Batista, Maria Joao

Figueiredo, M. Ondina

Oliveira, Daniel P. S.

Silva, Teresa

Veiga, JP

de Oliveira, Daniel Pipa Soares

Repositório do LNEG

X-ray absorption spectroscopy at Re L3-edge applied to mine waste materials:  a possible input to the sustainable recovery of rhenium  Maria-Ondina Figueiredo 1,2 (*) , Teresa Pereira da Silva 2 , João Pedro Veiga 1,  Daniel de Oliveira2 and Maria-João Batista2  1 CENIMAT / I3N, Materials Sci. Dept., Fac. Sci. Technol., New Univ. Lisbon, 2829-516 Caparica, Portugal 2 LNEG (Nat. Lab. Energy & Geol.), UI RU Min. Resources & Geophysics, Apartado 7586, 2610-999 Amadora, Portugal  (*) E-mail:  ondina.figueiredo@lneg.pt  Scientific Research Area:  CHEMISTRY  Keywords:  Re L3-edge;  XANES;  Re oxides;  molybdenite;  mine waste materials.  Rhenium belongs to 7th column of the Periodic Table along with a widespread element (manganese) and a non-naturally occurring one (technetium). It is a valuable but very scarce metal with very high melting point appearing in Nature mainly carried by molybdenite (MoS2) through a diadochic replacement of molybdenum and it was for long assumed to be related with the volatile transport and deposition of the refractory metals Mo and W in high temperature magmatic fluids [1]. However, while molybdenum and rhenium are typical chalcophile elements, tungsten oxidizes quite easily and very seldom occurs as a sulphide (WS2, tungstenite). The formal valence of Re ranges from -1 to +7 and the prevalence of this exceptionally high oxidation state has rendered rhenium technologically relevant for the production of catalysts [2].  Due to these unique properties, actual applications of rhenium cover distinctive areas ranging from the nuclear field to the electrical and aero-spatial industries, particularly for the production of superalloys applied in jet engines. Because of its very low availability (1 ppb average concentration in the Earth´s crust) comparative to the actual industrial demand, rhenium is nowadays one of the most expensive industrial commodities. It is mainly recovered as a by-product in the refinement of molybdenum concentrates from porphyry copper deposits because the flue dusts obtained from these metal concentrates are enriched in Re as a result of the high volatility of the molecular oxide Re2O7 [3]. Notably rare as a distinct mineral species, the first Re-mineral (rheniite, ReS2) was identified twenty years ago [4] as a condensate in the fumaroles of Kudriavy volcano, Kurila Islands, and more recently assigned in the Pagoni Rachi Mo-Cu prospect in northern Greece [5]. In view of the actual interest in exploring exhausted mine residues from the exploitation of sulphide ore deposits in Europe#, it is clear that finding about 3 ppm of Re in waste materials sampled close to the old sulphur factory from São Domingos abandoned mine [6] deserves a  particular attention, specially because no reference is known to a significant occurrence of molybdenite in association with the volcanic-hosted massive sulphide deposits from the Iberian Pyrite Belt, SW Iberian peninsula. Taking profitProfiting from an experiment focused on studying the binding state of rhenium in molybdenite*, a first X-ray absorption near-edge spectroscopy (XANES) study at Re L3-edge was carried out at the ESRF; along with a sample of São Domingos mine wastes, model compounds displaying various Re formal valences and coordinations - ReO3, Re2O7, KReO4 - were studied [7]. These preliminary results clearly showed that rhenium is bound to oxygen in the mine waste sample - a relevant conclusion within the frame of a future prospect on a sustainable Re-recovery; however, further work is needed with the aim of ascertaining the original Re-carrier mineral phase.       References [1] A. Bernard, R.B. Symons, W.I. Rose (1990) Appl. Geochem. 5, 317. [2] S.R. Bare et al. (2011) J. Phys. Chem. 115, 5740. [3] B. Krebs, H. Müller, H. Beyer (1968) Chem. Comm. 5, 263. [4] M.A. Korzhinskiy et al. (1994) Nature 369, 51. [5] P.C. Voudouris et al. (2009) Canad. Miner. 47, 1013. [6] M.J. Batista et al. (2011) VIII Iberian Congr. Geochem., Castelo Branco/Portugal, September 24-28. Abstract. [7] M.O. Figueiredo et al. (2012) 9th ISEG, Int. Symp. Environ. Geochem., Aveiro/Portugal, July 15-22, Poster T2-198. #  Project ProMine (FP7-NMP-2008-LARGE-2, 228559, Nanoparticle products from new mineral resources in Europe) * Experiment CH-3421 at beamline BM23, September 2011. 

X-ray absorption spectroscopy at Re L3-edge applied to mine waste materials : a possible input to the sustainable recovery of rhenium

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