NUST MISIS scientists, together with JSC "Shchelkovo Plant of Secondary Precious Metals," developed an innovative cascade method for purifying silver from spent batteries used in submarines and military aircraft. Secondary use of pure precious metal from one such battery can help save up to 500 million RUR for creating a new one.
In some versions of submarines and military fighters, huge alkaline batteries weighing about 14 tons and capable of operating up to 12 years uninterruptedly, are used as an electro-chemical energy source. Each of these devices uses 7 tons of pure silver plates, which, after being spent in terms of energy resource, goes to refineries (industrial processing of precious metals), where it is purified and prepared for reuse.
Recycling of such heavy-duty "strategic" batteries in 100% of cases falls into the sphere of state defense order, as the resulting silver is used for the manufacture of new batteries in the interests of the Russian Navy. The required quality of the metal from which the raw material for the battery is produced is strictly regulated by GOST (state standards), and the purity of silver should not be lower than 99.99%.
However, in the last decade, local manufacturers of silver-zinc batteries added 10%-15 % lead to the silver. This lowers the costs and does not affect the performance of the product, but almost completely blocks the process of subsequent recycling of the battery.
To solve the problem of extracting lead from the silver, specialists from NUST MISIS Department of Non-Ferrous Metals and Gold developed a fundamentally new technological scheme for processing silver-zinc batteries containing lead.