Recycling of rhenium-containing wire scrap

Rhenium is a refractory metal and is one of the rarest elements. Due to its high cost, recycling of rhenium-containing scraps is of economic interest. This paper pertains to the recycling of rhenium from tungsten-rhenium wire scrap generated in the manufacturing of W97Re3 wire. Rhenium from wire scrap, which contained 3.1-3.4% Re, was volatilized at 900 °C in the presence of air at 2 L/min in a tube furnace according to the following equation: 4Re + 7O2 → 2Re2O7 (g). Volatilized Re was solidified on the inner surface of the tube and was recovered as ammonium perrhenate (NH4ReO4) solution after washing the tube with dilute ammonium hydroxide solution (Re2O7 + 2NH4OH → 2NH4ReO4 + H2O). Ammonium perrhenate solution was crystallized to obtain ammonium perrhenate crystals which were free of tungsten and other metal impurities. First pass yield of rhenium recovery was 65.1%. Ammonium perrhenate crystals were reduced in hydrogen at 400-700 °C to obtain Re-metal powder: (2NH4ReO4 + 7H2 = 2Re + 8H2O + 2NH3). Rhenium metal powder obtained from the W-Re wire scrap was blended with non-sag tungsten powder to make a 6 kg W97Re3-alloy ingot which was rolled to make tungsten-rhenium wire. Results presented in this paper were intended for developing a commercial process for the recycling of a large inventory of W-Re wire scrap.