Electrochemical recovery of rhenium from W–Re alloys in the form of perrhenic acid: I. Fundamentals of the process

Review: Rhenium and its smelting and recycling technologies

“…For example, by adding HCl or hexamine (C 6 H 12 N 4 ) to an aqueous solution containing Re and W, tungstic acid (H 2 WO 4 , H 4 WO 5 ) and hexamine-tungsten compounds are formed that are separated from the Re in the solution. 187,269,270 The addition of CaO or Ca(OH) 2 to a NH 4 OH or NaOH solution containing Re, W, and Mo results in the conversion of Mo and W in the aqueous solution to CaMoO 4 and CaWO 4 precipitates, respectively 170,196 (cf. Figure 19,24).…”

“…When the obtained KPR is dissolved again in water and purified by solvent extraction or ion exchange, high-purity APR can be crystallized and separated. Levin et al used KPR as a raw material to produce a high-purity aqueous HReO 4 solution by electrolysis of KPR in a cell where the cathode, sample, and anode chambers were partitioned by using ion exchange membranes 196 (Figure 24). In the past, high-purity APR was prepared after converting the crude Re metal obtained from KPR to Re 2 O 7 ( g ) or ReCl 5 ( g ) by roasting or high-temperature chlorination and subsequent purification, and the APR was used to produce ultrahigh-purity Re metal.…”

“…Flowchart of Re recovery from W-Re alloy scraps by electrochemical dissolution. 196 Palant et al conducted the electrolysis of a Ni-based superalloy by using alternating current in a H 2 SO 4 bath and HNO 3 bath, respectively. 170,171 Figure 19 shows the process flowchart of the electrochemical oxidation of superalloys in a H 2 SO 4 electrolysis bath.…”

“…In the electrochemical oxidation of the W–Re scrap, which is used as an electrode in aqueous NaOH solution, both Re and W dissolve in the solution. 194–196 Levin et al demonstrated that W can be precipitated from aqueous NaOH solution by adding Ca(OH) 2 ( s ), and Re can be recovered as KPR or HReO 4 (Figure 24). 196–198…”

“…194–196 Levin et al demonstrated that W can be precipitated from aqueous NaOH solution by adding Ca(OH) 2 ( s ), and Re can be recovered as KPR or HReO 4 (Figure 24). 196–198…”