REMOVAL OF IRON, CHROMIUM AND SODIUM IMPURITIES FROM ZINC TUNGSTATE (ZNWO4)

Removal of Fe, Cr and Na impurities from ZnWO4 was carried out by the chemical purification of the starting materials for crystal growth. Tu ngsten trioxide (WO3) and zinc oxide (ZnO) were prepared by novel meth ods based on homogenous precipitation (using hydrogen peroxide as a co mplexing agent for sodium tungstate) and liquid-liquid extraction tech niques, respectively. The impurity concentrations were determined by g raphite furnace atomic absorption spectrometry (GFAAS) and flame atomi c emission spectrometry (FAES). The quality improvement of the crystal s grown from purified starting materials was demonstrated by ultraviol et-visible (UV-VIS) spectrophotometry.