Hydrometallurgy technology recycling metals such as nickel cadmium nickel cadmium battery
with the rapid development of economy, our country has become a battery in the world the first big country of production and consumption, accounting for about a third of the world's total battery production. According to statistics, in 2000 China's battery annual production of about 12. 5 billion only. Among them, in addition to the zinc manganese dry battery, nickel cadmium cell proportion is the largest. With the development of the telecommunications industry and the popularity of audiovisual products, mainly nickel cadmium battery as a proportion of the secondary battery in the market is growing.
nickel-cadmium batteries contain cadmium, nickel and other metal elements and alkaline electrolyte ( The pH of 12. 9 ~ 13. 5) , will cause harm to human health and ecological environment, has been listed in the hazardous waste in many countries. At the same time, the waste nickel cadmium cell contains a lot of nickel, cadmium, iron, etc. , how to recycle these valuable resources, has very important significance for the sustainable development of the economy.
the recycling waste nickel cadmium battery can be divided into two processing methods of pyrometallurgy and hydrometallurgy.
pyrometallurgy process pyrometallurgy is to make the nickel cadmium battery scrap metals and their compounds in the oxidation and reduction, the process of decomposition, volatile and condensation. Pyrometallurgy including atmospheric vacuum metallurgy and metallurgical two methods. Metallurgical
1, atmospheric pyrometallurgy processing waste nickel cadmium battery is made by high temperature melting, separated from cadmium battery. This process is simple and practical, easy to realize industrialization, and therefore is widely used. Due to the boiling point of cadmium far below the boiling point of iron, cobalt, nickel, can be in after pretreatment of waste nickel cadmium battery reductant ( Hydrogen gas, coke, etc. ) Existing conditions, heating to 900 ~ 1000 ℃, the cadmium metal cadmium into steam, recovery of cadmium by condensation, iron and nickel as iron nickel alloy for recycling. Metallurgical
2, vacuum vacuum distillation method to avoid the wet method and the disadvantages of conventional pyrometallurgy, short process flow, small pollution to the environment. Under the condition of a certain temperature and pressure, vacuum distillation can achieve the goal of recovery of cadmium, cadmium purity can reach 99. 85%, the craft simple, no pollution to the environment.
hydrometallurgy process hydrometallurgy principle is based on the metals and their compounds in waste nickel cadmium battery can dissolve in acid, alkaline solution, or a solvent solution, and then by processing, such as selective leaching, chemical precipitation, electrochemical deposition process, solvent extraction, such as the replacement for one of the valuable metals recovery.
the solvent extraction for metal recovery from waste nickel cadmium battery, using the extraction agent including the TBP ( SanZheng butyl phosphonic acid) 、Lix64（ The hydroxyl oxime) Kelex120 ( Hydroxyquinoline) And so on. Select the appropriate extraction agent is the key of solvent extraction.
control proper pH value, two (DEHPA 2 - Ethyl hexyl) Phosphonic acid) Is a good way to make cadmium and nickel and cobalt separation, while Cyanex272 ( 2, 2,4,4 - Three methyl amyl) Phosphonic acid) Can be effectively separation of cobalt and nickel. After the separation process for use - H2SO4 solution of waste battery, first using DEHPA as extraction agent, the cadmium from the solution, then use Cyanex272 separation of cobalt and nickel. This way has high selectivity and efficiency. Cadmium recovery rate is as high as 99. 99 7%, the recovery rate of cobalt. 5%. Also can use P507 ( 2 - Ethyl hexyl phosphonic acid ( 2 - Ethyl hexyl) Ester) As extraction agent, cadmium, cobalt extracted at the same time, to achieve the purpose of the separation of the nickel.
pyrometallurgy and hydrometallurgy waste nickel cadmium battery
the difference between a wet treatment process is long, sewage discharge may cause secondary pollution of environment. How to deal with the sewage is the key of this technology. Pyrometallurgy is no fears of wastewater, but should pay attention to the processing of waste gas and waste residue, vacuum metallurgy minimum impact to the environment, only equipment investment is large, in the long run should be a better choice. Abroad has been mature processing technology of waste nickel cadmium battery domestic handling of waste nickel cadmium battery recycling technology research stay in the laboratory, so such technology shall also be provided with practical development. About waste nickel cadmium battery recycling technology research should be the country's economic support, should strengthen the propaganda education, promote recycling waste nickel cadmium battery and nickel cadmium battery of cleaner production and production technology updates, as far as possible to reduce or avoid the secondary pollution to the environment.