Phosphogypsum

Phosphogypsum is the calcium sulphate co-produced when phosphate rock is attacked with acid in the wet-process phosphoric acid route. For every tonne of P₂O₅ manufactured, the operation yields roughly 4 to 5 tonnes of this residue^[1]. Phosphate rock carries various impurities that partition between the acid and the calcium sulphate, giving phosphogypsum a polluting character^[1][2].

Within the European Union, all facilities rely on land-based storage, as marine discharge is no longer permitted^[2]. Recovery efforts are hampered by the material's low value and transport costs^[3]. On a commercial scale, Prayon in Belgium sells 80 % of its output into the plasterboard sector; Kemira in Finland supplies the paper industry. In the Netherlands, a pilot-scale demonstration examined several construction products^[3]. The radioactivity of phosphogypsum represents a particular barrier to its utilisation^[2][4].