Application of Ion Exchange for Preparation of Selected Metal Perrhenates—Precursors for Superalloy Production

: Methods for the preparation of selected metal perrhenates and their mixtures are presented in this paper. These materials are suitable for reduction, and therefore for production of alloy powders containing rhenium and other superalloy components, i.e., Cr, Ni and Co. Prepared compounds may be also used as substrates for electrowinning of binary and ternary rhenium alloys. All developed methods are based on an ion exchange technique. This technique allows management of waste solutions, limitation of valuable metals losses, and, importantly, production of high-purity components. ionite after evaporation, puriﬁcation, and, proper


Introduction
Metals are basic materials for all technique branches. Currently, one of its most interesting application areas are superalloys [1][2][3]. These are alloys of various metals, usually iron-, nickel-and cobalt-based [3][4][5]. Superalloys possess unique physical and chemical properties, e.g., nickel-based superalloys are resistant to high temperature, dynamic loads and aggressive, corrosive environments. Therefore, they are mainly applied in aviation (engine turbines), rocket and space industries [3,6,7]. It is estimated that ca. 50% of nickel-based superalloys are used for construction of jet engine components. Further improvement of these materials should increase their operating temperature and reduce heat losses as well as improving their durability and reliability. Such improvement may be achieved by optimizing their chemical composition, which would enhance alloy's resistance to creep as well as mechanical and thermal fatigue [3]. The first monocrystalline nickel-based superalloys were prepared in the 1960s. However, their first industrial-scale production was launched in 1975 [1][2][3][4][5][6][7]. First-generation superalloys are highly thermal-fatigue-and creep-resistant materials. They are composed of nickel base and other elements, like chromium, cobalt, aluminum, titanium, molybdenum and tungsten. Second-generation superalloys also contain rhenium, which is added to improve material strength under elevated temperature. A small percentage of rhenium already significantly improves almost all technically-important properties of superalloys [6][7][8]. This is due to so called "rhenium effect", which is associated with the reduction of grain recrystallisation and inhibition of mean grain size increase. These unfavorable phenomena may increase alloy brittleness, especially during its ageing at high temperatures. Rhenium has a high tendency to form clusters, which inhibit the migration of other atoms and do not disturb alloy uniformity. In the next generations (3rd and 4th) of nickel-based superalloys, the rhenium content is reduced. However, this is due to economic aqueous HReO 4 , ionite washing after elution, neutralization, evaporation, purification, drying and, importantly, proper storage.
Developed methods allowed to prepare anhydrous forms of chromium(III), nickel(II) and cobalt(II) perrhenates and their mixtures.
The following indicators: sorption efficiency, elution efficiency, degree of ionite saturation were calculated for the performed tests. Sorption efficiency was calculated as a ratio of sorbed metal mass to mass of the metal in the initial solution multiplied by 100%. Elution efficiency was calculated as a ratio of metal mass in the solution before neutralization to metal mass sorbed in an ionite, multiplied by 100%. Degree of ionite saturation was calculated as a sorbed metal mass to ionite mass ratio, multiplied by 100%.

Preparation of Anhydrous Chromium(III) Perrhenate and Its Mixtures
Preparation of anhydrous chromium(III) perrhenate was performed using clear aqueous nitric solutions, containing 2-3 g/dm 3 Cr. Appropriate amounts of the solutions required to achieve over 2.5% degree of ionite saturation and 0.05 g/dm 3 chromium in the solution after sorption were used. The solutions were passed through a bed of PFC100X10 ionite in hydrogen form. The bed was placed inside a column and its height to diameter ratio was over 7.5. Tests were carried out using 1 kg portions of PFC100X10 ionite. Six working cycles of the ionite were performed. Sorption was carried out proceeding down the column, at room temperature, while contact time between solution and ionite bed was at the level of 5 dm 3 /h. After the sorption ionite was washed with water, downward from the column, at a flow rate between 2.5-10 dm 3 /h. Solutions generated after sorption and washing were acidic nitric effluent directed for utilization. Washed column with chromium-sorbed bed was subjected to elution. It was carried out using aqueous perrhenic acid solutions containing over 400 g/dm 3 rhenium. For each 1 g of sorbed chromium 30-40 g of rhenium were used, proceeding down the column, at a flow rate of 2.5 dm 3 /h. Solution generated after elution was collected in two portions. First portion, in the amount of about one bed volume was mixed with second portion of solutions from washing after elution and recycled to eluent preparation step. The second one was directed to neutralization. The ionite bed after the elution was washed with water. The solution generated in this step was also collected in two portions-the first one was mixed with the second portion of solution generated during elution and then neutralized, while the second one was mixed with the first portion of solution from elution step and directed to eluent preparation step. Solutions for neutralization from cycles I-III were joined and subsequently directed to neutralization step with freshly precipitated chromium(III) hydroxide and washed from ammonium ions to the level <0.1%. Whereas, solution generated in cycles IV-VI were combined and subsequently directed to neutralization with nickel(II) oxide. Both neutralizing agents were applied in stoichiometric amounts with respect to rhenium, which was present in excess. Irrespectively of the applied agent, neutralization was carried out below 80 • C, until solution pH reached ca. 6. Solution after neutralization was hot filtered from solid impurities. Concentration of solution after neutralization was also performed at temperature <80 • C, with vigorous mixing until dryness. Obtained solids were purified in two steps-firstly with water of ≤10 • C, using 10 cm 3 of H 2 O per each 1 g of the solid and, secondly, with anhydrous acetone at ≤10 • C using 2 cm 3 of acetone per each 1 g of the solid. The solids remaining after purification were dried at 160 • C, until constant mass and, then, stored in a glass vessel under argon [13]. The scheme of the applied Cr(ReO 4 ) 3 preparation method is presented in Figure 1.

Preparation of Anhydrous Cobalt(II) Perrhenate and its Mixtures
Preparation of anhydrous cobalt(II) perrhenate was performed using clear aqueous sulphate solutions, containing 5 g/dm 3 Co. Appropriate amounts of the solutions required to achieve over 5% degree of ionite saturation and 0.1 g/dm 3 chromium in the solution after sorption were used. The solutions were passed through a bed of SGC650 ionite in hydrogen form. The bed was placed inside a column which parameters were described in Section 2.3. Tests were carried out according to the methodology similar to chromium(III). The main difference was that sulphate solution generated after sorption was an acidic effluent for utilization, while solution from washing after sorption was recycled to sorption solution preparation step. Aqueous HReO4 solution, containing over 500 g/dm 3 rhenium, was used for elution. For each 1 g of sorbed cobalt 10-20 g of rhenium were used. Solution generated after elution was also collected in two portions. First portion (up to one bed volume) was directed for management using known methods, while the second one was neutralized. The solution generated during washing after elution was collected in two portions-the first one was combined with the second portion of solution from elution and neutralized, while the second one was mixed with washings from washing after sorption and directed to step of sorption solution preparation.
Solutions for neutralization from cycles I-II were joined and subsequently directed to neutralization step with metallic cobalt, solutions generated in cycles III-IV are combined and subsequently directed to neutralization with cobalt(II) oxide, whereas solutions generated during cycles V-VI were also combined and neutralized with nickel(II) oxide. Neutralization was carried out until solution pH was between 7-8. Solution after neutralization was hot filtered from solid impurities. Concentration of solution after neutralization was also performed at temperature <80 °C with vigorous mixing until dryness. Purification step was not applied. Obtained solid was dried at 130 °C [14]. The scheme of the applied Co(ReO4)2 preparation method is presented in Figure 2.

Preparation of Anhydrous Cobalt(II) Perrhenate and Its Mixtures
Preparation of anhydrous cobalt(II) perrhenate was performed using clear aqueous sulphate solutions, containing 5 g/dm 3 Co. Appropriate amounts of the solutions required to achieve over 5% degree of ionite saturation and 0.1 g/dm 3 chromium in the solution after sorption were used. The solutions were passed through a bed of SGC650 ionite in hydrogen form. The bed was placed inside a column which parameters were described in Section 2.3. Tests were carried out according to the methodology similar to chromium(III). The main difference was that sulphate solution generated after sorption was an acidic effluent for utilization, while solution from washing after sorption was recycled to sorption solution preparation step. Aqueous HReO 4 solution, containing over 500 g/dm 3 rhenium, was used for elution. For each 1 g of sorbed cobalt 10-20 g of rhenium were used. Solution generated after elution was also collected in two portions. First portion (up to one bed volume) was directed for management using known methods, while the second one was neutralized. The solution generated during washing after elution was collected in two portions-the first one was combined with the second portion of solution from elution and neutralized, while the second one was mixed with washings from washing after sorption and directed to step of sorption solution preparation.
Solutions for neutralization from cycles I-II were joined and subsequently directed to neutralization step with metallic cobalt, solutions generated in cycles III-IV are combined and subsequently directed to neutralization with cobalt(II) oxide, whereas solutions generated during cycles V-VI were also combined and neutralized with nickel(II) oxide. Neutralization was carried out until solution pH was between 7-8. Solution after neutralization was hot filtered from solid impurities. Concentration of solution after neutralization was also performed at temperature <80 • C with vigorous mixing until dryness. Purification step was not applied. Obtained solid was dried at 130 • C [14]. The scheme of the applied Co(ReO 4 ) 2 preparation method is presented in Figure 2.

Preparation of Anhydrous Nickel(II) Perrhenate and its Mixtures
Preparation of anhydrous nickel(II) perrhenate, the basics of which were described in the previous publications [15][16][17], was performed using clear aqueous nitrate solutions, containing 5 g/dm 3 Ni. Appropriate amounts of the solutions required to achieve over 6% degree of ionite saturation and 0.1 g/dm 3 chromium in the solution after sorption were used. The solutions were passed through a bed of C160 ionite in hydrogen form. The bed was placed inside a column which parameters were described in Section 2.3. Tests were carried out according to the similar methodology as for abovementioned perrhenates. Solution after sorption was recycled to the step of sorption solution preparation. After sorption ionite was washed with water in two steps, proceeding down the column, at a flow rate between 2.5-5.0 dm 3 /h. Combined solutions were recycled to step of sorption solution preparation. Washed column with nickel-sorbed bed was subjected to elution. It was carried out using aqueous solutions of perrhenic acid or solution obtained combining perrhenic acid with the first portion of the washings after elution. Total rhenium concentration in these solutions was over 500 g/dm 3 rhenium. Concentrated nitric acid in an amount of 20 cm 3 per each 1 dm 3 of eluent was added. For each 1 g of sorbed nickel, 20 g of rhenium were used. Solution generated after elution was also collected in two portions. The first one (up to 0.5 bed volume) was directed for management using known methods, while the second proper portion (up to 2 bed volumes) was neutralized. Eluted ionite bed was washed with water, whereas solution from washing after elution was collected in two portions-the first one was recycled to eluent preparation, while the second portion was directed to preparation of sorption solution. Solution for neutralization generated in cycles I-II were combined and subsequently neutralized with metallic nickel, solutions from cycles III-IV were joined and neutralized with nickel(II) oxide, whereas solutions from cycles V-VI were also combined and neutralized with metallic cobalt. All neutralizing agents were used in stoichiometric amounts with respect to rhenium, which was present in excess. Irrespective of the applied agent, neutralization was carried out below 80 °C, until solution pH reached 7-8. Solution after neutralization was hot filtered from solid impurities. Concentration of solution after neutralization was also performed at temperature <80 °C with vigorous mixing until dryness. Then, it was purified with 30% aqueous hydrogen peroxide solution using 2 cm 3 of the solution per each 1 g of the solid. Solids remaining after purification were dried at 160 °C, until constant mass and, then, stored in a

Preparation of Anhydrous Nickel(II) Perrhenate and Its Mixtures
Preparation of anhydrous nickel(II) perrhenate, the basics of which were described in the previous publications [15][16][17], was performed using clear aqueous nitrate solutions, containing 5 g/dm 3 Ni. Appropriate amounts of the solutions required to achieve over 6% degree of ionite saturation and 0.1 g/dm 3 chromium in the solution after sorption were used. The solutions were passed through a bed of C160 ionite in hydrogen form. The bed was placed inside a column which parameters were described in Section 2.3. Tests were carried out according to the similar methodology as for abovementioned perrhenates. Solution after sorption was recycled to the step of sorption solution preparation. After sorption ionite was washed with water in two steps, proceeding down the column, at a flow rate between 2.5-5.0 dm 3 /h. Combined solutions were recycled to step of sorption solution preparation. Washed column with nickel-sorbed bed was subjected to elution. It was carried out using aqueous solutions of perrhenic acid or solution obtained combining perrhenic acid with the first portion of the washings after elution. Total rhenium concentration in these solutions was over 500 g/dm 3 rhenium. Concentrated nitric acid in an amount of 20 cm 3 per each 1 dm 3 of eluent was added. For each 1 g of sorbed nickel, 20 g of rhenium were used. Solution generated after elution was also collected in two portions. The first one (up to 0.5 bed volume) was directed for management using known methods, while the second proper portion (up to 2 bed volumes) was neutralized. Eluted ionite bed was washed with water, whereas solution from washing after elution was collected in two portions-the first one was recycled to eluent preparation, while the second portion was directed to preparation of sorption solution. Solution for neutralization generated in cycles I-II were combined and subsequently neutralized with metallic nickel, solutions from cycles III-IV were joined and neutralized with nickel(II) oxide, whereas solutions from cycles V-VI were also combined and neutralized with metallic cobalt. All neutralizing agents were used in stoichiometric amounts with respect to rhenium, which was present in excess. Irrespective of the applied agent, neutralization was carried out below 80 • C, until solution pH reached 7-8. Solution after neutralization was hot filtered from solid impurities. Concentration of solution after neutralization was also performed at temperature <80 • C with vigorous mixing until dryness. Then, it was purified with 30% aqueous hydrogen peroxide solution using 2 cm 3 of the solution per each 1 g of the solid. Solids remaining after purification were dried at 160 • C, until constant mass and, then, stored in a glass vessel under argon [18]. The scheme of the applied Ni(ReO 4 ) 3 preparation method is presented in Figure 3.
glass vessel under argon [18]. The scheme of the applied Ni(ReO4)3 preparation method is presented in Figure 3.

Analytical Methods
All the necessary analysis was performed by IMN Department of Analytical Chemistry. Content of rhenium, chromium, nickel and cobaltium in products was analyzed using a weight method with tetraphenylarsonium chloride (TPAC) as a precipitating agent, and flame atomic emission spectroscopy (FAES, spectrophotometer AAS novAA400, Analytik, Jena, Germany), respectively. Solutions were analyzed by flame atomic absorption spectroscopy (FAAS, SOLAAR S4, ThermoWaltham, MA, USA) equipped with flame module and deuterium background correction, to establish Re, Co, Ni and Cr content. Analysis of contaminations was performed using various techniques: inductively coupled plasma mass spectrometry (ICP-MS, ICP MS NexION, PerkinElmer, Waltham, MA, USA), inductively coupled plasma-optical emission spectrometer (ICP-OES, ULTIMA 2, Horiba Jobin-Ivon, Kyoto, Japan), graphite furnace atomic absorption spectroscopy (GFAAS, Z-2000, Hitachi, Tokyo, Japan) with graphite cells.

Preparation of Anhydrous Chromium(III) Perrhenate and its Mixtures
Six cycles of chromium(III) perrhenate preparation under dynamic conditions were performed. Balance sheets of conducted trials are shown in Tables 1-6. Changes of sorption and elution efficiency in subsequent cycles of ionite work are presented in Figure 4.

Analytical Methods
All the necessary analysis was performed by IMN Department of Analytical Chemistry. Content of rhenium, chromium, nickel and cobaltium in products was analyzed using a weight method with tetraphenylarsonium chloride (TPAC) as a precipitating agent, and flame atomic emission spectroscopy (FAES, spectrophotometer AAS novAA400, Analytik, Jena, Germany), respectively. Solutions were analyzed by flame atomic absorption spectroscopy (FAAS, SOLAAR S4, ThermoWaltham, MA, USA) equipped with flame module and deuterium background correction, to establish Re, Co, Ni and Cr content. Analysis of contaminations was performed using various techniques: inductively coupled plasma mass spectrometry (ICP-MS, ICP MS NexION, PerkinElmer, Waltham, MA, USA), inductively coupled plasma-optical emission spectrometer (ICP-OES, ULTIMA 2, Horiba Jobin-Ivon, Kyoto, Japan), graphite furnace atomic absorption spectroscopy (GFAAS, Z-2000, Hitachi, Tokyo, Japan) with graphite cells.

Preparation of Anhydrous Chromium(III) Perrhenate and Its Mixtures
Six cycles of chromium(III) perrhenate preparation under dynamic conditions were performed. Balance sheets of conducted trials are shown in Tables 1-6. Changes of sorption and elution efficiency in subsequent cycles of ionite work are presented in Figure 4.      Sorption and elution efficiencies of Cr(III) ions in six subsequent working cycles of PFC100 × 10 ionite were stable and very high. Sorption efficiency was 99.69-99.87%, while elution efficiency was 98.31-99.84%. High stability of sorption and elution efficiencies was also observed when the initial amount of chromium for sorption was increased in cycles IV-VI. Degree of ionite saturation with chromium ions in cycles I-III was ca. 3%, whereas in cycles IV-VI it was over 4%. Concentration of chromium in the solution generated during 2nd part of elution, directed to neutralization, was high enough to isolate a final product, i.e., chromium(III) perrhenate. In the first three cycles it was 8.71-11.10 g/dm 3 , while in the next three-14.40-14.60 g/dm 3 . The proper course of the sorption and elution processes and low metal (Re and Cr) losses (<1%) were the result of adequate recycling of generated solutions. The important part of the proposed technology is minimizing amount of generated waste solutions, containing valuable metals.
Obtained solution were combined, neutralized and appropriate compounds (chromium(III) perrhenate and its mixture with nickel) were separated. Composition of the prepared substances after purification and drying is shown in Table 7. The proposed procedure allowed to obtain high purity substances fulfilling the requirements for their application in alloy powder production or as components of baths for alloy electrowinning.

Preparation of Anhydrous Cobalt(II) Perrhenate and its Mixtures
Six cycles of cobalt(II) perrhenate preparation, under dynamic conditions using sulphate solutions were performed. Balance sheets of conducted trials are shown in Tables 8-13. Changes of sorption and elution efficiency in subsequent cycles of ionite work are presented in Figure 5. Sorption and elution efficiencies of Cr(III) ions in six subsequent working cycles of PFC100 × 10 ionite were stable and very high. Sorption efficiency was 99.69-99.87%, while elution efficiency was 98.31-99.84%. High stability of sorption and elution efficiencies was also observed when the initial amount of chromium for sorption was increased in cycles IV-VI. Degree of ionite saturation with chromium ions in cycles I-III was ca. 3%, whereas in cycles IV-VI it was over 4%. Concentration of chromium in the solution generated during 2nd part of elution, directed to neutralization, was high enough to isolate a final product, i.e., chromium(III) perrhenate. In the first three cycles it was 8.71-11.10 g/dm 3 , while in the next three-14.40-14.60 g/dm 3 . The proper course of the sorption and elution processes and low metal (Re and Cr) losses (<1%) were the result of adequate recycling of generated solutions. The important part of the proposed technology is minimizing amount of generated waste solutions, containing valuable metals.
Obtained solution were combined, neutralized and appropriate compounds (chromium(III) perrhenate and its mixture with nickel) were separated. Composition of the prepared substances after purification and drying is shown in Table 7. The proposed procedure allowed to obtain high purity substances fulfilling the requirements for their application in alloy powder production or as components of baths for alloy electrowinning.

Preparation of Anhydrous Cobalt(II) Perrhenate and Its Mixtures
Six cycles of cobalt(II) perrhenate preparation, under dynamic conditions using sulphate solutions were performed. Balance sheets of conducted trials are shown in Tables 8-13. Changes of sorption and elution efficiency in subsequent cycles of ionite work are presented in Figure 5.      Sorption and elution efficiencies of cobalt(II) ions in six subsequent working cycles of SGC650 ionite were stable and very high. Sorption efficiency was 99.57-99.95%, while elution efficiency was 97.79-99.89%. Degree of ionite saturation with chromium ions was ca. 6%. Concentration of chromium in the solution generated during 2 nd part of elution, directed to neutralization, was high and between 24.2-26.4 g/dm 3 . The proper course of the sorption and elution processes and low metal (Re and Co) losses (<1%) were the result of adequate recycling of generated solutions. The important part of the proposed technology is a minimized amount of generated waste solutions, containing valuable rhenium and cobalt.
Obtained solutions were combined, neutralized and appropriate compounds (cobalt(II) perrhenate and its mixture with nickel) were separated. Compositions of the prepared substances after drying are shown in Table 14. As previously shown in this case, the proposed procedure also allowed us to obtain high purity substances that fulfilled the requirements. It should be pointed out that metallic cobalt is a more active neutralizing agent than cobalt(II) oxide. Moreover, the product of neutralization with metallic nickel is a purer substance than the product obtained using cobalt(II) oxide.

Preparation of Anhydrous Nickel(II) Perrhenate and its Mixtures
Six cycles of nickel(II) perrhenate preparation, under dynamic conditions using nitrate solutions were performed. Balance sheets of conducted trials are shown in Tables 15-20. Change of sorption and elution efficiencies in subsequent cycles of ionite work are presented in Figure 6. Sorption and elution efficiencies of cobalt(II) ions in six subsequent working cycles of SGC650 ionite were stable and very high. Sorption efficiency was 99.57-99.95%, while elution efficiency was 97.79-99.89%. Degree of ionite saturation with chromium ions was ca. 6%. Concentration of chromium in the solution generated during 2 nd part of elution, directed to neutralization, was high and between 24.2-26.4 g/dm 3 . The proper course of the sorption and elution processes and low metal (Re and Co) losses (<1%) were the result of adequate recycling of generated solutions. The important part of the proposed technology is a minimized amount of generated waste solutions, containing valuable rhenium and cobalt.
Obtained solutions were combined, neutralized and appropriate compounds (cobalt(II) perrhenate and its mixture with nickel) were separated. Compositions of the prepared substances after drying are shown in Table 14. As previously shown in this case, the proposed procedure also allowed us to obtain high purity substances that fulfilled the requirements. It should be pointed out that metallic cobalt is a more active neutralizing agent than cobalt(II) oxide. Moreover, the product of neutralization with metallic nickel is a purer substance than the product obtained using cobalt(II) oxide.

Preparation of Anhydrous Nickel(II) Perrhenate and Its Mixtures
Six cycles of nickel(II) perrhenate preparation, under dynamic conditions using nitrate solutions were performed. Balance sheets of conducted trials are shown in Tables 15-20. Change of sorption and elution efficiencies in subsequent cycles of ionite work are presented in Figure 6.
As in the case of cobalt and chromium, sorption and elution efficiencies of nickel(II) ions in six subsequent working cycles of C160 ionite were stable and very high. Sorption efficiency was 99.67-99.93%, while elution efficiency was 97.48-99.99%. The degree of ionite saturation with chromium ions was high and equal to ca. 7%. Concentration of chromium in a solution generated during 2 nd part of elution, directed to neutralization, was high and between 24-32 g/dm 3 .      During investigation of ion-exchange processes, it is important to perform several sorption-elution cycles to determine resin stability. Working parameters of ionite may be also established based on multiple repetitions of the cycles. The results of the first cycle are always subjected to significant errors. The reason for this is that new resin does not achieve equilibrium state during this cycle.
For all presented rhenium compounds, including nickel perrhenate, it is assumed that the degree of ionite saturation with metals should be >1%, whereas elution efficiency should be >90%. Therefore, determined efficiencies at the level 96-99% are considered to be very high. As in the case of cobalt and chromium, sorption and elution efficiencies of nickel(II) ions in six subsequent working cycles of C160 ionite were stable and very high. Sorption efficiency was 99.67-99.93%, while elution efficiency was 97.48-99.99%. The degree of ionite saturation with chromium ions was high and equal to ca. 7%. Concentration of chromium in a solution generated during 2 nd part of elution, directed to neutralization, was high and between 24-32 g/dm 3 .
During investigation of ion-exchange processes, it is important to perform several sorptionelution cycles to determine resin stability. Working parameters of ionite may be also established based on multiple repetitions of the cycles. The results of the first cycle are always subjected to significant errors. The reason for this is that new resin does not achieve equilibrium state during this cycle. For all presented rhenium compounds, including nickel perrhenate, it is assumed that the degree of ionite saturation with metals should be >1%, whereas elution efficiency should be >90%. Therefore, determined efficiencies at the level 96-99% are considered to be very high.
Obtained solutions were combined, neutralized and appropriate compounds (nickel(II) perrhenate and its mixture with cobalt) were separated. Compositions of the prepared substances after drying are shown in Table 21. In this case the proposed procedure is also allowed to obtain high purity substances fulfilling the requirements for their application in alloy powder production or for electrowinning of Re-Ni alloy.

Conclusions
An effective and highly efficient production method of high purity perrhenates of nickel(II), cobalt(II) and chromium(III) as well as their mixtures using ion exchange technique was applied. All developed technologies are characterized by management of waste solutions and low metal loss not exceeding 1%. Obtained products containing rhenium, cobalt, nickel and chromium, are components Obtained solutions were combined, neutralized and appropriate compounds (nickel(II) perrhenate and its mixture with cobalt) were separated. Compositions of the prepared substances after drying are shown in Table 21. In this case the proposed procedure is also allowed to obtain high purity substances fulfilling the requirements for their application in alloy powder production or for electrowinning of Re-Ni alloy.

Conclusions
An effective and highly efficient production method of high purity perrhenates of nickel(II), cobalt(II) and chromium(III) as well as their mixtures using ion exchange technique was applied. All developed technologies are characterized by management of waste solutions and low metal loss not exceeding 1%. Obtained products containing rhenium, cobalt, nickel and chromium, are components suitable for preparation of alloy powder precursors or baths for electrowinning of binary or ternary alloys.