JP7694012B2 - Method and system for determining nickel, cobalt and copper - Google Patents

Description

The present invention relates to a method and system for quantifying nickel, cobalt, and copper.

Conventionally, the quantitative determination of nickel (Ni), cobalt (Co) and copper (Cu) has been carried out on the sulfuric acid leachate using an ICP optical emission spectrometer, as described in Patent Document 1. In this specification, Ni, Co and Cu refer to the state in which they are dissolved in the solution and are ionized.

JP 2019-77912 A

Quantitative analysis of Ni, Co, and Cu in the sulfuric acid leachate is performed using an ICP atomic emission spectrometer, and it takes at least 1-2 hours to obtain quantitative results. This means that, for example, if there is a problem in the sulfuric acid leachate during an industrial process, it will take 1-2 hours before the problem is discovered.

For example, if very little Ni has actually been leached into the sulfuric acid leachate, 1 to 2 hours of leaching work will be wasted. Conversely, if excessive sulfuric acid leaching results in an excessive amount of Cu in the sulfuric acid leachate, the preset reaction time or preset amount of additives in the Cu separation work (e.g., Cu removal process using a cementation reaction) carried out as one step in the industrial process after sulfuric acid leaching may not be sufficient, and the state in which Cu cannot be sufficiently separated may be left for 1 to 2 hours. Reaction control using ORP is also possible, but it is preferable to actually be able to quantify Ni, Co, and Cu.

Moreover, the quantitative determination of Ni, Co, and Cu in the sulfuric acid leachate may need to be carried out several times a day, in some cases, and each time this is done, the above-mentioned risks are incurred.

As a result, it became clear that there was a demand for a quick, simple, and highly accurate in-process analysis method to replace analysis using ICP optical emission spectrometry.

Alternatives to analysis using an ICP optical emission spectrometer include dripping the collected sulfuric acid leachate onto filter paper and then subjecting the filter paper to an XRF analyzer, or analyzing by titration.

When the inventors investigated the application of analysis using an XRF analyzer that uses filter paper, they found that the sensitivity to Cu was poor. Furthermore, analysis by titration requires the operator's titration skills. Furthermore, quantitative accuracy equivalent to that of an ICP optical emission spectrometer is required. In the first place, all of the above methods require pretreatment operations such as dropping onto filter paper, separating, and adjusting the liquid properties, making it impossible to perform rapid analysis.

The objective of the present invention is to perform in-process analysis with appropriate quantitative accuracy easily in a short time and without depending on the operator's level of skill.

The aspects of the present invention made based on the above findings are as follows.
The first aspect of the present invention is a method for producing a cellular membrane comprising the steps of:
A method for quantifying nickel, cobalt and copper in an aqueous sulfate solution, comprising the steps of:
A step 1 of measuring the absorbance of an aqueous sulfate solution collected in a measurement cell;
A step 2 of quantifying nickel, cobalt and copper in the aqueous sulfate solution collected in the measurement cell based on the previously obtained relationship between absorbance and concentration in each of the aqueous nickel sulfate solution, the aqueous cobalt sulfate solution and the aqueous copper sulfate solution after correcting for interferences caused by different elements;
This is a method for quantitatively determining nickel, cobalt and copper.

A second aspect of the present invention is the above-mentioned first aspect,
In the step 1, absorbance is measured at wavelengths in the visible light range,
In step 2, the absorbance in the previously obtained relationship between absorbance and concentration is the absorbance at wavelengths in the visible light range.

A third aspect of the present invention is the first aspect,
In the step 2, when obtaining the relationship between the absorbance and the concentration, a wavelength λa is used for the nickel sulfate aqueous solution, a wavelength λb is used for the cobalt sulfate aqueous solution, and a wavelength λc is used for the copper sulfate aqueous solution (wherein the wavelengths λa, λb, and λc are wavelengths in the visible light range and are different from each other);
In the step 1, absorbance is measured at wavelengths λa, λb, and λc;
In the step 2, as a step 3,
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λa of the nickel sulfate aqueous solution and the concentration, the relationship between the absorbance at the wavelength λa of the cobalt sulfate aqueous solution and the relationship between the absorbance at the wavelength λa of the copper sulfate aqueous solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λb of the aqueous cobalt sulfate solution and the concentration, the relationship between the absorbance at a wavelength λb of the aqueous nickel sulfate solution and the relationship between the absorbance at a wavelength λb of the aqueous copper sulfate solution and the concentration,
The amount of interference caused by the relationship between the absorbance at a wavelength λc and the concentration of an aqueous solution of nickel sulfate and the relationship between the absorbance at a wavelength λc and the concentration of an aqueous solution of cobalt sulfate is eliminated with respect to the relationship between the absorbance at a wavelength λc and the concentration of an aqueous solution of copper sulfate.

A fourth aspect of the present invention is the third aspect,
The wavelength λa is one value in the range of 640 to 680 nm, the wavelength λb is one value in the range of 490 to 530 nm, and the wavelength λc is one value in the range of 780 to 820 nm.

A fifth aspect of the present invention is the aspect according to any one of the first to fourth aspects,
The aqueous sulfate solution has a nickel concentration of 50 to 125 g/L, a cobalt concentration of 1 to 10 g/L, a copper concentration of 1 to 10 g/L, and contains iron as other metal components exceeding 0 g/L and less than 10 g/L.

A sixth aspect of the present invention is the aspect according to any one of the first to fifth aspects,
The sulfate aqueous solution collected in the measurement cell is undiluted,
The optical path width of the measurement cell is 0.5 to 4.0 mm.

A seventh aspect of the present invention is the first aspect of the present invention,
In the step 2, when obtaining the relationship between the absorbance and the concentration, a wavelength λa is used for the nickel sulfate aqueous solution, a wavelength λb is used for the cobalt sulfate aqueous solution, and a wavelength λc is used for the copper sulfate aqueous solution (wherein the wavelengths λa, λb, and λc are wavelengths in the visible light range and are different from each other);
In the step 1, absorbance is measured at least at wavelengths λa, λb, and λc;
In the step 2, as a step 3,
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λa of the nickel sulfate aqueous solution and the concentration, the relationship between the absorbance at the wavelength λa of the cobalt sulfate aqueous solution and the relationship between the absorbance at the wavelength λa of the copper sulfate aqueous solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λb of the aqueous cobalt sulfate solution and the concentration, the relationship between the absorbance at a wavelength λb of the aqueous nickel sulfate solution and the relationship between the absorbance at a wavelength λb of the aqueous copper sulfate solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of nickel sulfate and the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of cobalt sulfate, relative to the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of copper sulfate;
The wavelength λa is a value in a range of 640 to 680 nm, the wavelength λb is a value in a range of 490 to 530 nm, and the wavelength λc is a value in a range of 780 to 820 nm,
The sulfate aqueous solution has a nickel concentration of 50 to 125 g/L, a cobalt concentration of 1 to 10 g/L, a copper concentration of 1 to 10 g/L, and contains iron as other metal components exceeding 0 g/L and less than 10 g/L;
The sulfate aqueous solution collected in the measurement cell is undiluted,
2. The method for quantifying nickel, cobalt and copper according to claim 1, wherein the optical path width of the measurement cell is 0.5 to 4.0 mm.

An eighth aspect of the present invention is the aspect according to any one of the first to seventh aspects,
In the step 1, the absorbance of an aqueous sulfate solution that is continuously passed through a measurement cell is measured.

A ninth aspect of the present invention is a method for producing a composition comprising the steps of:
A system for the determination of nickel, cobalt and copper in an aqueous sulfate solution, comprising:
a branch pipe provided in a pipe that serves as a flow path for the sulfate aqueous solution, the branch pipe branching a part of the sulfate aqueous solution;
A measurement cell for accommodating the branched sulfate aqueous solution;
a spectrometer for measuring the absorbance of the sulfate aqueous solution in the measurement cell;
a calculation mechanism for quantifying nickel, cobalt and copper in the aqueous sulfate solution collected in the measurement cell based on a relationship between absorbance and concentration in each of the aqueous nickel sulfate solution, the aqueous cobalt sulfate solution and the aqueous copper sulfate solution, which has been obtained in advance and after correcting for interference amounts caused by different elements;
The present invention relates to a quantitative system for nickel, cobalt and copper.

A tenth aspect of the present invention is the ninth aspect,
The optical path width of the measurement cell is 0.5 to 4.0 mm.

An eleventh aspect of the present invention is the ninth or tenth aspect of the present invention,
The branched aqueous sulfate solution is continuously passed through the measurement cell.

According to the present invention, in-process analysis with appropriate quantitative accuracy can be easily performed in a short time and regardless of the operator's level of expertise.

FIG. 1 is a flow chart showing a process for recycling waste LIB using a wet process. FIG. 2 shows the absorption spectra of the aqueous sulfate solutions obtained by a spectrophotometer. Fig. 3(a) is a plot showing a calibration curve at each wavelength of an aqueous nickel sulfate solution for obtaining a calibration curve for Ni (vertical axis: absorbance, horizontal axis: concentration (g/L), the same applies below). Fig. 3(b) is a plot showing a calibration curve at each wavelength of an aqueous cobalt sulfate solution for obtaining a calibration curve for Co. Fig. 3(c) is a plot showing a calibration curve at each wavelength of an aqueous copper sulfate solution for obtaining a calibration curve for Cu. FIG. 4 shows the absorption spectra of the sulfate aqueous solutions to be analyzed (samples 1, 3, 4, and 5) obtained by a spectrophotometer.

The embodiment of the present invention is described below. In this specification, "~" refers to a value greater than or equal to a given value and less than or equal to a given value.

This embodiment relates to a method for quantifying nickel, cobalt, and copper in an aqueous sulfate solution. There are no limitations on the aqueous sulfate solution. For example, as described in Examples 1 to 18 of Patent Document 1, it may be a sulfuric acid leachate of atomized powder obtained from waste lithium ion batteries (waste LIBs). Examples of such sulfuric acid leachates are given below.

In this embodiment, it is preferable to mainly carry out the following steps.
Step 1 of measuring the absorbance of the sulfate aqueous solution collected in the measurement cell (step of measuring the absorbance of the sulfate aqueous solution)
A step 2 (quantification step) of quantifying nickel, cobalt and copper in the sulfate aqueous solution collected in the measurement cell based on the previously obtained relationship between absorbance and concentration in each of the nickel sulfate aqueous solution, the cobalt sulfate aqueous solution and the copper sulfate aqueous solution after correcting the amount of interference caused by different elements.

The "sulfate aqueous solution collected in the measurement cell" in step 1 is a sulfate aqueous solution to which no color developer has been added.

One of the triggers for the technical idea of the present invention was the realization that an aqueous solution of nickel sulfate turns green, an aqueous solution of cobalt sulfate turns red, and an aqueous solution of copper sulfate turns blue, and that the relationship between the intensity of each color and the concentration of each metal can be uniquely obtained (a calibration curve can be obtained). Therefore, an absorption spectrum of sufficient intensity can be obtained without using a color former.

As will be shown in the Examples section below, in-process analysis with appropriate quantitative accuracy can be easily performed in a short time and regardless of the operator's level of skill, even without adding additives other than the color former to the sulfate aqueous solution. By not using additives containing color formers, the work time related to the use of additives can be reduced, and quantitative work can be further shortened. In addition, pretreatment operations such as quantitative separation, dilution, and liquid adjustment, which are required for component analysis in ordinary aqueous solutions, are no longer necessary, making it possible to perform continuous in-line measurements during industrial processes, making the method extremely valuable for industrial use.

Conventionally, when sulfuric acid leachate from an industrial process is sampled and the sampled sulfuric acid leachate is subjected to an ICP optical emission spectrometer, the concentration of various metals in the sampled sulfuric acid leachate is usually too high. Therefore, in order to properly measure the leachate with an ICP optical emission spectrometer, the leachate must be pretreated in some way, for example by diluting it (usually about 10,000 times by multi-stage dilution). This is one of the reasons for the increased time required with an ICP optical emission spectrometer.

On the other hand, by applying this embodiment, the pretreatment performed in the measurement with an ICP optical emission spectrometer becomes unnecessary. Although dilution is preferably not performed, dilution of 10 times or less may be performed to improve handling. Dilution to the extent that it does not hinder the shortening of the work time is permitted in the present invention. "Aqueous sulfate solution collected in a measurement cell" includes both undiluted aqueous sulfate solution to be collected and diluted aqueous sulfate solution to be collected.

The absorbance measurement itself in step 1 may be performed using a known spectrometer (e.g., a spectrophotometer (absorption) photometer, photoelectric photometer. Hereinafter, a spectrophotometer will be exemplified). In addition, the absorbance measurement performed when creating a calibration curve in step 2 described below may also be performed using a known spectrometer.

In a preferred embodiment of the present invention, in step 1, absorbance is measured at wavelengths in the visible light range, and in step 2, the absorbance in the previously obtained relationship between absorbance and concentration is the absorbance at wavelengths in the visible light range. In this specification, the "wavelengths in the visible light range" are 360 to 830 nm (or 400 to 830 nm).

There is no limitation on the material of the measurement cell installed in the spectrophotometer in step 1, but in the above preferred example, the material of the measurement cell is not limited to quartz. This makes it possible to use disposable resin measurement cells. As a result, it is possible to eliminate from the start the risk of foreign matter (contamination) caused by reusing quartz cells, and it is also possible to save the trouble of cleaning the quartz measurement cell.

Step 2 will be explained below with a specific example.

First, in step 2, when obtaining the relationship between absorbance and concentration, wavelength λa is used for the nickel sulfate aqueous solution, wavelength λb is used for the cobalt sulfate aqueous solution, and wavelength λc is used for the copper sulfate aqueous solution (however, wavelengths λa, λb, and λc are wavelengths in the visible light range and are different from each other).

More specifically, the wavelength λa is a value in the range of 640 to 680 nm, the wavelength λb is a value in the range of 490 to 530 nm, and the wavelength λc is a value in the range of 780 to 820 nm.

As shown in Figure 2 below, the above numerical range of wavelength λa is a wavelength range near the peak wavelength in the absorption spectrum of an aqueous nickel sulfate solution (horizontal axis: wavelength, vertical axis: absorbance, hereafter the same). Wavelength λb is a wavelength range near the peak wavelength in the absorption spectrum of an aqueous cobalt sulfate solution. Wavelength λc is a wavelength range near the peak wavelength in the absorption spectrum of an aqueous copper sulfate solution.

Incidentally, there are multiple peak wavelengths in the absorption spectrum of nickel sulfate aqueous solution, but it is preferable to use a peak wavelength that is away from the wavelengths λb and λc and in the visible light range where there is little interference from other coexisting sulfates (Co, Cu, Fe).

In particular, when the sulfate solution contains iron (Fe), Fe can be an interfering element with respect to the Ni, Co, and Cu to be quantified. Therefore, it is desirable to select a wavelength at which the absorbance of the absorption spectrum in the iron sulfate solution is close to zero. The above wavelength ranges of wavelengths λa, λb, and λc take this into consideration.

Whether or not the sulfate solution contains Fe, when Ni is the target element, Co and Cu become interfering elements and affect the quantification of Ni from the absorption spectrum of the sulfate solution to be quantified to some extent. Therefore, the amount of interference from different elements (interfering elements) is corrected for the relationship between absorbance and concentration (in one example, a calibration curve) in each of the nickel sulfate solution, cobalt sulfate solution, and copper sulfate solution that has been obtained in advance (step 3, correction step).

Regarding the correction of the amount of interference, for example, as shown in FIG. 3 in the Example below, a calibration curve is obtained for an aqueous solution of nickel sulfate at 660 nm, which is the peak wavelength of Ni. On the other hand, calibration curves are also obtained for 510 nm, which is the peak wavelength of Co, and 800 nm, which is the peak wavelength of Cu. This means that, for example, when obtaining absorbance at 510 nm, which is the peak wavelength of Co, for an aqueous solution of sulfate, the absorbance of Ni at 510 nm inhibits accurate quantification of Co. Correction of the amount of interference refers to, for example, eliminating the influence of the calibration curve of Ni (wavelength 510 nm) and the calibration curve of Cu (wavelength 510 nm) from the results at 510 nm, which is the absorption peak of Co, for the subject of analysis.

The process of obtaining the relationship between absorbance and concentration in advance for each of the nickel sulfate aqueous solution, the cobalt sulfate aqueous solution, and the copper sulfate aqueous solution may be regarded as process 4 (preparation process). Process 4 (preparation process) is performed before process 2 (quantification process) and process 3 (correction process). It may also be performed before process 1 (absorbance measurement process for sulfate aqueous solution).

In the step 2, the following operation is further carried out as a step 3.
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λa of an aqueous solution of nickel sulfate and the concentration, the relationship between the absorbance at the wavelength λa of an aqueous solution of cobalt sulfate and the relationship between the absorbance at the wavelength λa of an aqueous solution of copper sulfate and the concentration.
Eliminate the amount of interference caused by the relationship between the absorbance at wavelength λb of an aqueous cobalt sulfate solution and the concentration, the relationship between the absorbance at wavelength λb of an aqueous nickel sulfate solution and the relationship between the absorbance at wavelength λb of an aqueous copper sulfate solution and the concentration.
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λc and the concentration of an aqueous solution of nickel sulfate and the relationship between the absorbance at the wavelength λc and the concentration of an aqueous solution of cobalt sulfate with respect to the relationship between the absorbance at the wavelength λc and the concentration of an aqueous solution of copper sulfate.

In other words, since the target elements (Ni, Co, and Cu) interfere with each other, inter-element correction is applied in step 3 to simultaneously quantify the other elements. A specific example of the calculation for simultaneously quantifying the other elements is as follows:

If the Lambert-Beer law holds true and the optical path length is constant, absorbance A and concentration C are expressed in a proportional equation. In fact, as shown in the Examples section below, a calibration curve was created from the absorbance of standard solutions of known concentrations, which were valued using the ICP-OES method, and each coefficient (a, b) was calculated. As a result, a good linear relationship was confirmed between the wavelength of the target element and the wavelength of the interfering element in all standard solutions (nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and copper sulfate aqueous solution).

In this embodiment, the absorbance A and the concentration C are expressed as a linear equation (A = aC + b, a; molar extinction coefficient) with an intercept b due to the contribution of the blank test value, etc.

In the ternary system of Ni--Co--Cu of this embodiment, if the additivity of the absorbance of each element holds, the absorbance A can be expressed by the following ternary linear equation of Equation 1.

Furthermore, the concentrations of Ni, Co, and Cu can be calculated by converting Equation 1 into the matrix of Equation 2 below and measuring the absorbance at the wavelengths λa, λb, and λc (for example, wavelengths of 660 nm (Ni), 510 nm (Co), and 800 nm (Cu)) for the aqueous sulfate solution collected in the measurement cell in step 1. Equation 2 below corresponds to the "relationship between absorbance and concentration after correcting for the amount of interference due to different elements."

In general, the long-term variation in absorbance when measuring the same sample solution with a spectrophotometer is small, so once a calibration curve is created, it is possible to simultaneously quantify the target elements simply by measuring the absorbance of the sample to be analyzed. Therefore, this embodiment can be said to be a method that allows analysis in a short time, regardless of the skill level of the operator.

The aqueous sulfate solution has a nickel concentration of 50 to 125 g/L, a cobalt concentration of 1 to 10 g/L, and a copper concentration of 1 to 10 g/L, and may contain iron of more than 0 g/L and less than 10 g/L as other metal components. Even if the nickel concentration is high, applying this embodiment eliminates the need for time-consuming work such as multi-stage dilution.

When performing sulfuric acid leaching on atomized powder, iron is usually contained in the leachate, but the technical idea of the present invention can be applied even if iron is not present in the leachate. Therefore, it is possible to adopt the following specifications: nickel concentration in the sulfate aqueous solution is 50 to 125 g/L, cobalt concentration is 1 to 10 g/L, and copper concentration is 1 to 10 g/L.

The optical path width of the measurement cell is preferably 0.5 to 4.0 mm. Within this range, the absorbance of the sulfate aqueous solution collected in the measurement cell and not diluted will not become saturated. For example, if the solution is diluted by about 2 times, the optical path width of the measurement cell may be 8.0 to 12.0 mm.

The technical concept of the present invention can also be applied to a system (apparatus) that reflects the quantitative determination method for nickel, cobalt, and copper. Below, the system is explained using an example of recovering Ni, Co, and Cu from waste LIB and regenerating the Ni and Co (hereinafter, also referred to as waste LIB recycling). Any content not described below is the same as the content of the quantitative determination method for Ni, Co, and Cu explained so far.

Figure 1 is a flow chart showing the process for recycling waste LIB using a wet process.

The atomized powder used as the raw material for recycling waste LIBs is mainly composed of a Cu-Ni alloy and has strong corrosion resistance. Therefore, by adding elemental sulfur in addition to sulfuric acid, Cu can be separated as copper sulfide. As a result, Ni and Co can be selectively leached into the sulfuric acid solution.

The Cu that is partially dissolved by the sulfuric acid leaching is separated from the leachate in the next process, a cementation reaction (removal of Cu by reduction). The impurity Fe is separated by oxidation neutralization. As a result, a high-purity, high-concentration mixed solution of nickel sulfate and cobalt is obtained.

The goal of the wet process is to obtain a high-purity mixed solution of nickel sulfate and cobalt that can be used as a battery raw material. The target values are, for example, a (Ni + Co) concentration in the recovered solution of 100 g/L or more, and impurities such as Cu: 0.002 g/L or less, and Fe: 0.003 g/L or less.

The nickel, cobalt, and copper quantitative determination system of this embodiment has at least the following configuration.
A branch pipe that is provided in the pipe that serves as the flow path for the sulfate solution and branches off a portion of the sulfate solution; A measurement cell that contains the branched sulfate solution; A spectrometer that measures the absorbance of the sulfate solution in the measurement cell; A calculation mechanism that quantifies the amounts of nickel, cobalt, and copper in the sulfate solution collected in the measurement cell based on the previously obtained relationship between absorbance and concentration for each of the nickel sulfate solution, cobalt sulfate solution, and copper sulfate solution after correcting for the amount of interference caused by different elements.

As explained with reference to FIG. 1, in the quantitative system of this embodiment, a branch pipe is provided to a pipe for sending the sulfuric acid leaching solution obtained after sulfuric acid leaching to a cementation decoppering section where cementation decoppering is performed. The branch pipe leads to a measurement cell installed in advance in the quantitative system (in the spectrophotometer), and the branched sulfate aqueous solution is contained in the measurement cell.

At this time, if the measurement cell is a non-perforated container, the transfer of the sulfate aqueous solution from the branch pipe to the measurement cell is stopped as soon as a certain amount of sulfate aqueous solution accumulates in the measurement cell. If the measurement cell is a perforated container, the sulfate aqueous solution may be continuously passed through the measurement cell. The structure of the spectrophotometer may be set so that the measurement cell is held in this state in the spectrophotometer. "Contained in the measurement cell" is an expression that includes both cases.

The calculation mechanism may be a control mechanism that controls the entire quantitative system, or a separate calculation mechanism may be provided. The calculation mechanism may be a known computer in which a program that controls the quantitative system is installed. In addition, step 3 (interference amount correction step) may be performed by this calculation mechanism.

Specific examples of feedback on quantitative results are as follows:

If the Ni concentration is below the specified value, at least the sulfuric acid leaching process may be stopped. If it is not stopped, it is necessary to increase the Ni concentration. In other words, it is necessary to promote the leaching of Ni. To achieve this, the leaching time in the sulfuric acid leaching section where the sulfuric acid leaching is performed may be increased, or the ORP and/or pH may be manipulated.

Regarding Co, there is a correlation between the leaching rates of Ni and Co. Therefore, if the Co concentration is below the specified value, the same feedback operation as in the case of Ni can be carried out.

If the Cu concentration exceeds the specified value, measures to be taken include increasing the amount of sulfur added during sulfuric acid leaching, manipulating the ORP and/or pH, increasing the reaction time in the cementation copper removal section, and increasing the amount of additives (reducing agents) used in cementation.

After the absorbance measurement of the sulfate aqueous solution in the measurement cell is completed, the sulfate aqueous solution in the measurement cell may be returned to the main pipe before the branch. With the present invention, it is not necessary to add additives such as coloring agents to the sulfate aqueous solution, and there is no problem in returning the sulfate aqueous solution after measurement to the main pipe. Another branch pipe may be provided in the main pipe to return the sulfate aqueous solution after measurement from the measurement cell to the main pipe.

The branch pipe may be provided on a pipe other than the pipe for sending liquid to the cementation decoppering section.

For example, a branch pipe may be provided to the pipe that sends the copper removal solution, which is the sulfate aqueous solution obtained after copper removal by cementation as shown in FIG. 1, to an oxidation/neutralization section where the solution is oxidized and neutralized to remove iron. In this case, the amount of Cu in the copper removal solution can be quantified using the method of this embodiment, and used as a guide to whether copper removal has been performed reliably.

A branch pipe may be provided to the pipe that delivers the deironized solution, which is the aqueous sulfate solution obtained after deironization. In this case, the amount of Fe in the deironized solution can be quantified using the method of this embodiment, and this can be used as a guide to whether deironization has been performed properly.

Furthermore, the present invention can be widely applied to sulfate aqueous solutions in which nickel, cobalt, and copper coexist at high concentrations, and can be used to analyze the components of sulfuric acid leachates in nickel smelting plants, raw material dissolution solutions in nickel sulfate and cobalt sulfate manufacturing plants, etc.

In the present embodiment described above, it takes 5 to 10 minutes to obtain quantitative results from in-process analysis. This means that even if some problem occurs in the sulfuric acid leachate during an industrial process, it takes only 5 to 10 minutes for the problem to be discovered. Therefore, even if almost no Ni has actually been leached into the sulfuric acid leachate, or even if the amount of Cu in the sulfuric acid leachate is excessive, it is possible to fully recover. In addition, there is no problem even if the Ni, Co, and Cu in the sulfuric acid leachate are quantified several times a day. Furthermore, if a quantitative system is used in which the sulfate aqueous solution is continuously passed through, quantitative results can be obtained instantly.

Moreover, as shown in the examples section below, the quantitative accuracy is comparable to that of an ICP optical emission spectrometer. Furthermore, no large-scale pretreatment or addition of additives to the sulfate aqueous solution is required. Also, operation of the spectrophotometer does not depend on the skill level of the operator, compared to the titration method.

As a result, the present embodiment described above allows in-process analysis to be performed easily with appropriate quantitative accuracy in a short time, regardless of the operator's level of skill.

The technical scope of the present invention is not limited to the above-described embodiments, but includes forms with various modifications and improvements within the scope that can derive specific effects obtained by the constituent elements of the invention and their combinations.

For example, in this embodiment, Ni, Co, and Cu were quantified, but the present invention does not exclude the quantification of metal elements other than these. On the other hand, Equation 1 handled in step 3 (correction step) becomes a four-dimensional linear equation, and Equation 2 becomes correspondingly more complex.

The following describes this embodiment. Note that the technical scope of the present invention is not limited to the following embodiment.

In this example, step 4 (preparation step) was carried out first to obtain calibration curves for Ni, Co, and Cu. The specific steps are as follows:

Nickel sulfate crystals, cobalt sulfate crystals, and copper sulfate crystals were each dissolved in water to prepare an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of copper sulfate.

Each sulfate aqueous solution was placed in a measurement cell with an optical path width of 2.0 mm.

The measurement cells containing each sulfate aqueous solution were placed in a spectrophotometer (V-770 manufactured by JASCO Corporation) and the absorption spectra were obtained.

Figure 2 shows the absorption spectrum of each sulfate aqueous solution obtained by a spectrophotometer. The numbers on the plot indicate the metal concentration (g/L) of each sulfate aqueous solution.

Referring to the results in Figure 2, the specific wavelengths were set to 660 nm (near the peak wavelength in the Ni absorption spectrum), 510 nm (near the peak wavelength in the Co absorption spectrum), and 800 nm (near the peak wavelength in the Cu absorption spectrum).

Separately, solutions were prepared in which the metal (Ni, Co, Cu) concentrations in each sulfate solution were varied. The metal concentrations in each solution were measured using an ICP optical emission spectrometer (ICP-OES). The absorbance at wavelengths of 660 nm, 510 nm, and 800 nm of the solutions in which the metal (Ni, Co, Cu) concentrations in each sulfate solution were varied was measured using a spectrophotometer (MP-1200 manufactured by Elma Sales Co., Ltd.).

Figure 3(a) is a plot showing the calibration curves at each wavelength of an aqueous nickel sulfate solution to obtain a calibration curve for Ni (vertical axis: absorbance, horizontal axis: concentration (g/L), same below). Figure 3(b) is a plot showing the calibration curves at each wavelength of an aqueous cobalt sulfate solution to obtain a calibration curve for Co. Figure 3(c) is a plot showing the calibration curves at each wavelength of an aqueous copper sulfate solution to obtain a calibration curve for Cu.

If Ni is the target element and an attempt is made to quantify the sulfate solution to be analyzed according to a calibration curve, at a wavelength of 660 nm (near the peak wavelength in the Ni absorption spectrum), the absorbance exceeds zero not only for the target element Ni, but also for the calibration curves of Co and Cu, which are interfering elements with Ni. Ultimately, the measurement results obtained at a wavelength of 660 nm will be affected by interference from elements other than Ni.

Therefore, in this embodiment, step 2 (quantification step) is followed by step 3 (correction step). Equations 1 and 2 given in step 3 (correction step) of this embodiment are constructed in advance.

Meanwhile, step 1 (a step of measuring the absorbance of an aqueous sulfate solution) is carried out. The aqueous sulfate solution to be quantified in this example is a sulfuric acid leachate in an industrial process employing the flow shown in FIG.
This sulfuric acid leachate was obtained by leaching the atomized powder with sulfuric acid (slurry concentration: 100 g/L).
The concentrations of the sulfuric acid leachate at this time are Ni: 50 to 125 g/L, Co: 1 to 10 g/L, Cu: 1 to 10 g/L, and Fe: more than 0 g/L and less than 10 g/L.

1 mL of sulfuric acid leachate from an industrial process was sampled using a micropipette and placed in a measurement cell (a disposable resin cell with an optical path width of 10.0 mm) and then diluted 2-fold with pure water.

This dilution is a measure to allow the use of a relatively large measurement cell that is easy to handle. The inventors have confirmed that results equivalent to those shown below can be obtained even when a cell with an optical path width of 2.0 mm is used without dilution. Even when a two-fold dilution is performed, the required time increases by only a few minutes.

The measurement cell containing the sulfate aqueous solution was placed in a spectrophotometer (MP-1200 manufactured by Elma Sales Co., Ltd.) and the absorbance was measured. The wavelengths used for the measurement were the above-mentioned 660 nm, 510 nm, and 800 nm.

Figure 4 shows the absorption spectra of the sulfate aqueous solutions to be analyzed (samples 1, 3, 4, and 5) obtained using a spectrophotometer (V-770 manufactured by JASCO Corporation).

The absorbance at each wavelength obtained from Figure 4 was substituted into the above formulas 1 and 2 to quantify Ni, Co, and Cu.

Sulfuric acid leaching solutions from an industrial process employing the flow shown in Figure 1 were collected separately and numbered as samples 1 to 14, and the above-mentioned procedure was carried out for each sample. For comparison, measurements were carried out for samples 1 to 14 using the inductively coupled plasma optical emission spectrometer (ICP-OES). The results are shown in the table below.

It was confirmed that the relative error between this example and the ICP-OES method was within 3% for Ni and Co, and within 4% for Cu. In addition, when a t-test (α = 0.05) was performed, the result was that "there is no significant difference between the quantitative results obtained in this example and those obtained by the ICP-OES method" for any element.

In addition, to confirm the accuracy of repeated measurements, the same sample solution was used to check the daily variation (n=5). As a result, it was confirmed that the relative error between this embodiment and the ICP-OES method was within 1% for Ni, and within 2% for Co and Cu. Even from the perspective of daily variation, it was confirmed that this embodiment and the ICP-OES method have the same accuracy.

In addition, this is the working time assuming that step 4 (preparation step) and step 3 (correction step) have been carried out beforehand, but even if step 1 (absorbance measurement step for sulfate aqueous solution) and step 2 (quantification step) are combined (even if diluted 2-fold), it took about 10 minutes per sample. On the other hand, the ICP-OES method used to obtain the results in Table 1 required 2 hours per sample.

In addition, to confirm the difference due to the equipment, the same measurement was performed using a V-770 manufactured by JASCO Corporation instead of the MP-1200 manufactured by Elma Sales Co., Ltd., but the same results were obtained.

Claims (4)

A method for quantifying nickel, cobalt and copper in an aqueous sulfate solution, comprising the steps of:
A step 1 of measuring the absorbance of an aqueous sulfate solution collected in a measurement cell;
A step 2 of quantifying nickel, cobalt and copper in the aqueous sulfate solution collected in the measurement cell based on the previously obtained relationship between absorbance and concentration in each of the aqueous nickel sulfate solution, the aqueous cobalt sulfate solution and the aqueous copper sulfate solution after correcting for interferences caused by different elements;
having
The sulfate aqueous solution is a sulfuric acid leachate, does not contain any additives including a color former, and is undiluted. The sulfate aqueous solution has a nickel concentration of 50 to 125 g/L, a cobalt concentration of 1 to 10 g/L, a copper concentration of 1 to 10 g/L, and contains iron as other metal components exceeding 0 g/L and less than 10 g/L.
In the step 2, when obtaining the relationship between the absorbance and the concentration, a wavelength λa is used for the nickel sulfate aqueous solution, a wavelength λb is used for the cobalt sulfate aqueous solution, and a wavelength λc is used for the copper sulfate aqueous solution (wherein the wavelengths λa, λb, and λc are wavelengths in the visible light range and are different from each other);
In the step 1, absorbance is measured at least at wavelengths λa, λb, and λc;
In the step 2, as a step 3,
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λa of the nickel sulfate aqueous solution and the concentration, the relationship between the absorbance at the wavelength λa of the cobalt sulfate aqueous solution and the relationship between the absorbance at the wavelength λa of the copper sulfate aqueous solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λb of the aqueous cobalt sulfate solution and the concentration, the relationship between the absorbance at a wavelength λb of the aqueous nickel sulfate solution and the relationship between the absorbance at a wavelength λb of the aqueous copper sulfate solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of nickel sulfate and the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of cobalt sulfate, relative to the relationship between the absorbance at a wavelength λc and the concentration of the aqueous solution of copper sulfate;
The wavelength λa is a value in a range of 640 to 680 nm, the wavelength λb is a value in a range of 490 to 530 nm, and the wavelength λc is a value in a range of 780 to 820 nm,
The optical path width of the measurement cell is 0.5 to 4.0 mm.
Methods for quantitative determination of nickel, cobalt and copper. In the step 1, an absorbance of an aqueous sulfate solution continuously passed through a measurement cell is measured.
The method for quantifying nickel, cobalt and copper according to claim 1 . A system for the determination of nickel, cobalt and copper in an aqueous sulfate solution, comprising:
a branch pipe provided in a pipe that serves as a flow path for the sulfate aqueous solution, the branch pipe branching a part of the sulfate aqueous solution;
A measurement cell for accommodating the branched sulfate aqueous solution;
a spectrometer for measuring the absorbance of the sulfate aqueous solution in the measurement cell;
a calculation mechanism for quantifying nickel, cobalt and copper in the aqueous sulfate solution collected in the measurement cell based on a relationship between absorbance and concentration in each of the aqueous nickel sulfate solution, the aqueous cobalt sulfate solution and the aqueous copper sulfate solution, which has been obtained in advance and after correcting for interference amounts caused by different elements;
Equipped with
The sulfate aqueous solution is a sulfuric acid leachate, does not contain any additives including a color former, and is undiluted. The sulfate aqueous solution has a nickel concentration of 50 to 125 g/L, a cobalt concentration of 1 to 10 g/L, a copper concentration of 1 to 10 g/L, and contains iron as other metal components exceeding 0 g/L and less than 10 g/L.
The optical path width of the measurement cell is 0.5 to 4.0 mm;
The relationship between the absorbance and the concentration is obtained by adopting a wavelength λa having one value in the range of 640 to 680 nm for the nickel sulfate aqueous solution, a wavelength λb having one value in the range of 490 to 530 nm for the cobalt sulfate aqueous solution, and a wavelength λc having one value in the range of 780 to 820 nm for the copper sulfate aqueous solution (wherein the wavelengths λa, λb, and λc are wavelengths in the visible light range and are different from each other);
The relationship after the correction is as follows regarding the relationship between the absorbance and the concentration:
Eliminate the amount of interference caused by the relationship between the absorbance at the wavelength λa of the nickel sulfate aqueous solution and the concentration, the relationship between the absorbance at the wavelength λa of the cobalt sulfate aqueous solution and the relationship between the absorbance at the wavelength λa of the copper sulfate aqueous solution and the concentration,
Eliminate the amount of interference caused by the relationship between the absorbance at a wavelength λb of the aqueous cobalt sulfate solution and the concentration, the relationship between the absorbance at a wavelength λb of the aqueous nickel sulfate solution and the relationship between the absorbance at a wavelength λb of the aqueous copper sulfate solution and the concentration,
The relationship between the absorbance at the wavelength λc of the copper sulfate aqueous solution and the concentration is corrected by eliminating the amount of interference caused by the relationship between the absorbance at the wavelength λc of the nickel sulfate aqueous solution and the relationship between the absorbance at the wavelength λc of the cobalt sulfate aqueous solution,
The spectrometer performs absorbance measurements at least at wavelengths λa, λb, and λc.
Nickel, cobalt and copper determination system. 4. The system for quantitatively determining nickel, cobalt and copper according to claim 3 , wherein the branched aqueous sulfate solution is continuously passed through the measurement cell.