General description of treatment and utilization of cyanide-containing wastewater

Cyanide Wastewater produced mainly from gold cyanide gold extraction process. A cyanide plant with a daily processing capacity of 25t gold concentrate should discharge 80-100m ³ of cyanide-containing wastewater every day. The cyanide concentration is 50-500 mg/L. And some even up to 2000mg / L or more. According to the standards of the People's Republic of China, cyanide is a second type of pollutant specified in the comprehensive wastewater discharge standard GB8979-88. The discharge standard of cyanide in the total external discharge port is below 0.5mg/L. And such a high cyanide-containing wastewater is directly discharged into the river, which is bound to cause serious pollution of water quality and cause serious after-effects.

Therefore, the treatment of cyanide in the wastewater to protect the environment is an important task in the gold mining process using cyanidation. At present, there are many methods for treating cyanide-containing wastewater at home and abroad.

In the treatment of cyanide-containing wastewater in gold mines in China, the chlorination method (chlorine agent, chlorine gas, liquid chlorine, bleaching powder, calcium hypochlorite and sodium hypochlorite) and acidification method have been used in the past. In recent years, SO ₂ -air method and activated carbon have been developed. Adsorption catalytic oxidation method, pipeline aeration method, natural purification method, acidification method - chlorination method - natural purification method combined process. Electrochemical methods, internal electrochemical methods, and ion exchange methods are in the experimental stage. In recent years, the closed-circuit recycling process of cyanide wastewater has brought good economic, ecological and social benefits, and has been widely concerned.

It should be pointed out that the treatment of cyanide-containing wastewater should be adapted to local conditions, and it is not possible to hold a method. For example, the gold smelting method of the gold plant was originally designed by the alkaline liquid chlorination method. As another example, the cost of hydrogen peroxide treatment is expensive in people's minds. However, a gold mine in Hubei has a dense population and developed fishery waters. They use the hydrogen peroxide method (adding stabilizers), which is cheaper than the bleaching powder method and can meet the national discharge standards for fishery water quality. However, alkaline liquid chlorination is still the most widely used method.

For the chlorination process for treating cyanide, the chlorinating agents used are chlorine gas, liquid chlorine, bleaching powder, calcium hypochlorite and sodium hypochlorite. In fact, they all produce hypochlorous acid (HOCL) in the solution and then undergo oxidation. Among them, liquid chlorine is the most widely used, and it is generally carried out in an alkaline solution, and is therefore called an alkaline chlorination method. In recent years, it has developed into an acidic chlorination method.