METHOD FOR SILVER EXTRACTION FROM WASTE PHOTOMATERIALS

摘要

The method is used in the chemical industry for extraction and reuse of silver from photographic paper, films, plates, etc. The method is rapid, easily performed, and uses a readily available enzyme to break down the silver-containing gelatine layer, does not lead to disposal of toxic reagents into the environment, and provides extraction of over 95 percent of the silver with a minimum purity of 99.3 percent. The essence of the method consists of breaking down the silver-containing gelatine layer in the waste photographic materials using a proteolytic enzyme until a silver-containing slurry is obtained, with said enzyme being an alkaline protease enzyme. The gelatine layer can be broken down at pH 7-9 and temperatures ranging from 5 to 55 degrees C, and the resulting silver-containing slurry then undergoes pyrometallurgical processing at 1,100-1,150 degrees C, resulting in elemental silver. The flux used during pyrometallurgical processing consists of a mixture of sodium carbonate, calcium carbonate, borax, and a reducing agent in a 4:1:1:1 ratio.