Recovery and Preparation of Potassium Fluorotantalate from High-Tantalum-Bearing Waste Slag by Pressure Alkaline Decomposition

Tantalum slag is a type of high-grade tantalum resource with great recovery value. In this paper, low fluorine process, including alkali pressure decomposition, low-acid transformation, solvent extraction, and crystallization, proposed to recover prepare potassium fluotantalate. First, some underwent the optimal decomposition conditions were obtained under reaction time 2 h, oxygen partial 2.5 MPa, liquid–solid ratio 4:1, basicity 40 wt.%, temperature 200 °C. Under these conditions, efficiencies Ta Nb 93.62% 95.42%, respectively. X-Ray diffraction (XRD) scanning electron microscope (SEM) used detect main phase residue showed that it was mainly sodium tantalate. With increase in pressure, particle size gradually decreases becomes loose. Second, subjected leaching obtain tantalate niobate, niobium more than 99%. Last, solution extraction evaporative crystallization The results rate separation factors above 94% 200, respectively, purity fluotantalate met requirements commercial products. Compared current industrial practice, consumption hydrofluoric acid greatly reduced, increased.