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

摘要

Aqua regia, which is an acid solution of hydrochloric acid and nitric acid, was used at threeuddifferent strengths, over a period of seven days, to see how effective it was at dissolving theudindividual metals that are used in the super alloy CMSX-4. Tantalum, Hafnium and Titaniumudcould all withstand the corrosive effects and did not dissolve. The strongest strength of aquaudregia (not diluted) managed to partially dissolve the other metals, with Molybdenum beingudfully dissolved. The two diluted solutions of aqua regia were not as affective, howeverudrhenium managed to be fully dissolvedudSuper alloys, which are used in industries such as the aviation and energy sectors, are audcombination of specific metals which exhibit special characteristics. When the metals areudalloyed together, they produce an alloy that can withstand extreme temperatures (overud+1000°C) and workloads over an extended period of time, without the integrity of the alloyudbeing affected. As technologies change different generations of super alloys have beenuddeveloped. A second generation super alloy, CMSX-4, contains 3% rhenium and rheniumudbeing an extremely rare element, is an expensive metal to use (around £2500 per kg).udMolecular imprinted polymers are a new separation technique that has become increasinglyudpopular due to their benefits of, ease of creation; low cost and extremely specific separationudabilities. The specific separation is achieved during the polymerisation process, by using audtemplate, identical in chemical and structure to the analyte of interest, allowing forudseparation of the analyte of interest, even in the presence of similar structural and chemicaludcompounds.udFive molecular imprinted polymers were made, each with different concentrations of rheniumudtemplate. They were tested to not only see if they could successfully trap rhenium, but to alsoudinvestigate if the maximum loading of the molecular imprinted polymer would increase as theudconcentration of the template increased. Throughout the research, the molecular imprintedudpolymers were analysed by X-Ray fluorescence to determine the presence of trappedudrhenium. The solutions that were eluted through the polymers were analysed by AtomicudAbsorption Spectroscopy to identify how much rhenium was not being trapped by theudmolecular imprinted polymer during the analyte loading stage and how much rhenium wasudbeing removed during the analyte removal stage.udThe research also investigated to see if a re-useable polymer was produced. The resultsudindicated that not only could the molecular imprinted polymer trap rhenium; it could also beudremoved and then re-used again at least four times, without the maximum loading capacityuddiminishing. The results also confirmed that it was possible to trap 75mg of rhenium using 1gudof polymer. Doubling the template from 60mg to 120mg did not increase the loading capacity,udidentifying that there was a limit to the maximum loading of the polymer, even with increasedudconcentration of template.