There are four main methods for electronic product waste: chemical treatment, pyrolysis, mechanical treatment, and microbial treatment.
1. Mechanical treatment.
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. After subsequent treatment, the sorted materials can obtain recycled raw materials such as metals, plastics, and glass. This treatment method has the advantages of low cost, simple operation, not easy to cause secondary pollution, and easy to achieve scale.
The disassembly of electronic waste is usually done manually to recover useful electronic components after detection. However, due to the large number of electronic components in electronic waste and the complex combination method, the efficiency of manual treatment is very low.
2. Chemical treatment.
The chemical treatment of electronic waste, also known as wet treatment, puts the broken electronic waste particles into acidic or alkaline liquid, and the leaching liquid finally obtains high-grade metals through a series of processes such as extraction, precipitation, replacement, ion exchange, filtration and distillation. However, in the chemical treatment process, the use of strong acid and highly toxic fluoride will produce a large amount of waste liquid and emit toxic gases, which is very harmful to the environment.
3. Pyrolysis.
Pyrometallurgy is a method of incinerating, melting, sintering, and melting electronic waste to remove organic components such as plastics and enrich metals. Pyrometallurgy can also cause serious harm to the environment. From the perspective of resource recovery and ecological environmental protection, these methods are difficult to promote. These two treatment methods, which are very harmful to the environment, have a serious impact on the local environment and sustainable development.
4. Microbial treatment.
Using the activities of microorganisms, other non-precious metals in precious metal alloys such as gold are oxidized into soluble substances and enter the solution, exposing the precious metals. The extraction of precious metals such as gold by biotechnology has the advantages of simple process, low cost and simple operation, but the soaking time is long. Ferrothiobacillus ferrooxidans was used to carry out leaching tests on crushed pre-treated electronic waste fragments. At the selected temperature, pH and addition amount, more than 90% of Cu, Zn and Ni can be leached, and Pb is stabilized in the precipitate in the form of PbSO4.
