how to recycle pcb boards
Several methods of circuit board recycling
1 Physical Law
The physical method is the use of mechanical means and the difference in PCB physical properties to achieve recycling.
1.1 Broken
The purpose of crushing is to dissociate the metal in the waste circuit board from the organic matter as much as possible to improve the separation efficiency. The study found that when the crushing is 0.6 mm, the metal can basically reach 100% dissociation, but the choice of crushing method and grade depends on the subsequent process.
1.2 Sorting
Separation is to use the difference in physical properties such as material density, particle size, conductivity, magnetic permeability and surface characteristics to achieve separation. Currently widely used are wind shaker technology, flotation separation technology, cyclone separation technology, float-sink separation and eddy current separation technology.
2. Supercritical technology processing method
Supercritical fluid extraction technology refers to a purification method that uses the influence of pressure and temperature on the solubility of supercritical fluids to perform extraction and separation without changing the chemical composition. Compared with traditional extraction methods, the supercritical CO2 extraction process has the advantages of environmental friendliness, convenient separation, low toxicity, little or no residue, and can be operated at room temperature.
The main research directions on the use of supercritical fluids to treat waste PCBs are concentrated in two aspects: First, because the supercritical CO2 fluid has the ability to extract the resin and brominated flame retardant components in the printed circuit board. When the resin bonding material in the printed circuit board is removed by the supercritical CO2 fluid, the copper foil layer and the glass fiber layer in the printed circuit board can be easily separated, thereby providing the possibility of efficient recovery of the material in the printed circuit board . 2. Directly use supercritical fluid to extract metals from waste PCBs. Wai et al. reported using lithium fluorinated diethyldithiocarbamate (LiFDDC) as a complexing agent to extract Cd2+, Cu2+, Zn2+, Pb2+, Pd2+, As3+, Au3+, Ga3+ and simulated cellulose filter paper or sand. According to the results of Sb3+ research, the extraction efficiency is above 90%.
Supercritical processing technology also has big defects such as: high selectivity of extraction requires the addition of entrainer, which is harmful to the environment; relatively high extraction pressure requires high equipment; high temperature is used in the extraction process and therefore high energy consumption.
3 Chemical method
Chemical treatment technology is a process of extraction using the chemical stability of various components in PCB.
3.1 Heat treatment method
The heat treatment method is mainly a method of separating organic matter and metal by means of high temperature. It mainly includes incineration method, vacuum cracking method, microwave method and so on.
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