Lift silver from the waste. Dilute nitric acid (HNO3) at a concentration of 6% to 8% was poured into an acid-resistant cylinder, and then placed into x-ray sheets and scattered film sheets one by one, soaked for 24 hours, and the silver film on the film was dissolved:
3Ag+4HNO3—3AgNO3+NO++2H2O
The resulting solution. According to the above method, silver can be obtained.
Operation process
1. Remove the red dan: immerse the broken lens in the caustic soda with a concentration of 8% to 10%. After 1-2 hours, the red dan will fall off, and the silver glass after the red dan will be removed (you can also add the thermos bottle glass), with clear water. Rinse until it is alkaline.
2. Dissolving the silver layer: The washed silver glass is immersed in a dilute nitric acid solution having a concentration of 10%, and silver is reacted with nitric acid to form silver nitrate. 300 kg of this dilute nitric acid solution can process 4000 kg of silver glass and become a silver nitrate solution.
3. Precipitated silver chloride: According to the volume of the obtained silver nitrate solution, about 1% hydrochloric acid having a concentration of 16% was added in a volume ratio to produce a milky white silver chloride precipitate. After clarification, the clear solution is taken and the precipitate is washed 2-3 times with water to make it neutral.
4. Reduction of silver powder: the same amount of rust-free iron pieces and the obtained silver chloride are placed alternately in the container. Add 1% hydrochloric acid with a concentration of 16% by volume, after 8-12 hours. All the metallic silver was replaced and it was grayish brown. Wash with water for 3-4 times until there is no acidity.
5. Remove the iron filings: Place the replaced silver in a wok and fry it. It is best to fry the silver powder to brown, reddish, and form a block or granule. After cooling, the iron scraps mixed in are sucked up with a magnet (magnet).
6. Furnace ingot: Put the silver powder that has been fried and ironed into the graphite crucible. Melting at a temperature of 1000-1200 ° C. Add a little sodium nitrate and borax at the same time. Used to remove other metal chlorides and impurities. When it is baked, add a small amount of straw ash. In order to maintain the adsorption and adsorption of impurities, the silver solution is poured into the mold to form silver. Each ton of silver glass can refine silver 200--450 grams. The purity is 98%.
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