By Products Phosphoric Acid Fluosilicic Acid Uranium Rare Earth Elements

Author(s): J. Wing
AICHE Clearwater Conference (American Institute of Chemical Engineers), Clearwater Beach, Florida, USA. Presented June 9, 2012


Phosphoric acid is rich in materials that are potentially attractive for their by-product value. The most common by-product that is being recovered from phosphoric acid is fluosilicic acid. Most phosphate rock contains roughly 4% fluoride, and most of this evolves phosphoric acid evaporators. Many plants scrub evaporator vapors to recover fluosilicic acid (FSA). 

Standard grade FSA is utilized to fluoridate municipal water supply. FSA with very low phosphate content is used to make aluminum fluoride (AlF3) for the aluminum industry. Fluosilicate salts and various premium products can be produced from FSA.

Strong demand for nuclear power is encouraging interest in recovering uranium from phosphoric acid. Process options for extracting uranium oxide (U3O8) from phosphoric acid include traditional solvent extraction and newer ion exchange technology.

Many phosphate ores contain attractive quantities of valuable rare earth elements (REE). FIPR has found substantial concentrations of rare earths in Florida phosphates, and plans are being made to develop recovery technology.

Gypsum is really the product, rather than by-product, from phosphoric acid plants. Many valuable materials can be produced from phosphogypsum. Profits from sale of phosphogypsum products are further enhanced when considering major costs and environmental dangers of maintaining gypsum stacks. The worldwide Stack Free organization encourages utilization of phosphogypsum, rather than stacking it at great cost and environmental hazard.