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From 2013.igem.org

Contents 1 13-05 - 19-05-13 1.1 Gold Recovery from Electronic Waste 1.2 Precipitation of Gold from Electronic Waste 1.2.1 Protocol 1.2.2 Result

13-05 - 19-05-13

Gold Recovery from Electronic Waste

As test experiment, pins from an old CPU processor chip were dissolved.

Fig.0 Old motherboard from which we will recycle gold.

Step 1: Pins were mechanically removed and collected in a flask.

Fig.1.1 CPU from which pins will be removed.

Fig.1.2 Removed pins.

Step 2: Flask was put onto heating plate and covered in concentrated HCl.

Fig.2 Pins covered in HCl.

Step 3: HNO₃ was carefully added to the pins and heated.

Fig.3 Evolution NO2 gas.

Step 4: After several minutes of moderate heating, pins dissolved completely. The solution turned green.

Fig.4 Green solution of dissolved pins.

Step 5: The solution was carefully neutralized to pH ~6 in a step-wise manner using first 5 M, later 0.5 M NaOH.
Step 6: This led to precipitation of copper salts, indicated by the milky green coloring.

Fig.6 Milky solution following neutralization.

Step 7: In order to remove the precipitates, the solution was filtered using a buechner funnel and sterile filtrated (0.2 µm).

Fig.7.1 Filtering solution to remove precipitates.

Fig.7.2 Sterile filtering.

Fig.7.3 Filters used for sterile filteration.

Step 8: The final yellow-green gold containing solution was collected in a volumetric flask.

Fig.8Final gold containing solution.

Precipitation of Gold from Electronic Waste

Protocol

In order to evaluate optimial cultivation temperature of D. acidovorans, glycerol stock was streaked on ACM plates and incubated at RT, 30°C and 37°C ON. The next day, plates were covered with 200 µl 0.5% soft agar supplemented with 27 µl "dissolved electronic waste" solution.

Result