A group of researchers from Kazakhstan reports using biodegradable polymers as binders for printed circuit boards (PCBs) is instrumental to advancing e-scrap recycling.
‘The use of biodegradable and easily recyclable polymers as binders for printed circuit board manufacturing opens new perspectives for both environmental protection and resource conservation and aims to maximise the recovery of valuable materials like gold and for reuse,’ says project lead Arman Tirzhanov of Karaganda Economic University of Kazpotrebsouz.
He estimates that a tonne of used PCBs contains on average 130 kg of copper, 1.38 kg of silver, 0.35 kg of gold and 0.21 kg of palladium. Precious metals can account for more than 80% of the product’s economic value.
After conducting tests on a series of PCBs created at the university’s laboratory, tetrahydrofuran appeared to be the most efficient solvent for PCB disposal. The chemical is not classified as a “hazardous” solvent, has no carcinogenic effect and is not prohibited for use in the pharmaceutical industry for the manufacture of medical devices.
Tirzhanov also points out that tetrahydrofuran can be easily distilled from polylactic acid (PLA) and reused. For sample recycling, the PLA-PCB was placed in a container of solvent tetrahydrofuran and placed in an ultrasonic bath. This method allowed complete separation of the binder, copper tracks with electronic components and filler (fibreglass) from each other, without using additional manual, mechanical and thermal processes.
‘The process of the electronic device recycling was completed completely in 30 minutes,’ Tirzhanov concludes. The PLA solution in tetrahydrofuran was evaporated to dryness, in a rotary evaporator in a vacuum at a water bath temperature of 40 °C, resulting in 98% of the chemical being recovered.