Abstract
Tantalum and niobium extraction from domestic tantalite concentrates was studied by the United States Department of Interior, Bureau of Mines, using HF, H2SO4, and HF/H2SO4, mixtures. Sulfuric acid additions to HF greatly enhanced the dissolution rate of tantalite. Optimum leaching conditions were a combination of sulfuric and hydrofluoric acid mixtures and temperature. Increasing sulfuric acid concentration and temperature had a synergistic effect on the tantalum and niobium extraction. Maximum tantalum extraction was 95 pct at 60° C when using a mixture of 30 pct HF and 35 pct H2SO4. Concentrated sulfuric acid was also effective in dissolving tantalite concentrates. Greater than 90 pct sulfation was obtained at 300° C and 2 hr. The concentration of tantalum and niobium solubility in concentrated sulfuric acid decreased with increasing reaction time because of precipitation caused by hydrolysis.
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