A method for analyzing and detecting multiple components in waste liquid or recovered liquid of mixed acid

Abstract

The present invention discloses a method for analyzing and detecting multiple components in a waste liquid or a recovered acid of a mixed acid, comprising preparing a waste acid residual liquid or a recovered acid of the mixed acid, wherein the detection method comprises determining the contents of hydrofluoric acid, hydrochloric acid, silicon, and aluminum therein, and the steps are as follows: (1) determining Cl in the waste acid residual liquid or the recovered acid ‑ (2) Determine the content of free acid, silicon and aluminum in the waste acid residue or recovered acid; (3) Calculate the content of fluorine according to the law of charge conservation. The present invention uses a potentiometric titration method to analyze and detect multiple components in the waste acid or recovered liquid of the mixed acid. The whole process only requires two titrations to calculate the Cl ‑ , free acid, Si, aluminum, and fluorine content. The sample does not need additional treatment during the whole process, and the results are obtained in one time. It is simple, fast, and has good repeatability, making it suitable for industrial analysis.

Description

Technical Field

[0001] The invention belongs to the field of waste liquid analysis and detection, and in particular relates to a method for analyzing and detecting multiple components in waste liquid or recovered liquid of mixed acid. Background Art

[0002] Graphite used as negative electrode material for lithium-ion batteries requires high purity and low impurities. Therefore, a matching purification process is needed to reduce the impurity content in graphite. At present, many companies use the mixed acid method to remove impurities in negative electrode materials. The mixed acid method is the most effective, lowest cost and most polluting method in the purification process of negative electrode materials. In order to reduce pollution to the environment and maximize the use of acid, the applicant intends to adopt membrane separation technology to realize the recovery and reuse of hydrochloric acid and hydrofluoric acid based on the mixed acid purification method. However, in actual operation, there are waste acid residues or the recovered acid components are complex (mainly including free acid, Cl - , F, Si, Al, etc.) and the content is unknown, so it is impossible to clearly determine the free acid depletion, recovered acid components and content. Therefore, it is necessary to develop a simple, convenient and easy-to-operate detection method to monitor such solutions.

[0003] In the prior art, Han Libin et al. tested the content of the components of the mixed acid system containing phosphoric acid, hydrofluoric acid and sulfuric acid by using thymolphthalein as the first-stage titration indicator, calcium chloride solution as the precipitant, and thymolphthalein as the second-stage titration indicator, and obtained relatively accurate analysis results. Yang Yichao et al. of Yangzhou Municipal Health and Epidemic Prevention Station developed a "HF, HCl, H 2 SO 4 Yang Huiru et al. reported the potentiometric titration, electrode method, precipitation method, acid-base titration method, etc. applicable to the mixed system of hydrofluoric acid and sulfuric acid. Antje Henβge et al. reported the determination of HNO by two-step titration using potentiometric titration. 3 , HF, H 2 SiO 4 Content of each component in mixed acid. Although there are explorations on detection methods for simple mixed acid systems, there are currently no reports on industrial analytical methods for detecting the content of each component in solutions containing HCl, HF, Si, and Al.

[0004] At present, in the more advanced analytical test means, although anions can be monitored by ion chromatography, the instrument cost of this method is high, the operator requirements are high, the operation process is complicated and the dilution process is prone to introduce errors, which is not suitable for industrial field analysis. Cations can be detected by plasma emission spectrometry, but this method also has the above-mentioned shortcomings. In addition, since hydrofluoric acid can dissolve pipelines (containing silicon), the above method not only damages the equipment, but also increases the inaccuracy of silicon detection. Therefore, it is necessary to propose a simple, convenient and fast analytical detection method for multi-components in the waste liquid or recovered liquid of mixed acid.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for analyzing and detecting multiple components in mixed acid waste liquid or recovered acid. The present invention adopts a potentiometric titration method (Raymagnetic automatic titrator) to test the content of each component in the waste acid residue or recovered acid. Only two titration steps are required in the whole process to calculate Cl - , free acid, Si, aluminum, and fluorine content. The sample does not need to be processed during the entire process, and the results are obtained in one go, which is simple, fast, and has good repeatability.

[0007] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0008] The first object of the present invention is to provide a method for analyzing and detecting multiple components in a waste liquid or a recovered liquid of a mixed acid, comprising: preparing a waste acid residue of a mixed acid or a recovered acid, wherein the detection method comprises titrating and calculating the contents of hydrofluoric acid, hydrochloric acid, silicon, and aluminum therein, and the steps are as follows:

[0009] (1) Determination of Cl in waste acid residue or recovered acid - Content;

[0010] (2) Determine the content of free acid, silicon and aluminum in the waste acid residue or recovered acid;

[0011] (3) Calculate the fluorine content based on the principle of charge conservation.

[0012] The mixed acid purification method is a method of acid washing and purifying the negative electrode material precursor with a mixed solution of hydrochloric acid and hydrofluoric acid at a certain concentration. Since the mixed acid solution after purification still contains a large amount of hydrochloric acid and hydrofluoric acid, in order to reduce production costs, the effective components in the waste acid residue can be recycled and reused. If the concentration of free acid in the recovered acid is unclear, it will affect the reusability of the recovered acid; if the content of the components in the recovered acid is unclear, the recovered acid cannot be adjusted to a usable acid. The waste acid components were tested by ion chromatograph and inductively coupled plasma emission spectrometer (ICP), and it was found that the mixed acid residue after acid washing and purification mainly contained free acid, Cl- , F, Si, Al and other components (it should be noted that F, Si, Al exist in complex forms in the solution, not only in the form of single ions, and are uniformly represented by the symbols of the elements in this application). The above two test methods have the following characteristics: 1) high instrument cost; 2) relatively complicated operation, easy to introduce errors; 3) require special personnel to operate and maintain, which is relatively professional, making it unsuitable for non-knowledge-intensive enterprises. Therefore, there is an urgent need to develop a set of industrial analysis methods suitable for the analysis of multi-component mixed acid components.

[0013] Based on the idea of ​​developing a method for analyzing the composition of multi-component mixed acids, the present invention provides a method for accurately detecting the contents of hydrofluoric acid, hydrochloric acid, silicon, aluminum, and fluorine in waste acid residue and recovered acid. On the one hand, the concentration of free acid can be determined to facilitate the recovery of acid for reuse; on the other hand, the content of each component can be determined to facilitate adjustment to usable acid. The analytical detection method of the present invention can calculate Cl by two titrations. - , free acid, Si, aluminum, and fluorine content. The sample does not need to be processed during the entire process and the results are obtained in one time. It is simple and fast with good repeatability and high accuracy.

[0014] The analytical detection method of the present invention is suitable for detecting the content of various components in various mixed solutions containing hydrofluoric acid, hydrochloric acid, silicon and aluminum, and is particularly suitable for detecting the components of acid solution used for purifying negative electrode materials of lithium ion batteries.

[0015] In a further embodiment, in step (1), the Cl content in the waste acid residue or the recovered acid is determined. - Methods for content include:

[0016] S1, prepare NaCl standard solution and a certain concentration of AgNO 3 Solution;

[0017] S2, use NaCl standard solution to calibrate AgNO 3 Solution, calculate the exact concentration of silver nitrate solution;

[0018] S3, add a certain amount of waste acid residue or recovered acid to deionized water and use a known concentration of AgNO 3 The solution is titrated;

[0019] S4, calculate the Cl in the waste acid residue or recovered acid -1 concentration.

[0020] For more specific plans,

[0021] In S1, the method for preparing a 0.5 mol / L NaCl standard solution includes: 1) taking a certain amount of NaCl reagent and keeping it in a 600°C oven for 2 hours to a constant weight, placing it in a desiccator, and cooling it to room temperature for use. 2) weighing a certain amount of sodium chloride that has been weighed to a constant weight into a 100mL beaker, and adding water to dissolve it. 3) transferring it to a 1000mL volumetric flask, rinsing the small beaker and the transferred glass rod with deionized water three times, and then the volumetric flask is fixed to volume;

[0022] The concentration was limited to 0.1 M AgNO 3 Solution: Weigh a certain amount of silver nitrate reagent and dissolve it in water, dilute to 1L, store in a brown reagent bottle and use after calibration.

[0023] In S2, AgNO 3 Calibration: Pipette a certain volume of 0.5 mol / L sodium chloride standard solution into a 100 mL beaker, add appropriate amount of deionized water, add nitric acid to acidify, then add starch solution (1 g / 100 mL), and then titrate with the silver nitrate solution to be calibrated.

[0024] AgNO 3 The formula for calculating the concentration of the solution is:

[0025] Among them, V 终点 AgNO consumed at the titration endpoint 3 The volume of the solution.

[0026] In S3, Cl -1 Titration: Take a certain amount of (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a 100mL beaker, add deionized water, and titrate with standard silver nitrate solution. The titration consumes AgNO 3 The volume is

[0027] In S4, calculate Cl -1 The concentration formula is Right now

[0028] In a further embodiment, in step (2), the method for determining the content of free acid, silicon and aluminum in the waste acid residue or the recovered acid comprises:

[0029] S1, prepare potassium hydrogen phthalate standard solution and sodium hydroxide solution of a certain concentration;

[0030] S2, using potassium hydrogen phthalate standard solution to calibrate the sodium hydroxide solution and calculate the accurate concentration of the sodium hydroxide solution;

[0031] S3, take a certain volume of waste acid residue or recovered acid, and titrate it with a NaOH solution of known concentration until three titration endpoints appear, and record the volume V of NaOH consumed to reach the three titration endpoints. 1 , V 2 and V 3 ;

[0032] S4, calculate the contents of free acid, silicon and aluminum in the waste acid residue or recovered acid respectively.

[0033] Further solutions,

[0034] In S1, the method for preparing a potassium hydrogen phthalate standard solution includes: 1) drying the potassium hydrogen phthalate reagent at 100-125° C. for 1-2 hours, 2) cooling it to room temperature in a dryer for later use, and 3) weighing a certain mass of potassium hydrogen phthalate and dissolving it in deionized water to prepare a 0.1 M phthalic acid standard solution.

[0035] Prepare a NaOH solution with a concentration of approximately 0.5 M: weigh a certain amount of NaOH and dissolve it in deionized water. After constant volume, a NaOH solution with a concentration of approximately 0.5 M is obtained.

[0036] In S2, the standardization of NaOH standard solution: take a certain volume of potassium hydrogen phthalate solution in a beaker, add 50mL of deionized water, and standardize with NaOH solution. The volume of NaOH consumed in the titration is V. NaOH , calculate the true concentration of the NaOH standard solution.

[0037] In S2, the formula for calculating the concentration of sodium hydroxide solution is C NaOH V NaOH =C 邻苯二甲酸氢钾 V 邻苯二甲酸氢钾 ,Right now

[0038] In S3, titration of free acid, silicon and aluminum: take a certain volume (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a beaker, add 50mL of deionized water, and titrate with a standard NaOH solution. Adjust V 废酸残液或回收酸 Until three titration endpoints appear, record the volume V of NaOH consumed to reach the three titration endpoints 1 , V 2 and V 3 .

[0039] In the present invention, the computer of the Leiji automatic titrator determines the inflection point based on the potential-volume curve, that is, the highest point of the partial derivative function of potential-volume to determine the titration end point. In other words, the titration end point can be recorded based on the data automatically read out by the Leiji potentiometric titrator.

[0040] Further solutions,

[0041] In S4, the formula for calculating the free acid content is C 游离酸 V 废酸残液或回收酸 =C NaOH V 1 ,Right now

[0042] The formula for calculating the silicon content in the waste acid residue or recovered acid is 4C Si V 废酸残液或回收酸 =(V 2 -V 1 )C NaOH ,Right now

[0043] The formula for calculating the aluminum content in the waste acid residue or recovered acid is 4C Al V 废酸残液或回收酸 =(V 3 -V 2 )C NaOH ,Right now

[0044] The detection method of the present invention 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 titration. The steps are simple, fast and convenient, and the method is suitable for industrial on-site analysis.

[0045] In a further embodiment, in step (3), the fluorine content is calculated according to the charge conservation principle, and the formula is:

[0046] C F =C 游离酸 +4C 硅 +3C Al -C Cl -.

[0047] The second object of the present invention is to provide an analytical detection method for multiple components in the waste liquid or recovered liquid of the mixed acid as described in the above scheme, and to use it in the detection of acid solution components for purification of negative electrode materials for lithium-ion batteries.

[0048] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0049] 1. The potentiometric titration method of the present invention is used to analyze and detect multiple components in the waste liquid or recovered liquid of the mixed acid. The whole process only requires two titrations to calculate Cl - , free acid, Si, aluminum, and fluorine content. During the whole process, the sample does not need additional treatment and the results are obtained in one time. It is simple, fast, and has good repeatability, and is suitable for industrial on-site analysis.

[0050] 2. The analytical detection method of the present invention is suitable for detecting multiple components in waste liquid or recovered liquid of various mixed acids, and is particularly suitable for detecting acid components used for purification of negative electrode materials for lithium-ion batteries.

[0051] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings:

[0053] Figure 1 It is a process schematic diagram of the analysis and detection method of the present invention.

[0054] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0055] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0056] It should be noted that the "titration" mentioned in the present invention refers to determining the content of a certain solute by a quantitative reaction between two solutions, which can be implemented by a specific method already available in the prior art.

[0057] The present invention specifically provides a method for analyzing and detecting multiple components in a waste liquid or a recovered liquid of a mixed acid, preparing a waste acid residual liquid or a recovered acid of a mixed acid, wherein the waste liquid or the recovered liquid contains hydrofluoric acid, hydrochloric acid, silicon, and aluminum components, and the detection method comprises titrating and calculating the contents of the hydrofluoric acid, hydrochloric acid, silicon, and aluminum therein, and the steps are as follows:

[0058] Step 1: Free Cl in waste acid residue or recovered acid - The titration includes:

[0059] (1) Prepare 0.5M NaCl solution: 1) Take a certain amount of NaCl reagent and keep it in a 600℃ oven for 2 hours until it reaches constant weight, then place it in a desiccator and cool it to room temperature for later use. 2) Weigh a certain amount of sodium chloride that has reached constant weight into a 100mL beaker and add water to dissolve it. 3) Transfer it to a 1000mL volumetric flask, rinse the small beaker and the transferred glass rod three times with deionized water, and the volumetric flask is ready;

[0060] (2) The formulation is limited to 0.1 M AgNO 3 Solution: Weigh a certain amount of silver nitrate and dissolve it in water, dilute to 1L, store in a brown reagent bottle, and use after calibration;

[0061] (3) AgNO 3 Calibration: Take a certain volume of 0.5mol / L sodium chloride standard solution, put it in a 100mL beaker, add appropriate amount of deionized water, add nitric acid to acidify, then add starch solution (1g / 100mL), and then titrate with the silver nitrate solution to be calibrated;

[0062] (4) Calculate the concentration of silver nitrate solution using the formula:

[0063] (5) Cl -1 Titration: Take a certain amount of (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a 100mL beaker, add deionized water, and titrate with standard silver nitrate solution. The titration consumes AgNO 3 The volume is

[0064] (6) Calculation of Cl in waste acid residue or recovered acid -1 The concentration formula is:

[0065] The ion reaction equations involved are as follows:

[0066] NaCl+AgNO 3 =AgCl↓+NaNO 3

[0067] Step 2: Titration of free acid, silicon and aluminum in waste acid residue or recovered acid, including:

[0068] (1) Preparation of potassium hydrogen phthalate standard solution: 1) Potassium hydrogen phthalate reagent should be dried at 100-125℃ for 1-2h; 2) Cool to room temperature in a desiccator for later use; 3) Weigh a certain amount of potassium hydrogen phthalate and dissolve it in deionized water to prepare a 0.1 mol / L phthalic acid standard solution.

[0069] (2) Prepare a NaOH solution with a concentration of about 0.5 mol / L: Weigh a certain amount of NaOH and dissolve it in deionized water to obtain a NaOH solution with a concentration of about 0.5 mol / L.

[0070] (3) Calibration of NaOH standard solution: Take a certain volume of potassium hydrogen phthalate solution in a beaker, add 50 mL of deionized water, and calibrate with NaOH solution. The volume of NaOH consumed in the titration is V. NaOH , calculate the true concentration of the NaOH standard solution;

[0071] The formula for calculating the concentration of sodium hydroxide solution is C NaOH V NaOH =C 邻苯二甲酸氢钾 V 邻苯二甲酸氢钾 ,Right now

[0072] (4) Titration of free acid, silicon and aluminum: Take a certain volume (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a beaker, add 50mL of deionized water, and titrate with a standard NaOH solution. Adjust V 废酸残液或回收酸 Until three titration endpoints appear, record the volume V of NaOH consumed to reach the three titration endpoints 1 , V 2 and V 3 ;

[0073] In the present invention, it is necessary to adjust and explore to make the volume of the waste acid residue or the recovered acid appropriate so that three titration end points can appear at intervals when titrating with the NaOH standard solution. If the volume of the waste acid residue or the recovered acid is too small, after a small amount of sodium hydroxide is dripped in, the reaction is completed continuously, the interval time is too short, and the three titration end points cannot be distinguished; if the volume of the waste acid residue or the recovered acid is too large, too much NaOH solution is consumed, and the time is too long, resulting in waste.

[0074] Specifically, take 0.2mL (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a beaker, add 50mL of deionized water, and drop the NaOH standard solution into the beaker;

[0075] First, OH - React with the free acid in the waste acid residue or the recovered acid. When the free acid reacts completely with sodium hydroxide, the first titration endpoint is reached and the volume V of NaOH consumed is recorded. 1 ;

[0076] The chemical reaction involved is:

[0077] a.HCl+NaOH=NaCl+H 2 O

[0078] b. HF + NaOH = NaF + H 2 O

[0079] H 2 SiF 6 +2NaOH=Na 2 SiF 6 +2H 2 O

[0080] Then, continue to add NaOH standard solution, OH - Reacts with Si in waste acid residue or recovered acid. When all silicon in the solution is converted into Si(OH) 4 When the second titration endpoint is reached, the volume of NaOH consumed V is recorded. 2 ;

[0081] The chemical reaction involved is:

[0082] Na 2 SiF 6 +4NaOH=Si(OH) 4 +6NaF=SiO 2 +6NaF+H 2 O

[0083] Finally, continue to add NaOH standard solution, OH - React with the Al element in the waste acid residue or recovered acid. When all the Al element is converted into AlO 2 - When the third titration endpoint is reached, the volume of NaOH consumed V is recorded. 3 ;

[0084] The chemical reaction involved is:

[0085]

[0086] (5) Calculation of free acid, silicon and aluminum concentrations:

[0087] 1) C 游离酸 V 废酸残液或回收酸 =C NaOH V 1 ,

[0088] 2) 4C Si V 废酸残液或回收酸 =(V 2 -V 1 )C NaOH ,

[0089] 3) 4C Al V 废酸残液或回收酸 =(V 3 -V 2 )CNaOH ,

[0090] So,

[0091] The third step is to calculate the fluorine content according to the charge conservation law, the formula is C F =C 游离氢 +4C 硅 +3C Al -C Cl- .

[0092] The method of the present invention can be implemented by the method of the prior art, and can be detected manually or by instrument detection, and the difference lies in the difference in accuracy. In order to make the detection result more accurate, instrument detection can be used. As a preferred solution, the titration process of the present invention is detected by the potentiometric titration mode of the Lei magnetic automatic titrator, and the titration end point is calculated by a computer. As a specific solution, the device and parameters for detection by the potentiometric titration mode of the Lei magnetic automatic titrator are as follows:

[0093] Device used

[0094]

[0095] Device parameter settings

[0096] (1) During the titration process, the stirrer is always turned on at a speed of 20 r / min;

[0097] (2) A blank titration should be performed before the formal titration;

[0098] (3) The parameters of titration are generally:

[0099] 1) Titration type: The titration type for the present invention to use phthalic acid to calibrate sodium hydroxide solution and to use sodium hydroxide to titrate free acid is selected as "PH", and the other titrations are selected as "mV";

[0100] 2) Set the stabilization time to 6s;

[0101] 3) The choice of adding volume: if you can determine the approximate concentration of the substance, you can choose to pre-add a certain volume of a solution with a known concentration. If you are not sure, do not choose to pre-add.

[0102] 4) Volume added each time: This needs to be estimated based on the titration error. For example, if the titration error is to be controlled at 1%, 100 drops of a known solution should be titrated during the titration process. If 4 mL is expected to be dropped during the titration process, the volume added each time can be set to 0.04 mL.

[0103] 5) The number of endpoints does not need to be set;

[0104] 6) Set the jump amount to 1.

[0105] Example 1

[0106] like Figure 1 As shown, this embodiment provides a method for detecting the content of each component in the waste acid residue after the negative electrode material of the lithium ion battery is purified by the mixed acid method. The above-mentioned Lei magnetic automatic titrator is used for detection. The components in the waste acid residue mainly include free acid, Cl - , F, Si, Al. The specific test steps are as follows:

[0107] Step 1: Free Cl in waste acid residue or recovered acid - The titration includes:

[0108] (1) Prepare 0.5M NaCl solution: 1) Take a certain amount of NaCl reagent and keep it in a 600℃ oven for 2 hours until it is constant weight, then place it in a desiccator and cool it to room temperature for later use; 2) Weigh 29.250g of the constant weight sodium chloride NaCl into a 100mL beaker and add water to dissolve it. 3) Transfer it to a 1L volumetric flask, rinse the beaker and the transferred glass rod with deionized water three times, and the volumetric flask is ready;

[0109] (2) The formulation is limited to 0.1 M AgNO 3 Solution: Weigh 16.987g of silver nitrate and dissolve it in water, dilute to 1L, store in a brown reagent bottle and use after calibration;

[0110] (3) AgNO 3 Calibration: Pipette 1 mL of 0.5 mol / L sodium chloride standard solution into a 100 mL beaker, add appropriate amount of deionized water, add nitric acid to acidify, then add starch solution (1 g / 100 mL), and then titrate with the silver nitrate solution to be calibrated until the titration endpoint consumes a total of AgNO 3 Solution 4.971mL;

[0111] (4) Calculate the concentration of silver nitrate solution using the formula:

[0112] (5) Cl -1 Titration: Pipette 50mL of (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid is placed in a 100 mL beaker and titrated with standard silver nitrate solution. The titration consumes AgNO 3 The volume is

[0113] (6) Calculation of Cl in waste acid residue or recovered acid -1 The concentration formula is:

[0114] Step 2: Titration of free acid, silicon and aluminum in waste acid residue or recovered acid, including:

[0115] (1) Preparation of potassium hydrogen phthalate standard solution: Potassium hydrogen phthalate reagent should be dried at 100-125℃ for 1-2h, and then cooled to room temperature in a desiccator. Weigh 20.422g of potassium hydrogen phthalate and dissolve it in 1L of deionized water to prepare a 0.1M phthalic acid standard solution;

[0116] (2) Prepare 0.5 M NaOH solution: weigh 19.998 g of NaOH and dissolve it in deionized water. After constant volume, 1 L of NaOH solution with a concentration of approximately 0.5 M is prepared.

[0117] (3) Calibration of NaOH standard solution: Take 10 mL of potassium hydrogen phthalate solution in a beaker, add 40 mL of deionized water, and calibrate with NaOH solution. The volume of NaOH consumed in titration is V NaOH is 2mL, calculate the true concentration of the NaOH standard solution,

[0118] (4) Titration of free acid, silicon and aluminum: Take 0.2 mL (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a beaker, add 50mL of deionized water, and titrate with a standard NaOH solution. Adjust V 废酸残液或回收酸 Until the titration reaches three titration endpoints, record the volume of NaOH consumed to reach the three titration endpoints: V 1 2.946mL, V 2 4.345mL, V 3 4.700mL;

[0119] The concentrations of free acid, silicon, and aluminum were calculated using the following formula:

[0120]

[0121] The calculated contents of free acid, Si and Al in the waste acid are 7.365 mol / L, 0.874 mol / L and 0.222 mol / L respectively.

[0122] The third step is to calculate the fluorine content according to the charge conservation law, the formula is C F =C 游离氢 +4C 硅 +3C Al -C Cl- , the calculated fluorine content is 11.482 mol / L.

[0123] Example 2

[0124] As another embodiment of the present invention, this embodiment provides a method for detecting the content of each component in the waste acid residual liquid after the mixed acid method is used to purify the negative electrode material of the lithium ion battery. The detection method is the same as the method described in Example 1, except that in this embodiment, the waste acid residual liquid is different. The specific detection steps are as follows:

[0125] Step 1: Free Cl in the waste acid residue - The titration includes:

[0126] (1) Prepare 0.5 mol / L NaCl solution and 0.1 mol / L AgNO 3 Solution, for AgNO 3 The solution was calibrated and the concentration of the silver nitrate solution was calculated in exactly the same manner as in Example 1.

[0127] (2) Cl -1 Titration: Pipette 0.2 mL of (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid is placed in a 100 mL beaker and titrated with standard silver nitrate solution. The titration consumes AgNO 3 The volume is It is 6.266mL.

[0128] (3) Calculation of Cl in waste acid residue or recovered acid -1 The concentration formula is:

[0129] Step 2: Titration of free acid, silicon and aluminum in waste acid residue or recovered acid, including:

[0130] (1) Preparation of potassium hydrogen phthalate standard solution and NaOH solution. The calibration of NaOH solution is completely consistent with the corresponding steps in Example 1.

[0131] (2) Titration of free acid, silicon and aluminum: Take 0.2 mL (V 废酸残液或回收酸 ) of the waste acid residue or the recovered acid in a beaker, add 50mL of deionized water, and titrate with a standard NaOH solution. Adjust V 废酸残液或回收酸 Until the titration reaches three titration endpoints, record the volume of NaOH consumed to reach the three titration endpoints: V 1 2.113mL, V 2 3.121mL, V 3 5.323mL;

[0132] The concentrations of free acid, silicon, and aluminum were calculated using the following formula:

[0133]

[0134] The fluorine content is calculated according to the charge conservation principle, and the formula is C F =C 游离氢 +4C 硅 +3C Al -C Cl -, calculate the fluorine content.

[0135] (3) The calculated contents of free acid, Si, Al and F in the waste acid were 5.282 mol / L, 0.63 mol / L, 1.376 mol / L and 8.778 mol / L, respectively.

[0136] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for analyzing and detecting multiple components in waste liquid or recovered liquid of mixed acid, characterized in that: Prepare the waste acid residue or recovered acid of the mixed acid, and the detection method includes determining the content of hydrofluoric acid, hydrochloric acid, silicon and aluminum therein, and the steps are as follows: (1) Determination of Cl in waste acid residue or recovered acid - Content; (2) Determine the content of free acid, silicon and aluminum in the waste acid residue or recovered acid, the method comprising: S1, prepare potassium hydrogen phthalate standard solution and sodium hydroxide solution of a certain concentration; S2, using potassium hydrogen phthalate standard solution to calibrate the sodium hydroxide solution and calculate the accurate concentration of the sodium hydroxide solution; S3, taking a certain volume of waste acid residue or recovered acid, titrating with a NaOH solution of known concentration until three titration endpoints appear, and recording the volumes of NaOH V1, V2 and V3 consumed to reach the three titration endpoints; S4, respectively calculating the contents of free acid, silicon and aluminum in the waste acid residue or the recovered acid; The formula for calculating the free acid content is C 游离酸 V 废酸残液或回收酸 =C NaOH V1, that is The formula for calculating the silicon content in the waste acid residue or recovered acid is 4C Si V 废酸残液或回收酸 =(V2-V1)C NaOH ,Right now The formula for calculating the aluminum content in the waste acid residue or recovered acid is 4C Al V 废酸残液或回收酸 =(V3-V2)C NaOH ,Right now (3) Calculate the fluorine content according to the charge conservation principle, the formula is C F =C 游离酸 +4C 硅 +3C Al -C Cl- .

2. The analysis and detection method according to claim 1, characterized in that: In step (1), Cl in the waste acid residue or recovered acid is determined - Methods of assay include: S1, prepare NaCl standard solution and AgNO3 solution of a certain concentration; S2, use NaCl standard solution to calibrate AgNO3 solution and calculate the accurate concentration of silver nitrate solution; S3, adding a certain amount of waste acid residue or recovered acid to deionized water and titrating with a AgNO3 solution of known concentration; S4, calculate the Cl in the waste acid residue or recovered acid -1 concentration.

3. The analysis and detection method according to claim 2, characterized in that: In S2, the calculation formula for the concentration of AgNO3 solution is: Among them, V 终点 is the volume of AgNO3 solution consumed at the titration endpoint.

4. The analysis and detection method according to claim 2, characterized in that: In S4, calculate Cl -1 The concentration formula is Right now 5. The analysis and detection method according to any one of claims 1 to 4, characterized in that: In step (2), in S2, the formula for calculating the concentration of the sodium hydroxide solution is C NaOH V NaOH =C 邻苯二甲酸氢钾 V 邻苯二甲酸氢钾 ,Right now 6. Application of the method for analyzing and detecting multiple components in the waste liquid or recovered liquid of the mixed acid according to any one of claims 1 to 5 in the detection of acid liquid components for purification of negative electrode materials for lithium ion batteries.

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