A Method to Recover Tungsten and Nickel from Waste Nickel-Tungsten Catalysts

Nickel-tungsten catalysts are widely used in hydrotreating and hydrocracking. The main components are about 25% tungsten trioxide, 2% nickel oxide, 50% alumina, 5% silica, and a small amount of iron, vanadium and other substances. Waste nickel-tungsten catalysts contain metals such as tungsten and nickel. If they are recycled, they will generate huge economic benefits and avoid environmental pollution caused by the waste of nickel-tungsten catalysts.

A method of recovering tungsten nickel from a waste nickel-tungsten catalyst includes the following process steps:

1) Reduction and calcination: Calcine the waste nickel-tungsten catalyst with a reducing agent at a temperature of 600 to 800 ° C for a reaction time of 1 to 4 hours, thereby converting nickel oxide and iron oxide in the waste nickel-tungsten catalyst into Metals of nickel and iron, while alumina, tungsten oxide and silica are not reduced;

2) Displacement and leaching: a copper solution is added to the calcined product, and nickel metal and iron are replaced with copper ions to form nickel ions and iron ions into the solution, wherein the copper ion concentration is 0.5 to 3 mol/ L, the pH of the adjustment solution is 1.0 to 2.0, the reaction temperature is 60 to 80 ° C, and the leaching time is 2 to 6 hours;

3) Extraction and separation: the solution after displacement leaching is filtered, the filtrate is a solution containing nickel ions and a small amount of iron ions and copper ions, the pH of the solution is adjusted to 3.0 to 4.5, and then extracted to remove nickel from copper Separated from iron;

4) Concentration and crystallization: In the above step, the raffinate obtained after the extraction is a pure nickel solution, which can be directly concentrated and crystallized to obtain nickel crystals, and the stripping solution is a solution containing copper ions and iron ions, and can be returned to step 2, For obtaining nickel ions and iron ions;

5) High-temperature calcination: the residue leached in step 2 is mixed with sodium carbonate, calcined at 500-800 ° C for 2-6 hours, and the ratio of the molar ratio of sodium carbonate to tungsten is 1.2-2.0:1. The material after washing is washed with hot water of 60-99 ° C, the solid-liquid mass ratio is 1:4-12, and the washing time is 1-3 hours, and a solution containing sodium tungstate is obtained, and the filter residue is used for recovering aluminum and copper;

6) Recovery of tungsten: The solution containing sodium tungstate obtained in the step 5 is adjusted to pH value of 0.5 to 2.0 with an acid, and reacted at a temperature of 75 to 99 ° C for 2 to 4 hours, and the filter residue obtained after filtration is 80 to 99. The hot water washing at °C has a solid-liquid mass ratio of 1:8 to 12, and the washed residue is dried at 80 to 120 ° C for 2 to 8 hours to obtain a tungstic acid having a purity of 98.5% or more.

The above process has high recovery rate, simple process and low cost: it can be comprehensively recycled not only for tungsten, nickel but also for aluminum and copper.

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