A method for recovering rhodium and cobalt from detecting waste rhodium complex salt

Abstract

The invention discloses a method for recovering rhodium and cobalt from detection waste rhodium complex salt, and relates to the field of rhodium and cobalt recovery and utilization. The method destroys the chemical coordination state of rhodium complex salt by digestion, converts it into rhodium and cobalt ion state, and then utilizes the chemical properties of rhodium and cobalt, adopts oxidation and reduction, wet method and fire method to study the separation and purification method of rhodium and cobalt, finally separates rhodium and cobalt, purifies rhodium to obtain rhodium powder, and realizes the recovery of rhodium. The purity of rhodium powder recovered by the invention can reach more than 99%, the yield of rhodium powder can reach more than 98%, and cobalt is recovered in the form of cobalt chloride, realizing the recovery and utilization of rare and precious metal resources.

Description

Technical Field

[0001] The invention relates to the field of recycling of rhodium and cobalt, and in particular to a method for recycling rhodium and cobalt from detection waste rhodium double salt (hexaammine cobalt rhodium nitrate). Background Art

[0002] The precious metal rhodium has a very low content in nature, high industrial value and is expensive, so the recycling of rhodium resources has always been a focus of social attention.

[0003] Due to the different forms and states of rhodium in various waste materials, the recycling methods are also different. The common sources of rhodium recycling are mainly industrial rhodium-containing waste, such as rhodium-containing catalysts, rhodium-containing waste liquids, rhodium-containing waste residues, etc. These industrial waste rhodium are large in quantity and complex in state. They usually need to be concentrated or incinerated. The process is complicated, the environmental pollution is large, and the energy consumption is high. Only crude rhodium can be obtained in one recycling. The rhodium content is between 70% and 95%, and the impurity content is high. It needs to be purified many times to obtain more than 99% rhodium powder.

[0004] The rhodium complex salt used to detect waste is the precipitated hexaammine cobalt rhodium nitrate (Rh(NO2)6.Co(NH3)6) obtained by measuring the rhodium content by the hexaammine cobalt nitrate weight method. In fact, rhodium complex salt exists wherever the rhodium content is measured. This material is relatively pure, but has no further application value and can only be recycled as waste. This material is very stable and cannot be dissolved or destroyed by hydrochloric acid, nitric acid, or aqua regia. There is also the problem of separating rhodium and cobalt. The conventional treatment in the industry is to mix it with other rhodium-containing waste residues for recycling. This results in a high impurity content in the crude rhodium obtained after recycling, and the quality is inconsistent. The purity is between 70% and 95%, and it needs to be purified again.

[0005] There has been no targeted research and methods so far, and the recovery of rhodium in the complex salt has always been a problem in the precious metal industry, resulting in the inability to effectively recycle this part of rhodium. Summary of the invention

[0006] The present invention is a method for recovering rhodium from rhodium complex salt hexaammine cobalt rhodium nitrate, which is a waste material. The method involves separation and purification of rhodium and cobalt and is suitable for recovering rhodium and cobalt from rhodium complex salt hexaammine cobalt rhodium nitrate, which is a waste material.

[0007] The invention uses high-concentration sulfuric acid to digest and destroy the chemical coordination state of the waste rhodium complex salt, converting it into the ionic state of rhodium and cobalt, and then using the chemical properties of rhodium and cobalt, adopting oxidation and reduction, wet method and fire method to study the separation and purification method of rhodium and cobalt, finally separating rhodium and cobalt, purifying rhodium to obtain rhodium powder, realizing the recovery of rhodium, the purity of rhodium recovered once can reach more than 99%, and the cobalt is recovered in the form of cobalt chloride.

[0008] The specific technical scheme of the present invention is:

[0009] A method for recovering rhodium and cobalt from detecting waste rhodium double salts comprises the following steps:

[0010] S1, add an appropriate amount of sulfuric acid solution into a beaker containing hexaammine cobalt rhodium nitrate and heat until the material is completely dissolved;

[0011] S2, add appropriate amount of water, stirring while adding water to dilute sulfuric acid;

[0012] S3, add an appropriate amount of sodium hydroxide solution to adjust the pH and heat, and add an appropriate amount of hydrazine hydrate in portions during the heating process until the solution is clear and the precipitation is complete;

[0013] S4, filtering and washing the solution precipitate, transferring the filter cake into a crucible, and ashing in an ashing furnace;

[0014] S5, after the ashing is completed, the metal and oxide in the crucible are transferred to a beaker, and an appropriate amount of hydrochloric acid is added and heated to dissolve the cobalt oxide to form a pink cobalt oxide solution. Rhodium is insoluble in hydrochloric acid and becomes a precipitate;

[0015] S6, filtering the rhodium precipitate with filter paper, washing the filter residue with hydrochloric acid for 3-5 times, and then repeatedly washing the filter residue with hot water until the filtrate is neutral, the rhodium is retained in the filter residue, and the cobalt is separated out in the filtrate in the form of cobalt chloride, and recovered after concentration and crystallization;

[0016] S7, placing the rhodium filter residue together with the filter paper in a crucible and ashing again in an ashing furnace;

[0017] S8, the ashing crucible is cooled and placed in a hydrogen reduction furnace for reduction to obtain rhodium powder.

[0018] Further:

[0019] The concentration of sulfuric acid is 40%-98%; the concentration of sodium hydroxide solution is 15%; the concentration of hydrochloric acid is 10%-20%;

[0020] The amount of water added is 2-3 times the original volume by volume;

[0021] The temperature of ashing in the ashing furnace is 300°C-500°C; the temperature of reduction in the hydrogen reduction furnace is 650°C-800°C; the temperature of re-ashing in the ashing furnace is 750°C-850°C;

[0022] Add hydrazine hydrate in three portions, with the second and third additions being half of the first.

[0023] The beneficial effects of the present invention include:

[0024] (1) Conventional processing is exactly mixed in other rhodium-containing waste residues and recovered together, which causes the crude rhodium impurity content obtained after recovery to be high, and the purity is between 70% and 95%, and it is also necessary to purify again. The present invention, according to the chemical properties of rhodium double salt, can recycle the purity of rhodium powder once to reach more than 99%;

[0025] (2) First, the insoluble rhodium complex salt is destroyed by digestion with sulfuric acid. Other acids cannot dissolve it. The concentration of sulfuric acid used is required. Only sulfuric acid with a concentration of more than 40% can completely dissolve it. After dissolution, an ion solution of rhodium and cobalt is formed. Then, a reducing agent is used to reduce the mixed precipitate of rhodium black and cobalt. According to the different chemical properties of rhodium and cobalt, the mixed precipitate is subjected to low-temperature ashing oxidation at 300° C.-500° C. The easily decomposable impurities of ammonia decompose and volatilize in this process. Cobalt is oxidized to cobalt oxide. Rhodium is relatively stable and will not change at a temperature of less than 500° C. and will not dissolve in dilute hydrochloric acid. Cobalt will form cobalt oxide, which can be dissolved in dilute hydrochloric acid. By adding dilute hydrochloric acid to dissolve the cobalt oxide, rhodium is still in the form of precipitation. Rhodium and cobalt are separated by filtration. If the low-temperature ashing oxidation is removed and hydrochloric acid is used directly for dissolution, the dissolution rate is very slow, the cobalt-rhodium separation effect is very poor, and the recovery purity of rhodium cannot reach 99%.

[0026] (3) The separated rhodium precipitate is washed to remove soluble impurities, and then ashed at 750°C-850°C to remove volatile impurities, and finally reduced to more than 99% rhodium powder by hydrogen at 650°C-800°C. Here, more than 99% rhodium powder that can be directly reused can be obtained in one recovery process, without consuming resources for repeated purification, and the recycling of rare and precious metal resources can be achieved at one time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the method for recovering rhodium and cobalt. DETAILED DESCRIPTION

[0028] Example 1

[0029] A method for recovering rhodium and cobalt from detecting waste rhodium double salts comprises the following steps:

[0030] Step 1: Take 200g of the waste material hexaammine cobalt rhodium nitrate and put it in a 1L beaker;

[0031] Step 2: Add 50 mL of 40% sulfuric acid solution to the beaker containing the sample, place it on a 400°C electric furnace, cover it with a watch glass and heat for 60 minutes until the material is completely dissolved;

[0032] Step 3: Remove the beaker and add 100 mL of deionized water, stirring while adding water to prevent boiling and splashing;

[0033] Step 4: Add 30 mL of 15% sodium hydroxide solution, add 100 mL of hydrazine hydrate, heat on an electric furnace for 10 min, add 50 mL of hydrazine hydrate, continue heating for 10 min, add 50 mL of hydrazine hydrate again, and continue heating until the solution is clear and the precipitation is complete;

[0034] Step 5: Filter the precipitate with medium-speed filter paper, transfer the filter cake to a crucible, and incinerate in an incineration furnace at 400°C for 2 hours with air;

[0035] Step 6: After the ashing is completed, transfer the metal and oxide in the crucible to a 500 ml beaker, add 200 ml of 10% hydrochloric acid and heat to dissolve for 30 minutes. The cobalt oxide becomes a deep pink cobalt chloride solution, and rhodium is insoluble in hydrochloric acid and becomes a precipitate;

[0036] Step 7: Filter the rhodium precipitate with filter paper, wash the filter with 50 ml of 10% hydrochloric acid, and then repeatedly wash the filter residue with 1 L of hot water until the filtrate is neutral, the rhodium is retained in the filter residue, and the cobalt is separated in the filtrate in the form of cobalt chloride, which is concentrated and crystallized;

[0037] Step 8: Place the rhodium filter residue together with the filter paper in a crucible and ash again in an ashing furnace at 800°C for 3 hours;

[0038] Step 9: The ashing crucible was taken out after cooling, and placed in a hydrogen reduction furnace for reduction at 750°C for 1 hour. Finally, the rhodium powder was taken out and weighed to obtain a weight of 37.67 g. The purity of the rhodium powder was determined by ICP, and the purity reached 99.6wt%. The theoretical value of the rhodium powder was 38.10g according to the molecular formula. The yield of the rhodium powder was calculated based on the actual weight and purity of the rhodium powder, and the yield of the rhodium powder reached 98.5%.

[0039] Example 2

[0040] A method for recovering rhodium and cobalt from detecting waste rhodium double salts comprises the following steps:

[0041] Step 1: Take 200g of the waste material hexaammine cobalt rhodium nitrate and put it in a 1L beaker;

[0042] Step 2: Add 50 mL of 80% sulfuric acid solution to the beaker containing the sample, place it on a 400°C electric furnace, cover it with a watch glass and heat for 30 minutes until the material is completely dissolved;

[0043] Step 3: Remove the beaker and add 200 mL of deionized water, stirring while adding water to prevent boiling and splashing;

[0044] Step 4: Add 50 mL of 15% sodium hydroxide solution, add 100 mL of hydrazine hydrate, heat on an electric furnace for 10 min, add 50 mL of hydrazine hydrate, continue heating for 10 min, add 50 mL of hydrazine hydrate again, and continue heating until the solution is clear and the precipitation is complete;

[0045] Step 5: Filter the precipitate with medium-speed filter paper, transfer the filter cake to a crucible, and incinerate in an incineration furnace at 500°C for 2 hours with air;

[0046] Step 6: After the ashing is completed, transfer the metal and oxide in the crucible to a 500 ml beaker, add 200 ml of 20% hydrochloric acid and heat to dissolve for 30 minutes. The cobalt oxide becomes a deep pink cobalt chloride solution, and rhodium is insoluble in hydrochloric acid and becomes a precipitate;

[0047] Step 7: Filter the rhodium precipitate with filter paper, wash the filter with 50 ml of 20% hydrochloric acid, and then repeatedly wash the filter residue with 1 L of hot water until the filtrate is neutral, the rhodium is retained in the filter residue, and the cobalt is separated in the filtrate in the form of cobalt chloride, which is concentrated and crystallized;

[0048] Step 8: Place the rhodium filter residue together with the filter paper in a crucible and ash again in an ashing furnace at 800°C for 3 hours;

[0049] Step 9: The ashing crucible was taken out after cooling, and placed in a hydrogen reduction furnace for reduction at 750°C for 1 hour. Finally, the rhodium powder was taken out and weighed to obtain a weight of 37.39 g. The purity of the rhodium powder was determined by ICP, and the purity reached 99.4wt%. The theoretical value of the rhodium powder was 38.10g according to the molecular formula. The yield of the rhodium powder was calculated based on the actual weight and purity of the rhodium powder, and the yield of the rhodium powder reached 98.1%.

[0050] Example 3

[0051] A method for recovering rhodium and cobalt from detecting waste rhodium double salts comprises the following steps:

[0052] Step 1: Take 200g of the waste material hexaammine cobalt rhodium nitrate and put it in a 1L beaker;

[0053] Step 2: Add 50 mL of 35% sulfuric acid solution to the beaker containing the sample, place it on a 400°C electric furnace, cover it with a watch glass and heat it. After heating for 3 hours, the material still cannot be completely dissolved; the next step cannot be performed.

[0054] Example 4

[0055] A method for recovering rhodium and cobalt from detecting waste rhodium double salts comprises the following steps:

[0056] Step 1: Take 200g of the waste material hexaammine cobalt rhodium nitrate and put it in a 1L beaker;

[0057] Step 2: Add 50 mL of 40% sulfuric acid solution to the beaker containing the sample, place it on a 400°C electric furnace, cover it with a watch glass and heat for 60 minutes until the material is completely dissolved;

[0058] Step 3: Remove the beaker and add 200 mL of deionized water, stirring while adding water to prevent boiling and splashing;

[0059] Step 4: Add 50 mL of 15% sodium hydroxide solution, add 100 mL of hydrazine hydrate, heat on an electric furnace for 10 min, add 50 mL of hydrazine hydrate, continue heating for 10 min, add 50 mL of hydrazine hydrate again, and continue heating until the solution is clear and the precipitation is complete;

[0060] Step 5: Filter the precipitate with medium-speed filter paper, transfer the filter cake to a beaker, directly add 200 mL of 10% hydrochloric acid and heat to dissolve for 3 hours. The solution is light pink, and the separation of cobalt and rhodium is slow.

[0061] Step 7: Filter the precipitate with filter paper, wash the filter with 50 ml of 10% hydrochloric acid, and then repeatedly wash the filter residue with 1 L of hot water until the filtrate is neutral, rhodium is retained in the filter residue, and cobalt is separated out in the filtrate in the form of cobalt chloride, which is concentrated and crystallized;

[0062] Step 8: Place the rhodium filter residue together with the filter paper in a crucible and ash again in an ashing furnace at 800°C for 3 hours;

[0063] Step 9: After the ashing crucible is cooled, take it out and place it in a hydrogen reduction furnace for reduction at 750°C for 1 hour. Finally, take it out to obtain crude rhodium powder. After weighing, the weight of the crude rhodium powder is 47.39g. The theoretical value of rhodium powder is 38.10g calculated according to the molecular formula. The purity of rhodium powder is obtained by ICP measurement. The purity is only 69.4wt% and the cobalt content is 28.9%.

[0064] It can be seen from the embodiments that the greatest advantage of the present invention over the prior art is that it utilizes the different chemical properties of rhodium and cobalt, organically combines oxidation and reduction, wet method and pyrolysis and other technical means to form a complete technical route for recovery, and specifically carries out dissolution, reduction, ashing, re-dissolution, filtration separation, re-ashing and re-reduction. Each process is a process of purification and separation, and the steps cannot be reduced. The purity of the rhodium recovered at one time can reach more than 99%, and the yield of rhodium powder can reach more than 98%. The recovered rhodium powder can be directly produced and used without the need for subsequent repeated purification.

Claims

1. A method for recovering rhodium and cobalt from detecting waste rhodium double salts, characterized in that: The chemical coordination state of the rhodium complex salt is digested and converted into the ionic state of rhodium and cobalt. Then, rhodium and cobalt are separated by a combination of oxidation and reduction, wet method and fire method, and the rhodium is purified to obtain rhodium powder to achieve rhodium recovery, and cobalt is recovered in the form of cobalt chloride.

2. The method according to claim 1, characterized in that The specific steps include: S1, add appropriate amount of sulfuric acid into a beaker containing rhodium complex salt hexaammine cobalt rhodium nitrate and heat until the material is completely dissolved; S2, add appropriate amount of water and stir while adding water; S3, adding an appropriate amount of sodium hydroxide solution and heating, and adding an appropriate amount of hydrazine hydrate in portions during the heating process until the solution is clear and the precipitation is complete; S4, filtering the solution precipitate, transferring the filter cake into a crucible, and ashing in an ashing furnace; S5, after the ashing is completed, the metal and oxide in the crucible are transferred to a beaker, and an appropriate amount of hydrochloric acid is added to heat and dissolve the cobalt oxide to form a pink cobalt oxide solution. Rhodium is insoluble in hydrochloric acid and becomes a precipitate; S6, filtering the rhodium precipitate with filter paper, washing the filter residue with hydrochloric acid, and then repeatedly washing the filter residue with hot water until the filtrate is neutral, the rhodium is retained in the filter residue, and the cobalt is separated out in the filtrate in the form of cobalt chloride, and recovered after concentration and crystallization; S7, placing the rhodium filter residue together with the filter paper in a crucible and ashing again in an ashing furnace; S8, the ashing crucible is cooled and placed in a hydrogen reduction furnace for reduction to obtain rhodium powder.

3. The method according to claim 2, characterized in that In step S1, the concentration of sulfuric acid added is 40%-98%.

4. The method according to claim 2, characterized in that: In step S2, the amount of water added is 2-3 times the original volume by volume.

5. The method according to claim 2, characterized in that: In step S4, the ashing temperature in the ashing furnace is 300°C-500°C.

6. The method according to claim 2, characterized in that In step S8, the reduction temperature in the hydrogen reduction furnace is 650°C-800°C.

7. The method according to claim 2, characterized in that In step S7, the temperature of the re-ashing in the ash furnace is 750°C-850°C.

8. The method according to claim 2, characterized in that: In step S3, hydrazine hydrate is added in three times, wherein the amount added in the second and third times is half of the amount added in the first time.

9. The method according to any one of claims 2 to 8, characterized in that: In step S3, the concentration of the sodium hydroxide solution is 15%; In step S6, the concentration of hydrochloric acid is 10%-20%.

10. The method according to any one of claims 2 to 8, characterized in that: In step S8, the purity of the rhodium powder is above 99 wt % and the yield is above 98 %.

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