A PROCESS FOR OBTAINING SILVER POWDER OR SILVER INGOTS STARTING FROM PRIMARY OR SECONDARY SOURCES.

摘要

The present invention discloses a non-polluting simple process, for silver recovery starting from primary or secondary sources of this metal. The process initiates with the silver dissolution. When it is desired to recover the metal starting from primary sources it is preferably to solubilize it with the use of sodium or potassium cyanide; while when it is desired to recover the metal starting from secondary sources (slags, radiographies, etc.) it must be use the dissolution with diluted nitric acid. Once the silver is in the solution, a catalyst is added and subsequently the silver precipitation is performed introducing a metallic electrode which can be of silicon, Fe-Sn, aluminum, zinc or copper. The final product is metallic silver ingots with purity higher than 99%, which depends on the number of washes and on the process of metal melting. It can also be obtained fine silver powder or silver suspensions performing the dispersion in a high energy SPEX mill. When the silver recovery starting from primary sources is done, the process has to be carried out in closed tanks in order to avoid leaks of highly toxic hydrocyanic acid. Despite of the previous limiting, the advantage of this process in comparison with the conventional ones is that the recovery of each of the by-products decreases the operation costs and avoids the pollution of the environment.