Method for extracting rhodium from organic rhodium-containing liquid
Technical Field
The invention relates to a method for extracting noble metal, in particular to a method for extracting rhodium from liquid containing organic rhodium.
Background
The rhodium homogeneous catalyst has unique catalyst activity and selectivity, and is widely used in hydrogenation, olefin hydroformylation and other reactions in organic chemical industry. The rhodium-containing waste liquid is inevitably generated in the process of producing and using the rhodium catalyst. The price of rhodium is expensive, the price of rhodium in 2021 is more than 700 ten thousand yuan/kg, and the price of rhodium in 2022 is always maintained to be more than 400 ten thousand yuan/kg. Therefore, the efficient recovery of rhodium from the waste stream has important economic value.
There are many ways of recovering rhodium from waste streams, including pyrogenic and wet processes in general. Most of the pyrogenic processes adopt the concentration, incineration and rhodium refining of waste liquid, so that the pollution is large, the energy consumption is high, and the rhodium loss is serious in the incineration process; the wet process comprises precipitating rhodium from the waste solution with a precipitant and refining. There is also a literature report on the direct reduction of rhodium from organic waste streams using hydrazine hydrate reducing agents. Generally, when the carbon chain of the rhodium organic matter in the waste liquid is more than 2, the rhodium in the waste liquid cannot be completely reduced by hydrazine hydrate, and the loss of the rhodium is huge.
Specifically, the current methods for recovering rhodium from waste streams include:
(1) Chinese patent CN 111020220A discloses a method for recovering rhodium from rhodium-containing waste liquid, which comprises the steps of concentrating the rhodium-containing waste liquid to evaporate light components, mixing wood dust, carrying out primary incineration on the rhodium-containing waste liquid concentrated solution, burning into rhodium-containing carbon residue, and then carrying out acid pickling and water washing; then the carbon slag containing rhodium is incinerated for the second time to be fired into rhodium-containing ash slag, and then acid washing, water washing, alkali washing and water washing are carried out, so that acid-soluble and alkali-soluble impurities can be completely removed; in the primary incineration and the secondary incineration processes, the flue gas passes through a wet dust collector and a cyclone dust collector, so that dust in the flue gas can be collected, the direct emission of the flue gas is avoided, the environment pollution is avoided, and the rhodium loss in the incineration process is reduced; and mixing the dust and the incineration residues, reacting with alkali metal acid sulfate to generate soluble rhodium salt, and reacting the soluble rhodium salt with active metal to obtain rhodium. The liquid containing organic rhodium has large burning loss, although the smoke dust can collect the rhodium, the environmental protection is difficult to reach the standard, and the required equipment investment is large;
(2) Chinese patent CN110607448A discloses a method for recovering rhodium from organic rhodium-containing liquid to prepare rhodium trichloride, which comprises the following steps: 1. adsorbing rhodium in organic rhodium-containing liquid generated in the production process of the rhodium homogeneous catalyst on an adsorbent in a dynamic adsorption mode by adopting a high-molecular adsorbent; 2. putting a rhodium-containing adsorbent into an acid solvent, adding a certain amount of stannous chloride, refluxing and stirring, transferring rhodium from the adsorbent into a solution, and filtering to obtain a rhodium-containing aqueous phase solution; 3. purifying; 4. evaporating and concentrating to obtain rhodium trichloride. At present, the application of the adsorbent is mostly used for treating organic wastewater and wastewater containing heavy metals or noble metal wastewater, the main purpose is that the discharged wastewater is environmentally friendly and reaches the standard, and a sample provided by a trial adsorbent manufacturer is used for carrying out a noble metal wastewater adsorption experiment to find that the noble metals cannot be completely adsorbed, the adsorption effect is not ideal, and the discharge standard of the noble metal wastewater cannot be reached;
(3) Chinese patent CN110964910A discloses a method for recovering rhodium from rhodium catalyst waste liquid, comprising: s1, carrying out incineration treatment on rhodium catalyst waste liquid to obtain rhodium ash; s2, dissolving the rhodium ash by using a hydrochloric acid solution to obtain a rhodium-containing acid solution; and S3, treating the rhodium-containing acid solution by using LX-110 cation exchange resin and LSD-396 cation exchange resin to obtain an exchange solution containing rhodium chloride. The acidity of the dissolved acid solution containing rhodium is very high, and the specific LX-110 and LSD-396 cation resin are connected in series, so that iron, nickel and other base metal ions can be more effectively removed, and the recovery of rhodium is realized. However, in the actual production operation, rhodium is difficult to dissolve and difficult to further refine by hydrochloric acid after being incinerated;
(4) Chinese patent CN105944768A provides a method for recovering rhodium catalyst from rhodium-containing waste water phase. The method comprises the following steps: 1. acidizing; 2. extracting; 3. layering; 4. washing with water; 5. generation of a catalyst; 6. the extraction solvent is used indiscriminately. The method can directly obtain the water phase catalyst with complete catalytic capability without a complex process by recovering the rhodium catalyst from the rhodium-containing wastewater phase, and has the advantages of simple operation and high efficiency of recovering the rhodium catalyst. The phosphate is generally used for separating other precious metals from rhodium, the other precious metals are extracted into an organic phase by the phosphate, and the rhodium is difficult to extract and remains in an aqueous phase, so that the rhodium is separated from the other precious metals;
(5) The invention of Chinese patent CN102557155A is a method for recovering rhodium from rhodium-containing waste liquid to prepare rhodium trichloride hydrate, which adopts hydrazine hydrate solution to treat rhodium-containing reaction waste liquid for preparing rhodium homogeneous complex catalyst, and rhodium contained in the reaction waste liquid is precipitated, filtered and washed, and the precipitate is dissolved by hydrochloric acid and hydrogen peroxide to obtain the common raw material rhodium trichloride hydrate for preparing rhodium homogeneous complex catalyst. In the actual production process, the hydrazine hydrate directly reduces rhodium in the organic waste liquid and is difficult to completely reduce, and the organic rhodium-containing liquid with longer carbon chain and more complex components is difficult to reduce;
(6) In the document "precious metals" Nov 2018 Vol39 No. s1, the authors add sodium sulfide to the organic waste liquid to precipitate rhodium, and the final recovery rate of rhodium is over 80%. The valence state of rhodium aimed at by the method is 3, and actually in an organic system, rhodium is difficult to maintain 3 and difficult to form Rh under the condition of strong oxidizing property 2 S 3 Precipitating;
(7) In the literature, "nonferrous metals (smelting sector)" 2018, (09) "recovery of rhodium from rhodium-containing solutions by EDTA precipitation", the authors added EDTA to precipitate rhodium by adjusting the PH of the solution, followed by washing, calcination, and reduction with hydrogen to obtain pure rhodium powder. The method is mainly aimed at the recovery of rhodium-containing solution of inorganic system.
Disclosure of Invention
In order to overcome the defects of the method, the invention provides a method for extracting rhodium from an organic rhodium-containing liquid, which comprises the following steps:
step 1, preparing an alkaline solution with a certain concentration, mixing an organic rhodium-containing liquid and the alkaline solution according to a certain volume ratio, and heating to 70-120 ℃;
step 2, slowly adding a certain amount of reducing agent into the solution formed by mixing in the step 1 in batches, boiling for more than 1h after the reducing agent is added, cooling to room temperature, filtering and separating to obtain crude rhodium powder, and washing the crude rhodium powder for later use;
and 3, introducing hydrogen into the crude rhodium powder washed in the step 2 at 500-850 ℃ for reduction for 1-3h, then boiling the crude rhodium powder in aqua regia and hydrofluoric acid respectively, washing with water to remove acid, and drying to obtain pure rhodium powder.
The organic rhodium-containing liquid is waste liquid generated in the production or use process of rhodium acetate, rhodium acetylacetonate, rhodium octoate, rhodium (ethylene) chloride, rhodium park and other carboxylic acid rhodium salts, ketone rhodium salts, alkane rhodium salts and olefin rhodium salts.
Further, the alkaline solution comprises any one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate or sodium formate. The reducing agent comprises any one or more of formic acid, hydrazine hydrate, sodium borohydride or sodium formaldehyde sulfoxylate.
Further, the volume ratio of the organic rhodium-containing liquid to the alkaline solution is 1:0.2-5.
Further, in step 2, the reducing agent is added in an amount of 1:0.3 is added.
Preferably, in step 3, the temperature for hydrogen introduction reduction is 750 ℃, and the time for hydrogen introduction reduction is 3h.
Further, before step 1, the organic rhodium-containing liquid is concentrated under reduced pressure until the content of rhodium is more than 1wt.%.
Further, the concentration of the alkaline solution with a certain concentration is in a range of 5% -50%, and the purpose of the alkaline solution is to adjust the solution to be strong alkaline so as to promote the reaction of the organic matter and the strong alkali.
The reaction mechanism and the reaction process of the invention are as follows:
1) The carboxylic acid and the alkali are subjected to neutralization reaction; RCOOH + NaOH → RCOONa + H 2 O
2) The reaction of esters with alkali is also known as saponification; RCOOR '+ NaOH → RCOONa + R' OH
In an organic medium, under the strong alkaline condition, the coordination force of chemical bonds of the organic matters and the rhodium can be weakened, so that the rhodium can be easily reduced from the organic matters under the strong alkaline condition.
Compared with the prior method for recovering rhodium from the liquid containing organic rhodium, the method has the beneficial effects that:
(1) And no toxic, sensitive and difficult-to-operate reagent is used in the whole recovery process. Because high temperature is not used, the malodorous dioxin can not be generated, and the environment can not be polluted. The operating conditions are easy to implement and there are no harsh reaction conditions such as temperature, pressure, concentration, time, and the like.
(2) The method has the advantages of high recovery rate, good stability, low cost, no special equipment requirement and strong practicability, and meets the industrial production requirement.
(3) The recovery method has mild reaction conditions and good safety, the recovery rate is more than or equal to 95 percent, and the recovered rhodium powder has high purity (the purity is more than 99 percent).
Therefore, the method for recovering rhodium provided by the invention aims at rhodium-containing complex waste liquid (the waste liquid contains a large amount of carboxylic acid, ketone, olefin, N-N dimethylformamide, alkane, alcohol and the like) generated in the production or use process of the rhodium salt of carboxylic acid, the rhodium salt of alkane, and the rhodium salt of alkene and ketone, and has the advantages of simple process, low energy consumption, environmental protection, high recovery rate and the like.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
Example 1
As shown in fig. 1, the method of the present invention comprises:
300mL of waste liquid generated in the synthesis process of rhodium caprylate is taken, wherein the content of rhodium in the waste liquid is 2 percent, and the main components of the waste liquid are water, sodium caprylate, caprylic acid and ethanol. 300mL of 30% sodium hydroxide solution was added to a 5000mL three-necked glass bottle, and the above concentrate was added with stirring and heated to 100 ℃. Adding 90mL of hydrazine hydrate (CP) firstly, enabling the solution to react violently, adding hydrazine hydrate in batches after the reaction is slightly calm, continuously separating out crude rhodium until 100mL of hydrazine hydrate is added, boiling for 1h, filtering and separating, washing rhodium powder with deionized water, drying, placing in a hydrogen reduction furnace at 750 ℃, then carrying out hydrogen for 3h, and then boiling in aqua regia and hydrofluoric acid to obtain 5.88 g of rhodium powder, wherein the recovery rate is 98%, and the purity of the rhodium powder is 99.95%.
Example 2
As shown in fig. 1, the method of the present invention comprises:
taking 10L of waste liquid generated in the synthesis process of rhodium acetylacetonate, wherein the content of rhodium in the waste liquid is 0.7 percent, and the main components of the waste liquid are water, acetylacetone and dilute nitric acid, and firstly carrying out reduced pressure concentration to 1L by using a rotary evaporator. Adding 1L of 20% sodium hydroxide solution into a 10L three-mouth glass bottle, adding the concentrated solution while stirring, heating to 100 ℃, slowly adding 300ml of hydrazine hydrate, adding the hydrazine hydrate in batches, enabling the solution to react violently when the hydrazine hydrate is added, gradually adding the hydrazine hydrate after the reduction reaction is slightly calm, boiling for 1h after the hydrazine hydrate is added, separating out crude rhodium powder, filtering and separating, washing the rhodium powder with deionized water, drying, putting the rhodium powder into a hydrogen reduction furnace, introducing hydrogen for 3h at 750 ℃, boiling in aqua regia and hydrofluoric acid to obtain 67.5 g of rhodium powder, wherein the recovery rate is 98.4%, and the purity of the rhodium powder is 99.95%.
Example 3
As shown in fig. 1, the method of the present invention comprises:
taking 50L of waste liquid generated in the synthesis process of acetylacetonatodicarbonylrhodium, wherein the waste liquid contains 0.1 percent of rhodium and comprises the main components of water, N-N dimethylformamide, acetylacetone, isopropanol and petroleum ether. Concentrate to 5L under reduced pressure using a rotary evaporator. Adding 5L of 30% sodium hydroxide solution into a 20L three-mouth glass bottle, adding 5L of the concentrated solution under stirring, heating to 100 ℃, slowly adding 1.5L of hydrazine hydrate, enabling the solution to react violently, adding the hydrazine hydrate in batches, gradually adding the hydrazine hydrate after the reduction reaction is slightly calm, boiling for 1h after the hydrazine hydrate is added, separating out crude rhodium powder, filtering and separating, washing the rhodium powder with deionized water, drying, putting into a hydrogen reduction furnace, introducing hydrogen for 3h at 750 ℃, boiling in aqua regia and hydrofluoric acid to obtain 47.3 g of rhodium powder, wherein the recovery rate is 96.5%, and the purity of the rhodium powder is 99.95%.
Example 4
As shown in fig. 1, the method of the present invention comprises:
taking 100L of rhodium-containing waste liquid generated by rhodium acetate synthesis reaction, wherein the waste liquid contains 0.6% of rhodium and comprises the main components of water, acetic acid and sodium acetate, and concentrating the waste liquid to 10L by using a rotary evaporator. Adding 10L of 30% sodium hydroxide solution into a 50L glass reaction kettle, adding 10L of the concentrated solution under stirring, heating to 100 ℃, slowly adding 3L of hydrazine hydrate, enabling the solution to react violently, adding hydrazine hydrate for multiple times to prevent overflowing, boiling for 1.5 hours after adding, separating out crude rhodium powder, filtering and separating, washing the rhodium powder with deionized water, drying, putting into a hydrogen reduction furnace, introducing hydrogen for 3 hours at 750 ℃, then boiling aqua regia and hydrofluoric acid to obtain 564 g of rhodium powder, wherein the recovery rate is 96%, and the purity of the rhodium powder is 99.9%.
Example 5
As shown in fig. 1, the method of the present invention comprises:
taking 200L of waste liquid generated by the synthesis reaction of rhodium park, wherein the waste liquid contains 0.16% of rhodium and comprises the main components of water, N-N dimethylformamide, acetylacetone, isopropanol and petroleum ether, and concentrating to 20L by using a concentration kettle. Adding 20L of 30% sodium hydroxide solution into a 100L jacketed reaction kettle, adding 20L of the concentrated solution under stirring, heating to 100 ℃, slowly adding 6L of hydrazine hydrate, enabling the solution to react violently, adding hydrazine hydrate in batches to prevent overflowing, boiling for 2h after adding, separating out crude rhodium powder, filtering and separating, washing the rhodium powder with deionized water, drying, placing in a hydrogen reduction furnace, introducing hydrogen at 750 ℃ for 3h, and boiling with aqua regia and hydrofluoric acid to obtain 297.9 g of rhodium powder, wherein the recovery rate is 95%, and the purity of the rhodium powder is 99.9%.