Quantitative Phase Analysis of Phosphate Rocks with XRD for Fertilizer Production

Fertilizers are typically made of phosphates and nitrates. Usually, the phosphorous comes from phosphate rock. There are numerous minerals which affect the content and availability of phosphorous in phosphate rocks. One standard method employed for distinguishing between the various mineral phases in the raw material is X-ray diffraction (XRD). This technique can be used to quantify the content of different minerals based on their crystallographic structure.

Instrument

The Thermo Scientific™ ARL™ EQUINOX 100 makes use of a custom-designed Co (15 W) or Cu (50 W) micro-focus tube with mirror optics. The unit consumes minimum power, which allows it to be fully portable without the need for an external water chiller. The same unit can be transported between laboratories without any need for special infrastructure.

Compared to other diffractometers, the ARL EQUINOX 100 offers rapid data collection times due to its unique curved position sensitive detector (CPS) that measures all diffraction peaks simultaneously and in real time and is thus suitable for both reflection and transmission measurements (Figure 1).

ARL EQUINOX 100 X-ray diffractometer.

Figure 1. ARL EQUINOX 100 X-ray diffractometer.

Experiment

Measurement of a ball milled Phosphate Rock sample (3 minutes, 20 Hz) was carried out in reflection mode. The samples were analyzed under Cu Kα (1.541874 Å) radiation for 10 minutes with the sample rotating during the analysis. MATCH! in combination with COD database was employed for qualitative phase analysis, while MAUD was used for quantification.

Results

A Rietveld refinement gave the phase composition of the sample. It contains 79% of Fluoroapatite, 17% of Quartz, and 4% of Calcite (Figure 2) which corresponds to a fairly high phosphorous content (P2O5 ~ 26%).

Rietveld fit of a phosphate rock sample.

Figure 2. Rietveld fit of a phosphate rock sample.

Conclusion

The ARL EQUINOX 100 is an appropriate instrument to assess the quality of phosphate rocks using Rietveld’s method both in production plants and in the field due to its ease and robustness. MATCH! and MAUD cover all quantification requirements of phosphate-related minerals.

Thermo Fisher Scientific

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers.

For more information on this source, please visit Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers.

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