Cadmium carbonate CdCO

CdO slowly absorbs carbon dioxide forming cadmium carbonate, CdCOs. 

Cadmium carbonate, CdCO 1.8X10 Iron(II) hydroxide, Pe(OH)2 4.1X10 ... 

Cadmium carbonate CdCO, 1.0 10- Copper(I) thiocyanate CuSCN 1.77- 10- ... 

Among the various sources of cadmium contamination are the plating operations and the disposal of cadmium-containing wastes. In these cases, the forms of cadmium also depend on the treatment of the waste prior to disposal. The most common forms include Cd ", cadmium-cyanide complexes, or Cd(OH)2 solid sludge. Hydroxide (Cd(OH)2) and carbonate (CdCOs) solids dominate at high pH, whereas Cd " and aqueous sulfate species are the dominant cadmium forms at pH <8. Under reducing conditions, when sulfide is present, the stable solid CdS(s> is formed. Cadmium also precipitates in the presence of phosphate, arsenate, chromate, and other anions, although solubility will vary with pH and other chemical factors [77]. The free Cd " appears to be the form readily taken up by plants, whereas CdCU is taken up more slowly, while Cd-humate is not adsorbed. 

Cadmium was discovered by F. Stromeyer in 1817. In nature, it is mostly found in zinc deposits. The mineral, greenocktite (CdS) is found associated with the zinc ore, sphalerite (ZnS). Similarly zinc carbonate contains otavite (CdCOs) in small amounts. Its abundance in the earth s crust is estimated to he 0.15 mg/kg and in sea water 0.11 irg/L. 

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