Raman Spectroscopy Study of Phosphorites Combined with PCA-HCA and OPLS-DA Models

Xiyu Yao,Huan Liang,Huayi Hou,Xiangbai Chen,Kai Chen

doi:10.3390/min9100578

Abstract

Phosphorite is a nonrenewable strategic resource, a convenient and rapid method of phosphorite grade identification and classification is important to improve phosphate utilization. In this study, Raman spectroscopy has been combined with principal component analysis and hierarchical clustering analysis (PCA-HCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) models for an investigation of different grade phosphorite samples. Both the PCA-HCA and OPLS-DA models showed that different grade phosphorite samples can be clearly distinguished by statistically analyzing the Raman spectra after smoothing, baseline correction, and first derivation. In addition, the S-line study on the OPLS-DA model clearly demonstrated that the symmetrical stretching vibrational mode of phosphate near 960 cm−1 had a much more significant contribution than other vibrational modes for the differentiation of different grade phosphorite samples.

Highlights

Phosphorite is a nonmetallic mineral, which is an important raw material for many kinds of phosphorus products [1,2,3,4,5]
The classification of phosphorite grade is an important issue in the study of various types of phosphorites
The common methods for determining phosphorite grade include conventional chemical analyses, infrared spectroscopy, nuclear magnetic resonance, X-ray spectroscopy, and plasma mass spectrometry, etc. [5,6,7,8,9,10], most of these methods require complex sample preparation and are difficult to perform on site for underground measurements

Summary

Introduction

Phosphorite is a nonmetallic mineral, which is an important raw material for many kinds of phosphorus products [1,2,3,4,5]. The main types of phosphorite are magmatic apatite, sedimentary metamorphic apatite, and sedimentary rock-type apatite. These phosphorites constitute essentially the apatite group with a wide range of accessory minerals of quartz, calcite, dolomite, and silicates, etc. The classification of phosphorite grade is an important issue in the study of various types of phosphorites. The common methods for determining phosphorite grade include conventional chemical analyses, infrared spectroscopy, nuclear magnetic resonance, X-ray spectroscopy, and plasma mass spectrometry, etc. It is of great interest to study a powerful method to meet these difficulties

Methods

Results

Conclusion