Stamenov L.Stefanova V.Petkov K.Iliev P.2024-07-162024-07-162024-07-162024-07-162017-01-011314-79781314-7471SCOPUS_ID:85014076117https://rlib.uctm.edu/handle/123456789/1162In present study the crystallization process of ferric sulfate hydrate - Fe2(SO4)3.xH2O from rich in Fe(III) sulfate waste solutions was investigated. These solutions were obtained after autoclave oxidation of pyrite concentrate. They are characterized with high concentrations (> 60 g l-1) of ferric ions and sulfuric acid. Based on the ternary diagram of the Fe2(SO4)3-H2SO4-H2O system and the laboratory tests the necessary compositions and conditions for preparation of saturated solutions for ferric sulfate crystallization process were determined. It was found that the crystallization process takes place with obtaining of bulky sludge containing following phases: FeH(SO4)2.4H2O (rhomboclase), Fe2(SO4)3.8H2O (ferric sulfate with eight molecules water) and Fe4.67(SO4)6(OH)2.20H2O (ferric sulfate hydroxide hydrate). After detention of the sludge for seven days at temperature 373 K two modifications of ferric sulfate hydrate were observed: ferric sulfate hydroxidehydrate(Fe4.67(SO4)6(OH)2.8H2O) and paracoquimbite (Fe2(SO4)3.9H2O).enArticle