阅读说明：本技术 一种混合酸的废液或回收液中多组分的分析检测方法 (Analysis and detection method for multiple components in waste liquid or recovery liquid of mixed acid ) 是由 唐杰 张留峰 王鑫 孙瑜 岳鹏 于 2021-09-26 设计创作，主要内容包括：本发明公开了一种混合酸的废液或回收液中多组分的分析检测方法,包括准备混合酸的废酸残液或回收酸,检测方法包括测定其中的氢氟酸、盐酸、硅、铝的含量,步骤如下：(1)测定废酸残液或回收酸中Cl～(-)的含量；(2)测定废酸残液或回收酸中游离酸、硅、铝的含量；(3)根据电荷守恒计算氟的含量。本发明采用电位滴定方法分析检测混合酸的废液或回收液中的多种组分,整个过程只需两次滴定便可以计算出Cl～(-)、游离酸、Si、铝、氟的含量,整个过程中样品不需要额外处理,一次出结果,简单快捷,重复性好,适用于工业分析。(The invention discloses an analysis and detection method for multiple components in waste liquid or recovered liquid of mixed acid, which comprises the steps of preparing waste acid residual liquid or recovered acid of the mixed acid, and the detection method comprises the steps of measuring the contents of hydrofluoric acid, hydrochloric acid, silicon and aluminum in the waste acid residual liquid or recovered acid, and comprises the following steps: (1) determination of Cl in waste acid raffinate or recovered acid ‑ The content of (A); (2) measuring the content of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid; (3) the fluorine content was calculated from the conservation of charge. The invention adopts a potentiometric titration method to analyze and detect various components in the waste liquid or the recovery liquid of the mixed acid, and the Cl can be calculated by only twice titrations in the whole process ‑ Free acid, Si, aluminum and fluorine, and the sample does not need extra treatment in the whole process, and the method can obtain a result at one time, is simple and rapid, has good repeatability and is suitable for industrial analysis.)

1. A method for analyzing and detecting multiple components in waste liquid or recovery liquid of mixed acid is characterized in that waste acid residual liquid or recovery acid of the mixed acid is prepared, the detection method comprises the steps of measuring the contents of hydrofluoric acid, hydrochloric acid, silicon and aluminum in the waste acid residual liquid or recovery acid, and the steps are as follows:

(1) determination of Cl in waste acid raffinate or recovered acid^-The content of (A);

(2) measuring the content of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid;

(3) the fluorine content was calculated according to the principle of conservation of charge.

2. The analytical detection method according to claim 1, wherein in the step (1), the determination of the spent acid residue or the recovered acid is performedCl^-The method of (a) comprises:

s1, preparing NaCl standard solution and AgNO with certain concentration₃A solution;

s2, calibrating AgNO by adopting NaCl standard solution₃Solution, calculating the accurate concentration of the silver nitrate solution;

s3, adding deionized water into the quantitative waste acid raffinate or the recycling acid, and using AgNO with known concentration₃Titrating the solution;

s4, calculating Cl in waste acid raffinate or recovered acid^-1The concentration of (c).

3. The analytical detection method according to claim 2, wherein in S2, AgNO₃The concentration of the solution is calculated by the formula:wherein, V_{Terminal point}AgNO consumed for titration endpoint₃Volume of solution.

4. The analytical method as set forth in claim 2, wherein in S4, Cl is calculated^-1The formula of the concentration isNamely, it is

5. The analytical detection method according to any one of claims 1 to 4, wherein in the step (2), the method for determining the content of free acid, silicon and aluminum in the waste acid raffinate or the recovered acid comprises the following steps:

s1, preparing a potassium hydrogen phthalate standard solution and a sodium hydroxide solution with a certain concentration;

s2, calibrating the sodium hydroxide solution by adopting a potassium hydrogen phthalate standard solution, and calculating the accurate concentration of the sodium hydroxide solution;

s3, taking a fixed bodyTitrating the residual waste acid or the recovered acid by using NaOH solution with known concentration until three titration end points appear in the titration, and recording the volume V of NaOH consumed by reaching the three titration end points₁，V₂And V₃；

S4, respectively calculating the contents of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid;

preferably, in S2, the formula for calculating the concentration of the sodium hydroxide solution is C_NaOHV_NaOH＝C_{Potassium hydrogen phthalate}V_{Potassium hydrogen phthalate}I.e. by

6. The analytical detection method according to claim 5, wherein the formula for calculating the free acid content is C_{Free acid}V_{Spent acid raffinate or recycled acid}＝C_NaOHV₁I.e. by

7. The analytical method according to claim 5, wherein the formula for calculating the silicon content in the spent acid raffinate or the recovered acid is 4C_SiV_{Spent acid raffinate or recycled acid}＝(V₂-V₁)C_NaOHI.e. by

8. The analytical detection method according to claim 5, wherein the formula for calculating the aluminum content in the spent acid raffinate or the recovered acid is 4C_AlV_{Spent acid raffinate or recycled acid}＝(V₃-V₂)C_NaOHI.e. by

9. The analytical detection method according to any one of claims 1 to 8, wherein in step (3), the fluorine content is calculated according to the principle of conservation of charge by the formula

10. The use of the method for analyzing and detecting multiple components in the waste liquid or the recovered liquid of the mixed acid according to any one of claims 1 to 9 in the detection of acid liquid components for the purification of lithium ion battery negative electrode materials.

Technical Field

The invention belongs to the field of waste liquid analysis and detection, and particularly relates to a method for analyzing and detecting multiple components in a waste liquid or a recovery liquid of mixed acid.

Background

Graphite used as a negative electrode material of a lithium ion battery is required to have high purity and low impurity content, so that a matched purification process is required to reduce the impurity content in the graphite. At present, many enterprises adopt a mixed acid method to remove impurities in the cathode material, and the mixed acid method is the method with the best effect, the lowest cost and the greatest pollution in the cathode material purification process. In order to reduce the pollution to the environment and simultaneously utilize acid to the maximum extent, the applicant adopts a membrane separation technology to realize the recycling of hydrochloric acid and hydrofluoric acid on the basis of the purification by a mixed acid method. However, in actual practice, the presence of spent acid raffinate or the recovery of acid components (mainly including free acid, Cl) is complicated^-F, Si, Al, etc.) and the content is unknown, the depletion of the free acid, the recovered acid component and the content cannot be clarified. Therefore, there is a need to develop simple, convenient, and easy to operate detection methods for monitoring such solutions.

In the prior art, Han and the like test the component content of a mixed acid system containing phosphoric acid, hydrofluoric acid and sulfuric acid by taking thymolphthalein as a first-stage titration indicator, then taking a calcium chloride solution as a precipitator and then taking the thymolphthalein as a second-stage titration indicator, and obtain a relatively accurate analysis result. Yang Yichao of Yangzhou epidemic prevention station develops HF, HCl and H in air₂SO₄Ion chromatography in the coexistence of the two methods. Populus communis Huizus et al reported potentiometric titration, electrode method, precipitation method, acid-base titration, etc., which are suitable for a mixed system of hydrofluoric acid and sulfuric acid. Antje Hen β ge et al report the determination of HNO by two-step titration using potentiometric titration₃、HF、H₂SiO₄The contents of all components in the mixed acid. Despite the research on a simple mixed acid system detection method, no industrial analysis method for detecting the content of each component of a solution containing HCl, HF, Si and Al is reported at present.

At present, in a more advanced analysis and test means, although anions can be monitored by an ion chromatography, the method has the disadvantages of higher instrument cost, higher requirement on operators, complex operation process, easy error introduction in the dilution process and unsuitability for industrial field analysis. Cations can be detected by plasma emission spectroscopy, but this method also has the disadvantages described above. In addition, since hydrofluoric acid can erode the pipeline (containing silicon), the method can damage equipment and increase the inaccuracy of silicon detection. Therefore, it is necessary to provide a simple, convenient and fast method for analyzing and detecting multiple components in the waste liquid or the recovered liquid of the mixed acid.

The present invention has been made in view of this situation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for analyzing and detecting multiple components in mixed acid waste liquid or recovery liquid. The invention adopts (thunder magnetic automatic titrator) potentiometric titration method to test the content of each component in the waste acid residual liquid or the recovered acid, and Cl can be calculated by only two-step titration in the whole process^-Free acid, Si, aluminum, fluorine content. In the whole process, samples do not need to be processed, the result is obtained at one time, and the method is simple, quick and good in repeatability.

In order to solve the technical problems, the invention adopts the technical scheme that:

the first purpose of the invention is to provide a method for analyzing and detecting multiple components in a waste liquid or a recovery liquid of mixed acid, which comprises the following steps: preparing waste acid residual liquid of mixed acid or recovered acid, wherein the detection method comprises the steps of titrating and calculating the contents of hydrofluoric acid, hydrochloric acid, silicon and aluminum, and comprises the following steps:

(1) determination of Cl in waste acid raffinate or recovered acid^-The content of (A);

(2) measuring the content of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid;

(3) the fluorine content was calculated according to the principle of conservation of charge.

The mixed acid purification method is a method for carrying out acid cleaning purification on a precursor of a negative electrode material by using a mixed solution of hydrochloric acid and hydrofluoric acid with a certain concentration. Because the purified mixed acid solution still contains a large amount of hydrochloric acid and hydrofluoric acid, the effective components in the waste acid residual liquid can be effectively formed in order to reduce the production costAnd respectively recycling and reusing. If the concentration content of the free acid in the recovered acid is not clear, the reusability of the recovered acid is influenced; if the content of the component in the recovered acid is not clear, the recovered acid cannot be adjusted to a usable acid. The waste acid components are detected by an ion chromatograph and an inductively coupled plasma emission spectrometer (ICP), and the mixed acid residual liquid which is purified by acid washing mainly contains free acid and Cl is obtained^-And components such as F, Si, and Al (it should be noted that F, Si, and Al exist in a complicated form in a solution, and not only exist in a single ion form, but are collectively represented by a symbol of an element in the present application). The two test methods have the following characteristics: 1) the cost of the instrument is high; 2) the operation is more complex, and errors are easily introduced; 3) needs special personnel for operation and maintenance, has high specialty, and is not suitable for non-knowledge-intensive enterprises. Therefore, there is an urgent need to develop an industrial analysis method suitable for the analysis of the components of multi-component mixed acids.

Based on the idea of developing a method suitable for analyzing the components of the multi-component mixed acid, the invention provides a method capable of accurately detecting the contents of hydrofluoric acid, hydrochloric acid, silicon, aluminum and fluorine in waste acid residual liquid and recovered acid, so that on one hand, the concentration of free acid can be determined, and the recovered acid can be conveniently recycled; on the other hand, the content of each component can be specified so as to be adjusted to an available acid. According to the analysis and detection method, Cl can be calculated through twice titration^-Free acid, Si, aluminum and fluorine, the sample does not need to be processed in the whole process, the result is obtained at one time, and the method is simple and rapid, good in repeatability and high in accuracy.

The analysis and detection method is suitable for detecting the content of each component in various mixed solutions containing hydrofluoric acid, hydrochloric acid, silicon and aluminum, and is particularly suitable for detecting the acid liquid component for purifying the lithium ion battery cathode material.

In the further scheme, in the step (1), Cl in waste acid raffinate or recovered acid is measured^-The method for content comprises the following steps:

s1, preparing NaCl standard solution and AgNO with certain concentration₃A solution;

s2, calibrating AgNO by using NaCl standard solution₃Solution, calculationThe accurate concentration of the silver nitrate solution;

s3, adding deionized water into the quantitative waste acid raffinate or the recycling acid, and using AgNO with known concentration₃Titrating the solution;

s4, calculating Cl in waste acid raffinate or recovered acid^-1The concentration of (c).

In a further specific embodiment, the method comprises the following steps,

in S1, the method for preparing 0.5mol/L NaCl standard solution comprises the following steps: 1) a certain amount of NaCl reagent is taken and is placed in a drier after being kept warm for 2 hours and constant weight in a 600 ℃ oven, and then the NaCl reagent is cooled to room temperature for standby. 2) A certain amount of sodium chloride which has been constant in weight is weighed into a 100mL beaker and dissolved by adding water. 3) Transferring to a 1000mL volumetric flask, washing the small beaker and the transferred glass rod with deionized water for three times, and fixing the volume of the volumetric flask;

about 0.1M AgNO₃Solution: weighing a certain amount of silver nitrate reagent, dissolving in water, diluting to 1L, storing in a brown reagent bottle, and using after calibration.

In S2, AgNO₃Calibration: sucking a certain volume of 0.5mol/L sodium chloride standard solution, adding a proper amount of deionized water into a 100mL beaker, adding nitric acid for acidification, adding a starch solution (1g/100mL), and titrating with a silver nitrate solution to be calibrated.

AgNO₃The concentration of the solution is calculated by the formula:

wherein, V_{Terminal point}AgNO consumed for titration endpoint₃Volume of solution.

In S3, for Cl^-1Titration: sucking up a certain quantity of (V)_{Spent acid raffinate or recycled acid}) Adding deionized water into the waste acid residual liquid or the recovered acid in a 100mL beaker, titrating by using a standard silver nitrate solution, and titrating to consume AgNO₃Has a volume of

In S4, Cl is calculated^-1The formula of the concentration isNamely, it is

In a further scheme, in the step (2), the method for measuring the content of free acid, silicon and aluminum in the waste acid raffinate or the recovered acid comprises the following steps:

s1, preparing a potassium hydrogen phthalate standard solution and a sodium hydroxide solution with a certain concentration;

s2, calibrating the sodium hydroxide solution by adopting a potassium hydrogen phthalate standard solution, and calculating the accurate concentration of the sodium hydroxide solution;

s3, taking a certain volume of waste acid residual liquid or recovered acid, titrating with NaOH solution with known concentration until three titration end points appear in titration, and recording the volume V of NaOH consumed when the three titration end points are reached₁，V₂And V₃；

And S4, respectively calculating the contents of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid.

In a further aspect of the present invention,

in S1, the method for preparing the potassium hydrogen phthalate standard solution includes: 1) drying the potassium hydrogen phthalate reagent at the temperature of 100-125 ℃ for 1-2h, 2) cooling the reagent in a dryer to room temperature for later use, and 3) weighing a certain mass of potassium hydrogen phthalate and dissolving the potassium hydrogen phthalate in deionized water to prepare a 0.1M phthalic acid standard solution.

A NaOH solution was prepared at a concentration of about 0.5M: weighing a certain amount of NaOH, dissolving in deionized water, and preparing NaOH solution with the concentration of about 0.5M after constant volume.

Calibration of NaOH standard solution in S2: taking a certain volume of potassium hydrogen phthalate solution into a beaker, adding 50mL of deionized water, calibrating NaOH solution, and titrating to consume V NaOH_NaOHAnd calculating the real concentration of the NaOH standard solution.

In S2, the formula for calculating the concentration of the sodium hydroxide solution is C_NaOHV_NaOH＝C_{Potassium hydrogen phthalate}V_{Phthalic acidHydrogen potassium salt}I.e. by

Titration of free acid, silicon, aluminum in S3: taking a certain volume (V)_{Spent acid raffinate or recycled acid}) The waste acid raffinate or the recovered acid is added into a beaker, 50mL of deionized water is added, and titration is carried out by using NaOH standard solution. Adjusting V_{Spent acid raffinate or recycled acid}Until three titration endpoints appeared in the titration, the volume V of NaOH consumed to reach the three titration endpoints was recorded₁，V₂And V₃。

According to the method, the inflection point, namely the highest point of the potential-volume partial derivative function, is determined by a computer of the thunder magnetic potential titrator according to the potential-volume curve to determine the titration end point, namely the titration end point is recorded according to data automatically read by the thunder magnetic potential titrator.

In a further aspect of the present invention,

in S4, the formula for calculating the content of free acid is C_{Free acid}V_{Spent acid raffinate or recycled acid}＝C_NaOHV₁I.e. by

The formula for calculating the silicon content in the waste acid residual liquid or the recovered acid is 4C_SiV_{Spent acid raffinate or recycled acid}＝(V₂-V₁)C_NaOHI.e. by

The formula for calculating the aluminum content in the waste acid residual liquid or the recovered acid is 4C_AlV_{Spent acid raffinate or recycled acid}＝(V₃-V₂)C_NaOHI.e. by

The detection method can sequentially analyze and calculate the contents of free acid, silicon and aluminum in the waste acid residual liquid or the recovered acid through one-time titration, has simple, quick and convenient steps, and is suitable for industrial field analysis.

In the further scheme, in the step (3), the content of fluorine is calculated according to the principle of charge conservation, and the formula is

C_F＝C_{Free acid}+4C_Silicon+3C_Al-C_Cl-。

The invention also provides an application of the method for analyzing and detecting multiple components in the waste liquid or the recovered liquid of the mixed acid in the above scheme in the detection of acid liquid components for purifying the lithium ion battery negative electrode material.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. the potentiometric titration method is adopted to analyze and detect various components in the waste liquid or the recovered liquid of the mixed acid, and the Cl can be calculated by only needing two titrations in the whole process^-Free acid, Si, aluminum and fluorine, and the sample does not need extra treatment in the whole process, and the method can obtain a result at one time, is simple and rapid, has good repeatability and is suitable for industrial field analysis.

2. The analysis and detection method is suitable for detecting various components in waste liquid or recovery liquid of various mixed acids, and is particularly suitable for detecting acid liquid components for purifying lithium ion battery negative electrode materials.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without limiting the invention to the right. It is obvious that the drawings in the following description are only some embodiments, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:

FIG. 1 is a schematic process diagram of the analytical test method of the present invention.

It should be noted that the drawings and the description are not intended to limit the scope of the inventive concept in any way, but to illustrate it by a person skilled in the art with reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention.

It should be noted that the term "titration" as used herein refers to the quantitative reaction of two solutions to determine the content of a certain solute, and can be carried out by any method known in the art.

The invention specifically provides a method for analyzing and detecting multiple components in waste liquid or recovered liquid of mixed acid, waste acid residual liquid or recovered acid of the mixed acid is prepared, the waste liquid or the recovered liquid contains hydrofluoric acid, hydrochloric acid, silicon and aluminum components, the detection method comprises the steps of titrating and calculating the content of hydrofluoric acid, hydrochloric acid, silicon and aluminum, and the steps are as follows:

the first step is as follows: free Cl in waste acid raffinate or recovered acid^-The titration specifically comprises:

(1) preparing a 0.5M NaCl solution: 1) a certain amount of NaCl reagent is taken and is placed in a drier after being kept warm for 2 hours and constant weight in a 600 ℃ oven, and then the NaCl reagent is cooled to room temperature for standby. 2) A certain amount of sodium chloride which has been constant in weight is weighed into a 100mL beaker and dissolved by adding water. 3) Transferring to a 1000mL volumetric flask, washing the small beaker and the transferred glass rod with deionized water for three times, and fixing the volume of the volumetric flask;

(2) about 0.1M AgNO₃Solution: weighing a certain amount of silver nitrate, dissolving the silver nitrate in water, diluting to 1L, storing in a brown reagent bottle, and using after calibration;

(3)AgNO₃calibration: sucking 0.5mol/L sodium chloride standard solution with a certain volume, adding a proper amount of deionized water into a 100mL beaker, adding nitric acid for acidification, adding a starch solution (1g/100mL), and titrating with a silver nitrate solution to be calibrated;

(4) calculating the concentration of the silver nitrate solution according to the formula

(5) To Cl^-1Titration: sucking up a certain quantity of (V)_{Spent acid raffinate or recycled acid}) Adding deionized water into the waste acid residual liquid or the recovered acid in a 100mL beaker, titrating by using a standard silver nitrate solution, and titrating to consume AgNO₃Has a volume of

(6) Calculating Cl in waste acid raffinate or recovered acid^-1The formula is

The ion reaction involved is as follows:

NaCl+AgNO₃＝AgCl↓+NaNO₃

the second step is that: the titration of free acid, silicon and aluminum in waste acid residual liquid or recovered acid specifically comprises,

(1) preparing a potassium hydrogen phthalate standard solution: 1) drying the potassium hydrogen phthalate reagent at the temperature of 100-125 ℃ for 1-2h, 2) cooling the reagent in a dryer to room temperature for later use, and 3) weighing a certain mass of potassium hydrogen phthalate and dissolving the potassium hydrogen phthalate in deionized water to prepare a 0.1mol/L phthalic acid standard solution.

(2) Preparing a NaOH solution with the concentration of about 0.5 mol/L: weighing a certain amount of NaOH, dissolving the NaOH in deionized water, and preparing NaOH solution with the concentration of about 0.5mol/L after constant volume;

(3) and (3) calibrating NaOH standard solution: taking a certain volume of potassium hydrogen phthalate solution into a beaker, adding 50mL of deionized water, calibrating NaOH solution, and titrating to consume V NaOH_NaOHCalculating the real concentration of the NaOH standard solution;

the formula for calculating the concentration of the sodium hydroxide solution is C_NaOHV_NaOH＝C_{Phthalic anhydridePotassium hydrogen acid}V_{Potassium hydrogen phthalate}I.e. by

(4) Titration of free acid, silicon, aluminum: taking a certain volume (V)_{Spent acid raffinate or recycled acid}) The waste acid raffinate or the recovered acid is added into a beaker, 50mL of deionized water is added, and titration is carried out by using NaOH standard solution. Adjusting V_{Spent acid raffinate or recycled acid}Until three titration endpoints appeared in the titration, the volume V of NaOH consumed to reach the three titration endpoints was recorded₁，V₂And V₃；

In the invention, the volume of waste acid residual liquid or recovered acid is required to be adjusted to be proper so as to be convenient for dropping the NaOH standard solution at regular time and three titration end points can be generated at intervals. If the volume of the waste acid residual liquid or the recovered acid is too small, a small amount of sodium hydroxide is dripped into the waste acid residual liquid or the recovered acid, the reaction is continuously completed, the interval time is too short, and three titration end points cannot be distinguished; if the volume of the waste acid residual liquid or the recycled acid is too large, the consumption of NaOH solution is too much, and the consumption of time is too long, so that waste is caused.

Specifically, take 0.2mL (V)_{Spent acid raffinate or recycled acid}) Adding 50mL of deionized water into the waste acid residual liquid or the recovered acid in a beaker, and dripping NaOH standard solution into the beaker;

first, OH^-Reacting with free acid in waste acid raffinate or recycled acid, reaching a first titration end point when the free acid completely reacts with sodium hydroxide, and recording the volume V of consumed NaOH₁；

The chemical reaction formula is as follows:

a.HCl+NaOH＝NaCl+H₂O

b.HF+NaOH＝NaF+H₂O

c.H₂SiF₆+2NaOH＝Na₂SiF₆+2H₂O

then, NaOH standard solution, OH is continuously added dropwise^-Reacting with Si in the waste acid raffinate or the recovered acid, and when the silicon element in the solution is completely converted into Si (OH)₄When a second titration endpoint is reached, the consumption is recordedVolume V of NaOH consumed₂；

The chemical reaction formula is as follows:

Na₂SiF₆+4NaOH＝Si(OH)₄+6NaF＝SiO₂+6NaF+H₂O

finally, the NaOH standard solution, OH, is continuously added dropwise^-Reacting with Al element in waste acid raffinate or recovered acid, and when the Al element is completely converted into AlO₂ ^-When the third titration end point is reached, the volume V of NaOH consumed is recorded₃；

The chemical reaction formula is as follows:

(5) calculation of free acid, silicon, aluminium concentration:

1)C_{free acid}V_{Spent acid raffinate or recycled acid}＝C_NaOHV₁，

2)4C_SiV_{Spent acid raffinate or recycled acid}＝(V₂-V₁)C_NaOH，

3)4C_AlV_{Spent acid raffinate or recycled acid}＝(V₃-V₂)C_NaOH，

Then it is determined that,

the third step is to calculate the fluorine content according to the charge conservation with the formula C_F＝C_{Free hydrogen}+4C_Silicon+3C_Al-C_Cl-。

The method can be realized by the method in the prior art, can be realized by manual detection and can also be realized by adopting an instrument for detection, and the difference lies in the difference of the precision. In order to make the detection result more accurate, an instrument can be used for detection. As a preferable scheme, the titration process of the invention is detected by a potentiometric titration mode of a thunder magnetic automatic titrator, and the titration end point is calculated by a computer. As a specific scheme, the device and parameters for detection in the potentiometric titration mode of the thunder magnetic automatic titrator are as follows:

devices adopted

Device parameter setting

(1) The stirrer is always turned on in the titration process, and the rotating speed is 20 r/min;

(2) performing blank titration before formal titration;

(3) the parameter settings for the titration are typically:

1) type of titration: the invention uses phthalic acid to calibrate sodium hydroxide solution and uses sodium hydroxide to titrate the titration type of free acid to select 'PH', and the rest titrations select 'mV';

2) the stabilization time is set for 6 s;

3) the mode of adding volume is selected, if the approximate concentration of the substance can be judged, a certain volume of solution with known concentration can be pre-added, and if the concentration is uncertain, the pre-adding is not selected;

4) volume per addition: the evaluation needs to be pre-judged according to the titration error. eg: to control the titration error at 1%, the titration process titrates 100 drops of known solution, and if 4mL drops are expected by the titration process, the volume of each addition can be set to 0.04 mL.

5) The number of the end points does not need to be set;

6) the amount of the jump is set to 1.

Example 1

As shown in fig. 1, this example provides a method for detecting the content of each component in waste acid residual liquid after purification by a mixed acid method for a negative electrode material of a lithium ion battery. The thunder magnetic automatic titrator is adopted for detection. The components in the waste acid residual liquid mainly comprise free acid and Cl^-F, Si, Al. The specific testing steps are as follows,

the first step is as follows: free Cl in waste acid raffinate or recovered acid^-The titration specifically comprises:

(1) preparing a 0.5M NaCl solution: 1) taking a certain amount of NaCl reagent, keeping the temperature in a 600 ℃ oven for 2 hours, keeping the weight constant, and then placing the NaCl reagent in a drier to cool the NaCl reagent to room temperature for later use; 2) 29.250g of sodium chloride NaCl, which has been weighed to a constant weight, are weighed into a 100mL beaker and dissolved in water. 3) Transferring to a 1L volumetric flask, washing the small beaker and the transferred glass rod with deionized water for three times, and fixing the volume of the volumetric flask;

(2) about 0.1M AgNO₃Solution: weighing 16.987g of silver nitrate, dissolving in water, diluting to 1L, storing in a brown reagent bottle, and using after calibration;

(3)AgNO₃calibration: sucking 1mL of 0.5mol/L sodium chloride standard solution, adding a proper amount of deionized water into a 100mL beaker, adding nitric acid for acidification, adding a starch solution (1g/100mL), and titrating with a silver nitrate solution to be calibrated until the total AgNO consumption of the titration end point₃4.971mL of solution;

(4) calculating the concentration of the silver nitrate solution according to the formula

(5) To Cl^-1Titration: aspirate 50mL of (V)_{Spent acid raffinate or recycled acid}) The residual waste acid or the recovered acid is titrated by a standard silver nitrate solution in a 100mL beaker, and AgNO is consumed by titration₃Has a volume of

(6) Calculating Cl in waste acid raffinate or recovered acid^-1The formula is

The second step is that: the titration of free acid, silicon and aluminum in waste acid residual liquid or recovered acid specifically comprises,

(1) preparing a potassium hydrogen phthalate standard solution: the potassium hydrogen phthalate reagent should be dried at 100-125 ℃ for 1-2h and then cooled to room temperature in a dryer. 20.422g of potassium hydrogen phthalate is weighed and dissolved in 1L of deionized water to prepare 0.1M phthalic acid standard solution;

(2) about 0.5M NaOH solution was prepared: 19.998g of NaOH is weighed and dissolved in deionized water, and after constant volume, 1L of NaOH solution with the concentration of about 0.5M is prepared;

(3) and (3) calibrating NaOH standard solution: taking 10mL of potassium hydrogen phthalate solution, adding 40mL of deionized water and NaOH solution into a beaker for calibration, titrating the volume V of consumed NaOH_NaOHCalculating the real concentration of the NaOH standard solution to be 2mL,

(4) titration of free acid, silicon, aluminum: take 0.2mL (V)_{Spent acid raffinate or recycled acid}) The waste acid raffinate or the recovered acid is added into a beaker, 50mL of deionized water is added, and titration is carried out by using NaOH standard solution. Adjusting V_{Spent acid raffinate or recycled acid}Until three titration endpoints appeared for the titration, the volumes of NaOH consumed to reach the three titration endpoints were recorded as: v₁2.946mL, V₂4.345mL, V₃4.700 mL;

the concentrations of free acid, silicon, aluminum were calculated using the following formula:

the calculated contents of free acid, Si and Al in the waste acid are 7.365mol/L, 0.874mol/L and 0.222mol/L respectively.

The third step is to calculate the fluorine content according to the charge conservation with the formula C_F＝C_{Free hydrogen}+4C_Silicon+3C_Al-C_Cl-The fluorine content was calculated to be 11.482 mol/L.

Example 2

As another embodiment of the present invention, this embodiment provides a method for detecting the content of each component in a waste acid raffinate after purification by a mixed acid method for a negative electrode material of a lithium ion battery, which is the same as that described in embodiment 1, except that in this embodiment, the waste acid raffinate is selected differently. The specific detection steps are as follows:

the first step is as follows: free Cl in waste acid residual liquid^-The titration specifically comprises:

(1) preparing 0.5mol/L NaCl solution and 0.1mol/L AgNO₃Solution of p-AgNO₃The solution is calibrated, and the calculated silver nitrate solution concentration is completely consistent with the corresponding steps of the example 1.

(2) To Cl^-1Titration: aspirate 0.2mL of (V)_{Spent acid raffinate or recycled acid}) The residual waste acid or the recovered acid is titrated by a standard silver nitrate solution in a 100mL beaker, and AgNO is consumed by titration₃Has a volume of6.266 mL.

(3) Calculating Cl in waste acid raffinate or recovered acid^-1The formula is

The second step is that: the titration of free acid, silicon and aluminum in waste acid residual liquid or recovered acid specifically comprises,

(1) preparing a potassium hydrogen phthalate standard solution and a NaOH solution, wherein the calibration of the NaOH solution is completely consistent with the corresponding steps of the embodiment 1;

(2) titration of free acid, silicon, aluminum: take 0.2mL (V)_{Spent acid raffinate or recycled acid}) The waste acid raffinate or the recovered acid is added into a beaker, 50mL of deionized water is added, and titration is carried out by using NaOH standard solution. Adjusting V_{Spent acid raffinate or recycled acid}Until three titration endpoints appeared for the titration, the volumes of NaOH consumed to reach the three titration endpoints were recorded as: v₁2.113mL, V₂3.121mL, V₃5.323 mL;

the concentrations of free acid, silicon, aluminum were calculated using the following formula:

calculating the fluorine content according to the conservation of charge, wherein the formula is C_F＝C_{Free hydrogen}+4C_Silicon+3C_Al-C_ClCalculating the fluorine content.

(3) The calculated contents of free acid, Si, Al and F in the waste acid are 5.282mol/L, 0.63mol/L, 1.376mol/L and 8.778mol/L respectively.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.