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What is e-waste?
"Electronic waste" is also known as "electronic waste" (English e-waste, waste electronic equipment). Discarded electronic equipment belongs to electronic waste. There are many kinds of electronic waste, which can be roughly divided into two categories: one is the waste electronic products with relatively simple materials and less harm to the environment, such as refrigerators, washing machines, air conditioners and other household appliances, as well as medical and scientific research appliances. The disassembly and treatment of these products are relatively simple; The other is waste electronic products with complex materials and great harm to the environment, such as lead in computers and TV tubes, arsenic, mercury and other harmful substances in computer components, arsenic, cadmium, lead and other persistent and bioaccumulative toxic substances in raw materials of mobile phones.
Current domestic treatment methods
1）Chemical treatment
The chemical treatment of electronic waste is also called wet treatment. The crushed electronic waste particles are put into acidic or alkaline liquid, and the leaching solution is then extracted, precipitated, replaced, ion exchanged, filtered and distilled to obtain high-grade metals. However, in the process of chemical treatment, strong acids and highly toxic fluorides will be used, which will produce a large amount of waste liquid and discharge toxic gases, which will do great harm to the environment.
2）Fire treatment
Pyrotechnic treatment is a method of incinerating, smelting, sintering, melting, etc. of electronic waste to remove metals enriched in plastics and other organic components. Fire treatment will also cause serious harm to the environment. From the aspects of resource recovery and ecological environment protection, these methods are difficult to promote. Guiyu town in Guangdong Province in China has adopted these two treatment methods that are relatively harmful to the environment, which have brought serious impact on the local environment and sustainable development.
3）Mechanical treatment
Mechanical treatment the mechanical treatment of electronic waste is a method of sorting by using the differences in physical properties between components, including disassembly, crushing, sorting and other steps. The materials after sorting and processing can be obtained from recycled raw materials such as metal, plastic, glass and so on through subsequent treatment. The disassembly of electronic waste is usually done manually to recycle the electronic components that have been tested and useful. However, due to the large number of electronic components in electronic waste and the complex combination mode, the manual treatment efficiency is very low.
4）Microbiological treatment
Leaching gold and other precious metals by microorganisms is a new technology for extracting precious metals from low content materials, which began to be studied in the 1980s. The activities of microorganisms make other non precious metals in precious metal alloys such as gold oxidize into soluble substances and enter the solution, exposing precious metals for recycling. Biotechnology extraction of gold and other precious metals has the advantages of simple process, low cost and simple operation, but the leaching time is long.
Treatment of electronic waste by plasma gasification technology
Plasma gasification technology uses plasma torch to heat waste to ultra-high temperature. Under the action of ultra-high temperature and reactive particles, waste molecules are completely decomposed into atomic states, and organic matter is decomposed into simple gas molecules to form syngas (mainly Co, H2), which can be used as fuel or chemical raw materials; Inorganic substances melt to form vitreous slag (mainly composed of silicate and metal), which can be used to recover metals and building materials. Compared with the traditional pyrolysis and gasification treatment method, the high energy density and high temperature of the plasma make the waste reaction speed very fast, which does not depend on the existence of free radicals. It can decompose organics more effectively without producing dioxins. At the same time, there is no fly ash to avoid secondary pollution, and finally realize the complete harmless treatment of toxic and harmful substances, with the waste removal efficiency of more than 99%.
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