Promising Options for Solving the Dolomite Problem of the Florida Phosphate Resources—a Brief Review

  • Patrick Zhang
  • Shibo Zheng
  • Wenyi Song
  • Chunhui Feng
  • Brij Moudgil
  • Wending Xiao
  • Dapeng Zhang


Separation of dolomite from phosphate is the most challenging problem in phosphate mineral processing. Over 50% of the future phosphate reserve in Florida contains too much dolomite to process using the current industry practice. The current phosphoric acid production practice requires less than 1% MgO in the phosphate concentrate as the feed material. The Florida Industrial and Phosphate (FIPR) Institute has collaborated with worldwide experts in the field to address this issue. As a result, the industry is now offered three feasible options. Option 1 offers three methods for reducing MgO content in the concentrate from the Crago process, including adding a dolomite depressant in the rougher flotation step, dolomite flotation of the cleaner concentrate, and scrubbing the cleaner concentrate in quartz sand. These methods could reduce MgO content in the final concentrate by 20–40%. Option 2 involves crushing and grinding of high-dolomite phosphate pebbles followed by dolomite flotation at slightly acidic pH using a new collector that does not require phosphoric acid as a phosphate depressant, achieving a final concentrate analyzing less than 0.9% MgO at about 87% P2O5 recovery. Option 3 is a gravity separation technique using an innovative separation jig, and its full potential remains to be demonstrated.


Phosphate Dolomite Flotation Gravity separation 


Funding Information

All the research projects presented in this paper were funded by the Florida Industrial and Phosphate Research Institute, Florida Polytechnic University. All Florida phosphate companies participated in the research projects and provided technical input and in-kind supports.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.



The earliest version of a dolomite collector developed for processing Florida high-dolomite phosphate pebbles and manufactured in China. It is a fatty acid soap with a surfactant.


The second generation of PA-31, a fatty acid soap with a different source of fatty acid.


The third generation of PA-31, a fatty acid soap formulated for dolomite flotation without adding phosphoric acid.


An improved version of PA-66, a fatty acid soap formulated for improved selectivity by using higher quality fatty acid and a new surfactant.


A dolomite collector produced using raw materials from the USA based on the formulation of PA-31.


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Copyright information

© Society for Mining, Metallurgy & Exploration Inc. 2019

Authors and Affiliations

  • Patrick Zhang
    • 1
  • Shibo Zheng
    • 2
  • Wenyi Song
    • 2
  • Chunhui Feng
    • 2
  • Brij Moudgil
    • 3
  • Wending Xiao
    • 4
  • Dapeng Zhang
    • 4
  1. 1.Florida Industrial and Phosphate Research Institute (FIPR)Florida Polytechnic UniversityBartowUSA
  2. 2.China Bluestar Lehigh Engineering CorporationLianyungangChina
  3. 3.Department of Materials Science and EngineeringUniversity of FloridaGainesvilleUSA
  4. 4.Wuhan Institute of TechnologyWuhanChina

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