Tungsten production technology from low-grade tungsten-containing materials

Abstract

Tungsten is a worldwide highly-consumed metal. As the tungsten price has increased substantially in the last decade there is an economic imperative to recycle it. It is suggested to involve tungsten-containing metallurgical slags and wastes in reprocessing. Extraction of 87 % of tungsten into solution was reached by autoclave pressure leaching with sodium carbonate (250 g/l) as a leaching agent. Temperature of the process is 220-230°C, solid-to-liquid ratio - 1:5, stirring rate - 60 rpm, duration - 6 hours. After liquor purification from sulfur and silicon by flocculating agent VPK-402, ion-exchange extraction of tungstate-ion was carried out. Sorption properties of two anion-exchange resins - Amberjet 4200 and AV-17-8 - were studied in static conditions. It was revealed that strongly basic anion-exchange resin AV-17-8 in chloride-form is more capable of tungsten in comparison with Amberjet 4200: 42,5 kilos of W/m{3} against 32 kilos of W/m{3}. Carbonate-ions showed a greater affinity to the resin than tungstate-ions, therefore ion-exchange stage was performed in two steps: 1 - to remove CO[3]{2}- from liquor, 2 - extract WO[4]{2}-. Desorption was implemented by NH[4]Cl (50 g/l) with solid-to-liquid ratio 2,5:1 yielding ammonium paratungstate (NH[4])[2]WO[4] (APT). Technology steps for production pure tungsten powder from APT through WO[3] are well-known and described briefly.