A method for recovering rhodium from rhodium-containing wastewater and recovered rhodium salt

Abstract

The present invention proposes a method for recovering rhodium from rhodium-containing wastewater and the recovered rhodium salt, and relates to the technical field of recovering rhodium. The method for recovering rhodium from rhodium-containing wastewater of the present invention comprises the following steps: concentrating the rhodium-containing wastewater, adding an acidulant to the concentrated rhodium-containing wastewater to adjust the pH value, and then heating and refluxing to obtain an acidified solution; adding a complexing agent to the acidified solution for reaction, filtering, and obtaining a rhodium-containing filtrate; adding a precipitant to the rhodium-containing filtrate for reaction, filtering, and obtaining a rhodium-containing filter cake; dissolving the rhodium-containing filter cake with acid A to obtain a rhodium salt solution; adding an alkali solution to adjust the pH value, causing a precipitation reaction, and post-processing to obtain rhodium hydroxide; dissolving the rhodium hydroxide with acid B to obtain a rhodium salt solution. The method for recovering rhodium from rhodium-containing wastewater of the present invention has a low rhodium loss rate, a rhodium recovery rate greater than 97.07%, and has the characteristics of simple process, strong selectivity, low cost, high recovery rate, etc.

Description

Technical Field

[0001] The invention relates to the technical field of rhodium recovery, and more particularly to a method for recovering rhodium from rhodium-containing waste water and the recovered rhodiumate. Background Art

[0002] Rhodium, as a very expensive precious metal, is widely used in the field of petrochemical industry, especially in the field of carbonyl synthesis of olefin hydroformylation reaction. The use of rhodium catalyst is very important and the demand is also large. Due to the high price of rhodium, a large amount of rhodium needs to be imported from abroad. Therefore, the domestic rhodium recovery work has significant economic and social benefits.

[0003] A large amount of rhodium-containing wastewater is produced during the carbonyl synthesis reaction and the recovery of waste rhodium catalyst residue. These rhodium-containing wastewaters usually have low rhodium content and many impurities, making them very difficult to treat.

[0004] At present, the treatment methods for precious metal wastewater in the world usually adopt physical and chemical methods, including ion exchange, precipitation, adsorption, etc. The ion exchange method is based on ion exchange to achieve the purpose of separating and recovering rhodium, and it is simple to operate and has a large processing capacity. Therefore, the ion exchange method is widely used in metal recovery. However, the resin used in the ion exchange method is expensive and difficult to regenerate, and it is also easy to produce new pollution.

[0005] The precipitation separation method can extract and recover rhodium by direct precipitation. This method has the characteristics of simple process and easy operation, but it requires controlled conditions to ensure the recovery rate and purity, and its application range is relatively narrow. Summary of the invention

[0006] In order to solve the problem of low rhodium recovery rate in the prior art, the present invention provides a method for recovering rhodium from rhodium-containing wastewater and the recovered rhodium salt. The method for recovering rhodium from rhodium-containing wastewater of the present invention has a low rhodium loss rate, a rhodium recovery rate of more than 97.07%, and has the characteristics of simple process, strong selectivity, low cost, high recovery rate, etc.

[0007] One of the objects of the present invention is to provide a method for recovering rhodium from rhodium-containing waste water, comprising the following steps:

[0008] (1) concentrating the rhodium-containing wastewater, adding an acidulant to the concentrated rhodium-containing wastewater to adjust the pH value, and then heating and refluxing to obtain an acidified solution;

[0009] (2) adding a complexing agent to the acidified solution for reaction, filtering, and obtaining a rhodium-containing filtrate;

[0010] (3) adding a precipitant to the rhodium-containing filtrate for reaction, filtering, and obtaining a rhodium-containing filter cake;

[0011] (4) dissolving the rhodium-containing filter cake with acid A to obtain a rhodium salt solution; adding an alkali solution to adjust the pH value, causing a precipitation reaction, and post-processing to obtain rhodium hydroxide;

[0012] (5) Dissolving the rhodium hydroxide with acid B to obtain a rhodiumate solution.

[0013] Preferably,

[0014] In step (1),

[0015] After the rhodium-containing wastewater is concentrated, the rhodium content is 2 to 3 g / L;

[0016] Concentration methods include distillation under reduced pressure.

[0017] Preferably,

[0018] In step (1),

[0019] The acidulant includes concentrated hydrochloric acid, and the acidulant is added until the pH value of the solution is ≤1.2, preferably the pH value is 1-1.2;

[0020] In the present invention, in step (1), there is no special requirement for the temperature and time of the heating reflux process, as long as the reaction in step (1) can be fully completed.

[0021] Preferably,

[0022] The heating reflux temperature is 80-100°C and the reflux time is 2-4 hours.

[0023] Preferably,

[0024] In step (2),

[0025] The complexing agent is selected from sodium nitrite solution;

[0026] The complexing agent is added to the acidified solution in a dropwise manner, and no new precipitation is generated after being added into the system.

[0027] Preferably,

[0028] In step (2),

[0029] The concentration of the sodium nitrite solution is 30wt% to 40wt%;

[0030] Before the complexing agent is added to the acidified solution, the pH value of the acidified solution must be maintained between 1 and 1.5;

[0031] In the present invention, if the pH value of the acidified solution in step (1) is 1-1.2, the complexing agent can be directly added at this time; if the pH value of the acidified solution in step (1) is less than 1, a little sodium hydroxide should be added before adding the complexing agent in step (2) to keep the pH value of the acidified solution between 1-1.5.

[0032] In the present invention, in step (2), there is no special requirement for the temperature and time of the heating reflux process, as long as the reaction in step (2) can be fully completed.

[0033] Preferably,

[0034] The reaction is carried out under heating reflux at a temperature of 80-100° C., and the heating is stopped when the pH value reaches 6-6.5.

[0035] Preferably,

[0036] In step (3),

[0037] The precipitant is selected from ammonium chloride;

[0038] The mass ratio of the precipitant to the rhodium element in the rhodium-containing filtrate is 2.1 to 3.5:1;

[0039] The reaction temperature is 18-25°C.

[0040] Preferably,

[0041] In step (4),

[0042] The acid A comprises concentrated hydrochloric acid and / or dilute sulfuric acid, and preferably the concentration of the dilute sulfuric acid is 10-30 wt %.

[0043] Preferably,

[0044] In step (4),

[0045] The alkali solution is selected from sodium hydroxide solution;

[0046] The concentration of the alkali solution is 20-30wt%;

[0047] Adjust pH to 8.5-9.5.

[0048] Preferably,

[0049] In step (5),

[0050] The acid B is selected from concentrated hydrochloric acid.

[0051] A second object of the present invention is to provide rhodium salts recovered by the method according to one of the objects of the present invention.

[0052] Compared with the traditional recycling method, the present invention has the following beneficial effects:

[0053] The method for recovering rhodium of the present invention can realize the recovery of rhodium ions in a targeted manner through the steps of adding a complexing agent and a precipitating agent, and has the characteristic of strong selectivity.

[0054] The method for recovering rhodium of the present invention is applied to the recovery of rhodium-containing wastewater and has the characteristics of simple process, strong selectivity, low cost, high recovery rate, etc.

[0055] The invention provides a method for recovering rhodium from rhodium-containing wastewater. First, the rhodium-containing wastewater is concentrated, acidified, heated and refluxed, and organic matter is removed. Then, a complexing agent is added for complexation and separation from other metals. Then, a precipitant is added for sedimentation and purification is performed to obtain a pure rhodium-containing solution. The method for recovering rhodium is simple to operate, high in efficiency, and has low rhodium loss, and a rhodium yield greater than 97.07%. DETAILED DESCRIPTION

[0056] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0057] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0058] The rhodium yield is calculated using the following formula:

[0059] Rhodium yield = (mass of chlororhodium acid solution × rhodium concentration) / (concentration of rhodium in rhodium-containing wastewater × mass of wastewater) × 100%

[0060] The rhodium concentration in the rhodium-containing solution was analyzed by ICP.

[0061] Example 1

[0062] The rhodium-containing wastewater was subjected to reduced pressure distillation and concentrated to a rhodium content of 2 g / L, concentrated hydrochloric acid was added to adjust the solution pH to 1, and the solution was heated under reflux for 2 hours at a reflux temperature of 90°C; an acidified solution was obtained, and a 40 wt% sodium nitrite solution was gradually added dropwise to the acidified solution under stirring conditions, and no new precipitation was generated when the solution was added to the system; the solution was reacted under stirring and reflux at a reflux temperature of 90°C, and the heating was stopped when the pH value reached 6.5, and the solution was cooled to room temperature and filtered. After filtering, the filter cake was washed, and the filtrate was combined to obtain a rhodium-containing filtrate; the rhodium-containing filtrate at 25°C was added to the solution. Add ammonium chloride powder (ammonium chloride: rhodium element mass ratio is 2.1:1), stir and then settle, filter to obtain a rhodium-containing filter cake, dissolve the rhodium-containing filter cake with concentrated hydrochloric acid until no nitrogen oxides are produced and completely dissolved to obtain a sodium chlororhodate solution, and drip a 20wt% sodium hydroxide solution into the sodium chlororhodate solution until the pH value is 9, stir until no new precipitation is produced, filter to obtain a rhodium hydroxide solid, wash the rhodium hydroxide solid with a large amount of deionized water to remove the sodium salt, and then dissolve the rhodium hydroxide with concentrated hydrochloric acid to obtain a rhodium chloride acid solution, and the rhodium recovery rate is 97.07%.

[0063] Example 2

[0064] The rhodium-containing wastewater is subjected to reduced pressure distillation to be concentrated to a rhodium content of 3 g / L, concentrated hydrochloric acid is added to adjust the solution pH to 1, and the solution is heated to reflux for 4 hours at a reflux temperature of 80° C. to obtain an acidified solution, and a 40 wt% sodium nitrite solution is gradually added dropwise to the acidified solution under stirring conditions, and the solution is reacted under stirring and reflux at a reflux temperature of 80° C. When the pH value reaches 6.5, the solution is heated to room temperature and filtered, and the filter cake is washed after filtering, and the filtrate is combined to obtain a rhodium-containing filtrate; ammonium chloride powder is added to the rhodium-containing filtrate at 20° C. (the mass ratio of ammonium chloride: rhodium element is 2.5:1), stirred and then settled, filtered to obtain a rhodium-containing filter cake, the rhodium-containing filter cake was dissolved with concentrated hydrochloric acid until no nitrogen oxides were produced and completely dissolved to obtain a sodium chlororhodate solution, a 25wt% sodium hydroxide solution was added dropwise to the sodium chlororhodate solution until the pH value was 9, stirred until no new precipitation was produced, filtered to obtain a rhodium hydroxide solid, washed the rhodium hydroxide solid with a large amount of deionized water to remove the sodium salt, and then the rhodium hydroxide was dissolved with concentrated hydrochloric acid to obtain a chlororhodium acid solution, and the rhodium recovery rate was 97.81%.

[0065] Example 3

[0066] The rhodium-containing waste water was subjected to reduced pressure distillation and concentrated to a rhodium content of 2.5 g / L in the rhodium-containing waste water. Concentrated hydrochloric acid was added to adjust the solution pH to 1.2, and the solution was heated to reflux for 3 hours at a reflux temperature of 90° C. Under stirring conditions, a 40wt% sodium nitrite solution was gradually added dropwise to the acidified solution, and the solution was reacted under stirring and reflux at a reflux temperature of 90° C. When the pH value reached 6.5, the solution was cooled to room temperature and filtered. After filtering, the filter cake was washed and the filtrate was combined to obtain a rhodium-containing filtrate. Ammonium chloride powder ( The method comprises the following steps: the first step is to add a 30wt% sodium hydroxide solution to the sodium chlororhodium acid solution, and the sodium chlororhodium acid solution is added dropwise to a 30wt% sodium hydroxide solution until the pH value is 9, and the mixture is stirred until no new precipitation is produced, and the mixture is filtered to obtain a rhodium hydroxide solid. The rhodium hydroxide solid is washed with a large amount of deionized water to remove the sodium salt, and the rhodium hydroxide is dissolved in concentrated hydrochloric acid to obtain a rhodium chloride acid solution. The rhodium recovery rate is 98.04%.

[0067] Example 4

[0068] The rhodium-containing wastewater was subjected to reduced pressure distillation to be concentrated to a rhodium content of 2 g / L, concentrated hydrochloric acid was added to adjust the solution pH to 1.2, heated to reflux for 2 hours, the heating reflux temperature was 100°C, and under stirring conditions, a 30wt% sodium nitrite solution was gradually added dropwise to the acidified solution, and the mixture was stirred and refluxed to react, and the heating reflux temperature was 100°C. When the pH value reached 6.5, the heating was stopped, the mixture was cooled to room temperature, and filtered. After filtering, the filter cake was washed, and the filtrate was combined to obtain a rhodium-containing filtrate; ammonium chloride powder was added to the rhodium-containing filtrate at 23°C. (the mass ratio of ammonium chloride: rhodium element is 3:1), stirred and then settled, filtered to obtain a rhodium-containing filter cake, the rhodium-containing filter cake was dissolved with concentrated hydrochloric acid until no nitrogen oxides were produced and completely dissolved to obtain a sodium chlororhodate solution, a 30wt% sodium hydroxide solution was added dropwise to the sodium chlororhodate solution until the pH value was 9, stirred until no new precipitation was produced, filtered to obtain a rhodium hydroxide solid, washed the rhodium hydroxide solid with a large amount of deionized water to remove the sodium salt, and then dissolved the rhodium hydroxide with concentrated hydrochloric acid to obtain a chlororhodium acid solution, with a rhodium recovery rate of 98.13%.

[0069] Example 5

[0070] The rhodium-containing wastewater was subjected to reduced pressure distillation to be concentrated to a rhodium content of 2.7 g / L, concentrated hydrochloric acid was added to adjust the solution pH to 1.1, heated to reflux for 3.5 hours, the heating reflux temperature was 90°C, and under stirring conditions, a 35wt% sodium nitrite solution was gradually added dropwise to the acidified solution, stirred and refluxed, and the heating reflux temperature was 90°C. When the pH value was 6.5, the heating was stopped, the solution was cooled to room temperature, and filtered. After filtering, the filter cake was washed, and the filtrate was combined to obtain a rhodium-containing filtrate; ammonium chloride powder was added to the rhodium-containing filtrate at 18°C. (the mass ratio of ammonium chloride: rhodium element is 3.5:1), stirred and then settled, filtered to obtain a rhodium-containing filter cake, the rhodium-containing filter cake was dissolved with concentrated hydrochloric acid until no nitrogen oxides were produced and completely dissolved to obtain a sodium chlororhodate solution, a 30wt% sodium hydroxide solution was added dropwise to the sodium chlororhodate solution until the pH value was 9, stirred until no new precipitation was produced, filtered to obtain a rhodium hydroxide solid, washed the rhodium hydroxide solid with a large amount of deionized water to remove the sodium salt, and then dissolved the rhodium hydroxide with concentrated hydrochloric acid to obtain a chlororhodium acid solution, with a rhodium recovery rate of 98.57%.

[0071] Example 6

[0072] The rhodium-containing waste water was subjected to reduced pressure distillation and concentrated to a rhodium content of 2.7 g / L in the rhodium-containing waste water. Concentrated hydrochloric acid was added to adjust the solution pH to 1.1, and the solution was heated to reflux for 3 hours at a reflux temperature of 95° C. Under stirring conditions, a 35wt% sodium nitrite solution was gradually added dropwise to the acidified solution, and the solution was reacted under stirring and reflux at a reflux temperature of 95° C. When the pH value was 6, the solution was cooled to room temperature and filtered. After filtering, the filter cake was washed and the filtrate was combined to obtain a rhodium-containing filtrate. Ammonium chloride powder (ammonium chloride: The method comprises the following steps: the first step is to add a 25wt% dilute sulfuric acid solution to the rhodium sulfate solution, and the first step is to add a 30wt% sodium hydroxide solution to the rhodium sulfate solution until the pH value reaches 9, and the solution is stirred until no new precipitation is generated, and the solution is filtered to obtain a rhodium hydroxide solid. The rhodium hydroxide solid is washed with a large amount of deionized water to remove the sodium salt, and the rhodium hydroxide is dissolved in concentrated hydrochloric acid to obtain a chlororhodium acid solution. The rhodium recovery rate is 97.42%.

[0073] Comparative Example 1

[0074] The preparation method is the same as that of Example 5, except that the step of concentrating the rhodium-containing wastewater is not included.

[0075] The rhodium recovery rate of the chlororhodium acid solution prepared by the above method is 90.14%.

[0076] Comparative Example 2

[0077] The preparation method is the same as that of Example 5, except that the rhodium-containing wastewater is concentrated until the rhodium content of the rhodium-containing wastewater is 4 g / L.

[0078] The rhodium recovery rate of the chlororhodium acid solution prepared by the above method is 94.32%.

[0079] Comparative Example 3

[0080] The preparation method is the same as that of Example 5, except that concentrated hydrochloric acid is added to the concentrated rhodium-containing wastewater to adjust the pH of the solution to 2, and a sodium nitrite solution of the same concentration as that of Example 5 is directly added dropwise after refluxing under the condition of pH 2.

[0081] The rhodium recovery rate of the chlororhodium acid solution prepared by the above method is 95.77%.

[0082] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for recovering rhodium from rhodium-containing wastewater, characterized in that, The following steps are involved: (1) concentrating the rhodium-containing wastewater by vacuum distillation, wherein the rhodium content of the rhodium-containing wastewater after concentration is 2 to 3 g / L; adding an acidulant to the concentrated rhodium-containing wastewater until the pH value of the solution is 1 to 1.2, and then heating and refluxing to obtain an acidified solution; (2) adding a complexing agent to the acidified solution for reaction, filtering, and obtaining a rhodium-containing filtrate; the complexing agent is selected from a sodium nitrite solution; before the complexing agent is added to the acidified solution, the pH value of the acidified solution needs to be maintained between 1 and 1.5; (3) adding a precipitant to the rhodium-containing filtrate for reaction, filtering, and obtaining a rhodium-containing filter cake; (4) dissolving the rhodium-containing filter cake with acid A to obtain a rhodium salt solution; adding an alkali solution to adjust the pH value, causing a precipitation reaction, and post-processing to obtain rhodium hydroxide; (5) Dissolving the rhodium hydroxide with acid B to obtain a rhodiumate solution.

2. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (1), The acidulant includes concentrated hydrochloric acid; The heating reflux temperature is 80-100°C and the reflux time is 2-4 hours.

3. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (2), The complexing agent is added to the acidified solution in a dropwise manner, and no new precipitation is generated after being added into the system.

4. The method for recovering rhodium from rhodium-containing waste water according to claim 3, wherein In step (2), The concentration of the sodium nitrite solution is 30wt% to 40wt%; The reaction is carried out under heating reflux at a temperature of 80-100° C., and the heating is stopped when the pH value reaches 6-6.

5.

5. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (3), The precipitant is selected from ammonium chloride; The mass ratio of the precipitant to the rhodium element in the rhodium-containing filtrate is 2.1 to 3.5:1; The reaction temperature is 18-25°C.

6. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (4), The acid A includes concentrated hydrochloric acid and / or dilute sulfuric acid.

7. The method for recovering rhodium from rhodium-containing waste water according to claim 6, wherein The concentration of dilute sulfuric acid is 10-30 wt%.

8. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (4), The alkali solution is selected from sodium hydroxide solution; The concentration of the alkali solution is 20-30wt%; Adjust pH to 8.5-9.

5.

9. The method for recovering rhodium from rhodium-containing waste water according to claim 1, wherein In step (5), The acid B is selected from concentrated hydrochloric acid.