How To Refine Gold Scrap To 99.99 Percent Purity

Direct Fire Refining

Real gold is not afraid of fire. The simplest way to refine gold is to melt out everything that is not gold, which leaves high purity 99.9% gold. This is also the oldest method of refining gold.

Cyanide Dissolution

Gold can be refined by cyanide dissolution. Cyanide has a strong dissolving ability and many materials dissolve on contact with it, while gold does not. Compared with other methods this route reaches very high purity, and there is no problem reaching the 99.9% pure gold standard.

Aqua Regia Extraction

Circuit boards can be collected to extract gold. Remove the motherboard from the circuit board, grind it into powder or small pieces and soak it in aqua regia. Filter the liquid, then add a reducing agent to reduce the gold out of solution. Filter and clean to obtain the final gold.

Heated Concentrated Nitric Acid

Pour concentrated nitric acid into a beaker, add the scrap gold, and heat the beaker in a furnace. Keep heating and adding nitric acid to dissolve the other impurities in the scrap until only the gold is left undissolved. What remains is pure gold.

Sulfuric Acid With Hydrogen Peroxide

Mix sulfuric acid and hydrogen peroxide in a ratio of one to one, then put the scrap gold into the solution and wait for the reaction to complete naturally. The yellow metal obtained afterwards is pure gold.

Electrolysis From A 95 Percent Gold Anode

An electrolysis machine refines 95% gold to 99.99% gold. Gold of more than 95% purity is used as the anode, titanium sheet or pure gold as the cathode, and chloroauric acid solution as the electrolyte. A DC, AC or superimposed DC supply dissolves the 95% gold at the anode so that pure gold precipitates at the cathode.

Where Electrowinning Fits

• Electrowinning comes before refining: it takes gold out of stripping liquor, plating solution, carbon desorption eluate and cyanide leach liquor as solid metal at 95-99.8% purity.
• That recovered gold is then taken to final purity by one of the refining routes above.
• Our electrowinning machines bring residual gold in the treated solution below 2-10ppm.

Conclusion

The right route depends on what the scrap is, how much of it you have and what purity your buyer requires. If your gold currently sits in a solution rather than in a solid, electrowinning is the step that comes first.