Accurate determination method for lead content in lead concentrate

Abstract

The invention provides a method for accurately measuring the content of lead in lead concentrate, and belongs to the field of analysis of the content of lead in lead concentrate.The method comprises the steps that firstly, a sample is decomposed, dilute sulphuric acid and hydrobromic acid are added to eliminate interference of arsenic, antimony, tin and other elements, lead is precipitated in the form of lead sulfate, and an acetic acid-ammonium acetate buffer solution is used for dissolving the lead sulfate precipitate; then adding a potassium dichromate solution to enable lead to generate a lead chromate precipitate, and titrating and measuring the content of lead in the precipitate by an oxidation-reduction titration method; and measuring the lead content of the filtrate and the filter residue by using an atomic absorption spectrometer. The invention provides a novel method for measuring the lead content in the lead concentrate, the titration end point is clearer, and accurate judgment of detection personnel is facilitated; the method can be cooperated with the existing complexometric titration method to be applied to the determination of the lead content in the lead concentrate component analysis standard substance, and meets the requirements of standard substance valuing technical specifications; and the lead content in the precipitate, the filtrate and the filter residue is measured at the same time, the lead which is easy to lose during the existing lead content measurement is corrected, and the measurement result is more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of lead content analysis in lead concentrate, and in particular to a method for accurately determining the lead content in the lead concentrate. Background Art

[0002] Lead concentrate is an ore with a high lead content. After refining, beneficiation and other processes, pure lead metal can be extracted. Lead is an important non-ferrous metal, commonly used in the manufacture of batteries, printing, chemicals, building materials and nuclear industries. The main raw material for refining lead is lead concentrate, which plays an important role in industry. Therefore, in the smelting and trading process of lead concentrate, an accurate lead concentrate detection method is needed to provide a quantitative basis for metal balance, trade pricing, process index control, method demonstration, mineral evaluation and instrument calibration.

[0003] The existing lead concentrate detection method is mainly based on the principle of complexometric titration. For example, a certain invention patent discloses a method for determining the lead content in gold concentrate and lead concentrate, using nitric acid, bromine water and sulfuric acid to digest the sample, and using hydrobromic acid and dilute sulfuric acid to remove the interference of arsenic, antimony, selenium and tin in the sample on the lead determination, and then using sulfuric acid to form lead sulfate precipitation with lead, filtering and separating other interfering elements, and transferring the precipitation together with filter paper to acetic acid-sodium acetate buffer solution to generate lead acetate and dissolve it in the buffer solution, using xylenol orange as an indicator, and titrating with Na2EDTA standard titration solution; this method only measures the content of lead acetate dissolved in the buffer solution, so that the lead in the filtrate or filter residue is lost, and the use of Na2EDTA titration makes the titration end point unclear, which ultimately leads to inaccurate lead determination results.

[0004] A certain invention patent discloses a simple and efficient method for determining the lead content in gold concentrate. The sample is dissolved in a nitric acid-potassium chlorate solution, and the lead forms a lead sulfate precipitate in a sulfuric acid medium. After filtering, the precipitate, i.e., the lead sulfate on the filter paper, is dissolved in an acetic acid-sodium acetate buffer solution. Under the condition of a pH value of 5.0-6.0, a xylenol orange solution is used as an indicator, and the EDTA standard titration solution is used for titration. The lead content in the precipitate is calculated according to the volume of the consumed EDTA standard solution. At the same time, the filtrate is collected, and the lead content in the filtrate is determined by atomic absorption. Finally, the lead content in the ore is equal to the sum of the lead content in the filtrate and the precipitate. Although this method detects the lead in the precipitate and the filtrate at the same time, reducing the loss of lead in the filtrate, it also uses the EDTA standard titration solution titration method, and the solution turns bright yellow as the titration end point. However, each tester's judgment standard for bright yellow is relatively subjective and there is no unified standard, which may cause the titration result to be too low or too high.

[0005] In addition, the technical specification for the valuation of reference materials proposes to use two or more accurate methods based on different principles to determine their values ​​in order to improve the reliability of the assignment. However, in the prior art, the popular detection methods for determining the lead content in reference materials for lead concentrate composition analysis mostly use methods based on the principle of complexometric titration. The methods have a single principle and are difficult to meet the requirements of the technical specification for the valuation of reference materials. Summary of the invention

[0006] In view of the technical problems existing in the background technology, the present application provides a method for accurately determining the lead content in lead concentrate, aiming to solve the technical problems that the existing lead content determination method has lead loss, the titration end point of the complexometric titration is not obvious, resulting in inaccurate test results, and the existing method for determining the lead content in standard substances for lead concentrate component analysis has a single principle and is difficult to meet the requirements of the technical specifications for the determination of standard substances.

[0007] The present application embodiment provides a method for accurately determining the lead content in a lead concentrate, comprising the following steps: S1. Wetting the lead concentrate sample with water, adding concentrated hydrochloric acid, concentrated nitric acid, and bromine water in sequence, and heating the sample to decompose it to obtain a first solution; S2, after cooling the first solution in step S1, add dilute sulfuric acid solution, heat until white smoke is emitted for 2-3 min, then cool, then add hydrobromic acid solution, heat until white smoke is emitted, then cool, then add water and continue to heat and boil, and keep for 8-12 min, after cooling, add anhydrous ethanol, and let stand at room temperature for 1.5-2.5 h; S3, using filter paper to filter the precipitate obtained after standing in step S2 and the supernatant to separate, the precipitate is washed with sulfuric acid lotion for multiple times and filtered and separated, until there is no iron ion, and then washed with clean water for multiple times and filtered and separated, and all the aforementioned filtering and separation processes use the same filter paper; The supernatant was combined with the filtrate obtained after washing the precipitate for multiple times, evaporated on an electric stove, and concentrated hydrochloric acid was added to make up to 100 mL in a volumetric flask. The absorbance was detected by an atomic absorption spectrometer, and the lead concentration was obtained from the working curve, thereby obtaining the lead content in the filtrate. ; S4, adding a hot acetic acid-ammonium acetate buffer solution to the precipitate after washing with clean water in step S3, heating until completely dissolved to obtain a second solution, continuing to filter the second solution using the same filter paper used in the filtering and separation process in step S3, and washing the filter paper multiple times with a hot acetic acid-ammonium acetate washing solution, while mixing the washing solution with the second solution, placing the washed filter paper in a zirconium crucible, and waiting for ashing; S5, adding hot water to the mixture of the washing solution and the second solution in step S4 and boiling, adding a saturated K2Cr2O7 solution, and continuing to boil for 8 to 12 minutes to convert the yellow precipitate into an orange precipitate, and standing for 1 to 12 hours; filtering and separating the precipitate and the supernatant after standing by using filter paper, and washing the container with hot water for at least 5 times, and washing the filter paper with hot water until there is no chromate ion or the filter paper is colorless; S6, using a hot hydrochloric acid-sodium chloride mixed solution to dissolve the precipitate obtained by separation and filtration in step S5 to obtain a third solution, and continuing to use the mixed solution to wash the filter paper in step S5 multiple times, and mixing the washing solution after washing with the third solution; The washed filter paper is placed in the zirconium crucible containing the filter paper in step S4, and roasted at 650-750°C. After cooling, an alkaline solvent and sodium peroxide are added, and the roasting is continued to be kept at 650-750°C for 5-10 min. After cooling, the crucible is placed in a beaker, and hot water is added to heat and boil to decompose the peroxide therein until it is completely dissolved. The crucible is washed out with water, and hydrochloric acid is added to the beaker. The solution is transferred to a 100 mL volumetric flask, and the absorbance is detected by an atomic absorption spectrometer after constant volume and dilution. The lead concentration is checked from the working curve to obtain the lead content in the filter residue. ; S7, dilute the mixture of the washing solution and the third solution in step S6 with water, add potassium iodide and let stand for 2-4 min, then titrate with sodium thiosulfate standard solution until the solution turns light yellow, add starch solution as an indicator, and continue titrating until the blue-green color disappears as the end point, calculate the titer of sodium thiosulfate standard solution to lead standard solution, and then obtain the lead content in the precipitate. ; S8. Make a full program blank with the sample; S9, the final lead content in the lead concentrate sample is the lead content in the filtrate of step S3 , Step S6 Lead content in the filter residue The lead content in the precipitate of step S7 The sum of .

[0008] In the technical scheme of the embodiment of the present application, another principle determination method is provided for the fixed value analysis of the lead content in the lead concentrate - redox titration method, first the lead concentrate sample is decomposed with concentrated hydrochloric acid, concentrated nitric acid and bromine water, then dilute sulfuric acid and hydrobromic acid are added to eliminate the interference of elements such as arsenic, antimony and tin in the sample, the lead in the sample is precipitated in the form of lead sulfate, acetic acid-ammonium acetate buffer solution is used to dissolve the lead sulfate precipitate, and then potassium dichromate solution is added to make the lead generate lead chromate precipitate, and the lead content in the precipitate is titrated and measured by redox titration; this method overcomes the problem that when the traditional EDTA complexometric titration method turns into bright yellow as the titration end point, each tester has different judgments on the bright yellow, which may lead to the problem of low or high titration results; the titration end point color of the present method is the disappearance of blue-green color, which is clearer and is conducive to accurate judgment by testers, thereby improving the reliability of the determination of the lead content in the lead concentrate. The scheme also provides a new principle and method for determining lead content, which can be used in conjunction with the existing complexometric titration method to determine the lead content in lead concentrate component analysis standard materials, solving the technical problem that the existing method for determining the lead content in lead concentrate component analysis standard materials has a single principle and is difficult to meet the requirements of the technical specifications for standard material valuation.

[0009] In addition, the technical solution measures the lead content in the precipitate, filtrate and filter residue at the same time, and compensates for the lead that is easily lost when the lead content is measured in the prior art, making the measurement result more accurate, and having better application value for the mineral evaluation of lead concentrate. And in step S5, when washing the filter paper until there is no chromate ion, the solution uses hot water for washing, and the effect of hot water dissolving solids is good and the loss is small, which overcomes the traditional thinking of using hot ammonium acetate washing solution or other acetate solution to dissolve the lead precipitate in the EDTA complexometric titration method, and solves the problem of low results and loss of lead in the precipitate when washing with hot ammonium acetate or other washing solutions.

[0010] In some embodiments, in step S7, the lead content in the precipitate is The calculation formula is: %, in, -Mass fraction of lead in the precipitate, %; - Volume of titrant consumed, mL; - Volume of blank consumed titrant, mL; - Sample mass, g; -Titer, mg / mL.

[0011] In step S7, the preparation method of the sodium thiosulfate standard solution is as follows: 100 g of Na2S2O3·5H2O is weighed and placed in a 1000 mL beaker, 500 mL of a sodium carbonate solution with a concentration of 4 g / L is added, and the solution is transferred into a 10 L brown reagent bottle, and the solution is diluted to 10 L with boiled and cooled distilled water, 1 mL of chloroform is added, and the solution is allowed to stand for two weeks to obtain a sodium thiosulfate standard solution; the sodium thiosulfate standard solution needs to be filtered when used, and 1 mL of chloroform is added to mix well, and the solution is allowed to stand for 2 hours before use.

[0012] The concentration of the lead standard solution is 4 mg / mL and the volume is 10 mL. The titer of the sodium thiosulfate standard solution to the lead standard solution is calculated as follows: , in, The volume of sodium thiosulfate standard solution consumed to titrate the lead standard solution, mL.

[0013] In this embodiment, when sodium thiosulfate redox titration is used, potassium iodide is first added as a reducing agent, and dichromate ions oxidize iodide ions to precipitate a certain amount of iodine. This method utilizes the reduction effect of iodine ions to react with oxidizing substances (i.e., dichromate ions) to generate free iodine, and then titrate with sodium thiosulfate standard solution to measure the content of dichromate ions, and then obtain the content of lead ions. When calculating, the titration degree of sodium thiosulfate standard solution to lead is first calculated based on the volume of sodium thiosulfate standard solution consumed when titrating the lead standard solution, and then the mass fraction of lead in the precipitate titrated with sodium thiosulfate standard solution is calculated according to the formula.

[0014] In some embodiments, in step S3 and step S6, the working curve is established by accurately pipetting 0.00, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of lead single element standard solution into 6 100 mL volumetric flasks, fixing the volume, and shaking well to obtain standard working solutions with mass concentrations of 0.00 μg / mL, 2.00 μg / mL, 4.00 μg / mL, 6.00 μg / mL, 8.00 μg / mL, and 10.00 μg / mL, respectively, and detecting the absorbance by an atomic absorption spectrometer. The working curve is plotted with the lead concentration as the horizontal axis and the absorbance as the vertical axis.

[0015] In step S3, the lead content in the filtrate The calculation formula is: , in, -Mass fraction of lead in the filtrate, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtrate constant volume, mL; - Sample mass, g; In step S6, the lead content in the filter residue is The calculation formula is: , in, -Mass fraction of lead in the filter residue, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtration residue fixed volume, mL; - dilution factor; - Sample mass, g.

[0016] In this embodiment, the atomic absorption spectrometer is used to detect absorbance to respectively determine the lead content in the filtrate and the filter residue, thereby correcting the problem that the prior art only measures the lead in the precipitate when determining the lead content in the mineral, causing lead loss and thus leading to inaccurate test results.

[0017] In some embodiments, in step S1, the mass of the lead concentrate sample is 0.20-0.30 g, the accuracy is 0.0001 g, and the particle size is not greater than 0.074 mm; in step S5, the amount of the K2Cr2O7 saturated solution added is 20-30 mL, and the preparation method is to dissolve K2Cr2O7 in water to a saturated state; in step S7, the mixed solution of the washing liquid and the third solution is diluted with water to 200 mL, the amount of potassium iodide added is 2-4 g, the amount of the starch solution added is 3-6 mL, and the mass percentage concentration is 0.5%.

[0018] In step S1, the amount of concentrated hydrochloric acid added is 12-18 mL, and the volume ratio of concentrated hydrochloric acid, concentrated nitric acid and bromine water is 3:2:(0.1-0.3); in step S2, the solute mass fraction of the dilute sulfuric acid is 48%-50%, and the density of the hydrobromic acid is 1.5g / mL, the added amount of the dilute sulfuric acid and the hydrobromic acid is 8-12 mL, the added amount of water is 80-120 mL, and the added amount of anhydrous ethanol is 8-12 mL.

[0019] In step S3, the solute mass fraction of the sulfuric acid washing solution is 1.5% to 2.0%. The method for judging whether the precipitate has iron ions is to use potassium thiocyanate solution to test. If it turns red, it means that there are still iron ions, and then continue washing. If it does not change color, it means that the iron ions have been completely removed. The amount of concentrated hydrochloric acid added is 12 to 18 mL; In step S4, the concentration of the hot acetic acid-ammonium acetate buffer solution is 240-250 g / L, the amount added is 50-70 mL, and the mass percentage concentration of the hot acetic acid-ammonium acetate washing solution is 4%-6%; In step S5, when hot water is added to boil, the amount of hot water added is such that the total amount of the mixed solution is 180-220 mL. The method for determining whether there are complex acid ions is to use a 0.1 mol / L silver nitrate solution for testing. If there is no yellow precipitate, there is no complex acid ion. In step S6, the amount of the alkaline solvent added is 1-3 g, the amount of the sodium peroxide added is 0.3-0.7 g, the amount of the hot water added is 40-60 mL, the amount of the hydrochloric acid added to the beaker is 12-18 mL, and the density is 1.16g / mL~1.19g / mL, the dilution multiple is 10 times.

[0020] The temperature of the hot acetic acid-ammonium acetate buffer solution, the hot acetic acid-ammonium acetate washing solution, the hot hydrochloric acid-sodium chloride mixed solution and the hot water is 90-110°C.

[0021] In this embodiment, by limiting the dosage, concentration and measurement conditions of the reagents in each step, the measurement accuracy of the lead content in the filtrate, filter residue and precipitate of the technical solution of the present application is ensured.

[0022] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0023] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0025] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0028] The existing lead concentrate detection methods mostly measure the lead precipitate content dissolved in the buffer solution as the lead content in the mineral, which causes the lead in the filtrate or filter residue to be lost, resulting in inaccurate lead content determination results; and the existing technology mainly uses the principle of complexometric titration, and mostly uses EDTA standard titration solution for titration, and adds a small amount of ascorbic acid, and uses dimethylol orange as an indicator. The solution turns bright yellow as the titration end point, and each tester's judgment standard for bright yellow is relatively subjective, and there is no unified standard, which may cause the titration result to be too low or too high, affecting the final test result. In addition, the technical specification for the determination of standard substances proposes to use two or more accurate methods with different principles to determine the value of it, so as to improve the reliability of the assignment. In the existing technology, the determination method of lead content in the standard substance for lead concentrate component analysis, the popular detection method mostly uses the method based on the principle of complexometric titration, the method principle is single, and it is difficult to meet the requirements of the technical specification for the determination of standard substances.

[0029] In order to solve the technical problems that the existing lead content determination methods have lead loss, the titration endpoint of the complexometric titration method is not obvious, resulting in inaccurate test results, and the existing lead content determination method in the lead concentrate component analysis standard material has a single principle and is difficult to meet the requirements of the standard material value specification, the present application provides an accurate determination method for the lead content in lead concentrate, and provides another principle determination method for the value analysis of the lead content in lead concentrate - redox titration method, which overcomes the problem that when the traditional EDTA complexometric titration method turns into bright yellow as the titration endpoint, each tester has different judgments on the bright yellow, which may lead to low or high titration results; the titration endpoint color of the method is blue-green disappearance, which is clearer and is conducive to accurate judgment by testers, thereby improving the reliability of lead content determination in lead concentrate; and the scheme provides a new determination principle and method for lead content, which can be used in conjunction with the existing complexometric titration method for the determination of lead content in the lead concentrate component analysis standard material, solving the technical problems that the existing lead content determination method in the lead concentrate component analysis standard material has a single principle and is difficult to meet the requirements of the standard material value specification. In addition, the technical solution simultaneously measures the lead content in the precipitate, filtrate and filter residue, and compensates for the lead that is easily lost when the lead content is measured in the prior art, making the measurement result more accurate and having better application value for the mineral evaluation of lead concentrate.

[0030] For the convenience of explanation, the following examples are described by taking the method for accurately determining the lead content in a lead concentrate in an example of the present application.

[0031] The present application embodiment provides a method for accurately determining the lead content in lead concentrate, comprising the following steps: S1. Wetting the lead concentrate sample with water, adding concentrated hydrochloric acid, concentrated nitric acid, and bromine water in sequence, and heating the sample to decompose it to obtain a first solution; S2, after cooling the first solution in step S1, add dilute sulfuric acid solution, heat until white smoke appears for 2-3 min, then cool, then add hydrobromic acid solution, heat until white smoke appears, then cool, then add water and continue to heat and boil, and keep for 8-12 min, after cooling, add anhydrous ethanol, and let stand at room temperature for 1.5-2.5 h; S3, using filter paper to filter the precipitate obtained after standing in step S2 and the supernatant to separate, the precipitate is washed with sulfuric acid lotion for multiple times and filtered and separated, until there is no iron ion, and then washed with clean water for multiple times and filtered and separated, and all the aforementioned filtering and separation processes use the same filter paper; The supernatant was combined with the filtrate obtained after washing the precipitate several times, evaporated on an electric stove, and concentrated hydrochloric acid was added to make up to 100 mL in a volumetric flask. The absorbance was detected by atomic absorption spectrometer, and the lead concentration was obtained from the working curve, thereby obtaining the lead content in the filtrate. ; S4, adding a hot acetic acid-ammonium acetate buffer solution to the precipitate after washing with clean water in step S3, heating until completely dissolved to obtain a second solution, continuing to filter the second solution using the filter paper used in the filtering and separation process in step S3, and washing the filter paper multiple times with a hot acetic acid-ammonium acetate washing solution, while mixing the washing solution with the second solution, placing the washed filter paper in a zirconium crucible, and waiting for ashing; S5, adding hot water to the mixture of the washing solution and the second solution in step S4 and boiling, adding a saturated K2Cr2O7 solution, and continuing to boil for 8 to 12 minutes to convert the yellow precipitate into an orange precipitate, and standing for 1 to 12 hours; filtering and separating the precipitate and the supernatant after standing by using filter paper, and washing the container with hot water for at least 5 times, and washing the filter paper with hot water until there is no chromate ion or the filter paper is colorless; S6, using a hot hydrochloric acid-sodium chloride mixed solution to dissolve the precipitate obtained by separation and filtration in step S5 to obtain a third solution, and continuing to use the mixed solution to wash the filter paper in step S5 multiple times, and mixing the washing solution after washing with the third solution; The washed filter paper is placed in the zirconium crucible containing the filter paper in step S4, and roasted at 650-750°C. After cooling, an alkaline solvent and sodium peroxide are added, and the roasting is continued to be kept at 650-750°C for 5-10 min. After cooling, the crucible is placed in a beaker, and hot water is added to heat and boil to decompose the peroxide therein until it is completely dissolved. The crucible is washed out with water, and hydrochloric acid is added to the beaker. The solution is transferred to a 100 mL volumetric flask, and the absorbance is detected by an atomic absorption spectrometer after constant volume and dilution. The lead concentration is checked from the working curve to obtain the lead content in the filter residue. ; S7, dilute the mixture of the washing solution and the third solution in step S6 with water, add potassium iodide and let stand for 2-4 min, then titrate with sodium thiosulfate standard solution until the solution turns light yellow, add starch solution as an indicator, and continue titrating until the blue-green color disappears as the end point, calculate the titer of sodium thiosulfate standard solution to lead standard solution, and then obtain the lead content in the precipitate. ; S8. Make a full program blank with the sample; S9, the final lead content in the lead concentrate sample is the lead content in the filtrate of step S3 , Step S6 Lead content in the filter residue The lead content in the precipitate of step S7 The sum of .

[0032] The technical solution of this embodiment provides another principle determination method for the fixed value analysis of the lead content in lead concentrate - redox titration. This method overcomes the problem that when the traditional EDTA complexometric titration method uses the change to bright yellow as the titration endpoint, each tester has different judgments on the bright yellow, which may lead to a low or high titration result. The titration endpoint color of this method is the disappearance of blue-green, which is clearer and is conducive to the accurate judgment of the tester, thereby improving the reliability of the determination of the lead content in the lead concentrate. In addition, this solution provides a new determination principle and method for lead content, which can be used in conjunction with the existing complexometric titration method for the determination of the lead content in the standard substance for the analysis of the composition of lead concentrate, solving the technical problem that the existing determination method of the lead content in the standard substance for the analysis of the composition of lead concentrate has a single principle and is difficult to meet the requirements of the technical specifications for the fixed value of the standard substance.

[0033] In addition, the technical solution simultaneously measures the lead content in the precipitate, filtrate and filter residue, and compensates for the lead that is easily lost when the lead content is measured in the prior art, so that the measurement result is more accurate, and has better application value for the mineral evaluation of lead concentrate. In step S5, when washing the filter paper until there is no chromate ion, the technical solution uses hot water for washing. Hot water has a good effect of dissolving solids and small losses. The lead result in the precipitate is accurate, which solves the problem of lead loss in the precipitate. Hot water is not only simple to make, but also environmentally friendly and more convenient to operate. It overcomes the traditional thinking of using hot ammonium acetate washing solution or other acetate solution to dissolve the lead precipitate in the EDTA complexometric titration method, and solves the problem of low results and lead loss in the precipitate when washing with hot ammonium acetate or other washing solutions.

[0034] Further, in some embodiments, in step S7, the lead content in the precipitate is The calculation formula is: %, in, -Mass fraction of lead in the precipitate, %; - Volume of titrant consumed, mL; - Volume of blank consumed titrant, mL; - Sample mass, g; -Titer, mg / mL.

[0035] In step S7, the preparation method of the sodium thiosulfate standard solution is as follows: 100 g of Na2S2O3·5H2O is weighed and placed in a 1000 mL beaker, 500 mL of a 4 g / L sodium carbonate solution is added, and the solution is transferred into a 10 L brown reagent bottle, and the solution is diluted to 10 L with boiled and cooled distilled water, and 1 mL of chloroform is added, and the solution is allowed to stand for two weeks to obtain a sodium thiosulfate standard solution; the sodium thiosulfate standard solution needs to be filtered when used, and 1 mL of chloroform is added to mix well, and the solution is allowed to stand for 2 hours before use.

[0036] The concentration of the lead standard solution is 4 mg / mL and the volume is 10 mL. The titer of the sodium thiosulfate standard solution to the lead standard solution is calculated as follows: , in, is the volume of sodium thiosulfate standard solution consumed in titrating the lead standard solution, mL.

[0037] In the technical solution of the embodiment of the present application, when the sodium thiosulfate redox titration method is used, potassium iodide is first added as a reducing agent, and the dichromate ions oxidize the iodide ions to precipitate a certain amount of iodine. This method utilizes the reduction of iodide ions to react with oxidizing substances (i.e., dichromate ions) to generate free iodine, and then titrate with a sodium thiosulfate standard solution to measure the content of dichromate ions, and then obtain the content of lead ions. When calculating, the titration degree of the sodium thiosulfate standard solution to lead is first calculated based on the volume of the sodium thiosulfate standard solution consumed when titrating the lead standard solution, and then the mass fraction of lead in the precipitate titrated with the sodium thiosulfate standard solution is calculated according to the formula.

[0038] Further, in some embodiments, in step S3 and step S6, the working curve is established by accurately pipetting 0.00, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of lead single element standard solution into 6 100 mL volumetric flasks, fixing the volume, and shaking well to obtain standard working solutions with mass concentrations of 0.00 μg / mL, 2.00 μg / mL, 4.00 μg / mL, 6.00 μg / mL, 8.00 μg / mL, and 10.00 μg / mL, respectively, and detecting the absorbance by an atomic absorption spectrometer, and plotting the working curve with the lead concentration as the horizontal axis and the absorbance as the vertical axis.

[0039] In step S3, the lead content in the filtrate The calculation formula is: , in, -Mass fraction of lead in the filtrate, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtrate constant volume, mL; - Sample mass, g; In step S6, the lead content in the filter residue is The calculation formula is: %, in, -Mass fraction of lead in the filter residue, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtration residue fixed volume, mL; - dilution factor; - Sample mass, g.

[0040] In the technical solution of the embodiment of the present application, an atomic absorption spectrometer is used to detect absorbance to respectively determine the lead content in the filtrate and the residue, thereby correcting the problem that the prior art only measures the lead in the precipitate when determining the lead content in the mineral, causing lead loss and leading to inaccurate test results.

[0041] Furthermore, in some embodiments, in step S1, the mass of the lead concentrate sample is 0.20~0.30 g, the accuracy is 0.0001 g, and the particle size is not greater than 0.074 mm; in step S5, the amount of K2Cr2O7 saturated solution added is 20~30 mL, and the preparation method is to dissolve K2Cr2O7 in water to a saturated state; in step S7, the mixed solution of the washing liquid and the third solution is diluted with water to 200 mL, the amount of potassium iodide added is 2~4 g, the amount of starch solution added is 3~6 mL, and the mass percentage concentration is 0.5%.

[0042] In step S1, the amount of concentrated hydrochloric acid added is 12-18 mL, and the volume ratio of concentrated hydrochloric acid, concentrated nitric acid and bromine water is 3:2:(0.1-0.3); in step S2, the solute mass fraction of dilute sulfuric acid is 48%-50%, and the density of hydrobromic acid is 1.5g / mL (the density of the solution at 20°C is 1.5g / mL), the amount of dilute sulfuric acid and hydrobromic acid added is 8~12 mL, the amount of water added is 80~120 mL, and the amount of anhydrous ethanol added is 8~12 mL.

[0043] In step S3, the solute mass fraction of the sulfuric acid washing solution is 1.5% to 2.0%. The method for judging whether the precipitate has iron ions is to use potassium thiocyanate solution to test. If it turns red, it means that there are still iron ions, and then continue washing. If it does not change color, it means that the iron ions have been completely removed. The amount of concentrated hydrochloric acid added is 12 to 18 mL; In step S4, the concentration of the hot acetic acid-ammonium acetate buffer solution is 240-250 g / L, the amount added is 50-70 mL, and the mass percentage concentration of the hot acetic acid-ammonium acetate washing solution is 4%-6%; In step S5, when hot water is added to boil, the amount of hot water added is such that the total amount of the mixed solution is 180-220 mL. The method for determining whether there are complex acid ions is to use a 0.1 mol / L silver nitrate solution for testing. If there is no yellow precipitate, there is no complex acid ion. In step S6, the amount of alkaline solvent added is 1-3 g, the amount of sodium peroxide added is 0.3-0.7 g, the amount of hot water added is 40-60 mL, the amount of hydrochloric acid added to the beaker is 12-18 mL, and the density is 1.16g / mL~1.19g / mL (density of the solution at 20°C), the dilution multiple is 10 times.

[0044] The temperature of the hot acetic acid-ammonium acetate buffer solution, the hot acetic acid-ammonium acetate washing solution, the hot hydrochloric acid-sodium chloride mixed solution and the hot water is 90~110℃.

[0045] In the technical solution of the embodiment of the present application, the measurement accuracy of the lead content in the filtrate, filter residue and precipitate is ensured by limiting the dosage, concentration and measurement conditions of the reagents in each step.

[0046] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0047] Example 1 This embodiment provides a method for accurately determining the lead content in lead concentrate, comprising the following steps: S1. Place 0.22 g of lead concentrate sample (accuracy is 0.0001 g, particle size is not more than 0.074 mm) in a 400 mL beaker, add a small amount of water to moisten, add 15 mL of concentrated hydrochloric acid, cover with a watch glass, place on an electric furnace and heat for 5 min, remove the beaker and cool it slightly, then add 10 mL of concentrated nitric acid and 1 mL of bromine water, and heat gradually until the yellow smoke disappears, so that the sample is decomposed to obtain the first solution; S2, after cooling the first solution in step S1, add 10 mL of dilute sulfuric acid solution with a solute to solvent volume ratio of 1:1, heat until white smoke appears for 2-3 min, cool, and then add Heat 10 mL of 1.5 g / mL hydrobromic acid solution until white smoke appears, then cool it down, rinse the watch glass and the cup wall with water, reheat it until thick white smoke appears, then cool it down to room temperature, add 100 mL of water, continue heating and boiling, and keep it for 10 min. After cooling, add 10 mL of anhydrous ethanol, and let it stand at room temperature for 2 h; S3, adopt slow quantitative filter paper decantation method to filter and separate the precipitate obtained after step S2 is left to stand and the supernatant, filter the supernatant into a 400 mL beaker, wash the precipitate with sulfuric acid lotion with a solute to solvent volume ratio of 1:50 for multiple times and filter and separate, use potassium thiocyanate solution to check, if red indicates that there are still iron ions, continue washing, if it does not change color, it indicates that the iron has been removed, until there are no iron ions, wash it with clean water 3 times and filter and separate, all the aforementioned filtering and separation processes use the same filter paper; The supernatant and the filtrate obtained after multiple washings of the precipitate were combined into the same beaker, evaporated on an electric stove, and 15 mL of concentrated hydrochloric acid was added to a 100 mL volumetric flask. The absorbance was detected by an atomic absorption spectrometer, and the lead concentration was obtained from the working curve, thereby obtaining the lead content in the filtrate. ; The working curve was established by accurately transferring 0.00, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of the single-element lead standard solution into 6 100 mL volumetric flasks, fixing the volume, and shaking well to obtain standard working solutions with mass concentrations of 0.00 μg / mL, 2.00 μg / mL, 4.00 μg / mL, 6.00 μg / mL, 8.00 μg / mL, and 10.00 μg / mL, respectively. The absorbance was detected by atomic absorption spectrometer, and the working curve was drawn with the lead concentration as the horizontal axis and the absorbance as the vertical axis. Lead content in filtrate The calculation formula is: =0.25%, in, -Mass fraction of lead in the filtrate, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtrate constant volume, mL; - Sample mass, g; S4, adding the precipitate after washing with clean water in step S3 to 60 mL of hot acetic acid-ammonium acetate buffer solution with a temperature of 100° C. and a concentration of 244 g / L, heating until completely dissolved to obtain a second solution, continuing to filter the second solution using the filter paper used in the filtering and separation process in step S3, and washing the filter paper multiple times with a hot acetic acid-ammonium acetate washing solution with a mass percentage concentration of 5%, while mixing the washing solution with the second solution, placing the washed filter paper in a zirconium crucible, and waiting for ashing; S5. Add hot water to 200 mL of the mixture of the washing solution and the second solution in step S4 and boil it, add 25 mL of saturated K2Cr2O7 solution, continue boiling for 10 min to convert the yellow precipitate into orange precipitate, and let it stand for 2 h; filter the precipitate and the supernatant after standing by using filter paper, and wash the container with hot water for at least 5 times, and wash the filter paper with hot water until there is no chromate ion or the filter paper is colorless; S6, using a hot hydrochloric acid-sodium chloride mixed solution to dissolve the precipitate obtained by separation and filtration in step S5 to obtain a third solution, and continuing to use the mixed solution to wash the filter paper in step S5 multiple times, and mixing the washing solution after washing with the third solution; The washed filter paper is placed in the zirconium crucible containing the filter paper in step S4, and roasted at 700°C. After cooling, 2 g of alkaline solvent and 0.5 g of sodium peroxide are added, and the roasting is continued to 700°C for 8 min. After cooling, the crucible is placed in a beaker, 50 mL of hot water is added, and a watch glass is covered. The crucible is heated to boil on an electric hot plate to decompose the peroxide therein until it is completely dissolved. The crucible is washed out with water, 15 mL of hydrochloric acid is added to the beaker, and the solution is transferred to a 100 mL volumetric flask. After the volume is fixed and diluted 10 times, the absorbance is detected by an atomic absorption spectrometer. The lead concentration is checked from the working curve to obtain the lead content in the filter residue. ; Lead content in filter residue The calculation formula is: =0.082%, in, -Mass fraction of lead in the filter residue, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtration residue fixed volume, mL; - dilution factor; - Sample mass, g; S7, dilute the mixed solution of the washing solution and the third solution in step S6 with water to 200 mL, add 3 g of potassium iodide, let stand for 3 min, and then titrate with sodium thiosulfate standard solution until the solution turns light yellow, and at the same time add 5 mL of starch solution with a mass percentage concentration of 0.5% as an indicator, and continue to titrate until the blue-green color disappears as the end point, calculate the titer of the sodium thiosulfate standard solution to the lead standard solution, and then obtain the lead content in the precipitate. ; The preparation method of sodium thiosulfate standard solution is as follows: weigh 100g of Na2S2O3·5H2O and place it in a 1000mL beaker, add 500mL of 4g / L sodium carbonate solution, and transfer it to a 10L brown reagent bottle. Dilute to 10L with boiled and cooled distilled water, add 1mL of chloroform, and let stand for two weeks to obtain the sodium thiosulfate standard solution; the sodium thiosulfate standard solution needs to be filtered when used, and 1mL of chloroform is added to mix, and it is allowed to stand for 2 hours before use; The concentration of the lead standard solution is 4 mg / mL and the volume is 10 mL. The titer of the sodium thiosulfate standard solution to the lead standard solution is calculated as follows: , in, V is the volume of sodium thiosulfate standard solution consumed in titrating the lead standard solution, mL; Lead content in the precipitate The calculation formula is: %=66.49%, in, -Mass fraction of lead in the precipitate, %; - Volume of titrant consumed, mL; - Volume of blank consumed titrant, mL; - Sample mass, g; - Titer, mg / mL; S8. Make a full program blank with the sample; S9, the final lead content in the lead concentrate sample is the lead content in the filtrate of step S3 , Step S6 Lead content in the filter residue The lead content in the precipitate of step S7 The sum of ,Right now, = + + =0.25%+0.082%+66.49%=66.82%, indicating that the lead content in the lead concentrate sample of this embodiment is 66.82%.

[0048] Example 2 This embodiment provides a method for accurately determining the lead content in lead concentrate. Compared with Example 1, the difference is that 0.27 g of lead concentrate samples from different sources are taken in step S1, and the rest is roughly the same as Example 1, which will not be repeated here. Finally, the total lead content in the lead concentrate sample is obtained. =0.23%+0.076%+60.80%=61.11%.

[0049] Example 3 This embodiment provides a method for accurately determining the lead content in lead concentrate. Compared with Example 1, the difference is that 0.30 g of lead concentrate samples from different sources are taken in step S1, and the rest is roughly the same as Example 1, which will not be repeated here. Finally, the total lead content in the lead concentrate sample is obtained. =0.22%+0.053%+57.85%=58.12%.

[0050] Example 4 This embodiment provides a method for accurately determining the lead content in lead concentrate. Compared with Example 1, the difference is that in step S1, the lead concentrate sample is the national standard material of lead concentrate GBW (E) 070173 (lead content is 57.44±0.16%), and the rest is roughly the same as Example 1, which will not be repeated here.

[0051] The total lead content in the sample was determined by the method of this embodiment. =0.18%+0.030%+57.28%=57.49%, the standard value of the national standard substance of lead concentrate is 57.44±0.16%, and the measurement result is within the standard value range, indicating the accuracy of the technical solution of this embodiment in determining the lead content.

[0052] Comparative Example 1 Comparative Example 1 provides a method for accurately determining the lead content in a lead concentrate. Compared with Example 4, the difference is that in step S5, a hot ammonium acetate solution (concentration of 20 g / L) is used to wash the container at least 5 times, and the filter paper is washed with a hot ammonium acetate solution until there is no chromate ion or the filter paper is colorless. The rest is roughly the same as Example 4 and will not be repeated here.

[0053] The total lead content in the sample was determined =0.15%+0.023%+56.94%=57.11%. The standard value of the national standard substance of lead concentrate is 57.44±0.16%. The measurement result of comparative example 1 is not within the standard value range, indicating that the result will be low when washing with hot ammonium acetate solution, and the lead in the precipitate is lost.

[0054] Comparative Example 2 Comparative Example 2 provides a method for accurately determining the lead content in a lead concentrate. Compared with Example 4, in step S5 and step S7, EDTA standard titration solution is used for titration, and a small amount of ascorbic acid is added, and xylenol orange is used as an indicator to determine the lead content in the precipitate. The rest is roughly the same as Example 4 and will not be repeated here.

[0055] The total lead content in the sample was determined =0.15%+0.046%+57.40%=57.60%, the standard value of the national standard substance of lead concentrate is 57.44±0.16%, and comparative example 2 adopts the method of titration with EDTA standard titration solution. Although the titration end point is unclear, which may lead to a higher result, the measurement result is still within the standard value range; while the prior art only adopts the method based on the principle of complexometric titration, which is difficult to meet the requirements of the technical specification for the valuation of standard substances, which proposes to use two or more accurate methods based on different principles for valuation. The technical solution of the application provides a method for accurately determining the lead content based on another principle, which solves the technical problem.

[0056] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for accurately determining the lead content in lead concentrate, characterized in that: The following steps are involved: S1. Wetting the lead concentrate sample with water, adding concentrated hydrochloric acid, concentrated nitric acid and bromine water in sequence, and heating to obtain a first solution; S2, adding a dilute sulfuric acid solution to the first solution, heating until white smoke is emitted, and then cooling, adding a hydrobromic acid solution, heating until white smoke is emitted, and then cooling, adding water, boiling, cooling, adding anhydrous ethanol, and standing at room temperature; S3, using filter paper to filter and separate the precipitate after standing in step S2 from the supernatant, washing the precipitate with sulfuric acid washing solution and clean water for multiple times in sequence and filtering and separating, all the aforementioned filtering and separations are performed using the same filter paper; combining the supernatant and the filtrate after multiple washings, evaporating to dryness, adding concentrated hydrochloric acid to make up the volume, detecting the absorbance with an atomic absorption spectrometer, and finding the lead concentration from the working curve, thereby obtaining the lead content in the filtrate ; S4, adding a hot acetic acid-ammonium acetate buffer solution to the precipitate washed in step S3, heating until completely dissolved to obtain a second solution, filtering the second solution with the same filter paper as in step S3, and washing the filter paper with a hot acetic acid-ammonium acetate washing solution for multiple times, mixing the washed washing solution with the second solution to obtain a mixed solution, and placing the washed filter paper in a zirconium crucible to wait for ashing; S5, heating the mixed solution of step S4 to boil, adding a saturated solution of K2Cr2O7, and continuing to boil until the yellow precipitate is transformed into an orange precipitate, and letting it stand; filtering and separating the precipitate from the supernatant after standing by using filter paper, and washing the container and the filter paper with hot water for multiple times; S6, using a hot hydrochloric acid-sodium chloride mixed solution to dissolve the precipitate obtained in step S5 to obtain a third solution, using the mixed solution to wash the filter paper in step S5 multiple times, and mixing the washing solution after washing with the third solution; The washed filter paper is placed in the zirconium crucible of step S4 and roasted. After cooling, an alkaline solvent and sodium peroxide are added to continue roasting. After cooling, the crucible is placed in a beaker and heated with hot water to boil. After washing the crucible, hydrochloric acid is added to the beaker. After constant volume and dilution, the absorbance is detected by an atomic absorption spectrometer. The lead concentration is checked from the working curve to obtain the lead content in the filter residue. ; S7, dilute the mixture of the washing solution and the third solution in step S6 with water, add potassium iodide and let stand for 2-4 min, then titrate with sodium thiosulfate standard solution until the solution turns light yellow, add starch solution as an indicator, and continue titrating until the blue-green color disappears as the end point, calculate the titer of sodium thiosulfate standard solution to lead standard solution, and then obtain the lead content in the precipitate. ; S8. Make a full program blank with the sample; S9, the final lead content in the lead concentrate sample is the lead content in the filtrate of step S3 , Step S6 Lead content in the filter residue The lead content in the precipitate of step S7 The sum of .

2. The method for accurately determining the lead content in lead concentrate according to claim 1, characterized in that: In step S7, the lead content in the precipitate is The calculation formula is: %， in, -Mass fraction of lead in the precipitate, %; - Volume of titrant consumed, mL; - Volume of blank consumed titrant, mL; - Sample mass, g; -Titer, mg / mL.

3. The method for accurately determining the lead content in lead concentrate according to claim 2, characterized in that: In step S7, the preparation method of the sodium thiosulfate standard solution is as follows: 100 g of Na2S2O3·5H2O is weighed and placed in a 1000 mL beaker, 500 mL of a sodium carbonate solution with a concentration of 4 g / L is added, and the solution is transferred into a 10 L brown reagent bottle, and the solution is diluted to 10 L with boiled and cooled distilled water, 1 mL of chloroform is added, and the solution is allowed to stand for two weeks to obtain a sodium thiosulfate standard solution; the sodium thiosulfate standard solution needs to be filtered when used, and 1 mL of chloroform is added to mix well, and the solution is allowed to stand for 2 hours before use.

4. The method for accurately determining the lead content in lead concentrate according to claim 3, characterized in that: The concentration of the lead standard solution is 4 mg / mL and the volume is 10 mL. The titer of the sodium thiosulfate standard solution to the lead standard solution is calculated as follows: ， in, The volume of sodium thiosulfate standard solution consumed to titrate the lead standard solution, mL.

5. The method for accurately determining the lead content in lead concentrate according to claim 1, characterized in that: In step S3 and step S6, the working curve is established by accurately transferring 0.00, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of the lead single element standard solution into 6 100 mL volumetric flasks, fixing the volume, and shaking well to obtain standard working solutions with mass concentrations of 0.00 μg / mL, 2.00 μg / mL, 4.00 μg / mL, 6.00 μg / mL, 8.00 μg / mL, and 10.00 μg / mL, respectively. The absorbance is detected by an atomic absorption spectrometer, and the working curve is plotted with the lead concentration as the horizontal axis and the absorbance as the vertical axis.

6. The method for accurately determining the lead content in lead concentrate according to claim 5, characterized in that: In step S3, the lead content in the filtrate The calculation formula is: %， in, -Mass fraction of lead in the filtrate, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtrate fixed volume, mL; - Sample mass, g; In step S6, the lead content in the filter residue is The calculation formula is: %， in, -Mass fraction of lead in the filter residue, %; - The lead concentration is obtained from the working curve, mg / L; - The lead concentration in the blank sample is obtained from the working curve, mg / L; -Filtration residue fixed volume, mL; - dilution factor; - Sample mass, g.

7. The method for accurately determining the lead content in lead concentrate according to claim 1, characterized in that: In step S1, the mass of the lead concentrate sample is 0.20-0.30 g, the accuracy is 0.0001 g, and the particle size is not greater than 0.074 mm; in step S5, the amount of the K2Cr2O7 saturated solution added is 20-30 mL; in step S7, the mixed solution of the washing liquid and the third solution is diluted with water to 200 mL, the amount of potassium iodide added is 2-4 g, the amount of the starch solution added is 3-6 mL, and the mass percentage concentration is 0.5%.

8. The method for accurately determining the lead content in lead concentrate according to claim 7, characterized in that: In step S1, the amount of concentrated hydrochloric acid added is 12-18 mL, and the volume ratio of concentrated hydrochloric acid, concentrated nitric acid and bromine water is 3:2:(0.1-0.3); in step S2, the solute mass fraction of the dilute sulfuric acid is 48%-50%, and the density of the hydrobromic acid is 1.5g / mL, the added amount of the dilute sulfuric acid and the hydrobromic acid is 8-12 mL, the added amount of water is 80-120 mL, and the added amount of anhydrous ethanol is 8-12 mL.

9. The method for accurately determining the lead content in lead concentrate according to claim 8, characterized in that: In step S3, the solute mass fraction of the sulfuric acid washing solution is 1.5% to 2.0%. The precipitate is first washed with sulfuric acid washing solution for multiple times and filtered and separated until there is no iron ion, and then washed with clean water for multiple times and filtered and separated; the method for judging whether the precipitate has iron ions is to use potassium thiocyanate solution to test, if it turns red, it indicates that there are still iron ions, then continue washing, if it does not change color, it indicates that the iron ions have been removed; the amount of concentrated hydrochloric acid added is 12 to 18 mL; In step S4, the concentration of the hot acetic acid-ammonium acetate buffer solution is 240-250 g / L, the amount added is 50-70 mL, and the mass percentage concentration of the hot acetic acid-ammonium acetate washing solution is 4%-6%; In step S5, when adding hot water to boil, the amount of hot water added is to add the mixed solution to a total amount of 180-220 mL, and the hot water is used to filter paper several times until there is no chromate ion or the filter paper is colorless; the method for judging whether there is complex acid ion is to use a 0.1 mol / L silver nitrate solution for testing, and no yellow precipitate means no complex acid ion; In step S6, the calcination temperature is 650-750°C, the amount of the alkaline solvent added is 1-3 g, the amount of sodium peroxide added is 0.3-0.7 g, the amount of hot water added to the beaker is 40-60 mL, the amount of hydrochloric acid added to the beaker is 12-18 mL, and the density is 1.16g / mL~1.19g / mL, the dilution multiple is 10 times.

10. The method for accurately determining the lead content in lead concentrate according to claim 1, characterized in that: The temperature of the hot acetic acid-ammonium acetate buffer solution, the hot acetic acid-ammonium acetate washing solution, the hot hydrochloric acid-sodium chloride mixed solution and the hot water is 90-110°C.

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