Electrolytic and zinc smelting methods for tungsten carbide recycling

Recycling tungsten carbide is crucial due to its extensive use in cutting and machining tools and its significant environmental and economic impact. Two primary methods for recycling tungsten carbide are the Electrolytic Method and the Zinc Smelting Method. Each has unique processes and applications, making them suitable for different types of waste tungsten carbide materials.

1. Electrolytic Method

The electrolytic method is an efficient process that leverages the electrode potentials of different components within tungsten-containing waste. This method is particularly effective for waste materials that include tungsten carbide and cobalt metal.

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Process Overview:

• In an acidic solution, such as one with a hydrochloric acid concentration of about 20g/L, cobalt can be selectively dissolved, or both cobalt and tungsten carbide can be simultaneously dissolved.
• A graphite anode and a nickel plate cathode are used, where the cobalt dissolves into the solution, forming CoCl2.
• Electrolysis is performed at a low voltage of 1.0-1.5V, leading to the dissolution of cobalt and the peeling off of WC from the waste.
• The anode mud produced is then processed (washed, ball milled, and sieved) to recover WC, which can be reused to produce new tungsten carbides.

Advantages:

• Low reagent and energy consumption.
• Simplicity of the process.

Limitations:

• Only applicable to waste tungsten carbide with a cobalt content above 10%.

2. Zinc Smelting Method

This method involves the use of metallic zinc and high temperatures to recover tungsten carbide from waste materials. It is effective for waste tungsten carbide with low cobalt content or those containing other metals like tantalum and titanium.

Process Overview:

• Waste tungsten carbide blocks and metallic zinc are placed in a crucible inside a vacuum furnace.
• The mixture is heated to temperatures between 773 to 873 K, where cobalt reacts with molten zinc to form a zinc-cobalt alloy.
• At 1173 K, zinc is removed by vacuum distillation, leaving behind loose WC and cobalt powder.
• The recovered WC and cobalt powder are then processed (ball milled and sieved) for use in new production of tungsten carbides.

Advantages:

• Short production process.
• Capable of handling low-cobalt content waste.
• Recovers materials that closely match the grade of the original waste.

Limitations:

• Requires specific types of waste material.
• Complex equipment and high energy consumption.
• Generally, higher costs than the electrolytic method.

Conclusion

Choosing the right recycling method depends on the composition and properties of the waste tungsten carbide. The Electrolytic Method is best suited for high-cobalt content waste and is noted for its efficiency and low operational costs. In contrast, the Zinc Smelting Method is ideal for low-cobalt content waste and can handle a broader range of materials, despite its higher operational complexities and costs. Both methods offer effective solutions for recycling tungsten carbide, contributing to sustainable practices in the industry.