Method for measuring content of soluble zinc in raw material for producing electrolytic zinc by ammonia chloride method

Abstract

The invention belongs to the technical field of soluble zinc determination, and particularly relates to a method for determining the content of soluble zinc in a raw material for producing electrolytic zinc by a chlorine-ammonia method. The method comprises the following steps: firstly, carrying out ammoniacal leaching on raw materials for producing electrolytic zinc by using a chloramine method, then carrying out primary precipitation and impurity removal on metal impurity elements in a dissolved leaching solution by using a chemical precipitation method, and further eliminating the influence of unremoved metal impurity ions such as lead ions, cadmium ions, iron ions, copper ions and aluminum ions by using a masking agent. The accuracy of the determination result is improved, the soluble zinc content of the raw material is truly reflected, and the industrial production is better guided.

Description

Technical Field

[0001] This invention belongs to the field of soluble zinc determination technology, specifically a method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process. Background Technology

[0002] Currently, electrolytic zinc production generally employs the acid process. The raw materials used in this process are zinc oxide produced from zinc concentrate through desulfurization or zinc oxide (high in lead) produced in a rotary kiln. The main zinc component in zinc oxide or zinc oxide is zinc oxide itself, while it also contains small amounts of zinc sulfide, zinc chloride, zinc sulfate, zinc ferrite, and zinc silicate. Therefore, dilute sulfuric acid is typically used to leach the raw materials (e.g., zinc oxide) used in the acid process to determine the soluble zinc content. During the acid leaching process, only small amounts of zinc sulfide, zinc ferrite, and zinc silicate remain unleached; the remaining zinc is leached out.

[0003] The raw materials used in the ammonia chloride process for producing electrolytic zinc are mainly galvanizing ash, zinc ash (a byproduct of acid leaching, which consists primarily of zinc oxide, zinc chloride, and elemental zinc, with extremely low levels of impurities such as lead, cadmium, iron, and copper), and a small amount of low-lead steel mill ash (requiring lead <0.3%, cadmium <0.1%, and copper <0.1%). If the impurity content is too high, the purification process consumes too much zinc powder, increasing production costs. During the ammonia chloride process, lead, cadmium, and copper are leached from the raw materials, but elemental zinc is not. Therefore, the ammonia chloride process for producing electrolytic zinc and the acid leaching process are two completely different production systems. When using the acid leaching method to determine the soluble zinc content of the raw materials used in the ammonia chloride process, the measured soluble zinc content is often much higher than the actual soluble zinc content leached out by the ammonia chloride process due to the leaching of higher levels of elemental zinc, thus failing to accurately reflect the soluble zinc content of the raw materials.

[0004] Chinese patent document CN116338082A discloses a method for determining soluble zinc using the ammonium chloride method. This method involves leaching the raw materials used in the ammonium chloride method for producing electrolytic zinc using an ammoniacal leaching solution. Ammonia water is then added for neutralization, causing impurities such as iron, manganese, aluminum, and lead in the leaching solution to separate as solid precipitates. Ammonium fluoride, ascorbic acid, and thiourea are then added to mask residual impurities. Finally, xylenol orange is used as an indicator, and EDTA is used for titration. The soluble zinc content is determined and calculated based on the color change. The experimental analysis results of this method are generally consistent with production results. However, when using ammonium fluoride to mask aluminum ions, the solution is acidic. Under acidic conditions, the reaction rate between ammonium fluoride and aluminum ions is slow, which is not conducive to the masking of aluminum ions. Simultaneously, ascorbic acid and thiourea have very weak complexing effects on lead and cadmium ions, resulting in poor masking effects and a certain deviation between the measured results and the true values. Summary of the Invention

[0005] To address the above problems, this invention provides a method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc, thereby solving the problem of large errors in the test results when determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc via the ammonia chloride process includes the following steps: dissolving and leaching the raw materials using an ammonia leaching solution to obtain a dissolved leachate; then precipitating and removing metallic impurities from the dissolved leachate using a chemical precipitation method to obtain a test solution; next, acidifying the test solution to obtain an acidified solution; then adding a masking agent to the acidified solution to mask the metallic impurity ions in the acidified solution to obtain a titrant; finally, determining the soluble zinc content using a complexometric titration method; the chemical structure of the masking agent is as follows:

[0008] .

[0009] Preferably, the ammonia-based leachate is prepared by mixing ammonium chloride, ammonia water with a mass fraction of 25-28% NH3, and water. The concentration of ammonium chloride in the ammonia-based leachate is 5-6 mol / L, and the concentration of NH3 is 0.2-0.3 mol / L.

[0010] Preferably, the volume of the ammoniacal leachate corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 50~55mL.

[0011] Preferably, the temperature for dissolving and leaching with an ammonia-based leachate is 70~75℃.

[0012] Preferably, the method for precipitating and removing metallic impurities from the dissolution leachate using chemical precipitation is as follows: Ferric chloride solution and ammonium chloride are added to the dissolution leachate, mixed well, and then ammonia water with a mass fraction of 25-28% (NH3) is added dropwise. When the precipitate appears, excess ammonia water with a mass fraction of 25-28% (NH3) is added, followed by ammonium persulfate. The mixture is heated to boiling, and after 5-6 minutes, it is filtered while hot. The filtrate is collected to obtain the test solution.

[0013] Preferably, the ferric chloride solution has a mass fraction of 8-9%, the volume of ferric chloride solution corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 1-1.5mL, the mass of ammonium chloride corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 5-6g, and the mass of ammonium persulfate corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 0.2-0.3g.

[0014] Preferably, the pH of the acidification solution is 1 to 2.

[0015] Preferably, the masking agent is added in the form of a masking agent solution, and the volume of the masking agent solution corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 10~15mL, and the mass fraction of the masking agent solution is 8~10%.

[0016] Preferably, the method for determining the soluble zinc content using complexometric titration is as follows: Add xylenol orange indicator to the titrant, then add hexamethylenetetramine solution until the solution turns red. Add excess hexamethylenetetramine solution to obtain a mixture with pH = 5-6. Finally, titrate with EDTA solution until the solution turns bright yellow. Record the volume of EDTA solution consumed during titration and calculate the soluble zinc content using the following formula:

[0017] Zn (ammonia) = (T × V / M) × 100%

[0018] In the formula, Zn (ammoniacosinate) represents the soluble zinc content of the raw material used in the production of electrolytic zinc by the chloramine process, %; T represents the titer of EDTA solution on zinc, g / mL; V represents the volume of EDTA solution consumed during titration, mL; and M represents the mass of the raw material used in the production of electrolytic zinc by the chloramine process, g.

[0019] Preferably, the masking agent is prepared as follows: epicyanool, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and solvent are heated to 80-85°C and reacted for 6-8 hours. After cooling to 50-55°C, vinylthiourea is added, and the reaction is continued for 5-7 hours. After purification, the masking agent is obtained. The dithiol compound is 1,3-dimercaptoprop-2-ol, the molar ratio of epicyanool, dithiol compound and vinylthiourea is 1:1:1, and the mass of 1,5-diazabicyclo[4.3.0]non-5-ene is 0.5-0.7% of the sum of the masses of vinylthiourea and dithiol compound.

[0020] The beneficial effects of the method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc of the present invention are as follows:

[0021] (1) This invention first performs ammonia leaching on the raw materials used in the production of electrolytic zinc by the chloramine method, then uses chemical precipitation to preliminarily precipitate and remove metal impurities in the dissolved leaching solution, and further uses a masking agent to eliminate the influence of unremoved metal impurity ions such as lead ions, cadmium ions, iron ions, copper ions and aluminum ions, thereby improving the accuracy of the measurement results, truly reflecting the soluble zinc content of the raw materials, and better guiding industrial production.

[0022] (2) This invention synthesizes a compound with multiple hydroxyl groups, nitrile groups, thiourea groups, and thioether bonds. The multiple hydroxyl groups in the compound can provide lone pairs of electrons to form coordinate bonds with metal ions. The nitrile groups can participate in the formation of back-coordinate bonds with metal ions through π antibonding orbitals. The sulfur and nitrogen atoms in the thiourea groups can both act as coordinating atoms to form coordinate bonds with metal ions. The sulfur atom in the thioether bond can provide lone pairs of electrons to form coordinate bonds with metal ions. This invention uses this compound as a masking agent. This masking agent has a strong complexing ability for lead ions, cadmium ions, iron ions, copper ions, and aluminum ions in zinc oxide solution, forming stable complexes. This effectively masks the color reaction of lead ions, cadmium ions, iron ions, copper ions, and aluminum ions with xylenol orange indicator, eliminates the influence of multiple metal impurity elements on the determination results when determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine method, and improves the accuracy of the detection results. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the appearance of the mixture with pH=5.5 obtained in Example 1 of the present invention;

[0024] Figure 2 This is a schematic diagram showing the appearance of the solution after titration with 0.05 mol / L EDTA solution until the solution turns bright yellow, as described in Example 1 of this invention.

[0025] Figure 3 This is the 1H NMR spectrum of the masking agent prepared in Example 1 of this invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0027] Example 1

[0028] The method for determining the soluble zinc content of the raw material used in the production of electrolytic zinc by the chloramine-ammonia process in this embodiment includes the following steps: 0.2000g of the raw material sample to be tested is placed in a 250mL beaker, 50mL of ammoniacal leaching solution is added, and then the beaker is placed in a water bath and heated to 70°C. The beaker is shaken every 5 minutes to accelerate the dissolution of the raw material sample. After 30 minutes, the beaker is removed, and 1mL of 8% ferric chloride solution and 5.5g of ammonium chloride are added to the beaker in sequence. After shaking well, 26% ammonia water is added dropwise to the beaker. When a precipitate appears, 15mL of 26% ammonia water is added (at this time, the pH of the solution is 8.5). Then, 0.2g of ammonium persulfate is added to the beaker, and the mixture is heated to boiling. After 5 minutes, the mixture is filtered while hot, and the filtrate is collected. The beaker is washed twice with a cleaning agent at 85°C. After each beaker washing, the cleaning agent was filtered to remove solids. The filtered solids were washed six times. The collected filtrate, the filtrate obtained from filtering the cleaning agent after washing the beaker, and the cleaning agent used to wash the filtered solids were combined to form the test solution (volume 150 mL). The test solution was heated to 98°C until no ammonia odor remained, then cooled. 1 mL of dilute hydrochloric acid was added to the beaker, and the mixture was shaken to obtain an acidified solution with pH=1.5. 10 mL of 8% masking agent solution was then added to the acidified solution, and the mixture was shaken to obtain the titrant. 2 drops of 0.5% xylenol orange indicator were added to the titrant, followed by 20% hexamethylenetetramine solution until the solution turned red. Then, 8 mL of 20% hexamethylenetetramine solution was added to obtain a mixed solution with pH=5.5 (e.g., ...). Figure 1 (As shown), finally titrate with 0.05 mol / L EDTA solution until the solution turns bright yellow (as shown). Figure 2 (As shown), record the volume of EDTA solution consumed during titration, and calculate the soluble zinc content of the raw materials used in the ammonia chlorination process for producing electrolytic zinc using the following formula:

[0029] Zn (ammonia) = (T × V / M) × 100%

[0030] In the formula, Zn (ammoniacosinate) represents the soluble zinc content of the raw material used in the production of electrolytic zinc by the chlorammonia process, %; T represents the titer of EDTA solution on zinc, g / mL; V represents the volume of EDTA solution consumed during titration, mL; and M represents the mass of the raw material sample to be tested, g.

[0031] The ammonia-based leachate was prepared by mixing ammonium chloride, ammonia water with a mass fraction of 26% NH3, and deionized water. The concentration of ammonium chloride in the ammonia-based leachate was 5 mol / L, and the concentration of NH3 was 0.2 mol / L. The cleaning agent was prepared by mixing ammonium chloride, ammonia water with a mass fraction of 26% NH3, and deionized water. The mass fraction of ammonium chloride in the cleaning agent was 1%, and the mass fraction of NH3 was 0.5%. The masking agent solution consisted of a masking agent and deionized water. The masking agent was prepared as follows: epicyanohydrin, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene, and butyl acetate were added to a reaction vessel, stirred evenly, heated to 80°C, stirred for 6 hours, and then cooled to 50°C. Vinylthiourea was added to the reactor, and the reaction was continued with stirring for 5 hours. The mixture was then distilled under reduced pressure to remove 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate, yielding a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol, and acetonitrile in a volume ratio of 6:4:2:1 to obtain the masking agent. The dithiol compound was 1,3-dimercaptoprop-2-ol, and the molar ratio of epicyanool, the dithiol compound, and vinylthiourea was 1:1:1. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of vinylthiourea and the dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinylthiourea and the dithiol compound. The 1H NMR spectrum of the masking agent is shown below. Figure 3 As shown, the chemical structure is as follows:

[0032] .

[0033] The working principle of the method for determining the soluble zinc content of the raw materials used in the ammonia chlorination process for producing electrolytic zinc in this embodiment is as follows: After the raw material sample to be tested is heated in contact with the ammonia leaching solution, the soluble metal in the raw material sample dissolves, and the following chemical reaction occurs:

[0034] ZnO+2NH4Cl→Zn(NH3)2Cl2+H2O;

[0035] MeO + 2NH4Cl → Me(NH3)2Cl2 + H2O, where Me represents Pb, Cd, Cu, etc.

[0036] ZnO + 4NH3·H2O → [Zn(NH3)4] 2+ +2OH - +3H2O;

[0037] After the soluble metal dissolves, the addition of ferric chloride solution and ammonium chloride provides sufficient ferric and ammonium ions, which is beneficial for the subsequent formation of ferric hydroxide precipitate and zinc ammonium complex ions. The ferric hydroxide precipitate can effectively adsorb and encapsulate impurity elements, improving the impurity removal effect and thus improving the accuracy of the determination. After mixing, the solution is alkalized with ammonia water. Under the action of the oxidant ammonium persulfate, heating, and alkaline environment, the metal ions and OH- - A precipitation reaction occurs, and impurity elements such as iron, manganese, aluminum, and lead are separated in the form of solid precipitates. Zinc ions dissolved from the raw material sample, as well as small amounts of aluminum, lead, cadmium, copper, and iron ions, remain in the test solution. Subsequently, a masking agent is added to mask the metallic impurity ions such as aluminum, lead, cadmium, copper, and iron ions, thereby eliminating the interference of these metallic impurity ions on the zinc ion titration analysis results. Finally, using xylenol orange as an indicator and hexamethylenetetramine as a buffer solution, the soluble zinc content of the raw material used in the production of electrolytic zinc by the chloramine process is determined by titration with EDTA standard solution. Xylenol orange is a commonly used acid-base indicator. It is red when the pH is less than 6.3, intermediate in color when the pH is equal to 6.3, and yellow when the pH is greater than 6.3. When xylenol orange is added, it forms a complex with zinc ions in the solution, turning red. When titrating with EDTA standard solution, EDTA reacts with zinc ions to form a chelate, changing the color of the solution from red to yellow, thus determining the titration endpoint.

[0038] Example 2

[0039] The method for determining the soluble zinc content of the raw material used in the production of electrolytic zinc by the chloramine-ammonia process in this embodiment includes the following steps: 0.2000g of the raw material sample to be tested is placed in a 250mL beaker, and 50mL of ammoniacal leaching solution is added. The beaker is then placed in a water bath and heated to 70°C. The beaker is shaken every 5 minutes to accelerate the dissolution of the raw material sample. After 30 minutes, the beaker is removed, and 1mL of 8% ferric chloride solution and 5g of ammonium chloride are added sequentially to the beaker. After shaking well, 25% ammonia solution (NH3) is added dropwise to the beaker. When a precipitate appears, 15mL of 25% ammonia solution (at which point the pH of the solution is 8) is added. Then, 0.2g of ammonium persulfate is added to the beaker, and the mixture is heated to boiling. After 5 minutes, the mixture is filtered while hot, and the filtrate is collected. The beaker is washed twice with a cleaning agent at 80°C (the cleaning agent is filtered after each washing to remove solids). The filtered solid is washed five times. The filtrate collected by hot filtration, the filtrate obtained by filtration with the cleaning agent after washing the beaker, and the cleaning agent obtained by washing the solids obtained by filtration are combined to form the test solution (volume of the test solution is 150 mL). The test solution is heated to 95 °C until there is no ammonia odor, then cooled. Dilute hydrochloric acid is added to the beaker, and the mixture is shaken to obtain an acidified solution with pH=1. Then, 10 mL of 8% masking agent solution is added to the acidified solution, and the mixture is shaken to obtain a titrant. Two drops of 0.5% xylenol orange indicator are added to the titrant, and then 20% hexamethylenetetramine solution is added until the solution turns red. Then, excess 20% hexamethylenetetramine solution is added to obtain a mixed solution with pH=5. Finally, the solution is titrated with 0.05 mol / L EDTA solution until it turns bright yellow. The volume of EDTA solution consumed during titration is recorded. The soluble zinc content of the raw materials used in the production of electrolytic zinc by the chloramine method is calculated according to the following formula:

[0040] Zn (ammonia) = (T × V / M) × 100%

[0041] In the formula, Zn (ammoniacosinate) represents the soluble zinc content of the raw material used in the production of electrolytic zinc by the chlorammonia process, %; T represents the titer of EDTA solution on zinc, g / mL; V represents the volume of EDTA solution consumed during titration, mL; and M represents the mass of the raw material sample to be tested, g.

[0042] The ammonia-based leachate was prepared by mixing ammonium chloride, ammonia water with a mass fraction of 25% NH3, and deionized water. The concentration of ammonium chloride in the ammonia-based leachate was 5 mol / L, and the concentration of NH3 was 0.2 mol / L. The cleaning agent was prepared by mixing ammonium chloride, ammonia water with a mass fraction of 25% NH3, and deionized water. The mass fraction of ammonium chloride in the cleaning agent was 1%, and the mass fraction of NH3 was 0.5%. The masking agent solution consisted of a masking agent and deionized water. The chemical structure of the masking agent is as follows:

[0043] .

[0044] Example 3

[0045] The method for determining the soluble zinc content of the raw material used in the production of electrolytic zinc by the chloramine-ammonia process in this embodiment includes the following steps: 0.2000g of the raw material sample to be tested is placed in a 250mL beaker, and 50mL of ammoniacal leaching solution is added. The beaker is then placed in a water bath and heated to 70°C. The beaker is shaken every 5 minutes to accelerate the dissolution of the raw material sample. After 30 minutes, the beaker is removed, and 1mL of 8% ferric chloride solution and 6g of ammonium chloride are added sequentially to the beaker. After shaking well, 28% ammonia solution (NH3) is added dropwise to the beaker. When a precipitate appears, 15mL of 28% ammonia solution (at which point the pH of the solution is 9) is added. Then, 0.2g of ammonium persulfate is added to the beaker, and the mixture is heated to boiling. After 5 minutes, the mixture is filtered while hot, and the filtrate is collected. The beaker is washed three times with a cleaning agent at 90°C (the cleaning agent is filtered after each washing to remove solids). The filtered solid is washed six times. The filtrate collected by hot filtration, the filtrate obtained by filtration with the cleaning agent after washing the beaker, and the cleaning agent obtained by washing the solids obtained by filtration are combined to form the test solution (volume of the test solution is 150 mL). The test solution is heated to 100℃, and after cooling, dilute hydrochloric acid is added to the beaker and shaken to mix well to obtain an acidified solution with pH=2. Then, 10 mL of 8% masking agent solution is added to the acidified solution and shaken to mix for 2 min to obtain the titrant. Two drops of 0.5% xylenol orange indicator are added to the titrant, and then 20% hexamethylenetetramine solution is added until the solution turns red. Then, excess 20% hexamethylenetetramine solution is added to obtain a mixed solution with pH=6. Finally, it is titrated with 0.05 mol / L EDTA solution until the solution is bright yellow. The volume of EDTA solution consumed during titration is recorded. The soluble zinc content of the raw materials used in the production of electrolytic zinc by the chloramine method is calculated according to the following formula:

[0046] Zn (ammonia) = (T × V / M) × 100%

[0047] In the formula, Zn (ammoniacosinate) represents the soluble zinc content of the raw material used in the production of electrolytic zinc by the chlorammonia process, %; T represents the titer of EDTA solution on zinc, g / mL; V represents the volume of EDTA solution consumed during titration, mL; and M represents the mass of the raw material sample to be tested, g.

[0048] The ammonia-based leachate was prepared by mixing ammonium chloride, ammonia water with a NH3 mass fraction of 28%, and deionized water. The concentration of ammonium chloride in the ammonia-based leachate was 5 mol / L, and the concentration of NH3 was 0.2 mol / L. The cleaning agent was prepared by mixing ammonium chloride, ammonia water with a NH3 mass fraction of 28%, and deionized water. The mass fraction of ammonium chloride in the cleaning agent was 1%, and the mass fraction of NH3 was 0.5%. The masking agent solution consisted of a masking agent and deionized water. The chemical structure of the masking agent is as follows:

[0049] .

[0050] Comparative Example 1

[0051] The difference between the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example and the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 is that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is composed of ammonium fluoride, ascorbic acid and thiourea in a mass ratio of 1:0.5:6.

[0052] Comparative Example 2

[0053] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Epicyanohydrin, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 80°C, stirred for 6 hours, cooled to 50°C, allyl thiourea is added to the reaction vessel, stirred for another 5 hours, and then distilled under reduced pressure to remove 1 The crude product was obtained by reacting 5-diazabicyclo[4.3.0]non-5-ene and butyl acetate. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol, and acetonitrile in a volume ratio of 6:4:2:1 to obtain the masking agent. The dithiol compound was 1,3-dimercaptoprop-2-ol, and the molar ratio of epicyanool, the dithiol compound, and allyl thiourea was 1:1:1. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of allyl thiourea and the dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinyl thiourea and the dithiol compound. The chemical structure of the masking agent is as follows:

[0054] .

[0055] Comparative Example 3

[0056] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Epicyanohydrin, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 80°C, stirred for 6 hours, cooled to 50°C, vinyl thiourea is added to the reaction vessel, and stirred for another 5 hours. The mixture is then distilled under reduced pressure to remove... The crude product was obtained by removing 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol, and acetonitrile in a volume ratio of 6:4:2:1 to obtain the masking agent. The dithiol compound was 1,2-ethanedithiol, and the molar ratio of epicyanin, the dithiol compound, and vinylthiourea was 1:1:1. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of vinylthiourea and the dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinylthiourea and the dithiol compound. The chemical structure of the masking agent is as follows:

[0057] .

[0058] Comparative Example 4

[0059] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Epicyanohydrin, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 80°C, stirred for 6 hours, cooled to 50°C, vinyl thiourea is added to the reaction vessel, and stirred for another 5 hours. The mixture is then distilled under reduced pressure to remove... The crude product was obtained by removing 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol, and acetonitrile in a volume ratio of 6:4:2:1 to obtain the masking agent. The dithiol compound was 1,3-propanedithiol, and the molar ratio of epicyanool, the dithiol compound, and vinylthiourea was 1:1:1. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of vinylthiourea and the dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinylthiourea and the dithiol compound. The chemical structure of the masking agent is as follows:

[0060] .

[0061] Comparative Example 5

[0062] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Acrylonitrile, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 50°C, and stirred for 6 hours. Then, vinyl thiourea is added to the reaction vessel, and the stirring reaction continues for 5 hours. The mixture is then distilled under reduced pressure to remove 1,5-non-5-ene. -Diazabicyclo[4.3.0]non-5-ene and butyl acetate were used to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol and acetonitrile in a volume ratio of 6:4:2:1 to obtain a masking agent. The dithiol compound was 1,3-dimercaptoprop-2-ol, and the molar ratio of acrylonitrile, dithiol compound and vinylthiourea was 1:1:1. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of vinylthiourea and dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinylthiourea and dithiol compound. The chemical structure of the masking agent is as follows:

[0063] .

[0064] Comparative Example 6

[0065] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Epicyanohydrin, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 80°C, stirred and reacted for 11 hours, and then distilled under reduced pressure to remove 1,5-non-5-ene. -Diazabicyclo[4.3.0]non-5-ene and butyl acetate were used to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol and acetonitrile in a volume ratio of 6:4:2:1 to obtain a masking agent. The dithiol compound was 1,3-dimercaptoprop-2-ol, the molar ratio of epicyanool to dithiol compound was 2:1, the mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the mass of the dithiol compound, and the mass of butyl acetate was 6 times the mass of the dithiol compound. The chemical structure of the masking agent is as follows:

[0066] .

[0067] Comparative Example 7

[0068] The method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example differs from the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in Example 1 only in that the masking agent in the method for determining the soluble zinc content of the raw materials used in the ammonia chloride process for producing electrolytic zinc in this comparative example is prepared as follows: Vinylthiourea, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and butyl acetate are added to a reaction vessel, stirred evenly, heated to 50°C, stirred and reacted for 11 h, and then distilled under reduced pressure to remove 1,5-diazabicyclo[4.3.0]non-5-ene. [4.3.0]Non-5-ene and butyl acetate were reacted to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, dichloromethane, methanol, and acetonitrile in a volume ratio of 6:4:2:1 to obtain a masking agent. The dithiol compound was 1,3-dimercaptoprop-2-ol, and the molar ratio of the dithiol compound to vinylthiourea was 1:2. The mass of 1,5-diazabicyclo[4.3.0]non-5-ene was 0.5% of the sum of the masses of vinylthiourea and the dithiol compound, and the mass of butyl acetate was 6 times the sum of the masses of vinylthiourea and the dithiol compound. The chemical structure of the masking agent is as follows:

[0069] .

[0070] Experimental Example 1

[0071] To examine the accuracy of the determination methods in each embodiment and comparative example, working standard zinc oxide conforming to standard GB1260-2008 was dissolved in an ammoniacal leaching solution (the same ammoniacal leaching solution as in Example 1) to obtain a zinc oxide solution. Then, a certain amount of impurity ion solution (prepared by dissolving lead chloride, cadmium chloride, ferric chloride, copper chloride, and aluminum chloride in water) was added to obtain a test solution containing impurity ions. The volume of the test solution containing impurity ions was 70 mL, the concentration of zinc was 2.3 g / L, and the mass ratio of zinc, lead, cadmium, iron, copper, and aluminum in the test solution containing impurity ions was 80:1:1:4:4:4. Then, the solution containing impurity ions was... Dilute hydrochloric acid was added to the test solution of the ion, and the mixture was shaken thoroughly to obtain an acidified solution with pH=1.5. Then, the masking agent solution (10 mL in volume) from Example 1 or the comparative examples was added to the acidified solution, and the mixture was shaken and mixed for 1 min to obtain the titrant. Two drops of 0.5% xylenol orange indicator were added to the titrant, followed by 20% hexamethylenetetramine solution until the solution turned red. An excess of 20% hexamethylenetetramine solution was then added to obtain a mixture with pH=5.5. Finally, the solution was titrated with 0.05 mol / L EDTA solution until it turned bright yellow. The volume of EDTA solution consumed during titration was recorded, and three parallel experiments were performed. After the experiment, the average volume V1 of the EDTA solution consumed in the three parallel experiments was calculated. Simultaneously, a blank control experiment was conducted using deionized water instead of the impurity ion solution. The specific steps are as follows: Zinc oxide conforming to standard GB1260-2008 was dissolved in an ammoniacal leaching solution (the same ammoniacal leaching solution as in Example 1) to obtain a zinc oxide solution. Then, a certain amount of deionized water was added to obtain a blank test solution with a volume of 70 mL and a zinc concentration of 2.3 g / L. Then, dilute hydrochloric acid was added to the blank test solution, and after shaking evenly, an acidified solution with pH=1.5 was obtained. Finally, deionized water was added to the acidified solution (the volume of deionized water...). The solution was mixed with 10 mL of EDTA solution and shaken for 1 min to obtain a titrant. Two drops of 0.5% xylenol orange indicator were added to the titrant, followed by 20% hexamethylenetetramine solution until the solution turned red. An excess of 20% hexamethylenetetramine solution was then added to obtain a mixture with pH 5.5. Finally, the solution was titrated with 0.05 mol / L EDTA solution until it turned bright yellow. The volume of EDTA solution consumed during titration was recorded. Three parallel experiments were performed. After the experiments, the average volume V0 of the EDTA solution consumed in the three parallel experiments was calculated. Finally, the titration deviation was calculated as: Titration deviation = (V1 - V0) / V0 × 100%. The test results of the titration deviations for each example and comparative example are shown in Table 1.

[0072] Table 1. Test results of titration deviation for the determination methods of each embodiment and comparative example.

[0073]

[0074] As shown in Table 1, the masking agent used in this invention has a strong complexing ability for lead ions, cadmium ions, iron ions, copper ions and aluminum ions in zinc oxide solution, forming stable complexes. This effectively masks the color reaction of lead ions, cadmium ions, iron ions, copper ions and aluminum ions with xylenol orange indicator, thus improving the accuracy of the detection results.

[0075] As can be seen from Example 1 and Comparative Example 1, when a mixture of ammonium fluoride, ascorbic acid and thiourea is used as a masking agent, ammonium fluoride can mask aluminum ions, and ascorbic acid and thiourea can mask iron ions, copper ions and lead ions. However, ammonium fluoride is less effective at masking aluminum ions under acidic conditions, and the masking agent in Comparative Example 1 has a weak complexing effect on lead ions and cadmium ions, resulting in poor masking effect and large titration deviation.

[0076] As can be seen from Example 1 and Comparative Examples 2-6, the titration deviation increases when the chemical structure of the masking agent is adjusted. This indicates that the hydroxyl, thiourea, nitrile groups and carbon chain length in the masking agent all affect the complexation ability of lead, cadmium, iron, copper and aluminum ions in the zinc oxide solution, thereby affecting the masking effect.

[0077] Experiment Example 2

[0078] To further examine the practical application effect of the determination methods in Example 1 and the comparative examples, the same raw material samples used for the production of electrolytic zinc via the chloramine method (there were three types of raw material samples, named Sample 1, Sample 2, and Sample 3, respectively) were divided into several portions. The determination methods of Example 1 and Comparative Examples 1-7 were then used to determine the soluble zinc content. During the analysis, ICP emission spectroscopy was used to determine the content of zinc and other metallic impurities in the test solution. After the test, the relative error between the measured value and the actual zinc content in the test solution was calculated. The results are shown in Table 2. For each sample, each determination method was repeated three times, and the average of the three test results was taken as the final determination result. In Table 2, the contents of zinc and various metallic impurities in the test solution obtained when testing sample 1 were Zn: 1.25 g / L, Pb: 7.10 mg / L, Cd: 1.81 mg / L, Fe: 0.021 μg / L, Cu: 16.34 mg / L, and Al: 3.78 mg / L, respectively. The contents of zinc and various metallic impurities in the test solution obtained when testing sample 2 were Zn: 1.31 g / L, Pb: 6.52 μg / L, and Al: 0.021 μg / L, respectively. The concentrations of zinc and other metallic impurities in the test solution obtained when testing sample 3 were 1.21 g / L, 6.22 mg / L, 2.01 mg / L, 0.017 μg / L, 22.27 mg / L, and 3.82 mg / L, respectively.

[0079] Table 2. Relative errors when measuring the same zinc oxide samples using the methods of Example 1 and the comparative examples.

[0080]

[0081] As shown in Table 2, when the raw material samples used in the production of electrolytic zinc by the chloramine method were actually measured and analyzed using the determination methods of Example 1 and the comparative examples, the results obtained by Example 1 were closest to the zinc content in the test solution, with the smallest error. This indicates that the determination method of Example 1 has the highest accuracy. This conclusion further proves that the masking agent used in this invention can form stable complexes with metal impurity ions such as lead ions, cadmium ions, iron ions, copper ions and aluminum ions in the zinc oxide solution through complexation, effectively masking the color reaction of impurity metal ions with xylenol orange indicator, and improving the accuracy of the measurement results.

[0082] Example of effect

[0083] To further verify the effectiveness of the determination method of the present invention in practical applications, the soluble zinc content of the raw materials used in the production of electrolytic zinc by the chloramine method was determined according to the method in Example 1, and the determination results and actual production data are listed in Table 3. In Table 3, samples 1#, 2#, 3#, 4#, 5#, and 6# are raw material samples of zinc plating ash (iron tower ash), zinc plating ash (pipeline ash), electrolytic zinc ash (bag filter), electrolytic zinc ash (dust collection), steel plant ash, and blow plating ash, respectively. The soluble zinc by the ammonia method represents the percentage content of zinc soluble by the chloramine method in the raw material sample, i.e., Zn(ammonia soluble). The ammonia soluble rate is: Zn(ammonia soluble) / total mass of Zn element in the raw material sample × 100%. The actual production data refers to the actual dissolution rate of zinc during the production of electrolytic zinc by the chloramine method using the corresponding numbered raw material samples. The actual percentage of zinc dissolved in the raw material sample is calculated as follows: Actual dissolution rate = (Total amount of zinc ingots produced + Total amount of soluble zinc in the slag) ÷ Total amount of zinc in the raw material × 100%. Since some soluble zinc solution is adsorbed in the solid slag during the electrolytic zinc production process using the ammonia chloride method, the adsorbed soluble zinc is separated from the solid slag through pressure filtration and water leaching (using hot water at 80℃) to obtain a soluble zinc solution. The total amount of soluble zinc in the soluble zinc solution is then determined using ICP emission spectroscopy, which is the total amount of soluble zinc in the slag.

[0084] Table 3. Comparison of the measured values ​​of soluble zinc content in raw materials used in the production of electrolytic zinc via the ammonium chloride process and actual production data.

[0085]

[0086] As shown in Table 3, the method for determining the soluble zinc content of the present invention is in good agreement with actual production data and has high accuracy.

[0087] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc via the chloramine process, characterized in that, The process includes the following steps: The raw materials used in the electrolytic zinc production process via the chloramine-ammonia method are dissolved and leached with an ammoniacal leachate to obtain a dissolved leachate. Then, a chemical precipitation method is used to precipitate and remove metallic impurities from the dissolved leachate, yielding a test solution. This test solution is then acidified to obtain an acidified solution. A masking agent is added to the acidified solution to mask the metallic impurity ions, resulting in a titrant. Finally, a complexometric titration method is used to determine the soluble zinc content. The chemical structure of the masking agent is as follows: 。 2. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The ammonia-based leachate is prepared by mixing ammonium chloride, ammonia water with a mass fraction of 25-28% NH3, and water. The concentration of ammonium chloride in the ammonia-based leachate is 5-6 mol / L, and the concentration of NH3 is 0.2-0.3 mol / L.

3. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The volume of ammoniacal leachate corresponding to each 0.2000g of raw material used in the production of electrolytic zinc via the chloramine method is 50~55mL.

4. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The leaching temperature for dissolution using ammonia-based leachate is 70~75℃.

5. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The method for precipitating and removing metallic impurities from the dissolution leachate using chemical precipitation is as follows: Add ferric chloride solution and ammonium chloride to the dissolution leachate, mix well, and then add ammonia water with a mass fraction of 25-28% (NH3) dropwise. Neutralize until precipitation occurs, then add excess ammonia water with a mass fraction of 25-28% (NH3), followed by ammonium persulfate. Heat to boiling, and after 5-6 minutes, filter while hot. Collect the filtrate to obtain the test solution.

6. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 5, characterized in that, The ferric chloride solution has a mass fraction of 8-9%, the volume of ferric chloride solution corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 1-1.5mL, the mass of ammonium chloride corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 5-6g, and the mass of ammonium persulfate corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 0.2-0.3g.

7. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The pH of the acidified solution is 1 to 2.

8. The method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process according to claim 1, characterized in that, The masking agent is added in the form of a masking agent solution. The volume of the masking agent solution corresponding to each 0.2000g of raw material used in the production of electrolytic zinc by the chloramine method is 10~15mL, and the mass fraction of the masking agent solution is 8~10%.

9. The method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc according to any one of claims 1-8, characterized in that, The method for determining soluble zinc content using complexometric titration is as follows: Add xylenol orange indicator to the titrant, then add hexamethylenetetramine solution until the solution turns red. Add excess hexamethylenetetramine solution to obtain a mixture with pH 5-6. Finally, titrate with EDTA solution until the solution turns bright yellow. Record the volume of EDTA solution consumed during titration and calculate the soluble zinc content using the following formula: Zn (ammonia) = (T × V / M) × 100% In the formula, Zn(ammoniacos) represents the soluble zinc content of the raw materials used in the ammonia chlorination process for producing electrolytic zinc, %; T represents the titer of EDTA solution for zinc, g / mL; V represents the volume of EDTA solution consumed during titration, mL; M represents the mass of raw materials used in the production of electrolytic zinc via the chloramine process, g.

10. The method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc according to any one of claims 1-8, characterized in that, The masking agent is prepared as follows: epicyanool, dithiol compound, 1,5-diazabicyclo[4.3.0]non-5-ene and solvent are heated to 80~85℃ and reacted for 6~8h. After cooling to 50~55℃, vinylthiourea is added and the reaction is continued for 5~7h. After purification, the masking agent is obtained. The dithiol compound is 1,3-dimercaptoprop-2-ol, the molar ratio of epicyanool, dithiol compound and vinylthiourea is 1:1:1, and the mass of 1,5-diazabicyclo[4.3.0]non-5-ene is 0.5~0.7% of the sum of the masses of vinylthiourea and dithiol compound.

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