阅读说明：本技术 一种废旧铂铑热电偶的常温氯化溶解处理方法 (Normal-temperature chlorination and dissolution treatment method for waste platinum-rhodium thermocouples ) 是由 罗凤兰 吴保安 秦钊 王丹 冉义斌 唐会毅 梁源玲 王云春 于 2020-12-02 设计创作，主要内容包括：本发明涉及化学工程领域,具体涉及一种废旧铂铑热电偶的常温氯化溶解处理方法,包括以下步骤：1)制备铁基离子液；2)在常温下氯化溶解废旧铂铑热电偶；3)纯化分离单质铑、单质铂。本发明在常温下利用Cl-2的氧化作用和所产生的次氯酸使铂铑合金物料溶解,并以1-丁基-3-甲基氯代咪唑和六水合三氯化铁合成铁基离子液富集铂铑离子加速溶解铂铑合金物料,只需要搅拌均匀即可富集回收铂铑,不需要高温条件,从而节约能耗,降低工艺成本,实现废旧铂铑合金的回收无害化和资源化处理,且经本发明处理的废旧热电偶,达到直收率98％以上,符合我国倡导的可持续发展之路,也符合当今世界的时代主题。(The invention relates to the field of chemical engineering, in particular to a normal-temperature chlorination and dissolution treatment method of waste platinum-rhodium thermocouples, which comprises the following steps: 1) preparing iron-based ionic liquid; 2) chloridizing and dissolving the waste platinum-rhodium thermocouple at normal temperature; 3) and purifying and separating the simple substance rhodium and the simple substance platinum. The invention utilizes Cl at normal temperature 2 The oxidation of the catalyst and the generated hypochlorous acid dissolve platinum-rhodium alloy materials, 1-butyl-3-methyl chloroimidazole and ferric chloride hexahydrate are used for synthesizing iron-based ionic liquid to enrich platinum and rhodium ions and accelerate the dissolution of the platinum-rhodium alloy materials, the platinum and rhodium can be enriched and recovered only by uniformly stirring, and high-temperature conditions are not needed, so that the energy consumption is saved, the process cost is reduced, the harmless and recycling treatment of the waste platinum-rhodium alloy is realized, the waste thermocouple treated by the method can reach the direct yield of more than 98 percent, the method accords with sustainable development roads advocated by China and the era theme of the world at present.)

1. A normal-temperature chlorination and dissolution treatment method of waste platinum-rhodium thermocouples is characterized by comprising the following steps:

1) preparing an iron-based ionic liquid:

1-1) Synthesis of 1-butyl-3-methylchloroimidazole solution:

uniformly mixing N-methylimidazole and N-butyl chloride according to the molar ratio of 1:1, and fully reacting to obtain a 1-butyl-3-methylimidazole chloride solution; :

1-2) synthesis of iron-based ionic liquid:

mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂Mixing O uniformly according to a molar ratio of 1:2, fully reacting, and standing for liquid separation to obtain an iron-based ionic liquid;

2) chloridizing and dissolving the waste platinum-rhodium thermocouple at normal temperature:

2-1) uniformly mixing the iron-based ionic liquid and hydrochloric acid to obtain a mixed solution, wherein the volume ratio of the iron-based ionic liquid to the hydrochloric acid in the mixed solution is 2-4: 15-20;

2-2) putting crushed waste platinum-rhodium thermocouple particles into the mixed solution to be submerged, continuously introducing chlorine into the mixed solution, and stirring the mixed solution;

2-3) carrying out sampling detection analysis on the mixed solution for multiple times, stopping introducing chlorine when the contents of platinum ions and rhodium ions in the mixed solution are not less than 98%, and stopping stirring;

3) purifying and separating simple substance rhodium and simple substance platinum:

adding NaOH into a mixed solution with the contents of platinum ions and rhodium ions being more than or equal to 98 percent for precipitating rhodium, purifying and separating simple substance rhodium, taking out the simple substance rhodium, and adding NH into the mixed solution₄And precipitating the platinum by using Cl, purifying and separating the simple substance platinum, and taking out the simple substance platinum.

2. The method of claim 1, wherein: in the step 1-1), impurities in the 1-butyl-3-methyl imidazole chloride solution are removed by adopting an impurity removal method.

3. The method of claim 2, wherein: the impurity removal method adopts the following steps to remove impurities in the 1-butyl-3-methyl imidazole chloride solution in the step 1-1):

adding ethyl acetate into the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1), placing the solution in a rotary evaporator, setting the operating temperature to be 70 ℃, evaporating and removing the ethyl acetate in the 1-butyl-3-methyl imidazole chloride solution, and then placing the 1-butyl-3-methyl imidazole chloride solution in a vacuum drying oven at 70 ℃ for drying.

4. The method of claim 1, wherein: in the step 1-1), the N-methylimidazole and N-butyl chloride are fully reacted by adopting the following method: under the condition of room temperature, uniformly mixing N-methylimidazole and N-butane chloride according to the molar ratio of 1:1, putting the mixture into a constant-temperature magnetic stirrer, and continuously stirring for at least 72 hours, wherein the temperature in the constant-temperature magnetic stirrer is 65-75 ℃.

5. The method of claim 1, wherein: in the step 1-2), the 1-butyl-3-methyl imidazole chloride solution and FeCl are mixed by the following method₃·6H₂And (3) fully reacting O: under the condition of room temperature, 1-butyl-3-methyl imidazole chloride solution and FeCl₃·6H₂And (3) uniformly mixing the O according to the molar ratio of 1:2, placing the mixture into a constant-temperature stirrer, and setting the reaction temperature to be 70 ℃ to continuously stir and react for 24 hours.

6. The method of claim 1, wherein: the iron-based ionic liquid is obtained by adopting the following steps of standing and liquid separation in the step 1-2): mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂And O is uniformly mixed according to the molar ratio of 1:2 and fully reacted, then the mixture is put into a separating funnel and stands until the solution is separated into two phases, and after the liquid at the lower layer is drained from the lower port of the separating funnel, the dark green liquid at the upper layer, namely the iron-based ionic liquid, is collected from the upper port.

7. The method of claim 1, wherein: and 2) washing the waste platinum-rhodium thermocouple with ethanol and deionized water before crushing.

8. The method of claim 1, wherein: the structural formula of the iron-based ionic liquid is as follows:

9. the method of claim 1, wherein: the concentration of the hydrochloric acid in the step 2-1) is 4-14 mol/L.

10. The method of claim 1, wherein: the concentration of the iron-based ionic liquid in the step 2-1) is 2-8 mol/L.

Technical Field

The invention relates to the field of chemical engineering, in particular to a normal-temperature chlorination and dissolution treatment method of waste platinum-rhodium thermocouples.

Background

Along with the development of temperature measurement technology, the performance of measuring instruments and measuring systems is continuously improved, and the requirements on temperature measurement precision and accuracy are more and more strict. The thermocouple can directly convert temperature into electric quantity during temperature measurement, is particularly suitable for automatic adjustment and automatic control of temperature, and is widely applied to medium temperatures of gas, liquid, steam and the like at minus 200-2500 ℃. In large-scale temperature measurement, thermocouples are widely used in industries of power plants, manufacturing enterprises, scientific research institutions and other departments due to their small size, high sensitivity and stable output signals.

At present, a low-cost K-type nickel-chromium thermocouple is generally adopted for measuring high temperature, but the measurement can be stably carried out for a long time only at the temperature below 700 ℃, and the service life is shortened or even damaged sharply due to oxidation in the temperature environment above 700 ℃ for a long time; if the temperature above 1000 ℃ needs to be measured stably for a long time, only the thermocouple made of the platinum-rhodium precious metal material with high cost can be adopted. Thermocouples made of noble metals such as platinum group and alloys thereof are called noble metal thermocouples, and have many advantages such as wide temperature measurement range (0-1800 ℃), high measurement accuracy, sensitive temperature change, long service life, and the like, compared with inexpensive metal thermocouples. The platinum-rhodium alloy has the excellent characteristics of good catalytic activity, stable thermoelectric property, good creep resistance, high-temperature endurance strength, good corrosion resistance, strong high-temperature oxidation resistance and the like, so that the platinum-rhodium alloy is widely applied to the fields of thermocouples and the like. Because the platinum-rhodium precious metal has excellent performance and wide application prospect, under the background of extremely deficient platinum-group metal resources, the dissolution and recovery of waste platinum-rhodium alloy arouses the interest of a plurality of foreign researchers, and develops a plurality of new recovery methods and new technologies.

At present, the enrichment of platinum group metals mainly comprises two processes, namely a fire process and a wet process. The pyrogenic process comprises plasma smelting, metal trapping, dry chlorination and other technologies; the wet process is carried out by carrier dissolving method, active component dissolving method, full dissolving method and pressure cyaniding method. As the pyrometallurgical process has the defects of high energy consumption, long production period, difficult post-treatment of part of generated slag, large investment and the like, the wet process is generally adopted in industry to dissolve platinum group metals.

The waste platinum-rhodium thermocouples are generally dissolved and recovered directly by an active component dissolving method, wherein the active component dissolving method mainly comprises an aqueous solution chlorination dissolving method and an electrochemical dissolving method. Because the electrochemical dissolution method has low dissolution speed and complex operation and is less applied to the industry, the aqueous solution chlorination dissolution method is mainly adopted to dissolve the platinum-rhodium alloy. The aqueous solution chlorination dissolving method comprises HCl-HNO₃、HCl-Cl₂、HCl-NaClO₃The constant-strength acid oxidation system is widely applied to the present time and is HCl-HNO₃And (5) processing.

HCl-HNO₃The process can have a good dissolving effect on the platinum-rhodium alloy, but has the defects of long dissolving period, need of heating to a certain temperature, insoluble slag generation when the rhodium content in the platinum-rhodium alloy is more than 5 percent and the like, so related researchers in HCl-HNO₃The process is improved, for example, aluminum is added under the condition of high temperature for alloying activation, and then aqua regia is used for dissolution, thereby improving the dissolution rate of rhodium; or by reaction in HCl-HNO₃In the process, H is added₂O₂And heated to boiling to enhance the dissolution of rhodium. The HCl-HNO after the above improvement₃Although the process can better dissolve the platinum-rhodium alloy, the process needs to be carried out at higher temperature, and NO which is difficult to treat is generated_xPollutants and subsequent complex operations such as denitration and the like cannot achieve the purposes of energy conservation and environmental protection. HCl-NaClO₃The process is also related to reports, or HCl-NaClO is adopted₃The process recovers platinum and palladium from silver electrolysis anode mud, or adopts HCl-NaClO₃Rhodium powder is dissolved in the four processes, and although the dissolution effects are good, the rhodium powder is dissolved in the four processesHigh-temperature heating is needed, the energy consumption is serious, the process cost is increased, an energy-saving and environment-friendly process capable of efficiently dissolving the platinum-rhodium alloy at normal temperature is found, and the problem to be solved at present is urgently needed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a normal-temperature chlorination and dissolution treatment method of waste platinum-rhodium thermocouples.

The purpose of the invention is realized by adopting the following scheme: a normal-temperature chlorination and dissolution treatment method for waste platinum-rhodium thermocouples comprises the following steps:

1) preparing an iron-based ionic liquid:

1-1) Synthesis of 1-butyl-3-methylchloroimidazole solution:

uniformly mixing N-methylimidazole and N-butyl chloride according to a molar ratio of 1:1, and fully reacting to obtain a 1-butyl-3-methylimidazole chloride solution, wherein the reaction formula of the process is as follows:

1-2) synthesis of iron-based ionic liquid:

mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂Mixing O uniformly according to a molar ratio of 1:2, fully reacting, and standing for liquid separation to obtain an iron-based ionic liquid;

the reaction formula of the process is as follows:

2) chloridizing and dissolving the waste platinum-rhodium thermocouple at normal temperature:

2-1) uniformly mixing the iron-based ionic liquid and hydrochloric acid to obtain a mixed solution, wherein the volume ratio of the iron-based ionic liquid to the hydrochloric acid in the mixed solution is 2-4: 15-20;

2-2) putting crushed waste platinum-rhodium thermocouple particles into the mixed solution to be submerged, continuously introducing chlorine into the mixed solution, stirring the mixed solution, and respectively oxidizing platinum ions and rhodium ions to +4 and +3 by using [ Cl ] generated by the chlorine so as to realize the dissolution of platinum and rhodium;

2-3) carrying out sampling detection analysis on the mixed solution for multiple times, stopping introducing chlorine when the contents of platinum ions and rhodium ions in the mixed solution are not less than 98%, and stopping stirring;

3) purifying and separating simple substance rhodium and simple substance platinum:

adding NaOH into a mixed solution with the contents of platinum ions and rhodium ions being more than or equal to 98 percent for precipitating rhodium, purifying and separating simple substance rhodium, taking out the simple substance rhodium, and adding NH into the mixed solution₄And precipitating the platinum by using Cl, purifying and separating the simple substance platinum, and taking out the simple substance platinum.

In the step 1-1), impurities in the 1-butyl-3-methyl imidazole chloride solution are removed by adopting an impurity removal method.

The impurity removal method adopts the following steps to remove impurities in the 1-butyl-3-methyl imidazole chloride solution in the step 1-1):

adding ethyl acetate into the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1), placing the solution in a rotary evaporator, setting the operating temperature to be 70 ℃, evaporating and removing the ethyl acetate in the 1-butyl-3-methyl imidazole chloride solution, and then placing the 1-butyl-3-methyl imidazole chloride solution in a vacuum drying oven at 70 ℃ for drying.

In the step 1-1), the N-methylimidazole and N-butyl chloride are fully reacted by adopting the following method: under the condition of room temperature, uniformly mixing N-methylimidazole and N-butane chloride according to the molar ratio of 1:1, putting the mixture into a constant-temperature magnetic stirrer, and continuously stirring for at least 72 hours, wherein the temperature in the constant-temperature magnetic stirrer is 65-75 ℃.

In the step 1-2), the 1-butyl-3-methyl imidazole chloride solution and FeCl are mixed by the following method₃·6H₂And (3) fully reacting O: under the condition of room temperature, 1-butyl-3-methyl imidazole chloride solution and FeCl₃·6H₂Mixing O uniformly according to the molar ratio of 1:2, and placingIn a constant temperature stirrer, the reaction temperature is set to 70 ℃ and the reaction is continuously stirred for 24 h.

The iron-based ionic liquid is obtained by adopting the following steps of standing and liquid separation in the step 1-2): mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂O is uniformly mixed according to the molar ratio of 1:2 and fully reacted, then the mixture is put into a separating funnel and stands until the solution is separated into two phases, and after the liquid at the lower layer is drained from the lower port of the separating funnel, the dark green liquid at the upper layer, namely the iron-based ionic liquid, is collected from the upper port;

and 2) washing the waste platinum-rhodium thermocouple with ethanol and deionized water to remove surface stains before crushing.

The structural formula of the iron-based ionic liquid is as follows:

the concentration of the hydrochloric acid in the step 2-1) is 4-14 mol/L.

The concentration of the iron-based ionic liquid in the step 2-1) is 2-8 mol/L.

The invention has the following beneficial effects: when the waste platinum-rhodium thermocouple is dissolved, the dissolution rate of rhodium which is an insoluble matter of aqua regia is improved by using the iron-based ionic liquid, the dissolution rate of platinum-rhodium alloy is greatly promoted, the dissolution time is greatly shortened, the dissolution rate and the dissolution speed reach the international advanced level, and the method has great industrial application potential.

The invention can also find out the optimal reaction condition by adjusting the stirring speed, the hydrochloric acid concentration, the chlorine gas introduction amount, the reaction time, the concentration of the iron-based ionic liquid and the like to influence the dissolution efficiency of the waste platinum-rhodium thermocouple.

Because the rhodium content is more than 5 percent, the platinum-rhodium alloy can not be dissolved by methods such as aqua regia dissolution method, and the like, but the invention can dissolve the platinum-rhodium alloy with the rhodium content of more than 5 percent, and can not generate aqua regia insoluble slag and NO_xPollutants are dissolved by the aid of iron-based ionic liquid, and the platinum-rhodium alloy can be continuously and rapidly dissolved at normal temperature by introducing chlorine.

The invention has the advantages that 1-butyl-3-methyl imidazole chloride and ferric trichloride hexahydrate are used for synthesizing the iron-based ionic liquid, and the platinum-rhodium ions are enriched to accelerate the dissolution of the platinum-rhodium alloy by adding the iron-based ionic liquid into a device for dissolving the platinum-rhodium alloy in the waste platinum-rhodium thermocouple.

The optimal reaction condition can be found out by influencing the dissolving effect of the platinum-rhodium alloy under different conditions of pH, hydrochloric acid concentration, chlorine gas introduction amount, reaction time, ionic liquid concentration and the like, the operation is simple, the investment cost is low, and the guarantee is provided for industrialization.

In summary, the invention provides a normal-temperature chlorination and dissolution treatment method for waste platinum-rhodium thermocouples, which utilizes Cl at normal temperature₂The oxidation of the catalyst and the generated hypochlorous acid dissolve platinum-rhodium alloy materials, 1-butyl-3-methyl chloroimidazole and ferric chloride hexahydrate are used for synthesizing iron-based ionic liquid to enrich platinum and rhodium ions and accelerate the dissolution of the platinum-rhodium alloy materials, the platinum and rhodium can be enriched and recovered only by uniformly stirring, the energy consumption is saved, the process cost is reduced, the adopted chlorine is convenient to recover and treat, the harmless and recycling treatment of the recovery of the waste platinum-rhodium alloy is realized, and the waste thermocouple treated by the method can reach the direct yield of more than 98 percent, accords with sustainable development roads advocated by China, and also accords with the times theme of the world at present.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a graph showing the effect of acidity on platinum-rhodium alloy dissolution according to the present invention;

FIG. 3 is a graph showing the effect of the amount of oxidant used in the present invention on the dissolution of a platinum-rhodium alloy;

FIG. 4 is a graph showing the effect of the dosage of the iron-based ionic liquid on the dissolution of the platinum-rhodium alloy.

Detailed Description

As shown in fig. 1 to 4, a normal temperature chlorination and dissolution treatment method for waste platinum-rhodium thermocouples comprises the following steps:

1) preparing an iron-based ionic liquid:

1-1) Synthesis of 1-butyl-3-methylchloroimidazole solution:

uniformly mixing N-methylimidazole and N-butyl chloride according to a molar ratio of 1:1, and fully reacting to obtain a 1-butyl-3-methylimidazole chloride solution, wherein the reaction formula of the process is as follows:

in the step 1-1), impurities in the 1-butyl-3-methyl imidazole chloride solution are removed by adopting an impurity removal method.

The impurity removal method adopts the following steps to remove impurities in the 1-butyl-3-methyl imidazole chloride solution in the step 1-1):

adding ethyl acetate into the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1), placing the solution in a rotary evaporator, setting the operating temperature to be 70 ℃, evaporating and removing the ethyl acetate in the 1-butyl-3-methyl imidazole chloride solution, and then placing the 1-butyl-3-methyl imidazole chloride solution in a vacuum drying oven at 70 ℃ for drying.

In the step 1-1), the N-methylimidazole and N-butyl chloride are fully reacted by adopting the following method: under the condition of room temperature, uniformly mixing N-methylimidazole and N-butane chloride according to the molar ratio of 1:1, putting the mixture into a constant-temperature magnetic stirrer, and continuously stirring for at least 72 hours, wherein the temperature in the constant-temperature magnetic stirrer is 65-75 ℃.

1-2) synthesis of iron-based ionic liquid:

mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂Mixing O uniformly according to a molar ratio of 1:2, fully reacting, standing, separating to obtain an iron-based ionic liquid, wherein the chemical formula of the 1-butyl-3-methylimidazolium chloride is [ Bmim ]]Cl, the chemical formula of the iron-based ionic liquid is [ Bmim ]][FeCl₄]；

The reaction formula of the process is as follows:

the structural formula of the iron-based ionic liquid is as follows:

in the step 1-2), the 1-butyl-3-methyl imidazole chloride solution and FeCl are mixed by the following method₃·6H₂And (3) fully reacting O: under the condition of room temperature, 1-butyl-3-methyl imidazole chloride solution and FeCl₃·6H₂And (3) uniformly mixing the O according to the molar ratio of 1:2, placing the mixture into a constant-temperature stirrer, and setting the reaction temperature to be 70 ℃ to continuously stir and react for 24 hours.

The iron-based ionic liquid is obtained by adopting the following steps of standing and liquid separation in the step 1-2): mixing the 1-butyl-3-methyl imidazole chloride solution obtained in the step 1-1) with FeCl₃·6H₂O is uniformly mixed according to the molar ratio of 1:2 and fully reacted, then the mixture is put into a separating funnel and stands until the solution is separated into two phases, and after the liquid at the lower layer is drained from the lower port of the separating funnel, the dark green liquid at the upper layer, namely the iron-based ionic liquid, is collected from the upper port;

2) chloridizing and dissolving the waste platinum-rhodium thermocouple at normal temperature:

2-1) uniformly mixing the iron-based ionic liquid and hydrochloric acid to obtain a mixed solution, wherein the volume ratio of the iron-based ionic liquid to the hydrochloric acid in the mixed solution is 2-4: 15-20;

the concentration of the hydrochloric acid in the step 2-1) is 4-14 mol/L.

The concentration of the iron-based ionic liquid in the step 2-1) is 2-8 mol/L.

2-2) putting crushed waste platinum-rhodium thermocouple particles into the mixed solution to be submerged, continuously introducing chlorine into the mixed solution, stirring the mixed solution, and respectively oxidizing platinum ions and rhodium ions to +4 and +3 by using [ Cl ] generated by the chlorine so as to realize the dissolution of platinum and rhodium;

2-3) carrying out sampling detection analysis on the mixed solution for multiple times, stopping introducing chlorine when the contents of platinum ions and rhodium ions in the mixed solution are not less than 98%, and stopping stirring;

in the embodiment, the mixed solution is sampled every 15min, and an icp-aes analyzer is used for detecting to obtain the content of platinum ions and rhodium ions in the mixed solution.

3) Purifying and separating simple substance rhodium and simple substance platinum:

adding NaOH into a mixed solution with the contents of platinum ions and rhodium ions being more than or equal to 98 percent for precipitating rhodium, purifying and separating simple substance rhodium, taking out the simple substance rhodium, and adding NH into the mixed solution₄And precipitating the platinum by using Cl, purifying and separating the simple substance platinum, and taking out the simple substance platinum.

The invention comprises the following steps of performing chlorination and dissolution treatment on waste platinum-rhodium thermocouple particles at normal temperature:

example 1:

1500mL of hydrochloric acid with the concentration of 4mol/L and 200mL of iron-based ionic liquid with the concentration of 8mol/L which is prepared in advance are mixed, 200g of waste platinum-rhodium thermocouple particles (number 1: Pt90 wt%, Rh10 wt%) which are cleaned in advance are weighed and placed in a mixed solution, then chlorine is introduced at the speed of 2L/min to saturate the chlorine in the mixed solution, 5mL of the mixed solution is sampled every 15min after uniform stirring, and an icp-aes analyzer is used for detecting the contents of platinum ions and rhodium ions in the mixed solution. Stopping stirring when the content of platinum ions and rhodium ions in the mixed solution reaches 98%, and stopping introducing chlorine; the reagent consumed for dissolving the platinum-rhodium alloy in the present example is shown in Table 1.

Example 2:

1500mL of hydrochloric acid with the concentration of 8mol/L and 300mL of iron-based ionic liquid with the concentration of 4mol/L which is prepared in advance are mixed, 200g of waste platinum-rhodium thermocouple particles (number 1: Pt80 wt%, Rh20 wt%) which are pretreated and cleaned are weighed and placed in a mixed solution, then chlorine is introduced at the speed of 2L/min to saturate the chlorine in the mixed solution, 5mL of the mixed solution is sampled every 15min after uniform stirring, and an icp-aes analyzer is used for detecting the contents of platinum ions and rhodium ions in the mixed solution. Stopping stirring when the content of platinum ions and rhodium ions in the mixed solution reaches 98%, and stopping introducing chlorine; the reagent consumed for dissolving the platinum-rhodium alloy in the present example is shown in Table 1.

Example 3:

1500mL of hydrochloric acid with the concentration of 12mol/L and 400mL of iron-based ionic liquid with the concentration of 2mol/L which is prepared in advance are mixed, 200g of waste platinum-rhodium thermocouple particles (number 1: Pt70 wt%, Rh30 wt%) which are pretreated and cleaned are weighed and placed in a mixed solution, then chlorine is introduced at the speed of 2L/min to saturate the chlorine in the mixed solution, 5mL of the mixed solution is sampled every 15min after uniform stirring, and an icp-aes analyzer is used for detecting the contents of platinum ions and rhodium ions in the mixed solution. Stopping stirring when the content of platinum ions and rhodium ions in the mixed solution reaches 98%, and stopping introducing chlorine; the reagent consumed for dissolving the platinum-rhodium alloy in the present example is shown in Table 1.

TABLE 1 materials consumed in examples 1-3

In summary, the present invention utilizes Cl at normal temperature₂The oxidation of the catalyst and the generated hypochlorous acid dissolve platinum-rhodium alloy materials, 1-butyl-3-methyl chloroimidazole and ferric chloride hexahydrate are used for synthesizing iron-based ionic liquid to enrich platinum and rhodium ions and accelerate the dissolution of the platinum-rhodium alloy materials, the platinum and rhodium can be enriched and recovered only by uniformly stirring, the energy consumption is saved, the process cost is reduced, the harmless and recycling treatment of the recovery of the waste platinum-rhodium alloy is realized, the direct yield of the waste thermocouple treated by the method is more than 98%, the method accords with sustainable development roads advocated by China and also accords with the era theme of the world nowadays.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and those skilled in the art can make modifications without departing from the spirit of the present invention.