Process for separating iodine and rhodium from a solution containing iodine and rhodium

Abstract

The present application relates to the field of purification and separation, and particularly relates to a method for separating iodine and rhodium from a solution containing iodine and rhodium. The method comprises the following steps: (1) adding an oxidizing agent and hydrogen peroxide into the solution containing iodine and rhodium to generate an oxidation reaction, obtaining a reaction liquid containing iodine, aging the reaction liquid, and filtering the aged reaction liquid to obtain a filtrate and a residue; (2) sublimating and purifying iodine product from the residue; adding a reducing agent into the filtrate to generate a reduction reaction, obtaining a reaction liquid containing rhodium, adding an inorganic acid into the reaction liquid to obtain a dissolution liquid, distilling the dissolution liquid to obtain a distillation liquid, adding activated carbon into the distillation liquid to perform adsorption, filtering, and ashing the obtained rhodium-containing residue to obtain a rhodium product. The method can reduce the cost of separating iodine and rhodium from a solution containing iodine and rhodium, effectively recovers rhodium metal and elemental iodine, simplifies the recovery process, and realizes resource recovery and recycling.

Description

Technical Field

[0001] This invention relates to the field of purification and separation, and more specifically to a method for separating iodine and rhodium from a solution containing iodine and rhodium. Background Technology

[0002] Rhodium-containing catalysts possess high selectivity and catalytic activity, making them widely used in chemical reactions such as hydroformylation, hydrogenation, and carbonyl synthesis, as well as in automotive exhaust purification catalysts. Metallic rhodium is present in the Earth's crust at a concentration of less than two parts per billion, making its reserves extremely scarce. Rhodium is not only expensive but also difficult to mine. Currently, spent rhodium-containing catalysts are listed as hazardous waste; improper disposal will lead to economic losses and environmental problems. Therefore, recovering the precious metal rhodium from spent catalysts not only effectively disposes of hazardous waste and achieves resource recycling but also possesses considerable economic and social value.

[0003] Acetic acid is an important chemical product and organic chemical intermediate in modern industry, widely used in pharmaceuticals, pesticides, printing and dyeing, and food processing. Currently, the mainstream process for acetic acid production worldwide is the methanol carbonylation method, which has abundant raw material supply and relatively low production costs and environmental pollution. While obtaining high-purity acetic acid, approximately 1% by volume of heavy component residue is produced. Its main component is acetic acid, and it also contains high-boiling-point polymers, water, iodine, potassium, and the precious metal rhodium.

[0004] Existing methods for recovering rhodium from organic solutions include the following:

[0005] CN111848674A discloses a method for the step-by-step recovery of effective components from waste rhodium Parker catalysts: First, the waste rhodium Parker catalyst is subjected to atmospheric distillation to remove light components, with butyraldehyde and butanol discharged via a side stream. Next, the residue from which low-boiling points have been removed is subjected to vacuum distillation to remove neutral components, with alkenal and octanol discharged via a side stream. Then, the residue from which neutral components have been removed is subjected to high-vacuum vacuum distillation to remove heavy components. The top distillate components from the light, neutral, and heavy component removal processes, along with the heavy rhodium-containing tar residue, are incinerated to produce ammonium phosphate, which can be used as fertilizer. The incineration residue is then purified by reduction to obtain rhodium powder. This method, through step-by-step recovery, achieves the recovery of the precious metal rhodium from waste rhodium Parker catalysts. The rhodium purity is high, and the recovery rate is high. However, this method has a long process flow and relatively complex steps.

[0006] CN1414125A discloses a method for recovering rhodium from spent rhodium catalysts in carbonyl synthesis reactions. The method involves using alkali metal or alkaline earth metal carbonates as additives, incinerating the spent catalyst residue at 650℃-700℃, and then reacting the remaining residue with molten alkali metal acid sulfates to obtain soluble rhodium salts. The rhodium is then separated using electrolysis. This method increases energy consumption.

[0007] CN1403604A discloses a method for recovering metallic rhodium from olefin carbonylation catalyst waste liquid. This method employs vacuum distillation, evaporation, and ashing to recover metallic rhodium. However, this method results in significant rhodium entrainment losses. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of low rhodium and iodine recovery rates in existing rhodium recovery methods, and to provide a method for recovering rhodium from rhodium-containing waste liquid. This method reduces the loss of iodine and rhodium during the recovery process, enables the effective recovery of precious metal rhodium and elemental iodine from waste catalysts, and simplifies the recovery process.

[0009] To achieve the above objectives, the present invention provides a method for separating iodine and rhodium from a solution containing iodine and rhodium, the method comprising the following steps:

[0010] (1) An oxidizing agent and hydrogen peroxide are added to a solution containing iodine and rhodium to produce an oxidation reaction, and a reaction solution containing iodine is obtained. The reaction solution is aged and then filtered to obtain filtrate and residue.

[0011] (2) Sublimation and purification of iodine products from filter residue; a reducing agent is added to the filtrate to produce a reduction reaction, and a reaction solution containing rhodium is obtained. An inorganic acid is added to the reaction solution to obtain a dissolution solution. The dissolution solution is distilled to obtain a distillate solution. Activated carbon is added to the distillate solution for adsorption. The solution is filtered, and the rhodium-containing filter residue is ashed to obtain rhodium products.

[0012] Through the above technical solution, the present invention has the following advantages:

[0013] The method of this invention can reduce the cost of separating iodine and rhodium from solutions containing iodine and rhodium, effectively recover rhodium metal and elemental iodine, simplify the recovery process, and realize the recovery and recycling of resources. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] In this invention, hydrogen peroxide is a 30% (w / w) aqueous solution of hydrogen peroxide.

[0016] This invention provides a method for separating iodine and rhodium from a solution containing iodine and rhodium, the method comprising the following steps:

[0017] (1) An oxidizing agent and hydrogen peroxide are added to a solution containing iodine and rhodium to produce an oxidation reaction, and a reaction solution containing iodine is obtained. The reaction solution is aged and then filtered to obtain filtrate and residue.

[0018] (2) Sublimation and purification of iodine products from filter residue; a reducing agent is added to the filtrate to produce a reduction reaction, and a reaction solution containing rhodium is obtained. An inorganic acid is added to the reaction solution to obtain a dissolution solution. The dissolution solution is distilled to obtain a distillate solution. Activated carbon is added to the distillate solution for adsorption. The solution is filtered, and the rhodium-containing filter residue is ashed to obtain rhodium products.

[0019] The method of this invention can reduce the cost of separating iodine and rhodium from solutions containing iodine and rhodium, effectively recover rhodium metal and elemental iodine, simplify the recovery process, and realize the recovery and recycling of resources.

[0020] In this invention, the content of iodine and rhodium in the solution containing iodine and rhodium can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the concentration of iodine in the solution containing iodine and rhodium is 30-3000 ppm, and the concentration of rhodium is 10-1000 ppm.

[0021] According to a preferred embodiment of the present invention, the solution containing iodine and rhodium is acetic acid production waste liquid.

[0022] According to a preferred embodiment of the present invention, the oxidant is selected from at least one of nitric acid, sulfuric acid, sodium hypochlorite, and ferric chloride, preferably nitric acid. By adopting the aforementioned preferred embodiment, the recovery rates of iodine and rhodium can be further improved.

[0023] According to a preferred embodiment of the present invention, the volume ratio of the oxidant to hydrogen peroxide is 0.1-0.5:1, for example, 0.25:1 or 0.35:1. By adopting the aforementioned preferred embodiment, the recovery rate of iodine and rhodium can be further improved.

[0024] According to a preferred embodiment of the present invention, the reducing agent is at least one selected from zinc powder, iron powder, magnesium powder, and aluminum powder, preferably a mixture of zinc powder and iron powder. By adopting the aforementioned preferred embodiment, the recovery rates of iodine and rhodium can be further improved.

[0025] According to a preferred embodiment of the present invention, the molar ratio of iron powder to zinc powder in the mixture is 1-5:1, preferably 2-4:1. By adopting the aforementioned preferred embodiment, the recovery rate of iodine and rhodium can be further improved.

[0026] According to a preferred embodiment of the present invention, the inorganic acid is at least one selected from nitric acid, sulfuric acid, and hydrochloric acid, preferably hydrochloric acid. By adopting the aforementioned preferred embodiment, the recovery rates of iodine and rhodium can be further improved. The present invention uses hydrochloric acid with a mass concentration of 36.5% as an example.

[0027] In this invention, the conditions for the oxidation reaction can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the conditions for the oxidation reaction include: the mass ratio of the amount of oxidant to the mass of iodine in the solution containing iodine and rhodium is 0.1-0.5:1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, or 0.5:1.

[0028] According to a preferred embodiment of the present invention, the conditions for the oxidation reaction include a temperature of 60-85°C.

[0029] In this invention, the aging conditions can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the aging conditions include a temperature of 30-50°C. The aging time is adjusted according to the aging temperature and other conditions, for example, the time is 0.5-2 hours, preferably 1-1.5 hours.

[0030] In this invention, the sublimation temperature can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the sublimation temperature is 60-100°C, preferably 80-85°C.

[0031] In this invention, the conditions for the reduction reaction can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the conditions for the reduction reaction include: the molar ratio of the amount of reducing agent to the molar ratio of rhodium in the solution containing iodine and rhodium is 0.7-1.5:1, preferably 1-1.4:1.

[0032] According to a preferred embodiment of the present invention, the conditions for the reduction reaction include: a temperature of 60-90°C, preferably 60-80°C, and a reaction time adjusted according to the reaction temperature and other conditions, for example, a time of 0.5-2 hours, preferably 1-1.5 hours.

[0033] In this invention, the distillation conditions can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the distillation conditions include: a temperature of 70-100°C, preferably 80-90°C, and a distillation time that is adjusted according to the reaction temperature and other conditions, for example, a time of 3-5 hours, preferably 4-5 hours.

[0034] In this invention, during the process of sublimating and purifying iodine products from filter residue, residual filter paper is combined with rhodium-containing filter residue and then ashed.

[0035] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents used in the following examples are commercially available products.

[0036] In the following embodiments:

[0037] Iodine recovery rate determination: The iodine recovery rate is determined by weighing. The calculation formula is as follows:

[0038] x% = m2 / m1 × 100%. Where: x is the iodine recovery rate, %; m1 is the iodine content in the acetic acid production waste liquid, g; m2 is the weight of iodine obtained after purification, g.

[0039] Rhodium recovery rate determination: The rhodium recovery rate is determined by a weighing method. The calculation formula is as follows:

[0040] y% = m4 / m3 × 100%. Where: y is the rhodium recovery rate, %; m3 is the rhodium content in the acetic acid production waste liquid, g; m4 is the rhodium content in the ashing slag, g.

[0041] The acetic acid production waste liquid used in the following examples is a rhodium catalyst from a methanol carbonylation unit for acetic acid production in a chemical company. In the following examples, the mass fraction of nitric acid is 68% (density 1.4 g / ml), and the mass fraction of hydrochloric acid is 36.5% (density 1.19 g / ml). Unless otherwise specified, "%" refers to mass.

[0042] Example 1

[0043] 2000 mL of catalyst waste liquid containing 25.8 ppm rhodium (51.6 mg rhodium and 154.8 mg iodine) was weighed. Under stirring, 47.6 mg of 68% nitric acid and 190.5 mg of 30% hydrogen peroxide were added dropwise. A large amount of purplish-black crystals appeared in the solution, and stirring was stopped. After aging at 40°C for 1 hour, the solution was vacuum filtered and purified by sublimation at 80°C to obtain 127.1 mg of elemental iodine. The sublimed filter paper was retained for later use. The iodine recovery rate was measured to be 82.1%. 13.1 mg of zinc powder and 22.4 mg of iron powder were added to the filtrate, and the mixture was heated and stirred at 60°C for 1 hour. Then, 50 mL of 36.5% hydrochloric acid was added. The solution was distilled at 85℃ for 4 hours. A small amount of activated carbon (0.1% of the solution mass, 2 g) was added to the distillate for adsorption. After 1 hour, the mixture was vacuum filtered to obtain a displacement residue. This residue was combined with sublimated filter paper and ashed to obtain 51.0 mg of ashed residue. The rhodium recovery rate was calculated to be 99.3%.

[0044] Example 2

[0045] Weigh 2000 ml of catalyst waste liquid containing 92.6 ppm rhodium (185.2 mg rhodium and 555.6 mg iodine). Add 100 mg 68% nitric acid and 683.9 mg 30% hydrogen peroxide dropwise under stirring. A large number of purplish-black crystals appear in the solution, and stop stirring. After aging for 1 hour, the solution was vacuum filtered and purified by sublimation at 80°C to obtain 449.0 mg of refined iodine. The sublimated filter paper was retained for later use. The iodine recovery rate was measured to be 80.8%. 31.1 mg of zinc powder and 80.4 mg of iron powder were added to the filtrate, and the mixture was heated and stirred at 60°C for 1 hour. Then, 50 ml of 36.5% hydrochloric acid was added, and the solution was distilled at 85°C for 4 hours. A small amount of activated carbon (0.1% of the solution mass, 2 g) was added to the distillate for adsorption. After 1 hour, the solution was vacuum filtered to obtain a displacement residue, which was combined with the sublimated filter paper and ashed to obtain 183.9 mg of ashed residue. The rhodium recovery rate was 99.1%.

[0046] Example 3

[0047] Weigh 4000 ml of catalyst waste liquid containing 9.8 ppm rhodium (39.2 mg rhodium and 117.6 mg iodine). Add 56.2 mg 68% nitric acid and 144.8 mg 30% hydrogen peroxide dropwise under stirring until a large number of purplish-black crystals appear in the solution, then stop stirring. After aging for 1.5 hours, the solution was vacuum filtered and purified by sublimation at 80°C to obtain 96.0 mg of refined iodine. The sublimated filter paper was retained for later use. The iodine recovery rate was measured to be 81.6%. 10.0 g of zinc powder and 34.0 mg of iron powder were added to the filtrate, and the mixture was heated and stirred at 60°C for 1 hour. Then, 50 ml of 36.5% hydrochloric acid was added, and the solution was distilled at 85°C for 4 hours. A small amount of activated carbon (0.25% of the solution mass, 100 g) was added to the distillate for adsorption. After 1.5 hours, the solution was vacuum filtered to obtain a displacement residue, which was combined with the sublimated filter paper and ashed to obtain 38.7 mg of ashed residue. The rhodium recovery rate was 98.6%.

[0048] Example 4

[0049] Similar to Example 1, except that sulfuric acid of equal concentration and mass was used as the oxidant, the recovery rate of iodine was 78.9% and the recovery rate of rhodium was 97.3%.

[0050] Example 5

[0051] Similar to Example 1, except that only 33.6 mg of iron powder was added to the filtrate as a reducing agent, the recovery rate of iodine was 82.1%, and the recovery rate of rhodium was 97.5%.

[0052] Example 6

[0053] Similar to Example 1, except that 26 mg of zinc powder and 11.2 mg of iron powder were added to the filtrate, the recovery rate of iodine was 82.1%, and the recovery rate of rhodium was 97.9%.

[0054] Comparative Example 1

[0055] 2000 mL of catalyst waste liquid containing 25.8 ppm rhodium (51.6 mg rhodium and 154.8 mg iodine) was weighed. 238.1 mg of 68% nitric acid was added dropwise under stirring. A large amount of purplish-black crystals appeared in the solution, and stirring was stopped. After aging at 40°C for 1 hour, the solution was vacuum filtered and purified by sublimation at 80°C to obtain 120.0 mg of elemental iodine. The sublimed filter paper was retained for later use. The iodine recovery rate was measured to be 77.5%. 13.1 mg of zinc powder and 22.4 mg of iron powder were added to the filtrate, and the mixture was heated and stirred at 60°C for 1 hour. Then, 50 mL of 36.5% hydrochloric acid was added. The solution was distilled at 85°C for 4 hours. A small amount of activated carbon (0.1% of the solution mass, 2 g) was added to the distillate for adsorption. After 1 hour, the solution was vacuum filtered to obtain a displacement residue, which was combined with the sublimed filter paper and ashed to obtain 49.6 mg of ashed residue. After conversion, the rhodium recovery rate is 96.1%.

[0056] Comparative Example 2

[0057] 2000 mL of catalyst waste liquid containing 25.8 ppm rhodium (51.6 mg rhodium and 154.8 mg iodine) was weighed. 47.6 mg of 68% nitric acid and 190.5 mg of 30% hydrogen peroxide were added dropwise under stirring. A large amount of purplish-black crystals appeared in the solution, and stirring was stopped. After aging at 40°C for 1 hour, the solution was vacuum filtered and purified by sublimation at 80°C to obtain 127.1 mg of elemental iodine. The sublimed filter paper was retained for later use, and the iodine recovery rate was measured to be 82.1%. 13.1 mg of zinc powder and 22.4 mg of iron powder were added to the filtrate, and the solution was heated and stirred at 60°C for 1 hour. The solution was distilled at 85°C for 4 hours. A small amount of activated carbon (0.1% of the solution mass, 2 g) was added to the distillate for adsorption. After 1 hour, the solution was vacuum filtered to obtain a displacement residue, which was combined with the sublimed filter paper and ashed to obtain 49.3 mg of ashed residue. After conversion, the rhodium recovery rate is 95.5%.

[0058] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for separating iodine and rhodium from a solution containing iodine and rhodium, characterized in that, The method includes the following steps: (1) An oxidizing agent and hydrogen peroxide are added to a solution containing iodine and rhodium to produce an oxidation reaction, and a reaction solution containing iodine is obtained. The reaction solution is aged and then filtered to obtain filtrate and filter residue. (2) Sublimation and purification of iodine products from filter residue; a reducing agent is added to the filtrate to produce a reduction reaction, and a reaction solution containing rhodium is obtained. An inorganic acid is added to the reaction solution to obtain a dissolution solution. The dissolution solution is distilled to obtain a distillate solution. Activated carbon is added to the distillate solution for adsorption. The solution is filtered, and the rhodium-containing filter residue is ashed to obtain rhodium products.

2. The method according to claim 1, wherein, The iodine concentration in the solution containing iodine and rhodium is 30-3000 ppm, and the rhodium concentration is 10-1000 ppm; preferably, the solution containing iodine and rhodium is acetic acid production waste liquid; and / or The oxidant is selected from at least one of nitric acid, sulfuric acid, sodium hypochlorite and ferric chloride, preferably nitric acid; and / or the volume ratio of the oxidant to hydrogen peroxide is 0.1-0.5:

1.

3. The method according to claim 1 or 2, wherein, The reducing agent is at least one of zinc powder, iron powder, magnesium powder and aluminum powder, preferably a mixture of zinc powder and iron powder; Preferably, the molar ratio of iron powder to zinc powder in the mixture is 1-5:1, more preferably 2-4:

1.

4. The method according to any one of claims 1-3, wherein, The inorganic acid is at least one of nitric acid, sulfuric acid, and hydrochloric acid, preferably hydrochloric acid.

5. The method according to any one of claims 1-4, wherein, The conditions for the oxidation reaction include: The mass ratio of the oxidant used to the iodine in the solution containing iodine and rhodium is 0.1-0.5:1; and / or The temperature is 60-85℃.

6. The method according to any one of claims 1-5, wherein, The aging conditions include: a temperature of 30-50°C; and / or a time of 0.5-2 hours.

7. The method according to any one of claims 1-6, wherein, The sublimation temperature is 60-100℃, preferably 80-85℃.

8. The method according to any one of claims 1-7, wherein, The conditions for the reduction reaction include: The molar ratio of the reducing agent to rhodium in the solution containing iodine and rhodium is 0.7-1.5:1, preferably 1-1.4:1; and / or the temperature is 60-90℃, preferably 60-80℃; and / or the time is 0.5-2h, preferably 1-1.5h.

9. The method according to any one of claims 1-8, wherein, The distillation conditions include: The temperature is 70-100℃, preferably 80-90℃; and / or The time is 3-5 hours, preferably 4-5 hours.

10. The method according to any one of claims 1-9, wherein, During the process of sublimating and purifying iodine products from filter residue, residual filter paper is combined with rhodium-containing filter residue and ashed.