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fbtwitterlinkedinvimeoflicker grey 14rssslideshare1
Publisher: Consejo Superior de Investigaciones Científicas
Journal: Revista de Metalurgia
Languages: English
Types: Article
Subjects: Stainless steel, Pickling, Selective precipitation, Iron, Chromium, Nickel, Acero inoxidable, Decapado, Precipitación selectiva, Hierro, Cromo, Níquel, Mining engineering. Metallurgy, TN1-997, Technology, T, DOAJ:Mining and Metallurgy, DOAJ:Technology and Engineering
Stainless steel spent pickling baths are very complex solutions of metals and acids (HNO<sub>3</sub> and HF) and are a very important environmental concern. Several processes have been developed for acid recovery (free and bounded acid) with techniques like acid retardation, solvent extraction, evaporation and dialysis diffusion. In these processes, metallic content is precipitated and treated for its disposal. We have developed a process that permits the separation of metals by means of a selective precipitation, induced by adding free fluoride. Iron (Fe) and chromium (Cr) precipitate as pentafluorides and nitrogennickel (Ni) remains in solution. After this stage, complex fluorides can be hydrolized with alkali to give iron and chromium hydroxides, releasing fluoride in solution<br><br>Los baños ácidos agotados del decapado de acero inoxidable son disoluciones muy complejas debido al alto contenido de metales y ácidos (HNO<sub>3</sub> y HF), por lo que constituyen un grave problema medioambiental. Existen tratamientos comerciales para la recuperación del ácido (libre o complejado) que se basan en técnicas de retardo ácido, extracción con disolventes, evaporación o membranas. En estos procesos el contenido metálico es precipitado y tratado como un residuo. El grupo de investigación formado por los autores del presente trabajo ha desarrollado un procedimiento que permite el aprovechamiento de dichos metales mediante su recuperación selectiva con una técnica de precipitación modificada inducida por fluoruro libre. Se consigue la precipitación de hierro (Fe) y cromo (Cr) como pentafluoruros (pH 3-4,5) dejando el níquel en disolución. Posteriormente, los fluoruros complejos son hidrolizados con álcali dando lugar a hidróxidos de hierro y cromo, mientras que el fluoruro es redisuelto.

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