Open Chem., 2018; 16: 1298–1306 Research Article Open Access J. Gonzalez-Rodriguez*, Katherine Pepper, M.G. Baron, S.K. Mamo, A.M. Simons Production and Analysis of Recycled Ammonium Perrhenate from CMSX-4 superalloys https://doi.org/10.1515/chem-2018-0136 received June 6, 2018; accepted October 9, 2018. Abstract: The process to extract rhenium from a superalloy is an immense technical challenge due the complex chemistry involved. Being one of the rarest elements in the earth’s crust the scarcity and cost of rhenium makes it advantageous to recover the element from scrap superalloy. In this research the separation and monitoring of the different stages of the recycling process to extract rhenium from CMSX-4 superalloys using a distillation process were performed. This novel method combining distillation and use of exchange resins was used to separate rhenium from a complex mixture of metals in the CMSX-4 superalloy. The identification and quantitation of perrhenate and contaminants were performed by atomic absorption spectroscopy (AAS), Fourier transform infra- red spectroscopy (FTIR), ion chromatography (IC) and Scanning Electron Microscopy- Energy Dispersive X-Ray (SEM-EDX). Perrhenate ions were extracted with purity close to 93%. The analytical characteristics for a novel infrared method to quickly identify perrhenate anions from CMSX-4 are presented. The main characteristics of the analytical validation were: LoD: 0.5% w/w; LoQ: 1.5% w/w; linear range 1.5-100% w/w; correlation coefficient R 2 = 0.9905; precision (%RSD) for 10%w/w = 6.6 and 75%w/w = 4.1, respectively; accuracy (%) for 10% w/w 99.6% and 75% w/w=101.1, respectively. Keywords: Rhenium; CMSX-4; superalloys; metal recycling; metal separation. 1 Introduction A super alloy, being a unique high temperature and high performance alloy, displays excellent resistance to mechanical and chemical degradation close to their melting points [1]. In addition, super alloys demonstrate increased mechanical strength, creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Furthermore, as they maintain their properties at elevated temperatures (above 540 ̊C), super alloys can be employed in the hottest sections of turbines [2]. As a consequence of technological advances in super alloys, manufacturing costs have increased. Moreover, super alloys require the use of rare and expensive elements, such as rhenium or ruthenium. The alloying elements and heat-treatments also often make superalloys difficult to machine and weld, increasing fabrication costs, part reject rates, and reworks [3]. Rhenium is one of the rarest and most valuable elements in nature, and can only be found distributed on the earth’s surface in very small quantities, on the order of 10 -9 % [4]. Moreover, it occurs in a scattered form, and methods for its separation – in the form of metal or compounds – are complicated and costly. These factors result in a high price for rhenium and its compounds. Rhenium can be found in copper sulphide ores, but predominantly it can be obtained through molybdenum refinement. After its isolation, rhenium is traded commercially as sodium and ammonium perrhenates. In addition to its use in super alloys, specific properties of rhenium also make it useful for other selective applications, including catalysis and radiology and applications in the nuclear industry. Rhenium has a range of very desirable mechanical properties that makes it a valuable alloying element. This element has an extremely high density of 21.04 g/cm 3 , a melting point of 3180°C and a boiling point of 5630°C [5]. Another useful mechanical property is its high ductility, and it does not exhibit a ductile/brittle transition, so it remains ductile up to its melting point. It also presents high strength at elevated temperatures together with a high modulus of elasticity. Rhenium has excellent creep *Corresponding author: J. Gonzalez-Rodriguez, School of Chemistry, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, LN67DL, United Kingdom, E-mail: jgonzalezrodriguez@lincoln.ac.uk Katherine Pepper: Praxair Surface Technologies Ltd, Whisby Road, N. Hykeham, Lincoln LN6 3DL, United Kingdom M.G. Baron, S.K. Mamo, A.M. Simons: School of Chemistry, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, LN67DL, United Kingdom Open Access. © 2018 J. Gonzalez-Rodriguez et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.