Where do discarded mobile phones and broken computers end up?
Many people are unaware that these seemingly useless electronic wastes actually represent an overlooked "urban mine." Each printed circuit board (PCB) contains valuable metals such as copper, gold, silver, and palladium. With the right processing technologies, electronic waste can be transformed into reusable resources.
PCB Recycling Process
1. Component Removal: Separating Different Materials
The first step in PCB recycling is the removal of electronic components.
Modern automated dismantling equipment uses controlled electric heating, typically maintaining temperatures between 120–150°C. At this range, solder melts efficiently, allowing components to detach without causing thermal deformation of the substrate. A single dismantling line requires minimal labor and can process several hundred kilograms of PCBs per hour, ensuring both efficiency and operational stability.
2. Crushing Stage: Temperature Control to Reduce Material Decomposition
After component removal, the remaining PCB substrates are sent to the crushing stage.
A key technical consideration is heat generation during crushing. Excessive temperatures may alter the organic materials within the boards. Advanced crushing systems are equipped with temperature control mechanisms to maintain stable operating conditions and minimize thermal decomposition.
Studies indicate that after crushing, approximately 72.77% of valuable metals are concentrated within particle sizes ranging from 0.5 to 2 mm. This data provides a critical basis for optimizing subsequent separation processes.
3. Separation Stage: Physical Methods for Metal Recovery
Once crushed, the materials undergo separation to recover metals from non-metallic fractions.
Modern systems primarily rely on physical separation technologies, including:
Magnetic Separation: Extracts ferrous metals such as iron and nickel
Eddy Current Separation: Separates non-ferrous metals like copper and aluminum based on conductivity differences
Electrostatic Separation: Further refines the separation of fine particles
These processes do not require chemical reagents and generate no hazardous liquid waste, making them environmentally sustainable. With optimized configurations, high recovery rates of copper and other metals can be achieved.
Metal Composition of Waste PCBs
The metal content of waste PCBs varies depending on their source and type. Academic studies provide insight into their resource value:
Analysis of PCB samples from an e-waste facility in Malaysia showed a copper content of approximately 43.60%, along with the presence of nickel, gold, and iron.
Other studies estimate that each ton of waste PCBs contains about 100–143 kg of copper and 0.11–0.56 kg of gold.
Research also indicates that copper and lead together account for nearly 70% of the total metal content in PCBs.
