Preparation of High-purity Sodium Tungstate from Low-grade Tungsten-concentrate with a High Content of Calcium and Other Impurities

摘要

A new technological process for production of sodium tungstate from low-grade tungsten-concentrate with a high content of calcium and other impurities has been studied. The experiments showed that average tungsten leaching efficiency of more than 96.92% can be obtained with a low NaOH consumption by using the mechanical activating caustic decomposition, and the content of main impurities (P, As, Si) in Na_2WO_4 solution obtained is competitive with that from standard wolframite concentrate by traditional caustic decomposition. After recovering caustic liquor by first crystallization, molybdenum is removed from Na_2WO_4 solution by ion exchange method. High-purity sodium tungstate is obtained by second crystallization of Na_2WO_4 solution. This technology has the advantages of good adaptability for raw materials, nigh removing efficiency of impurities, high tungsten recovery and high economic benifit.