Recovery of tungsten and vanadium from waste tungsten metal products
Tungsten, due to its unique physical and chemical properties, is widely used in the field of high temperature resistance and high strength. However, the content of tungsten in the earth's crust is very low, and the resources are also continuously depleted. Therefore, more and more countries, especially developed countries and resource deficient countries, attach importance to the recovery of tungsten from waste tungsten metal products, and there are many research reports on this aspect. All kinds of tungsten containing materials, such as tungsten carbide, tungsten carbide scrap, tungsten carbide cutting tools, etc. One of the important characteristics of waste tungsten containing materials is that the tungsten content is very high. Scheelite Concentrate and wolframite concentrate usually contain only 7% to 60% of tungsten, while the waste tungsten bearing materials contain 40% ~ 95% w, some even more than 99%. At present, about 1 / 3 of tungsten in the world comes from the recovery of waste tungsten containing metal materials. Waste tungsten metal products often contain other valuable metal components, such as Mo, V, Co, Ni, Cu, Ta, Nb, Ti, re, Ag, etc., which are worthy of comprehensive recovery. Sometimes, the value of Co and Ta as by-products exceeds the value of tungsten. It is reported that there are feasible methods for recovering tungsten, such as cobalt, nickel, nickel, titanium, etc. However, there are few reports on the technology of recovering tungsten from tungsten containing materials.
Vanadium and tungsten have very similar solution chemical properties and industrial recovery process. The recovery process usually dissolves the raw material into sodium salt, and then converts it into ammonium tungstate and ammonium vanadate solution by precipitation or solvent extraction, and then crystallizes in the chemical form of ammonium salt. Therefore, it is difficult to separate tungsten and vanadium from chemical solution. In the past 20 years, more work has been focused on improving the purity of apt (ammonium paratungstate) products and reducing production costs. In addition to the raw material composition and crystallization control, the purity of the product depends more on the purification of crude sodium tungstate solution. The selection of purification process and technology is related to the raw material composition and product requirements. The existing purification technologies often only consider the recovery of tungsten, and most of them will cause a large loss of vanadium. Therefore, it is necessary to select a method which can remove a lot of impurities and not affect the recovery of vanadium.
The purpose of this paper is to study a new process for recovering tungsten and vanadium from waste tungsten metal products. Because the concentration of WO3 in the alkali leaching solution of waste tungsten containing materials exceeds 90g/L, the chemical precipitation crystallization method is adopted to recover tungsten; the concentration of vanadium in the leaching solution is about 0.18g/l, and vanadium can be recovered as a by-product.
