The main methods for recovering silver from waste film and printing paper are incineration and dissolution. I. Incineration This method is widely used to process large quantities of film and paper. Known as the 10-GSX incinerator developed by the US Air Force Weapons Laboratory with a daily processing film of 6.8kg (Fig. 1), the US Air Force Strategic Reconnaissance Center invented in 1970, using propane as fuel, daily processing film and paper 362kg. The 1150 incinerator (Fig. 2) and the large incinerator designed by Kodak, the largest photosensitive material manufacturer in the United States, to process 2041 kg of film per hour. Although the incineration method destroys the high-priced base, it is also easy to cause the loss of silver in the smoke, but this method has the advantages of large volume, low cost, and easy operation. To reduce the loss of silver in soot, Kodak's large incinerator consists of two combustion chambers equipped with a cooling and dust collection system. This type of furnace is to slowly burn a film and paper like a small amount of air in the first combustion chamber. And in the second combustion chamber, the excess air is supplied to completely combust the combustible gas, the temperature can reach 750 ° C, and the silver in the flue gas is recovered by the electrostatic precipitator after the water spray is cooled to 316 ° C, and the produced ash is incinerated. The ash content of the film contains 46% to 52% of silver, and the ash content of the paper contains 0.6% to 0.7% of silver. The collected soot can be smelted in an electric arc furnace. It can also be dissolved in dilute nitric acid, precipitated with hydrochloric acid, and then smelted with sodium carbonate, or dissolved in dilute nitric acid and sent to electrolytic silver extraction. Figure 1 10-GSX type incinerator 1-second combustion chamber; 2-assisted burner; 3-secondary combustion chamber; 4-exhaust gas; 5-ash tray; 6-spray nozzle Figure 2 1150 type incinerator If the film is incinerated at (500 ± 5) °C, the obtained film ash is firstly washed with 4% NaOH solution, and the leaching residue is washed with hot water, and then treated with a 2 mol/L sulfuric acid solution containing 10% H 2 O 2 . Leaching the slag for 2 h allowed 91.75% of the silver to enter the solution. Second, the dissolution method (1) Nitric acid dissolution method. The film was added to a 5% HNO 3 solution, heated to 40-60 ° C for 10 min, and the silver was completely dissolved from the film. (2) Acetic acid method. This method is to cut the waste film, add acetic acid to dissolve at 32 ~ 38 ° C, silver into the solution. The silver in the solution is extracted by electrowinning. (C) Potassium weight chromium catalysis. This method is chopped film disposed hydrochloric acid or bromine in potassium dichromate was added as a catalyst, at this time the film has been converted to the reducible silver i.e. the silver halide. It is dissolved in sodium thiosulfate and sent to the electricity to extract silver. However, this method produces sewage due to the addition of dichromate, and the conversion process of dichromate can be completed in only a few seconds, which causes difficulty in operation and thus easily affects the recovery rate of silver. (4) Alkali dip method. This method involves digesting the comminuted film in 10% NaOH solution to transfer the silver into the alkaline solution. Further, sulfuric acid is added to neutralize to pH 6 to 7, and silver forms a silver sulfide precipitate. (5) Protease decomposition method. The method is to dissolve the film with a protease-containing pH 6.8-7.2 aqueous solution at 30-70 ° C, so that the protein in the substrate can be decomposed into a peptide and a chloro acid, and the silver layer on the substrate is detached to obtain silver slag. . Under the same conditions, an aqueous solution using chymase, amylase or lipase is also effective. When this method is used to process the photosensitive and washed film, if the silver halide residue is to be obtained, it should be treated with a solution of dichromate and hydrochloric acid to convert the reduced silver on the film into silver chloride. Treatment with protease or the like. In addition, use of organic solvents aryl ether, benzophenone dicarboxylic ether acetate and the like, was dissolved in 15min film pieces 165 ~ 225 ℃, the base polyester can dissolve, to obtain a metallic silver and silver halide precipitation. The silver halide precipitate obtained by the above various methods can be stirred and leached with silver in an aqueous solution containing 200 to 300 g of sodium thiosulfate, 30 g of sodium sulfite, and 30 mg of glacial acetic acid. The leachate is sent to the electricity to extract silver. Mounted Adaptor,Power Supply Ac To Dc,Power Supply Plug Adapter,Wall Mount Power Adapter Dongguan O-Ray Power Supply Technology Co., Ltd , https://www.oraytek.com