25-01-2013, 02:26 PM
THE EXTRACTION OF HEAVY METALS BY MEANS OF A NEW ELECTROLYTIC METHOD
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ABSTRACT
The extraction of metals in known metallurgical methods is pursued on the basis of separating as much as
possible the desired metal’s content from the ore concentrate, in the most economical manner. When these
principles are also applied to the extraction of heavy metals, the related environmental factors do not readily
meet with requirements. Today, an acceptable extraction technology for metals must satisfy the need to
produce the deep separation of metals from their source in both economical and environmentally safe manner.
This pertains to the direction of our ongoing research and development, among others in the field of
environmental remediation. Earlier, we successfully addressed in an environmentally safe manner the
selective extraction of radioactive isotopes from liquid radioactive wastes, produced at Armenia’s Metzamor
Nuclear Power Plant and implemented a functioning LRW station at the NPP. Currently, we extended our new
electrodialysis-based electrolytic method in a laboratory scale, for the extraction and deep separation of
different metals, including the heavy metals. Our new method, its efficiency, economy and full compliance
with environmental issues will be presented.
INTRODUCTION
A newly developed hydro-chemical metal extraction and purification system, presented in this paper, is a result
of proprietary work performed at AREV Scientific-Industrial Company in Yerevan, Armenia. This technology
was initially developed especially to secure the large volume of Liquid Radioactive Wastes (LRW), typically
produced at Armenia’s 840-MWe Metzamor Nuclear Power Plant (NPP) or at any one of the more than fourhundred
NPP operations worldwide. The extraction of metals from ore concentrates, from industrial waste
waters, mineral-rich spring waters, NPP-produced liquid radioactive wastes, and in grounds contaminated by
industrial wastes, in a complete, economical and environmentally safe manner, so far has not been possible,
when employing the known conventional methods.
In particular, overcoming these deficiencies in a new technology would permit the efficient and economical
extraction of metals from ore concentrates and the processing of globally accumulated huge quantities of liquid
radioactive wastes, to take place entirely in an environmentally clean manner. AREV’s new technology
development can be applied to the extraction and purification of any metal from any one of the above sources.
However, we specialized to demonstrate the production of 99.99% pure molybdenum, copper, zinc and lead
metals from Armenia’s ore concentrates and to the industrial-scale processing of LRW.
NEW, ENVIRONMENTALLY SAFE PROCESSING OF LRW AT NUCLEAR POWER PLANTS
In the operation of nuclear power plants large volumes of LRW are produced, having low to medium level of
radioactivity that must be processed efficiently, to reduce their volume significantly, to permit the safe and cost
effective storage of the residual material. The current method of processing LRW is based on dehydrationevaporation
that leaves behind large volumes of solid radioactive waste. The radiotoxicity of this waste is
sufficiently long lived that a safe storage of a few hundred years is still required. This situation can be
removed if in the waste-product stream the long-lived radioactive isotopes are removed selectively and
completely. Research to accomplish this is being pursued in several countries. Results are insufficient to
solve the problem fundamentally, by removing 100% of the long-lived radioactive components.
NEW, ENVIRONMENTALLY SAFE EXTRACTION AND REFINING OF METALS FROM MINERAL ORE CONCENTRATES
To demonstrate the superiority of our new method, to extract and refine metals from mineral ore concentrates
[23], we again chose to employ a cesium-based electrolytic solution in the amount consistent with those
concentrations expected in a hydrometallurgical process. Accordingly, we used 20 g of CsNO3 dissolved in
100 ml of water to proceed with a laboratory-scale demonstration. Following Figure 2, the input electrolyte
solution (1) was pumped into the water tank (2) at a rate of 10 ml/min, and introduced into the central
processing chamber of the Electrodialysis Separator. As a result of the ED process, anions are accumulated in
the acid-solution tank (3), while the cations are adding into the base-solution tank (8). The base solution was
processed further in an especial Electrolysis Concentrator (10), to accumulate and refine the selected metal.
The amount of metal extraction is linearly proportional to the current flowing in the Electrodialysis Separator.
Following 15 minutes of operation from when the electrolyte was introduced, the electric current in the ED
unit (4) dropped to a residual value of 0.007 A, from a starting current of 5 A. The amount of extracted metal
was also monitored by the amount of current flowing in the especial Electrolysis Concentrator (10). Following
the extraction of the cesium metal product in solid powder form, the input electrolyte was reconstituted by
dissolving in nitric acid, from which 19.77 g of CsNO3 was reestablished, as compared to the original 20 g.
This difference was well within the measurement error.