Aplicación de residuos de combustión del carbón para el autosellado de balsas mineras productoras de drenaje ácido de mina

163 páginasTesis Doctoral (Lectura 13/12/2013). Directores: Dr. Jose Miguel Nieto Liñán (Universidad de Huelva) y Dr. Rafael Pérez López (Universidad de Huelva). Tribunal: Carlos Ayora Ibáñez (presidente); Acero Salazar, Patricia (vocal); Morales Ruano, Salvador (vocal); Asta, María del Pilar (vocal); Olías Álvarez, Manuel (secretario). El principal objetivo y aportación de la tesis doctoral es la búsqueda de una solución sostenible y atractiva para el tratamiento simultáneo de cenizas volantes de combustión del carbón y lodos de flotación productores de drenaje ácido de mina en la Faja Pirítica Ibérica. Con este propósito, se realizó una caracterización previa del comportamiento de ambos residuos bajo condiciones de meteorización. Posteriormente, se propuso una estrategia de tratamiento directamente en el campo basada en la adición de una cobertera alcanina de cenizas volantes sobre los lodos de flotación en dos parcelas experimentales a escala piloto. El resultado final del sistema de tratamiento es la disminución de la tasa de oxidación de los sulfuros contenidos en el lodo minero y la atenuación de la liberación de elementos potencialmente contaminantes al medioambiente.The main objective and contribution of the Doctoral Thesis is the search for a sustainable and attractive solution for the simultaneous treatment of fly ash from coal combustion and flotationtailings producing acid mine drainage in the Iberian Pyrite Belt. With this purpose,a previous characterization of the behaviour of both wastes under weathering conditions was carried out. Then, it was proposed a strategy for the treatment directly in the field based on the addition of an alkaline cover of fly ash on top ofthe flotation tailings in two pilot-scale experimental plots. The final result of the treatment system is the decrease of the oxidation rate of the sulphides contained in the mining tailings and the attenuation of the release of potentially pollutant elements to the environment

Potential release and bioaccessibility of metal/loids from mine wastes deposited in historical abandoned sulfide mines

This study deals with the potential release of metal/loids from sulfide mine wastes upon weathering and the health risks associated with their accidental ingestion. To address this, a complete chemical and mineralogical characterization of a variety of sulfide mine wastes was performed alongside a determination of metal/loid bioaccessibility through leaching tests simulating human digestive and lung fluids. The mine wastes consisted predominantly of Fe (35–55% of Fe2O3) and exhibited high concentrations of trace metalloids such as As (382–4310 mg/kg), Pb (205–15,974 mg/kg), Cu (78–1083 mg/kg), Zn (274–1863 mg/kg), or Sb (520–1816 mg/ kg). Most wastes with high concentrations of soluble compounds are considered hazardous according to the European regulations due to the exceedance of threshold values for As, Pb, Cr, Cu, Sb, sulfates, and Zn determined by standardized tests. In general terms, the absorption of waste-hosted metals through both digestive and respiratory routes was low compared to the total metal contents of the wastes, with values below 8% of the total concentration in wastes for most metal/loids including Cu, Zn, As, Cd, Tl, or U. However, some metals exhibited a significantly higher absorption potential, especially through the respiratory route, reaching values of up to 17% for Cr and 75% for Pb, highlighting the strong bioaccessibility of Pb in certain sulfide wastes. Despite the high metal/loid concentrations observed in the studied wastes, a health risk assessment indicated that some noncarcinogenic effects could be observed in children only following the accidental digestion of Pb.This work was supported by the Spanish Ministry of Economy and Competitiveness under the research project TRAMPA (MINECO; PID2020-119196RB-C21). C.R C´anovas thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC2019-027949-I. BCL, AAB and TGB were supported by projects PG2018-096608-B-C21 from the Spanish Ministry of Science and innovation (MINECO) and P20-00366 (Ministry of Economy, Knowledge, Business and Universities, Regional Government of Andalusia, Spain). We would also like to thank to the Editor Dr. Hefa Cheng and five anonymous reviewers for the support and comments that notably improved the quality of the original paper. Funding for open access charge: Universidad de Huelva / CBUA

Hydrochemical performance and mineralogical evolution of a dispersed alkaline substrate (DAS) remediating the highly polluted acid mine drainage in the full-scale passive treatment of Mina Esperanza (SW Spain)

Acid mine drainage remediation is an unresolved matter in abandoned mining districts around the world. Development and implementation of passive treatment systems in these areas are commonly focused on engineering and water quality aspects. Neoformed mineral phases precipitated within the reactive material of these passive treatments account for the removal of pollutants but also can cause clogging and passivation of the reactive substrate. After 20 months of operation and monitoring, the limestone-based passive treatment system implemented in Mina Esperanza (SW Spain) was sampled to study the relationship between water chemistry, mineral composition of the neoformed precipitates, and treatment performance. Water chemical profiles show the existence of three precipitation zones controlled by Fe, Al, and Zn hydrochemistry and also a migration with time of precipitation zones downward into the reactive material. These precipitation zones were also confirmed by a mineral study performed on the solid samples where either schwertmannite and goethite or hydrobasaluminite and Zn-rich green rust were the mineral phases that controlled the metal removal in the three precipation (Fe, Al, or Zn) zones. Iron and Al precipitates were observed to play a critical role in the time evolution of the reactive material hydraulic conductivity. Furthermore, Al precipitates passivated to some extent the limestone grains by armoring, although migration of the Fe precipitation zone and Al redissolution later activated the limestone grains. A higher proportion of limestone in the reactive mixture and the addition of new reagents to the bottom section of the reactive material (to enhance the reducing environment and to promote divalent metal removal) are proposed on the basis of this hydrochemical and mineralogical study for a future design for the Mina Esperanza passive treatment system.We gratefully acknowledge Mari Paz Martín, Rafael Carrasco and María José Ruíz, and Cristobal Cantero (Central Research Services of the University of Huelva) for assistance in XRD, ICP-OES, and EPMA, respectively. This study was funded by the Spanish Ministry of Science and Technology through the projects CTM200766724-C02/TECNO and CTM2010-21956-C02 and by the Environmental Council of the Andalusia Regional Government. M.A.C. was financially supported by the Spanish Government with a FPU Ph.D. fellowship. We also thank Richard Wilkin (Associate Editor), Charles Cravotta, and one anonymous reviewer for their comments that significantly improved the quality of this paper.Departamento de Ingeniería Minera, Mecánica, Energética y de la Construcció