With the industrialization and scale of PCB processing, and the extensive research and application of electronic information products, 1oz vs 2oz more and more electronic waste is generated and manufactured in the practice activities of socialist production and life in human development.

Waste polychlorinated biphenyls contain heavy metals such as lead, mercury, hexvalent chromium, and toxic chemicals such as polybrominated biphenyls and polybrominated biphenyls as flame retardants, which not only pollute the environment, soil and water resources, but also cause harm to human health. Waste PCBS contain nearly 20 non-ferrous and rare metals and have high economic value in recycling.

Therefore, the correct disposal of waste PCB board is particularly important.

Today we discuss some ways to deal with e-waste:

1 Physical Method

According to the different physical properties of the PCB, physical and mechanical means are used for recycling.

1.1 Crushing

Mechanical crushing of PCB, so that it has metal and organic matter disintegration and separation, improve the efficiency of urban sorting work. how to test a circuit board with a multimeter When the crushed particles reach 0.6mm, the metal material can basically reach 100% dissociation, but the choice of crushing treatment method and stage depends on the subsequent production process of the enterprise.

1.2 Sorting

According to its density, particle size, conductivity, permeability and surface characteristics and other physical characteristics, the crushed material can be separated by wind vibration table technology, flotation separation technology, cyclone separation technology, float and sink separation technology and eddy current separation technology.

2 Supercritical technology treatment

This method does not change the chemical composition of the PCB. Supercritical fluids are dissolved by pressure and temperature, and then extracted, separated, and purified. Compared with traditional extraction methods, supercritical CO2 extraction is more environmentally friendly, easy to separate, less toxic, with little or no residue, and is operated at room temperature.

Supercritical processing is not without its drawbacks. For example, the entrainment agent used in the extraction process is harmful to the environment, and the high pressure and high temperature extraction method has high requirements on equipment and energy consumption.

3 Chemical Method

Chemical treatment technology lies in the process of extraction using the different stability of various chemical components in the PCB.

3.1 Heat treatment method

Heat treatment can separate organic and metallic materials by high temperatures. The heat treatment method also includes a vacuum cracking method, incineration method, microwave method and so on.

3.1.1 Incineration method

E-waste is physically broken down into tiny particles and then sent to an incinerator, where the organic components are broken down. Waste incineration residues consist of exposed metals, metal oxides and glass fibers, which are crushed and recovered by physical and chemical methods. The disadvantage of this method is that it will produce a lot of waste gas and toxic substances.

3.1.2 Cracking method

Pyrolysis, also known as dry distillation.

Under the condition of isolating air, the waste PCB is heated, the pressure and temperature are controlled, and the organic matter is decomposed into oil and gas, which is collected and recycled after condensation. Unlike incineration, vacuum pyrolysis is carried out in the absence of oxygen, which can inhibit the production of furans and dioxins and reduce environmental pollution.

3.1.3 Microwave processing technology

The use of microwave heating electronic waste, when heated to about 1400 ° C, the heated glass fiber and metal will glass, after cooling gold, silver and other metals will be automatically separated in the form of beads. Recycled glass can be used as a building material. Compared with the traditional method, it has the advantages of high efficiency, high speed, high resource recovery and low energy consumption.

3.2 Hydrometallurgy

Hydrometallurgical enterprise technology, the PCB is placed in nitric acid, sulfuric acid and aqua regia and other acids, so that the metal is removed from the electronic industry waste, and then recycled. It is a widely used method for the treatment of electronic product waste in China. Hydrometallurgy has more advantages than pyrometallurgy, such as less waste gas emission, easy analysis and treatment of residues after metal extraction, remarkable economic and social benefits, simple process design and flow management.

4 Biotechnology

The surface of mineral is adsorbed by microorganisms, and microbial oxidation and metal oxidation recovery are carried out. There are two main approaches:

1, microbial adsorption can be divided into the use of microbial metabolites to fix metal ions

When hydrogen sulfide produced by bacteria is fixed, flocs can be formed and settled down when the surface of bacteria is saturated with ions.

2. Direct fixation of metal ions by microorganisms

The oxidation of trivalent iron ions is used to oxidize gold and other precious metals as some other metals in the alloy into soluble substances soluble in organic solutions in order to improve the exposure of precious metals for recovery.

Biotechnology extraction process is simple, low cost, easy to operate, but the extraction time is long, the extraction rate is low, has not been put into use.

peroration

Electronic waste has complex and diverse characteristics, and a single recycling technology is difficult to completely recover. The treatment technology of e-waste needs to be continuously optimized, to maximize the recycling of resources, and to make the treatment technology scientific and industrialized. In short, the disposal and recycling of waste circuit boards can not only protect the environment and prevent pollution, but also facilitate the recycling of resources and promote the sustainable development of society and economy.