CN111610183A - Semi-quantitative detection method for total residual chlorine in wastewater - Google Patents
Semi-quantitative detection method for total residual chlorine in wastewater Download PDFInfo
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Abstract
The invention discloses a semi-quantitative detection method of total residual chlorine in wastewater, which comprises the steps of filling quantitative acetate buffer solution, starch solution and sodium thiosulfate standard solution into a container to prepare a prefabricated tube for later use, weighing quantitative potassium iodide solid, sealing and storing in a dark place for later use; and mixing the collected water sample with a potassium iodide solid, an acetate buffer solution, a starch solution and a sodium thiosulfate standard solution, and judging whether the concentration of the total residual chlorine in the water sample reaches the standard or not by observing whether the mixed solution is colored or not. The semi-quantitative detection method for the total residual chlorine in the wastewater provided by the invention is simple, convenient and quick to operate, and has intuitive and obvious reaction phenomenon; the prefabricated pipe is easy to store and convenient to carry, and is suitable for monitoring the content of total residual chlorine in a water sample on site.
Description
Technical Field
The invention belongs to the technical field of wastewater monitoring, and particularly relates to a semi-quantitative detection method for total residual chlorine in wastewater.
Background
In order to ensure that tap water meets the national safety and sanitation requirements and avoid the occurrence of waterborne infectious diseases, the tap water needs to be added with a disinfectant in the water purification process to kill pathogenic microorganisms in the water. Because of the high performance-to-cost ratio of chlorine, sodium hypochlorite is widely used as a disinfectant in the domestic water treatment industry.
After the wastewater is disinfected, sodium hypochlorite partially remains in the water, and whether the wastewater is qualified or not is judged by detecting the content of total residual chlorine in the water. The total residual chlorine is also called total chlorine, the total residual chlorine includes free residual chlorine and combined residual chlorine, the free residual chlorine includes HOCl and OCl-Etc.; the combined residual chlorine comprising NH2C1，NHCl2， NCl3And other chloramines; if the total residual chlorine content in the wastewater is lower than 6.5mg/L, pathogenic microorganisms cannot be effectively killed, and along with the discharge of the wastewater, the pathogenic microorganisms can also continuously swim in the wastewater and continuously diffuse to cause the pollution of other water bodies. Therefore, effective control and detection of total residual chlorine content is critical in water treatment.
At present, the total residual chlorine in the wastewater is mostly determined by an iodometry method, and a water sample needs to be brought into a laboratory for detection. In an epidemic situation, key protection places such as hospitals and the like need to be disinfected frequently by adopting a chlorine-containing disinfectant, and a disinfected water body needs to be detected so as to ensure that the chlorine content is not lower than a safety standard. If the water sample after disinfection is brought into a laboratory for detection, the carrying and the transmission of highly pathogenic infectious viruses can be caused in the detection process and the waste liquid treatment link, and meanwhile, the disinfection and protection link can lead the whole detection process to be used for a long time, thus leading to low detection efficiency. Some commercial test paper can also measure the total residual chlorine in water, but the test paper method is not supported by a standard method at present, a comparison and verification experiment with other principle standard methods needs to be carried out, and whether the characteristic indexes of the method, such as accuracy, deviation and the like, meet the quantitative requirements or not needs to be further confirmed.
Disclosure of Invention
The invention aims to provide a semi-quantitative detection method for total residual chlorine in wastewater, which aims to solve the problems of long time consumption and low detection efficiency in the detection process in the prior art.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: a semi-quantitative detection method of total residual chlorine in wastewater adopts an iodometry method, and comprises placing acetate buffer solution, starch solution and sodium thiosulfate standard solution into a container to prepare a prefabricated tube for later use, and sealing potassium iodide solid for keeping in the dark for later use; and mixing the collected water sample with a potassium iodide solid, an acetate buffer solution, a starch solution and a sodium thiosulfate standard solution, and judging the concentration of the total residual chlorine in the water sample by observing whether the mixed solution is developed.
The semi-quantitative detection method for the total residual chlorine in the wastewater specifically comprises the following steps:
s1, manufacturing a prefabricated pipe: preparing acetate buffer solution, putting a proper amount of the acetate buffer solution into a container to prepare a prefabricated pipe B, and sealing and storing the prefabricated pipe B; preparing a starch solution, putting a proper amount of the starch solution into a container to prepare a prefabricated pipe C, and sealing and storing the prefabricated pipe C; preparing a sodium thiosulfate standard solution, putting a proper amount of the sodium thiosulfate standard solution into a container to prepare a prefabricated pipe D, and sealing and storing the prefabricated pipe D; simultaneously weighing a proper amount of potassium iodide solid, sealing and storing in dark place;
s2, collecting a water sample on site, adding potassium iodide solid into a colorimetric tube to prepare a prefabricated tube A, and adding the water sample and acetate buffer solution in the prefabricated tube B into the prefabricated tube A;
s3, adding the starch solution in the prefabricated pipe C into the prefabricated pipe A, wherein the solution is blue, adding the sodium thiosulfate standard solution in the prefabricated pipe D into the prefabricated pipe A, observing the solution in the prefabricated pipe A, and if the solution in the prefabricated pipe A is still blue, the concentration of the total residual chlorine in the water sample is more than or equal to 6.5 mg/L; if the blue color of the solution in the prefabricated pipe A fades, and the concentration of the total residual chlorine in the water sample is less than 6.5mg/L, the chlorine-containing disinfectant is continuously added into the wastewater, and the operation steps are repeated until the solution in the prefabricated pipe A is still blue after detection.
Preferably, the prefabricated tube a is a transparent colorimetric tube, and the prefabricated tube B, the prefabricated tube C and the prefabricated tube D are brown containers.
Wherein when the concentration of the sodium thiosulfate standard solution is in the range of 0.0090-0.0115 mmol/L, the volume of the solution corresponding to the sodium thiosulfate standard solution is in the range of 1.59-2.03 mL
The invention has the following beneficial effects:
according to the semi-quantitative detection method for the total residual chlorine in the wastewater, provided by the invention, acetate buffer solution, starch solution and sodium thiosulfate standard solution are prepared into prefabricated tubes respectively in advance, quantitative potassium iodide solid is weighed and stored in a sealed and light-proof manner for later use, and the reagents can be carried to the site to perform a color reaction with an acquired water sample, so that whether the total residual chlorine content in the wastewater reaches the standard or not is judged, the purpose of rapidly detecting the residual chlorine content in the wastewater is realized, the semi-quantitative detection method is suitable for site detection under emergency or emergency conditions, and the diffusion and the propagation of pathogenic microorganisms in the water quality detection process can be effectively controlled and avoided.
The semi-quantitative detection method for total residual chlorine in water provided by the invention has the advantages that the prefabricated pipe is convenient to carry, the cold chain storage and transportation are easy, the operation is simple and rapid, the time consumption is short, the detection efficiency is high, the semi-quantitative result is visual and reliable, and the method is suitable for being used on site.
Detailed Description
The semi-quantitative detection method for total residual chlorine in water provided by the invention is further described in detail by combining the examples.
Under the condition that the pH value is 3.5-4.2, reacting potassium iodide with an acetate buffer solution to generate hydrogen iodide, reacting elemental chlorine, hypochlorous acid, hypochlorite, chloramine and the hydrogen iodide to generate an iodine elemental substance, adding a starch solution into the solution generating the iodine elemental substance to change the solution into blue, titrating the blue solution by using a sodium thiosulfate standard solution, and if the blue still exists, indicating that the concentration of total residual chlorine in a water sample is greater than or equal to 6.5 mg/L; if the blue color disappears, the chlorine content in the water sample is lower than 6.5 mg/L.
Examples
A semi-quantitative detection method of total residual chlorine in wastewater adopts an iodometry method, and specifically comprises the following steps:
s1: preparing a prefabricated tube, preparing acetate buffer solution with pH of 4, and filling 5.0mL of the acetate buffer solution into a colorimetric tube to prepare a prefabricated tube B; preparing a starch solution with the mass concentration of 1%, putting 1.0mL of the starch solution into a colorimetric tube to prepare a prefabricated tube C, preparing a sodium thiosulfate standard solution, and putting the solution into the colorimetric tube to prepare a prefabricated tube D; and weighing 0.5g of potassium iodide solid, and storing in a sealed bag in a dark place, or wrapping the potassium iodide solid by weighing paper and storing in a dark place.
Acetate buffer solution preparation: 146g of anhydrous sodium acetate was weighed out and dissolved in experimental water, 457mL of glacial acetic acid was added, and the solution was diluted to 1000mL with water to obtain a pH 4 acetate buffer solution. Prefabricated tube B was prepared by placing 5mL of acetate buffer solution in the first brown cuvette. The experimental water in this embodiment is deionized water containing no nitrite, high iron, and manganese, or may be redistilled water, and the experimental water is only usable after passing the test. In this embodiment, an acetate buffer solution with a pH of 4 is added to the experimental water, so that the reaction of nitrite, high iron, and manganese in the water with potassium iodide under an acidic condition can be reduced, and the interference on the detection can be avoided.
Preparing a starch solution with the mass concentration of 1%: weighing 1g of starch solid, dissolving the starch solid in 100mL of boiling experimental water, cooling, fixing the volume to 100mL, and uniformly stirring to form a starch solution with the mass concentration of 1%; 1mL of the starch solution was placed in a second brown cuvette to form a pre-fabricated tube C.
Preparing a 0.05mol/L sodium thiosulfate standard solution to be calibrated: 12.5g of sodium thiosulfate (Na) are weighed out first2S2O3·5H2O) dissolving the solid in boiled and cooled water, and diluting to 1000 mL; 0.2g of anhydrous sodium carbonate is added, and the solid is dissolved by stirring to obtain a standard sodium thiosulfate solution with the concentration of about 0.05 mol/L. With 1/6K at 0.025mol/L2Cr2O7And carrying out specific concentration calibration on the sodium thiosulfate standard solution to be calibrated. In an alternative embodiment, a calibrated 0.05mol/L standard solution of sodium thiosulfate is also commercially available. In a specific embodiment, the calibration concentration of the sodium thiosulfate standard solution to be calibrated is 0.05 mol/L. 50mL of the calibrated 0.05mol/L sodium thiosulfate standard solution is measured, boiled and cooled experimental water is added into the solution, and the solution is diluted to 250mL to obtain the 0.01mol/L sodium thiosulfate standard solution. A prefabricated tube D was prepared by placing 1.83mL of 0.01mol/L sodium thiosulfate standard solution in a third brown colorimetric tube. In other examples, the sodium thiosulfate standard solution was calibrated differently and used for experimentsThe solutions were varied, and specifically the desired solution volumes for the different concentrations of the sodium thiosulfate standard solution are shown in table 1.
TABLE 1
| Sodium thiosulfate concentration (mmol/L) | Amount of sodium thiosulfate (mL) |
| 0.0115 | 1.59 |
| 0.0110 | 1.66 |
| 0.0105 | 1.74 |
| 0.0095 | 1.92 |
| 0.0092 | 1.99 |
| 0.0090 | 2.03 |
The prefabricated pipe B, the prefabricated pipe C and the prefabricated pipe D are preferably brown containers to ensure light-proof storage and cold-chain transportation and storage.
S2: and (4) placing the prefabricated pipe and the potassium iodide prepared in the step (S1) in a portable incubator to bring the prefabricated pipe and the potassium iodide to a water sample collection site. Measuring 100mL of a water sample to be detected through a measuring cylinder, and pouring potassium iodide solid into a transparent colorimetric tube to prepare a prefabricated tube A; and sequentially adding the water sample and the acetate buffer solution in the prefabricated pipe B into the prefabricated pipe A, shaking up to enable potassium iodide and the acetate buffer solution to react to generate hydrogen iodide, and enabling the generated hydrogen iodide to perform redox reaction with chlorine in the water sample to generate an iodine simple substance.
S3: and adding the starch solution in the prefabricated pipe C into the prefabricated pipe A, changing the solution into blue, shaking up, adding the sodium thiosulfate standard solution in the prefabricated pipe D into the prefabricated pipe A, shaking up, observing the solution in the prefabricated pipe A, and if the solution in the prefabricated pipe A is still blue, enabling the concentration of the total residual chlorine in the water sample to be more than or equal to 6.5mg/L, namely meeting the requirement. If the blue color of the solution in the prefabricated pipe A is completely faded, the concentration of the total residual chlorine in the water sample is less than 6.5mg/L, the disinfection effect is not up to the standard, sodium hypochlorite needs to be continuously added into the wastewater, and the operation steps are repeated until the solution in the prefabricated pipe A is still blue after detection.
In the semi-quantitative detection method for total residual chlorine in wastewater provided by the embodiment, acetate buffer solution, starch solution and sodium thiosulfate standard solution are respectively prepared into prefabricated tubes in advance, and quantitative potassium iodide is weighed and sealed and stored in a dark place; the device can be carried to the site and performs color reaction with the collected water sample, thereby judging whether the content of the total residual chlorine in the wastewater meets the requirement or not, realizing the purpose of rapidly detecting the content of the residual chlorine in the wastewater, being suitable for the site detection under emergency or emergency, and effectively controlling and avoiding the diffusion and the propagation of pathogenic microorganisms in the water quality detection process.
The semi-quantitative detection method for the total residual chlorine in the wastewater provided by the invention has the advantages that the prefabricated pipe is convenient to carry, the cold chain storage and transportation are easy, the operation is simple and rapid, the time consumption is short, the detection efficiency is high, the semi-quantitative result is visual and reliable, and the method is suitable for being used on site.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, or direct or indirect applications in other related fields, which are made by the present specification, are included in the scope of the present invention.
Claims (4)
1. A semi-quantitative detection method of total residual chlorine in wastewater adopts an iodometry method, and is characterized in that: putting the acetate buffer solution, the starch solution and the sodium thiosulfate standard solution into a container to prepare a prefabricated tube for later use, and sealing the potassium iodide solid for later use in a dark place; and mixing the water sample with a potassium iodide solid, an acetate buffer solution, a starch solution and a sodium thiosulfate standard solution, and judging whether the concentration of the total residual chlorine in the water sample reaches the standard or not by observing whether the mixed solution is colored or not.
2. The semi-quantitative detection method of total residual chlorine in wastewater according to claim 1, characterized in that: the method specifically comprises the following steps:
s1, manufacturing a prefabricated pipe: preparing acetate buffer solution, putting a proper amount of the acetate buffer solution into a container to prepare a prefabricated pipe B, and sealing and storing the prefabricated pipe B; preparing a starch solution, putting a proper amount of the starch solution into a container to prepare a prefabricated pipe C, and sealing and storing the prefabricated pipe C; preparing a sodium thiosulfate standard solution, putting a proper amount of the sodium thiosulfate standard solution into a container to prepare a prefabricated pipe D, and sealing and storing the prefabricated pipe D; simultaneously weighing a proper amount of potassium iodide solid, sealing and storing in dark place;
s2, collecting a water sample on site, adding potassium iodide solid into a colorimetric tube to prepare a prefabricated tube A, and adding the water sample and acetate buffer solution in the prefabricated tube B into the prefabricated tube A;
s3, adding the starch solution in the prefabricated pipe C into the prefabricated pipe A, changing the solution into blue, adding the sodium thiosulfate standard solution in the prefabricated pipe D into the prefabricated pipe A, observing the solution in the prefabricated pipe A, and if the solution in the prefabricated pipe A is blue, enabling the concentration of the total residual chlorine in the water sample to be larger than or equal to 6.5 mg/L; if the blue color of the solution in the prefabricated pipe A fades, and the concentration of the total residual chlorine in the water sample is less than 6.5mg/L, continuing to add the chlorine-containing disinfectant into the wastewater, and repeating the operation steps until the solution in the prefabricated pipe A is blue after detection.
3. The semi-quantitative determination method for total residual chlorine in wastewater according to claim 2, wherein the prefabricated tube A is a transparent colorimetric tube, and the prefabricated tube B, the prefabricated tube C and the prefabricated tube D are brown containers.
4. The semi-quantitative detection method for the total residual chlorine in the wastewater according to claim 1, wherein when the concentration of the sodium thiosulfate standard solution is in the range of 0.0090-0.0115 mmol/L, the solution volume corresponding to the sodium thiosulfate standard solution is in the range of 1.59-2.03 mL.
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