Method for recovering trace iridium in solution

Abstract

The invention relates to the technical field of precious metal recovery, in particular to a method for recovering trace iridium in a solution, trace iridium in the solution is recovered by utilizing a vulcanizing agent, liquid-phase ppm-level iridium is transferred to solid-phase to obtain about 5% iridium-containing sulfide, the process is short in time consumption and low in energy consumption, and then chloroiridic acid is prepared through the processes of impurity removal, melting, chemical precipitation and the like. The problems that a large amount of salt is separated out and the iridium enrichment rate is low due to direct solvent evaporation are solved, iridium recovery is effectively achieved, and cost reduction and efficiency improvement are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal recovery, and in particular to a method for recovering trace iridium in a solution. Background Art

[0002] Iridium is a scarce precious metal resource with a high melting point, high strength, high corrosion resistance, and unique catalytic properties. It plays an irreplaceable and important role in numerous fields, including aerospace, electronics, chemicals, and medicine. However, iridium is present in extremely low concentrations in the Earth's crust, making its development and smelting costs prohibitive. Industrial production processes often generate large amounts of wastewater containing trace amounts of iridium. Recovering trace iridium from these wastewaters has important economic and environmental implications for improving iridium resource utilization, reducing production costs, and minimizing resource waste.

[0003] Currently, the common method for recovering iridium from solution is to convert iridium into oxide by evaporating the solvent and then roasting it, then converting the iridium into a readily soluble form using medium-temperature chlorination or alkali melting methods, and then converting the iridium into solution through hydrochloric acid leaching. However, these methods are cumbersome to operate, have lengthy processes, cause large iridium losses, and require the addition of large amounts of auxiliary materials. They are only suitable for waste liquids with low impurity content and high iridium content, and require repeated melting, resulting in low recovery rates. For low-concentration complex iridium-containing solutions, a method of neutralization precipitation, adsorbent / flocculant adsorption, filtration, and incineration enrichment or the use of strong reducing agents to reduce iridium byproducts is usually adopted. Both methods have disadvantages such as complex processes, low iridium enrichment rates, a large number of impurity elements, and environmental pollution.

[0004] Therefore, there is an urgent need to develop a method for efficiently recovering trace iridium from iridium-containing waste liquid and converting it into chloroiridic acid, which is of great significance for reducing production costs. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for recovering trace iridium in a solution, which utilizes a sulfiding agent to recover the trace iridium in the solution, and transfers the ppm-level iridium in the liquid phase to the solid phase to obtain about 5% iridium-containing sulfide. The process is short in time and has low energy consumption. Subsequently, impurity removal, melting, iridium precipitation, and aqua regia dissolution are performed to prepare chloroiridic acid, thereby achieving efficient recovery of trace iridium in iridium-containing waste liquid, with high recovery rate, strong operability, easy large-scale processing, low auxiliary material cost, reduced iridium loss, and cost reduction and efficiency improvement.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for recovering trace iridium in a solution comprises the following steps:

[0008] Step 1, adjusting the pH of the solution: adjusting the pH of the iridium-containing waste liquid to greater than 12, and then heating and keeping the waste liquid warm;

[0009] Step 2, sulfidation precipitation: heating the waste liquid treated in step 1 to boil, adding a sulfiding agent after boiling and stirring until no black precipitate is precipitated, cooling to room temperature and performing solid-liquid separation to obtain an iridium sulfide solid;

[0010] Step 3, removing impurities with boiling water: boiling the iridium sulfide solid obtained in step 2 with water to remove impurities, and then performing solid-liquid separation to obtain the iridium sulfide solid after impurities removal;

[0011] Step 4, high-temperature calcination: drying the iridium sulfide solid obtained in step 3 after removing impurities, and then calcining it at high temperature;

[0012] Step 5, alkali fusion roasting: adding an oxidant to the solid obtained in step 4 and roasting it at high temperature; the oxidant is sodium peroxide or sodium chlorate;

[0013] Step 6, mixed acid leaching: washing the reaction product obtained in step 5 with water and then performing mixed acid leaching;

[0014] Step 7, chemical precipitation: the reaction product obtained in step 6 is subjected to solid-liquid separation, the separated solution is heated, and then ammonium chloride is added for chemical precipitation;

[0015] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, and then a reducing agent is added and heated;

[0016] The volume ratio of the reducing agent to the slurried solution is 1:50 to 200;

[0017] The reducing agent is any one of ammonium sulfide, sodium sulfide and hydrazine hydrate;

[0018] Step 9, sulfurization and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and a sulfurizing agent is added to the separated solution to perform sulfurization and impurity removal;

[0019] The volume ratio of the sulfiding agent to the solution is 1:20-100;

[0020] The vulcanizing agent is ammonium sulfide or sodium sulfide;

[0021] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, an oxidant is added to the separated solution and heated, ammonium chloride is then added to precipitate, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide;

[0022] The volume ratio of the oxidant to the solution is 1:10-50;

[0023] The oxidant is any one of nitric acid, hydrogen peroxide and sodium chlorate;

[0024] Step 11, aqua regia dissolution: dissolving the iridium oxide solid obtained in step 10 in aqua regia and heating and concentrating the solution to obtain chloroiridic acid; the liquid-to-solid ratio of the aqua regia to the solid is 3 to 8:1, and the unit of the liquid-to-solid ratio is ml / g.

[0025] Preferably, in step 1, sodium hydroxide solution is used to adjust the pH of the solution; the heating conditions are: heating temperature is 80-100° C., and heating time is 1.5-3 hours.

[0026] Preferably, in step 2, the sulfiding agent is sodium sulfide; and the stirring time is 1 to 2 hours.

[0027] Preferably, in step 3, the solid-liquid ratio of the solid to water is 1:5-10, and the unit of the solid-liquid ratio is mL / g; and the boiling time is 0.5-1 h.

[0028] Preferably, in step 4, the high-temperature calcination conditions are: a calcination temperature of 600-900° C., and a calcination time of 2-4 hours.

[0029] Preferably, in step 5, the mass ratio of the solid to the oxidant is 1:1 to 3; the conditions for the high-temperature calcination are: a calcination temperature of 700 to 950° C., and a calcination time of 2 to 4 hours.

[0030] Preferably, in step 6, the mixed acid is hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:3-5, and the mass ratio of the reaction product to nitric acid is 1:0.1-0.3; the conditions for the mixed acid leaching are: the leaching temperature is 80-100°C, and the leaching time is 0.5-2h.

[0031] Preferably, in step 7, the heating conditions are: heating temperature is 80-100° C., and heating time is 2-4 hours.

[0032] Preferably, in step 10, the amount of ammonium chloride added is 40 g / L to 60 g / L, and the heating conditions are: heating temperature is 80 to 100° C., and heating time is 2 to 8 hours.

[0033] Preferably, in step 11, the heating conditions are: heating temperature is 85-90° C., and heating time is 2-3 h.

[0034] Beneficial effects of the present invention:

[0035] 1. The present invention uses the process of sulfidation precipitation, boiling water impurity removal, high temperature roasting, alkali fusion roasting, mixed acid leaching, chemical precipitation, reduction dissolution, sulfidation impurity removal, oxidation precipitation, and aqua regia dissolution to recover trace iridium in waste liquid and prepare chloroiridic acid;

[0036] 2. The present invention ensures that the treated waste liquid is alkaline by adjusting the pH of the solution, thereby ensuring a high precipitation rate of iridium during sulfide precipitation and improving the recovery rate;

[0037] 3. The present invention uses a sulfiding agent to recover trace iridium in the solution through sulfidation precipitation, transferring ppm-level iridium in the liquid phase to the solid phase to obtain about 5% iridium-containing sulfide. The process is short in time and low in energy consumption, achieving efficient recovery of trace iridium in iridium-containing waste liquid, with high recovery rate, strong operability, easy large-scale processing, low auxiliary material cost, reduced iridium loss, and achieved cost reduction and efficiency improvement;

[0038] 4. The present invention uses boiling water to remove impurities and remove alkaline soluble substances entrained in the precipitation process, which reduces the workload of subsequent operations, is easy to operate, and has an obvious effect of removing alkaline soluble substances.

[0039] 5. The present invention converts iridium sulfide into iridium oxide by high-temperature roasting. Iridium oxide is easier to handle than iridium sulfide and improves the recovery rate of subsequent iridium treatment.

[0040] 6. The present invention activates iridium oxide by adding oxides, so that iridium exists in an easily soluble form, reducing the difficulty of processing;

[0041] 7. The present invention adopts mixed acid leaching to improve the leaching rate of activated iridium oxide. If the acid concentration is controlled, the number of repeated acid leaching is reduced, thereby improving operating efficiency;

[0042] 8. The present invention uses chemical precipitation to perform preliminary impurity removal and enrichment treatment on iridium in the solution, thereby improving recovery efficiency;

[0043] 9. The present invention is suitable for treating low-concentration complex iridium-containing solutions, has a high iridium enrichment rate, contains few impurity elements, and reduces environmental pollution. During the preparation process of the present invention, there is no need to add a large amount of expensive auxiliary materials, such as reducing agents and flocculants, thereby reducing production costs. The parameters of each process step are reasonable, and parameters such as the temperature, time, and material ratio of steps such as pH adjustment, sulfide precipitation, and high-temperature roasting are optimized. The operating steps are simple and the process is reasonable, which reduces the loss of iridium and improves the recovery rate of iridium. The entire process flow is highly operable, easy to scale up, and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0045] The following examples are provided to illustrate the present invention but are not intended to limit the scope of the invention. Unless otherwise specified, the reagents used are commercially available or prepared according to the prior art; and the operating methods used are conventional in the art unless otherwise specified.

[0046] A method for recovering trace iridium in a solution comprises the following steps:

[0047] Step 1, adjusting the pH of the solution: adjusting the pH of the iridium-containing waste liquid to greater than 12, heating the waste liquid at a temperature of 80 to 100° C. for 1.5 to 3 hours, and providing conditions for sulfide precipitation of iridium; wherein, sodium hydroxide solution is used to adjust the pH of the solution;

[0048] Step 2, sulfidation precipitation: heating the waste liquid treated in step 1 to boil, adding a sulfiding agent after boiling and stirring until no black precipitate is precipitated, stirring and reacting for 1 to 2 hours, cooling to room temperature and performing solid-liquid separation to obtain an iridium sulfide solid; wherein the sulfiding agent is a sodium sulfide solution;

[0049] Step 3, boiling water impurity removal: adding water to the iridium sulfide solid obtained in step 2 and boiling for 1 to 2 hours to remove impurities precipitated by sulfidation, and then performing solid-liquid separation to obtain an impurity-removed iridium sulfide solid; wherein the solid-liquid ratio of the solid to water is 1:5 to 10, and the unit of the solid-liquid ratio is mL / g;

[0050] Step 4, high-temperature calcination: drying the iridium sulfide solid obtained in step 3 after impurities are removed, and then calcining it in a muffle furnace at a high temperature of 600-900° C. for 2-4 hours;

[0051] Step 5, alkali fusion roasting: the solid obtained in step 4 is mixed with an oxidant in a mass ratio of 1:1 to 3, mixed and then roasted at a high temperature of 700 to 950° C. for 2 to 4 hours; the oxidant is sodium peroxide or sodium chlorate;

[0052] Step 6, mixed acid leaching: washing the reaction product obtained in step 5 with water and then performing mixed acid leaching, the leaching temperature is 80-100° C., the leaching time is 0.5-2 h, the mixed acid composition is hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:3-5, and the mass ratio of the reaction product to nitric acid is 1:0.1-0.3;

[0053] Step 7, chemical precipitation: the reaction product obtained in step 6 is subjected to solid-liquid separation, the separated solution is heated at a temperature of 80 to 100° C. for 2 to 4 hours, and then ammonium chloride is added for chemical precipitation; the amount of ammonium chloride added is adjusted until the color of the solution becomes lighter;

[0054] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, and then a reducing agent is added and heated at a temperature of 70 to 100° C. for a reduction time of 0.5 to 2 hours, and the volume ratio of the reducing agent to the slurried solution is 1:50 to 200; the reducing agent is any one of ammonium sulfide, sodium sulfide and hydrazine hydrate;

[0055] Step 9, sulfurization and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and a sulfurizing agent is added to the separated solution for sulfurization and impurity removal. The sulfurization temperature is 25-100° C., the sulfurization time is 0.5-24 hours, and the volume ratio of the sulfurizing agent to the solution is 1:20-100; the sulfurizing agent is ammonium sulfide or sodium sulfide;

[0056] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, an oxidant is added to the separated solution and heated at a temperature of 80 to 100° C. for 2 to 8 hours, and then 40 g / L to 60 g / L of ammonium chloride is added to precipitate for 0.8 to 1 hour, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide; the volume ratio of the oxidant to the solution is 1:10 to 50; the oxidant is any one of nitric acid, hydrogen peroxide and sodium chlorate;

[0057] Step 11, aqua regia dissolution: dissolving the iridium oxide solid obtained in step 10 in aqua regia and heating and concentrating it to obtain chloroiridic acid, the liquid-to-solid ratio of aqua regia to the solid is 3 to 8:1, the unit of the liquid-to-solid ratio is ml / g, the heating temperature is 85 to 90°C, and the heating time is 2 to 3 hours.

[0058] The present invention utilizes a sulfiding agent to recover trace iridium in a solution, transfers ppm-level iridium in a liquid phase to a solid phase to obtain about 5% iridium-containing sulfide. The process is short in time and has low energy consumption. Subsequently, impurity removal, melting, chemical precipitation and other processes are performed to prepare chloroiridic acid. This avoids the problems of direct evaporation of the solvent leading to the analysis of a large amount of salts and a low iridium enrichment rate, thereby effectively realizing the recovery of iridium and achieving cost reduction and efficiency improvement.

[0059] Example 1

[0060] A method for recovering trace iridium in a solution comprises the following steps:

[0061] Step 1, pH adjustment: add 1 L of waste liquid containing 200 ppm iridium to a reactor, slowly add sodium hydroxide solution to the reactor while stirring until the pH value of the waste liquid is greater than 12, heat the waste liquid with adjusted pH to 100° C., and keep warm for 1.5 hours;

[0062] Step 2, sulfide precipitation: heating the waste liquid treated in step 1 to boiling, slowly adding sodium sulfide solution to the boiling waste liquid until no black precipitate is precipitated, stirring the reaction for 1 hour, cooling to room temperature, filtering and separating the solid and liquid to obtain an iridium sulfide solid;

[0063] Step 3, removing impurities in boiling water: adding the solid obtained in step 2 to boiling water at a ratio of solid to water of 1:5, boiling for 1 hour, removing impurities precipitated by sulfidation, filtering and separating the solid and liquid, and obtaining a solid containing iridium sulfide after impurity removal;

[0064] Step 4, high-temperature calcination: drying the reaction product obtained in step 3 and calcining it in a muffle furnace at a temperature of 600° C. for 4 hours;

[0065] Step 5, alkali fusion roasting: the reaction product obtained in step 4 is mixed with sodium peroxide in a mass ratio of 1:1, and then roasted at a high temperature of 700°C for 4 hours;

[0066] Step 6, mixed acid leaching: the reaction product obtained in step 5 is washed with water and then subjected to mixed acid leaching, wherein the mixed acid composition comprises hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:3, the mass ratio of the reaction product to nitric acid is 1:0.1, the leaching temperature is 80° C., and the leaching time is 2 h;

[0067] Step 7, chemical precipitation: The reaction product obtained in step 6 is subjected to solid-liquid separation, and the separated solution is heated to 80° C. for 4 hours, and then ammonium chloride is added for chemical precipitation. The amount of ammonium chloride added is such that the color of the solution becomes lighter;

[0068] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, hydrazine hydrate is added, and the mixture is heated to 70° C. and reacted for 2 h. The volume ratio of hydrazine hydrate to the slurried solution is 1:50;

[0069] Step 9, sulfidation and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and the separated solution is added with sodium sulfide and reacted at 25°C for 24 hours to perform sulfidation and impurity removal, with the volume ratio of sodium sulfide to solution being 1:20;

[0070] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, and a nitric acid solution is added to the separated solution, with the volume ratio of the nitric acid solution to the reaction solution being 1:10, and the mixture is heated to 80° C. and stirred for oxidation for 8 h. 40 g / L ammonium chloride is then added, and the mixture is stirred and precipitated for 0.8 h. The solid and liquid are separated by filtration to obtain a solid containing iridium oxide;

[0071] Step 11, dissolving in aqua regia: dissolving the iridium oxide solid obtained in step 10 in aqua regia at a liquid-to-solid ratio of 8:1, heating to 90° C. and concentrating for 3 h to obtain chloroiridic acid.

[0072] Example 2

[0073] A method for recovering trace iridium in a solution comprises the following steps:

[0074] Step 1, pH adjustment: add 1 L of waste liquid containing 100 ppm iridium to a reactor, slowly add sodium hydroxide solution to the reactor while stirring until the pH value of the waste liquid is greater than 13, heat the waste liquid with adjusted pH to 90°C, and keep warm for 2 hours;

[0075] Step 2, sulfide precipitation: heating the waste liquid treated in step 1 to boiling, slowly adding sodium sulfide solution to the boiling waste liquid until no black precipitate is precipitated, stirring the reaction for 1.5 hours, cooling to room temperature, filtering and separating the solid and liquid to obtain an iridium sulfide solid;

[0076] Step 3, boiling water impurity removal: adding the solid obtained in step 2 to boiling water at a solid to water ratio of 1:7, boiling for 1.5 hours, removing impurities precipitated by sulfidation, filtering and separating the solid and liquid, and obtaining a solid containing iridium sulfide after impurity removal;

[0077] Step 4, high-temperature calcination: drying the reaction product obtained in step 3 and calcining it in a muffle furnace at a temperature of 700° C. for 3 h;

[0078] Step 5, alkali fusion roasting: the reaction product obtained in step 4 and sodium chlorate are mixed in a mass ratio of 1:1.5, and then roasted at a high temperature of 800° C. for 3 hours;

[0079] Step 6, mixed acid leaching: the reaction product obtained in step 5 is washed with water and then subjected to mixed acid leaching, wherein the mixed acid composition comprises hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:3.5, the mass ratio of the reaction product to nitric acid is 1:0.15, the leaching temperature is 85° C., and the leaching time is 1.5 h;

[0080] Step 7, chemical precipitation: The reaction product obtained in step 6 is subjected to solid-liquid separation, and the separated solution is heated to 85° C. for 3.5 hours, and then ammonium chloride is added for chemical precipitation. The amount of ammonium chloride added is such that the color of the solution becomes lighter;

[0081] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, ammonium sulfide is added, and the mixture is heated to 80° C. and reacted for 1.5 hours, with the volume ratio of ammonium sulfide to the slurried solution being 1:100;

[0082] Step 9, sulfidation and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and ammonium sulfide is added to the separated solution and reacted at 100° C. for 0.5 h to perform sulfidation and impurity removal, with the volume ratio of ammonium sulfide to the solution being 1:100;

[0083] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, and a hydrogen peroxide solution is added to the separated solution at a volume ratio of hydrogen peroxide solution to reaction solution of 1:30, heated to 90° C., stirred and oxidized for 4 hours, and then 50 g / L ammonium chloride is added, stirred and precipitated for 0.9 hours, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide;

[0084] Step 11, dissolving in aqua regia: dissolving the iridium oxide solid obtained in step 10 in aqua regia at a liquid-to-solid ratio of 6:1, heating to 85° C. and concentrating for 2.8 h to obtain chloroiridic acid.

[0085] Example 3

[0086] A method for recovering trace iridium in a solution comprises the following steps:

[0087] Step 1, pH adjustment: 2 L of waste liquid containing 200 ppm iridium was added to a reactor, and sodium hydroxide solution was slowly added to the reactor while stirring until the pH value of the waste liquid was greater than 13. The waste liquid with adjusted pH was heated to 80° C. and kept warm for 3 hours;

[0088] Step 2, sulfide precipitation: heating the waste liquid treated in step 1 to boiling, slowly adding sodium sulfide solution to the boiling waste liquid until no black precipitate is precipitated, stirring and reacting for 2 hours, cooling to room temperature, filtering and separating the solid and liquid to obtain an iridium sulfide solid;

[0089] Step 3, boiling water impurity removal: adding the solid obtained in step 2 to boiling water at a solid to water ratio of 1:10, boiling for 2 hours, removing impurities precipitated by sulfidation, filtering and separating the solid and liquid to obtain a solid containing iridium sulfide after impurity removal;

[0090] Step 4, high-temperature calcination: drying the reaction product obtained in step 3 and calcining it in a muffle furnace at a temperature of 800° C. for 2.5 h;

[0091] Step 5, alkali fusion roasting: the reaction product obtained in step 4 and sodium chlorate are mixed in a mass ratio of 1:2, and then roasted at a high temperature of 900° C. for 2.5 hours;

[0092] Step 6, mixed acid leaching: the reaction product obtained in step 5 is washed with water and then subjected to mixed acid leaching, wherein the mixed acid composition comprises hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:4, the mass ratio of the reaction product to nitric acid is 1:0.2, the leaching temperature is 90° C., and the leaching time is 1 h;

[0093] Step 7, chemical precipitation: The reaction product obtained in step 6 is subjected to solid-liquid separation, and the separated solution is heated to 90° C. for 3 hours, and then ammonium chloride is added for chemical precipitation. The amount of ammonium chloride added is such that the color of the solution becomes lighter;

[0094] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, sodium sulfide is added, and the mixture is heated to 90°C for 1 hour. The volume ratio of sodium sulfide to the slurried solution is 1:150;

[0095] Step 9, sulfurization and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, sodium sulfide is added to the separated solution, and the mixture is reacted at 80° C. for 2 hours to perform sulfurization and impurity removal, wherein the volume ratio of sodium sulfide to the solution is 1:50;

[0096] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, sodium chlorate is added to the separated solution, the volume ratio of sodium chlorate to the reaction solution is 1:40, the solution is heated to 100° C., stirred and oxidized for 2 hours, and then 60 g / L ammonium chloride is added, stirred and precipitated for 1 hour, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide;

[0097] Step 11, dissolving in aqua regia: dissolving the iridium oxide solid obtained in step 10 in aqua regia at a liquid-to-solid ratio of 4:1, heating to 87° C. and concentrating for 2.6 h to obtain chloroiridic acid.

[0098] Example 4

[0099] A method for recovering trace iridium in a solution comprises the following steps:

[0100] Step 1, pH adjustment: 2 L of waste liquid containing 100 ppm iridium was added to a reactor, and sodium hydroxide solution was slowly added to the reactor while stirring until the pH value of the waste liquid was greater than 12. The waste liquid with adjusted pH was heated to 85° C. and kept warm for 2.5 hours;

[0101] Step 2, sulfide precipitation: heating the waste liquid treated in step 1 to boiling, slowly adding sodium sulfide solution to the boiling waste liquid until no black precipitate is precipitated, stirring the reaction for 1.5 hours, cooling to room temperature, filtering and separating the solid and liquid to obtain an iridium sulfide solid;

[0102] Step 3, boiling water impurity removal: adding the solid obtained in step 2 to boiling water at a solid to water ratio of 1:8, boiling for 2 hours, removing impurities precipitated by sulfidation, filtering and separating the solid and liquid to obtain a solid containing iridium sulfide after impurity removal;

[0103] Step 4, high-temperature calcination: drying the reaction product obtained in step 3 and calcining it in a muffle furnace at a temperature of 900° C. for 2 h;

[0104] Step 5, alkali fusion roasting: the reaction product obtained in step 4 and sodium chlorate are mixed in a mass ratio of 1:3, and then roasted at a high temperature of 950° C. for 2 h;

[0105] Step 6, mixed acid leaching: the reaction product obtained in step 5 is washed with water and then subjected to mixed acid leaching, the mixed acid composition is hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:5, the mass ratio of the reaction product to nitric acid is 1:0.3, the leaching temperature is 100° C., and the leaching time is 0.5 h;

[0106] Step 7, chemical precipitation: The reaction product obtained in step 6 is subjected to solid-liquid separation, and the separated solution is heated to 100° C. for 2 hours, and then ammonium chloride is added for chemical precipitation. The amount of ammonium chloride added is such that the color of the solution becomes lighter;

[0107] Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, hydrazine hydrate is added, and the mixture is heated to 100° C. and reacted for 0.5 h, wherein the volume ratio of hydrazine hydrate to the slurried solution is 1:200;

[0108] Step 9, sulfidation and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and ammonium sulfide is added to the separated solution and reacted at 50° C. for 12 hours to perform sulfidation and impurity removal, with the volume ratio of ammonium sulfide to the solution being 1:30;

[0109] Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, nitric acid is added to the separated solution, the volume ratio of nitric acid to the reaction solution is 1:40, the solution is heated to 100° C., stirred and oxidized for 2 hours, and then 55 g / L ammonium chloride is added, stirred and precipitated for 1 hour, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide;

[0110] Step 11, dissolving in aqua regia: dissolving the iridium oxide solid obtained in step 10 in aqua regia at a liquid-to-solid ratio of 3:1, heating to 85° C. and concentrating for 2 h to obtain chloroiridic acid.

[0111] Comparative Example

[0112] Get 1L and contain the iridium-containing waste liquid of iridium 200ppm and place on heating furnace, heating evaporation is to solvent volatilization completely, a large amount of salt is had to analyze, oven dry back weight 300g, iridium content is only 0.067%, carry out melt roasting 2h after with 900g sodium peroxide batching, after the reaction, solid adds 10% hydrochloric acid and dissolves, filtrate heats and concentrates and adds 10ml nitric acid to be oxidized, after the oxidation, add ammonium chloride and carry out chemical precipitation, the gained solid adds hydrazine hydrate and reduces, remove by filter insoluble slag, filtrate adds ammonium sulfide and carries out sulfurization removal of impurities, remove by filter insoluble slag, filtrate is oxidized with nitric acid, after adding ammonium chloride and carry out chemical precipitation, obtain the ammonium chloroiridate solid, solid adds aqua regia and dissolves nitric acid to catch up with and obtain chloroiridic acid solution.

[0113] In summary, according to the comparison of the operating procedures of Examples 1 to 4 with the comparative example, it can be seen that the embodiments of the present invention control the amount of the added sulfiding agent, the sulfiding temperature and the sulfiding time during the sulfidation precipitation process to quickly achieve the enrichment of iridium in the iridium-containing waste liquid with a low iridium content, reduce the time-consuming solvent evaporation process and the problem that more impurities are precipitated after evaporation, and the obtained solid has a low iridium content; the present invention improves the recovery efficiency of iridium in the iridium-containing waste liquid with a low iridium content, has strong operability, a large waste liquid treatment capacity, and a small amount of auxiliary material consumption, reduces the loss of iridium, and significantly improves the recovery efficiency.

Claims

1. A method for recovering trace iridium in a solution, characterized in that, The following steps are involved: Step 1, adjusting the pH of the solution: adjusting the pH of the iridium-containing waste liquid to greater than 12, and then heating and keeping the waste liquid warm; Step 2, sulfidation precipitation: heating the waste liquid treated in step 1 to boil, adding a sulfiding agent after boiling and stirring until no black precipitate is precipitated, cooling to room temperature and performing solid-liquid separation to obtain an iridium sulfide solid; Step 3, removing impurities with boiling water: boiling the iridium sulfide solid obtained in step 2 with water to remove impurities, and then performing solid-liquid separation to obtain the iridium sulfide solid after impurities removal; Step 4, high-temperature calcination: drying the iridium sulfide solid obtained in step 3 after removing impurities, and then calcining it at high temperature; Step 5, alkali fusion roasting: adding an oxidant to the solid obtained in step 4 and roasting it at high temperature; the oxidant is sodium peroxide or sodium chlorate; Step 6, mixed acid leaching: washing the reaction product obtained in step 5 with water and then performing mixed acid leaching; Step 7, chemical precipitation: the reaction product obtained in step 6 is subjected to solid-liquid separation, the separated solution is heated, and then ammonium chloride is added for chemical precipitation; Step 8, reduction dissolution: the reaction product obtained in step 7 is subjected to solid-liquid separation, the separated solid is slurried with water, and then a reducing agent is added and heated; The volume ratio of the reducing agent to the slurried solution is 1:50 to 200; The reducing agent is any one of ammonium sulfide, sodium sulfide and hydrazine hydrate; Step 9, sulfurization and impurity removal: the reaction product obtained in step 8 is subjected to solid-liquid separation, and a sulfurizing agent is added to the separated solution to perform sulfurization and impurity removal; The volume ratio of the sulfiding agent to the solution is 1:20-100; The vulcanizing agent is ammonium sulfide or sodium sulfide; Step 10, oxidative precipitation: the reaction product obtained in step 9 is subjected to solid-liquid separation, an oxidant is added to the separated solution and heated, ammonium chloride is then added to precipitate, and the solid and liquid are separated by filtration to obtain a solid containing iridium oxide; The volume ratio of the oxidant to the solution is 1:10-50; The oxidant is any one of nitric acid, hydrogen peroxide and sodium chlorate; Step 11, aqua regia dissolution: dissolving the iridium oxide solid obtained in step 10 in aqua regia and heating and concentrating the solution to obtain chloroiridic acid; the liquid-to-solid ratio of the aqua regia to the solid is 3 to 8:1, and the unit of the liquid-to-solid ratio is ml / g.

2. The method for recovering trace iridium in the solution according to claim 1, wherein In step 1, sodium hydroxide solution is used to adjust the pH of the solution; the heating conditions are: heating temperature is 80-100° C., and heating time is 1.5-3 hours.

3. The method for recovering trace iridium in the solution according to claim 1, wherein In step 2, the sulfiding agent is sodium sulfide; and the stirring time is 1 to 2 hours.

4. The method for recovering trace iridium in the solution according to claim 1, wherein In step 3, the solid-liquid ratio of the solid to water is 1:5-10, and the unit of the solid-liquid ratio is mL / g; and the boiling time is 0.5-1 h.

5. The method for recovering trace iridium in the solution according to claim 1, wherein In step 4, the high-temperature calcination conditions are: calcination temperature is 600-900° C., and calcination time is 2-4 hours.

6. The method for recovering trace iridium in the solution according to claim 1, wherein In step 5, the mass ratio of the solid to the oxidant is 1:1-3; the conditions for the high-temperature calcination are: the calcination temperature is 700-950° C., and the calcination time is 2-4 hours.

7. The method for recovering trace iridium in the solution according to claim 1, wherein In step 6, the mixed acid is hydrochloric acid and nitric acid, the hydrochloric acid concentration is 10%, the mass ratio of the reaction product to hydrochloric acid is 1:3-5, and the mass ratio of the reaction product to nitric acid is 1:0.1-0.3; the conditions for the mixed acid leaching are: the leaching temperature is 80-100° C., and the leaching time is 0.5-2 h.

8. The method for recovering trace iridium in solution according to claim 1, wherein In step 7, the heating conditions are: heating temperature is 80-100° C., and heating time is 2-4 hours.

9. The method for recovering trace iridium in the solution according to claim 1, wherein In step 10, the amount of ammonium chloride added is 40 g / L to 60 g / L, and the heating conditions are: heating temperature is 80 to 100° C., and heating time is 2 to 8 hours.

10. The method for recovering trace iridium in solution according to claim 1, wherein In step 11, the heating conditions are: heating temperature is 85-90° C., and heating time is 2-3 h.

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