Phosphorus gypsum

Phosphorus heap at Fort Meade , Florida.

Phosphorus heap near Kėdainiai , Lithuania.

As phosphogypsum (also phosphogypsum ) is referred to in the phosphate industry obtained as by-product in large quantities gypsum . Due to impurities in the raw materials, this gypsum contains radioactive and toxic components, such as traces of uranium or radium . Only about 2% of the phosphogypsum can be re-used because it cannot compete economically with other types of gypsum due to the effort involved in cleaning; the rest is mostly stored outdoors and represents a potential environmental and water pollution or hazard.

Phosphorus gypsum is produced by the reaction of fluoroapatite (Ca ₅ (PO ₄ ) ₃ F) with sulfuric acid (H ₂ SO ₄ ) during the production of phosphoric acid (H ₃ PO ₄ ) according to the reaction:

${\displaystyle \mathrm {Ca_{5}(PO_{4})_{3}F\ +\ 5\ H_{2}SO_{4}\ +\ 10\ H_{2}O\ \longrightarrow \ 3\ H_{3}PO_{4}\ +\ 5\ CaSO_{4}\cdot 2\ H_{2}O\downarrow \ +\ HF\uparrow } }$

The gaseous hydrogen fluoride (HF) produced during the reaction escapes and is collected separately for further use. The uranium compounds present in the phosphate ore are dissolved in the phosphoric acid after the reaction and can be obtained therefrom as uranium (V, VI) oxide (U ₃ O ₈ ). Traces of radium can be separated from the phosphogypsum produced using special cleaning processes.

Individual evidence

1. ↑ Construction chemistry: Introduction to chemistry for civil engineers and architects, by Roland Benedix . books.google.de. Retrieved December 12, 2009.
2. ^ Franz Wirsching: Gips - natural raw material and residual material of technical processes, Chemistry in our time, 19th year 1985, No. 4, p. 141, ISSN  0009-2851 .