Environmental impact and management of phosphogypsum

The production of phosphoric acid from natural phosphate rock by the wet process gives rise to an industrial by-product called phosphogypsum (PG). About 5 tons of PG are generated per ton of phosphoric acid production, and worldwide PG generation is estimated to be around 100–280 Mt per year. This by-product is mostly disposed of without any treatment, usually by dumping in large stockpiles. These are generally located in coastal areas close to phosphoric acid plants, where they occupy large land areas and cause serious environmental damage. PG is mainly composed of gypsum but also contains a high level of impurities such as phosphates, fluorides and sulphates, naturally occurring radionuclides, heavy metals, and other trace elements. All of this adds up to a negative environmental impact and many restrictions on PG applications. Up to 15% of world PG production is used to make building materials, as a soil amendment and as a set controller in the manufacture of Portland cement; uses that have been banned in most countries. The USEPAThe authors are grateful to AECI (project N A/5537/06) and to the Spanish National R&D&I Plan (Project CTQ2008-02012/PPQ) for the financial support of this study. Hanan Tayibi is grateful to the CSIC (Spanish National Research Council) for an I3P contract (I3PDR-6-01).Peer reviewe