How to extract silver from waste fixing solution by replacement method

Metals commonly used to replace silver from waste developer are: iron, copper, aluminum, zinc, cadmium and so on. Various silver recovery devices made of this raw material have applied for many patents at home and abroad. Kodak silver recycling barrel 1 is typical and widely used abroad. The principle is as follows: Ag2(S2O3)+Fe→2Ag+Fe2++S2O32- The recycling barrel of HKUST Silver consists of a replacement barrel and a circulation device. The replacement barrel is made of plastic and filled with steel wool. The waste bleaching solution passed through the recovery barrel at the flow rate of 20L/h, and the yield could reach 99.5%. The recovery process is continuous and very simple. The waste liquid flows through the barrel, while the silver remains in the barrel. The factory is responsible for the smelting of silver and the replacement of old barrels. This method is the main method to recover silver from photographic waste liquid abroad.

Some people put forward to replace steel wool with iron filings, but it is easy to cause liquid flow blockage; It has also been suggested to spray sponge iron powder with wine to make it adhere to glass fiber felt; Others coated polystyrene beads or polyurethane foam with iron powder to solve the problem of blocking liquid flow when iron powder adhered. Ethylene hydrocarbons or tertiary amino or metal salts, preferably copper salts and cadmium salts, are used as inhibitors to solve the problem of iron corrosion. A few hospitals and photo studios in China use this method to recover silver. This method can extract silver quickly, but the solution is polluted. Well, I forgot the ingredients of the fixative. Do you know that?/You know what? If I knew, I should be able to push it out.