Cadmium Mining- Process - Uses - Cadmium Mining Companies.

Cadmium Mining

CADMIUM ORE:

Cadmium is a rare earth metal found alongside zinc ores. Even though greenockite (CdS) contains a major percentage of cadmium in nature, it is more commonly associated with zinc sulfide ores like sphalerite. Zinc ores contain only up to 0.3% of cadmium. A small amount of cadmium can be obtained from the byproducts of lead and copper refining. Some metallic cadmium is found along the Vilyuy River basin in Siberia.

MINING:

Cadmium-containing ores are extracted using both surface and underground mining techniques. In surface mining, also known as open-pit mining, cadmium ore is excavated from open pits. These pits are created by drilling into the step walls of the mine, which are strategically designed for extensive excavation.

Once the larger ore bodies are blasted off, they are collected and transported by trucks to the primary processing unit using the ramps within the mines. Open-pit mining is a commonly used method for ores located close to the surface.

In underground mining, extensive machinery and shafts are employed, entailing significant labor and costs. The process of underground mining for cadmium ore commences with comprehensive analysis of the area, including assessments of ore quality and quantity, nearby infrastructure, and overall mining expenses. Only if these assessments meet the necessary criteria is a mine established.

Excavation begins with the digging of underground pits and the creation of shafts to facilitate the movement of labor, machinery, excavated ores, and ventilation. Strict safety measures are implemented to mitigate hazards within the pit. Ores containing cadmium collected from underground mines typically exhibit higher quality compared to those obtained from open-pit mining.

EXTRACTION OF CADMIUM:

The major extraction of cadmium is carried out from mined zinc sulfide ores. There are two extraction steps involved in zinc production. In pyrometallurgical smelting, cadmium is separated through vacuum distillation, while in the electrolytic process, it precipitates among the anode mud.

2 ZnS + 3O₂ ----- >2 ZnO + 2 SO₂

For both processes, the initial step involves roasting the zinc sulfide ore. Roasting the zinc ore at high temperatures and in a concentrated environment converts zinc sulfides into impure zinc oxides.

By electrolysis:

The produced zinc oxide (ZnO) metal undergoes a step-by-step electrolytic leaching process. First, it is leached with a dilute sulphuric acid solution (H₂SO₄). Next, it is leached with a concentrated sulphuric acid (H₂SO₄) solution.

The leaching process is completed when zinc is dissolved, and other impurities such as cadmium, cobalt, nickel, copper, antimony, and thallium are precipitated as a solid mixture. Further processing of this solid residue mixture allows for the extraction of cadmium sulphate.

By pyrometallurgical smelting:

The resultant zinc oxide (ZnO) metal is combusted in the presence of carbon at high temperatures. In this process, the metal reaches its boiling point and begins to vaporize. During this vaporization process, at a certain equilibrium temperature, cadmium alone vaporizes and is collected. The collected cadmium vapor is then further purified using the vacuum distillation method. Cadmium produced from this method contains only 0.3% impurities.

These are the two industrial techniques used to extract and produce cadmium in bulk quantities. About 10% of the consumed cadmium is produced from alternate sources such as dust from recycling iron and steel.

China, the Republic of Korea, and Japan are the major producers of cadmium in the world. Additionally, Canada, India, Kazakhstan, and the United States of America also contribute to the overall global production.