structural features
cyanide has the smell of almond oil. it is a volatile substance and easily soluble in water. its CN-ion is similar in structure to CO and N2, I .e. (:C = N :)-. an external charge seems to be distributed on a c atom (as shown in fig. 1), I .e. (-CN), which is an isoelectronic body. Structurally, this ion is a dipole ion, that is, there is a dipole and a negative charge. The negative end of the dipole should be on the side of the C atom. Therefore, a pair of lone electron pairs on the carbon atom is easy to coordinate to metal ions with empty orbits, which is a strong coordination complexing agent. All transition metals can form cyanide complexes.
poisoning and clinical manifestations
Among all cyanides, hydrogen cyanide is the most toxic, followed by cyanide that can release hydrogen cyanide gas (HCN) or cyanide ion (CN-) in the air or tissue. CN-has super complex ability to metal ions, and cytochrome oxidase is the most sensitive to it. After cyanide enters the human body through different pathways, the released CN-quickly binds to the trivalent iron of the end oxidase of the mitochondrial electron transport chain, namely cytochrome C oxidase, thereby inhibiting the activity of cytochrome C oxidase and blocking the respiratory chain Make the tissue hypoxia. Because aerobic metabolism is inhibited, anaerobic respiration becomes dominant, which can produce a large number of acidic substances such as lactic acid, which eventually leads to metabolic acidosis and causes a series of neurological symptoms. Oral administration of a large amount of cyanide, or inhalation of high-concentration hydrogen cyanide gas in a short period of time, can suddenly coma within a few seconds, causing "flash-like" poisoning. Generally, acute poisoning can be divided into prodromal period, dyspnea period, spasm period and 4 periods of paralysis period, mainly causing non-specific reactions such as dizziness, headache, nausea, vomiting, chest tightness and tinnitus, in severe cases, it can lead to purple lips, dyspnea, convulsions, coma and even respiratory failure and death. Long-term low-dose cyanide exposure can also cause neurological damage symptoms such as Parkinson's-like syndrome, confusion and mental decline.
processing method
1. Alkaline chlorination method The principle of alkaline chlorination method is to add high-valent chlorine oxidant to alkaline cyanide-containing wastewater. Cyanide is first oxidized to cyanate, and further oxidized to carbon dioxide and nitrogen. Commonly used oxidants are: ClO2, Cl2 (two kinds of gas and liquid), bleaching powder, sodium hypochlorite, hypochlorous acid boundary, chlorite, etc. The pH of the oxidation reaction is controlled at about 11, and the operation is simple. After adding chlorine oxidant, only stirring is required. If the composition of the wastewater is complex and the consumption of chlorine oxidants is high, it is generally 4-9 times the theoretical value, the purity of the reagent is not high or the consumption of chlorine oxidants is greater when the content of thiocyanate is high; when it contains ferrocyanide complexes, It will oxidize into ferrocyanide complexes and become soluble groups, and the treated wastewater is difficult to meet the national discharge standards.
2. Chemical precipitation method The principle of chemical precipitation method is to convert cyanide into ferrocyanide complex and form ferrocyanate precipitation with heavy metal ions in wastewater, and other heavy metal ions are sulfide and hydroxide The form is removed. The ferrous sulfate method is to convert cyanide into ferrocyanide, then into a Prussian blue insoluble compound, and then decanted or filtered out
structural features
cyanide has the smell of almond oil. it is a volatile substance and easily soluble in water. its CN-ion is similar in structure to CO and N2, I .e. (:C = N :)-. an external charge seems to be distributed on a c atom (as shown in fig. 1), I .e. (-CN), which is an isoelectronic body. Structurally, this ion is a dipole ion, that is, there is a dipole and a negative charge. The negative end of the dipole should be on the side of the C atom. Therefore, a pair of lone electron pairs on the carbon atom is easy to coordinate to metal ions with empty orbits, which is a strong coordination complexing agent. All transition metals can form cyanide complexes.