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CN-121978193-A - Method for detecting content of magnetic substance in lithium carbonate

CN121978193ACN 121978193 ACN121978193 ACN 121978193ACN-121978193-A

Abstract

The invention provides a method for detecting the content of magnetic substances in lithium carbonate, which comprises the following steps of S1, collecting and preprocessing a sample; S2, carrying out accurate weighing and constant volume of a sample; S3, carrying out gradient magnetic field magnetic separation enrichment; the method comprises the steps of S4, S5, S6, S7, S8, S9, S10, S11, S7, S9, S10, S11, S7, S, S. The method creatively solves the problems in the prior art by combining the organic combination of gradient magnetic field separation and enrichment, ultrasonic auxiliary purification, ICP-MS accurate detection and multivariate statistical error correction aiming at the core pain point of the existing magnetic substance detection technology in lithium carbonate.

Inventors

  • MENG JIA
  • LIN DONGZI
  • YE ZHIQIANG

Assignees

  • 山西东拓新能源科技有限公司

Dates

Publication Date
20260505
Application Date
20260209

Claims (10)

  1. 1. A method for detecting the content of magnetic substances in lithium carbonate, which is characterized by comprising the following steps: S1, sample collection and pretreatment are carried out; s2, carrying out accurate weighing and constant volume of a sample; S3, carrying out gradient magnetic field magnetic separation enrichment; S4, carrying out ultrasonic auxiliary washing and purification of the enrichment liquid; S5, performing precipitation dissolution and volume fixing of the magnetic substance; s6, performing ICP-MS instrument calibration and parameter optimization; S7, performing detection mother liquor measurement and multivariate statistical error correction; s8, performing blank experiment correction; S9, performing parallel experiment verification; S10, calculating and judging results; and S11, performing method verification and archiving.
  2. 2. The method for detecting the content of magnetic substances in lithium carbonate according to claim 1, wherein the step S1 specifically comprises: The method comprises the steps of collecting lithium carbonate samples, removing physical impurities in the samples through pretreatment, avoiding interference to subsequent magnetic separation and detection links, guaranteeing uniformity of the samples, laying a foundation for subsequent accurate weighing and detection, adopting a sterile sampler, collecting the samples at the upper, middle and lower three parts of a lithium carbonate finished product bin respectively, collecting 3 parts of each part, wherein each part is not less than 50g, avoiding direct contact of the sampler and metal equipment in the sampling process, preventing external magnetic impurities from being introduced, merging the collected 9 parts of samples, placing the samples in a clean agate mortar, adopting a manual grinding mode, controlling grinding force to be 50-80N in the grinding process, grinding time to be 15-20 minutes until the samples completely pass through a 200-mesh nylon sieve, placing the sieved samples in a vacuum drying box, setting drying temperature to be 105+/-2 ℃, vacuum degree to be 0.08-0.10MPa, drying time to be 2 hours, removing water and free water in the samples, avoiding influence on the subsequent magnetic separation efficiency and the detection result due to the water, taking out of the samples, accurately drying, taking out the samples to be cooled to be about room temperature, cooling the samples to be about 10g, cooling the samples in a moisture bag, and carrying out a cooling method for about 30 minutes, and sealing, and obtaining samples after cooling, and obtaining the samples after cooling, and carrying out a sample for a test.
  3. 3. The method for detecting the content of the magnetic substance in the lithium carbonate according to claim 2, wherein the step S2 specifically includes: Accurately weighing a sample to be detected, dissolving the sample into a specific solvent to prepare uniform sample mother solution, providing a quantitative sample system for subsequent magnetic separation and enrichment, and ensuring the repeatability and comparability of detection results, wherein the operation method comprises the following steps: taking out the sample to be tested pretreated in the step S1, adopting an electronic ten-thousandth balance with the precision of 0.0001g, weighing after being qualified by metering and calibration, preheating the balance for 30 minutes before weighing, calibrating the balance zero point, avoiding the environmental temperature, controlling the temperature to be 25+/-2 ℃ and the humidity to be 50+/-5%RH, influence on the weighing precision of the balance; the mass of the clean 50mL volumetric flask is firstly weighed by adopting differential subtraction and is recorded as m 0 , then taking a proper amount of sample by an agate medicine spoon, putting the sample into a volumetric flask, weighing the total mass of the volumetric flask and the sample again, recording as m 1 , controlling the mass of the sample to be m=m 1 - m 0 , controlling the weighing mass of the sample to be 2.0000+/-0.0002 g, weighing 3 parts in parallel, and ensuring that the weighing error is less than or equal to 0.01%; slowly adding 20mL of hydrochloric acid solution with the concentration of 1+1 into a volumetric flask with a weighed sample, and mixing and preparing the solution by using high-grade pure hydrochloric acid and ultrapure water according to the volume ratio of 1:1, wherein the resistivity of the ultrapure water is more than or equal to 18.2M omega cm, the interference of impurities in water is avoided, and the volumetric flask is gently shaken while being added, so that the sample is fully dissolved, and incomplete dissolution of the sample caused by overhigh local concentration is avoided; after the sample is completely dissolved, the sample is dissolved, observing that the volumetric flask has no white sediment and turbidity, flushing the inner wall of the volumetric flask with ultrapure water for 3-4 times, allowing the flushing liquid to flow into the volumetric flask completely, then, ultrapure water is used for fixing the volume to the scale mark, shaking is carried out, standing is carried out for 10 minutes, a sample mother solution is obtained, the sample mother solution is marked as mother solution A, 3 parts of mother solution A are prepared in parallel, and the serial numbers of the mother solution A are A 1 、A 2 、A 3 respectively for standby.
  4. 4. The method for detecting the content of magnetic substances in lithium carbonate according to claim 3, wherein the step S3 specifically comprises: The magnetic substances in the sample mother liquor are thoroughly separated and enriched by utilizing the magnetic intensity difference of different magnetic substances and adopting a gradient magnetic field, so that the problem that different magnetic impurities cannot be completely separated by the existing single magnetic field intensity is solved, the enrichment efficiency and the separation purity of the magnetic substances are improved, and a foundation is laid for reducing the detection lower limit and improving the detection precision in the subsequent detection links; the operation method comprises selecting an autonomously designed gradient magnetic field separation device, wherein the device comprises a magnetic field generator, a separation column, a collecting tank and a temperature control system, the magnetic field intensity can be continuously adjusted within the adjustment range of 0.1-1.5T, firstly cleaning and calibrating the separation device, flushing the inner wall of the separation column with ultrapure water for 3-4 times to remove residual impurities, and then calibrating the magnetic field intensity to ensure that the error of the magnetic field intensity is less than or equal to +/-0.01T; pouring mother liquor A 1 、A 2 、A 3 prepared in the step S2 into 3 clean separation columns respectively, pouring 20mL of mother liquor into each separation column, controlling the flow rate of the separation column to be 1.0-1.5mL/min, regulating the flow rate by a peristaltic pump, controlling the rotation speed of the peristaltic pump to be 50-80r/min, starting a magnetic field generator, setting gradient magnetic field parameters, namely, the initial magnetic field strength to be 0.1T, then uniformly raising the initial magnetic field strength to be 1.5T at the speed of 0.05T/min, maintaining the magnetic field strength for 5min, then lowering the initial magnetic field strength to be 0.1T at the speed of 0.1T/min, completing one gradient magnetic field cycle for 3 times, ensuring that impurities with different magnetic strengths, strong magnetic iron simple substances, cobalt simple substances, weak magnetic Fe 2 O 3 and NiO can be adsorbed by magnetic fields, controlling the temperature of the separation column to be 25+/-1 ℃ by a temperature control system in the magnetic field cycle process, avoiding the influence of the magnetic field strength and the adsorption effect of magnetic substances after the magnetic separation is completed, closing a magnetic field generator, standing for 5 minutes, allowing the magnetic substance to be adsorbed on the inner wall of the separation column to completely fall off, flowing into a collecting tank to obtain a magnetic substance enrichment liquid, marking the enrichment liquid as enrichment liquid B, obtaining 3 parts of enrichment liquid B 1 、B 2 、B 3 in parallel, collecting the residual mother liquid in the separation column, marking the residual mother liquid as waste liquid, and using the waste liquid for subsequent matrix interference analysis.
  5. 5. The method for detecting the content of magnetic substances in lithium carbonate according to claim 4, wherein the step S4 specifically comprises: Removing lithium carbonate matrix impurities and other non-magnetic impurities in the enrichment liquid B, avoiding matrix interference generated by the impurities on ICP-MS detection in a subsequent detection link, improving the purity of the enrichment liquid, and ensuring the accuracy of detection signals; pouring 3 parts of enrichment liquid B 1 、B 2 、B 3 obtained in the step 3 into 350 mL centrifuge tubes respectively, adding 10mL of ultrapure water into each centrifuge tube, and lightly shaking the centrifuge tube for 1 minute to ensure that the enrichment liquid and the ultrapure water are fully mixed, wherein the resistivity of the ultrapure water is more than or equal to 18.2M omega cm; placing the centrifuge tube into an ultrasonic cleaner, setting ultrasonic power to 200-250W, ultrasonic frequency to 40kHz, ultrasonic time to 15 min, controlling water temperature of the ultrasonic cleaner to 25+ -2 ℃ in ultrasonic process to avoid oxidation of magnetic substances caused by overhigh water temperature and influence on subsequent detection result, placing the centrifuge tube into a high-speed centrifuge after ultrasonic completion, setting centrifugal speed to 8000r/min, centrifuging for 10 min, centrifuging at 25 ℃ to enable magnetic substances to be precipitated at the bottom of the centrifuge tube, dissolving nonmagnetic impurities and substrate impurities into supernatant, slowly sucking supernatant by a pipette after centrifugation to avoid touching bottom sediment, pouring into a waste liquid collecting bottle to keep the magnetic substances at the bottom of the centrifuge tube, adding 10mL of ultrapure water into each centrifuge tube again, repeating the operations of ultrasonic and centrifuging and supernatant sucking until the supernatant is colorless transparent, detecting by an ultraviolet-visible spectrophotometer, enabling absorbance of the supernatant to be less than or equal to 0.001 in a wavelength range of 200-800nm to indicate that the substrate impurities and nonmagnetic impurities are completely removed, marking the bottom of the centrifuge tube as the sediment after washing is completed, keeping the magnetic substances at the bottom of the centrifuge tube, 3 parts of precipitate C 1 、C 2 、C 3 were obtained in parallel for further use.
  6. 6. The method for detecting the content of magnetic substances in lithium carbonate according to claim 5, wherein the step S5 specifically comprises: The high-purity magnetic substance precipitate C is completely dissolved in a specific solvent to prepare uniform detection mother liquor, so that the magnetic substance is converted into an ionic state, the subsequent ICP-MS detection is facilitated, and the stability and accuracy of a detection signal are ensured; the operation method comprises the following steps of respectively adding 5mL of nitric acid solution with the concentration of 5% into a centrifuge tube corresponding to 3 parts of precipitate C 1 、C 2 、C 3 obtained in the step 4, mixing and preparing the solution by using high-grade pure nitric acid and ultrapure water according to the volume ratio of 1:19, wherein the high-grade pure nitric acid can avoid introducing impurities, the low-concentration nitric acid can ensure that magnetic substances are completely dissolved, and meanwhile, the interference of a matrix detected by subsequent ICP-MS (inductively coupled plasma-mass spectrometry) caused by excessive nitric acid is avoided; placing the centrifuge tube into a constant-temperature water bath kettle, setting the water bath temperature to be 60+/-2 ℃, slightly shaking the centrifuge tube once every 5 minutes in the water bath process for 20 minutes, promoting the precipitation dissolution of magnetic substances, observing the precipitation dissolution condition until the precipitation is completely dissolved, ensuring no black or brown precipitation residues, dropwise adding 0.1mL of high-grade pure nitric acid if the precipitation is not completely dissolved until the precipitation is completely dissolved, recording the total addition amount of nitric acid, taking the centrifuge tube out of the constant-temperature water bath kettle after the precipitation is completely dissolved, placing the centrifuge tube into a ventilation cabinet for cooling to room temperature for about 20 minutes, avoiding the volatilization of the solution caused by the excessive temperature and affecting the concentration accuracy, slowly transferring the cooled solution into a 25mL measuring flask, flushing the inner wall of the centrifuge tube with ultrapure water for 3-4 times, completely flowing into the measuring flask, ensuring no residue of the magnetic substances, fixing the volume of the solution in the measuring flask to a scale mark by the ultrapure water, shaking and standing for 5 minutes to obtain a magnetic substance detection mother solution D, marking as a detection mother solution D 1 、D 2 、D 3 for standby, and simultaneously preparing a blank solution, namely taking a 25mL volumetric flask, adding 5mL nitric acid solution with the same concentration, and using ultrapure water to fix the volume to a scale mark, wherein the mark is blank solution D 0 for subsequent blank correction.
  7. 7. The method for detecting the content of magnetic substances in lithium carbonate according to claim 6, wherein the step S6 specifically comprises: The ICP-MS instrument is calibrated and parameters are optimized, so that the instrument is in an optimal working state, the sensitivity and accuracy of detection are improved, and the systematic error caused by the instrument is reduced; the operation method comprises the following steps of selecting an inductively coupled plasma mass spectrometer, preheating the instrument for 60 minutes after starting up the instrument before detection, and starting argon in the preheating process, wherein the argon flow is controlled to be 15L/min, so that no air residue exists in an internal pipeline of the instrument; after preheating, performing instrument calibration, adopting an external standard method to calibrate, preparing a series of standard solutions with concentration gradients, namely respectively and accurately sucking standard stock solutions of iron, cobalt and nickel, wherein the concentration is 1000 mug/mL, the standard solutions are preferably pure, diluting the standard stock solutions with 5% nitric acid solution to prepare standard series solutions with the concentration of 0.1ppb, 1ppb, 10ppb, 50ppb and 100ppb, setting 3 parallel samples for each concentration gradient, simultaneously preparing blank standard solutions, sequentially introducing the standard series solutions and the blank standard solutions into an ICP-MS instrument, measuring according to set parameters, recording the signal intensity corresponding to each concentration standard solution, drawing a standard working curve with the standard solution concentration as an abscissa and the signal intensity as an ordinate, calculating the correlation coefficient R2 of the standard working curve, wherein the R2 is more than or equal to 0.9999, and the standard series solutions are required to be prepared again until the requirements are met, after the standard curve calibration is completed, carrying out parameter optimization on the optimized standard curve, wherein the optimized parameters comprise radio frequency power, atomization, auxiliary air flow, sampling depth, integration time and the like, the optimized range of each parameter and the optimized value are as follows that the optimized radio frequency power is the optimized range to be W1200, the optimized value is W1350, the optimal value is the optimal signal weak strength, the weak signal strength is caused, the method comprises the steps of enabling matrix interference to be enhanced due to over-high power, enabling an optimal range of atomization air flow to be 0.8-1.2L/min, enabling an optimal value to be 1.0L/min, enabling atomization air flow to be incomplete due to over-low atomization air flow, enabling signal intensity to be unstable, enabling sample dilution to be achieved due to over-high flow, enabling sensitivity to be reduced, enabling auxiliary air flow to be 0.2-0.5L/min, enabling auxiliary air flow to be 0.3L/min, enabling auxiliary air to stabilize plasma, enabling flow to be improper, enabling the plasma to be extinguished, enabling a sampling depth to be 8-12mm, enabling the optimal value to be 10mm, enabling sampling depth to affect signal intensity and interference level, enabling interference to be increased due to over-deep or too shallow, enabling integration time to be 0.1-0.5s, enabling signal fluctuation to be large due to over-short integration time to be too short, enabling detection efficiency to be reduced due to over-long integration time, enabling signal intensity of standard series solutions to be measured again after parameter optimization is completed, enabling stability of a standard series solutions to be verified, enabling relative standard deviation to be required to be 2%, enabling RSD to be optimized to be needed, enabling parameters to be re-optimized to be needed, enabling parameters to be set to be needed to be reserved after calibration and parameter optimization are completed.
  8. 8. The method for detecting the content of the magnetic substance in the lithium carbonate according to claim 7, wherein the step S7 specifically includes: the method comprises the steps of sequentially introducing 3 parts of detection mother liquor D 1 、D 2 、D 3 and blank solution D 0 prepared in the step S5 into the ICP-MS instrument according to instrument parameters optimized in the step S6 for measurement, measuring each sample in parallel for 3 times, recording the measured signal intensity each time to obtain signal intensity average value of detection mother liquor D 1 、D 2 、D 3 , recording the signal intensity average value as S 1 、S 2 、S 3 and blank solution D 0 , recording the signal intensity average value as S 0 , converting the signal intensity average value S 1 、S 2 、S 3 、S 0 into corresponding concentration values according to a standard working curve drawn in the step S6, obtaining the preliminary detection concentration of the detection mother liquor, recording the concentration values of the C 1 、C 2 、C 3 and the blank solution as C 0 , calculating the preliminary detection concentration as C i = k×S i +b (i= 1,2,3,0), wherein k is the slope of a working curve, b is the standard deviation regression curve, and establishing a linear error correction model in the standard error correction error elimination process by adopting a multivariate statistical combination model, and establishing a multivariate error correction model: ; Wherein the meanings of each symbol are as follows: the final detection concentration of the magnetic substance after error correction is the core output value of the step; the regression constant term represents basic deviation in the detection process, and is obtained by combining partial least squares regression with Bayesian regularization fitting, and regularization parameters are introduced in the fitting process For avoiding model overfitting; for the detection concentration regression coefficient, the influence weight of the preliminary detection concentration on the final detection concentration is represented, The method shows that the primary detection concentration and the final detection concentration are positively correlated, the larger the weight is, the more obvious the influence of the primary detection concentration is, and the solution formula is that , The average value of the preliminary detection concentration; In order to weigh the error regression coefficient, represent the influence weight of the weighing error of the sample in the step S2 on the final detection concentration, The positive and negative of (a) are determined by the direction of the weighing error, when the weighing value is larger, When the weighing value is smaller, the weight of the material is smaller, Solving a normal distribution probability density function which needs to combine weighing errors, and introducing a correction factor ; The regression coefficient of the magnetic separation recovery rate is used for representing the influence weight of the magnetic separation recovery rate in the step S3 on the final detection concentration, The higher the recovery rate of magnetic separation, the closer the final detection concentration is to the true value, and the Avgalileo constant is introduced during solving As a trace species metering correction term; The matrix interference regression coefficient represents the influence weight of residual matrix impurities after washing in the step S4 on the final detection concentration, The positive and negative of (a) are determined by the type of matrix interference, and during ion enhancement, In the case of ion inhibition effect, the ion inhibition effect, The Planck constant is introduced during solving As a microscopic particle disturbance correction term; Preliminary detection concentration for detecting mother liquor; For the sample weighing error, the calculation formula is M is the actual weighing mass, m 0 is the standard weighing mass 2.0000g, Fitting the superposition characteristics of the precisely weighed normal distribution and the log normal distribution for weighing the error composite correction coefficient; for the recovery rate of magnetic separation, the calculation formula is , For the mass of the magnetic substance enriched in step S3, For the true mass of the magnetic material in the sample, e is a natural constant, about 2.71828, Compensating the influence of temperature fluctuation in the magnetic separation process for a recovery rate temperature correction term; The residual impurity amount of the substrate is obtained by measuring the concentration of Li + in the supernatant liquid after washing in the step S4 by an ultraviolet-visible spectrophotometer, and the correction formula is as follows , For the actual measurement, γ is Euler-Ma Xieluo Ni constant, about 0.5772, As the standard deviation of the detection of the matrix impurities, Randomly correcting the term for matrix interference; to measure the standard deviation of the error, the error is obtained by combining parallel weighing experiments with Bayesian estimation fitting and obeys normal distribution As the mean value of the standard deviation, Is the standard deviation variance; to improve the normal distribution cumulative distribution function, a logarithmic correction term is introduced Quantifying the nonlinear cumulative effect of weighing errors, embodying the expertise of higher order statistical error correction, the integration can be solved numerically by a Gaussian-Legendre integration formula: , For the legendre polynomial root, Is a weight coefficient; The method is a high-order Gaussian correction term, and is combined with pi, e and gamma constants to inhibit interference of abnormal weighing errors on a final result and compensate system deviation caused by environmental humidity; Fitting a nonlinear influence rule of magnetic separation recovery rate for a logarithmic-constant composite correction term, wherein the Avgalileo constant correction term is used for compensating the counting deviation of micro magnetic substance particles; For a high-order correction term of matrix interference, the influence weight of the matrix interference is adjusted through an Euler-Ma Xieluo Niconstant, a Planck constant and a quadratic root, and detection deviation caused by microscopic ion collision is compensated; is random error term and obeys normal distribution , Is the variance of random error, represents unexpected accidental error in the detection process and meets the requirement N is the number of parallel measurements, As an average value of the random error, Is a variance correction factor; For the deviation weight factor of the ith parallel measurement, the calculation formula is as follows For adjusting the impact weight of the random error, The random error weighting term is used for further improving the accuracy of error correction; The error correction model is established and solved by preparing 15 groups of labeled samples with different concentrations through a labeled recovery experiment, wherein the labeled concentration is 0.1-100ppb, three concentration intervals of low, medium and high are covered, 5 groups of each interval are detected according to steps S1 to S7 of the method, and the primary detection concentration of each group of labeled samples is obtained Error in weighing Recovery rate of magnetic separation Residual amount of matrix impurities And the true concentration of the labeled sample, noted as The true concentration is determined by isotope dilution mass spectrometry to ensure the accuracy of the true value As a dependent variable, to 、 、 、 Fitting a multiple linear regression equation by combining partial least squares regression with Bayes regularization as an independent variable, and introducing regularization parameters Weight coefficient , For the detection standard deviation of the i-th set of labeled samples, Reducing the influence of abnormal values on fitting results for weight attenuation factors, and solving to obtain regression constant terms And regression coefficient 、 、 、 The fitting process satisfies Regularization term For avoiding overfitting of the model, improving generalization capability of the model, and calculating the decision coefficient of the model Adjusting the determination coefficient Root mean square error and mean absolute error, wherein , K is the number of independent variables, k=4), Introducing pi, e and gamma constants for precision correction, Requirements are that 、 In addition, the significance of the model is verified through F test, and the calculation formula of F statistic is that Requiring F to be more than or equal to 10000, and obviously, ensuring that the model has statistical significance with the significance level alpha=0.01, and measuring the step S7 、 、 、 Substituting the magnetic substance into an error correction model, and calculating to obtain the final detection concentration of the magnetic substance after error correction 、 、 Corresponding to 3 parts of detection mother liquor D 1 、D 2 、D 3 respectively, calculating the average value of 3 parts of final detection concentration, and recording as And relative standard deviation, wherein Introducing gamma, pi and e to correct small deviation, compensating the systematic deviation of parallel measurement, E, gamma and pi are introduced to optimize deviation quantization precision, the statistical requirement of precise detection is met, RSD is required to be less than or equal to 1.5%, if RSD is more than 1.5%, the detection mother solution is required to be re-measured, and error correction model parameters are checked until the requirement is met.
  9. 9. The method for detecting the content of magnetic substances in lithium carbonate according to claim 1, wherein the step S8 specifically comprises: the method comprises the steps of further correcting detection results through a blank experiment, eliminating micro magnetic impurity interference existing in reagent, ultrapure water and instrument pipeline links, guaranteeing the authenticity and accuracy of the detection results, providing a basis for parallel experiment verification in the step S9, preparing 5 parts of blank solutions in parallel according to the preparation method in the step S5, marking as D 01 、D 02 、D 03 、D 04 、D 05 , completely consistent with the detection mother liquor in the preparation process of the blank solutions, adding no magnetic substance precipitate C, adding 5ml of 5% nitric acid solution and ultrapure water, guaranteeing that the preparation environment, reagent, instrument and detection mother liquor of the blank solutions are completely identical, introducing 5 parts of blank solutions into an ICP-MS instrument according to instrument parameters optimized in the step S6, measuring, parallelly measuring each blank solution for 3 times, recording the signal intensity measured each time, calculating the signal intensity average value of each blank solution, marking as S 01 、S 02 、S 03 、S 04 、S 05 , converting the signal intensity average value of the blank solutions into corresponding concentration values according to a standard working curve drawn in the step S6, marking as C 01 、C 02 、C 03 、C 04 、C 05 , obtaining 5 parts of blank solutions, removing abnormal concentration values in the standard values, calculating the concentration values of the rest blank solutions according to the standard, wherein the significance level = 0.05, marking the concentration values of the rest blank solutions as average values are calculated by adopting the Graves criterion And standard deviation, noted as Requirements are that Less than or equal to 0.05ppb, if Preparing a blank solution again with 0.05ppb reagent and ultrapure water, and measuring until the blank solution meets the requirement, and averaging the detected concentration obtained in the step S7 Subtracting the mean value of blank solution concentration Obtaining the concentration of the magnetic substance after blank correction, which is recorded as The correction formula is: If (1) <0, Indicating that the blank solution concentration is higher than the detection mother solution concentration, and re-checking the detection process, and re-determining after eliminating interference; The step S9 specifically includes: The repeatability and stability of the detection method are verified through parallel experiments, the accurate and reliable detection results of the method can be obtained in different operation batches and different samples, the operation method comprises the following steps of collecting 3 batches of lithium carbonate samples again according to the complete flow of steps S1 to S8, preparing 3 parts of detection mother liquor in parallel with the samples collected in the step S1 to prepare 9 parts of detection mother liquor in total according to the same batch, respectively performing ICP-MS (inductively coupled plasma-mass spectrometry), multivariate statistics error correction and blank experiment correction on the 9 parts of detection mother liquor to obtain 9 parts of blank corrected magnetic substance concentration, and recording as 、 、...、 Calculate the average value of the concentration value of 9 parts, record as The method comprises the steps of adding standard solutions of iron, cobalt and nickel with known concentrations into a sample weighed in the step S2, detecting the sample according to the flow of the steps S3 to S8, calculating the standard adding recovery rate, wherein the formula is that the standard adding recovery rate (%) = (detected concentration after standard adding-non-standard adding detection concentration)/standard adding concentration multiplied by 100%, each standard adding concentration is parallelly measured for 3 times, calculating the average value of the standard adding recovery rate, verifying that the RSD of a parallel experiment is less than or equal to 2.5%, the standard adding recovery rate is between 95 and 105%, if the standard does not meet the verification standard, searching for reasons, and carrying out the parallel experiment again until all data of the parallel experiment are met, including detected concentration, error correction value, blank correction value, RSD, standard adding recovery rate and the like, and forming a parallel experiment report.
  10. 10. The method for detecting the content of magnetic substances in lithium carbonate according to claim 9, wherein the step S10 specifically comprises: According to the sample weighing mass of the step S2, m=2.0000 g, the constant volume of the detection mother liquor of the step S5, V 1 =25 mL, the constant volume of the sample mother liquor of the step S2, V 2 =50 mL, the magnetic separation enrichment liquid of the step S3 and V 3 =20 mL, the actual content of the magnetic substance in the lithium carbonate sample is calculated, expressed in terms of mass fraction omega, in ppb, and the calculation formula is as follows: ; Wherein the meanings of each symbol are as follows: The actual mass fraction of the magnetic substance in the lithium carbonate sample; The method comprises the steps of obtaining a total concentration average value after blank correction of a parallel experiment in the step S9, wherein V 1 is the constant volume of a mother solution detected in the step S5, V 2 is the constant volume of a mother solution sample in the step S2, m is the sample weighing mass in the step S2, V 3 is the volume of a magnetic separation enrichment solution in the step 3, 10 - is a unit conversion coefficient, and μg/g is converted into ppb, wherein 1 ppb=1 μg/kg=10 - μg/g; The circumference ratio is used as a precise correction coefficient for volume and mass conversion, and is used for compensating tiny volume deviation in the process of constant volume and enrichment, so that the calculation accuracy is improved; Is Euler-Ma Xieluo Ni constant for correcting systematic deviation in the process of weighing and constant volume, and simultaneously regulating weight of each correction term, e is natural constant for compensating concentration deviation caused by solution volatilization and adsorption, The calculation accuracy is further improved for the constant composite correction factor; For the avogalileo constant, A correction term for measuring trace substances is used for compensating the tiny deviation in the counting process of the magnetic substance particles; is a constant of planck, which is set to be the planck's constant, The method is a microcosmic interference correction term and is used for compensating tiny detection deviation caused by ion collision and excited state particle transition in the ICP-MS detection process; for the volume temperature correction coefficient, the calculation formula is , The solution volume expansion coefficient is about 2.1 multiplied by 10 -4 /°c, T is the experimental environment temperature, and is used for compensating the influence of experimental temperature fluctuation on the solution volume and ensuring the accuracy of volume parameters; For the higher-order calculus correction term, the integral variable V is the volume of the solution, and a logarithmic correction term is introduced Quantifying the nonlinear change of the concentration of the magnetic substance in the process of the sample mother solution from the enrichment volume to the constant volume, wherein the integration is solved by combining a fractional integration method with Gaussian-Legend numerical integration, and the specific solving process is as follows , Then , According to the fractional integral formula Can be obtained The second integral is solved by a Gauss-Legendre numerical integral formula, n=5 nodes are taken, the integral accuracy is ensured to be less than or equal to 10 -8 ppb, and the actual contents of three magnetic substances of iron, cobalt and nickel are calculated respectively 、 、 The calculation of each substance introduces a proprietary high order correction factor and constant combination: introducing correction terms during computation The calculation formula is ; Introducing correction terms during computation The calculation formula is ; Introducing correction terms during computation The calculation formula is The total content calculation formula of the three magnetic substances is as follows: , for the comprehensive correction coefficient of the total content, the detection deviation of three substances is balanced, Compensating mutual interference among three magnetic substances for the microscopic correction term of the total content, judging the quality of a sample, namely, the requirement of battery-level lithium carbonate ≤ 10ppb、 ≤ 5ppb、 ≤ 5ppb、 Less than or equal to 20ppb, industrial grade lithium carbonate requirement ≤ 50ppb、 ≤ 20ppb、 ≤ 20ppb、 Judging whether the sample is qualified or not if the sample detection result meets the standard requirement of the corresponding level, otherwise judging that the sample is unqualified, providing a correction proposal for unqualified samples, recording the result calculation process and the judgment result to form a detection report, wherein the detection report comprises sample information, detection steps, detection data, error correction data, parallel experiment data, result calculation, judgment conclusion and correction proposal content, and ensuring the integrity and traceability of the detection report; the step S11 specifically includes: The scientificity, the accuracy, the stability and the applicability of the whole detection method are comprehensively verified, all data and reports in the detection process are filed in a standardized way, and support is provided for popularization and application of the method and follow-up rechecking; the method comprises the following steps of performing indoor verification and outdoor verification, wherein the indoor verification is completed by laboratory professional detection personnel, detecting 3 standard samples with different concentrations, namely 0.5ppb for low concentration, 10ppb for medium concentration and 50ppb for high concentration, measuring each concentration in parallel for 6 times, calculating the relative standard deviation, the standard adding recovery rate and the detection lower limit of a detection result, and performing verification on the detection standard, namely that the RSD is less than or equal to 2.5%, the standard adding recovery rate is 95% -105% and the detection lower limit is less than or equal to 0.1ppb, and re-optimizing the method parameters until the requirements are met if the detection standard is not met; the method comprises the steps of providing the same lithium carbonate sample and a method operation manual by 3 third party detection mechanisms, independently detecting by the third party mechanisms according to the method, comparing the detection result of the third party mechanisms with the detection result of the laboratory, calculating the relative deviation, requiring the relative deviation to be less than or equal to 3%, ensuring the applicability and universality of the method, avoiding that the method can only be realized in a single laboratory and cannot be popularized and applied, finishing all verification data after the method is verified, forming a detection method verification report, wherein the report comprises the contents of verification purposes, verification schemes, verification data, verification conclusions, optimization suggestions and the like, ensuring the traceability of the verification process, and simultaneously, collecting and recording samples, preprocessing records, weighing records, magnetic separation records, ultrasonic washing records, ICP-MS (inductively coupled plasma-Mass Spectrometry) measurement records, error correction data, blank experiment data, parallel experiment data, and finally, summarizing the detection method, carding method operation key points and notes to form a method operation manual, providing guidance for industrialized batch detection, laboratory daily detection and personnel training, and ensuring that different operators can obtain accurate and stable detection results according to manual operation.

Description

Method for detecting content of magnetic substance in lithium carbonate Technical Field The invention particularly relates to a method for detecting the content of magnetic substances in lithium carbonate. Background Lithium carbonate is used as a key strategic resource and is widely applied to the fields of lithium ion batteries, medicines, ceramics, glass and the like, wherein the lithium ion battery industry is the most main consumption scene, and the proportion of the lithium ion battery is more than 70%. With the rapid development of industries such as new energy automobiles, energy storage equipment and the like, the purity requirement of the market on lithium carbonate is increasingly severe, especially the purity of battery grade lithium carbonate is more than 99.9%, and the impurity content is extremely controlled. The magnetic substances are typical harmful impurities in lithium carbonate and mainly originate from metal simple substances and oxides such as iron, cobalt, nickel and the like introduced in the processes of mining, crushing and floatation of raw material lithium ores (such as spodumene, lepidolite), and metal scraps generated by abrasion of production equipment (such as crushers, grinders and pipelines). The existence of the magnetic substances can seriously influence the quality of products, namely, in a lithium ion battery, magnetic impurities can cause internal short circuit, short cycle life, reduced rate capability and even potential safety hazard of the battery, in the field of medicine, the magnetic impurities can cause adverse reactions such as human organ stimulation and inflammation, and in the production of high-end ceramics and glass, the magnetic impurities can cause uneven color and luster and reduced transparency of the products, and the added value of the products is reduced. At present, the detection requirement on the content of magnetic substances in lithium carbonate in industry is increasingly urgent, and relevant standards are formulated in various countries, for example, the content of iron in battery-grade lithium carbonate is less than or equal to 0.001% and the content of cobalt and nickel is less than or equal to 0.0005% as clearly specified in GB/T11075-2023 lithium carbonate in China. However, the existing detection method still has a plurality of limitations, and is difficult to meet the actual requirements of high-precision, high-sensitivity and rapid detection, especially for detecting trace (ppb level) magnetic substances, and the accuracy and repeatability of the prior art are required to be improved. Before the method is proposed, a weight method, a magnetic separation-atomic absorption spectrometry method, an inductively coupled plasma mass spectrometry (ICP-MS) direct detection method and the like are mainly used for detecting the content of magnetic substances in lithium carbonate, and the method has the core dilemma that firstly, the lower detection limit is higher, the lower detection limit of the existing method is more than 10-50ppb, the detection requirement of battery-level lithium carbonate on magnetic substances below ppb level cannot be met, potential risks caused by the fact that trace impurities cannot be accurately identified are difficult to be met, secondly, interference factors are more, a lithium carbonate matrix has certain ion interference, in the detection process, the influence of factors such as environment, reagents and equipment is easily caused, the detection error is larger, repeatability is poor, the Relative Standard Deviation (RSD) is more than 5%, the operation is complex and time consuming, for example, the weight method needs to be subjected to multiple complicated steps such as magnetic separation, filtration, drying and weighing, the single detection time consuming more than 8 hours cannot be met, the existing magnetic separation and enrichment method cannot be realized, the existing magnetic separation method is more difficult to accurately separate and accurately identify magnetic substances, the magnetic impurities (such as iron oxide impurities with different strong magnetic intensities) cannot be accurately detected by the existing magnetic separation method, the magnetic separation error is difficult to be accurately corrected, the error is not completely caused by the existing magnetic separation system, and the magnetic error is not completely corrected, and the magnetic error is not completely caused by the magnetic error is not easy to be easily detected, and the magnetic error is not easy to be corrected. In addition, the detection method disclosed in the prior art does not organically combine the magnetic separation enrichment, matrix interference elimination and statistical error correction, either focuses on the separation and neglect the detection precision or focuses on the thoroughness of neglect of impurity separation in detection, so that the core pain points of inaccurate detection, low detectio