Abstract
Checking the presence of sesquioxide (Fe2O3, Al2O3) is helpful for its removal in advance. Therefore, the occurrence of sesquioxide in a mid-low grade calcareous-siliceous collophane ore (massive carbonate-apatite, also known as francolite) from Guizhou, China was determined by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), field emission scanning electron microscope-energy dispersive X-ray spectrometry (FESEM-EDX) and Mineral Liberation Analyzer (MLA). The results show that iron mainly occurs as pyrite FeS2, goethite FeO(OH) and as substitution within dolomite Ca(Mg,Fe)(CO3)2, while aluminum is enriched in muscovite KAl2(AlSi3O10)(OH)2 and also found in apatite (F,CO3)CaPO4 and calcite CaCO3 due to isomorphism or adsorption. All these minerals are fine-grained, among which pyrite and goethite tend to be enriched in larger particles. Intergrowth is predominant in the six minerals’ locking. Pyrite is mainly intergrown with calcite, biotite and also included in apatite and muscovite, while the monomer pyrite appears as semi-automorphic fine grain with the liberation of 56.1%. Apatite particles are mainly intergrown with quartz and calcite. Most of goethite, dolomite, muscovite and calcite form intergrowth with apatite, with contents of 21.7%, 11.1%, 19.5% and 41%, respectively. The removal of pyrite, goethite, dolomite, muscovite and calcite in the ore is the key to reduce the contents of Fe2O3 and Al2O3. In the subsequent beneficiation, the ore must be fully ground. In addition to flotation, magnetic separation can also be considered to remove part of iron in ore. For the removal of aluminum from apatite, leaching method can be considered.
Highlights
Phosphate ore is an essential raw material for manufacturing phosphoric industrial products, which is nonrenewable, nonrecyclable and irreplaceable
Phosphate ore can be divided into three major types: igneous deposits, sedimentary deposits and biological deposits
The chemical and mineralogical composition of the collophane ore are shown in Tables 2 and 3, Figure 2 gives the X-ray diffraction (XRD) phase analysis result of the collophane ore and Figure 3 shows the dissemination characteristics of some main mineral particles
Summary
Phosphate ore is an essential raw material for manufacturing phosphoric industrial products, which is nonrenewable, nonrecyclable and irreplaceable. The world’s phosphate reserves in 2019 are 70 billion tons. Morocco has the largest phosphate reserves, which are 50 billion tons accounting for 71.43% of the total. Morocco, the United States and Russia are the leading phosphate. Minerals 2020, 10, 1038 producing countries with a proportion of 79% [1]. Phosphate ore can be divided into three major types: igneous deposits, sedimentary deposits and biological deposits (guano accumulations). About 75% of phosphate resources are sedimentary [2]
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