JP6834467B2 - Deterioration analysis method for organic solvents - Google Patents

Description

The present invention relates to a method for analyzing deterioration of an organic solvent. More specifically, the present invention relates to a deterioration analysis method for an organic solvent used for grasping the state of a phosphorus-containing organic solvent.

Demand for valuable metals such as nickel and cobalt, which are contained in trace amounts in minerals, is rapidly increasing with the development of industry, while the production of nickel oxide ore containing high-grade nickel and cobalt is decreasing. There is a tendency. Therefore, an extraction method using a phosphoric acid-based organic solvent in which phosphorus is present in the molecule has been widely adopted. By using such a phosphoric acid-based organic solvent, there is an advantage that nickel and the like can be selectively recovered.

On the other hand, in terms of operation, the phosphoric acid-based organic solvent used for extraction is repeatedly used, but there arises a problem that the extraction efficiency of nickel and cobalt decreases depending on the usage conditions. It is considered that this is because the phosphoric acid-based organic solvent deteriorates due to repeated use of the phosphoric acid-based organic solvent. Therefore, it is very important to grasp the deteriorated state of the phosphoric acid-based organic solvent in order to efficiently recover nickel and cobalt. Especially in the operation process of recovering nickel and the like from minerals and the like, it is very important to quickly grasp such a state.

Here, it is considered that the deterioration of the phosphoric acid-based organic solvent is caused by a state in which a part of the phosphoric acid-based organic solvent cannot exert the extraction function. Specifically, it is considered that the cause is that phosphorus flows out from the organic compound constituting the phosphoric acid-based organic solvent together with the extractant, and the portion of the phosphoric acid-based organic solvent that exerts the extraction function is reduced.
That is, the state of the phosphoric acid-based organic solvent is affected by the amount of phosphorus in the phosphoric acid-based organic solvent. Therefore, if the concentration of phosphorus in the phosphoric acid-based organic solvent can be quantified, the phosphoric acid-based organic solvent can be used. It is thought that the state can be grasped.

Usually, an inductively coupled plasma emission spectrometer (ICP-OES) or the like having an inductively coupled plasma (ICP) capable of accurately measuring the metal in the solution is used for measuring metals such as phosphorus existing in the solution. Has been done.
However, while the above-mentioned apparatus can accurately measure metals such as phosphorus in the solution, the presence of an organic compound in the solution causes various problems in the apparatus.
Therefore, when a phosphoric acid-based organic solvent or the like is present in the solution, it is necessary to perform pretreatment to decompose the phosphoric acid-based organic solvent or the like in the solution.

As a method for decomposing an organic compound such as a phosphoric acid-based organic solvent in a solution, generally, an open system decomposition method using a mixed solution of nitric acid and sulfuric acid, a pressure decomposition method using an acid under pressure, etc. Has been adopted.

However, in the former method, since the decomposition treatment is performed in an open system, phosphorus is oxidized during the decomposition treatment and partially volatilizes as phosphoric acid to be lost, and phosphorus in the phosphoric acid-based organic solvent is accurately quantified. There is a problem that it cannot be done.
Further, the latter method has a problem that it takes time to supply heat from the outside to the inside of the thick pressure vessel to bring the inside of the pressure vessel into a high temperature and high pressure state. Moreover, since heat is supplied to the pressure vessel from the outside, there is a problem that the temperature inside the pressure vessel is difficult to become uniform. That is, the latter method may not be able to properly decompose the phosphoric acid-based organic solvent.

On the other hand, a method for rapidly separating phosphorus present in an organic solvent from the organic solvent has been proposed (for example, Patent Document 1).

Patent Document 1 discloses a method for separating and quantifying phosphorus present in a tributyl phosphate organic solvent from such an organic solvent. First, an organic solvent is brought into contact with an alkaline aqueous solution to extract phosphoric acid in the aqueous solution. By subjecting this extract solution to ion chromatography, contaminants and phosphoric acid present in the extract solution are separated to prepare a phosphoric acid eluate containing phosphoric acid as a main component. It is described that the phosphorus concentration in the tributyl phosphate organic solvent can be quantified by measuring this phosphoric acid eluate using an ICP device. That is, the technique of Patent Document 1 has an advantage that phosphorus present in the organic solvent can be measured in a short time as compared with the general analysis method as described above because it is not necessary to decompose the organic solvent. is there.

Japanese Unexamined Patent Publication No. 7-721136

However, in the technique of Patent Document 1, since the back extraction step using an alkaline aqueous solution must be performed a plurality of times, there is a problem that the phosphorus recovery rate tends to vary. Further, since it is necessary to perform an ion chromatography operation after the back extraction step, there is a problem that the pretreatment operation becomes complicated. That is, in the analysis method of Patent Document 1, while the operation of decomposing the organic solvent is not performed, there is a problem that the pretreatment operation becomes complicated and the analysis value may vary.

In view of the above circumstances, an object of the present invention is to provide a deterioration analysis method for an organic solvent capable of appropriately grasping the state of a phosphorus-containing organic solvent.

The deterioration analysis method for an organic solvent of the first invention is an analysis method used for grasping the deterioration state of the target organic solvent, in which the target organic solvent and the nitrate solution are housed in a closed container and both are stored. Present in a microwave irradiation step of irradiating a mixed solution of both liquids contained in the closed container with a microwave in a sealed state, and in an analysis sample prepared after the microwave irradiation step. This is a method of sequentially performing a measurement step of measuring phosphorus to be produced, wherein the target organic solvent contains mono-2-ethylhexyl 2-ethylhexylphosphonate as a main component, and in the microwave irradiation step, the said It is characterized by irradiating microwaves so that the temperature of the mixed solution in the closed container becomes 200 ° C. or higher.
The method for analyzing deterioration of an organic solvent of the second invention is characterized in that, in the first invention, the nitric acid concentration of the nitric acid solution is 5 mol / L to 11 mol / L.

According to the first invention, a subject containing mono-2-ethylhexyl 2-ethylhexylphosphonate (PC-88A) as a main component can be subjected only by a simple operation of storing it in a closed container and irradiating it with a predetermined microwave. The organic solvent can be decomposed appropriately and quickly. Moreover, by using a closed container, the loss of phosphorus can be reliably suppressed. Therefore, the phosphorus concentration in the target organic solvent can be accurately quantified. Then, based on the obtained quantitative value, the deteriorated state of the target organic solvent can be quickly and appropriately grasped.
According to the second invention, the target organic solvent can be decomposed more appropriately by adjusting the nitric acid concentration to a predetermined value.

It is a schematic flow chart of the deterioration analysis method of the organic solvent of this embodiment.

The organic solvent deterioration analysis method of the present invention is characterized in that the deterioration state of the target organic solvent can be diagnosed by accurately quantifying the concentration of phosphorus in the target organic solvent. ing.

The target organic solvent in the method for analyzing the deterioration of an organic solvent of the present invention is not only composed of an organic solvent but also a small amount of another solvent (for example, water or another organic compound) mixed in the organic solvent. It is a concept that includes those in a state of being.

The target organic solvent in the method for analyzing deterioration of an organic solvent of the present invention is not particularly limited as long as it contains phosphorus in the solvent.
For example, an organic solvent used for hydrometallurgy can be targeted. Specifically, in the process of recovering a valuable metal such as nickel by wet refining, an organic solvent obtained by extracting nickel or the like from a solution in which a metal sulfide such as nickel is dissolved in an acid such as sulfuric acid can be mentioned. As the organic compound which is the main component of this organic solvent, an organic compound in which phosphorus is bound in the molecule is used. As the organic compound, for example, mono-2-ethylhexyl 2-ethylhexyl phosphonate (PC-88A), bis hydrogen phosphate (2-ethylhexyl) (D2EHPA), and the like are adopted.

Next, the deterioration analysis method for the organic solvent of the present invention will be described. As the target organic solvent, PC-88A used in the extraction step of the nickel and cobalt recovery process by hydrometallurgy will be described as a representative.

First, before each step of the organic solvent deterioration analysis method of the present invention is described in detail, each step will be briefly described with reference to FIG.

As shown in FIG. 1, in the method for analyzing deterioration of an organic solvent of the present invention, first, a predetermined amount (for example, about 0.25 ml) of the target organic solvent is collected, and the collected target organic solvent is used as a closed container described later. To be housed in. Then, a nitric acid solution having a predetermined concentration is added to the closed container, and both liquids are mixed in the closed container to prepare a mixed solution.

The nitric acid concentration of the nitric acid solution to be mixed is adjusted so that the nitric acid concentration can be decomposed in the microwave irradiation step of the next step. For example, the nitric acid solution is adjusted so that its nitric acid concentration is 5 mol / L or more.
Both liquids described above may be directly stored in a closed container described later as described above, or once stored in a beaker or the like may be transferred to a closed container described later.

Then, the closed container containing the mixed solution is subjected to the microwave irradiation step of the next step.
In this microwave irradiation step, a microwave irradiation device provided with a device for generating microwaves is used. A closed container is set in such a device, and the mixed solution contained in the closed container is irradiated with microwaves to thermally decompose the organic solvent to be the target existing in the mixed solution.

The microwave emitted from the microwave irradiation device is adjusted so that the temperature of the mixed solution in the closed container becomes a predetermined temperature. Specifically, the microwave is irradiated so that the temperature of the mixed solution becomes equal to or higher than the temperature at which the target organic solvent decomposes (the decomposition temperature of the target organic solvent).

The closed container is a container that can seal the inside of the accommodation space formed inside, and is not particularly limited as long as it is made of a material capable of transmitting microwaves. For example, known pressure-resistant airtight containers made of glass, polytetrafluoroethylene (PTFE), ceramic or the like can be used.

Further, in the microwave irradiation step, whether or not the target organic solvent is properly decomposed is whether or not the liquid in the closed container after the microwave irradiation step, that is, the decomposed solution is in a decomposed state (decomposed state). Can be judged by. That is, it can be determined that the decomposition is insufficient in a state where an undissolved substance is present in the decomposition solution (for example, a state in which the decomposition solution is turbid or a colloidal state).

The decomposition state means that the decomposition solution is colorless and transparent or has no turbidity.

Then, by subjecting the liquid (decomposition solution) in the closed container obtained by the microwave irradiation step to a predetermined analyzer, phosphorus present in the decomposition solution can be measured.
This analyzer is not particularly limited as long as it can measure phosphorus present in the solution. For example, an inductively coupled plasma emission spectrometer (ICP-OES), an inductively coupled plasma mass spectrometer (ICP-MS), an atomic absorption spectrometer, and the like can be mentioned. In particular, ICP-OES or the like is preferable because phosphorus present in the decomposition solution can be measured accurately.

As described above, in the deterioration analysis method of the organic solvent of the present invention, the target organic solvent can be quickly selected by simply irradiating the mixed solution of the target organic solvent and the nitric acid solution with microwaves. It can be decomposed into (for example, about 10 minutes). Moreover, at this time, since the nitric acid solution having a predetermined concentration is mixed, the target organic solvent existing in the mixed solution can be appropriately decomposed into an elemental state.

Moreover, since the organic solvent to be targeted is decomposed in the closed container in the microwave irradiation step, it is possible to reliably prevent phosphorus from being lost due to volatilization or the like during the decomposition.

Therefore, by applying the decomposition solution after the microwave irradiation step to a predetermined analyzer, phosphorus present in the decomposition solution can be measured accurately.
Then, if the concentration of phosphorus present in the target organic solvent is calculated based on the measured value and the collected amount of the target organic solvent, the phosphorus concentration in the target organic solvent can be accurately quantified. ..

Then, based on the obtained quantitative value of phosphorus in the target organic solvent, the state of the target organic solvent can be appropriately grasped.
For example, when the target organic solvent is after use, the quantitative value of phosphorus present in the target organic solvent, the quantitative value of phosphorus present in the new target organic solvent before use, and the quantitative value of phosphorus. By comparing, it is possible to appropriately grasp how much the target organic solvent is deteriorated with respect to the new target organic solvent. In other words, the deteriorated state of the target organic solvent can be appropriately diagnosed.

Therefore, if the target organic solvent is analyzed using the organic solvent deterioration analysis method of the present invention, is the target organic solvent suitable for its intended use (for example, the organic solvent used in the extraction step in hydrometallurgy)? It is possible to judge (that is, diagnose) whether or not it is appropriate and prompt.

Further, since the operation is as simple as irradiating the airtight container in which the target organic solvent and the nitric acid solution are mixed with microwaves, the work efficiency of the pretreatment operation for analysis can be improved. Moreover, since the operation is simple, it is possible to suppress variations in the measured values by the operator.

Further, in the method for analyzing deterioration of an organic solvent of the present invention, the steps from collecting the target organic solvent to preparing the decomposition solution can be performed in a closed container. Therefore, contamination from the outside such as other appliances can be suppressed. Since the number of processing steps is very small as described above, the time of exposure to the working environment can be shortened from the collection of the organic solvent to be the target to the preparation of the measurement sample. That is, the pretreatment can be performed more quickly than the usual measurement method. Therefore, the pretreatment solution can almost prevent contamination (so-called contamination) from the operating equipment, the operator, and the working environment.

Furthermore, as described above, the only acid solution used for decomposing the target organic solvent is the nitric acid solution. That is, sulfuric acid, which is a highly reactive strong oxidizing agent, is not used. Therefore, in the above-mentioned pretreatment operation of the organic solvent to be targeted, the risk of bumping or the like that occurs when sulfuric acid is used can be avoided, so that the pretreatment can be performed safely and sulfuric acid is used. The workability of pretreatment can be improved as compared with the case.
In addition, nitric acid is preferable from an economical point of view because it can reduce the cost as compared with sulfuric acid.

Hereinafter, the pretreatment operation in the deterioration analysis method for the organic solvent of the present invention will be specifically described.

(About nitric acid solution)
The nitric acid solution to be mixed with the target organic solvent is adjusted so that the nitric acid concentration becomes a predetermined concentration as described above, so that when the mixed solution of the target organic solvent and the nitric acid solution is decomposed, the target organic The solvent can be decomposed.
For example, the nitric acid solution is preferably prepared so that the nitric acid concentration is 5 mol / L or more in order to decompose the target organic solvent. This is because if the nitric acid concentration of the nitric acid solution is lower than 5 mol / L, the decomposition of the target organic solvent becomes insufficient. The higher the nitric acid concentration of the nitric acid solution, the easier it is to decompose the target organic solvent. Therefore, the upper limit thereof is not particularly limited, but the nitric acid concentration of the nitric acid solution should be 11 mol / L or less in consideration of handleability. It is preferable to prepare in. Therefore, the nitric acid solution is preferably prepared so that the nitric acid concentration is 5 mol / L or more and 11 mol / L or less.

(About the mixing ratio of the target organic solvent and nitric acid solution)
The mixing ratio of the target organic solvent and the nitric acid solution is not particularly limited. For example, the target organic solvent and the nitric acid solution can be mixed so that the volume ratio is 1: 100 to 5: 100.
For example, when the internal volume of the storage space of the closed container is 100 ml and the nitric acid solution to be mixed is 7 mol / L and 10 ml, the amount of the organic solvent to be collected can be 0.1 ml to 0.5 ml. Under the above conditions, if the amount of the target organic solvent collected is less than 0.1 ml, the sampling accuracy of the target organic solvent deteriorates. On the other hand, if the amount of the target organic solvent collected is more than 0.5 ml, the decomposition of the target organic solvent becomes insufficient. Therefore, the mixing ratio of the target organic solvent and the nitric acid solution is adjusted to be 1: 100 to 5: 100 in terms of volume ratio, and the sampling amount of the target organic solvent is 0.1 ml or more. It is preferable to adjust to.

(About closed container)
The closed container is a member capable of heating the mixed solution in a state where the above-mentioned mixed solution is contained in the internal storage space as described above. That is, the closed container is a container that can be closed inside and is formed so as to have a structure that can withstand high temperature and high pressure. As described above, the closed container is made of a material having a property of transmitting microwaves, for example, glass, polytetrafluoroethylene (PTFE), or the like. It is desirable that the material of the closed container is PTFE because it can be a container having excellent heat resistance and chemical resistance.

(About microwave irradiation process)
The microwave irradiation step is a step of irradiating a mixed solution in a closed container with a predetermined microwave as described above to decompose the solution.
As described above, the microwave to be irradiated may be adjusted so that the temperature of the mixed solution is equal to or higher than the decomposition temperature of the target organic solvent, and its frequency and output are not particularly limited.

For example, when the target organic solvent is PC-88A, its decomposition temperature is about 200 ° C. In this case, if the mixed solution is irradiated with a microwave having an output of 1200 W, the mixed solution can reach the decomposition temperature in a short time (about 10 minutes). Then, if such a state is maintained (held) for a predetermined time (for example, 5 to 20 minutes), the target organic solvent can be reliably decomposed. In other words, the decomposition solution after the microwave irradiation step can be prepared so as to be in a decomposed state.

Further, if the microwave to be irradiated is adjusted so that the temperature of the mixed solution is higher than the decomposition temperature, the decomposition time can be shortened. The upper limit temperature of this mixed solution is not particularly limited, but is preferably adjusted to be lower than the heat resistant temperature of the closed container from the viewpoint of safety. For example, when the material of the closed container is PTFE, it is preferable to adjust the temperature of the mixed solution to be about 200 ° C. to 220 ° C.

It was confirmed that the deteriorated state of the target organic solvent can be grasped by using the deterioration analysis method of the organic solvent of the present invention.

The equipment or reagents used in the experiment are as follows.

As the target organic solvent, 2-ethylhexyl phosphonate mono-2-ethylhexyl (PC-88A) (manufactured by Daihachi Chemical Co., Ltd.) was used.
In order to grasp the deteriorated state, a solvent extraction was repeated a plurality of times using a PC-88A after opening. Hereinafter, the opened PC-88A will be referred to as a new PC-88A, and the PC-88A after repeating solvent extraction a plurality of times will be referred to as a reused PC-88A.
In the experiment, the recycled PC-88A used was a PC-88A repeatedly contacted with an acidic solution containing nickel (Ni) and cobalt (Co) a plurality of times.

The nitric acid solution used was adjusted so that the concentration of nitric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was 5 mol / L and 7 mol / L. A nitric acid solution having a nitric acid concentration of 3 mol / L was used as a comparative example.

The equipment and closed container used are as follows.
Closed container: A container made of polytetrafluoroethylene resin (manufactured by Anton Paar) having an internal volume of 100 ml was used.
Microwave irradiation device: A microwave heating decomposition device (manufactured by AntonPaar, model number: Multi Wave3000) was used.
Microwave irradiation conditions: The output is raised to 800 W so that the temperature of the mixed solution of the organic solvent to be targeted and the nitric acid solution contained in the closed container is in the range of 200 ° C. to 220 ° C. Hold for minutes.
Analyzer: An ICP-emission spectroscopic analyzer (manufactured by SPECTRO, model number: ARCOS) was used.

(Preliminary experiment)
As a preliminary experiment, it was confirmed that the organic compound in the target organic solvent could be reliably decomposed by using the deterioration analysis method of the organic solution of the present invention.

When an ICP-emission spectroscopic analyzer is used in the measurement step of the deterioration analysis method for an organic solution of the present invention, if an organic compound remains in a sample to be used in such an apparatus, a high measured value may be exhibited due to a sensitizing effect. .. Therefore, as a preliminary experiment, it was confirmed that no organic compound was present in the sample.
The concentration of the organic compound present in such a sample was measured using a TOC meter (manufactured by Shimadzu Corporation, model number; TOC-5000A).

First, 0.5 ml of recycled PC-88A as the target organic solvent was weighed in a container made of polytetrafluoroethylene resin for a microwave heating decomposition apparatus, and 10 ml of a 7 mol / L nitric acid solution was added.

Next, the above-mentioned container made of polytetrafluoroethylene resin was set in a microwave heat decomposition apparatus and sealed, and the reused PC-88A was heat-decomposed. At that time, the output was raised to 800 W so that the temperature of the recycled PC-88A in the mixed solution was within the range of 200 ° C. to 220 ° C. The temperature of the recycled PC-88A in the mixed solution could be reached to a predetermined temperature in 10 minutes by operating the device. Then it was held for 10 minutes. The temperature of 200 ° C. is the decomposition temperature of PC-88A. The temperature of 220 ° C. is the upper limit of the recommended heat-resistant temperature of the container made of polytetrafluoroethylene resin.

Then, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is put into a 50 ml volumetric flask. I transferred it. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, the carbon content of the organic carbon in the sample was measured using a TOC meter. Then, based on the obtained measured values, the concentration of the organic carbon present in the sample solution for analysis was calculated.

(Result of preliminary experiment)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was not confirmed in the decomposition solution. Moreover, the decomposition solution was almost transparent without any turbidity. The state of the decomposition solution corresponds to the "decomposition state" in the embodiment.

As a result of measuring the analytical sample solution prepared from the above decomposition solution with a TOC meter, the concentration of organic carbon present in the analytical sample solution was less than 5 mg / L.

Therefore, it was confirmed that no organic compound was present in the decomposition solution. That is, it was confirmed that the organic compound existing in the target organic solvent can be completely decomposed by the decomposition conditions using the above apparatus.
Therefore, when the ICP-emission spectroscopic analyzer is used in the measurement step in the deterioration analysis method for organic solutions of the present invention, phosphorus is accurately measured without being affected by undecomposed organic compounds present in the sample solution for analysis. I was able to confirm that I could do it.

The above-mentioned organic carbon concentration (5 mg / L) is a lower limit value that does not affect the measurement result.
In parallel with the preliminary experiment, analysis was performed by _{open system treatment (HNO 3} + H ₂ SO _{4 decomposition treatment).} The organic carbon concentration in the obtained sample was measured using a TOC meter in the same manner as in the preliminary experiment. As a result, the calculated organic carbon concentration was 2 to 4 mg / L. On the other hand, the same concentration was obtained even when the temperature condition of the microwave heating decomposition apparatus was treated at 200 ° C. or higher.
Therefore, the lower limit of the organic carbon concentration that does not affect the measurement was set to 5 mg / L as described above.

(Experiment 1)
It was confirmed that the concentration of phosphorus in PC-88A can be quantified by using the deterioration analysis method of the organic solvent of the present invention.

First, 0.25 ml of the new PC-88A was weighed in a container made of polytetrafluoroethylene resin for a microwave heating decomposition apparatus, and 10 ml of a 7 mol / L nitric acid solution was added.

Next, the above-mentioned container made of polytetrafluoroethylene resin was set in a microwave heat decomposition apparatus and sealed, and the new PC-88A was heat-decomposed. At that time, the output was raised to 800 W so that the temperature of the new PC-88A in the mixed solution was within the range of 200 ° C. to 220 ° C. It was possible to bring the temperature of the new PC-88A in the mixed solution to a predetermined temperature in 10 minutes after operating the device. Then it was held for 10 minutes.

Then, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is put into a 50 ml volumetric flask. I transferred it. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the new PC-88A was calculated.

(Result of Experiment 1)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was not confirmed in the decomposition solution. Moreover, the decomposition solution was almost transparent without any turbidity. That is, it was confirmed that the new PC-88A can be completely decomposed under the above decomposition conditions.
The theoretical concentration of phosphorus present in 0.25 ml of PC-88A is 20.0 g / L. On the other hand, the concentration of phosphorus in the novel PC-88A obtained in Experiment 1 was 20.0 g / L.
The variation when the above operation was performed a plurality of times was 1 to 2%.
The time required from the preparation of the mixed solution to the preparation of the sample solution for analysis was about 60 minutes.
Therefore, it was confirmed that the concentration of phosphorus in PC-88A can be quantified quickly and accurately by using the deterioration analysis method of the organic solvent of the present invention.

(Experiment 2)
In Experiment 2, it was confirmed that the deterioration state in the recycled PC-88A can be grasped by using the deterioration analysis of the organic solution of the present invention.

Reused PC-88A was used instead of the new PC-88A as the target organic solvent.
Except for the above, the same equipment, conditions, etc. as in Experiment 1 were used.

In the same manner as in Experiment 1, the polytetrafluoroethylene resin container is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the polytetrafluoroethylene resin container is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of Experiment 2)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was not confirmed in the decomposition solution. Moreover, the decomposition solution was almost transparent without any turbidity. That is, it was confirmed that the recycled PC-88A can be completely dissolved, that is, decomposed under the above decomposition conditions.
The concentration of phosphorus in the recycled PC-88A obtained in Experiment 2 was 19.0 g / L.

Therefore, since the theoretical concentration of phosphorus present in 0.25 ml of PC-88A was 20.0 g / L, it was confirmed that the phosphorus concentration of the recycled PC-88A was lowered. That is, it was possible to understand that the reused PC-88A is in a deteriorated state as compared with the new PC-88A.

(Experiment 3)
In Experiment 3, it was confirmed that PC-88A, which is the target organic solvent, can be appropriately decomposed when the nitric acid concentration of the nitric acid solution is 5 mol / L or more.

In the experiment, the same equipment and conditions as in Experiment 2 were used except that the nitric acid concentration of the nitric acid solution added to the container made of polytetrafluoroethylene resin for the microwave heating decomposition apparatus was set to 5 mol / L.

Similar to Experiment 2, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of Experiment 3)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was not confirmed in the decomposition solution. Moreover, the decomposition solution was almost transparent without any turbidity. That is, it was confirmed that the recycled PC-88A can be completely dissolved, that is, decomposed under the above decomposition conditions.
The concentration of phosphorus in the recycled PC-88A obtained in Experiment 3 was 19.2 g / L.

Therefore, it was confirmed that the phosphorus concentration in the recycled PC-88A can be accurately quantified even when a nitric acid solution having a nitric acid concentration of 5 mol / L is used.

(Experiment 4)
In Experiment 4, the amount of PC-88A collected, which is the target organic solvent, was confirmed.

In the experiment, the same equipment and conditions as in Experiment 2 were used except that 0.5 ml of the recycled PC-88A was weighed in a container made of polytetrafluoroethylene resin for a microwave heating decomposition apparatus.

Similar to Experiment 2, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of Experiment 4)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was not confirmed in the decomposition solution. Moreover, the decomposition solution was almost transparent without any turbidity. That is, it was confirmed that the recycled PC-88A can be completely dissolved, that is, decomposed under the above decomposition conditions.
The concentration of phosphorus in the recycled PC-88A obtained in Experiment 4 was 19.0 g / L.

Therefore, the phosphorus concentration in the recycled PC-88A can be accurately quantified even when the collected amount of the recycled PC-88A, which is the target organic solvent, is doubled to 0.5 ml as compared with Experiment 2. It could be confirmed.

(Comparative test 1)
In Comparative Test 1, when the nitric acid concentration of the nitric acid solution added to the polytetrafluoroethylene resin container for the microwave heating decomposition device was lower than 5 mol / L, the recycled PC-88A, which is the target organic solvent, was used. It was confirmed that the decomposition was insufficient.

In the experiment, the same equipment and conditions as in Experiment 2 were used except that the nitric acid concentration of the nitric acid solution added to the container made of polytetrafluoroethylene resin for the microwave heating decomposition apparatus was set to 3 mol / L.

Similar to Experiment 2, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of comparative test 1)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was confirmed in the decomposition solution. That is, it was confirmed that the decomposition of the recycled PC-88A was insufficient under the above decomposition conditions.
Therefore, when PC-88A was used as the target organic solvent, it was confirmed that the nitric acid concentration of the nitric acid solution must be higher than 3 mol / L in order to completely decompose the PC-88A.

(Comparative test 2)
In Comparative Test 2, the effect of microwave irradiation conditions on the decomposition of recycled PC-88A was confirmed.

In the experiment, the microwave irradiation conditions were set so that the temperature of the mixed solution of the organic solvent to be targeted and the nitric acid solution contained in the closed container was within the range of 170 ° C to 190 ° C (that is, the decomposition temperature of PC-88A used in the experiment or less). ), The same equipment and conditions as in Experiment 2 were used.

Similar to Experiment 2, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of comparative test 2)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was confirmed in the decomposition solution. That is, it was confirmed that the decomposition of the recycled PC-88A was insufficient under the above decomposition conditions.
Therefore, it was confirmed that the microwave irradiation conditions need to be adjusted so that the heating temperature of the mixed solution in the container made of polytetrafluoroethylene resin is equal to or higher than the decomposition temperature of the organic solvent to be targeted.

(Comparative test 3)
In Comparative Test 3, the effect of the collected amount of recycled PC-88A, which is the target organic solvent, was confirmed.

In the experiment, the same equipment and conditions as in Experiment 2 were used except that 1.0 ml of the recycled PC-88A was weighed in a container made of polytetrafluoroethylene resin for a microwave heating decomposition apparatus.

Similar to Experiment 2, the container made of polytetrafluoroethylene resin is taken out from the microwave heating decomposition apparatus, allowed to cool at room temperature, and then the solution (decomposition solution) prepared in the container made of polytetrafluoroethylene resin is prepared. Transferred to a 50 ml volumetric flask. Water was added to this flask to adjust the volume to 50 ml, and a sample solution for analysis was prepared.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the recycled PC-88A was calculated.

(Result of comparative test 3)
The container made of polytetrafluoroethylene resin was taken out from the microwave heating decomposition apparatus and allowed to stand at room temperature to cool. After allowing to cool, the container made of polytetrafluoroethylene resin was opened and the liquid (decomposition solution) in the container was confirmed. As a result, the presence of undecomposed products (undissolved products) was confirmed in the decomposition solution. That is, it was confirmed that the decomposition of the recycled PC-88A was insufficient under the above decomposition conditions.
Therefore, it was confirmed that the amount of PC-88A collected affects the decomposition of PC-88A.

(Comparative test 4)
In Comparative Test 4, it was confirmed that the phosphorus concentration in the novel PC-88A, which is the target organic solvent, could not be appropriately quantified when the conventional open decomposition method using nitric acid and sulfuric acid was used.

In the experiment, 0.25 ml of fresh PC-88A was weighed in a beaker and dried on a heater at 300 ° C. Then, 5 ml of nitric acid and 2 ml of sulfuric acid (1 + 1) were added to the beaker, and the new PC-88A was thermally decomposed on the heater. The decomposition state was confirmed with white smoke of sulfuric acid. Specifically, after heating to generate white smoke, the operation of adding 3 ml of nitric acid and decomposing was repeated until the new PC-88A was completely decomposed.

Then, pure water and 5 ml of nitric acid were added and dissolved by heating. After allowing the beaker to cool, the heated solution in the beaker was transferred to a 50 ml volumetric flask, and water was added to adjust the volume to 50 ml to prepare a sample solution for analysis.

In the prepared sample solution for analysis, phosphorus present in the sample was measured using an ICP-luminescence spectroscopic analyzer. Then, based on the obtained measured values, the phosphorus concentration in the new PC-88A was calculated.

(Result of comparative test 4)
The prepared sample solution for analysis was free of insoluble substances and was almost transparent without any turbidity. That is, it was confirmed that the new PC-88A can be completely decomposed under the above decomposition conditions.
On the other hand, the concentration of phosphorus in the novel PC-88A obtained in Comparative Test 4 was 17.2 g / L.
Here, since the theoretical concentration of phosphorus present in 0.25 ml of PC-88A is 20.0 g / L, in the conventional release system decomposition method using nitric acid and sulfuric acid, phosphorus is lost due to volatilization or the like during decomposition. It was confirmed that (loss) occurred.
Therefore, it was confirmed that the phosphorus concentration in the novel PC-88A, which is the target organic solvent, cannot be appropriately quantified when the conventional open decomposition method using nitric acid and sulfuric acid is used.

From the above experimental results, it was confirmed that phosphorus present in the organic solvent can be quantified quickly and accurately by using the deterioration analysis of the organic solution of the present invention. Then, it was confirmed that it is possible to grasp the deteriorated state of the organic solvent based on the quantitative value, that is, to diagnose the deteriorated state of the organic solvent.
For example, by using the deterioration analysis of the organic solution of the present invention, it is considered possible to quickly and appropriately diagnose the deterioration state of PC-88A used in the extraction step of the nickel and cobalt recovery process by hydrometallurgy. ..

The method for analyzing deterioration of an organic solvent of the present invention is suitable for rapidly and appropriately quantifying the concentration of phosphorus present in the target organic solvent.

Claims (2)

It is an analytical method used to grasp the deterioration state of the target organic solvent.
Microwave irradiation in which the target organic solvent and the nitrate solution are housed in a closed container, and both liquids are housed and sealed, and the mixed solution of the two liquids housed in the closed container is irradiated with microwaves. It is a method of sequentially performing a step and a measuring step of measuring phosphorus present in an analysis sample prepared after the microwave irradiation step.
The target organic solvent is
2-Ethylhexyl Phosphonate The main component is mono-2-ethylhexyl.
In the microwave irradiation step
A method for analyzing deterioration of an organic solvent, which comprises irradiating microwaves so that the temperature of the mixed solution in the closed container becomes 200 ° C. or higher. The method for analyzing deterioration of an organic solvent according to claim 1, wherein the nitric acid concentration of the nitric acid solution is 5 mol / L to 11 mol / L.

Images