A method for detecting chloride ions in coking ammonium sulfate mother liquor based on cascade oxidation-pyrolysis coupling pretreatment
By employing a stepwise oxidation-pyrolysis coupled pretreatment method, the accuracy problem of chloride ion detection in coking ammonium sulfate mother liquor was solved, enabling accurate and rapid determination under high interference backgrounds and reducing detection costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TONGLING XIN YAXING COKING&CHEM CO LTD
- Filing Date
- 2026-03-27
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies make it difficult to accurately and quickly determine the chloride ion content in coking ammonium sulfate mother liquor. Conventional methods are severely affected by interfering substances, resulting in inaccurate test results and high costs.
A stepwise oxidation-pyrolysis coupled pretreatment method was adopted, including dilution, alkaline oxidation, acidic pyrolysis and neutralization titration. By controlling the pH value and using hydrogen peroxide solution, interfering substances were eliminated, ensuring that the titration endpoint was clearly identifiable.
It achieves high accuracy and reproducibility in chloride ion concentration measurement under high interference background, with a relative error of less than 5%, meeting the requirements of industrial analysis and reducing detection costs.
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Figure CN122193499A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ion detection, and in particular to a method for detecting chloride ions in coking ammonium sulfate mother liquor based on a stepwise oxidation-pyrolysis coupled pretreatment. Background Technology
[0002] During the coking process, coal produces a large amount of raw coal gas under high-temperature dry distillation conditions. Raw coal gas has a complex composition. In order to achieve resource recycling and environmentally friendly emissions, the raw coal gas is purified to recover its chemical products. The most common method is to use sulfuric acid absorption to recover ammonia from the raw coal gas. Specifically, sulfuric acid mother liquor is used as an absorbent to react with ammonia in the raw coal gas to produce ammonium sulfate, which is then crystallized and recovered. This ammonium sulfate can be used as an important agricultural fertilizer and industrial raw material.
[0003] In the ammonium sulfate production unit, the sulfuric acid mother liquor needs to be continuously circulated between the absorption tower and the crystallization system. Chlorine in the raw coal is converted into hydrogen chloride or ammonium chloride through high-temperature dry distillation, which then enters the raw coal gas, resulting in the raw coal gas containing some chlorine components. As production continues, chloride ions accumulate in the sulfuric acid mother liquor, and the chloride ion concentration gradually increases. This increase in chloride ion concentration causes a series of problems, including: chloride ions are highly corrosive, thus accelerating the corrosion of equipment and pipelines and shortening equipment lifespan; the presence of chloride ions significantly affects the ammonium sulfate crystallization process, interfering with normal crystal growth, leading to smaller crystal size, irregular morphology, and increased difficulty in subsequent centrifugation and drying; furthermore, chloride ions can also enter the finished ammonium sulfate product as impurities, reducing product purity and affecting product quality.
[0004] Therefore, by monitoring the chloride ion content in the coking ammonium sulfate mother liquor after long-term circulation, it is possible to effectively guide the sewage discharge operation in the production process, control the concentration of impurities in the mother liquor, stabilize the quality of the mother liquor, and thus help extend the equipment operating cycle and ensure product quality.
[0005] However, coking ammonium sulfate mother liquor is a matrix with an extremely complex composition. In addition to containing a high concentration of ammonium sulfate, it also contains a large number of interfering substances. For example, components such as hydrogen cyanide and hydrogen sulfide in raw coal gas react with the absorbent to generate various sulfur-containing compounds such as thiocyanate, thiosulfate, and sulfides. There are also unreacted organic substances, as well as ammonium ions and sulfate ions. These interfering substances can seriously affect the accurate determination of chloride ions.
[0006] In conventional methods for chloride ion detection, such as potassium chromate indicator titration, interfering substances in the coking ammonium sulfate mother liquor preferentially react with silver ions to form precipitates, severely interfering with the determination of the titration endpoint and leading to complete failure. On the other hand, instrumental analysis methods such as ion chromatography are prone to column contamination due to interfering substances, resulting in poor separation, signal drift, and compromised accuracy and reproducibility of analytical results. Furthermore, the high maintenance costs of these instruments make them unsuitable for the needs of rapid on-site detection.
[0007] To address these issues, researchers attempted to pretreat the coking ammonium sulfate mother liquor before detection to eliminate or mask interfering substances. A common pretreatment method is hydrogen peroxide oxidation. However, in practice, it was found that directly adding hydrogen peroxide to the acidic coking ammonium sulfate mother liquor causes the decomposition of thiosulfate in the interfering substances, generating elemental sulfur precipitate. Furthermore, the oxidation process also oxidizes organic matter into carbonates, introducing new carbonaceous impurities and causing errors in subsequent detection. Moreover, the pretreatment process requires the addition of excessive hydrogen peroxide, and the residual hydrogen peroxide can affect the color change reaction of the indicator during subsequent titration, causing the detection results to deviate from the true value.
[0008] Therefore, it is of great significance to obtain a method for accurately and rapidly determining chloride ion content in complex systems with extremely high ionic strength, high organic loading, and the coexistence of multiple reducing sulfides. Summary of the Invention
[0009] This invention provides a method for detecting chloride ions in coking ammonium sulfate mother liquor based on a stepped oxidation-pyrolysis coupled pretreatment. This method can solve the problems in the prior art where there are many interfering substances, sulfur precipitation and turbidity are difficult to avoid, and the chloride ion content cannot be accurately and quickly determined when detecting chloride ion concentration in coking ammonium sulfate mother liquor.
[0010] A method for chloride ion detection in coking ammonium sulfate mother liquor based on a stepped oxidation-pyrolysis coupled pretreatment includes the following process steps: S1. Dilute the filtered mother liquor of coking ammonium sulfate to be tested with water to obtain a homogenized mother liquor; S2. Add alkaline regulator and acid-base regulator to the homogenized mother liquor to control the pH value of the solution to always be maintained at 10-12, add hydrogen peroxide solution to carry out oxidation, and obtain oxidized mother liquor; S3. Lower the temperature of the oxidation mother liquor, add an acid regulator, control the pH of the solution to 2-3, and carry out pyrolysis to obtain the pretreated mother liquor; S4. Using phenolphthalein as an indicator, neutralize the pretreated mother liquor with alkaline and acidic regulators to adjust the pH to 6.5–7.5, and determine the endpoint using pH test paper; then determine the chloride ion content by molar titration.
[0011] Preferably, the molar titration method specifically includes the following steps: S401. Take the neutralized pretreatment mother liquor as the sample solution; S402. Add potassium chromate indicator to the sample solution and titrate with silver nitrate standard solution until a persistent brick-red precipitate is produced; S403. Set up a blank control group, replace the sample solution with an equal volume of water for titration, and finally calculate the chloride ion content in the coking ammonium sulfate mother liquor.
[0012] Preferably, the chloride ion content in the coking ammonium sulfate mother liquor is calculated according to the following formula: ;where V 样 V represents the volume of silver nitrate standard solution consumed in the titration. 空白 V represents the volume of silver nitrate standard solution consumed by the blank control group. 取样量 Indicates the volume of the sample solution. The value indicates the concentration of the silver nitrate standard solution, and f represents the dilution factor.
[0013] Preferably, the dilution ratio of the filtered coking ammonium sulfate mother liquor to be tested to water is 10 to 50 times.
[0014] More preferably, the diluted solution of the filtered coking ammonium sulfate mother liquor is diluted with water by a factor of 20.
[0015] By adopting the above technical solution, the mother liquor of coking ammonium sulfate to be tested is first filtered to remove suspended tar and mechanical impurities. Then, water is added to dilute and homogenize it. By reducing the ionic strength of the mother liquor of coking ammonium sulfate to be tested, the adsorption effect of the system is reduced, and the absolute concentration of reducing components in the interfering substances of the mother liquor is reduced, thereby effectively preventing the subsequent oxidation reaction from being too violent and causing splashing.
[0016] Then, a strongly alkaline peroxidation system was constructed in the homogenized mother liquor. Utilizing the strong nucleophilicity of hydrogen peroxide under alkaline conditions, interfering substances in the mother liquor, including thiosulfate and thiocyanate, were oxidized to sulfate and cyanate, as shown in the following reaction equation: ; ; ; By first creating a strongly alkaline environment, the pathway for the disproportionation of thiosulfate to generate elemental sulfur can be thermodynamically blocked, thereby ensuring that the mother liquor is clear and transparent, which is beneficial for determining the titration endpoint.
[0017] Furthermore, in the mother liquor of coking ammonium sulfate, since the solubility product of silver thiocyanate is much smaller than that of silver chloride, silver thiocyanate is two orders of magnitude less soluble than silver chloride. During silver ion titration, silver ions will first precipitate all the thiocyanate before starting to precipitate chloride ions. Thiocyanate has a significant interference effect on chloride ion titration. This invention, by operating in an alkaline environment, can avoid the formation of elemental sulfur precipitate and polythionite from thiocyanate.
[0018] On the other hand, hydrogen peroxide exists mainly as hydrogen peroxide anions under alkaline conditions. As a strong nucleophile, it can specifically attack the SS bond in thiocyanate, reducing the quantitative oxidation to sulfate ions. The carbon-nitrogen bond breaks to generate cyanate ions, thereby eliminating the possibility of thiocyanate precipitating with silver ions in the subsequent titration process.
[0019] This avoids the problem of hydrogen peroxide causing disproportionation of elemental sulfur under acidic conditions in the mother liquor.
[0020] The oxidation mother liquor is then further processed. Specifically, an acidic pyrolysis system is constructed for the oxidation mother liquor. Hydrogen peroxide is extremely unstable under acidic thermal conditions. Therefore, this property is utilized to allow the residual hydrogen peroxide to undergo disproportionation decomposition. Since the residual hydrogen peroxide itself has both redox properties, it can reduce silver ions, which can lead to fading of the titration endpoint or titration instability in subsequent titrations. The residual hydrogen peroxide is decomposed by catalysis in a hot acid environment, effectively avoiding the influence of residual hydrogen peroxide on the subsequent titration process.
[0021] Meanwhile, under acidic conditions, the cyanate ions produced by the oxidation of thiocyanate and the carbonate ions produced by the oxidation of organic matter during the oxidation process will decompose under hot acid conditions, releasing carbon dioxide. This can prevent the formation of precipitates between cyanate ions and carbonate ions and silver ions, thus avoiding interference with the detection of chloride ions. Moreover, under hot acid conditions, trace amounts of residual organic tar in the mother liquor can be further degraded, improving the clarity of the titration endpoint observation.
[0022] Finally, using alkaline and acidic adjusters, the pH of the solution is adjusted to the optimal range for molar titration, avoiding the formation of silver oxide due to excessive alkalinity or silver dichromate due to excessive acidity. Furthermore, at this point, interfering substances in the mother liquor are converted into inert ions that do not react with silver ions, creating a favorable environment for molar titration. Therefore, molar titration can be performed under interference-free conditions, and the titration endpoint is clearly identifiable.
[0023] Preferably, in step S2, the oxidation temperature is 90–95°C and the oxidation time is 10–15 min.
[0024] Preferably, in step S3, the temperature of the oxidation mother liquor is reduced to 50–70°C.
[0025] Preferably, in step S3, the pyrolysis temperature is 95–100°C and the pyrolysis time is 15–25 min.
[0026] Preferably, the alkalinity regulator includes sodium hydroxide, and the acid-base indicator includes phenolphthalein reagent.
[0027] Preferably, the volume ratio of hydrogen peroxide solution to homogenization mother liquor is (0.25~0.5):1.
[0028] More preferably, the concentration of the hydrogen peroxide solution is 30%.
[0029] Preferably, the acid regulator includes either dilute nitric acid or dilute sulfuric acid.
[0030] The beneficial effects of this invention are: 1. The present invention provides a method for chloride ion detection in coking ammonium sulfate mother liquor based on a stepped oxidation-pyrolysis coupled pretreatment. This method employs a linked mechanism of alkaline oxidation, acidic pyrolysis, and neutralization titration. Alkaline oxidation addresses the turbidity of the mother liquor, protects chloride ions, and decomposes interfering substances. Acidic pyrolysis further eliminates interference from carbonate, cyanate, and residual hydrogen peroxide. Finally, neutralization titration is performed to achieve low-cost quantitative analysis of chloride ions. Even under extremely high interference conditions, the relative error in chloride ion concentration measurement can be less than 5%, significantly improving the accuracy and reproducibility of chloride ion detection.
[0031] 2. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on step-by-step oxidation-pyrolysis coupled pretreatment provided by this invention can not only eliminate detection errors and solve the problem of elemental sulfur precipitation under acidic oxidation, but also make the mother liquor obtained after pretreatment clear, so that the brick-red endpoint of the molar titration method can be clearly identified, which greatly improves the precision of titration.
[0032] 3. The method for chloride ion detection in coking ammonium sulfate mother liquor based on step-by-step oxidation-pyrolysis coupled pretreatment provided by this invention introduces a variety of reagents during alkaline oxidation and acidic pyrolysis, but does not introduce new interfering ions and will not affect the chloride ion titration. Moreover, the residual hydrogen peroxide is completely removed by pyrolysis, demonstrating extremely high chemical self-consistency. Attached Figure Description
[0033] Figure 1 The curve is a fitting curve of the spiked recovery rate of the sample in Example 1 of this invention. Detailed Implementation
[0034] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.
[0035] Example
[0036] Example 1: A method for chloride ion detection in coking ammonium sulfate mother liquor based on a stepped oxidation-pyrolysis coupled pretreatment, comprising the following process steps: S1. Take the mother liquor of coking ammonium sulfate to be tested. The mother liquor is dark brown in appearance and has a tar smell. Filter it through medium-speed filter paper. Then take 5 mL of the filtered mother liquor of coking ammonium sulfate to be tested, dilute it with water at a dilution ratio of 20 times, and shake it well to obtain a homogenized mother liquor. S2. Take 20 mL of homogenized mother liquor, add 30 mL of water, add 2 drops of phenolphthalein reagent, and add 20% sodium hydroxide solution. Control the pH value of the solution to be kept at 11 throughout the process. Use pH test paper to monitor the pH value. Add 5 mL of 30% hydrogen peroxide solution to carry out oxidation. The oxidation temperature is 90℃. Keep it at this temperature for 15 min to obtain the oxidation mother liquor. At this time, the color of the oxidation mother liquor gradually becomes lighter. S3. Reduce the temperature of the oxidation mother liquor to 60℃, add dilute nitric acid, control the pH of the solution to 2.5, and carry out pyrolysis. The pyrolysis temperature is 98℃, and the solution is kept at this temperature for 15 minutes to obtain the pretreated mother liquor. The pretreated mother liquor has a clear and transparent appearance. S4. After cooling the pretreated mother liquor to room temperature, add 2 drops of phenolphthalein reagent and neutralize with sodium hydroxide and dilute nitric acid to adjust the pH of the pretreated mother liquor to 7. The endpoint is determined using pH test paper. Then, the chloride ion content is determined by molar titration. Specifically: S401. Take 20 mL of the neutralized pretreatment mother liquor as the sample solution; S402. Add 0.2 mL of potassium chromate indicator to the sample solution and titrate with a 0.1 mol / L silver nitrate standard solution, shaking vigorously during the process until a persistent brick-red precipitate is formed and remains unchanged for 30 seconds. S403. Set up a blank control group, replace the sample solution with an equal volume of water for titration, and finally calculate the chloride ion content in the coking ammonium sulfate mother liquor.
[0037] For the same sample of coking ammonium sulfate mother liquor, four parallel determinations were performed using the method described above, and the chloride ion concentration was calculated using the following formula: , The experimental data and results are shown in Table 1. =0.1mol / L: Table 1. Results of Parallel Tests
[0038] As shown in Table 1, the average concentration of chloride ions in the coking ammonium sulfate mother liquor tested using the method provided in Example 1 was calculated to be 12496.13 mg / L, with a standard deviation of 177.25 mg / L and a relative standard deviation of 1.42%, which meets the requirements for industrial analysis.
[0039] Comparative Example
[0040] Comparative Example 1: A method for detecting chloride ions in coking ammonium sulfate mother liquor based on oxidation, comprising the following process steps: S1. Take the mother liquor of coking ammonium sulfate to be tested. The mother liquor is dark brown in appearance and has a tar smell. Filter it through medium-speed filter paper. Then take 5 mL of the filtered mother liquor of coking ammonium sulfate to be tested, dilute it with water at a dilution ratio of 20 times, and shake it well to obtain a homogenized mother liquor. S2. Take 20 mL of homogenized mother liquor, add dilute nitric acid to control the pH of the solution to 2.5, then add 5 mL of 30% hydrogen peroxide solution and carry out oxidative pyrolysis at 90℃ for 15 min to obtain pretreated mother liquor. The pretreated mother liquor is turbid and has precipitate. S3. After the pretreatment mother liquor is cooled to room temperature, 2 drops of phenolphthalein reagent are added, and the solution is neutralized with sodium hydroxide and dilute nitric acid to adjust the pH value of the pretreatment mother liquor to 7. After filtration, the chloride ion content is determined by molar titration.
[0041] During the molar titration process, the endpoint is dark gray, making it difficult to identify the brick-red abrupt change. The results of four parallel determinations were extremely unstable, and the calculated chloride ion concentration fluctuated greatly with a relative standard deviation of >30%, making it impossible to accurately determine the chloride ion concentration in the coking ammonium sulfate mother liquor.
[0042] Performance testing
[0043] Spike recovery experiment: The sample spike recovery experiment was used to verify whether the chloride ion detection method of coking ammonium sulfate mother liquor based on the step-by-step oxidation-pyrolysis coupled pretreatment obtained in Example 1 completely eliminated the positive bias (interference of interfering substances) and the negative bias (loss of chloride ions). The specific experimental steps are as follows: Weigh out 4 equal volumes of the homogenized mother liquor obtained in Example 1; The first group is the background sample group, where the chloride ion concentration is determined using the method in Example 1, and used as the benchmark for calculating the recovery rate; The second to fourth groups were spiked sample groups. Sodium chloride standard solution with a concentration of 0.1 mol / L was added to the homogenized mother liquor in volumes of 1 mL, 2 mL and 3 mL, respectively. Then, the chloride ion concentration was determined by the method provided in Example 1, and the volume of silver nitrate standard solution consumed during the actual titration was recorded.
[0044] Calculate the volume of silver nitrate standard solution that is theoretically required for each titration.
[0045] Then, the recovery rates of the second to fourth groups were calculated as follows: Recovery rate (%) = (Measured value of spiked sample - Measured value of background sample) / Spiked amount × 100%.
[0046] The experimental data and results are shown in Table 2 and 2. Figure 1 As shown: Table 2 Results of spiked recovery experiment
[0047] The calculated average recovery rate was 103.8%.
[0048] According to Table 2 and Figure 1 As can be seen from Example 1, the recovery rate calculated by the method for detecting chloride ions in coking ammonium sulfate mother liquor based on the step-by-step oxidation-pyrolysis coupled pretreatment provided in Example 1 is <105% through sample spike recovery rate experiments. This indicates that the method for detecting chloride ions in coking ammonium sulfate mother liquor provided by the present invention is accurate and reliable.
[0049] The preliminary alkaline oxidation and acidic pyrolysis treatments effectively eliminate interference from thiocyanates and thiosulfates present in the coking ammonium sulfate mother liquor. In other words, even if trace amounts of highly difficult-to-oxidize organic sulfur are still present, their impact on chloride ion detection results is within a controllable range. Compared to the 300-500% false recovery rate of samples directly detecting chloride ions in untreated coking ammonium sulfate mother liquor, the chloride ion detection method provided by this invention effectively removes impurity interference and significantly reduces positive bias. Simultaneously, the chloride ion detection method of this invention does not cause chloride ion adsorption, volatilization, or precipitation loss, effectively avoiding negative bias. Furthermore, the results maintain good linearity across a wide range of chloride ion concentrations, indicating that the method has high robustness and reproducibility, and also exhibits strong tolerance to high concentrations of ammonium sulfate in the coking ammonium sulfate mother liquor.
[0050] Furthermore, as can be seen from Example 1 and Comparative Example 1, after conducting multiple parallel experiments, the chloride ion detection method provided in Example 1 exhibits good reproducibility, with minimal differences in chloride ion concentration, and the results are reliable. This demonstrates that even in complex matrices such as coking ammonium sulfate mother liquor, which contains extremely high ionic strength (i.e., saturated ammonium sulfate), extremely high organic loading, and multiple reducing sulfur-containing interfering substances, the chloride ion detection method provided by this invention can accurately and rapidly determine the chloride ion content in the matrix. It can minimize the influence of interfering substances such as thiocyanate, thiosulfate, and sulfides, which have concentrations as high as several thousand milligrams per liter in the mother liquor, with a relative standard deviation of less than 1.5%, meeting the requirements of industrial analysis.
[0051] In Comparative Example 1, hydrogen peroxide was directly added to the acidic mother liquor for oxidation treatment. During this process, polythionate and elemental sulfur are easily generated. The elemental sulfur precipitate is difficult to remove by simple filtration, which will affect the determination of the titration endpoint, resulting in large fluctuations in the chloride ion content of the measurement results, large relative standard deviation, and low feasibility and poor precision of the obtained analytical results.
[0052] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.
Claims
1. A method for detecting chloride ions in coking ammonium sulfate mother liquor based on a stepped oxidation-pyrolysis coupled pretreatment, characterized in that, The process includes the following steps: S1. Dilute the filtered mother liquor of coking ammonium sulfate to be tested with water to obtain a homogenized mother liquor; S2. Add alkaline regulator and acid-base regulator to the homogenized mother liquor to control the pH value of the solution to always be maintained at 10-12, add hydrogen peroxide solution to carry out oxidation, and obtain oxidized mother liquor; S3. Lower the temperature of the oxidation mother liquor, add an acid regulator, control the pH of the solution to 2-3, and carry out pyrolysis to obtain the pretreated mother liquor; S4. Using phenolphthalein as an indicator, neutralize the pretreated mother liquor with alkaline and acidic regulators to adjust the pH to 6.5–7.5, and determine the endpoint using pH test paper; then determine the chloride ion content by molar titration.
2. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, The molar titration method specifically includes the following steps: S401. Take the neutralized pretreatment mother liquor as the sample solution; S402. Add potassium chromate indicator to the sample solution and titrate with silver nitrate standard solution until a persistent brick-red precipitate is produced; S403. Set up a blank control group, replace the sample solution with an equal volume of water for titration, and finally calculate the chloride ion content in the coking ammonium sulfate mother liquor.
3. The method for chloride ion detection in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 2, characterized in that, The chloride ion content in the coking ammonium sulfate mother liquor is calculated according to the following formula: ;where V 样 V represents the volume of silver nitrate standard solution consumed in the titration. 空白 V represents the volume of silver nitrate standard solution consumed by the blank control group. 取样量 Indicates the volume of the sample solution. The value indicates the concentration of the silver nitrate standard solution, and f represents the dilution factor.
4. The method for chloride ion detection in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, The filtered coking ammonium sulfate mother liquor to be tested is diluted with water by a ratio of 10 to 50 times.
5. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, In step S2, the oxidation temperature is 90–95°C and the oxidation time is 10–15 min.
6. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on staged oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, In step S3, the temperature of the oxidation mother liquor is reduced to 50-70°C.
7. The method for chloride ion detection in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, In step S3, the pyrolysis temperature is 95–100°C, and the pyrolysis time is 15–25 min.
8. The method for chloride ion detection in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, The alkalinity regulator includes sodium hydroxide, and the acid-base indicator includes phenolphthalein reagent.
9. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, The volume ratio of the hydrogen peroxide solution to the homogenization mother liquor is (0.25~0.5):
1.
10. The method for detecting chloride ions in coking ammonium sulfate mother liquor based on stepped oxidation-pyrolysis coupled pretreatment according to claim 1, characterized in that, The acid regulator includes either dilute nitric acid or dilute sulfuric acid.