Method for reducing measurement error of sediment nitrogen and increasing integrity of continuously extracted sample by adopting multi-stage composite adsorption column

Abstract

The invention belongs to the technical field of water environment research and treatment, and particularly relates to a method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by adopting a multi-stage composite adsorption column. The method comprises the following steps: firstly, weighing a sediment sample, screening, putting into a colorimetric tube, adding alkaline potassium persulfate for high-temperature digestion, taking out the sample, cooling to room temperature, adding a hydrochloric acid solution for color development, uniformly shaking to obtain supernate, putting a multi-stage composite adsorption column into the supernate, standing, settling and adsorbing to obtain a sample; and measuring the absorbance of the supernate by adopting an ultraviolet spectrophotometer to obtain the method for reducing the measurement error of the sediment nitrogen and increasing the integrity of the continuously extracted sample by adopting the multi-stage adsorption column.

Description

Technical Field

[0001] The present invention belongs to the technical field of water environment research and treatment, and particularly relates to a method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column. Background Art

[0002] Water is the basis of life. However, due to the accelerating development of human activities, industrialization, and urbanization, the problem of water pollution has become increasingly prominent. Various pollutants have appeared in water bodies and are enriched in sediments in the form of sedimentation. These pollutants have damaged the water ecosystem, threatened the survival and reproduction of aquatic organisms, and at the same time, they will enter the human drinking water source through water bodies, bringing risks to human health. Ecological environment governance is a very important link, and the governance of sediments is a very important part of water environment governance. How to accurately obtain the indicators in sediments has become a prerequisite for effective environmental governance.

[0003] Nitrogen in sediments is an important part of the nitrogen cycle in the water ecosystem. The nitrogen content in sediments is relatively high in many regions, resulting in serious eutrophication problems in water bodies. The current mainstream method for measuring sediment nitrogen is to refer to the measurement method of total nitrogen in water quality, convert particulate nitrogen into dissolved nitrogen, and then use ultraviolet spectrophotometry for measurement. The conversion method can use alkaline potassium persulfate digestion method. Before measurement, it is required that the sample to be measured passes through a 100-mesh sieve.

[0004] The above method is widely used in the field of soil and can effectively measure the total nitrogen content in soil. However, since sediments are formed by the settlement of suspended fine particles, their particle viscosity is weaker than that of soil, and their suspension is higher than that of soil. Many small particles are resuspended in the supernatant. According to the principle of ultraviolet spectrophotometry, suspended particulate matter has an error effect on the measurement result. When measuring the total nitrogen in water, there are no particulate matters in the sample, so the true value can be approximated by multiple measurements to reduce the error. However, when measuring sediments, there must be small particulate matters. In the past, filtration was used to obtain a supernatant with fewer particulate matters, but in this way, the sediment sample was discarded and could not meet the requirements of continuous chemical extraction. Therefore, there is an urgent need for a method that can effectively reduce the concentration of suspended fine particulate matter and retain the sample without affecting the nature of the indicators. Summary of the Invention

[0005] In view of the disadvantages and problems existing in the prior art, the present invention provides a method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, including the following steps:

[0006] Weigh the sediment sample, screen it, put it into a colorimetric tube, add alkaline potassium persulfate for high-temperature digestion, take out the sample and cool it to room temperature, add hydrochloric acid solution for color development and shake well to obtain the supernatant. Put the multi-stage composite adsorption column into the supernatant, let it stand for sedimentation and adsorption, and measure the absorbance of the supernatant with an ultraviolet spectrophotometer to obtain a method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples using a multi-stage adsorption column.

[0007] Further, a 100-mesh sieve is used in the screening process.

[0008] Further, the volume of the colorimetric tube is 25 mL.

[0009] Further, the temperature in the high-temperature digestion process is 130 °C and the time is 30 min.

[0010] Further, the standing time is 15 min.

[0011] Further, the mass ratio of potassium persulfate to sodium hydroxide in the alkaline potassium persulfate solution is 8:3.

[0012] Further, the hydrochloric acid solution is prepared by mixing concentrated hydrochloric acid and deionized water in a ratio of 1:9.

[0013] Further, the height of the multi-stage composite adsorption column is 2 cm and the diameter is 0.5 cm.

[0014] Further, the multi-stage composite adsorption column includes activated carbon, porous ceramics, and activated carbon fibers.

[0015] Further, the fiber pore diameter of the activated carbon in the multi-stage composite adsorption column is 50 nm to 1 μm, and the pore diameter of the porous ceramics is 1 μm.

[0016] Beneficial effects

[0017] A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples using a multi-stage composite adsorption column provided by the present invention. Different from the previous use of powdered activated carbon in water treatment and hoping to keep it suspended to achieve the maximum adsorption effect, the method proposed in this application avoids the re-suspension of powdered activated carbon from further affecting the light absorption performance.

[0018] This invention focuses on the impact of suspended solids in the supernatant, which has received little attention in sediment measurement, on the accuracy of results. By using the adsorption performance of a multi-stage composite adsorption column, the concentration of suspended fine particles in the supernatant is significantly reduced, and the reaction intensity of dissolved nitrogen itself to ultraviolet light is increased. The method and structural chemistry properties provided by this invention are stable, and while being easy to operate, they will not affect the results due to the release of substances from added components. Moreover, the multi-stage combination method proposed by this invention increases the adsorption efficiency, taking into account the wide size distribution of suspended particles in the supernatant. The method is applicable to sediment samples in most regions. The method is universal and can be used for sediment tests that require clear supernatant.

[0019] The method provided by this invention can also achieve multi-stage preservation of samples. Subsequent measurements of nitrogen index at different levels can be continuously used. At the same time, by utilizing the interception ability of the activated carbon fiber column, the loss of samples is reduced, further improving the accuracy of subsequent measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the exemplary embodiments of this invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0021] Figure 1 Schematic diagram of the activated carbon multi-stage adsorption column of Embodiment 1 of this invention;

[0022] Figure 2 Comparison chart of the average values and upper and lower error limits before and after implementing the patent method for the same sample in Embodiment 1 of this invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Next, the technical solutions in the embodiments of this invention will be clearly and completely described in combination with Embodiment 1 of this invention and the attached Figures 1 to 2 , It is obvious that the described embodiments are only part of the embodiments of this invention, rather than all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this invention.

[0024] Embodiment 1

[0025] Pass the dry sediment sample through a 100-mesh sieve. Weigh 0.1 g of the sieved sediment sample, place 0.1 g of the sediment sample into a 25-mL colorimetric tube, and add 20 mL of alkaline potassium persulfate solution; this alkaline potassium persulfate solution is prepared by dissolving 40 g of potassium persulfate and 15 g of sodium hydroxide in deionized water and making up the volume to 1 L.

[0026] Digest it in a high-temperature digestion furnace at 130 °C for 30 min, take it out and cool it to room temperature, and add 1 mL of hydrochloric acid solution for color development; this hydrochloric acid solution is prepared by mixing concentrated hydrochloric acid with a density of 1.19 g / mL and deionized water in a ratio of 1:9. After shaking well, place a multi-stage composite adsorption column into the supernatant, let it stand for 15 min for sedimentation and adsorption, and then measure the absorbance of the supernatant using an ultraviolet spectrophotometer. During the measurement, use a 10-mm quartz cuvette, and the ultraviolet spectrophotometer measures in a multi-wavelength mode, which are 220 nm and 275 nm respectively; pour out the supernatant, dry the sample for storage or, after shaking well again, place the multi-stage composite adsorption column into the supernatant for continuous extraction.

[0027] Combined with Figure 1 It can be known that the size of the multi-stage composite adsorption column in Example 1 is 2 * 0.5 cm, where the height is 2 cm. This height can increase the contact area of the supernatant and increase the adsorption area. The diameter of 0.5 cm is smaller than the inner diameter of the colorimetric tube, which can effectively be put in and leave space for the supernatant to flow out, and at the same time play the interception function of the outer activated carbon fiber. The principle of multi-stage adsorption is that the particle size of the suspended particles in the supernatant is between 1 nm and 1 μm, and the particle size distribution is relatively wide.

[0028] Using a multi-stage adsorption composite material, the adsorption pores of the upper activated carbon are between 2 nm and 50 nm, which can effectively adsorb the small-sized fine particles in the supernatant; the maximum adsorption pore diameter of the lower porous ceramic is 1 μm, which can effectively adsorb the larger-sized fine particles; the pore diameter of the outer activated carbon fiber is between 50 nm and 1 μm, which can provide adsorption sites and play an interception role at the same time to prevent the sample particles from flowing out when pouring out the supernatant. Since the characteristic of the suspended particles is that the smaller size is near the water surface layer and the larger size is near the water bottom layer, the multi-stage composite adsorption column is placed with the porous ceramic end down.

[0029] When performing continuous sample processing in Example 1, it can be directly processed together with the multi-stage composite adsorption column because the activated carbon and porous ceramic have stable chemical properties and will not contaminate the sample. Even at high temperatures, their microstructures can remain stable and continue to play a role.

[0030] The method of Example 1 is used to measure the sample 3 times, and the results and averages of each measurement are shown in Figure 2, the result proves that the upper and lower errors are significantly reduced, and the single measurement result is closer to the multiple average value. By this method, the accuracy and feasibility of each measurement are greatly improved.

[0031] Compared with the prior art, the present invention has the following substantial improvements:

[0032] The present invention provides a method using a multi-stage composite adsorption column to reduce the measurement error of sediment nitrogen and increase the integrity of continuously extracted samples. Different from traditional powdered activated carbon, this method avoids the suspension of powdered activated carbon and its influence on light absorption performance. The invention pays attention to the influence of supernatant suspended solids, which are often ignored in sediment measurement, on the accuracy of measurement results. By using a multi-stage composite adsorption column, the concentration of fine particles in the supernatant is effectively reduced, thereby enhancing the reaction intensity of dissolved nitrogen to ultraviolet light. This method has the advantages of stable structural chemical properties, simple operation, and no influence on results due to the release of substances from added components. The multi-stage combination method increases the adsorption efficiency. Considering the wide range of particle size distributions in the supernatant, the method is applicable to sediment samples in most regions and has wide applicability. In addition, the present invention can achieve multi-stage preservation of samples, support continuous measurement of subsequent hierarchical nitrogen indicators, and reduce sample loss through the interception ability of the activated carbon fiber column, further improving the accuracy of measurement results.

Claims

1. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, It includes the following steps: Weigh the sediment sample, after screening, put it into a colorimetric tube, add alkaline potassium persulfate for high-temperature digestion, take out the sample and cool it to room temperature, add hydrochloric acid solution for color development and shake well to obtain the supernatant. Put the multi-stage composite adsorption column into the supernatant, let it stand for sedimentation and adsorption, and use an ultraviolet spectrophotometer to measure the absorbance of the supernatant, obtaining a method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage adsorption column.

2. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that A 100-mesh sieve is used in the screening process.

3. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The volume of the colorimetric tube is 25 mL.

4. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The temperature in the high-temperature digestion process is 130 °C and the time is 30 min.

5. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that The standing time is 15 min.

6. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The mass ratio of potassium persulfate to sodium hydroxide in the alkaline potassium persulfate solution is 8:

3.

7. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The hydrochloric acid solution is prepared by mixing concentrated hydrochloric acid and deionized water in a ratio of 1:

9.

8. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The height of the multi-stage composite adsorption column is 2 cm and the diameter is 0.5 cm.

9. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The multi-stage composite adsorption column includes activated carbon, porous ceramics and activated carbon fibers.

10. A method for reducing the measurement error of sediment nitrogen and increasing the integrity of continuously extracted samples by using a multi-stage composite adsorption column, characterized in that, The fiber pore diameter of the activated carbon in the multi-stage composite adsorption column is 50 nm to 1 μm, and the pore diameter of the porous ceramics is 1 μm.

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