Recycling of rhenium-containing wire scrap

Abstract 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 W 97 Re 3 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 + 7O 2 → 2Re 2 O 7 (g). Volatilized Re was solidified on the inner surface of the tube and was recovered as ammonium perrhenate (NH 4 ReO 4 ) solution after washing the tube with dilute ammonium hydroxide solution (Re 2 O 7 + 2NH 4 OH → 2NH 4 ReO 4 + H 2 O). 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: (2NH 4 ReO 4 + 7H 2 = 2Re + 8H 2 O + 2NH 3) . Rhenium metal powder obtained from the W–Re wire scrap was blended with non-sag tungsten powder to make a 6 kg W 97 Re 3 -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.