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333277 
Journal Article 
Recovery of sulphur and calcium carbonate from waste gypsum 
Nengovhela, NR; Strydom, CA; Maree, JP; Oosthuizen, S; Theron, DJ 
2007 
1 
Water SA
ISSN: 1816-7950 
33 
5 
741-747 
Gypsum is produced as a waste product by various industries, e.g. the fertiliser industry, the mining industry and power stations. Gypsum waste disposal sites are responsible for the leaching of saline water into surface and underground water. The aim of this investigation was to evaluate a process for converting waste gypsum into sulphur and calcium carbonate. The process evaluated consisted of the following stages: reduction of gypsum to calcium sulphide; H[sup]2[/sup]S-stripping and sulphur production. Thermal reduction showed that gypsum could be reduced to CaS with activated carbon in a tube furnace operating at 1 100 °C. The CaS yield was 96%. The CaS formed was suspended in water to form a CaS slurry. The reaction of gaseous CO[sup]2[/sup] with the CaS slurry leads to the stripping off of H[sup]2[/sup]S gas and the precipitation of CaCO[sup]3[/sup]. During batch studies sulphide was stripped from 44 000 mg/Å‚ to less than 60 mg/Å‚ (as S). The H[sup]2[/sup]S generated in the previous step was then reacted in the PIPco process to form elemental sulphur. (English) 
Précipitation; Plomb; Carbone dioxyde; Sulfure; Eau saumâtre; Lessivage; Site décharge déchet; Industrie extractive; Gypse; Déchet; Calcium carbonate; Carbonate calcium; Soufre; Récupération; Sulfate; Carbonate; precipitation; lead; Carbon dioxide; sulfides; brackish water; leaching; waste disposal sites; Mining industry; gypsum; Wastes; sulfur; recovery; sulfates; carbonates; Precipitación; Plomo; Carbono dióxido; Sulfuro; Agua salobre; Lavado con lejía; Industria extractiva; Yeso; Desperdicio; Calcio carbonato; Carbonato calcio; Azufre; Recuperación; Sulfato; Carbonato