Cadmium Compounds

Abstract

Abstract Naturally occurring cadmium compounds are limited to the rare minerals, greenockite, CdS, and otavite, an oxycarbonate, but neither is an economically important source of cadmium metal or its compounds. Instead, cadmium compounds are usually derived from metallic cadmium produced as a by‐product of lead‐zinc smelting or electrolysis. In general, cadmium compounds exhibit properties similar to the corresponding zinc compounds. The principal areas of cadmium usage in terms of U.S. consumption in 2001 were batteries, 75%; pigments, 12%; coatings and plating, 8%; plastic stabilizers, 4%; and nonferrous alloys and other uses, 1%. Cadmium hydroxide is the anode material of Ag–Cd and Ni–Cd rechargeable storage batteries. Cadmium sulfide, selenide, and especially telluride find utility in solar cells. In flexible PVC, cadmium salts such as stearate are used as heat and light stabilizers. Cadmium cyanide, acetate, fluoroborate, or sulfate is used as an electrolyte in electroplating onto other metals, imparting corrosion protection. The cadmium chalcogenide semiconductors have found numerous applications ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds are used as phosphors in luminescent screens. The declining use of cadmium in plastics and as pigments in the 1980s, largely because of health and environmental concerns and the concomitant introduction of Cd substitutes, has been offset by its increased use in rechargeable storage (Ni–Cd) batteries. Continued and growing concern over the toxicity of cadmium in the environment is expected to lead to alternatives for cadmium compounds in all applications. Inorganic compounds include cadmium arsenides, antimonides, and phosphides; cadmium borates; cadmium carbonate; cadmium complexes; cadmium halides; cadmium hydroxide; cadmium nitrate; cadmium oxide; cadmium phosphates; and others. Many organocadmium compounds are known but few have been of commercial importance. They include dialkyl cadmium compounds, cadmium acetate, and organocadmium soaps.