Multivariate regression models for the simultaneous quantitative analysis of calcium and magnesium carbonates and magnesium oxide through drifts data

Luciano Marder,Paulo Tomedi,Marco F Ferrão,Celso U Davanzo,André Jablonski

doi:10.1590/s0103-50532006000300025

Abstract

In the present work multivariate regression models were developed for the quantitative analysis of ternary systems using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) to determine the concentration in weight of calcium carbonate, magnesium carbonate and magnesium oxide. Nineteen spectra of standard samples previously defined in ternary diagram by mixture design were prepared and mid-infrared diffuse reflectance spectra were recorded. The partial least squares (PLS) regression method was applied to the model. The spectra set was preprocessed by either mean-centered and variance-scaled (model 2) or mean-centered only (model 1). The results based on the prediction performance of the external validation set expressed by RMSEP (root mean square error of prediction) demonstrated that it is possible to develop good models to simultaneously determine calcium carbonate, magnesium carbonate and magnesium oxide content in powdered samples that can be used in the study of the thermal decomposition of dolomite rocks.

Highlights

The reserves of carbonate rocks in the state of Rio Grande do Sul - Brazil, are mainly constituted by dolomitelike rocks (MgO content ≅ 18%), while calcite-like rocks (MgO content < 4%) occur in a smaller proportion
The present paper proposes the use of the DRIFTSPLS method to determine the concentration in weight of calcium carbonate, magnesium carbonate and magnesium oxide
The major advantages are that these analyses do not require extensive sample preparation,[32] are noninvasive, and do not produce residues that are harmful to the environment

Summary

Introduction

The reserves of carbonate rocks in the state of Rio Grande do Sul - Brazil, are mainly constituted by dolomitelike rocks (MgO content ≅ 18%), while calcite-like rocks (MgO content < 4%) occur in a smaller proportion. Multivariate Regression Models for the Simultaneous Quantitative Analysis carbonates (52% and 40% approximately),[1] at a given temperature and a complete calcination process that results in a mix of calcium carbonate combined with magnesium oxide in the same material. The lack of specific methodologies[2,3,4,5,6] that allow the joint analysis of the mix of obtained products from the fractionated calcination of the dolomite-like rocks led to the development of a technique that enabled the quantitative analysis of calcium carbonate and magnesium oxide by means of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS).

Results

Conclusion