CINÉTICA E MECANISMO DE OXIDAÇÃO DE UM CONCENTRADO DE ESFALERITA
KINETICS AND MECHANISM OF OXIDATION OF A CONCENTRATE OF SPFALERITE
Vitor de Andrade Alvarenga Oliveira, José Márcio Soares Penna, Lucas Sanches Magalhães
Resumo
A oxidação do concentrado de esfalerita (ZnS) por oxigênio gasoso foi realizada por meio de análise termogravimétrica (TGA). Os produtos de oxidação foram analisados por difratometria de raios X e microscopia eletrônica de varredura (MEV/EDS) e a formação de sulfato de zinco foi detectada durante o processo de oxidação. A pirita presente no concentrado foi aquecida a uma temperatura mais baixa do que a esfalerita e o mecanismo de oxidação estava de acordo com o mecanismo proposto por Dunn J. G. et. al. (1989). A cinética da oxidação da esfalerita foi avaliada por meio do método de isoconversão de Linhas de Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS) e não-linear (MNL) e os resultados sugerem que o processo de oxidação segue um mecanismo complexo. Os valores de energia de ativação encontrados foram superiores a 40kJ/mol na gama completa de conversão sugerindo que a etapa de controle ocorre por meio de reação química.
Palavras-chave
Abstract
The oxidation of sphalerite (ZnS) concentrate by gaseous oxygen was carried out by means of thermogravimetric analysis (TGA). The products of oxidation were analyzed by X-ray difractometry and microscopy electronic scanning (MEV/EDS) and the formation of zinc sulphate was detected during the oxidation process. The pyrite present on concentrate was roasted at lower temperature than sphalerite and the mechanism of oxidation was in agreement with the mechanism proposed by Dunn J. G. et. al. (1989). The kinetics of sphalerite oxidation was evaluated by mean of Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS) and nonlinear (MNL) isoconversional method and the results suggest that the oxidation process follow a complex mechanism. The values of activation energy founded were higher than 40kJ/mol at full range of conversion and suggest that the controlling step takes place via chemical reaction.
Keywords
Referências
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