Biolixiviação do minério de calcopirita pela perspectiva da eletroquímica de semicondutores
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Data
2022-10-14
Autores
Toledo, Ailton Guilherme Rissoni [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A crescente necessidade de cobre, o esgotamento dos recursos mundiais de jazidas de minério de alto teor e o acúmulo ininterrupto de resíduos de minério contendo metais comercialmente valiosos tendem a impulsionar o desenvolvimento de processos hidrometalúrgicos. A hidrometalurgia designa processos mais sustentáveis e de baixo custo para obtenção de recursos metálicos a partir de sua (bio)lixiviação, em que há a possibilidade de processar minérios de baixo teor, substituindo a pirometalurgia. No entanto, a (bio)lixiviação em larga escala de minério de calcopirita, minério de cobre mais abundante disponível na natureza (>70%), ainda não é viável economicamente. Muitos dos minerais de interesse são semicondutores, como a calcopirita, desse modo, entender sua natureza semicondutora em contato com uma solução eletrolítica é crucial para promover a eficiência e a aplicação da biohidrometalurgia em larga escala. No entanto, poucos trabalhos na área de (bio)lixiviação têm considerado a abordagem eletroquímica de semicondutores, em que uma efetiva (bio)lixiviação mineral depende do que ocorre na interface entre o semicondutor e uma solução eletrolítica, bem como em suas fases sólida e líquida. A fim de compreender os processos químicos entre a calcopirita e a solução eletrolítica, uma superfície de resposta capaz de descrever a extração de cobre com alta confiança estatística (R2 = 0,9973) foi obtida usando um planejamento fatorial composto central. Os resultados evidenciaram que a lixiviação da calcopirita foi fortemente influenciada pelo potencial da solução, que foi função da razão [Fe2+]i:ρpolpa. A razão [Fe2+]i:ρpolpa ≈ 80 permitiu uma faixa ótima de potencial de solução para a maior parte de duração do experimento, o que proporcionou uma extração de cobre de cerca de 91% em 28 dias do concentrado calcopirítico. Nos experimentos de biolixiviação, consórcios de microrganismos capazes de manter potenciais de solução mais baixos propiciaram recuperações de cobre de quase 90% em 129 dias do concentrado calcopirítico. Por sua vez, a lixiviação do minério de baixo teor obteve aproximadamente 63% de extração de cobre em 195 dias. Assim, os resultados experimentais, a teoria da eletroquímica de semicondutores juntamente com os potenciais de Nernst calculados das principais reações de oxidação-redução, indicaram que a recuperação do cobre foi regida por condições experimentais que favoreceram o aumento de concentração de portadores de carga majoritários na superfície da calcopirita. Foram elaborados modelos de (bio)lixiviação pela perspectiva da eletroquímica de semicondutores, que explicaram os resultados obtidos.
The increasing demand for copper, the depletion of the world's resources of high-grade ore deposits and the uninterrupted accumulation of ore residues containing commercially valuable metals tend to drive the development of hydrometallurgical processes. Hydrometallurgy designates more sustainable and low-cost processes for obtaining metallic resources from the (bio)leaching of ores, in which there is the possibility of processing low-grade ores, replacing pyrometallurgy. However, large-scale (bio)leaching of chalcopyrite ore, the most abundant copper ore available in nature (>70%), is still not economically viable. Many of the minerals of interest are semiconductors, such as chalcopyrite, so understanding its semiconducting nature in contact with an electrolyte solution is crucial to promote efficiency and the application of large-scale biohydrometallurgy. However, few works in the field of (bio)leaching have considered the electrochemical approach of semiconductors, in which an effective mineral (bio)leaching depends on what happens at the interface between the semiconductor and an electrolyte solution, as well as in its solid and liquid phases. In order to understand the chemical processes between chalcopyrite and the electrolyte solution, a response surface capable of describing copper extraction with high statistical confidence (R2 = 0.9973) was obtained using a central composite factorial design. The results showed that the leaching of chalcopyrite was strongly influenced by the solution potential, which was a function of the [Fe2+]i pulp ratio. The [Fe2+]i pulp 80 ratio allowed an optimal range of solution potential for most of the duration of the experiment, which provided a copper extraction of about 91% in 28 days from the chalcopyrite concentrate. In the bioleaching experiments, consortia of microorganisms capable of maintaining lower solution potentials provided copper recoveries of almost 90% in 129 days of the chalcopyrite concentrate. In turn, the leaching of low-grade ore obtained approximately 63% of copper extraction in 195 days. Thus, the experimental results, the theory of semiconductor electrochemistry together with the Nernst potentials calculated from the main oxidation-reduction reactions, indicated that copper recovery was governed by experimental conditions that favored an increase in the concentration of majority charge carriers in the chalcopyrite surface. Models of (bio)leaching were elaborated from the perspective of semiconductor electrochemistry, which explained the results obtained.
The increasing demand for copper, the depletion of the world's resources of high-grade ore deposits and the uninterrupted accumulation of ore residues containing commercially valuable metals tend to drive the development of hydrometallurgical processes. Hydrometallurgy designates more sustainable and low-cost processes for obtaining metallic resources from the (bio)leaching of ores, in which there is the possibility of processing low-grade ores, replacing pyrometallurgy. However, large-scale (bio)leaching of chalcopyrite ore, the most abundant copper ore available in nature (>70%), is still not economically viable. Many of the minerals of interest are semiconductors, such as chalcopyrite, so understanding its semiconducting nature in contact with an electrolyte solution is crucial to promote efficiency and the application of large-scale biohydrometallurgy. However, few works in the field of (bio)leaching have considered the electrochemical approach of semiconductors, in which an effective mineral (bio)leaching depends on what happens at the interface between the semiconductor and an electrolyte solution, as well as in its solid and liquid phases. In order to understand the chemical processes between chalcopyrite and the electrolyte solution, a response surface capable of describing copper extraction with high statistical confidence (R2 = 0.9973) was obtained using a central composite factorial design. The results showed that the leaching of chalcopyrite was strongly influenced by the solution potential, which was a function of the [Fe2+]i pulp ratio. The [Fe2+]i pulp 80 ratio allowed an optimal range of solution potential for most of the duration of the experiment, which provided a copper extraction of about 91% in 28 days from the chalcopyrite concentrate. In the bioleaching experiments, consortia of microorganisms capable of maintaining lower solution potentials provided copper recoveries of almost 90% in 129 days of the chalcopyrite concentrate. In turn, the leaching of low-grade ore obtained approximately 63% of copper extraction in 195 days. Thus, the experimental results, the theory of semiconductor electrochemistry together with the Nernst potentials calculated from the main oxidation-reduction reactions, indicated that copper recovery was governed by experimental conditions that favored an increase in the concentration of majority charge carriers in the chalcopyrite surface. Models of (bio)leaching were elaborated from the perspective of semiconductor electrochemistry, which explained the results obtained.
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Palavras-chave
Hidrometalurgia, Lixiviação bacteriana, Calcopirita, Semicondutores, Minérios