**Abstract**

The first commercial production of phosphate rock began in England in 1847. A wide variety of techniques and equipment is used to mine and process phosphate rocks in order to beneficiate low-grade ores and remove impurities. The eighth chapter of this book deals with mining and beneficiation of phosphate ore. The principle and operating conditions of important parts of manufacturing process including separation, classifi‐ cation, removing of carbonates, calcination and flotation was described. The chapter ends with description of techniques used for extraction of rare earth element.

**Keywords:** Apatite, Phosphate Rock, Mining, Benefication, Separation, Calcination, Flotation, Extraction of Rare-Earth Element

Phosphate rock is an important mineral commodity used in the chemical industry and production of food. Phosphate ores show a wide diversity in the composition of their gangue materials but generally fall into one of the following categories based on major associated gangue materials [1],[2],[3],[4]:


phosphates are very similar. The separation by physical means becomes even impossible when the carbonate minerals are finely disseminated into the phosphate particles.

An alternative technique for the beneficiation of these ores is the calcination. Calcination is the process of heating the ore to a high temperature ranging from 800 to 1000°C to decompose CaCO3 and MgCO3 to CaO, MgO and gaseous CO2. The CaO and MgO formed are then removed as hydroxides by quenching the calcined product in water and wash‐ ing. The most common chemical reagent used to enhance the removal of calcium and magnesium hydroxides is ammonium chloride.

Chemical dissolution of carbonate minerals (calcite and dolomite) from calcareous phosphate ores, without the calcination, using organic acids also proved to be capable of beneficiating the calcareous phosphate ores on the laboratory scale.

**4. Phosphate ores associated with organic matter** (**black or brown phosphates**): ores of this type are generally beneficiated by heating the ore up to about 800°C. This type of calcina‐ tion burns organic material and residual organic carbon without significantly affecting the superior qualities of sedimentary phosphates such as the solubility and reactivity.

Furthermore, as a result of low calcination temperature, the reduction of calcium sulfate, present in ore, to corrosive calcium sulfide by the organic matter is minimized. During the burning of organic matter, the following two conditions must be kept: organic carbon must be decreased to less than 0.3% to minimize the gassing in the wet phosphoric acid process‐ ing, and apatite CO2 must be maintained at a level close to 2% to allow good reactivity of calcined product.

**5. Phosphate ores containing more than one type of gangue minerals**: many sedimentary phosphate deposits contain mixtures of undesired constituents. These ores require a series of beneficiating operations during their processing depending on the type of gangue minerals present in each ore. This may include, after the size reduction, the combination of attrition scrubbing, desliming, flotation, gravity separation and/or calcination. Each flow sheet is to be designed after thorough characterization and testing of a representative sample of the exploited ore.

**Igneous and metamorphic phosphate ores**: the main gangue materials in these ores are sulfides, magnetite, carbonates (calcite, dolomite, siderite and ankerite), nepheline syenite, pyroxenite, foskorite, etc. The processing of these ores may include, after crushing and grinding, washing, desliming, magnetic separation and flotation depending on the types of present gangue minerals. However, the flotation is a common step in all of them [1].

The quality factors of commercial phosphate rocks include [5]:


content of Fe and Al (expressed as R2O3 1 ), the content of Mg in phosphate and accessory minerals, the content of inert gangue mineral (insoluble oxides and silicates), the content of Na and K (phosphate and accessory minerals), organic matter (native and beneficiation reagents), chlorides (from evaporite salts), heavy metals (Cd, Pb, Zn, Hg), potentially toxic elements (Se, As, Cr, V) and radionu‐ clides (U, Th, Ra, Rn).

Increasing world demand on fertilizer in the 1960s and 1970s and the need for phosphate feedstock stimulated the efforts to develop the techniques to beneficiate low-grade ores and remove impurities. It is highly desirable, for both economic and technical reasons, to remove as much of these impurities as possible, thus to increase the apatite content and the grade of phosphate feedstock and to improve the chemical quality. Phosphate ores can be beneficiat‐ ed by many methods, and usually a combination of more methods is used [6],[7], [8].

The phosphate rock concentrate must meet the following conditions to be salable [4]:

**a.** High P2O5 content (>30%);

phosphates are very similar. The separation by physical means becomes even impossible

An alternative technique for the beneficiation of these ores is the calcination. Calcination is the process of heating the ore to a high temperature ranging from 800 to 1000°C to decompose CaCO3 and MgCO3 to CaO, MgO and gaseous CO2. The CaO and MgO formed are then removed as hydroxides by quenching the calcined product in water and wash‐ ing. The most common chemical reagent used to enhance the removal of calcium and

Chemical dissolution of carbonate minerals (calcite and dolomite) from calcareous phosphate ores, without the calcination, using organic acids also proved to be capable of

**4. Phosphate ores associated with organic matter** (**black or brown phosphates**): ores of this type are generally beneficiated by heating the ore up to about 800°C. This type of calcina‐ tion burns organic material and residual organic carbon without significantly affecting the

superior qualities of sedimentary phosphates such as the solubility and reactivity.

**5. Phosphate ores containing more than one type of gangue minerals**: many sedimentary phosphate deposits contain mixtures of undesired constituents. These ores require a series of beneficiating operations during their processing depending on the type of gangue minerals present in each ore. This may include, after the size reduction, the combination of attrition scrubbing, desliming, flotation, gravity separation and/or calcination. Each flow sheet is to be designed after thorough characterization and testing of a representative sample

**Igneous and metamorphic phosphate ores**: the main gangue materials in these ores are sulfides, magnetite, carbonates (calcite, dolomite, siderite and ankerite), nepheline syenite, pyroxenite, foskorite, etc. The processing of these ores may include, after crushing and grinding, washing, desliming, magnetic separation and flotation depending on the types of present gangue minerals. However, the flotation is a common step in all of them [1].

**i. Physical factors**, which include the parameters such as the texture (hardness,

**ii. Chemical factors**, which include the parameters such as the content of phosphorus

porosity, cementing of coating phases), the particle size (coarse or cryptocrystalline), the degree of crystallinity of apatite and the effect of physical treatments (natural or

(BLP grade, **Section 9.3**), fluorine, carbonate and free carbonates in apatite. The

Furthermore, as a result of low calcination temperature, the reduction of calcium sulfate, present in ore, to corrosive calcium sulfide by the organic matter is minimized. During the burning of organic matter, the following two conditions must be kept: organic carbon must be decreased to less than 0.3% to minimize the gassing in the wet phosphoric acid process‐ ing, and apatite CO2 must be maintained at a level close to 2% to allow good reactivity of

when the carbonate minerals are finely disseminated into the phosphate particles.

magnesium hydroxides is ammonium chloride.

384 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

The quality factors of commercial phosphate rocks include [5]:

calcined product.

of the exploited ore.

calcined state).

beneficiating the calcareous phosphate ores on the laboratory scale.


As will be mentioned in **Section 9.3**, the content of P2O5 is usually expressed as bone phos‐ phate of lime. The treatment and utilization of phosphate ore is shown in **Fig. 1**.

**Fig. 1.** The treatment of phosphate rock and end-product [8].

<sup>1</sup> Sesquioxides (R2O3) that consist of three atoms of oxygen and two atoms or radicals of other elements, e.g. Al2O3, Fe2O3 and La2O3.

**Fig. 2.** Mining and beneficiation of sedimentary (a) and igneous (b) phosphate ore [8].

The example of a generic scheme for mining and beneficiation of sedimentary and igneous phosphate ore is shown in **Fig. 2** [8].
