Cadmium (Cd)
Overview of Cadmium
Cadmium is a soft, silvery-blue metal that is highly toxic to humans and the environment. Because of its health risks, the use of cadmium has been restricted in many industries. However, its unique chemical and physical properties still make it valuable in specialized applications, from batteries to nuclear technology.
Uses of Cadmium
Despite safety concerns, cadmium has been widely used in industry:
Batteries: Around 80% of cadmium production goes into nickel–cadmium (NiCd) rechargeable batteries, though these are increasingly being replaced by safer alternatives.
Corrosion protection: Cadmium coatings protect steel and other metals from rust, particularly in critical components such as aircraft parts and offshore structures.
Nuclear reactors: Cadmium is an excellent neutron absorber and is used in control rods to regulate nuclear fission.
Pigments: Cadmium compounds once produced vivid yellow, orange, and red pigments used in paints, plastics, and ceramics. Their use has declined due to toxicity.
History of Cadmium
1817 – Discovery: German chemist Friedrich Stromeyer discovered cadmium while investigating the discoloration of zinc carbonate. He identified the impurity as a new element, which he named after cadmia, an old term for zinc ores.
1818 – Independent discoveries: German chemists Karl Meissner and Karl Karsten also independently discovered cadmium shortly after Stromeyer.
Natural Occurrence and Production of Cadmium
Cadmium is a relatively rare element and is not found in pure form in nature. Instead, it occurs as a minor component in zinc ores, particularly in the mineral greenockite (CdS). Nearly all cadmium used commercially is obtained as a by-product of zinc refining.
Biological Role of Cadmium
Cadmium has no known biological role and is considered highly toxic. It accumulates in living organisms, including humans, where it can damage the kidneys, bones, and respiratory system. Cadmium is a suspected carcinogen and can also cause birth defects with prolonged exposure.