Nickel, a silvery-white metal, is recognized for its durability, corrosion resistance, and ability to form alloys. These characteristics make it a valuable material in numerous industries, from consumer products to advanced technological applications. Transforming nickel from its raw state into a refined product involves a series of complex processes. This journey includes distinct stages of mining, extraction, and purification, each tailored to the specific type of nickel deposit.
Where Nickel is Found
Nickel is primarily sourced from two distinct types of ore deposits: sulfide and laterite. Sulfide deposits, found in Canada and Russia, typically occur deep within the Earth. They contain nickel minerals mixed with sulfur and other metals, requiring underground mining techniques.
Laterite deposits are common in tropical regions like Indonesia, the Philippines, and New Caledonia. These ores are typically closer to the surface and extracted using open-pit mining. Lateritic ores can contain significant amounts of water, up to 35-40%, which presents challenges during processing.
Extracting Nickel from Ore
Nickel extraction methods depend on the ore type. Sulfide ores are processed using pyrometallurgical techniques, involving high temperatures. Ores undergo crushing and grinding to liberate nickel minerals from waste materials, then flotation separates nickel minerals into a concentrate.
This concentrate is then roasted, smelted, and converted. Roasting removes sulfur, while smelting produces a molten “matte” rich in nickel, copper, and iron. Converting further oxidizes impurities, forming a slag and sulfur dioxide gas.
Laterite ores are processed using hydrometallurgical methods, which involve chemical solutions. High-Pressure Acid Leaching (HPAL) treats ore with sulfuric acid at high temperatures and pressures to dissolve nickel. Atmospheric leaching percolates acid through stacked ore for several months, liberating nickel into a solution. These leaching processes yield a nickel-containing solution for recovery.
Purifying Nickel Metal
After initial extraction, crude nickel undergoes further refining to achieve high purity. Electrolytic refining is a widely used method where impure nickel acts as the anode, and pure nickel is deposited onto a cathode in an electrolytic cell. Impurities from the anode either dissolve into the electrolyte or settle as anode mud. This process allows for the recovery of other valuable metals.
Another important refining technique, especially for producing very high-purity nickel, is the Carbonyl Process, also known as the Mond Process. This method leverages carbon monoxide’s unique ability to react reversibly with nickel, forming a volatile gas called nickel carbonyl. Impure nickel reacts with carbon monoxide at lower temperatures to form nickel tetracarbonyl gas, leaving most impurities as solids. The gaseous nickel carbonyl is then separated and heated, causing it to decompose back into pure nickel metal and carbon monoxide gas, which can be recycled.
What Nickel Becomes
Refined nickel is a versatile metal, used as pure nickel and in various alloys. Its exceptional properties, such as corrosion resistance, high strength, and heat resistance, make it indispensable across many industries. The largest application for nickel is in the production of stainless steel, where it enhances corrosion resistance, ductility, and weldability. About two-thirds of new nickel produced annually is used in stainless steel manufacturing.
Nickel and its alloys are also extensively used in advanced technology sectors. In the aerospace industry, nickel alloys are found in jet engines and gas turbines due to their ability to withstand extreme temperatures and corrosive environments. The growing electric vehicle market relies on nickel for its role in battery technology, particularly in lithium-ion batteries, where it contributes to higher energy density and greater storage capacity. Additionally, nickel is used in coinage, electroplating for protective and decorative coatings, and various electronic components due to its electrical conductivity and magnetic properties.