Physical Separation of Wastes Nonferrous Metals
Introduction
Nonferrous metals are used widely in modern society, from vehicles to household appliances. With the continuous development of industry, used nonferrous metals accumulate continuously and become one of the main sources of environmental-hazardous waste. Therefore, physical separation of wastes from nonferrous metals is important for the collection, transportation, and utilization of these materials, which also can reduce environmental pollution. It’s important for relevant departments to accelerate the development of safety and effective physical separation technologies for nonferrous metals.
Background
In recent years, by carrying out the Blue sky and Bitter sky campaign against air pollution, the Chinese government has put a priority on energy conservation and emissions reduction in various industries. Nonferrous metals are widely used in many industries, and they increasing appear in our lives. The development of these industries has promoted the demand for nonferrous metals. With the increase in the production and consumption of nonferrous metals, more and more nonferrous metal scrap is also produced. Because of this, it has become very important to develop efficient and effective ways of separating nonferrous metals from the wastes.
Method of Physical Separation
The process of physical separation for nonferrous metals involves a series of steps. Firstly, the wastes need to be pre-treated by crushing, sorting and removing large particles before physical separation. Secondly, the wastes need to be processed through magnetic separation, gravity separation or flotation-separation methods in order to separate the reusable nonferrous metals from other refuse. Thirdly, the separated materials need to be treated further in order to be reused in industry.
Magnetic Separation
Magnetic separation is the process of using a magnetic field to separate ferromagnetic materials from nonmagnetic materials. This method is widely used in the recycling of nonferrous metals and has great significance in resource regeneration. In the process of magnetic separation, the material is fed onto a conveyor belt and passed through a high-intensity magnetic field at the end of the belt. The magnetic field will attract the ferromagnetic particles of the material and separate them from the nonmagnetic particles. However, this method has some limitations, such as being unable to separate some non-magnetic particles, such as aluminum and nonferrous alloys.
Gravity Separation
The principle of gravity separation is based on differential specific gravity and particle size of materials. In other words, different materials or particles with different specific gravities have different settling velocities in a liquid or gas medium according to their relative densities. In this process, the materials are fed into a sluice box or vibrating table. The vibrating table uses the effect of vibration to separate the lighter and heavier particles and has found application in the separation of metal particles from water and organic solvents. This process is straightforward and easy to operate.
Flotation-Separation
Flotation separation is based on the hydrophobic surface characteristics of materials and density differences within a pulp or liquid phase to separate nonferrous metals. In this method, the material is suspended in a liquid-air mixture and a compressed air jet is introduced into the mixture. This causes the relatively lighter particles to bubble and float to the surface, while the heavier particles remain suspended in the liquid. This method is more complicated but is more efficient and commonly used for the separation of metals from fine materials.
Conclusion
To sum up, physical separation of wastes from nonferrous metals plays an important role in the management of hazardous materials and the prevention of environmental pollution. Magnetic separation, gravity separation and flotation-separation are three commonly used methods for the physical separation of wastes nonferrous metals and various materials. These technologies have a high degree of accuracy and can help reduce the hazardous waste impact on the environment. In order to ensure the efficient and safe management of nonferrous metals, government departments should strengthen their research on these physical separation technologies and robustly promote these technologies in the society.
