Process for the preparation of tantalum/niobium hydroxides and oxides with a low fluoride content

US5194232A · kind A · utility

Assignee

• Hermann C. Starck Berlin GmbH & Co. KG · DE

Inventors

• Walter Bludssus · Vienenburg, DE
• Erk-Rudiger Feuerhahn · Osterode, DE
• Horst Zimmermann · Mannheim, DE

Key dates

• Filing date: Aug 27, 1991
• Grant date: Mar 16, 1993
• Expiry date: Aug 27, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/80
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Fluorine content of tantalum and niobium hydroxides is reduced to under 0.5 weight % by washing such hydroxide precipitates (as obtained by HF digestion and solvent extraction) with dilute ammonia (1 to 10%) and then water in two washing stages. The first washing stage includes a partial neutralization and the used wash water of the second stage is advantageously recycled, after adjustment of its ammonia concentration, for use as the first stage washing liquid.