Application of Temperature Programmed Oxidation-Infrared Technique in the Analysis of Sulfur Occurrence and Genesis in Phosphate Rock

Abstract

In this study, a temperature programmed oxidation-infrared (TPO-IR) technique was improved and applied in the analysis of sulfur occurrence and genesis in phosphate rock. Phosphate rocks from three regions (KYP, ZJP, and WAP) were selected for the detection of sulfur species by TPO-IR combined with XRD, SEM, EDS, and XPS characterization. TPO-IR results show that the total sulfur contents of the three phosphate rocks were 2.14% for KYP, 1.18% for ZJP, and 1.06% for WAP. In the low-temperature area (<1000°C), TPO-IR detected that both KYP and WAP contain FeS with a characteristic temperature of about 513°C and their contents were 9.22‰ and 0.64‰, respectively. In high-temperature areas (>1000°C), the TPO-IR curves suggest that sulfate is the main sulfur species in the three phosphate rocks. Typically, the characteristic temperature near 1070^oC belongs to MgSO₄, and the characteristic temperature near 1290°C belongs to CaSO₄. Due to the incomplete TPO-IR database of sulfur reference materials at present, it is not possible to assign all sulfur species in high-temperature areas. However, in a sense, this research provides theoretical basis and experimental support for the application of the TPO-IR technique for the detection of sulfur species in other solid minerals.