Precious metals are widely used in people's daily life. What belongs to precious metals? What are precious metals?

Precious metals are gold Au, silver Ag, platinum Pt, palladium Pd, strontium Sr, osmium Os, rhodium Rh and ruthenium Ru. These metals have very few stocks on the earth, and the extraction methods are complex. However, precious metals are widely used, such as electronic components, jewelry, high-tech equipment, electronic equipment, instrumentation, electronic components and household appliances. A large number of waste household appliances and electronic equipment are eliminated every year, A large number of precious metals can be extracted from these obsolete materials, so we asked how to extract precious metals from materials with precious metals. Here we summarize three methods:

First: new process of electrolytic silver stripping

Electrolytic silver stripping equipment is adopted, with graphite plate as cathode and stainless steel drum as anode. There are many fine holes on the drum. Sodium citrate and sodium sulfite are electrolytes. Silver plated pieces enter from the head end of the drum and are sent out from the tail end of the drum. The silver on the surface layer of the plating piece enters the electrolyte, and the substrate of the plating piece is completely undamaged and can be returned to the new electroplating application. The recovery of silver is 97-98%, and the purity of silver powder is 99.9%.

The second type: recovery and application of waste silver zinc battery

The waste silver zinc battery contains 52.55% silver and 42.7% zinc. Zinc is the negative electrode, and silver oxide is the positive electrode, which is coated on the copper network framework. Dilute sulfuric acid was used to separate zinc and copper, and silver powder was used to melt ingot indirectly. When dilute sulfuric acid is used for copper leaching, oxidant is used. Zinc sulfate is consumed by concentrated crystallization of zinc containing solution, and copper sulfate is consumed by concentrated crystallization of copper containing solution. The recovery rate of zinc is more than 98%, the recovery rate of silver is 98%, and the purity of silver ingot is more than 99%.

Third type: recovery of silver from waste film

The silver emulsion layer on the color film was eluted by dilute sulfuric acid solution, silver halide was precipitated by heating with chlorine salt, and organic matters were removed by chlorination calcination or washing with organic solvent. Pure silver was recovered by suspending sugar solid in alkaline medium. The purity of silver is 99.9% and the yield is 98%.

Sodium thiosulfate solution is used to dissolve silver halide on the waste film. Inhibitors are used to prevent the dissolution of gelatin on the film during the dissolution process. Silver is recovered from the solution by electrolysis and the film base is recycled for application. The silver leaching rate is more than 99%, the recovery rate is 98%, and the silver purity is 99.9%. This method has been applied to industrial consumption.