são provenientes dos produtos hidrotermais, fazendo parte da geologia local junto com a pirita, a fluorita e os minerais de urânio (Waber et al, 1992) . Alguns elementos de interesse ambiental também estão presentes no estéril em quantidades significativas: As (61,7 mg kg -1 ), ba (668 mg kg -1 ), Pb (258 mg kg -1 ), sr (502 mg kg -1 ), v (336 mg kg -1 ) e Zn (95,2 mg kg -1 ).…”

Section: Análise Química Do Estéril E Dos Agentes Alcalinosunclassified

“…o sulfato deve-se, principalmente, à dissolução de minerais secundários, uma vez que a maior parte do s presente na composição química do estéril encontrase na forma oxidada (so 4 2-) (Figura 3i,j). Já a adição de Ca pelo estéril (C1) resulta, principalmente, da dissolução de carbonatos, fluorita, apatita e de plagioclásios presentes na rocha da região (Waber et al, 1992).…”

Section: Análise Química Do Estéril E Dos Agentes Alcalinosunclassified

“…A presença desse elemento deve-se à ocorrência de pirolusita (mno 2 ) na mina (Waber et al, 1992) (Figura 4c,d). o mn representa uma preocupação na estação de tratamento da mina em questão, pela necessidade de um pH maior que 10 para garantir a sua precipitação (tedeschi, 2005).…”

Section: Análise Química Do Estéril E Dos Agentes Alcalinosunclassified

“…As concentrações má-ximas observadas variaram de 10, 6 a 11,8 mg l -1 . isso se deve à dissolução da esfalerita (Zns) presente no estéril (Waber et al, 1992;souza, 1995).…”

Section: Análise Química Do Estéril E Dos Agentes Alcalinosunclassified

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Avaliação em laboratório do uso de sistemas de coberturas alcalinas para prevenção da drenagem ácida de mina

Abreu¹,

Faria²,

Guimarães³

et al. 2012

Rev. Bras. Ciênc. Solo

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A drenagem ácida de mina (DAM) é um problema ambiental em escala mundial. Ela é proveniente do processo de oxidação química de materiais da mineração que contenham minerais sulfetados expostos a condições atmosféricas com a mediação de bactérias. As águas ácidas geradas nesses ambientes podem comprometer a qualidade dos recursos hídricos. Para tentar conter essa DAM, métodos de prevenção e remediação têm sido aplicados. As coberturas secas têm sido estudadas como alternativa de prevenção, visto que a remediação tem mostrado-se de custo elevado. O objetivo deste trabalho foi avaliar o uso de coberturas alcalinas para controlar a geração de ácido proveniente do estéril da mineração de urânio, U, por meio de sistemas colunas de lixiviação. Para isso, foram estudados sistemas de coberturas que têm como agentes de neutralização a lama vermelha, o calcário e a cal. Amostras de estéril e de água foram coletadas na mina Osamu Utsumi, em Caldas, MG. Foram realizadas análises químicas e mineralógicas do estéril, da cal, do calcário e da lama vermelha. Para os testes cinéticos, foram montadas sete colunas de lixiviação: C1(estéril); C2 (estéril + cobertura de lama vermelha); C3 (estéril + cobertura de calcário); C4 (estéril + cobertura de cal); COB2 (cobertura de lama vermelha); COB3 (cobertura de calcário); e COB4 (cobertura de cal). As amostras lixiviadas foram monitoradas por 100 dias. Os resultados mostraram que a cal e a lama vermelha têm maior potencial neutralizador. No entanto, esses agentes neutralizantes oferecem o inconveniente de introduzir material solúvel no lixiviado. Dessa forma, considerando os parâmetros avaliados, foi demonstrado que o uso de mistura de lama vermelha com estéril do Bota-fora 4 (BF4) pode ser uma alternativa viável para o controle de geração de DAM associada à reciclagem de resíduos industriais alcalinos.

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Structural analysis and geophysical survey for hydrogeological diagnosis in uranium mine, Poços de Caldas (Brazil)

et al. 2019

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The implementation of open pit mines promotes alterations on geological and hydrogeological processes, mainly on natural streamflow patterns. Drainage system tries to reach its equilibrium due to modification on slope profiling water flows through new pathways contributing to erosion and leaching processes. One of the impacts related to mining is the generation of acid mine drainage (AMD), which occurs as a product of sulfide minerals exposure to oxidizing environment and, in contact to water, favors the formation of sulfuric acid. Thus, a low pH promotes a higher mobility of heavy metals and radionuclides, which become a source of contamination. In order to understand the hydrogeological dynamic in rock masses that contribute to AMD production, this paper aimed to subsidize mitigation programs in fractured aquifers using a structural analysis and geophysical survey for the reduction of acid drainage generation. The study was carried at the four mining fronts that compose the mine pit of Osamu Utsumi Mine, named according to its cardinal position (NE, SE, SW and NW). Local structural survey indicated that fractures attitudes are mainly N20E/80NW and N55 W/75NE, with intersections between them. Evidence of water flows, like whitish kaolinite stains and small vegetation growth, was identified in fronts NE, SW and NW, in addition to water springs at the base of the slopes. The flows arise mainly in areas that coincide to intersection between fracture systems in an orthogonal arrangement and the fracturing pattern indicated that at all fronts most of the fracture planes project into the open pit area, which favor the water channeling to the center of the mine as a water catchment basin. Moreover, the relationship between the persistence and spacing among the discontinuities enables a good hydraulic conductivity within the rock masses and the water upwelling on the slopes surface. The geophysical data corroborated with the structural survey, which identified the fracture planes as linear structures associated with low resistivity zones. DC resistivity method showed a strong contrast between saturated zones, differing natural from acidic water. Delimitation of linear features in the inversion models indicated that water flows are channeled through fracture planes and promote an expressive weathering process inside the rock masses, observed at depths of up to 70 m.

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Hydrothermal and supergene uranium mineralization at the Osamu Utsumi mine, Poços de Caldas, Minas Gerais, Brazil

Cited by 10 publications

References 18 publications

Surface complexation of U(VI) on goethite (α-FeOOH)

Surface complexation of U(VI) on goethite (α-FeOOH)

Avaliação em laboratório do uso de sistemas de coberturas alcalinas para prevenção da drenagem ácida de mina

Structural analysis and geophysical survey for hydrogeological diagnosis in uranium mine, Poços de Caldas (Brazil)

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