Basically, Au, Ag, Sn, Pd, Cu is probably the right sequence of commodities value in e-scrap material recycling. Which metal to recover is usually depends on the operator’s facility and technical capacities etc.
Eco-Goldex provides a sequential stripping procedure that will help the operation to recover multiple metal commodities in sequence:
- Surface Au-Ag-Pd stripping
Surface Au-Ag-Pd refers to those precious metals that are plated on the surfaces of electronic components such as the golden fingers on RAM, the pins of CUP, connectors, all kinds of pins and the plated wide print circuits on the telecom board.
These surface gold/silver/ palladium can be easily stripped off with Eco-Goldex E series agent solution.
- Solder Stripping
Many recycling operators haven’t noticed the economic importance of solder in e-scraps. Solder (mainly composed of Tin(Sn) and some Ag and Pb) can be easily recovered through either hydrometallurgical method or thermal process (heavy smoke pollution). Eco-Goldex provides its own hydrostripping method that can easily strip Solder on PCB, at the same time to lose those components attached to PCB such as IC chips, capacitors etc, most of the component s will fall off the PCB.
After the solder stripping step, the PCB will become bare boards. these bare PCBs can be either further crushed and pulverized to recover copper and epoxy/plastic fibres that can realize zero disposal in the recycling process. The pop-off components will then pass a screening mechanism that sorts different components into different slots. one of the slots will receive IC chips.
- Internal Au-Ag-Pd leaching
The IC chips collected from the solder stripping step are then crushed and pulverized into about 200 mesh powder. The IC chips powder is then leached in an agitating tank in there gold/silver fine particles will be leached out into solution. Through a compressing filtration process, the pregnant solution from the leaching solution will be separated from the IC hips powder sludge. The pregnant solution is then sent back to the electrowinning machine to recover gold/silver/palladium.
Eco-Goldex has analyzed gold/silver/palladium grades in several different common IC chips and bare PCB boards after stripping.
Results indicate that all the IC chips container high-grade gold, some of them contain considerably high silver. Palladium grade is not impressive or a high as claimed by some operators.
Our conclusion is that for most hobbyists, it will be good enough to recover Au-Ag, Pd can be counted as a credit if the process quantity of high. The bare PCB has not significant value since Au-Ag-Pd is low.
Below is a table showing assay results of Au-Ag-Pd (all in ppm unit) grade in various IC chips. These IC chips powder are digested in AR to ensure all metals are completely dissolved. AR solution is then assayed for Au-Ag-Pd concentration with AAS (Atomic absorption spectrometry).