Characterisation and valorisation of materials from a copper metallurgical complex
Atlantic Copper is a Spanish company whose metallurgical complex is in Huelva. It is one of the biggest manufacturers of copper cathodes in Europe and accounts for 8.5 % of the province’s GDP. Using the most advanced technologies, they produce high-purity copper cathode (> 99.99 %). This comp...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universidad de Huelva (UHU) |
| Repositorio: | Arias Montano. Repositorio Institucional de la Universidad de Huelva |
| Idioma: | inglés |
| OAI Identifier: | oai:ariasmontano.uhu.es:10272/27541 |
| Acceso en línea: | https://hdl.handle.net/10272/27541 |
| Access Level: | acceso abierto |
| Palabra clave: | Inorganic wastes Valorisation Characterisation Metals recovery Copper metallurgy Residuos inorgánicos Valorización Caracterización Recuperación de metales Metalurgia del cobre 2303.18 Metales 2391 Química Ambiental 3308 Ingeniería y Tecnología del Medio Ambiente 3308.02 Residuos Industriales |
| Sumario: | Atlantic Copper is a Spanish company whose metallurgical complex is in Huelva. It is one of the biggest manufacturers of copper cathodes in Europe and accounts for 8.5 % of the province’s GDP. Using the most advanced technologies, they produce high-purity copper cathode (> 99.99 %). This company is framed within a circular economy strategy carrying out the management of by-products, intermediate materials, and waste to reduce the environmental impact of its operations as much as possible and, turn in, reduce the associated costs. The central goal of this doctoral thesis has been to evaluate and develop possible valorisation lines for different wastes and secondary materials generated in the manufacture of high-purity cathodes. The studied materials were sludge scrubber (SS), sludge from converters (SC), electrolyte sludge (ES), and copper wastewater sludge (CWS). For that purpose, first, an exhaustive characterisation was carried out to determine chemical composition, mineral phases, particle sizes, microstructure, and pollutants' mobility. Considering the characterisation results and the literature consulted, potential applications were identified and evaluated. After, different valorisation lines were selected for each studied material based on its characteristics and properties. The studies carried out to SS and SC showed that both sludges were mainly composed of Pb (> 20 % w/w) mainly as anglesite, and the SS also contained a high concentration of Se (> 30 % w/w) as metallic selenium. Therefore, these wastes could be an important secondary source of Se and Pb. Thus, Se recovery by roasting process and Pb recovery by hydrometallurgy process were proposed. Se-Pb recovery could have remarkable environmental benefits in contrast to its disposal in landfill, as well as a reduction in its management cost. On the other hand, ES presented a high Cu concentration (≈ 50 % w/w) as domeykite (Cu3As), cuprite (Cu2O), Cu metal and copper sulphate hydrate (CuSO4∙xH2O) and also a high As concentration (≈ 10 % w/w), mainly as Cu3As. Therefore, this material could be an important secondary source of Cu. However, As content should be removed for avoiding problems in reprocessing or valorisation. For the Cu recovery, ES dissolution was chosen, which was achieved using an acid medium, H2SO4 (1.4 M)/HNO3 (1.8 M), and a solid-to-liquid ratio of 1:20 g/mL. Subsequently, two lines of research were carried out: a) Arsenic removal from the ES solution by precipitation with iron, and then copper recovery from the arsenic-free solution; b) Copper recovery from the ES solution by an evaporative crystallisation, and then arsenic precipitation. In the first line of research, As was removed from ES solution by precipitation as iron (III) arsenate, with high efficiency (> 70 %). However, about 50 % of Cu was also co-precipitated with the As, suggesting copper should previously recover. In the second line of research, more than 90 % of the Cu contained in the sludge was recovered as very pure copper sulphate (≥ 99.5 % w/w) by an evaporative crystallization process. Moreover, around 70 % of the As was removed during this process as As2O3 (> 99 % w/w). Therefore, this process was considered an effective way to recover Cu and remove the As contained in ES. On the other hand, CWS presented a high concentration of CaO (≈ 70 % w/w) and, in a minor proportion, contained SiO2, Fe2O3, MgO, SO3 (15‒1 % w/w) and Al2O3 (≈ 0.4 % w/w). In addition, CWS presented As (≈ 3.4 % w/w) and other elements such as Ba, Cu, Pb, Sb, Sr, and Zn in traces concentration (< 1 % w/w). This material contained several mineral phases: calcite (CaCO3), gypsum (CaSO4∙2H2O), portlandite (Ca(OH)2), and iron oxide hydroxide (Fe21O31(OH)). For CWS, the proposed valorisation and/or immobilisation line was to use it as raw material in geopolymer materials. The geopolymers obtained had an excellent compressive strength (50‒20 Mpa), these values were considered admissible for construction applications. Only the highest compact paste (CWSs10) leached 2 mg/kg of As, this value coincides with the threshold limit established for the admission of non-hazardous waste landfills --------------------------------------------------------------------------------------------------------- |
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