Recycling Printed Circuit Board Wastes Through Supercritical Fluid Delaminating 2011 Final Report

Supercritical fluid technology is a new technology being extensively studied in the past two decades. The research on application of supercritical fluid to PCB recycling is an attempt to equip the recycling industry with the state-of-the-art technique to achieve better economic benefits and environmental objectives. Through the exploratory research and the systematic study, it is proved that the SCF CO2 treatment of PCBs is promising in decomposing bonding materials between various PCB layers to cause delaminating of the boards. This idea is contributive to the research on PCB recycling techniques because of its innovation on recycling processes without destroying the recoverable materials. This could make the subsequent process much easier for recovering of the materials. As a promising technique, the SCF process is potentially characterized with some advantageous properties: A) Automatic separation: With bonding materials decomposed in SCF treatment, the PCB layers is possible to be automatically delaminated with aid of foaming effects induced by rapid depressurizations during SCF treatment of PCB scraps; B) Higher recycle rate: When metals and fiberglass are automatically separated out, they can be efficiently collected and sent to different processes to be recovered. This process will have a higher recycle rate of metals and fiberglass when compared with shredding and incineration processes; C) Better recycle grade: The metals and fiberglass are separated while they are still in their original forms. This enables metals and fiberglass materials to be completely separated in the collection process. Accordingly, the subsequent process may achieve a better recycle grade in metal recovery and fiberglass recycling. Their recycle value hence will be highly improved; D) Environmental benign: With CO2 mainly employed in the recycling process, the SCF treatment of PCB scraps release few hazardous materials to the environment. The gas could be easily cleaned by a paper filter to prevent the dissolved resins from directly entering the environment. Employment of water as co-solvent can enhance the environmental performance of the process; E) Energy saving: Compared with the shredding process, the supercritical fluid process consumes less energy, which would lower the total cost for PCB recycling processes and accordingly, enlarge the recycling revenue for hundreds of electronic recyclers. Equipped with the above five major advantages, this alternative process for PCB recycling is worth of further research to turn it into a real industrial technique to address the economic and environmental issues in current PCB recycling industry.