Recovery of tungsten from acidic solutions rich in calcium and iron

During the decomposition of low-grade scheelite ore using HCl-H3PO4 solution, a large amount of Ca and Fe in the ore are released into the leach liquor, which complicates subsequent purification. Due to the difficulties of separation, a novel solvent extraction process was developed for extracting tungsten from acidic solutions rich in calcium and iron. The impacts of calcium and iron impurities on the extraction were investigated, and the results showed that co-extraction of calcium led to the loss of tungsten. Therefore, pre-decalcification was carried out by adding H2SO4 to the acidic leach liquor before extraction, and a high-quality gypsum product with a low tungsten content (< 0.1 wt%) was obtained. Subsequently, tri-butyl phosphate was used to extract tungsten from the calcium-removed solution. During solvent extraction, 96.2% tungsten and 26.5% iron were extracted by a single-stage extraction under the optimal conditions. Then, tungsten and iron were separated by stripping with NaOH. Tungsten was transferred into the aqueous phase as soluble sodium tungstate, whereas iron was precipitated as ferric hydroxide. A complete process flow chart was proposed for the treatment of acidic solutions rich in calcium and iron. The efficient extraction of tungsten and the resource utilization of impurities show the excellent prospects of this process for industrial applications.

Automated summary

A novel solvent extraction process was developed to extract tungsten from acidic solutions rich in calcium and iron, achieving efficient extraction and separation through pre-decalcification and stripping processes. The efficient extraction of tungsten and the utilization of impurities demonstrate excellent prospects for industrial applications.