Recycling of waste pickle acid by precipitation of metal fluoride hydrates
2007 (English)In: Minerals Engineering, ISSN 0892-6875, Vol. 20, no 9, 950-955 p.Article in journal (Refereed) Published
Stainless steel is pickled in mixed acid solutions (1-3 M HNO3 and 0.5-4 M HF). The spent solution is usually neutralized with lime, and in Sweden about 18,000 tons/yr of metal hydroxide sludge is disposed as landfill waste. We are developing a cost-saving and environmentally friendly process, involving crystallization of beta-FeF3 . 3H(2)O, where the metal content is recovered and the acid is recycled. Iron has been successfully separated from spent pickle bath solutions by precipitation of beta-FeF3 . 3H(2)O in a continuous crystallizer (10 L scale) where the solution is concentrated by nanofiltration. The crystal growth rate of beta-FeF3 . 3H(2)O has been determined in industrial pickle bath solutions at 50 degrees C and the results have been compared to previous measurements in pure HF/HNO3 solutions prepared in the laboratory. The growth rate of beta-beta eF(3) . 3H(2)O crystals at 50 degrees C is in the order of 10(-11) m/s in both industrial and pure acid mixtures.
Place, publisher, year, edition, pages
2007. Vol. 20, no 9, 950-955 p.
hydrometallurgy, waste processing, recycling, CRYSTAL-STRUCTURE, TRIHYDRATE, MIXTURES, BETA-FEF3.3H2O, MOSSBAUER, GROWTH
IdentifiersURN: urn:nbn:se:kth:diva-14095DOI: 10.1016/j.mineng.2007.03.011ISI: 000249051000015ScopusID: 2-s2.0-34447256127OAI: oai:DiVA.org:kth-14095DiVA: diva2:329673
Conference: International Symposium on Material, Minerals and Metal Ecology (MMM 06). Cape Town, SOUTH AFRICA. NOV 14-15, 2006 2010-07-132010-07-132011-09-13Bibliographically approved