ABSTRACT
Cyanide can be associated with solids in contaminated water and soil systems. Therefore, methods for analyzing total cyanide or specific cyanide species in soils, sludges, plant and animal tissue, solid wastes, and other solids are of interest. As discussed in Chapters 2 and 5, free cyanide is very reactive and readily forms solution complexes and solid phase precipitates with metals in the environment. It can form solid precipitates with a number of metals, including copper, zinc, nickel, and iron among others [1]. Iron-iron cyanide solids such as Prussian Blue, Fe4(Fe(CN)6)3(s), and Turnbull’s Blue, Fe3(Fe(CN)6)2(s), are the most common cyanide solid phases in the environment, as iron is very reactive with free cyanide, and is ubiquitous [2]. Iron-iron cyanide solids have limited to moderate solubility in water, with the solubility dependent on pH, and oxidation-reduction potential [2,3]. Solid phases consisting of simple salts of free cyanide or metal-cyanide complexes, such as KCN, NaCN, and K2Ni(CN)4, are not encountered in the environment to any appreciable extent, as these solids dissolve readily in water. Aqueous cyanide species can also adsorb onto various inorganic and organic phases, with the extent of adsorption being dependent on pH, and other solution conditions [4-9]. Thus, adsorption is another means by which cyanide species can become associated with the solid phase.
