1, physical law
Physical method is to use mechanical means and PCB physical properties of the different ways to achieve recovery.
The purpose of fragmentation is to make the metal in the waste circuit board as far as possible and organic matter, in order to improve the separation efficiency. The study found that when the broken in 0.6 mm, the metal can basically reach 100% of the dissociation, but the broken way and the choice of series depends on the subsequent process.
Separation is the use of material density, particle size, conductivity, magnetic conductivity and surface characteristics of the physical properties of the separation of the separation. Are widely used at present the wind shaking, flotation separation technology, cyclone separation technology, the ups and downs of separation and vortex separation technology.
2, super critical technology treatment
Supercritical fluid extraction technology is a method to extract and separate the effects of pressure and temperature on the solubility of supercritical fluid without changing the chemical composition. Compared with the traditional extraction method, the supercritical CO2 extraction process has the advantages of friendly environment, convenient separation, low toxicity, little or no residue, and can be operated at room temperature and so on.
The main research direction of the treatment of waste PCB by using supercritical fluid is focused on two aspects: first, the supercritical CO2 fluid has the ability to extract the resin and the flame retardant composition in the printed circuit board. When the printed circuit board of the resin bonded material is ultra supercritical CO2 fluid after the removal, printed circuit board copper foil layer and a glass fiber layer can be easily separated, thus for the efficient recovery of the printed circuit board materials. Two, the direct use of supercritical fluid extraction of waste PCB in the metal. Wai reports to fluoride diethyl dithio carbamate lithium (lifddc) as complexing agent, from the simulated samples cellulose filter paper or sand extraction of Cd2 +, Cu2 +, Zn2 +, Pb2 + and Pd2 +, As3 +, Au3 +, GA3 +, Sb3 + results, the extraction efficiency of over 90%.
Supercritical processing technology also has a lot of defects such as extraction of high selectivity for adding entrainer, the environmental harm; extraction pressure is relatively high requirements for the equipment is high; extraction process to be used in high temperature so that the energy consumption is large, etc..
3, chemical method
Chemical treatment technology is used to extract the chemical stability of PCB in a variety of different process.
3.1 heat treatment method
Heat treatment method is mainly by means of high temperature to make the separation of organic matter and metal. It mainly includes incineration method, vacuum pyrolysis method, microwave method etc..
3.1.1 incineration method
Incineration method is the electronic waste crushing to a certain particle size, into an incinerator burning, will be the decomposition of organic component, the separation of gas and solid. The residue after burning is a bare metal or its oxide and glass fiber, which can be recovered by physical and chemical methods after being crushed. The gas containing organic ingredients into two combustion treatment after discharge. The disadvantage of this method is that it produces a lot of waste gas and toxic substances.
3.1.2 lysis method
Cracking in the industry also called retorting, is the electronic waste disposed in the container is heated under the condition of air isolation, control temperature and pressure, the organic matter is broken down into oil and gas. After condensing and collecting recyclable. Different from the electronic waste incineration, vacuum pyrolysis process is carried out under anaerobic conditions, it can suppress the two? The production of English and Chinese, the amount of waste gas generated is little, and the environment pollution is small.
3.1.3 microwave processing technology
Microwave recycling method is the first electronic waste broken, and then use the microwave heating, so that the organic matter decomposition. Heated to about 1400 DEG C so that the glass fiber and www.pcblover.com metal melting glass forming substances, this substance cooling Jin, gold, silver and other metal on the beads in the form of separation out, recycling use the remaining glass material can be recovered and used as building materials. The method has significant difference with the traditional heating method, and has the advantages of high efficiency, high efficiency, high utilization rate of resource recovery and low energy consumption.
3.2 wet metallurgy
Hydrometallurgical technology is mainly by metal can be dissolved in nitric acid, sulfuric acid and aqua regia and other acid characteristics. The metal from electronic waste removal and from the liquid phase to be recycled. It is a widely used method to deal with electronic waste at present. Compared with the method of fire metallurgy, the method of the wet metallurgy has the advantages of less waste gas emission, easy processing of the residue after extraction, remarkable economic benefit, simple process flow and so on.
4, biological technology
Biotechnology is the use of microorganisms in the mineral surface adsorption and oxidation of microorganisms to solve the problem of metal recycling. Microbial adsorption can be divided into two types, which are immobilized metal ion and immobilized metal ion by using microbial metabolites. The former is fixed using bacteria to produce hydrogen sulfide, when bacteria adsorbed on the surface of the ions reach saturation state, can form floc settling down; the latter is using ferric ion in the oxidation of other metal oxide gold and other precious metals into soluble substances in solution, the precious metal is exposed to facilitate recovery. It has the advantages of simple process, low cost and convenient operation to extract gold and other precious metals. However, the extraction time is longer, the extraction rate is lower, and the current is not really put into use.
Electronic waste is a valuable resource, and it is of great significance to strengthen the research and application of metal recovery technology of electronic waste. Because of the complex and diverse characteristics of electronic waste, either technique alone is difficult to recover the metal, future disposal of e-waste technology development trend should be: processing industry, resource recovery maximization, science and technology of processing. To sum up, the study of waste PCB resources, both to protect the environment, prevent pollution, but also conducive to recycling of resources, saving a lot of energy, and promote the sustainable development of economic society.