A method for reworking unqualified rhodium products

Abstract

The invention relates to a reprocessing method for unqualified rhodium products. Unqualified rhodium powder and sodium chloride are mixed in a certain proportion and then put into a quartz boat. Chlorine gas is introduced into the mixture after heating in a closed tube furnace. After keeping the temperature for a period of time, the mixture is taken out and cooled. Hydrochloric acid is added to leach and filter to obtain a sodium chlororhodate solution. Sodium hydroxide is added to the sodium chlororhodate solution for hydrolysis to obtain a hydrolysis residue of rhodium. The residue is dissolved with a small amount of hydrochloric acid and then driven out of the acid. A small amount of sodium hydroxide solution is added to control the pH value to perform resin exchange to remove base metals. After the base metals are removed, the residue is hydrolyzed again, and the hydrolysis residue is dissolved with hydrochloric acid to obtain a chlororhodate acid solution for the next step of electrolysis. The electrolysis method is used to further separate rhodium from base metals, and the noble metal impurity elements exceeding the standard in the rhodium powder can be removed, so as to finally obtain rhodium powder with a purity greater than 99.99%.

Description

Technical Field

[0001] The invention relates to a reworking process for unqualified rhodium products and relates to the technical field of metallurgical processes. Background Art

[0002] As a platinum group metal, rhodium metal has an extremely low content in the earth's crust and is widely used in the military, pharmaceutical and catalyst industries. It is mainly used in the manufacture of platinum-rhodium alloys, platinum-rhodium thermocouples, automobile exhaust three-way catalysts, chemical catalysts, artificial fiber nozzles and various electroplating compounds.

[0003] The efficiency of nickel removal reagents used in the separation and refining of rhodium is low. The control of valence state in the extraction and separation of platinum and rhodium and rhodium and iridium during TBP extraction has always been a difficult point. The separation of rhodium and iridium requires a high degree of refined operation. A slight deviation in reagents or control parameters can lead to poor separation of platinum and rhodium, rhodium and iridium, resulting in the final rhodium product containing nickel, iridium and platinum, which cannot meet the national standard of purity greater than 99.9%. In order to solve the above problems, a purification process needs to be developed for the impurity elements exceeding the standard in the above unqualified rhodium powder. Summary of the invention

[0004] In order to solve the problem of excessive impurity elements in unqualified rhodium powder, the present invention has invented a reprocessing process for unqualified rhodium products by studying the physicochemical properties of the impurity elements and the electrochemical reaction process, and successfully produced high-purity rhodium with a grade greater than 99.99%.

[0005] The technical solution of the present invention is as follows:

[0006] 1) Medium-temperature chlorination: mix rhodium powder and sodium chloride in a mass ratio of 1:1-1:4 and load them into a quartz boat, then put the quartz boat into a quartz tube furnace, connect the chlorine inlet and outlet pipes, heat to 650-750°C for chlorination for 4-5 hours, dissolve the chlorinated product with 1-2 mol / L HCl, and the insoluble matter enters the next medium-temperature chlorination cycle; the chlorinated product is mainly sodium chlororhodate.

[0007] 2) primary hydrolysis, adding a 35% to 45% NaOH solution to the hydrochloric acid solution obtained in step 1) to start hydrolysis, adjusting the pH value of the solution to 8 to 9, standing for 0.5 to 1 hour after the pH value stabilizes, cooling and filtering to obtain a hydrolysis residue and a hydrolysis liquid; washing the hydrolysis residue with deionized water for 2 to 3 times, and adding the washing water to the hydrolysis liquid for external use;

[0008] 3) Acid dissolution and pH adjustment: the hydrolysis residue obtained in step 2) is dissolved with 2-5 mol / L hydrochloric acid, the pH value of the rhodium-containing solution is measured after the acid is driven out, and the pH value of the rhodium-containing solution is controlled to 1-1.5 by using a NaOH solution with a mass fraction of 15%-25%;

[0009] 4) Cation resin exchange, add strong acid cation resin to the rhodium-containing solution with a pH value of 1-1.5 obtained in step 3), mix and stir for 5-10 minutes, let stand for 0.5-1 hour and filter; the strong acid cation exchange resin is 732 type cation exchange resin. The 732 type cation exchange resin is pretreated before use, and the pretreatment method is: soak with 10-12 mol / L HCl for 72 hours, wash with water to neutrality and then regenerate with pH=1.5 HCl solution. After use, check that there is no precious metal, wash the resin with 6 mol / L HCl until it is colorless, and then regenerate the resin with pH=1.5 HCl.

[0010] 5) Secondary hydrolysis: add 15%-25% NaOH solution to the filtrate obtained in step 4) to adjust the pH to 12, pass chlorine gas to reduce the pH to 8-9, repeat twice, filter and wash to obtain hydrolysis residue and hydrolysis liquid; dissolve the hydrolysis residue in 2-5 mol / L hydrochloric acid for later use, and add the washing water to the hydrolysis liquid for external use;

[0011] 6) Electrolysis, the hydrochloric acid solution obtained in step 5) is placed in the cathode chamber, the ammonium chloride solution or the sodium chloride solution is placed in the anode chamber, the cathode chamber and the anode chamber are separated by a cation exchange membrane, and the electrolysis temperature is controlled at 50-95°C and the voltage is 0.2-1.5V during electrolysis to ensure that the rhodium concentration is ≮20g / L and the copper ion concentration is ≯0.5g / L during the electrolysis process. The rhodium ion concentration in the hydrochloric acid solution is 5g / L-20g / L, and the acidity is 2-10mol / L.

[0012] Reaction mechanism of the present invention:

[0013] Medium temperature chlorination: 2Rh+NaCl+3Cl2 heating 2Na3RhCl6

[0014] Primary hydrolysis: H3[RhCl6]+6NaOH=Rh(OH)3↓+6NaCl+3H2O

[0015] H3[IrCl6]+6NaOH=Ir(OH)3↓+6NaCl+3H2O

[0016] PtCl4+4NaOH=Pt(OH)4+4NaCl

[0017] H2[PtCl6]+4H2O=Pt(OH)4+6HCl

[0018] Pt(OH)4+2NaOH=Na2[Pt(OH)6]

[0019] The platinum remains in the liquid and no precipitation occurs.

[0020] Cation Resin Exchange: Copper, nickel and hydrogen ions are exchanged and removed.

[0021] Secondary hydrolysis: H3[RhCl6]+6NaOH=Rh(OH)3↓+6NaCl+3H2O

[0022] H3[IrCl6]+6NaOH=Ir(OH)3↓+6NaCl+3H2O

[0023] electrolysis:

[0024] Anode: Rh 3+ +3e==Rh

[0025] Cathode: 2Cl - -2e==Cl2

[0026] By controlling the electrolysis temperature and reduction potential, rhodium can be reduced and precipitated, while iridium remains in the electrolyte.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention uses electrolysis to separate impurity elements in refined rhodium powder, with the advantages of simple equipment, easy operation, short process flow, strong adaptability, low production cost, etc., and strong industrial applicability;

[0029] 2. The current efficiency is greater than 80%. Excluding the electrolyte tank, the rhodium recovery rate is greater than 99%, which can be used for rhodium enriched materials containing various impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a process flow chart of the method of the present invention,

[0031] Figure 2 A structural diagram of the electrolysis device used in the method of the present invention.

[0032] In the figure, 1-power supply, 2-cathode titanium plate, 3-cation exchange membrane, 4-cathode chamber, 5-anode chamber, 6-anode millstone. DETAILED DESCRIPTION

[0033] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] (1) Unqualified rhodium powder (rhodium grade 96.4%) and sodium chloride were mixed in a mass ratio of 1:2, loaded into a quartz boat, placed in a quartz tube furnace, connected to chlorine gas entering the quartz tube, heated to 700°C for chlorination for 4 hours, and rhodium formed soluble sodium chlororhodate, which was dissolved in 2 mol / L HCl. The undissolved alloy rhodium powder entered the next medium-temperature chlorination cycle.

[0036] (2) Add 40% sodium hydroxide solution to the hydrochloric acid solution to start hydrolysis and adjust the solution pH to 8.5. After the pH value stabilizes for 0.5h, cool and filter, and wash the hydrolysis residue twice with deionized water. Dissolve the rhodium hydrolysis residue with 4mol / L hydrochloric acid, remove the acid, add water and measure the pH value. Control the sodium chlororhodate solution at pH=1.5 by adding 20% ​​liquid alkali.

[0037] (3) After pretreatment, the 732 cation exchange resin at pH = 1.5 was mixed with the rhodium-containing solution at pH = 1.5 and stirred for 5 minutes, allowed to stand for 40 minutes and filtered; the resin was washed with HCl at pH = 1.5 until there was no precious metal.

[0038] (4) After the base metals are removed, add 20% NaOH solution to adjust the pH to 13, pass chlorine gas to reduce the pH to 8, repeat twice, filter and wash. Dissolve the hydrolysis residue with 4 mol / L HCl for later use.

[0039] (5) Add 17% ammonium chloride solution to the anode chamber, add the above hydrochloric acid solution (chlororhodium acid concentrate) to the cathode chamber, and continue to add 10 mol / L hydrochloric acid to control the rhodium ion concentration at 15 g / L and the acidity at 2 mol / L; insert flake graphite as anode into the anode chamber, insert titanium plate as cathode into the cathode chamber; the anode chamber and cathode chamber are separated by a cation exchange membrane. The electrolysis temperature is 65 ° C, the voltage is 1 V, and the hydrochloric acid solution is regularly added to ensure that the rhodium concentration is ≮10 g / L and the copper ion concentration is ≯0.5 g / L during the electrolysis process. The rhodium powder precipitated from the cathode is washed with nitric acid or sulfuric acid and then dried to obtain rhodium powder with a purity greater than 99.99%. The current efficiency of the whole process is 81.5%, and the rhodium yield is 99.2%.

[0040] Example 2

[0041] (1) Mix unqualified rhodium powder (rhodium grade 94.2%) and sodium chloride in a mass ratio of 1:2, put into a quartz boat, put into a quartz tube furnace, connect chlorine gas into the quartz tube, heat to 750℃ and chlorinate for 4.5h. Rhodium generates soluble sodium chlororhodate, which is dissolved in 2mol / L HCl. The undissolved alloy rhodium powder enters the next medium-temperature chlorination cycle.

[0042] (2) Add 40% sodium hydroxide solution to start hydrolysis and adjust the pH value of the solution to 8.5. After the pH value stabilizes for half an hour, cool and filter, and wash with deionized water three times. Dissolve the rhodium hydrolysis residue with 4 mol / L hydrochloric acid, remove the acid, add water and measure the pH value, and control the sodium chlororhodate solution at pH = 1.5 by using 20% ​​liquid alkali.

[0043] (3) After pretreatment, the 732 type cation exchange resin with a pH value of 1.5 was mixed with a rhodium-containing solution with a pH value of 1.5 and stirred for 5 minutes, allowed to stand for 40 minutes and filtered; the resin was washed and regenerated with HCl with a pH value of 1.5 until there was no precious metal.

[0044] (4) After the base metals are removed, add 20% NaOH solution to adjust the pH to 13, pass chlorine gas twice until the pH drops to 9, and filter and wash. Dissolve the hydrolysis residue with 4 mol / L HCl for later use.

[0045] (5) Add 17% ammonium chloride solution to the anode chamber, add chlororhodic acid concentrate to the cathode chamber, and continue to add 10 mol / L hydrochloric acid to control the chlororhodic acid concentration at 20 g / L and the acidity at 6 mol / L; insert flake graphite as anode in the anode chamber and insert titanium plate as cathode in the cathode chamber; the anode chamber and cathode chamber are separated by a cation exchange membrane. The electrolysis temperature is 95 °C, the voltage is 1.1 V, and the chlororhodic acid concentrate is regularly added to ensure that the rhodium concentration is ≮10 g / L and the copper ion concentration is ≯0.5 g / L during the electrolysis process. The rhodium powder precipitated from the cathode is washed with nitric acid or sulfuric acid and then dried to obtain rhodium powder with a purity greater than 99.99%. The current efficiency of the whole process is 80.3%, and the rhodium yield is 99.1%.

[0046] Example 3

[0047] (1) Mix unqualified rhodium powder (rhodium grade 95.8%) and sodium chloride in a mass ratio of 1:2, put into a quartz boat, put into a quartz tube furnace, connect chlorine gas into the quartz tube, heat to 650℃ and chlorinate for 5h. Rhodium will generate soluble sodium chlororhodate, which will be dissolved in 2mol / L HCl. The undissolved alloy rhodium powder will enter the next medium-temperature chlorination cycle.

[0048] (2) Add 40% sodium hydroxide solution to start hydrolysis and adjust the pH value of the solution to 8. After the pH value stabilizes for half an hour, cool and filter, and wash with deionized water three times. Dissolve the rhodium hydrolysis residue with 4 mol / L hydrochloric acid, remove the acid, add water and measure the pH value, and control the sodium chlororhodate solution at pH = 1 by using 20% ​​liquid alkali.

[0049] (3) After pretreatment, the 732 type cation exchange resin with a pH value of 1.5 was mixed with a rhodium-containing solution with a pH value of 1 and stirred for 5 minutes, and then allowed to stand for 40 minutes and filtered; the resin was washed and regenerated with HCl with a pH value of 1.5 until there was no precious metal.

[0050] (4) After the base metals are removed, add 20% NaOH solution to adjust the pH to 13, pass chlorine gas to reduce the pH to 9, repeat twice, filter and wash. Dissolve the hydrolysis residue with 4 mol / L HCl for later use.

[0051] (5) Add 17% ammonium chloride solution to the anode chamber, add chlororhodic acid concentrate to the cathode chamber, continue to add 10 mol / L hydrochloric acid, control the chlororhodic acid concentration at 17 g / L, and the acidity at 10 mol / L; insert flake graphite as anode in the anode chamber, insert titanium plate as cathode in the cathode chamber; the anode chamber and cathode chamber are separated by a cation exchange membrane. The electrolysis temperature is 50 ° C, the voltage is -0.2 V, and the chlororhodic acid concentrate is regularly replenished to ensure that the rhodium concentration is ≮10 g / L and the copper ion concentration is ≯0.5 g / L during the electrolysis process. The rhodium powder precipitated from the cathode is washed with nitric acid or sulfuric acid and then dried to obtain rhodium powder with a purity greater than 99.99%. The current efficiency of the whole process is 81.3%, and the rhodium yield is 99.5%.

Claims

1. A method for reworking unqualified rhodium products, characterized in that: The steps include: 1) Medium-temperature chlorination: Mix unqualified rhodium powder and sodium chloride in a mass ratio of 1:1~1:4 and put them into a quartz boat. Then put the quartz boat into a quartz tube furnace, connect the chlorine inlet and outlet pipes, heat to 650~750℃ and chlorinate for 4~5h. Dissolve the chlorinated product with 1~2mol / L hydrochloric acid, and the undissolved matter enters the next medium-temperature chlorination cycle; 2) primary hydrolysis, adding a 35% to 45% NaOH solution to the hydrochloric acid solution obtained in step 1) to start hydrolysis, adjusting the pH value of the solution to 8 to 9, standing for 0.5 to 1 hour after the pH value stabilizes, cooling and filtering to obtain a hydrolysis residue and a hydrolysis liquid; washing the hydrolysis residue with deionized water for 2 to 3 times, and adding the washing water to the hydrolysis liquid for external use; 3) Acid dissolution and pH adjustment: the hydrolysis residue obtained in step 2) is dissolved with 2-5 mol / L hydrochloric acid, the pH value of the rhodium-containing solution is measured after the acid is driven out, and the pH value of the rhodium-containing solution is controlled to 1-1.5 by using a NaOH solution with a mass fraction of 15%-25%; 4) strong acid cation resin exchange, adding strong acid cation resin with a pH value of 1.5 to the rhodium-containing solution with a pH value of 1 to 1.5 obtained in step 3), mixing and stirring for 5 to 10 minutes, standing for 0.5 to 1 hour and then filtering; 5) Secondary hydrolysis: add 15% to 25% NaOH solution to the filtrate obtained in step 4) to adjust the pH to 12, pass chlorine gas to reduce the pH to 8 to 9, filter and wash to obtain hydrolysis residue and hydrolysis liquid; dissolve the hydrolysis residue in 2 to 5 mol / L hydrochloric acid for later use, and add the washing water to the hydrolysis liquid for external use; 6) Electrolysis, the hydrochloric acid solution obtained in step 5) is placed in the cathode chamber, the ammonium chloride solution or the sodium chloride solution is placed in the anode chamber, the cathode chamber and the anode chamber are separated by a cation exchange membrane, the electrolysis temperature is controlled at 50-95° C., the voltage is controlled at 0.2-1.5 V, and the rhodium concentration is ensured to be ≮10 g / L and the copper ion concentration is ≯0.5 g / L during the electrolysis process.

2. A method for reworking unqualified rhodium products according to claim 1, characterized in that: In step 1), the chlorination product is mainly sodium chlororhodate.

3. A method for reworking unqualified rhodium products as claimed in claim 1, characterized in that: In step 4), the strong acid cation resin is 732 type cation exchange resin.

4. A method for reworking an unqualified rhodium product as claimed in claim 1, characterized in that: In step 6), the concentration of the ammonium chloride solution is 5% to 17%, and the concentration of the sodium chloride solution is 5% to 8%.

5. A method for reworking an unqualified rhodium product as claimed in claim 1, characterized in that: In step 6), the concentration of rhodium ions in the hydrochloric acid solution is 5 g / L to 20 g / L, and the acidity is 2 to 10 mol / L.

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