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In some versions of submarines and military fighters, huge alkaline batteries weighing about 14 tons, 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.
An innovative cascade method for purifying silver from spent batteries used in submarines and military aircraft that has been developed ensures secondary use of pure precious metal from one battery for creating a new one.
The technology which enables the recycling of previously non-recyclable waste was developed by scientists from the Russian technical university National University of Science and Technology (NUST) MISIS Department of Non-Ferrous Metals and Gold, together with JSC “Shchelkovo Plant of Secondary Precious Metals”.
Usually, the 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. However, in the last decade, local manufacturers of silver-zinc batteries add 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, the scientists developed a fundamentally new technological scheme for processing silver-zinc batteries containing lead.
In a two-stage process the silver is melted, and as a result – lead is removed and a commercial product of 99.99% purity is obtained from raw materials with 85% silver content. The pure product corresponds to all GOSTs (state standards) and is suitable for the manufacture of a new battery.
Currently, the technology has been successfully implemented at one of the refining domestic enterprises – JSC “Shchelkovo Plant of Secondary Precious Metals”. For its implementation, no additional equipment was required, except for a low-cost installation of high-speed melt cooling unit, according to eurekalert.org.