A PCB or printed circuit board has a small amount of gold along with other metals like silver, copper, palladium, tin and lead. The role of these metals is to enhance the conductivity. Gold is used mainly on connector pins, processors and chips. But, it is not on the PCB, and is rather used on connectors located inside Microchips adjoining the chip and the external electrical connectors. So, let’s see the various ways of extracting gold from printed circuit boards.
Different Ways of Extracting Gold from Printed Circuit Boards
There are various methods to remove these minute traces of gold from these circuit boards. First requirement is milling of the PCB to expose the gold in the chips. Various methods can be used to break or mill the printed circuit board. They can be broken into sizes as small as 150 mm. A wood chipper can be ideal for milling. In order to achieve finer milling rotating cylinder filler with steel balls/rods or a hammer mill is used. The degree of milling depends on the smallest size of the components in the PCB.
Using Chemicals for Extracting Gold from Printed Circuit Boards
Various chemicals have the ability to remove and refine gold such as sodium cyanide and sodium meta nitro benzene sulphonate. Sodium cyanide is the cheapest available unless you can find calcium cyanide. You will require a very dilute solution of cyanide depending upon the content of copper present, about 100 – 500 ppm. Slurry of recycle material is made in this weak cyanide solution at a pH greater than 10.This condition is extremely important.
The slurry is aerated using a cement mixer or tumbling drum. The time taken for dissolution can range from 2 hours to 2 days. Once gold and other metals such as silver and copper are dissolved, the solution is filtered off or decanted. The dissolved species are adsorbed on granular activated carbon surface or precipitated using chemicals such as zinc dust. However, Cyanide is a dangerous and highly toxic chemical. Hence it requires careful handling. It is safe to use only when handled with responsibility.
The Bottom-Line: Is It Worth The Efforts?
For extracting gold from printed circuit boards even in minute quantities, you may require a large number of circuit boards. A metric ton would approximately have 80 to 1600 grams of gold.
With evolving technology and development in PCB design, the amount of gold used for fabrication and creation of components is reduced. Moreover, before extraction you need to figure out the potential earnings involved with the amount of gold available on these PCBs, so that the cost of retrieving the gold does not exceed the cost of the gold obtained.
Hence, before extracting Gold from Printed Circuit Boards, you need to do an economic assessment on the value of the recoverable gold to make the process worthwhile.
The above-mentioned methods are moderately cost, and some more approaches are covered in the part II of this series, including the cheapest way of extracting gold from Printed Circuit Boards.
