Aluminum sulfate quality analysis method based on multi-index determination

Abstract

The invention discloses an aluminum sulfate quality analysis method based on multi-index determination. The method comprises the following steps: S1, appearance and character; s2, measuring the content of aluminum sulfate; s3, determining the iron content; s4, determining the content of water insoluble substances; s5, determining the pH value; s6, heavy metal content determination; and S7, judging: integrating the measurement results of the indexes in the steps S1-S6, and judging whether the aluminum sulfate sample meets the related quality standard or not. The aluminum sulfate quality analysis method based on multi-index determination is simple, convenient, rapid and accurate to operate, can comprehensively evaluate the quality of aluminum sulfate, and can effectively control the product quality of aluminum sulfate by determining the indexes such as the aluminum sulfate content, the iron content, the water insoluble content, the pH value and the heavy metal content; the guarantee is provided for the application of the method in the field of water treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum sulfate mass analysis, and particularly relates to an aluminum sulfate mass analysis method based on multi-index determination. Background Art

[0002] Aluminum sulfate is an important inorganic chemical raw material, widely used in the field of water treatment. The quality of aluminum sulfate directly affects the performance and application effect of water treatment related products. Therefore, establishing an accurate and reliable aluminum sulfate quality analysis method is of great significance for controlling the product quality of aluminum sulfate.

[0003] At present, common aluminum sulfate mass analysis methods include gravimetric analysis, volumetric analysis, single spectral analysis, etc. These aluminum sulfate mass analysis methods all have some shortcomings.

[0004] Gravimetric analysis: (1) The operation is cumbersome and time-consuming: Gravimetric analysis usually requires that the specific components in aluminum sulfate be converted into a precipitate form, and then its content is determined through a series of steps such as filtering, washing, drying and weighing. Improper control of any condition may lead to incomplete precipitation or the introduction of impurities, thereby affecting the accuracy of the analysis results. After the precipitation is generated, multiple filtering and washing operations are required to remove impurities adsorbed on the surface of the precipitation. This process is not only cumbersome but also time-consuming. Insufficient washing may lead to residual impurities, resulting in a high measurement result; while excessive washing may cause the dissolution loss of the precipitate, resulting in a low result. In addition, the drying and weighing process also requires strict control of temperature and time to ensure that the moisture of the precipitate is completely removed and no decomposition or other chemical reactions occur. (2) Low sensitivity: Gravimetric analysis mainly determines the content of the component to be measured based on the mass of the precipitate. For components with low content, it may be difficult to accurately weigh the precipitate due to the small mass of the precipitate, resulting in a high detection limit and low sensitivity.

[0005] Volumetric analysis (such as acid-base titration): (1) Poor selectivity: Volumetric analysis is a method for determining the content of a substance based on the stoichiometric relationship of a chemical reaction. When determining aluminum sulfate, other components in the solution may react with the titrant, thereby interfering with the determination results. For complex aluminum sulfate samples, which may contain multiple components that can react with the titrant, volumetric analysis often has difficulty distinguishing the reactions of these components, making it impossible to accurately determine the content of aluminum sulfate. (2) Accuracy is greatly affected by operation: The accuracy of volumetric analysis depends to a large extent on the judgment of the titration end point. In actual operation, the judgment of the titration end point is often affected by many factors, such as the choice of indicator, the color change of the solution, and the visual judgment of the operator. Different operators may have different judgments on the titration end point, resulting in errors in the determination results. During the titration operation, errors may also be introduced, such as the reading of the burette and the control of the titration speed. If the titration speed is too fast, it may cause incomplete local reactions and affect the determination results; and inaccurate burette readings will directly lead to errors in the measurement of the titrant volume.

[0006] Single spectral analysis method (such as UV-visible spectrophotometry): (1) Limited analysis indicators: Single spectral analysis method can usually only measure components with specific absorption spectra in aluminum sulfate, and cannot comprehensively analyze the quality indicators of aluminum sulfate. It needs to be combined with other methods for comprehensive analysis. (2) Affected by interference factors: Coexisting substances in the sample may interfere with the measurement, resulting in spectral overlap or absorption enhancement or weakening. The matrix components of the solution, such as pH, ionic strength, etc., will also affect the spectral analysis. Under different matrix conditions, the absorption spectrum of the component to be measured may change, thereby affecting the reliability of the measurement results.

[0007] Therefore, it is very necessary to develop a method for analyzing the quality of aluminum sulfate with more comprehensive and accurate analysis results, simple and efficient operation and wide application range. The present invention establishes a method for analyzing the quality of aluminum sulfate based on multi-index determination, which is simple, fast and accurate to operate and can comprehensively evaluate the quality of aluminum sulfate. By determining the indicators such as aluminum sulfate content, iron content, water-insoluble matter content, pH value and heavy metal content, the product quality of aluminum sulfate can be effectively controlled, providing guarantee for its application in the field of water treatment. Summary of the invention

[0008] Purpose of the invention: In order to overcome the above shortcomings, the purpose of the present invention is to provide an aluminum sulfate quality analysis method based on multi-index determination, which is reasonably designed. By determining multiple indicators such as aluminum sulfate content, iron content, water-insoluble matter content, pH value and heavy metal content, the product quality of aluminum sulfate can be effectively controlled, providing a guarantee for its application in the field of water treatment, and has broad application prospects.

[0009] The objective of the present invention is achieved through the following technical solutions: A method for analyzing the quality of aluminum sulfate based on multi-index determination comprises the following steps: S1 Appearance and properties: Directly observe the appearance and properties of the aluminum sulfate sample under natural light or white fluorescent light; S2 Determination of aluminum sulfate content: The aluminum sulfate content of the aluminum sulfate sample was determined by EDTA complexometric titration; S3 Iron content determination: The iron content of aluminum sulfate samples was determined by o-phenanthroline spectrophotometry; S4 Determination of water-insoluble matter content: Determination of the water-insoluble matter content of the aluminum sulfate sample; S5 pH value determination: Use a pH meter to measure the pH value of the aluminum sulfate aqueous solution; S6 Heavy metal content determination: Flame atomic absorption spectrometry was used to determine the heavy metal content of aluminum sulfate samples; S7 judgment: comprehensively judging the measurement results of various indicators in steps S1-S6 to judge whether the aluminum sulfate sample meets the relevant quality standards.

[0010] In water treatment applications, not only the aluminum sulfate content will affect the flocculation effect, but too high iron content may cause water color changes, too much water-insoluble matter may clog the pipes, inappropriate pH value may affect the flocculation reaction, and excessive heavy metal content may cause harm to the environment and human health.

[0011] The aluminum sulfate quality analysis method of the present invention is based on multiple indicators for determination, covering the determination of multiple key indicators such as aluminum sulfate content, iron content, water-insoluble matter content, pH value, and heavy metal content. Through a comprehensive analysis of these indicators, the quality of aluminum sulfate can be more accurately evaluated, avoiding ignoring other potential problems due to the qualification of a single indicator, ensuring that the product meets more stringent quality standards, and being able to fully guarantee the application effect of aluminum sulfate in water treatment.

[0012] Among them, the present invention selects the most suitable determination method for different indicators, adopts EDTA complexometric titration to determine the content of aluminum sulfate, adopts o-phenanthroline spectrophotometry to determine the content of iron, adopts flame atomic absorption spectrometry to determine the content of heavy metals, etc. These methods have been verified by long-term practice and have high accuracy and precision, can effectively reduce errors in the analysis process, and improve the reliability of the analysis results.

[0013] Furthermore, in the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, the appearance and properties of the qualified aluminum sulfate sample in S1 are white crystalline powder or colorless transparent block or flaky crystals, and there are no visible impurities.

[0014] Appearance and properties are the most intuitive quality judgment indicators for aluminum sulfate. If there is an obvious color deviation in the aluminum sulfate sample, such as yellowing or graying, or there are impurities such as insoluble particles visible to the naked eye, it means that its appearance and properties do not meet the quality requirements.

[0015] Further, the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, said S2, specifically includes the following contents: (1) Weigh 0.5 g aluminum sulfate sample and place it in a 250 mL conical flask. Add water to dissolve it, then add 20 mL of 0.05 mol / L EDTA standard solution, heat and boil for 3-10 min, and cool to room temperature. (2) Add 2-3 drops of xylenol orange indicator and titrate with 0.05 mol / L zinc standard solution until the solution changes from yellow to purple-red. Record the volume of zinc standard solution consumed. , and at the same time, conduct a blank test and record the volume of zinc standard solution consumed ; (3) Calculate the content of aluminum sulfate using the following formula: ; in, is the mass fraction of aluminum sulfate, is the concentration of zinc standard solution, is the molar mass of aluminum sulfate, is the mass of aluminum sulfate sample.

[0016] The present invention adopts EDTA complexometric titration to determine the content of aluminum sulfate in an aluminum sulfate sample. Under acidic conditions, aluminum ions in the aluminum sulfate sample and EDTA form a stable complex. Xylenol orange is used as an indicator, and zinc standard solution is used to titrate excess EDTA, thereby calculating the content of aluminum sulfate.

[0017] Further, the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, S3, specifically includes the following contents: (1) Pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of iron standard solution (100 μg / mL) into a 50 mL volumetric flask, add 1 mL of 10% hydroxylamine hydrochloride solution, shake well, let stand for 5 min, then add 5 mL of 0.2% o-phenanthroline solution and 5 mL of acetic acid-sodium acetate buffer solution (pH = 4.5), dilute to the scale with water, and shake well; use the reagent blank as a reference, measure the absorbance at a wavelength of 510 nm, and draw a standard curve; (2) Weigh 1g of aluminum sulfate sample and place it in a 100mL beaker. Add water to dissolve it and transfer it to a 50mL volumetric flask. Follow the steps for drawing the standard curve and measure the absorbance. The iron content of the aluminum sulfate sample can be obtained from the standard curve. The calculation formula is as follows: ; in, is the mass fraction of iron, To find out the iron content of aluminum sulfate sample from the standard curve, is the mass of aluminum sulfate sample.

[0018] The invention adopts o-phenanthroline spectrophotometry to determine the iron content of an aluminum sulfate sample. Under the condition of pH=3-9, ferrous ions react with o-phenanthroline to generate a stable orange-red complex with maximum absorption at a wavelength of 510nm. The absorbance is measured and the iron content of the aluminum sulfate sample is calculated using a standard curve method.

[0019] Further, the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, said S4, specifically includes the following contents: (1) Weigh 10 g of aluminum sulfate sample, place it in a 250 mL beaker, add 100 mL of distilled water, heat to boiling, and keep it at a slight boil for 5-30 minutes; (2) Filter using a glass crucible that has been pre-conditioned at 105 - 110°C to achieve a constant weight, and wash the filtrate with hot water until there is no sulfate ion. Then, place the glass crucible and the filtrate in an oven and dry them at 105 - 110°C to a constant weight, and weigh the mass of the filtrate. (3) Calculate the content of water-insoluble matter based on the mass of the filtrate. The calculation formula is as follows: ; in, is the mass fraction of water-insoluble matter, is the mass of the filter, is the mass of aluminum sulfate sample. The present invention dissolves an aluminum sulfate sample in water, filters, washes, and dries, weighs the mass of water-insoluble matter (filtered matter), and calculates the content of the water-insoluble matter.

[0020] Furthermore, the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, S5, specifically includes the following contents: weigh 1g of aluminum sulfate sample, place it in a 100mL beaker, add 90mL of distilled water, stir to dissolve, and then measure the pH value of the solution with a pH meter.

[0021] Further, the above-mentioned aluminum sulfate quality analysis method based on multi-index determination, S6, specifically includes the following contents: (1) Weigh 0.5 g of aluminum sulfate sample and place it in a digestion tube. Then add nitric acid and perchloric acid and heat to digest until the solution in the digestion tube becomes clear. After cooling, dilute to a 50 mL volumetric flask. (2) Pipette heavy metal standard solutions of different concentrations into the above 50 mL volumetric flasks, add nitric acid and matrix modifier, dilute to scale with water, and shake well; select the corresponding analysis line on the flame atomic absorption spectrometer, measure the absorbance, and draw a standard curve; (3) Place the sample solution after desolvation in a 50 mL volumetric flask and operate according to the steps of drawing the standard curve to measure the absorbance. The heavy metal content of the aluminum sulfate sample can be obtained from the standard curve. The calculation formula is as follows: ; in, is the mass fraction of heavy metals, To check the heavy metal content of aluminum sulfate samples from the standard curve, is the mass of aluminum sulfate sample. The present invention adopts flame atomic absorption spectrometry to measure the heavy metal content of aluminum sulfate samples. After the aluminum sulfate samples are digested, the content of heavy metals (such as lead, cadmium, mercury, etc.) therein is determined by flame atomic absorption spectrometer. In the digestion process of the aluminum sulfate samples, appropriate amounts of nitric acid and perchloric acid are used for digestion, thereby avoiding the use of a large amount of strong acid and reducing pollution to the environment.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The aluminum sulfate quality analysis method based on multi-index determination described in the present invention is reasonably designed, including the determination of multiple key indicators such as aluminum sulfate content, iron content, water-insoluble matter content, pH value and heavy metal content. Compared with the single aluminum sulfate quality analysis method in the prior art, through the comprehensive analysis of these indicators, the quality of aluminum sulfate can be more accurately evaluated, avoiding ignoring other potential problems due to the qualification of a single indicator. The analysis results are more comprehensive and accurate, reducing analysis errors, and can fully guarantee the application effect of aluminum sulfate in water treatment; (2) The aluminum sulfate quality analysis method based on multi-index determination described in the present invention selects the most appropriate determination method for different indicators and simplifies the operation steps, avoiding complicated and cumbersome pre-treatment processes and lengthy analysis time. For example, in the determination of aluminum sulfate content, EDTA complexometric titration is used, which is relatively simple to operate and does not require the use of expensive and complex instruments and equipment. For example, when determining the iron content and heavy metal content, multiple aluminum sulfate samples can be digested and determined at one time, thereby improving the analysis efficiency. DETAILED DESCRIPTION

[0023] The following embodiment 1 is combined with specific experimental data to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The following Example 1 provides a method for analyzing the quality of aluminum sulfate.

[0024] Example 1 The aluminum sulfate quality analysis method of Example 1 is based on multiple indicators (including appearance and properties, aluminum sulfate content, iron content, water-insoluble matter content, pH value, heavy metal content) for determination, and then the determination results of all indicators are used to determine whether the aluminum sulfate sample meets the relevant quality standards, specifically including the following contents: (1) Appearance and properties: These are the most intuitive indicators of aluminum sulfate quality, mainly focusing on its color and state.

[0025] Directly observe the color and properties of the aluminum sulfate sample under natural light or white fluorescent light. Qualified aluminum sulfate samples should be white crystalline powder or colorless transparent block or flaky crystals without visible impurities.

[0026] (2) Aluminum sulfate content: a key indicator to measure the content of effective ingredients in aluminum sulfate samples. It reflects whether the actual content of aluminum sulfate in the aluminum sulfate sample meets the specified standard. For example, in water treatment applications, the content of aluminum sulfate directly affects its flocculation effect. If the content is insufficient, the expected water treatment effect may not be achieved.

[0027] Example 1 The content of aluminum sulfate in the aluminum sulfate sample was determined by EDTA complexometric titration, as follows: 1) Weigh 0.5g aluminum sulfate sample, accurate to 0.0001g, place it in a 250mL conical flask, add water to dissolve, then add 20mL 0.05mol / L EDTA standard solution, heat and boil for 5min, and cool to room temperature.

[0028] 2) Add 2-3 drops of xylenol orange indicator and titrate with 0.05 mol / L zinc standard solution until the solution changes from yellow to purple-red, and record the volume of zinc standard solution consumed. V 1 , and at the same time, conduct a blank test and record the volume of zinc standard solution consumed V 0 .

[0029] 3) Calculate the content of aluminum sulfate using the following formula: .

[0030] in, is the mass fraction of aluminum sulfate, is the concentration of zinc standard solution, is the molar mass of aluminum sulfate, is the mass of aluminum sulfate sample.

[0031] (3) Iron content: It is one of the important indicators of aluminum sulfate quality, because the presence of iron impurities may have an adverse effect on the application of aluminum sulfate. For example, in water treatment applications, iron impurities may cause side reactions and affect the water treatment effect.

[0032] Example 1 The iron content in the aluminum sulfate sample was determined by o-phenanthroline spectrophotometry, as follows: 1) Pipette 0.00, 1.00, 2.00, 3.00, 4.00, 5.00 mL of iron standard solution (100 μg / mL) into a 50 mL volumetric flask, add 1 mL of 10% hydroxylamine hydrochloride solution, shake well, let stand for 5 min, then add 5 mL of 0.2% o-phenanthroline solution and 5 mL of acetic acid-sodium acetate buffer solution (pH = 4.5), dilute to the scale with water, shake well; use the reagent blank as a reference, measure the absorbance at a wavelength of 510 nm, and draw a standard curve.

[0033] 2) Weigh 1g of aluminum sulfate sample, accurate to 0.0001g, place it in a 100mL beaker, add water to dissolve, and transfer to a 50mL volumetric flask; follow the steps of drawing the standard curve, measure the absorbance, and find the iron content of the aluminum sulfate sample from the standard curve. The calculation formula is as follows: .

[0034] in, is the mass fraction of iron, To find out the iron content of aluminum sulfate sample from the standard curve, is the mass of aluminum sulfate sample.

[0035] (4) Water-insoluble matter content: affects the solubility of aluminum sulfate in the solution and the effect of its use. For example, when preparing aluminum sulfate solution, water-insoluble matter may clog pipes, filters and other equipment, affecting the smooth progress of the production process; during the application process, water-insoluble matter may also affect its reaction efficiency with other substances.

[0036] Example 1 After dissolving the aluminum sulfate sample in water, filtering, washing, and drying, the mass of the insoluble matter was weighed, and the content of the water-insoluble matter was calculated as follows: 1) Weigh 10 g of aluminum sulfate sample, accurate to 0.0001 g, place it in a 250 mL beaker, add 100 mL of distilled water, heat to boiling, and keep it boiling for 20 minutes.

[0037] 2) Use a glass crucible that has been pre-conditioned at 105 - 110°C to filter, and use hot water to wash the filtrate until there is no sulfate ion (check with barium chloride solution). Then put the glass crucible and the filtrate into an oven, dry them at 105 - 110°C to constant weight, and weigh the mass of the filtrate.

[0038] 3) Calculate the content of water-insoluble matter based on the mass of the filtrate. The calculation formula is as follows: .

[0039] in, is the mass fraction of water-insoluble matter, is the mass of the filter, is the mass of aluminum sulfate sample. (5) pH value: reflects the acidity and alkalinity of aluminum sulfate solution. For example, in water treatment, the appropriate pH range helps aluminum sulfate to achieve the best flocculation effect. The pH value also affects the direction and rate of the reaction.

[0040] Example 1 The pH value of the aluminum sulfate aqueous solution was measured using a pH meter, as follows: Weigh 1g of aluminum sulfate sample, accurate to 0.0001g, place it in a 100mL beaker, add 90mL of distilled water, stir to dissolve, and then use a pH meter to measure the pH value of the solution.

[0041] (6) Heavy metal content: Excessive heavy metal content may cause harm to the environment and human health.

[0042] Example 1 Flame atomic absorption spectrometry was used to determine the heavy metal content in the aluminum sulfate sample, as follows: 1) Weigh 0.5 g of aluminum sulfate sample, accurate to 0.0001 g, and place it in a digestion tube. Then add nitric acid and perchloric acid, and heat to digest until the solution in the digestion tube becomes clear. After cooling, dilute to a 50 mL volumetric flask.

[0043] 2) Pipette heavy metal standard solutions of different concentrations into the above 50mL volumetric flasks, add nitric acid and matrix modifier, dilute to the scale with water, and shake well; on the flame atomic absorption spectrometer, select the corresponding analysis line, measure the absorbance, and draw the standard curve.

[0044] 3) Place the sample solution after desolvation in a 50mL volumetric flask and operate according to the steps of drawing the standard curve to measure the absorbance. The heavy metal content of the aluminum sulfate sample can be obtained from the standard curve. The calculation formula is as follows: .

[0045] in, is the mass fraction of heavy metals, To check the heavy metal content of aluminum sulfate samples from the standard curve, is the mass of aluminum sulfate sample.

[0046] The precision of Example 1 was tested: aluminum sulfate samples from the same batch were measured multiple times, and the relative standard deviation (RSD) of various indicators was calculated. The results showed that the precision of Example 1 was good, and the RSD was less than 5%. The accuracy of Example 1 was tested: the recovery rate of each index was calculated through a spike recovery test. The results showed that the recovery rate was between 95% and 105%, indicating that the accuracy of Example 1 was relatively high.

[0047] In summary, the present invention establishes a quality analysis method of aluminum sulfate based on multi-index determination, which is simple, fast, accurate, and can comprehensively evaluate the quality of aluminum sulfate. By determining multiple key indicators such as aluminum sulfate content, iron content, water-insoluble matter content, pH value, and heavy metal content, the product quality of aluminum sulfate can be effectively controlled, providing a guarantee for its application in the field of water treatment.

[0048] The present invention has many specific application paths, and the above is only a preferred embodiment of the present invention. It should be pointed out that the above embodiments are only used to illustrate the present invention, and are not used to limit the protection scope of the present invention. For those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for analyzing the quality of aluminum sulfate based on multi-index determination, characterized in that: The steps include: S1 Appearance and properties: Directly observe the appearance and properties of the aluminum sulfate sample under natural light or white fluorescent light; S2 Determination of aluminum sulfate content: The aluminum sulfate content of the aluminum sulfate sample was determined by EDTA complexometric titration; S3 Iron content determination: The iron content of aluminum sulfate samples was determined by o-phenanthroline spectrophotometry; S4 Determination of water-insoluble matter content: Determination of the water-insoluble matter content of the aluminum sulfate sample; S5 pH value determination: Use a pH meter to measure the pH value of the aluminum sulfate aqueous solution; S6 Heavy metal content determination: Flame atomic absorption spectrometry was used to determine the heavy metal content of aluminum sulfate samples; S7 judgment: comprehensively judging the measurement results of various indicators in steps S1-S6 to judge whether the aluminum sulfate sample meets the relevant quality standards.

2. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The appearance and properties of the qualified aluminum sulfate sample in S1 are white crystalline powder or colorless transparent block or flaky crystals without visible impurities.

3. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The S2 specifically includes the following contents: (1) Weigh 0.5 g of aluminum sulfate sample and place it in a 250 mL conical flask. Add water to dissolve it, then add 20 mL of 0.05 mol / L EDTA standard solution, heat and boil for 3-10 min, and cool to room temperature. (2) Add 2-3 drops of xylenol orange indicator and titrate with 0.05 mol / L zinc standard solution until the solution changes from yellow to purple-red. Record the volume of zinc standard solution consumed. , and at the same time, conduct a blank test and record the volume of zinc standard solution consumed ; (3) Calculate the content of aluminum sulfate using the following formula: ； in, is the mass fraction of aluminum sulfate, is the concentration of zinc standard solution, is the molar mass of aluminum sulfate, is the mass of aluminum sulfate sample.

4. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The S3 specifically includes the following contents: (1) Pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of iron standard solution (100 μg / mL) into a 50 mL volumetric flask, add 1 mL of 10% hydroxylamine hydrochloride solution, shake well, let stand for 5 min, then add 5 mL of 0.2% o-phenanthroline solution and 5 mL of acetic acid-sodium acetate buffer solution (pH = 4.5), dilute to the scale with water, and shake well; use the reagent blank as a reference, measure the absorbance at a wavelength of 510 nm, and draw a standard curve; (2) Weigh 1g of aluminum sulfate sample and place it in a 100mL beaker. Add water to dissolve it and transfer it to a 50mL volumetric flask. Follow the steps for drawing the standard curve and measure the absorbance. The iron content of the aluminum sulfate sample can be obtained from the standard curve. The calculation formula is as follows: ； in, is the mass fraction of iron, To check the iron content of aluminum sulfate sample from the standard curve, is the mass of aluminum sulfate sample.

5. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The S4 specifically includes the following contents: (1) Weigh 10 g of aluminum sulfate sample, place it in a 250 mL beaker, add 100 mL of distilled water, heat to boiling, and keep it at a slight boil for 5-30 minutes; (2) Filter using a glass crucible that has been pre-conditioned at 105 - 110°C to achieve a constant weight, and wash the filtrate with hot water until there is no sulfate ion. Then, place the glass crucible and the filtrate in an oven and dry them at 105 - 110°C to a constant weight, and weigh the mass of the filtrate. (3) Calculate the content of water-insoluble matter based on the mass of the filtrate. The calculation formula is as follows: ； in, is the mass fraction of water-insoluble matter, is the mass of the filter, is the mass of aluminum sulfate sample.

6. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The S5 specifically includes the following contents: weigh 1 g of aluminum sulfate sample, place it in a 100 mL beaker, add 90 mL of distilled water, stir to dissolve, and then measure the pH value of the solution with a pH meter.

7. The aluminum sulfate quality analysis method based on multi-index determination according to claim 1, characterized in that, The S6 specifically includes the following contents: (1) Weigh 0.5 g of aluminum sulfate sample and place it in a digestion tube. Then add nitric acid and perchloric acid and heat to digest until the solution in the digestion tube becomes clear. After cooling, dilute to a 50 mL volumetric flask. (2) Pipette heavy metal standard solutions of different concentrations into the above 50 mL volumetric flasks, add nitric acid and matrix modifier, dilute to scale with water, and shake well; select the corresponding analysis line on the flame atomic absorption spectrometer, measure the absorbance, and draw a standard curve; (3) Place the sample solution after desolvation in a 50 mL volumetric flask and operate according to the steps of drawing the standard curve to measure the absorbance. The heavy metal content of the aluminum sulfate sample can be obtained from the standard curve. The calculation formula is as follows: ； in, is the mass fraction of heavy metals, To check the heavy metal content of aluminum sulfate samples from the standard curve, is the mass of aluminum sulfate sample.

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