We are a professional manufacturer of precious metal refining equipment, offering complete process solutions for gold extraction from gold-plated waste parts. Gold coatings on plated scraps can be stripped and recovered by two mature routes: fire deplating and chemical deplating.
Fire Deplating Process
Place gold-plated scrap into molten electrolytic lead (melting point 327°C). Gold dissolves and alloys with lead. After removing the stripped base materials, cast the gold-bearing lead melt into precious lead slabs. Gold is then recovered from precious lead via cupellation or electrolysis. During cupellation, silver can be added to form gold-silver alloy. Water-quench the alloy into granular form, then perform nitric acid parting to separate gold powder. The nitric leachate can be treated with hydrochloric acid for silver precipitation.
Chemical Deplating Process
Immerse gold-plated scraps in stripping solution heated to 90°C for 1–2 minutes, so gold transfers fully into the liquid phase.
Stripping Solution Formula
Dissolve 75g sodium cyanide (NaCN) and 75g sodium 3-nitrobenzenesulfonate in 1000mL water, stir until fully dissolved for immediate use. When the stripping capacity is exhausted or gold saturation prevents further deplating, prepare fresh stripping liquor. After deplating, rinse the substrate three times with distilled water; save rinse water for reuse in future washing cycles.
Dilute each liter of gold-bearing stripping solution with 5L water and stir thoroughly. Adjust pH to 1~2 with hydrochloric acid. This pH adjustment must be operated inside a fume hood to avoid cyanide poisoning. Use zinc plates or zinc wire for cementation to precipitate gold from the pregnant solution, until the yellow color disappears. Let the mixture settle and siphon off supernatant. Wash gold powder 1–2 times, then boil in sulfuric acid to remove zinc and other impurities. Separate solid and liquid, dry gold powder, and melt-cast to produce crude gold ingots.
Electrowinning is an alternative gold recovery method for gold stripping solution. The spent electrolyte can be reused as stripping liquor after replenishing sodium cyanide and sodium 3-nitrobenzenesulfonate, though this route requires more complex equipment and operation.
High-Speed Citrate-Based Stripping Formula
Stripping liquor formulated with sodium 3-nitrobenzenesulfonate, cyanide and citrate can completely remove gold plating within only 3–5 seconds. For electrowinning: use stainless steel as cathode and graphite as anode. Operating parameters: DC voltage 6V, cathode current density 0.3–0.5 A/dm², temperature 40–60°C, electrolysis duration 4–8 hours. Gold recovery rate exceeds 99.5% with gold purity reaching 99%.
Our Advantages
We supply full sets of precious metal refining equipment matching both fire and hydrometallurgical workflows. Our systems support zinc cementation and electrowinning gold recovery, stable high gold yield, easy scale-up for small to medium recyclers. Contact us to customize your gold deplating and refining plant.
