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Quantification of Hematite and Goethite Concentrations in Kaolin Using Diffuse Reflectance Spectroscopy: A New Approach To Kubelka-Munk Theory

Published online by Cambridge University Press:  01 January 2024

Ítalo Gomes Gonçalves ,
Carlos Otávio Petter  and
Jaqueline Lepkoski Machado
Ítalo Gomes Gonçalves*
Affiliation:
Laboratório de Processamento Mineral, Departamento de Engenharia de Minas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
Carlos Otávio Petter
Affiliation:
Laboratório de Processamento Mineral, Departamento de Engenharia de Minas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
Jaqueline Lepkoski Machado
Affiliation:
Laboratório de Processamento Mineral, Departamento de Engenharia de Minas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
*
*E-mail address of corresponding author: [email protected]
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Abstract

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Kaolin ores are usually contaminated by some Fe-bearing minerals, the strong colors of which degrade the quality of the final product. A spectroscopic technique is sought to quantify the content of hematite and goethite, the main contaminant minerals in the kaolin from Capim River in Brazil, was the focus of this study. The total Fe content obtained through X-ray fluorescence showed a poor correlation with the brightness of kaolin, due to the inability to differentiate between the Fe contained in the (oxyhydr)oxides and the Fe present in the crystalline structure of kaolinite, especially when the Fe-bearing minerals occur in small quantities. Here, a new generic technique to quantify Fe (oxyhydr)oxides in kaolin, based on the Kubelka-Munk theory, is presented. A new interpretation of the theory was made that enables its use without the need to measure thin layers of material. The results with synthetic goethite and hematite were very positive (R2pred ≈ 0.99) and experiments with contaminants from the mine are already underway.

Keywords

BrightnessDiffuse ReflectanceGoethiteHematiteKaolinKubelka-Munk Theory
Type
Article
Information
Clays and Clay Minerals , Volume 60 , Issue 5 , October 2012 , pp. 473 - 483
Copyright
Copyright © Clay Minerals Society 2012

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