Recover gold from gold-containing alloy scrap

Alloy wide range of different components, different recovery methods. Before recycling, the classification should be sorted, stacked separately, and processed separately according to the class. The process of recovering gold from waste alloys usually includes the main processes of dissolution (liquid refining), metal separation and enrichment, purification of the enrichment liquid, and metal extraction. Before the liquid preparation, the types of raw materials should be single, oil stains and inclusions should be removed, and large materials need to be shredded.

1, from the gold - gold alloy scrap recycling of antimony (arsenic gold - gold or aluminum - - Antimony)

First, boil the water with dilute aqua regia (acid: water = 1:3) to completely dissolve the gold, evaporate and concentrate until no nitrogen dioxide gas is present, concentrate to about one-fifth of the original volume, and then dilute the value to contain gold 100-150g/ L. Allow to filter. The gold in the filtrate is recovered by reduction with sulfur dioxide, and the sulfur dioxide in the residual gas is absorbed by the caustic soda solution. Wash the gold powder and dry the ingot.

The gold content in the niobium alloy is >99%, which can be directly electrorefined.

2. Recovery of gold from gold- palladium - silver alloy scrap

First, the silver is dissolved by dilute nitric acid (acid: water = 2:1), the filtrate is added with silver, and the palladium in the residue is combined with ammonia, acidified with hydrochloric acid, and then added with formic acid to produce palladium powder. The gold is then recovered from the nitric acid insoluble residue.

3. Recovery of gold from gold- platinum (gold-palladium) alloy scrap

First, use Wang aqueous solution, add hydrochloric acid to evaporate and drive the nitrate to syrup, dilute with distilled water and add saturated ammonium chloride to precipitate platinum as chloroplatinic acid ammonia. After washing with a 5% ammonium chloride solution, it was calcined to obtain a crude sponge platinum. The filtrate was reduced with ferrous iron .

Fourth, from gold - gold iridium alloy scrap recycling

铱 is a refractory metal, which can be heated with 600-900 ° C for 60-90 min with sodium oxide (and can be added with caustic soda) until it melts. The melt was poured on an iron plate to form a sheet, which was cooled and then leached with cold water. A small amount of strontium sodium salt enters the solution and most of the hydrazine remains in the leaching residue. The leaching residue is diluted with hydrochloric acid to dissolve the hydrazine, and the filtrate is filtered, and the filtrate is oxidized to a tetravalent value by a chlorine gas, and then a saturated ammonium chloride solution is added to precipitate the hydrazine as ammonium chloroantimonate. Calcination produces coarse sponge mash.铱Insoluble slag plus aqua regia gold, use ferrous reduction to recover gold.

V. Recovery of gold from siliceous scrap

It can be leached with a mixture of hydrofluoric acid and nitric acid (HF:HNO ₃ =6:1). The mixed acid (acid:water = 1:3) was diluted with water, the silicon was dissolved during leaching, and the gold was peeled off from the silicon wafer. Then, it was boiled with 1:1 diluted hydrochloric acid for 3 hours to remove impurities on the gold flakes, washed with gold flakes (gold powder), and dried ingots.

6. Recovery of gold from gold- boron -palladium (gold-boron-palladium- ruthenium ) alloy scrap

Dissolve with dilute aqua regia (acid: water = 1:3), heat slowly, add hydrochloric acid to evaporate and drive to near dryness. After cooling, it was wetted with a little hydrochloric acid, then hot water was added and the palladium was leached by heating. The mixture was filtered, and ammonium chloride was added to the filtrate to prepare ammonium chloropalladate. And calcined into a crude sponge palladium. The residual liquid after palladium is reduced with gold ferrous sulfate.

7. Recovery of gold from gold-boron- gallium alloy scrap

Boil and dissolve with rare water (Ace water: water = 1:3). The gold is then reduced from the filtrate with ferrous sulfate.

8. Recovering silver from gold-silver- copper alloy scraps

Such alloys often contain more than 60% of gold. If nearly one-third of silver is contained, gold and silver can be separated by electrolysis.

Usually, gold and silver alloys are difficult to dissolve in the liquid. If silver is appropriately added to the raw materials, gold:silver=3:1 is soluble in aqua regia and soluble in nitric acid.

When dissolved in aqua regia, gold forms chloroauric acid into the solution. Although silver forms silver chloride to hinder the dissolution of silver, it does not interfere with the dissolution of gold due to the gold-coated gold.

When the above raw materials are dissolved in nitric acid, the dissolution of silver by nitric acid is not hindered by the small amount of gold. The result of liquid production allows gold and silver to enter the solution or precipitate separately, and the gold and silver can be separated by filtration. Then, the solution or the insoluble precipitate is separately processed to produce metal gold and silver, respectively.

Nine, fire method smelting gold alloy scrap waste recovery

At present, sent melting alloy, milling - was dissolved in aqua regia, and the waste parts - peeled gold thiocyanate or ethylene iodide solution.

The gold-containing alloy is processed in an induction crucible, which is the same as silver. Since the gold content in the alloy exceeds 50%, the melt dose is not large (10% to 30% by weight of the charge). Soda ash and quartz sand are used as flux. The material is charged into a hot pot, and then heated to 1200 ~ 1250 ° C. The melt is kept for 0.5 ~ 1 h, and slowly poured into water for granulation. The obtained pellets were washed and placed in a porcelain container, and dissolved in aqua regia (1:4 ratio of nitric acid to hydrochloric acid) under heating to 80 to 90 ° C, and stirred periodically until the reaction was completely stopped. The reaction is carried out as follows:

Au+4HCl+HNO ₃ =HAuCl ₄ +NO+2H ₂ O

The resulting solution was decanted and allowed to stand for 4-6 h to flocculate AgCl. The AgCl and the solution are separated by filtration, the AgCl is dried, and sent to the smelting, and the gold is precipitated from the clarified liquid with hydrazine hydrochloride or ferrous sulfate:

4HAuCl ₄ +3N ₂ H ₄ (HCl) ₂ =4Au+3N ₂ +22HCl

The resulting gold-containing slag is washed with hot deionized water, then AgCl is washed away with a 10% NH ₄ OH solution, and AgCl forms a water-soluble complex:

AgCl+2NH ₄ OH=Ag(NH ₃ ) ₂ Cl+2H ₂ O

After that, iron and copper were washed away with a 5% to 10% H2SO4 solution. Wash the silver, copper and iron in the mud twice. The obtained sludge is dried at a temperature of 150 to 200 ° C, and nitrated at 1,250 ° C to be smelted and cast into an ingot. The ingot is sent to electrolytic refining.