Method and device for detecting ammonia nitrogen in water through flow injection conductivity

Abstract

The invention relates to a method for detecting ammonia nitrogen in water by flow injection conductance, which comprises the following steps: automatically inputting a detection sample in a flow injection mode, pumping the input detection sample, a sodium thiosulfate solution and a sodium hydroxide solution, mixing to form a mixed solution, carrying out online distillation on the mixed solution to extract ammonia gas and water vapor mixed gas, and detecting the ammonia nitrogen in the water by flow injection conductance. The method comprises the following steps: performing online condensation on the extracted mixed gas of ammonia gas and water vapor to form an ammonia-containing aqueous solution, pumping the ammonia-containing aqueous solution, performing degassing treatment, and detecting the conductivity of the degassed ammonia-containing aqueous solution through a conductivity detector, so that the whole process from sample introduction to result output almost does not need manual intervention, thereby greatly reducing personal errors and improving the detection accuracy. And the working efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of water quality detection, and specifically to the technical field of a method and device for flow injection conductivity detection of ammonia nitrogen in water. Background Art

[0002] With the growth of environmental monitoring needs and the development of technology, it is becoming increasingly important to quickly, accurately and efficiently determine the ammonia nitrogen content in water. As one of the water quality indicators, the excessive presence of ammonia nitrogen not only affects the ecological balance of the water body, but may also cause drinking water safety problems.

[0003] Traditional ammonia nitrogen detection methods, such as Nessler's reagent colorimetric method, are widely used due to their simplicity and low cost, but they have disadvantages such as complex operation, long time consumption, high reagent consumption, and the need for professional operation. In addition, the sensitivity and accuracy of this method may be limited due to the influence of color interference and sample matrix effect.

[0004] In response to this, in the field of water quality testing, there is a demand for a simplified process for efficient and accurate testing of ammonia nitrogen. Summary of the invention

[0005] In response to the above problems, the present application proposes a method and device for flow injection conductivity detection of ammonia nitrogen in water, which utilizes the properties of ammonia molecules such as volatility, solubility in water and conductivity, aiming to improve detection efficiency and accuracy while simplifying the operation process.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application proposes a method for detecting ammonia nitrogen in water by flow injection conductivity, comprising step S1: automatically inputting a test sample by flow injection;

[0008] Step S2: mixing the input test sample with the sodium thiosulfate solution and the sodium hydroxide solution by pumping to form a mixed solution;

[0009] Step S3: performing online distillation on the mixed solution to extract ammonia and water vapor mixed gas;

[0010] Step S4: online condensing the extracted mixed gas of ammonia and water vapor to form an ammonia-containing aqueous solution;

[0011] Step S5: degassing the aqueous ammonia solution after pumping;

[0012] Step S6: The conductivity of the degassed ammonia-containing aqueous solution is detected by a conductivity detector.

[0013] Thus, based on the principle of flow injection analysis (FIA), the present application mixes the test sample with sodium thiosulfate solution and sodium hydroxide solution and then performs online distillation, online condensation, degassing, etc., and utilizes the characteristics of ammonia molecules such as volatility, solubility in water and conductivity to achieve accurate determination of ammonia nitrogen concentration. The conductivity detector can detect changes in extremely low concentrations of ammonia nitrogen and provide higher measurement accuracy.

[0014] Compared with traditional methods, this application provides a higher degree of automation, and the entire process from sample injection to result output requires almost no human intervention, which greatly reduces human errors and improves work efficiency. At the same time, the continuous flow property allows sample analysis to be completed in a short time, which is suitable for rapid screening of large batches of samples, as well as real-time online monitoring in the environment (such as rivers, reservoirs and other water bodies) or production (such as drinking water plants, sewage plants, beverage plants, etc.).

[0015] At the same time, the experimental process is simplified, the professional skill requirements for operators are lowered, the use of chemical reagents is reduced, and waste generation is reduced, which is in line with the principles of green chemistry.

[0016] In some possible implementations, the method further includes step S7: transmitting the detected conductivity to a data processing workstation, and calculating the ammonia nitrogen content in the test sample through an algorithm.

[0017] In some possible implementations, the pumping method is a peristaltic pump, which pushes the fluid by squeezing a hose rather than directly contacting the liquid, thereby avoiding contamination of the fluid and ensuring the accuracy of high-purity chemical analysis.

[0018] In a preferred embodiment, the pumping of the test sample and the sodium thiosulfate solution and the sodium hydroxide solution in step S2 and the pumping of the ammonia-containing aqueous solution in step S5 use the same peristaltic pump.

[0019] In this way, the number of devices is reduced, making the entire detection process more compact and efficient, reducing complexity and facilitating installation and maintenance. At the same time, such an integrated design also reduces the operational errors that may be introduced by using multiple pumps, further improving the reliability and consistency of the measurement results.

[0020] On the second aspect, the present application also proposes a device for flow injection conductivity detection of ammonia nitrogen in water, including a mixing device for mixing a test sample and a sodium thiosulfate solution and a sodium hydroxide solution, an online distillation device for distilling the mixed solution, an online condensation device for condensing the distilled ammonia and water vapor mixed gas, a degassing tube for degassing the ammonia-containing aqueous solution produced by condensation, and a conductivity detector for detecting the conductivity of the degassed ammonia-containing aqueous solution.

[0021] In some possible implementations, a data processing workstation is also included for calculating the ammonia nitrogen content in the test sample using an algorithm based on the detected conductivity.

[0022] In some possible implementations, a peristaltic pump for transporting the test sample, the sodium thiosulfate solution, the sodium hydroxide solution, and the condensed ammonia solution is also included.

[0023] In a preferred embodiment, the number of the peristaltic pump is one, which can simultaneously transport the test sample, sodium thiosulfate solution, sodium hydroxide solution, and condensed ammonia-containing aqueous solution.

[0024] In some possible implementations, the mixing device includes a tee for collecting the test sample, the sodium thiosulfate solution, and the sodium hydroxide solution, and a surrounding reactor disposed at the rear end of the tee.

[0025] In some possible implementations, a waste liquid bottle for recovering waste liquid after online distillation and conductivity detection is also included. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a device for flow injection conductivity detection of ammonia nitrogen in water according to the present application;

[0027] Figure 2 This is a detection flow chart of ammonia nitrogen in water by flow injection conductivity detection in the present application. DETAILED DESCRIPTION

[0028] The following examples further illustrate the features of the present application and other related features to facilitate understanding by technicians in the same industry:

[0029] First, the traditional ammonia nitrogen detection process requires manual intervention, which requires high professional skills of operators and a high probability of error. At the same time, chemical waste is generated because chemical reagents are used.

[0030] For this problem, a method that can be considered is to use a water ammonia nitrogen detection system based on the principle of flow injection analysis (FIA) combined with conductivity detection. The premise for its realization is that ammonia molecules are volatile, soluble in water, and have electrical conductivity.

[0031] Please refer to Figure 1 and Figure 2 The following is a detailed description of the detection method and the equipment used with detailed process steps.

[0032] First, in step S1, the test sample is automatically input by flow injection, and the test sample can be an online water quality test sample in the fields of water supply and drainage, environment, food, etc. In step S2, the test sample input is pumped with the sodium thiosulfate solution and the sodium hydroxide solution to form a mixed solution. The sodium thiosulfate solution and the sodium hydroxide solution can be provided by a dedicated solution bottle, or by other dedicated equipment, which is not limited.

[0033] Specifically, the mixing device can select a tee for collecting the test sample and the sodium thiosulfate solution and the sodium hydroxide solution and a surrounding reactor arranged at the rear end of the tee. The tee and the surrounding reactor arranged at the rear end of the tee are used to fully mix the water sample with the sodium thiosulfate solution and the sodium hydroxide solution and cause a chemical reaction. It is preferred to first mix with the sodium thiosulfate solution through the tee and then mix with the sodium hydroxide solution.

[0034] Sodium thiosulfate can remove the interference of oxidants in water (such as chlorine, sodium hypochlorite, etc.) on detection, and react with chloramines (including monochloramine, dichloramine, trichloramine, etc.) to generate ammonium ions (NH4+), and the original ammonium ions (NH4+) in the water sample will be converted into ammonia molecules (NH3) under alkaline conditions. Since ammonia is volatile, ammonia will escape from the solution in the subsequent online distillation process.

[0035] The reaction formula is as follows: Taking the reaction of monochloramine and sodium thiosulfate, ammonium ions will be converted into ammonia molecules under alkaline conditions:

[0036] 4NH2Cl+S2O32-+5H2O→4NH4++4Cl-+2SO42-+2H+;

[0037] NH4++OH-→NH3+H2O.

[0038] The above reaction takes place under alkaline conditions, where sodium hydroxide provides the necessary alkalinity to promote the reaction. Since ammonia is a volatile compound, it easily escapes from the solution under such conditions.

[0039] Furthermore, the pumping method adopts a peristaltic pump. The peristaltic pump pushes the fluid by squeezing the hose instead of directly contacting the liquid, thus avoiding contamination of the fluid and ensuring the accuracy of high-purity chemical analysis. And the flow rate can be easily changed by adjusting the speed, which helps to maintain the consistency and reproducibility of experimental conditions.

[0040] Since the fluid only contacts the hose, the peristaltic pump is easy to clean and maintain. At the same time, the hose material used usually has good chemical compatibility and can resist corrosion from various chemicals. It is suitable for handling different types of solutions, which means that different test samples can be tested.

[0041] Furthermore, it is preferred to use the same peristaltic pump for pumping. In this way, the number of equipment is reduced, making the entire detection process more compact and efficient, and reducing complexity, making installation and maintenance easier. At the same time, such an integrated design also reduces the operational errors that may be introduced by using multiple pumps, further improving the reliability and consistency of the measurement results.

[0042] Further, in step S3, the mixed solution is distilled online in an online distillation device to separate ammonia molecules and part of water vapor from the water sample. The main products of online distillation are ammonia (NH3) and water vapor, which are formed by the volatilization of ammonia molecules (NH3) after the test sample reacts with the sodium thiosulfate solution and the sodium hydroxide solution.

[0043] The online distillation device may be a device using a heating element or a heat exchanger, and may also include a temperature control unit, a gas-liquid separation device, etc., which will not be described in detail. The ammonia (NH3) and water vapor after online distillation are then introduced into the online condensation device, and the waste liquid 1 generated is recovered into the waste liquid bottle.

[0044] Further, step S4 ammonia (NH3) and water vapor are introduced into an online condensing device to form an ammonia-containing aqueous solution. The online condensing device can adopt a cooling coil, a heat exchanger or a cooling jacket using a circulating coolant. The cooling medium can be cold water, an ice-water mixture or a refrigerant, and the purpose is to quickly reduce the gas temperature and promote ammonia (NH3) and water vapor to condense into liquid. In the whole process, by optimizing the condensation conditions (such as temperature, pressure and gas flow rate), it is possible to ensure that ammonia is efficiently recovered, thereby improving the accuracy and reliability of the final measurement result. Its purpose is mainly to form an ammonia-containing aqueous solution that is easy to detect, and the specific device principle form is not described in detail.

[0045] After condensation, bubbles or dissolved gases will remain, which need to be degassed. Specifically, a degassing tube can be used for degassing. The specific degassing method can be selected by the conventional technical means in the industry, which will not be described in detail. The purpose is to effectively remove air bubbles in the sample, thereby improving the data quality and stability of the entire analysis process.

[0046] When the ammonia-containing aqueous solution is transported to the degassing pipe, it is preferably transported by the peristaltic pump as described above. The same peristaltic pump is used for transport as described above, which will not be described in detail here.

[0047] After the above treatment, the conductivity of the ammonia-containing aqueous solution is detected by a conductivity detector. Conductivity detector (Conductivity Detector) is an analytical instrument used to measure the conductivity of a solution. Its basic working principle is based on the ability of ions in a solution to conduct current. When two electrodes are inserted into a solution containing an electrolyte, applying a DC voltage or an AC voltage will generate a current between the two electrodes. The conductivity (G) of the solution is inversely related to the resistivity (ρ) and can be calculated by the following formula: G=1R=σ· / LG=R1=σ·A / L, where rR is the resistance, σσ is the conductivity, AA is the cross-sectional area between the electrodes, and LL is the distance between the electrodes. The waste liquid 2 generated after the detection is recovered into the waste liquid bottle.

[0048] Due to the change of ammonia content in ammonia-containing aqueous solution, its conductivity changes. The conductivity detector can accurately measure this change, and the detection value is then transmitted to the data processing workstation and converted into the concentration value of ammonia nitrogen through the pre-calibrated standard curve. That is, the ammonia nitrogen content in the original water sample is calculated through an algorithm. This method not only improves the detection efficiency, but also ensures the accuracy and reliability of the results. It is very suitable for large-scale water quality monitoring and research work.

[0049] Compared with traditional methods, this application provides a higher degree of automation, and the entire process from sample injection to result output requires almost no human intervention, which greatly reduces human errors and improves work efficiency. At the same time, the continuous flow property allows sample analysis to be completed in a short time, which is suitable for rapid screening of large batches of samples, as well as real-time online monitoring in the environment (such as rivers, reservoirs and other water bodies) or production (such as drinking water plants, sewage plants, beverage plants, etc.).

[0050] At the same time, the experimental process is simplified, the professional skill requirements for operators are lowered, the use of chemical reagents is reduced, and waste generation is reduced, which is in line with the principles of green chemistry.

[0051] As described above, the present application protects a method and device for detecting ammonia nitrogen in water by flow injection conductivity. All technical solutions that are identical or similar to the present case should be deemed to fall within the protection scope of the present case.

Claims

1. A method for detecting ammonia nitrogen in water by flow injection conductivity, characterized in that: The steps include: step S1: automatically inputting the test sample by flow injection mode; Step S2: mixing the input test sample with the sodium thiosulfate solution and the sodium hydroxide solution by pumping to form a mixed solution; Step S3: performing online distillation on the mixed solution to extract ammonia and water vapor mixed gas; Step S4: online condensing the extracted mixed gas of ammonia and water vapor to form an ammonia-containing aqueous solution; Step S5: degassing the aqueous ammonia solution after pumping; Step S6: The conductivity of the degassed ammonia-containing aqueous solution is detected by a conductivity detector.

2. The method for detecting ammonia nitrogen in water by flow injection conductivity as claimed in claim 1, characterized in that: The method further includes step S7: transmitting the detected conductivity to a data processing workstation, and calculating the ammonia nitrogen content in the detected sample through an algorithm.

3. The method for detecting ammonia nitrogen in water by flow injection conductivity as claimed in claim 1, characterized in that: The pumping method is peristaltic pump transmission.

4. A method for detecting ammonia nitrogen in water by flow injection conductivity as claimed in claim 3, characterized in that: The pumping of the test sample, sodium thiosulfate solution and sodium hydroxide solution in step S2 and the pumping of the ammonia solution in step S5 use the same peristaltic pump.

5. A device for flow injection conductivity detection of ammonia nitrogen in water, characterized in that: The invention comprises a mixing device for mixing the test sample and the sodium thiosulfate solution and the sodium hydroxide solution, an online distillation device for distilling the mixed solution, an online condensation device for condensing the mixed gas of the distilled ammonia and water vapor, a degassing tube for degassing the ammonia-containing aqueous solution produced by the condensation, and a conductivity detector for detecting the conductivity of the degassed ammonia-containing aqueous solution.

6. The device for flow injection conductivity detection of ammonia nitrogen in water as claimed in claim 5, characterized in that: It also includes a data processing workstation that calculates the ammonia nitrogen content in the test sample through an algorithm based on the detected conductivity.

7. The device for flow injection conductivity detection of ammonia nitrogen in water as claimed in claim 5, characterized in that: It also includes a peristaltic pump for conveying test samples, sodium thiosulfate solution, sodium hydroxide solution, and condensed ammonia solution.

8. The device for flow injection conductivity detection of ammonia nitrogen in water as claimed in claim 7, characterized in that: The number of the peristaltic pump is one, which can simultaneously transport the test sample, the sodium thiosulfate solution, the sodium hydroxide solution, and the condensed ammonia-containing aqueous solution.

9. The device for flow injection conductivity detection of ammonia nitrogen in water as claimed in claim 5, characterized in that: The mixing device comprises a tee for collecting the test sample, the sodium thiosulfate solution and the sodium hydroxide solution, and a surrounding reactor arranged at the rear end of the tee.

10. The device for flow injection conductivity detection of ammonia nitrogen in water as claimed in claim 5, characterized in that: It also includes a waste liquid bottle for recovering waste liquid after online distillation and conductivity detection.

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