Acidic water contains platinum, how to reduce it?

Platinum reacts with aqua regia to form corresponding salts.

A substance that evaporates to obtain salt.

And then calcined at high temperature to produce the corresponding metal! ! !

Nitrate of the metal behind H in the metal activity table is calcined at high temperature to generate the corresponding metal! ! !

Recovery and purification methods of precious metals

I. Recovery of silver

There are several ways to recover silver:

1. Electrolysis: This method is the same as electroplating, except that the area of anode (stainless steel) is small and the cathode surface is particularly large, so it is not necessary to clean the cathode, mainly for the convenience of silver withdrawal.

2, chemical method:

(1) Collect the silver scraps from the mold, dissolve the silver scraps with nitric acid, and heat to drive away the nitric acid (no smoke).

(2) Filtering the solution to remove impurities such as dust and sawdust, and washing the filter paper with deionized water for several times.

(3) Dilute the solution by 3-5 times, and put the iron sheet or copper block into the solution, and the silver will be replaced soon. Always stir the solution.

2ag++(-2e) 2ag (silver)

Copper -(-2e) copper ion

(4) If the copper block no longer reacts (that is, silver no longer precipitates), pour the solution into another beaker with sponge silver at the bottom, then filter, and then rinse the sponge silver with water until it is neutral (PH test paper test).

(5) Put the washed sponge silver and filter paper into the pot, and ignite the silver block with a musket.

(6) Recovering silver from silver decoction (chemical polishing solution)

The main component of polishing solution is potassium cyanide and hydrogen peroxide, so (silver) can only be precipitated after cyanide is broken. Pour the polishing solution into a cup, add nitric acid to make the PH value around 5, and then boil it in an electric furnace for 1-2 minutes (silver) precipitation.

Filter and cleaning that precipitate silver to be neutral, and sintering the silver block.

Second, gold recovery.

1. Electrolysis: Same as silver electrolysis.

2, ferrous sulfate reduction method

3, sodium sulfite reduction method

4, sodium bisulfite reduction method

5, zinc powder reduction method

6, hydrogen peroxide reduction method

7. Mercury enrichment method

8, musket blowing method

This method is based on the principle that the proportion of gold is heavy and it is not easy to be blown off. The treated waste is collected in a burning pot and blown away with a musket. The waste is blown away, and the gold is left at the bottom of the pot, and then burned into gold nuggets.

Pay attention to the size of the wind.

The recovery methods mentioned in 2, 3, 4, 5 and 6 above are all chemical methods.

First of all, the waste collected after the execution of the mold should be dissolved with aqua regia. After dissolution, the ash removal method and other insoluble substances are filtered. Dilute the solution with water for 3-5 times, and add sodium sulfite or sodium bisulfite or zinc powder. The purity of pure gold reduced by these methods is low and needs to be purified repeatedly.

If gold is produced by hydrogen peroxide reduction, it will be grayish yellow. This method has high purity, but it is complicated. The specific method is as follows:

1. After collecting the mold polishing ash, dissolve it with aqua regia (3 parts hydrochloric acid+1 part nitric acid) and dilute it with appropriate amount of water. Remove insoluble matter (lime sand, etc.). ) and wash the filter paper to yellow.

2. Add an appropriate amount of sulfuric acid (industrial grade) to the filtrate, and the solution of about 100 ml is slightly cooled with 200 ml of sulfuric acid.

3. Slowly add hydrogen peroxide to reduce to metallic gold. The amount depends on the gold content, and white smoke comes out when heated. Yellow gold mud precipitated out.

4. Pour the clear liquid into another container, mash and filter the gold mud under it (dilute it with appropriate amount of water before filtering to avoid filter paper rot) and rinse the gold mud to neutrality.

5. After the gold mud is crushed, add a proper amount of nitric acid to boil for 1-2 minutes, further remove impurities, and then filter and clean.

6. Burn the filter paper and gold mud into gold nuggets with a musket.

Note: ① The white smoke solution is still yellow, so it needs to be reduced again by adding hydrogen peroxide until the solution turns white (sulfuric acid is not needed at this time). ② The temperature should not be too high when adding hydrogen peroxide.

Three. Precious metal recovery after K-gold die casting

18K gold jewelry is generally composed of gold, silver, palladium and other metals, of which gold accounts for about 75%, silver for about 5% and palladium for about 20%.

Recovery method:

1, the gun will blow off the ash powder (soot blowing method), and the gold, silver and palladium will be sintered with the gun.

2. Use aqua regia for deep dissolution (the amount of aqua regia depends on the dissolution of gold nuggets). Tetrachloropalladium acid, silver chloride and gold fulminate are generated in the solution.

3. Add a proper amount of water to dilute silver chloride, so that it can be separated from tetrachloropalladium acid and gold fulminate. Gold and palladium are in solution, and silver chloride precipitate is washed with water to neutrality (filtrate cannot be dumped).

① Adjust the PH=9 of silver chloride precipitate to about 9 with ammonia water. Reduction to silver powder with hydrazine hydrate. (hydrazine hydrate n2h4.h2o);

(2) filter and washing that sil powder to be neutral, and burning the silver pow into silver blocks. Note: Before adding hydrazine hydrate (after ammonia water), if there is still sediment in the solution, that is, metal ash powder or other impurities. Filtering will discard the sediment. Hydrazine hydrate was added to the filtrate to reduce silver.

Gold recovery:

(1) Heat and boil the filtrate recovered from silver to drive away more nitric acid (i.e. nitrogen oxides). (There are gold and palladium in the solution)

(2) Dilute the solution with water 1-2 times, and add umbrella powder to make sponge gold.

(3) filtering out sponge-like gold, washing it with water for several times until it is neutral, and sintering it into gold nuggets with a musket.

Recovery of palladium:

① In the filtrate after recovering gold, adjust the pH value to 8-9 with ammonia hydroxide.

(2) adding hydrazine hydrate to reduce palladium to obtain metallic palladium powder, filtering, washing with water to neutrality, and drying and storing.

Recovery of platinum:

Nowadays, platinum jewelry is increasingly favored by customers. In the process of processing, some wastes will inevitably appear, but these wastes contain a certain amount of precious metals such as platinum, palladium and rhodium. It is a pity if they are dumped, and the only way is to recover precious metals from waste.

There are many kinds of platinum, mainly including:

Pure platinum without diamonds

Platinum-rhodium-platinum-palladium is diamond-encrusted jewelry.

Platinum cobalt blue

Recovery of powder after platinum-rhodium alloy processing

Common methods:

1. Dissolve the powder with aqua regia, dilute it with water, and filter the waste residue. The filtrate contains platinum, rhodium and other metals.

2. Neutralization of filtrate (ammonia hydroxide) solution 10- 15% makes rhodium precipitate into Rn(OH)3 (rhodium oxychloride). Wash the precipitate with water to neutrality. Can be made into rhodium plating solution.

Recovery of rhodium plating recovery solution;

Concentrating the volume of the rhodium-plated recovery solution, neutralizing the concentrated recovery solution with ammonia water until the pH value is 7-8, precipitating rhodium hydroxide, boiling the precipitated solution for several minutes, removing the ammonia smell, filtering the rhodium hydroxide, and cleaning to neutrality.

Rhodium hydroxide is diluted with sulfuric acid solution. So as to obtain rhodium sulfate plating solution. The electroplating solution is treated with water and activated carbon to further remove impurities.

Filter analysis. Measure the content of sulfuric acid and rhodium. Can be added into a rhodium plating tank. (as a supplementary solution for rhodium plating)

3. Ammonium chloride is added into the filtrate to make platinum precipitate filtered and washed clean.

4. Burn the sediment into platinum sponge.

If it is a (platinum)-(palladium) alloy, this method produces a (platinum)-(palladium) coprecipitation, which is washed and fired into a (platinum)-(palladium) alloy block.

In short, in the process of making jewelry, no matter which department, we should pay attention to openly collecting all kinds of metal powder. It is best to install the corresponding equipment to minimize the loss.