Methods for preparing adsorbents and methods for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc.

Abstract

This invention belongs to the technical field of metal ion adsorption materials, specifically a method for preparing an adsorbent and a method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc. This invention modifies the surface of manganese dioxide with a thiourea-based silane coupling agent, grafting a silane coupling agent containing a thiourea structure onto the surface of manganese dioxide. The adsorption of lead, copper, and cadmium ions in solution is achieved using the manganese dioxide matrix and the thiourea-based silane coupling agent on the matrix surface, while effectively preventing the adsorbent from adsorbing zinc ions from the solution. When the adsorbent prepared by this invention is used to determine the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc, it exhibits a small testing error and can effectively improve the accuracy of soluble zinc content determination.

Description

Technical Field

[0001] This invention belongs to the technical field of metal ion adsorption materials, specifically the preparation method of the adsorbent and the method for determining the soluble zinc content of the 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, along with small amounts of zinc chloride, zinc sulfate, and trace amounts of 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 trace amounts of zinc ferrite and zinc silicate remain unleached; the remaining zinc is leached out.

[0003] The raw materials used in the ammonia chlorination process for producing electrolytic zinc are mainly galvanizing ash, zinc ash (a byproduct of acid smelting, which primarily consists of zinc oxide, zinc chloride, and elemental zinc, with low levels of impurities such as lead, cadmium, iron, and copper), and a small amount of low-lead steel mill ash. During the ammonia chlorination process, metallic elements such as lead, cadmium, and copper are leached out, but elemental zinc is not. Therefore, the ammonia chlorination process for producing electrolytic zinc and the acid smelting process are two completely different production systems. When determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc, 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 concentrations of elemental zinc. This fails to accurately reflect the soluble zinc content of the raw materials. Chinese patent document CN116338082A discloses a method for determining soluble zinc in the ammonia chloride process that effectively solves this problem. However, this method requires a low lead content in the raw materials; otherwise, lead will also introduce significant errors in the measurement results (because lead is leached out simultaneously during zinc leaching, and the generated lead sulfate is mostly dissolved in the high-concentration ammonium chloride solution). With the increasing number of ammonia chloride zinc smelting production lines, the supply of low-lead raw materials is becoming increasingly tight and the price is rising, severely restricting the production and development of ammonia chloride electrolytic zinc. For the survival and development of enterprises, it is necessary to develop new raw material markets. Currently, there are many zinc oxides and steel mill ash with lead content between 1% and 5% available on the market, and their prices are relatively low. The lead content is relatively low (because acid zinc smelting generally requires the raw materials to contain more than 5% lead, so that the lead mud by-product can be sold at a higher price, while ammonia zinc smelting requires the lead content to be less than 1%, otherwise the cost of purification and lead removal is too high). In order to survive, our company has developed a new lead removal technology, namely, adding an electrolytic lead removal process in the purification workshop. This solves the problem of high purification and lead removal costs, and the electrolytic lead generated in the electrolytic lead removal process is of high grade, generating higher by-product value. However, this high-lead raw material has a significant impact on our original determination of soluble zinc using the chloramine method, resulting in higher test results. In order to solve the problem of higher test results, we added 2-3g of ammonium carbonate before filtration and impurity removal through a large number of experiments. This greatly reduced the influence of lead on the test results (because lead carbonate has low solubility in high-concentration ammonium chloride solution). In order to further eliminate the influence of impurities such as lead, cadmium, and copper on the test results, we also used a new type of adsorption material to selectively adsorb and remove metal ions.

[0004] Chinese patent document CN116338082A discloses a method for determining soluble zinc using the ammonia chloride method. This method involves leaching the raw materials used in the ammonia chloride method for producing electrolytic zinc using an ammonia-based leaching solution. Ammonia water is then added for neutralization, causing impurities such as iron, manganese, aluminum, and trace amounts of lead 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 masking aluminum ions. Simultaneously, ascorbic acid and thiourea have weak complexing effects on lead and cadmium ions, resulting in poor masking effects. This leads to a certain deviation between the measured results and the true values. Furthermore, a high lead content in the raw materials can significantly affect the measured results. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing an adsorbent and a method for determining the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc, which solves 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 preparing an adsorbent includes the following steps:

[0008] (1) Manganese sulfate hydrate and potassium permanganate are mixed and reacted in water to obtain manganese dioxide particles;

[0009] (2) Manganese dioxide particles and thiourea-based silane coupling agent are heated in a solvent to obtain an adsorbent; the mass ratio of manganese dioxide particles to thiourea-based silane coupling agent is 1:1~1.2, and the chemical structure of the thiourea-based silane coupling agent is as follows:

[0010] .

[0011] Preferably, the mass ratio of manganese sulfate hydrate to potassium permanganate is 15.24:9.48.

[0012] Preferably, the reaction of manganese sulfate hydrate and potassium permanganate in water is carried out at room temperature for 3-4 hours.

[0013] Preferably, after manganese sulfate hydrate and potassium permanganate are mixed and reacted in water, they are allowed to stand for 24-25 hours, and then the solid and liquid are separated. The solid obtained from the solid-liquid separation is washed and dried to obtain manganese dioxide particles.

[0014] Preferably, the temperature for heating the manganese dioxide particles and the thiourea-based silane coupling agent in the solvent is 100-110°C, and the time is 15-20 h.

[0015] Preferably, after the manganese dioxide particles and the thiourea-based silane coupling agent are heated and reacted in a solvent, solid-liquid separation is performed. The solid obtained from the solid-liquid separation is soaked in ethanol for 12 hours and then subjected to solid-liquid separation again. The solid obtained from the second solid-liquid separation is dried to obtain the adsorbent. The mass ratio of the solid obtained from the solid-liquid separation to ethanol is 1:20~25.

[0016] A method for determining the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process includes the following steps: dissolving and leaching the raw materials used in the production of electrolytic zinc by the chloramine process with an ammoniacal leaching solution to obtain a dissolved leaching solution; then using a chemical precipitation method to precipitate and remove metal impurities in the dissolved leaching solution to obtain a test solution; then acidifying the test solution to obtain an acidified solution; then using the adsorbent described above to adsorb and remove metal ions in the acidified solution to obtain a titrant; and finally determining the soluble zinc content using a complexometric titration method.

[0017] Preferably, the ammoniacal leachate is prepared by mixing ammonium chloride and ammonia water with a concentration of 26-28%, wherein the concentration of ammonium chloride in the ammoniacal leachate is 5-6 mol / L; the concentration of ammonia water is 0.2-0.3 mol / L; the volume of ammoniacal leachate corresponding to each 0.2500 g of raw material used in the production of electrolytic zinc by the ammonia-chloride method is 50-55 mL; and the temperature for dissolving and leaching with the ammoniacal leachate is 70-75℃.

[0018] Preferably, the method for precipitating and removing metallic impurities from the dissolved leachate using chemical precipitation is as follows: Ferric chloride solution, ammonium carbonate, and ammonium chloride are added to the dissolved leachate, stirred and mixed, and then 26-28% ammonia solution is added dropwise. The mixture is stirred and neutralized until precipitation occurs, then excess 26-28% ammonia solution is added, followed by ammonium persulfate. After stirring evenly, the mixture is heated to boiling, and filtered while hot after 5 minutes. The filtrate is collected to obtain the test solution. The ferric chloride solution has a mass fraction of 8-9%, the volume of ferric chloride solution corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 1-1.5mL, the mass of ammonium chloride corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 5-6g, the mass of ammonium carbonate corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 2-3g, and the mass of ammonium persulfate corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 0.2-0.3g.

[0019] Preferably, the pH of the acidified solution is 2-3; the amount of adsorbent added is 3.5-4g per liter of acidified solution.

[0020] The beneficial effects of the adsorbent preparation method and 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: The present invention modifies the surface of manganese dioxide with a thiourea-based silane coupling agent, grafting a silane coupling agent containing a thiourea structure onto the surface of manganese dioxide. The adsorption of lead, copper, and cadmium ions in the solution is achieved using the manganese dioxide matrix and the thiourea-based silane coupling agent on the matrix surface, while effectively preventing the adsorbent from adsorbing zinc ions from the solution. When the adsorbent prepared by the present invention is used to determine the soluble zinc content of raw materials used in the ammonia chloride process for producing electrolytic zinc, it exhibits a small testing error and can effectively improve the accuracy of soluble zinc content determination. Attached Figure Description

[0021] Figure 1 The 1H NMR spectrum of the thiourea-based silane coupling agent prepared in Example 1 of this invention;

[0022] Figure 2 This is an ICP spectrum of Cd metal in the test solution in an application example of the present invention;

[0023] Figure 3 This is an ICP spectrum of the Cu element in the test solution in an application example of the present invention;

[0024] Figure 4 This is an ICP spectrum of Pb element in the test solution in an application example of the present invention;

[0025] Figure 5 This is an appearance diagram of the mixture with pH=5.5 obtained in an application example of the present invention;

[0026] Figure 6 This is a diagram showing the appearance of the solution at the titration endpoint when using EDTA solution in an application example of the present invention. Detailed Implementation

[0027] 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.

[0028] Specific embodiments of the preparation method of the adsorbent of the present invention are as follows:

[0029] Example 1

[0030] The method for preparing the adsorbent in this embodiment includes the following steps:

[0031] (1) Add 15.24g of manganese sulfate hydrate (manganese sulfate monohydrate, MnSO4·H2O) to 300mL of deionized water and stir until the manganese sulfate hydrate is fully dissolved to obtain a manganese sulfate hydrate solution; add 9.48g of potassium permanganate to 300mL of deionized water and stir until the potassium permanganate is fully dissolved to obtain a potassium permanganate solution; pour the manganese sulfate hydrate solution and the potassium permanganate solution into a flask equipped with a stirrer at the same time, and start stirring at the same time to make the manganese sulfate hydrate solution and potassium permanganate solution mix quickly. After pouring, continue stirring for 3h, then stop stirring, let stand for 24h, filter, wash the filter cake with deionized water, place the washed filter cake in a 50℃ oven and dry for 12h to obtain manganese dioxide particles.

[0032] (2) Add 0.01 mol of benzoyl isothiocyanate and 35 mL of acetonitrile to a flask, stir evenly, and cool to 0°C. Then add 0.015 mol of 3-aminopropyltriethoxysilane dropwise to the flask. After the addition is complete, stir the reaction at room temperature for 2 h. Rotate the reaction solution at 45°C to obtain the crude product. Stir the crude product and acetone at a mass ratio of 1:0.5 at 50°C for 15 min, then cool to 0°C. After standing for 2 h, a solid precipitate is formed. Filter at 0°C and wash the filter cake twice with acetone pre-cooled to 0°C, 5 mL each time. Place the washed filter cake in a vacuum drying oven at 50°C and dry for 12 h to obtain the thiourea-silane coupling agent. The 1H NMR spectrum of the thiourea-silane coupling agent (DMSO as solvent, TMS as internal standard) is shown below. Figure 1 As shown, the chemical structure is as follows:

[0033] .

[0034] (3) Add 5g of manganese dioxide particles and 200mL of toluene to a flask, then introduce nitrogen gas into the flask and heat it to 100℃. Then add a mixed solution containing 5g of thiourea-silane coupling agent and 30mL of toluene dropwise to the flask (dropping rate is 5mL / min). After the dropwise addition is completed, continue stirring the reaction for 15h. After cooling to room temperature, filter (the pore size of the filter paper is 3μm). Then immerse the solid obtained by vacuum filtration in anhydrous ethanol (the mass ratio of solid to anhydrous ethanol is 1:20). After soaking for 12h, filter (the pore size of the filter paper is 3μm). Place the solid obtained by vacuum filtration in a 60℃ oven and dry for 12h to obtain the adsorbent. The obtained adsorbent was tested using a thermogravimetric analyzer (N2 atmosphere, temperature increased to 800℃ at 10℃ / min). The results showed that the mass loss rate of the adsorbent in the characteristic decomposition range of the organic phase from 150℃ to 500℃ was 12.8%. Calculations showed that the actual grafting amount of the thiourea-based silane coupling agent on the surface of manganese dioxide particles was 0.734 g, with a grafting rate of 14.68%, confirming that the thiourea-based silane coupling agent had been successfully chemically grafted onto the surface of manganese dioxide particles.

[0035] Comparative Example 1

[0036] The adsorbent used in this comparative example is the manganese dioxide particles prepared in step (1) of the adsorbent preparation method of Example 1.

[0037] Comparative Example 2

[0038] The only difference between the preparation method of the adsorbent in this comparative example and the preparation method of the adsorbent in Example 1 is that the thiourea-silane coupling agent in step (3) of the preparation method of the adsorbent in this comparative example is replaced with 3-aminopropyltriethoxysilane.

[0039] Comparative Example 3

[0040] The steps (3) of the preparation method of the adsorbent in this comparative example are as follows: 5g of manganese dioxide particles and 200mL of toluene are added to a flask, nitrogen gas is then introduced into the flask, and a mixed solution containing 5g of thiourea-silane coupling agent and 30mL of toluene is added dropwise to the flask (dropping rate is 5mL / min). After the addition is completed, the mixture is stirred at room temperature for 15h, then filtered (the pore size of the filter paper is 3μm). The solid obtained by filtration is then immersed in anhydrous ethanol (the mass ratio of solid to anhydrous ethanol is 1:20). After soaking for 12h, it is filtered (the pore size of the filter paper is 3μm). The solid obtained by filtration is placed in a 60℃ oven and dried for 12h to obtain the adsorbent. The obtained adsorbent was tested using a thermogravimetric analyzer (N2 atmosphere, temperature increased to 800℃ at 10℃ / min). The results showed that the mass loss rate of the adsorbent in the characteristic decomposition range of the organic phase from 150℃ to 500℃ was 0.4%. Calculations showed that the actual grafting amount of the thiourea-based silane coupling agent on the surface of manganese dioxide particles was 0.02g, with a grafting rate of 0.4%. This confirms that at room temperature, the thiourea-based silane coupling agent may not have been grafted onto the surface of manganese dioxide through a chemical reaction, but rather adsorbed onto the surface of manganese dioxide through physical adsorption.

[0041] Experimental Example

[0042] To evaluate the removal efficiency of the adsorbents prepared in Example 1 and Comparative Examples 1-3 for metal ions in solution, 35 mg of adsorbent was added to 10 mL of a metal ion solution containing lead, copper, cadmium, and zinc ions (pH 2, concentrations of lead, copper, cadmium, and zinc ions were 7 mg / L, 12 mg / L, 2.5 mg / L, and 3400 mg / L, respectively). The solution was allowed to stand at 30 °C for 60 min, then filtered through 3 μm filter paper. The filtrate was collected, and the concentrations of lead, copper, cadmium, and zinc ions in the filtrate were determined using inductively coupled plasma atomic emission spectrometry (ICP). The results are shown in Table 1.

[0043] Table 1. Removal effect of adsorbent on metal ions in solution

[0044]

[0045] As shown in Table 1, the adsorbent prepared by this invention can reduce the concentration of lead, copper, and cadmium ions in the solution to below 0.03 mg / L, and has no significant effect on the concentration of zinc ions. This indicates that the adsorbent prepared by this invention has good selective adsorption of lead, copper, and cadmium ions in zinc ion solutions and can be applied to the removal of metal ions from zinc ion solutions.

[0046] In Comparative Example 1, unmodified manganese dioxide was used as the adsorbent. Its surface only has hydroxyl groups. After the hydroxyl groups are protonated in an acidic environment, they adsorb lead ions, copper ions, cadmium ions and zinc ions in the solution through electrostatic interaction. The adsorption effect is generally poor.

[0047] In Comparative Example 2, when amino-modified manganese dioxide was used, the amino groups on its surface easily combined with hydrogen ions under pH 2 conditions. A large number of hydrogen ions occupied the adsorption sites of the adsorbent, which prevented the amino groups from binding well with lead ions, copper ions, and cadmium ions, thus affecting the adsorption and removal effect of metal ions.

[0048] In Comparative Example 3, the adsorbent was prepared by mixing manganese dioxide and thiourea-based silane coupling agent at room temperature. Due to the low temperature, the thiourea-based silane coupling agent could not be grafted onto the surface of manganese dioxide through a chemical reaction. As a result, the adsorbent prepared in Comparative Example 3 was actually similar to the adsorbent in Comparative Example 1. The adsorption experiment results can well prove this conclusion.

[0049] The above conclusions indicate that the hydroxyl groups on the surface of unmodified manganese dioxide are protonated at pH=2, resulting in electrostatic adsorption of zinc ions, while the thiourea groups in the modified manganese dioxide exhibit Pb adsorption. 2+ Cu 2+ Cd 2+ It has a specific chelating effect, and is effective against Zn. 2+ It has no chelating ability; at the same time, the thiourea group covers the hydroxyl sites on the surface of manganese dioxide, significantly reducing Zn. 2+ The electrostatic adsorption capacity enables selective removal of heavy metal impurities from zinc ion solutions.

[0050] Application examples

[0051] Based on the above experimental results, it can be seen that the adsorbent prepared in this invention has good selective adsorption capacity for lead ions, copper ions, and cadmium ions in zinc ion solution. Therefore, in this application example, the adsorbent is used to determine the soluble zinc content of raw materials used in the production of electrolytic zinc by the chloramine process. The specific experimental method is as follows:

[0052] Place 0.2500g of the test sample into a 250mL beaker, add 50mL of ammonia leaching solution (the ammonia leaching solution is prepared by mixing ammonium chloride, 26% ammonia water with NH3 mass fraction, and deionized water; the concentration of ammonium chloride in the ammonia leaching solution is 5mol / L, and the concentration of NH3 is 0.2mol / L). Then place the beaker in a water bath and heat to 70℃, shaking every 5 minutes to accelerate the dissolution of the sample. After 30 minutes, remove the beaker, and then add 1mL of 8% ferric chloride solution, 5.5g of ammonium chloride, and 2.5g of ammonium carbonate to the beaker in sequence. Shake well, and then add 26% ammonia water with NH3 mass fraction dropwise to the beaker. Neutralize until a precipitate appears, and then add 15mL of 26% ammonia water with NH3 mass fraction. (The pH of the solution at this point is 8.5). Then, add 0.2 g of ammonium persulfate to the beaker, heat to boiling, and filter while hot after 5 minutes. Collect the filtrate. Wash the beaker twice with an ammonia-based washing solution at 85°C (the washing solution is 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 washing solution is 1%, and the mass fraction of NH3 is 0.5%) (the washing agent after each washing is filtered to remove solids). Wash the solid obtained from filtration six times. Combine the collected filtrate, the filtrate obtained from filtering the washing agent after washing the beaker, and the washing agent after washing the solid obtained from filtration while hot to form the test solution (the volume of the test solution is 150 mL; the ICP spectrum of the metal element in the test solution is shown in the figure). Figure 2 , Figure 3 and Figure 4 As shown, the contents of zinc and various metallic impurities in the test solution are Zn: 1082.3351 mg / L, Pb: 20.4858 mg / L, Cd: 3.0337 mg / L, and Cu: 23.9653 mg / L, respectively. The test solution was heated to 98°C until no ammonia odor remained, then cooled. Dilute hydrochloric acid was added to the beaker, and the mixture was shaken to obtain an acidified solution with pH=2. The adsorbent prepared in Example 1 (3.5 g / L) was then added to the acidified solution, and the mixture was shaken and mixed for 5 minutes, then sealed and allowed to stand for 60 minutes. Filter again, wash the beaker twice with deionized water, and wash the filtered solid five times. Collect the filtrate, the washing liquid from washing the beaker, and the washing liquid from washing the filtered solid. Combine the three liquids to obtain the titrant (volume 120 ml). Add 2 drops of 0.5% xylenol orange indicator to the titrant, then add 20% hexamethylenetetramine solution until the solution turns red. Add another 8 mL of 20% hexamethylenetetramine solution to obtain a mixture with pH 5.5 (e.g., ...). Figure 5 (As shown), finally titrate with 0.05 mol / L EDTA solution until the solution turns bright yellow (as shown). Figure 6(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:

[0053] Zn (ammonia) = (T × V / M) × 100%

[0054] 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.

[0055] After the determination, the relative error between the measured and actual values ​​(determined by ICP detection) of the soluble zinc content in the raw material sample was calculated. The relative standard deviation (RSD) of the three parallel determinations was 0.52%, and the spiked recovery rate was 99.6%. This experimental result proves that the adsorbent prepared in this invention can effectively remove Pb from the leaching solution of the raw material for electrolytic zinc production using the chloramine process. 2+ Cu 2+ Cd 2+ This method removes impurities and eliminates their interference with the determination of soluble zinc content by EDTA titration. It is suitable for pretreatment of soluble zinc content in electrolytic zinc raw materials to accurately determine the content, thereby reducing testing errors.

[0056] 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 preparing an adsorbent, characterized in that, Includes the following steps: (1) Manganese sulfate hydrate and potassium permanganate are mixed and reacted in water to obtain manganese dioxide particles; (2) Manganese dioxide particles and thiourea-based silane coupling agent are heated in a solvent to obtain an adsorbent; the mass ratio of manganese dioxide particles to thiourea-based silane coupling agent is 1:1~1.2, and the chemical structure of the thiourea-based silane coupling agent is as follows: 。 2. The method for preparing the adsorbent according to claim 1, characterized in that, The mass ratio of manganese sulfate hydrate to potassium permanganate is 15.24:9.

48.

3. The method for preparing the adsorbent according to claim 1, characterized in that, The reaction of manganese sulfate hydrate and potassium permanganate in water is carried out at room temperature for 3-4 hours.

4. The method for preparing the adsorbent according to claim 1, characterized in that, After manganese sulfate hydrate and potassium permanganate are mixed and reacted in water, they are allowed to stand for 24-25 hours, and then the solid and liquid are separated. The solid obtained from the solid-liquid separation is washed and dried to obtain manganese dioxide particles.

5. The method for preparing the adsorbent according to claim 1, characterized in that, The reaction of manganese dioxide particles and thiourea-based silane coupling agent in a solvent is carried out at a temperature of 100-110℃ for 15-20 hours.

6. The method for preparing the adsorbent according to claim 1, characterized in that, After manganese dioxide particles and thiourea-based silane coupling agent are heated and reacted in a solvent, solid-liquid separation is performed. The solid obtained from the solid-liquid separation is soaked in ethanol for 12 hours and then separated again. The solid obtained from the second solid-liquid separation is dried to obtain the adsorbent. The mass ratio of the solid obtained from the solid-liquid separation to ethanol is 1:20~25.

7. 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 production of electrolytic zinc by the chloramine process are dissolved and leached with an ammoniacal leachate to obtain a dissolved leachate. Then, the metal impurities in the dissolved leachate are precipitated and removed using a chemical precipitation method to obtain a test solution. The test solution is then acidified to obtain an acidified solution. The metal ions in the acidified solution are then adsorbed and removed using the adsorbent described above to obtain a titrant. Finally, the soluble zinc content is determined using a complexometric titration method.

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 7, characterized in that, The ammonia-based leachate is prepared by mixing ammonium chloride and ammonia water with a concentration of 26-28%. The concentration of ammonium chloride in the ammonia-based leachate is 5-6 mol / L, and the concentration of ammonia water is 0.2-0.3 mol / L. The volume of ammonia-based leachate corresponding to each 0.2500 g of raw material used in the production of electrolytic zinc by the ammonia-chloride method is 50-55 mL. The temperature for dissolving and leaching with the ammonia-based leachate is 70-75℃.

9. 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 7, characterized in that, The method for precipitating and removing metallic impurities from the leaching solution using chemical precipitation is as follows: Ferric chloride solution, ammonium carbonate, and ammonium chloride are added to the leaching solution and stirred until homogeneous. Then, ammonia solution with a concentration of 26-28% is added dropwise. The mixture is stirred until a precipitate forms, then excess ammonia solution with a concentration of 26-28% is added, followed by ammonium persulfate. After stirring until homogeneous, the mixture is heated to boiling and filtered while hot for 5 minutes. The filtrate is collected to obtain the test solution. The ferric chloride solution has a mass fraction of 8-9%. The volume of ferric chloride solution corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 1-1.5mL. The mass of ammonium chloride corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 5-6g. The mass of ammonium carbonate corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 2-3g. The mass of ammonium persulfate corresponding to each 0.2500g of raw material used in the production of electrolytic zinc using the chlorine-ammonia method is 0.2-0.3g.

10. 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 7, characterized in that, The pH of the acidified solution is 2-3; the amount of adsorbent added is 3.5-4g per liter of acidified solution.

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