Is it possible to recycle PCB boards?
PCB are present in most electronic devices found nowadays all around the world. While they brought incredible innovation, their recycling is also a problem.
The International Labor Organization (ILO) points out that some 40 million tons of electronic waste (including computers, mobile phones, printers, etc.) are produced every year. The prospect is that this amount will increase even more over time, as electronic devices with new functions and more attractive designs are constantly appearing, stimulating new purchases from the consumer without the old product being out of date.
Being present is most electronic devices, Printed Circuit Boards, also known as PCBs, are among the most discarded parts. They are made up of a plastic board and fibrous materials (such as plastic polymers) and a thin film of metallic substance (copper, silver, gold or nickel). These films form “tracks” or “paths” that will be responsible for the electrical conduction done by the electronic components.
They can also have other materials in their composition, such as alloys, which have distinct melting points, thus allowing for manipulation and arrangement. There are several alloys available to be used, such as cerrobend, low melting point alloy or fusible alloys.
Recycling electronic waste is much needed, because of the chemical components in its composition, with some of them being toxic – they can cause problems if they are disposed of incorrectly. For PCBs specifically, their recycling process involves quite some steps.
It starts with a pre-treatment system that aims to separate metals, polymer materials and ceramics. After this step, the metals are sent to the metallurgical refining process. The techniques that make up this process are: comminution, classification and separation.
Comminution is the technique used to reduce particle size and release metals for future concentrations. In the classification step, the material particles obtained by the previous process must be separated or classified according to their size. After the steps of comminution and classification, the enrichment of the material takes place by means of separation techniques: the parts that are interesting for the refining process of the metal are separated, discarding any impurities.
In the case of circuit boards, the difference in electrical conductivity between metals and non-metals is a fundamental condition for the good result of the technique. Non-conductive materials (polymers and ceramics) can be separated from conductors (metals). Some techniques employed for this purpose are explained below.
It is a metallurgical process that uses high temperatures to produce pure metals, alloys or intermediate compounds. Pyrometallurgy requires high energy consumption to reach the appropriate temperatures for each stage of the process. There are several steps in the process, from the drying of the raw material to the refining of the final product.
The chemical transformation step to be used will depend on the material in question. The best known are calcination (decomposition by heat in the presence of oxygen), roasting (calcination applied to sulphides) and pyrolysis (decomposition by the action of heat in an environment with little or no oxygen). Some of the major problems in the use of pyrometallurgical processes are the possibility of emission of toxic compounds such as dioxins and the high energy consumption.
It consists of the separation of metals. Some of the advantages of this method are the energy savings and the lower pollution of the environment.
It is a process of refining metals through electrolysis. During electrolysis, metals without the impurities undergo electrodeposition, in which metals such as copper, zinc, cadmium, aluminum, precious metals, among others, can be recovered with a high degree of purity;
This process uses the action of microorganisms and minerals to recover valuable metals. This process requires a lot of time and metal needs to be exposed to microbial action.
Where to recycle?
If your computer and its PCBs are not broken but only technologically lagged, look for specialized places that accept donations of these items. You can also resell those components on the Internet, for example. However, and regardless of the final decision, always be sure that the final destination to be given to these materials is a proper one, always avoiding to harm the environment.