The dissolution of metals used in the super alloy CMSX-4 by means of aqua regia, with the focus of recovering rhenium by means of molecular imprinted polymers

Ghaleb, Matthew Stewart (2014) The dissolution of metals used in the super alloy CMSX-4 by means of aqua regia, with the focus of recovering rhenium by means of molecular imprinted polymers. Masters thesis, University of Lincoln.

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The dissolution of metals used in the super alloy CMSX-4 by means of aqua regia, with the focus of recovering rhenium by means of molecular imprinted polymers
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Abstract

Aqua regia, which is an acid solution of hydrochloric acid and nitric acid, was used at three
different strengths, over a period of seven days, to see how effective it was at dissolving the
individual metals that are used in the super alloy CMSX-4. Tantalum, Hafnium and Titanium
could all withstand the corrosive effects and did not dissolve. The strongest strength of aqua
regia (not diluted) managed to partially dissolve the other metals, with Molybdenum being
fully dissolved. The two diluted solutions of aqua regia were not as affective, however
rhenium managed to be fully dissolved
Super alloys, which are used in industries such as the aviation and energy sectors, are a
combination of specific metals which exhibit special characteristics. When the metals are
alloyed together, they produce an alloy that can withstand extreme temperatures (over
+1000°C) and workloads over an extended period of time, without the integrity of the alloy
being affected. As technologies change different generations of super alloys have been
developed. A second generation super alloy, CMSX-4, contains 3% rhenium and rhenium
being an extremely rare element, is an expensive metal to use (around £2500 per kg).
Molecular imprinted polymers are a new separation technique that has become increasingly
popular due to their benefits of, ease of creation; low cost and extremely specific separation
abilities. The specific separation is achieved during the polymerisation process, by using a
template, identical in chemical and structure to the analyte of interest, allowing for
separation of the analyte of interest, even in the presence of similar structural and chemical
compounds.
Five molecular imprinted polymers were made, each with different concentrations of rhenium
template. They were tested to not only see if they could successfully trap rhenium, but to also
investigate if the maximum loading of the molecular imprinted polymer would increase as the
concentration of the template increased. Throughout the research, the molecular imprinted
polymers were analysed by X-Ray fluorescence to determine the presence of trapped
rhenium. The solutions that were eluted through the polymers were analysed by Atomic
Absorption Spectroscopy to identify how much rhenium was not being trapped by the
molecular imprinted polymer during the analyte loading stage and how much rhenium was
being removed during the analyte removal stage.
The research also investigated to see if a re-useable polymer was produced. The results
indicated that not only could the molecular imprinted polymer trap rhenium; it could also be
removed and then re-used again at least four times, without the maximum loading capacity
diminishing. The results also confirmed that it was possible to trap 75mg of rhenium using 1g
of polymer. Doubling the template from 60mg to 120mg did not increase the loading capacity,
identifying that there was a limit to the maximum loading of the polymer, even with increased
concentration of template.

Keywords:Super alloy, CMSX-4, Aqua regia, Rhenium, Molecular imprinted polymers
Subjects:F Physical Sciences > F180 Analytical Chemistry
Divisions:College of Science > School of Life Sciences
ID Code:14740
Deposited On:20 Aug 2014 13:58

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