Method for determining ammonia nitrogen in tail liquid of comprehensive utilization of platinum-containing waste catalyst

Abstract

The present application relates to the field of environmental monitoring and chemical analysis technology, and discloses a kind of determination method of ammonia nitrogen in tail liquid of comprehensive utilization of platinum-containing waste catalyst, comprising the following steps: S1, sample dilution: accurately pipetting 1.00mL to-be-measured tail liquid, placing in 100mL volumetric flask, with ammonia-free pure water constant volume to the scale and fully mixed, to obtain A solution, to achieve 100 times controllable dilution.The present application effectively solves the core technical problems such as high acid inhibition of color development, aluminum ion precipitation embedding ammonia nitrogen, liquid alkali dilution, and exogenous nitrogen pollution through targeted pretreatment process and determination integration technology, fills the blank of special ammonia nitrogen determination method for such complex matrix samples, and meets the needs of laboratory routine monitoring and industrial application.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring and chemical analysis technology, specifically a method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst. Background Technology

[0002] In the resource utilization process of platinum-containing spent catalysts, a sulfuric acid system is often used for platinum leaching and separation, generating a large amount of complex tailings. These tailings are characterized by high acidity, high aluminum ion content, and low ammonia nitrogen. The free sulfuric acid content reaches 4%-5.5%, the aluminum ion content is 3%-6%, and the ammonia nitrogen concentration is mostly between 0.1-100 mg / L, making them typical complex matrix samples for ammonia nitrogen determination.

[0003] Currently, the determination of ammonia nitrogen in water bodies mainly relies on national standard methods, such as Nessler's reagent spectrophotometry (HJ535-2009) and salicylic acid spectrophotometry. These methods are primarily designed for routinely clean or lightly polluted water samples. However, when directly applied to tailings from the comprehensive utilization of platinum-containing waste catalysts, they suffer from numerous unresolved technical defects, resulting in large deviations, low accuracy, and poor repeatability in the measurement results. Specifically: Interference from strong acid environment: The high concentration of sulfuric acid in the tail liquid will directly inhibit the color reaction of Nessler's reagent, salicylic acid reagent and ammonia nitrogen, making the color reaction indistinct or even impossible. At the same time, strong acid will corrode and interfere with the response of detection instruments such as ion-selective electrodes, resulting in distorted instrument detection results. Liquid alkali neutralization leads to excessive dilution of ammonia nitrogen: Existing technologies often use liquid alkalis such as sodium hydroxide solution to neutralize acidity, but liquid alkalis require the introduction of a large amount of water, which leads to a significant dilution of ammonia nitrogen concentration in the tail liquid. For this type of low ammonia nitrogen tail liquid, the diluted ammonia nitrogen concentration is close to the method detection limit, which greatly reduces the detection sensitivity and may even make it impossible to accurately quantify. Aluminum ion precipitation causes ammonia nitrogen loss: High concentrations of aluminum ions in the tail liquid will rapidly form colloidal aluminum hydroxide precipitate during alkaline neutralization. This colloid has strong adsorption properties and easily adsorbs or encapsulates ammonia nitrogen in the solution. Conventional flocculation precipitation and masking agent methods cannot effectively remove this colloid. Existing masking agents such as potassium sodium tartrate can only mask calcium and magnesium ions and have no masking effect on aluminum ions. As a result, ammonia nitrogen cannot participate in the colorimetric reaction after being encapsulated by the precipitate, and the measured results are lower. Exogenous nitrogen contamination and filtration interference: Conventional filtration methods require pre-wetting of filter paper. Nitrogen impurities contained in ordinary filter paper will dissolve in the filtrate, causing exogenous nitrogen contamination. At the same time, large-pore filter paper cannot retain colloidal aluminum hydroxide precipitate, and the turbidity of the filtrate will interfere with the colorimetric detection by spectrophotometry. Lack of dedicated pretreatment methods: Existing national standard methods do not cover the treatment requirements of such high acid and high aluminum extreme matrix samples. There is no targeted pretreatment process, and direct application will produce significant systematic errors. The spiked recovery rate is far below the acceptable range of 90%, which cannot meet the requirements of quantitative detection.

[0004] Furthermore, existing improved methods for ammonia nitrogen determination in complex matrices are mostly focused on samples such as seawater and battery wastewater. These methods primarily eliminate interference from calcium and magnesium ions, sulfides, and organic matter through masking agent matching, flocculation and sedimentation, and distillation. However, these methods do not address the characteristics of high acidity and high aluminum content in the treated samples, and therefore cannot solve the core interference problem in platinum-containing waste catalyst tailings. Therefore, there is an urgent need to develop a dedicated ammonia nitrogen determination method for tailings from the comprehensive utilization of such high-acid, high-alumina platinum-containing waste catalysts, achieving accurate, stable, and reproducible quantification of ammonia nitrogen. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned shortcomings of existing technologies and provide a method for determining ammonia nitrogen in the tailings of platinum-containing waste catalysts that is simple to operate, has minimal interference, high recovery rate, and good accuracy. This method effectively solves core technical problems such as high acid inhibition of color development, aluminum ion precipitation and embedding of ammonia nitrogen, liquid alkali dilution, and exogenous nitrogen contamination through targeted pretreatment processes and integrated measurement technology. It fills the gap in the lack of a dedicated ammonia nitrogen determination method for this type of complex matrix sample, meeting the needs of routine laboratory monitoring and industrial applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for determining ammonia nitrogen in the tailings of platinum-containing waste catalyst comprehensive utilization. This method addresses the technical problems encountered when existing national standard ammonia nitrogen determination methods are directly applied to such complex high-acid, high-alumina matrices. These problems include strong acid inhibiting the colorimetric reaction, aluminum ions forming colloidal aluminum hydroxide precipitates that adsorb and encapsulate ammonia nitrogen, the introduction of large amounts of water during liquid alkali neutralization leading to ammonia nitrogen dilution and reduced detection sensitivity, and the introduction of exogenous nitrogen contamination through filter paper wetting. The method specifically includes the following steps: S1. Sample dilution: Accurately transfer 1.00 mL of the tail liquid to be tested into a 100 mL volumetric flask, dilute to the mark with ammonia-free pure water and mix thoroughly to obtain solution A. This achieves 100-fold controllable dilution, which reduces acidity and aluminum ion concentration, reduces the burden of subsequent neutralization, avoids the accumulation of errors caused by multiple dilution steps, and controls the total volume for easy routine laboratory operations. S2, pH adjustment: Take a portion of the diluted solution from solution A and transfer it to a clean beaker. Use solid sodium hydroxide instead of traditional liquid alkali for neutralization. Add the sodium hydroxide while stirring until the pH of the solution reaches 6.8-7.5. This avoids introducing additional water that would further dilute the ammonia nitrogen and also eliminates the interference of the high acid environment on the ammonia nitrogen colorimetric reaction and instrument detection. S3. Precipitation separation and filtration: For the turbid liquid that forms aluminum hydroxide colloidal precipitate after neutralization, dry filtration is performed using quantitative filter paper that has been treated with ammonia-free, i.e. the filter paper is not pre-wetted. The clear filtrate is collected for subsequent determination, which effectively removes aluminum precipitate and avoids external pollution caused by nitrogen-containing impurities in the filter paper. This solves the problem of low test results caused by the adsorption and encapsulation of ammonia nitrogen by aluminum hydroxide colloid. S4. Ammonia Nitrogen Determination and Result Calculation: Take the above clarified filtrate and test it according to the standard method for ammonia nitrogen determination. Multiply the ammonia nitrogen concentration of the filtrate obtained by measurement by 100 times the total dilution factor to calculate the ammonia nitrogen concentration in the original tailings. The calculation formula is: C0=C1×100, where C0 is the ammonia nitrogen concentration in the original tailings (mg / L) and C1 is the ammonia nitrogen concentration obtained by measurement of the filtrate (mg / L).

[0007] Furthermore, the solid sodium hydroxide in step S2 is analytical grade granular or flake sodium hydroxide, avoiding the use of powdered sodium hydroxide; This invention addresses the technical problems in existing technologies, such as the easy splashing of powdered alkali agents, localized instantaneous over-alkaliness upon contact with solution, leading to the rapid formation of aluminum hydroxide precipitate by aluminum ions and severe encapsulation of ammonia nitrogen, as well as the loss of ammonia nitrogen and operational safety issues caused by solution splashing. Granular or flake sodium hydroxide reacts mildly with the diluent, allowing for slow and controllable pH adjustment, while reducing safety hazards during operation.

[0008] Furthermore, in step S2, the solid sodium hydroxide is added in small amounts multiple times. To address the issue of localized over-alkaliness caused by a single addition of alkali in existing technologies, sodium hydroxide is added in small, multiple batches with continuous stirring. This ensures uniform dissolution of sodium hydroxide in the diluent, guaranteeing a synchronous and slow increase in pH across all areas of the solution. This prevents rapid precipitation of aluminum ions caused by sudden increases in local pH, thus preventing the adsorption or encapsulation of ammonia nitrogen by aluminum hydroxide colloids during formation. Simultaneously, it avoids solution splashing caused by violent acid-base reactions, ensuring no loss of ammonia nitrogen and improving the accuracy of the measurement results.

[0009] Furthermore, in step S2, the pH adjustment process is monitored in real time using precision pH test paper or a digital pH meter, and the pH endpoint is strictly controlled within the range of 6.8-7.5. This invention addresses two major technical shortcomings of existing technologies due to the lack of real-time pH monitoring: First, when the pH value is below 6.8, acidity neutralization is incomplete, which still inhibits the colorimetric reaction in subsequent ammonia nitrogen determination, and aluminum ions cannot completely form aluminum hydroxide precipitate, making it impossible to remove aluminum interference through filtration. Second, when the pH value is above 9.0, ammonium ions in the solution will be converted into ammonia gas and volatilize, causing a large loss of ammonia nitrogen and resulting in severely low measurement results. The neutral to slightly alkaline range of 6.8-7.5 achieves complete acidity neutralization and sufficient precipitation of aluminum ions, while effectively preventing ammonia volatilization.

[0010] Furthermore, the dry filtration in step 3 uses ammonia-free slow or medium-speed quantitative filter paper, and the filter paper pore size is below 0.45μm; The technical problems caused by the use of ordinary filter paper or large-pore filter paper in existing technologies are as follows: First, ordinary filter paper is not treated to be ammonia-free, and the nitrogen impurities it contains will dissolve in the filtrate, causing exogenous nitrogen pollution and resulting in higher ammonia nitrogen measurement results. Second, filter paper with a pore size greater than 0.45μm cannot effectively retain the colloidal precipitate of aluminum hydroxide. The colloidal residue will cause turbidity in the filtrate, interfering with the subsequent spectrophotometric colorimetric detection and causing deviation in the absorbance measurement value. Ammonia-free slow / medium-speed quantitative filter paper with a pore size of less than 0.45μm can completely retain aluminum hydroxide colloids, while ensuring that the filtrate is free from exogenous nitrogen pollution, thus ensuring the accuracy of the measurement results.

[0011] Furthermore, in step S3, if the amount of aluminum hydroxide precipitate in the neutralized turbid liquid is too large, leading to a decrease in filtration efficiency, a centrifugal pretreatment step can be added before dry filtration. Specifically, the turbid liquid is placed in a centrifuge and centrifuged at 3000-4000 rpm for 5-10 minutes. The supernatant after centrifugation is then subjected to dry filtration. This solves the technical problems of filter paper clogging, excessively long filtration time, and ammonia nitrogen loss due to the adsorption of filtrate by the precipitate layer when the amount of aluminum hydroxide precipitate in high-aluminum-concentration tail liquid is too large. Centrifugation pretreatment can cause most of the aluminum hydroxide colloids to precipitate into large particles and settle to the bottom, while the supernatant contains only a small amount of fine precipitate, which greatly improves the efficiency of subsequent dry filtration and reduces the adsorption loss of ammonia nitrogen by the precipitate.

[0012] Furthermore, all glassware used in the method, including volumetric flasks, beakers, pipettes, colorimetric tubes, etc., undergo a pretreatment process of soaking and cleaning in 10% hydrochloric acid and rinsing repeatedly with ammonia-free water. This invention addresses the technical problem of residual ammonium salts and nitrogen-containing organic matter on the inner wall of glassware, which dissolve in the solution during sample processing, causing exogenous nitrogen contamination. 10% hydrochloric acid can react with and dissolve nitrogen-containing impurities on the surface of glassware, while rinsing with ammonia-free water can remove residual hydrochloric acid and impurities, ensuring that glassware is free from nitrogen contamination and avoiding external interference from the source of sample processing.

[0013] Furthermore, the standard method for determining ammonia nitrogen in step S4 is Nessler's reagent spectrophotometry (HJ535-2009), salicylic acid spectrophotometry, or continuous flow analysis. The above-mentioned standard methods are all suitable for the clear, interference-free, low-concentration ammonia nitrogen filtrate pretreated by this invention, solving the problem in the prior art of not selecting a suitable determination method for the characteristics of the filtrate after pretreatment of high-acid and high-alumina tail liquid: Nessler's reagent spectrophotometry is simple to operate and suitable for routine laboratory testing, salicylic acid spectrophotometry has stronger anti-interference ability and higher sensitivity, and continuous flow analysis is suitable for rapid determination of batch samples. All three methods can achieve accurate quantification of ammonia nitrogen in the filtrate, and the determination results have no compatibility conflict with the pretreatment process of this invention, ensuring the applicability and flexibility of the method.

[0014] Furthermore, in step S2, the volume of the diluent taken from solution A is approximately 50 mL, which balances the convenience of routine laboratory operations with the sample requirements for subsequent measurements. To address the technical issues arising from using too much or too little diluent: Using too much diluent increases the required amount of solid sodium hydroxide, prolongs the neutralization time, and generates excessive aluminum hydroxide precipitate, increasing the filtration burden. Using too little diluent fails to meet the parallel sample testing requirements for subsequent ammonia nitrogen determination, and the pH adjustment error rate is higher in small solutions. A 50mL dilution ensures sufficient filtrate while making the neutralization reaction and filtration operations more efficient, conforming to routine laboratory testing practices.

[0015] Compared with the prior art, the present invention has the following significant advantages: Only one 100-fold controlled dilution is performed to avoid the accumulation of errors caused by multiple dilution steps. Solid sodium hydroxide is used for neutralization, without introducing any additional water, thus maximizing the preservation of ammonia nitrogen concentration information in the tail liquid and solving the problem of insufficient sensitivity for low ammonia nitrogen detection caused by excessive dilution through liquid alkali neutralization. By diluting 100 times and neutralizing with solid alkali, the interference of strong acid on the colorimetric reaction and instrument detection is completely eliminated; by precisely controlling pH, precipitating and centrifuging, and dry filtration, the aluminum hydroxide colloid is completely removed, thus completely solving the problem of low test results caused by aluminum ion precipitation adsorption and encapsulation of ammonia nitrogen. Ammonia-free pretreatment of glassware and ammonia-free filter paper for dry filtration prevent external nitrogen contamination from the source; the pH range of 6.8-7.5 and the method of adding alkali in small amounts multiple times effectively prevent ammonia nitrogen loss caused by ammonia volatilization and solution splashing, and the spiked recovery rate can reach 90%-105%, which meets the requirements for quantitative detection. The entire process is a routine laboratory operation, carried out step by step, with a mild reaction and no special conditions such as high temperature or high pressure. The use of solid alkali reduces the amount of solution transportation and addition, and effectively avoids the corrosion risk of liquid alkali, making it suitable for daily laboratory monitoring and industrial batch sample testing. This invention is the first ammonia nitrogen determination method designed for the high acid and high aluminum special matrix of the tail liquid of the comprehensive utilization of platinum-containing waste catalyst. It solves the problem that the existing national standard method and other improved methods cannot be adapted to this type of sample, and fills the technical gap of no dedicated pretreatment and determination method for this type of complex matrix sample. It is suitable for platinum-containing waste catalyst tailings with sulfuric acid content of 4%-5.5%, aluminum content of 3%-6%, and ammonia nitrogen concentration of 0.1-100 mg / L. Nessler's reagent method, salicylic acid method, or continuous flow analysis method can be selected according to laboratory conditions to meet different detection needs. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1 A sample of tail liquid discharged from a platinum-containing waste catalyst comprehensive utilization production line was taken. Its basic parameters are: sulfuric acid content of about 5.0%, aluminum content of about 4.8%, and theoretical ammonia nitrogen concentration of about 15 mg / L (conventional matrix, no extreme interfering factors).

[0018] Sample dilution: Accurately transfer 1.00 mL of the above tailings into a 100 mL volumetric flask, dilute to the mark with ammonia-free pure water, and shake well to obtain solution A; pH adjustment: Take 50 mL of the solution into a clean beaker, and add about 0.2 g of analytical grade sodium hydroxide flakes in 5 small portions while stirring. Monitor the pH value in real time with a digital pH meter until the solution pH value reaches 7.0. Precipitation separation and filtration: After neutralization of the solution, aluminum hydroxide colloidal precipitate is formed, which is turbid. After standing for 2 minutes, it is directly filtered by dry filtration using 0.45μm ammonia-free slow quantitative filter paper, and the clear filtrate is collected. Ammonia nitrogen determination: Take the above clear filtrate and determine the ammonia nitrogen according to the HJ535-2009 Nessler's reagent spectrophotometric method. Perform the determination in parallel 3 times, record the data and calculate the average value. Results Calculation and Spiked Recovery: The original ammonia nitrogen concentration in the tailings was calculated according to the formula C0=C1×100. At the same time, a spiked recovery experiment was conducted by adding 1.0 mg / L ammonia nitrogen standard solution and recording the recovery rate.

[0019] Measurement of Example 1

[0020] Example 2 Another sample of tail liquid from the comprehensive utilization of platinum-containing waste catalyst was taken. Its basic parameters were: sulfuric acid content 4.2%, aluminum content 5.8%, theoretical ammonia nitrogen concentration of about 5.0 mg / L, high alumina matrix, and a large amount of aluminum hydroxide precipitation.

[0021] Sample dilution: Accurately transfer 1.00 mL of the tailings to be tested into a 100 mL volumetric flask, dilute to volume with ammonia-free pure water and shake well to obtain solution A; pH adjustment: Take 50 mL of the solution into a beaker, add approximately 0.18 g of analytical grade granular sodium hydroxide in 6 portions while stirring, and monitor the pH to 6.9 using a pH meter. Precipitation separation and filtration: The solution was turbid and the amount of aluminum hydroxide precipitate was large. The turbid liquid was first placed in a centrifuge and centrifuged at 3500 rpm for 8 min. The supernatant was taken and then filtered dry with 0.45 μm ammonia-free medium-speed quantitative filter paper. The clear filtrate was collected. Ammonia nitrogen determination: Take the filtrate and determine it according to the salicylic acid spectrophotometric method. Perform the determination in parallel 3 times, record the data and calculate the average value. Results calculation and spiked recovery: The original ammonia nitrogen concentration in the tail liquid was calculated according to the formula. For the spiked recovery experiment, 0.5 mg / L ammonia nitrogen standard solution was added.

[0022] Measurement of Example 2

[0023] Example 3 A sample of the waste catalyst tail liquid containing platinum was taken. Its basic parameters were: sulfuric acid content 5.5%, aluminum content 3.2%, and theoretical ammonia nitrogen concentration of approximately 0.5 mg / L.

[0024] Sample dilution: Accurately transfer 1.00 mL of the tail liquid to 100 mL of ammonia-free pure water in a volumetric flask and shake well to obtain solution A; pH adjustment: Take 50 mL of solution and add about 0.22 g of flake sodium hydroxide in 4 portions, stirring until pH = 7.2; Precipitation separation and filtration: Dry filtration was performed directly using 0.45μm ammonia-free slow quantitative filter paper, and the clear filtrate was collected; Ammonia nitrogen determination: The continuous flow analysis method is used for determination, which is suitable for the detection of low concentration ammonia nitrogen and has higher sensitivity. Six parallel determinations are performed, the data are recorded and the average value is calculated. Results Calculation and Spike Recovery: The original ammonia nitrogen concentration in the tail liquid was calculated according to the formula. In the spike recovery experiment, 0.2 mg / L ammonia nitrogen standard solution was added to simulate a low-concentration spike scenario.

[0025] Measurements were performed on Example 3.

[0026] Example 4 Take the same tail liquid sample as in Example 3 (5.5% sulfuric acid, 3.2% aluminum, 0.5 mg / L theoretical ammonia nitrogen), and replace the flake sodium hydroxide in step S2 with powdered sodium hydroxide. The rest of the steps are completely consistent with Example 3 to verify the technical defects of powdered alkali.

[0027] Sample dilution: Same as in Example 3; pH adjustment: Take 50 mL of solution and add about 0.22 g of powdered sodium hydroxide in 4 portions while stirring. Monitor the pH with a pH meter until it reaches 7.2. Precipitation separation and filtration: Same as in Example 3; Ammonia nitrogen determination: Same as in Example 3; Results calculation and spike recovery: Same as in Example 3.

[0028] Measurements were performed on Example 4.

[0029] Example 5 Take the same tail liquid sample as in Example 3 (5.5% sulfuric acid, 3.2% aluminum, 0.5 mg / L theoretical ammonia nitrogen), and adjust the pH endpoint in step S2 to 6.5. The rest of the steps are completely the same as in Example 3 to verify the effect of pH deviation.

[0030] Sample dilution: Same as in Example 3; pH adjustment: Take 50 mL of solution, add about 0.21 g of flake sodium hydroxide, and stir until pH = 6.5; Precipitation separation and filtration: Same as in Example 3; Ammonia nitrogen determination: Same as in Example 3; Results calculation and spike recovery: Same as in Example 3.

[0031] Measurements were performed on Example 5.

[0032] The average relative error, average spiking recovery rate, and operational complexity (1-5 points, with 5 points being the most complex) of the five examples were quantitatively compared. The results are shown in the table below:

[0033] The comparative data clearly shows that Example 3 is the optimal example: Example 3 deals with the most challenging low ammonia nitrogen + high acid and high alumina composite matrix of this method. Its average relative error is only 1.333%, which is much lower than Example 4 (16.0%) and Example 5 (24.0%), and slightly better than Example 1 (0.889%) with conventional matrix and Example 2 (2.0%) with high alumina matrix. This proves that the adaptability and accuracy of this method to extreme matrices are at the best level. The average recovery rate of Example 3 was 95.6%, which is at the upper limit of the quantitative detection acceptable range of 90%-105%. Moreover, the recovery rate fluctuation range of the six parallel determinations was only 94.9%-96.2%, and the repeatability was much better than that of Example 4 (86.8%-88.2%) and Example 5 (81.5%-83.1%). It was comparable to the recovery rate level of Examples 1 and 2, and was also suitable for low-concentration ammonia nitrogen spiking scenarios, making it more widely applicable. Example 3 eliminates the need for centrifugation pretreatment, simplifying the operation process while ensuring detection accuracy. The operation complexity is 2 points, consistent with Examples 1, 4, and 5, and lower than Example 2 (3 points), which better meets the efficiency requirements of routine laboratory testing and industrial batch sample processing. Example 3 uses a pH of 7.2, which is within the optimal range of 6.8-7.5. Parameters such as granular / flake sodium hydroxide, 0.45μm ammonia-free filter paper, and continuous flow analysis are precisely matched to the detection requirements of low ammonia nitrogen + high acid and high aluminum matrix. This completely solves the core problems of high acid inhibiting color development, aluminum ion embedding of ammonia nitrogen, and insufficient sensitivity for low concentration ammonia nitrogen from a technical perspective, and verifies the rationality and optimal combination of the technical parameters in the claims of this invention.

[0034] In summary, Example 3 demonstrates the best performance in terms of detection accuracy, recovery rate stability, operational efficiency, and technical parameter adaptability, fully reflecting the technical innovation and practical value of the method of the present invention.

[0035] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst, characterized in that, Includes the following steps: S1. Sample dilution: Accurately transfer 1.00 mL of the tail liquid to be tested into a 100 mL volumetric flask, dilute to the mark with ammonia-free pure water and mix thoroughly to obtain solution A, achieving 100-fold controllable dilution; S2, pH adjustment: Take a portion of the diluted solution from solution A and transfer it to a clean beaker. Use solid sodium hydroxide instead of traditional liquid alkali for neutralization, adding it while stirring until the pH of the solution reaches 6.8-7.

5. S3. Precipitation separation and filtration: For the turbid liquid that forms aluminum hydroxide colloidal precipitate after neutralization, dry filtration is performed using quantitative filter paper treated with ammonia-free, i.e. the filter paper is not pre-wetted, and the clear filtrate is collected for subsequent determination. S4. Ammonia Nitrogen Determination and Result Calculation: Take the above clarified filtrate and test it according to the standard method for ammonia nitrogen determination. Multiply the ammonia nitrogen concentration of the filtrate obtained by measurement by 100 times the total dilution factor to calculate the ammonia nitrogen concentration in the original tailings. The calculation formula is: C0=C1×100, where C0 is the ammonia nitrogen concentration in the original tailings (mg / L) and C1 is the ammonia nitrogen concentration obtained by measurement of the filtrate (mg / L).

2. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, The solid sodium hydroxide in step S2 is analytical grade granular or flake sodium hydroxide.

3. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 2, characterized in that, In step S2, the solid sodium hydroxide is added in small amounts multiple times while continuously stirring to ensure that the sodium hydroxide dissolves evenly in the diluent.

4. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, In step S2, the pH adjustment process is monitored in real time using precision pH test paper or a digital pH meter to control the pH endpoint within the range of 6.8-7.

5.

5. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, The dry filtration in step S3 uses ammonia-free slow or medium-speed quantitative filter paper with a pore size of less than 0.45 μm.

6. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, In step S3, if the amount of aluminum hydroxide precipitate in the neutralized turbid liquid is too large, resulting in a decrease in filtration efficiency, a centrifugal pretreatment step can be added before dry filtration: place the turbid liquid in a centrifuge and centrifuge at a speed of 3000-4000 rpm for 5-10 minutes, and then take the supernatant after centrifugation for dry filtration.

7. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, All glassware used in the method, including volumetric flasks, beakers, pipettes, and colorimetric tubes, underwent a pretreatment process of soaking and cleaning in 10% hydrochloric acid followed by repeated rinsing with ammonia-free water.

8. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, The standard method for determining ammonia nitrogen in step S4 is Nessler's reagent spectrophotometry, salicylic acid spectrophotometry, or continuous flow analysis.

9. The method for determining ammonia nitrogen in the tail liquid of platinum-containing waste catalyst comprehensive utilization according to claim 1, characterized in that, In step S2, the volume of the diluted solution taken from solution A is approximately 50 mL.

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