Method for rapidly detecting gas-phase sulfide in alkaline environment

Abstract

The invention discloses a method for rapidly detecting gas-phase sulfide in an alkaline environment, and belongs to the technical field of analytical chemistry. The method comprises the following steps: S1, preparing a reaction solution: taking a 25ml colorimetric tube, adding 3mL of a 0.1 wt% ferric trichloride solution and 5mL of 25wt% ammonia water, and adding water to dilute to 25mL to obtain the reaction solution with ferric hydroxide precipitate; s2, taking a gas sample to be detected, and introducing the gas sample into the reaction solution for reaction; s3, observing the color and precipitation state of the reaction solution; s4, determining the concentration range of sulfide in the reaction solution after the reaction by contrasting with the standard colorimetric solution; and S5, calculating the sulfide concentration in the gas sample to be detected according to the sulfide concentration in the reaction solution. According to the present invention, the ferric chloride and the sulfide are subjected to the chemical reaction in the alkaline environment, and the precipitate generated by the reaction and the presented color change are compared with the standard colorimetric solution so as to achieve the semi-quantitative detection of the hydrogen sulfide, such that the method is suitable for on-site rapid detection and determination.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and more particularly to a method for rapidly detecting gaseous sulfide in an alkaline environment. Background Art

[0002] In the fields of chemical industry, environmental protection, etc., sulfides in sulfide-containing alkaline waste gas often exist in the form of gaseous H2S. Excessive H2S concentration in the waste gas will corrode equipment, affect catalyst activity, and even lead to environmental protection failure.

[0003] Current methods for detecting hydrogen sulfide include methylene blue spectrophotometry, iodine titration, lead acetate test paper, electrochemical sensor, gas chromatography, and spectroscopy. Methylene blue spectrophotometry involves reacting the gas phase of sulfide with aminodimethylaniline to produce blue methylene blue, and then measuring the absorbance using a spectrophotometer. This method is complex, time-consuming, and susceptible to interference from reducing substances. Iodine titration involves a redox reaction between hydrogen sulfide and iodine, followed by titration of the excess iodine with sodium thiosulfate. The hydrogen sulfide concentration is calculated based on the iodine consumption. This method requires titration and endpoint determination, making it unsuitable for rapid on-site detection. The lead acetate test paper method involves the reaction of hydrogen sulfide with lead acetate to produce a black lead sulfide precipitate. The concentration is qualitatively or semi-quantitatively determined by the color change of the test paper. This method is susceptible to humidity and light exposure, and requires demanding storage conditions. The electrochemical sensor method involves a redox reaction between hydrogen sulfide and lead acetate, generating a current signal proportional to the concentration. However, the electrolyte and electrodes in this method are susceptible to aging, and humidity fluctuations can also affect stability. Gas chromatography involves separating samples through gas chromatography and then detecting hydrogen sulfide using FPD and SCD. This method requires professional operation and maintenance, complex sample pretreatment, and a long analysis cycle, making it unsuitable for rapid on-site operation. Spectroscopy involves the reaction of hydrogen sulfide with a developer to form a colored compound, which is then measured for absorbance. This method is costly, has complex steps, and uses unstable reagents. These methods are aimed at the direct determination of sulfides in alkaline gases, and each has problems such as method inapplicability, difficulty in eliminating interference, high cost, and low efficiency. Therefore, there is an urgent need to develop a new detection method that does not require acidification pretreatment, is resistant to alkaline interference, and is easy to operate, to fill the gap in sulfide detection technology in alkaline environments. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for rapidly detecting gaseous sulfides in an alkaline environment.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for rapidly detecting gaseous sulfide in an alkaline environment comprises the following steps:

[0007] S1. Take a 25ml colorimetric tube, add 3ml of 0.1wt% ferric chloride solution and 5ml of 25wt% ammonia water, dilute with water to obtain 25ml of a display solution containing ferric hydroxide precipitate;

[0008] S2, taking a gas sample to be tested and passing it into a display agent solution containing ferric hydroxide precipitate to react;

[0009] S3. Observe the color and precipitation state of the solution after the reaction, and compare the color and precipitation state of the solution with those of a standard colorimetric solution, and determine the concentration range of sulfide in the solution after the reaction based on the sulfide concentration of the standard colorimetric solution;

[0010] S4. Calculate the concentration range of gaseous sulfide in the gas sample to be tested based on the concentration range of sulfide in the solution after the reaction. The calculation formula is:

[0011] Sulfide concentration in the gas sample to be tested = (sulfide concentration in the solution after reaction × volume of the indicator solution containing ferric hydroxide precipitate) / volume of the gas sample to be tested;

[0012] Where, the unit of sulfide concentration in the gas sample to be measured is mg / m 3 ; Sulfide concentration in the solution after the reaction: mg / L; Volume of the indicator solution containing ferric hydroxide precipitation: L; Volume of the gas sample to be tested: m 3 .

[0013] Furthermore, in step S2, the volume of the gas sample to be tested is 0.001-0.008m 3 .

[0014] Furthermore, the gas sample to be tested is a gas with a sulfide concentration ≥ 0 mg / L.

[0015] Furthermore, in step S3, the light source condition during observation is natural light or D65 standard light source; when 5°C ≤ observation temperature ≤ 40°C, the observation time is ≤ 30s; when the observation temperature is < 5°C, the observation time is 40-60s.

[0016] Furthermore, in step S4, the steps for preparing the standard colorimetric solution are as follows:

[0017] (1) Take nine 25 ml colorimetric tubes, add 3 ml of 0.1 wt % ferric chloride solution and 5 ml of 25 wt % ammonia water to each colorimetric tube, and dilute with water to obtain nine 25 ml display solutions containing ferric hydroxide precipitates;

[0018] (2) Sulfide standard gas is introduced into 9 indicator solutions containing ferric hydroxide precipitates at a rate of 0.1 L / min. The aeration time of each indicator solution is 0 s, 10 s, 20 s, 40 s, 50 s, 60 s, 70 s, 80 s, and 100 s, respectively, to obtain standard colorimetric solutions. The color and precipitation state of the standard colorimetric solutions are observed and recorded under natural light or D65 standard light source, and the sulfide concentration in the standard colorimetric solutions is calculated. The sulfide standard gas is a mixture of hydrogen sulfide and nitrogen with a sulfide concentration of 7640 mg / L. The calculation formula for the sulfide concentration in the standard colorimetric solution is:

[0019] Sulfide concentration in the standard colorimetric solution = (H2S concentration in the sulfide standard gas × sulfide standard gas flow rate × sulfide standard gas ventilation time) / volume of the indicator solution containing ferric hydroxide precipitate;

[0020] Wherein, the unit of sulfide concentration in the standard colorimetric solution is mg / L; the unit of H2S concentration in the sulfide standard gas is mg / L; the unit of sulfide standard gas flow rate is mL / min; the unit of sulfide standard gas ventilation time is min; the unit of volume of the indicator solution containing ferric hydroxide precipitate is mL.

[0021] Furthermore, when 5°C ≤ observation temperature ≤ 40°C, the observation time is ≤ 30s; when the observation temperature is < 5°C, the observation time is 40-60s.

[0022] In summary, the present invention has the following beneficial effects:

[0023] The present invention achieves semi-quantitative detection of sulfide by chemically reacting ferric chloride with sulfide in an alkaline environment and based on the precipitation produced by the reaction and the color change presented. It is suitable for on-site rapid detection and determination. The present invention has the following advantages:

[0024] (1) Rapid response: short reaction time, suitable for on-site instant detection, without the need for complex instruments;

[0025] (2) Simple operation: No professional training is required, just compare the colors and perform simple calculations;

[0026] (3) Low cost: The reagents used are low-cost and suitable for large-scale promotion;

[0027] (4) Visual: Concentration can be directly judged by color and precipitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the appearance of the standard colorimetric solution after reaction;

[0029] Figure 2 This is the appearance of the gas sample to be tested in Example 1 after passing through the indicator solution containing iron hydroxide precipitate to react. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] The method for rapidly detecting gaseous sulfide in an alkaline environment of the present invention comprises the following steps:

[0032] S1. Prepare a display solution containing ferric hydroxide precipitate: Take a 25 ml colorimetric tube, add 3 ml of 0.1 wt% ferric chloride solution and 5 ml of 25 wt% ammonia water, dilute with water to obtain 25 ml of a display solution containing ferric hydroxide precipitate;

[0033] S2: Take the gas sample to be tested (gas with sulfide concentration ≥ 0 mg / L) and pass it into the display agent solution containing ferric hydroxide precipitation to react. The volume of the gas sample to be tested is 0.001-0.008m 3 (Ventilation flow rate is controlled at 0.5-1 L / min);

[0034] S3: Observe the color and precipitation state of the reaction solution under natural light or D65 standard light source (when 5°C ≤ observation temperature ≤ 40°C, observation time ≤ 30s; when observation temperature < 5°C, observation time is 40-60s), and compare the solution color and precipitation state with those of the standard colorimetric solution. Determine the concentration range of sulfide in the reaction solution based on the sulfide concentration of the standard colorimetric solution;

[0035] The steps for preparing the standard colorimetric solution are as follows:

[0036] (1) Take nine 25 ml colorimetric tubes, add 3 ml of 0.1 wt % ferric chloride solution and 5 ml of 25 wt % ammonia water to each colorimetric tube, dilute with water, and obtain nine 25 ml developer solutions containing ferric hydroxide precipitate. Each developer solution is designated as sample 1 to sample 9.

[0037] (2) Hydrogen sulfide standard gas (components: H2S+N2, standard value: 0.502% mol / mol; i.e., a mixture of hydrogen sulfide and nitrogen with a hydrogen sulfide concentration of 7640 mg / L) is introduced into 9 indicator solutions containing ferric hydroxide precipitates at a rate of 0.1 mL / min. The aeration time of each indicator solution is 0 s, 10 s, 20 s, 40 s, 50 s, 60 s, 70 s, 80 s, and 100 s, respectively, to obtain a standard colorimetric solution. The color and precipitation state of the standard colorimetric solution are observed and recorded under natural light or D65 standard light source, and the sulfide concentration in the standard colorimetric solution is calculated. The calculation formula for the sulfide concentration in the standard colorimetric solution is:

[0038] It is known that the H2S concentration of the hydrogen sulfide standard gas is 7640 mg / L, the flow rate of the hydrogen sulfide standard gas is 0.1 mL / min, the ventilation time is 0s, 10s, 20s, 40s, 50s, 60s, 70s, 80s, and 100s, and the volume of the display solution containing ferric hydroxide precipitate is 25 mL. The sulfide concentration in the standard colorimetric solution is calculated as shown in Table 1. The calculation formula is:

[0039] Sulfide concentration in the standard colorimetric solution = (H2S concentration in hydrogen sulfide standard gas × hydrogen sulfide standard gas flow rate × hydrogen sulfide standard gas ventilation time) / volume of the indicator solution containing ferric hydroxide precipitate;

[0040] Wherein, the unit of sulfide concentration in the standard colorimetric solution is mg / L; the unit of H2S concentration in the sulfide standard gas is mg / L; the unit of sulfide standard gas flow rate is mL / min; the unit of sulfide standard gas ventilation time is min; the unit of volume of the indicator solution containing ferric hydroxide precipitate is mL.

[0041] Table 1

[0042]

[0043] Observe and record the color of the standard colorimetric solution and the precipitation state under natural light. Figure 1 .

[0044] S4. Calculate the concentration range of gaseous sulfide in the gas sample to be tested based on the concentration range of sulfide in the solution after the reaction. The calculation formula is:

[0045] Sulfide concentration in the gas sample to be tested = (sulfide concentration in the solution after reaction × volume of the indicator solution containing ferric hydroxide precipitate) / volume of the gas sample to be tested;

[0046] Where, the unit of sulfide concentration in the gas sample to be measured is mg / m 3 ; Sulfide concentration in the solution after the reaction unit: mg / L; Volume of the indicator solution containing ferric hydroxide precipitation unit: L; Volume of the gas sample to be tested unit: m3 .

[0047] Example 1

[0048] (1) Preparation of a display solution containing ferric hydroxide precipitate: Take a 25 ml colorimetric tube, add 3 ml of 0.1 wt % ferric chloride solution and 5 ml of 25 wt % ammonia water, and dilute with water to obtain 25 ml of a display solution containing ferric hydroxide precipitate;

[0049] (2) Take the initial non-condensable gas from the conversion condensate treatment section in the water gas synthesis ammonia process and pass it into the indicator solution containing iron hydroxide precipitate at a rate of 0.8 mL / min (ventilation for 5 minutes), that is, pass 0.004 m3 of the gas sample to be tested. 3 ;

[0050] (3) Stop ventilation and observe the color and precipitation of the solution after reaction for 30 seconds under natural light at 24°C. Figure 1 shown; compare it with Figure 2 The solution color and precipitation state were compared to determine that the sulfide concentration in the solution after the reaction was >50.93 mg / L; the hydrogen sulfide concentration in the gas sample to be tested was calculated to be greater than 318.3 mg / m 3 .

[0051] Example 2

[0052] (1) Preparation of a display solution containing ferric hydroxide precipitate: Take a 25 ml colorimetric tube, add 3 ml of 0.1 wt % ferric chloride solution and 5 ml of 25 wt % ammonia water, and dilute with water to obtain 25 ml of a display solution containing ferric hydroxide precipitate;

[0053] (2) Take the gas from the ammonia outlet of the stripping tower in the conversion condensate treatment section of the water gas synthesis ammonia process and pass it into the indicator solution containing iron hydroxide precipitate at a rate of 0.1 mL / min (ventilation for 5 minutes), that is, pass 0.005 m3 of the gas sample to be tested. 3 ;

[0054] (3) Stop ventilation and observe the color and precipitation of the solution after reaction for 30 seconds under natural light at 22°C. Figure 1 By comparing the solution color and precipitation state, it was determined that the sulfide concentration in the solution after the reaction was between 5.09-10.19 mg / L; the hydrogen sulfide concentration in the gas sample to be tested was calculated to be between 25.45-50.95 mg / m 3 .

[0055] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapid detection of gaseous sulfide in an alkaline environment, characterized in that: The following steps are involved: S1. Take a gas washing bottle, add 3 mL of 0.1 wt% ferric chloride solution and 5 mL of 25 wt% ammonia water, dilute with water to obtain 25 mL of a display agent solution containing ferric hydroxide precipitate; S2, taking a gas sample to be tested and passing it into a display agent solution containing ferric hydroxide precipitate to react; S3. Observe the color and precipitation state of the solution after the reaction, and compare the color and precipitation state of the solution with those of a standard colorimetric solution, and determine the concentration range of sulfide in the solution after the reaction based on the sulfide concentration of the standard colorimetric solution; S4. Calculate the concentration range of gaseous sulfide in the gas sample to be tested based on the concentration range of sulfide in the solution after the reaction. The calculation formula is: Sulfide concentration in the gas sample to be tested = (sulfide concentration in the solution after reaction × volume of the indicator solution containing ferric hydroxide precipitate) / volume of the gas sample to be tested; Where, the unit of sulfide concentration in the gas sample to be measured is mg / m 3 ; Sulfide concentration in the solution after the reaction unit: mg / L; Volume of the indicator solution containing ferric hydroxide precipitation unit: L; Volume of the gas sample to be tested unit: m 3 .

2. The method for rapid detection of gaseous sulfide in an alkaline environment according to claim 1, characterized in that: In step S2, the volume of the gas sample to be tested is 0.001-0.008m 3 .

3. The method for rapid detection of gaseous sulfide in an alkaline environment according to claim 1, characterized in that: The gas sample to be tested is a gas with a sulfide concentration ≥ 0 mg / L.

4. The method for rapid detection of gaseous sulfide in an alkaline environment according to claim 1, characterized in that: In step S3, the light source condition during observation is natural light or D65 standard light source; when 5°C ≤ observation temperature ≤ 40°C, the observation time is ≤ 30s; when the observation temperature is less than 5°C, the observation time is 40 to 60s.

5. The method for rapid detection of gaseous sulfide in an alkaline environment according to claim 1, characterized in that: In step S4, the steps for preparing the standard colorimetric solution are as follows: (1) Take nine 25 mL colorimetric tubes, add 3 mL of 0.1 wt% ferric chloride solution and 5 mL of 25 wt% ammonia water to each colorimetric tube, and dilute with water to obtain nine 25 mL display solutions containing ferric hydroxide precipitates; (2) Sulfide standard gas is introduced into 9 indicator solutions containing ferric hydroxide precipitates at a rate of 0.1 L / min. The aeration time of each indicator solution is 0 s, 10 s, 20 s, 40 s, 50 s, 60 s, 70 s, 80 s, and 100 s, respectively, to obtain standard colorimetric solutions. The color and precipitation state of the standard colorimetric solutions are observed and recorded under natural light or D65 standard light source, and the sulfide concentration in the standard colorimetric solutions is calculated. The sulfide standard gas is a mixture of hydrogen sulfide and nitrogen with a sulfide concentration of 7640 mg / L. The calculation formula for the sulfide concentration in the standard colorimetric solution is: Sulfide concentration in the standard colorimetric solution = (H2S concentration in the sulfide standard gas × sulfide standard gas flow rate × sulfide standard gas ventilation time) / volume of the indicator solution containing ferric hydroxide precipitate; Wherein, the unit of sulfide concentration in the standard colorimetric solution is mg / L; the unit of H2S concentration in the sulfide standard gas is mg / L; the unit of sulfide standard gas flow rate is mL / min; the unit of sulfide standard gas ventilation time is min; the unit of volume of the indicator solution containing ferric hydroxide precipitate is mL.

6. The method for rapid detection of gaseous sulfide in an alkaline environment according to claim 5, characterized in that: When the observation temperature is 5℃≤observation temperature≤40℃, the observation time is ≤30s; when the observation temperature is less than 5℃, the observation time is 40~60s.

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