Book Description

The fate of the cyanide ion in aqueous environments is an area of concern as exampled by an accident on the Danube River in 2000. A mining company accident in Romania spilled thousands of cubic meters of waste slurry that included cyanide and unspecified heavy metals into the Sasar River in Romania, which eventually flowed into the Danube River in Hungary. Thousands of fish died in the incident and agriculture was damaged. The population that depended on the rivers for their livelihood was devastated. There was no investigation into the fate of the spill, and eventually life forms near the origination of the spill began to re-emerge. This thesis investigates hydrolysis and volatilization as possible fates of the cyanide ion in the aqueous environment. Ion selective electrodes were used to analyze the disappearance of cyanide and the appearance of ammonia (the end product of hydrolysis). If these could be measured simultaneously the rate of the hydrolysis of cyanide in a neutral aqueous environment could be determined. The hydrolytic pathway for the cyanide ion has been investigated for the reaction catalyzed with cyanidase, and enzyme found in some bacteria and fungi. The products of the enzyme-catalyzed hydrolysis are formate and carbon dioxide or formate and ammonia, depending on the organism. A two-step reaction has been proposed for cyanide hydrolysis without a catalyst in which formamide is an intermediate. The limiting step in this reaction is the initial hydrolysis of cyanide to formamide and investigations into the appearance of ammonia were used as a surrogate to the formation of this intermediate. Hydrogen cyanide gas is extremely volatile and will escape into the environment at room temperature. The experiments conducted for this thesis showed a consistent loss of cyanide during a timed reaction from an aqueous solution without a corresponding increase in an equivalent amount of ammonia. From additional experiments on the effects of temperature, ultraviolet radiation and aeration, it was concluded that volatilization was the most probable fate of cyanide in these investigations. Confirmation of volatilization was achieved by infrared spectrometry of the vapor phase above aqueous potassium cyanide solutions.