A method for rapid detection of gaseous sulfides in alkaline environments

Abstract

This invention discloses a rapid method for detecting gaseous sulfides in an alkaline environment, belonging to the field of analytical chemistry. The invention includes the following steps: S1, preparing the reaction solution: Take a 25ml colorimetric tube, add 3mL of 0.1wt% ferric chloride solution and 5mL of 25wt% ammonia water, and dilute with water to 25mL to obtain a reaction solution with ferric hydroxide precipitate; S2, pass the gas sample to be tested into the reaction solution to react; S3, observe the color of the reaction solution and the precipitate state; S4, compare with a standard colorimetric solution to determine the concentration range of sulfides in the reaction solution after the reaction; S5, calculate the sulfide concentration in the gas sample to be tested based on the sulfide concentration in the reaction solution. This invention utilizes the chemical reaction between ferric chloride and sulfides in an alkaline environment, and compares the precipitate produced by the reaction and the resulting color change with a standard colorimetric solution to achieve semi-quantitative detection of hydrogen sulfide, suitable for rapid on-site detection and judgment.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and more specifically, to a method for rapid detection of gaseous sulfides in alkaline environments. Background Technology

[0002] In the fields of chemical engineering and environmental protection, sulfides in alkaline waste gas often exist in the form of gaseous H2S. Excessive H2S concentration in waste gas can corrode equipment, affect catalyst activity, and even lead to failure to meet environmental protection standards.

[0003] Currently, methods for detecting hydrogen sulfide include methylene blue spectrophotometry, iodometric titration, lead acetate test paper method, electrochemical sensor method, gas chromatography, and spectrometry. The methylene blue spectrophotometry method involves the reaction of gaseous sulfide with aminodimethylaniline to produce blue methylene blue, which is then quantified by measuring absorbance using a spectrophotometer. This method is cumbersome, time-consuming, and susceptible to interference from reducing agents. The iodometric titration method involves a redox reaction between hydrogen sulfide and iodine, with excess iodine titrated with sodium thiosulfate. The concentration of hydrogen sulfide is calculated based on the amount of iodine consumed. 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 form a black lead sulfide precipitate. The concentration is qualitatively or semi-quantitatively determined by the color change of the test paper. This method is easily affected by humidity and light, and requires stringent storage conditions. The electrochemical sensor method involves a redox reaction of hydrogen sulfide at the sensor electrode, generating a current signal proportional to the concentration. In this method, the electrolyte and electrodes are prone to aging, and changes in humidity can affect stability. Gas chromatography involves separating the sample using gas chromatography and then detecting hydrogen sulfide using FPD and SCD. This method requires specialized operation and maintenance, complex sample pretreatment, and a long analysis cycle, making it unsuitable for rapid on-site operation. Spectroscopic methods involve reacting hydrogen sulfide with a colorimetric reagent to form a colored compound, and then measuring the absorbance. This method is costly, cumbersome, and uses unstable reagents. These methods, designed for the direct determination of sulfides in alkaline gases, each suffers from limitations such as inapplicability, difficulty in eliminating interference, high cost, and low efficiency. Therefore, there is an urgent need to develop a novel detection method that requires no acidification pretreatment, is resistant to alkaline interference, and is easy to operate, filling the technological gap in sulfide detection in alkaline environments. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for rapid detection of gaseous sulfides in an alkaline environment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for rapid detection of gaseous sulfides in an alkaline environment includes 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 indicator solution containing ferric hydroxide precipitate;

[0008] S2. Take the gas sample to be tested and pass it into the indicator solution containing ferric hydroxide precipitate to carry out the reaction;

[0009] S3. Observe the color and precipitation state of the solution after the reaction, and compare it with the standard colorimetric solution. 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 sulfides in the gas sample based on the concentration range of sulfides in the solution after the reaction. The calculation formula is as follows:

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

[0012] In the formula, the concentration of sulfides in the gas sample to be tested is expressed in mg / m³. 3 ; Sulfide concentration in the solution after reaction (mg / L); Volume of the indicator solution containing ferric hydroxide precipitate (L); Sample volume of the gas to be tested (m³) 3 .

[0013] Furthermore, in step S2, the volume of the gas sample to be tested is 0.001-0.008 m³. 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 conditions during observation are natural light or D65 standard light source; when 5℃≤observation temperature≤40℃, the observation time is ≤30s, and when the observation temperature<5℃, the observation time is 40~60s.

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

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

[0018] (2) Sulfide standard gas was passed into nine indicator solutions containing ferric hydroxide precipitate at a rate of 0.1 L / min. The gas passage times for each indicator solution were 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 were observed and recorded under natural light or a D65 standard light source, and the sulfide concentration in the standard colorimetric solutions was calculated. The sulfide standard gas was a mixture of hydrogen sulfide and nitrogen with a sulfide concentration of 7640 mg / L. The formula for calculating the sulfide concentration in the standard colorimetric solutions is:

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

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

[0021] Furthermore, when 5℃≤observation temperature≤40℃, the observation time is ≤30s, and when the observation temperature<5℃, the observation time is 40~60s.

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

[0023] This invention utilizes the chemical reaction between ferric chloride and sulfides in an alkaline environment. Based on the precipitate produced and the resulting color change, it achieves semi-quantitative detection of sulfides, suitable for rapid on-site detection and determination. This invention has the following advantages:

[0024] (1) Rapid response: Short reaction time, suitable for on-site instant detection, no need for complex instruments;

[0025] (2) Simple operation: No professional training is required; simply 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) Visually intuitive: The concentration can be directly judged by color and sediment. Attached Figure Description

[0028] Figure 1 This is a diagram showing the appearance of the standard colorimetric solution after the reaction.

[0029] Figure 2 This is an image showing the appearance of the gas sample to be tested after it has been reacted with a solution of indicator containing ferric hydroxide precipitate in Example 1. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The method for rapid detection of gaseous sulfides in an alkaline environment according to the present invention includes the following steps:

[0032] S1. Preparation of indicator solution containing ferric hydroxide precipitate: 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 indicator solution containing ferric hydroxide precipitate;

[0033] S2: Take the gas sample to be tested (a gas with a sulfide concentration ≥ 0 mg / L) and pass it into the indicator solution containing ferric hydroxide precipitate to carry out the reaction. The volume of the gas sample passed in is 0.001-0.008 m³. 3 (The airflow rate is controlled at 0.5-1 L / min);

[0034] S3: Observe the color and precipitation state of the solution after the reaction under natural light or D65 standard light source (when 5℃≤observation temperature≤40℃, the observation time ≤30s; when the observation temperature<5℃, the observation time is 40~60s), and compare the solution color and precipitation state with the standard colorimetric solution. Determine the concentration range of sulfide in the solution after the reaction 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 9 colorimetric tubes of 25 ml each, 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 to obtain 9 display solutions containing ferric hydroxide precipitate, each with a volume of 25 mL. Each display solution is recorded 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) was passed into nine indicator solutions containing ferric hydroxide precipitate at a rate of 0.1 mL / min. The gas passage times for each indicator solution were 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 were observed and recorded under natural light or a D65 standard light source, and the sulfide concentration in the standard colorimetric solutions was calculated. The formula for calculating the sulfide concentration in the standard colorimetric solutions is:

[0038] Given 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, and the aeration times are 0 s, 10 s, 20 s, 40 s, 50 s, 60 s, 70 s, 80 s, and 100 s respectively, and the volume of the indicator solution containing ferric hydroxide precipitate is 25 mL, calculate the sulfide concentration in the standard colorimetric solution as shown in Table 1. The calculation formula is:

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

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

[0041] Table 1

[0042]

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

[0044] S4. Calculate the concentration range of gaseous sulfides in the gas sample based on the concentration range of sulfides in the solution after the reaction. The calculation formula is as follows:

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

[0046] In the formula, the concentration of sulfides in the gas sample to be tested is expressed in mg / m³. 3 ; Sulfide concentration in the solution after reaction (mg / L); Volume of the indicator solution containing ferric hydroxide precipitate (L); Sample volume of the gas to be tested (m³)3 .

[0047] Example 1

[0048] (1) Preparation of indicator solution containing ferric hydroxide precipitate: 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 indicator solution containing ferric hydroxide precipitate;

[0049] (2) The initial non-condensable gas from the shift condensate treatment section of the water gas to ammonia synthesis process is introduced into the indicator solution containing ferric hydroxide precipitate at a rate of 0.8 mL / min (for 5 min), i.e., 0.004 mL of the gas sample to be tested is introduced. 3 ;

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

[0051] Example 2

[0052] (1) Preparation of indicator solution containing ferric hydroxide precipitate: 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 indicator solution containing ferric hydroxide precipitate;

[0053] (2) In the water gas to ammonia synthesis process, the gas from the ammonia outlet of the stripping tower in the shift condensate treatment section is introduced into a solution containing ferric hydroxide precipitate at a rate of 0.1 mL / min (for 5 min), i.e., 0.005 mL of the gas sample to be tested is introduced. 3 ;

[0054] (3) Stop ventilation, observe the color of the solution and the state of the precipitate after the reaction for 30 seconds at 22°C under natural light; then combine it with… Figure 1 By comparing the solution color and precipitation state, the sulfide concentration in the solution after the reaction was determined to be between 5.09 and 10.19 mg / L; the calculated hydrogen sulfide concentration in the gas sample was between 25.45 and 50.95 mg / L. 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 embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing 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 sulfides in an alkaline environment, characterized in that, Includes the following steps: 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 indicator solution containing ferric hydroxide precipitate; S2. Take the gas sample to be tested and pass it into the indicator solution containing ferric hydroxide precipitate to carry out the reaction; S3. Observe the color and precipitation state of the solution after the reaction, and compare it with the standard colorimetric solution. 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 sulfides in the gas sample based on the concentration range of sulfides in the solution after the reaction. The calculation formula is as follows: Sulfide concentration in the gas sample to be tested = (sulfide concentration in the solution after reaction × volume of indicator solution containing ferric hydroxide precipitate) / volume of gas sample to be tested passed through; In the formula, the concentration of sulfides in the gas sample to be tested is expressed in mg / m³. 3 ; Sulfide concentration in the solution after reaction (mg / L); Volume of the indicator solution containing ferric hydroxide precipitate (L); Sample volume of the gas to be tested (m³) 3 ; The sulfide measured was hydrogen sulfide.

2. The method for rapid detection of gaseous sulfides in an alkaline environment according to claim 1, characterized in that, In step S2, the volume of the gas sample to be tested is 0.001-0.008 m³. 3 .

3. The method for rapid detection of gaseous sulfides 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 sulfides in an alkaline environment according to claim 1, characterized in that, In step S3, the light source conditions for observation are natural light or D65 standard light source; when 5℃≤observation temperature≤40℃, the observation time is ≤30s, and when the observation temperature<5℃, the observation time is 40~60s.

5. The method for rapid detection of gaseous sulfides in an alkaline environment according to claim 1, characterized in that, In step S4, the preparation steps for 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, dilute with water to obtain nine display solutions containing ferric hydroxide precipitate, each with a volume of 25 mL. (2) Sulfide standard gas was introduced into nine indicator solutions containing ferric hydroxide precipitate at a rate of 0.1 L / min. The gas introduction time for each indicator solution was 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 were observed and recorded under natural light or a D65 standard light source, and the sulfide concentration in the standard colorimetric solutions was calculated. The sulfide standard gas was a mixture of hydrogen sulfide and nitrogen with a sulfide concentration of 7640 mg / L. The formula for calculating the sulfide concentration in the standard colorimetric solutions is: Sulfide concentration in standard colorimetric solution = (H2S concentration in sulfide standard gas × sulfide standard gas flow rate × sulfide standard gas aeration time) / volume of indicator solution containing ferric hydroxide precipitate; In the formula, the concentration of sulfide in the standard colorimetric solution is in mg / L; the concentration of H2S in the sulfide standard gas is in mg / L; the flow rate of the sulfide standard gas is in mL / min; the venting time of the sulfide standard gas is in min; and the volume of the indicator solution containing ferric hydroxide precipitate is in mL.

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

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