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Method for measuring concentration of low-concentration soluble organic nitrogen in water

A technology of dissolved organic nitrogen and concentration, applied in testing water, chemical instruments and methods, preparation of samples for testing, etc., can solve the problems of difficulty in large-scale popularization and application, high cost of dialysis membranes, and achieve convenient control, simple operation, The effect of reducing bias

Active Publication Date: 2010-07-21
TONGJI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the cost of the method device, dialysis tube and dialysis membrane is very high, and the required time is at least 24 hours, making it difficult to popularize and apply in a large area

Method used

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  • Method for measuring concentration of low-concentration soluble organic nitrogen in water
  • Method for measuring concentration of low-concentration soluble organic nitrogen in water
  • Method for measuring concentration of low-concentration soluble organic nitrogen in water

Examples

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Effect test

example 1

[0047] Taking the water samples from a waterworks factory filtered by 0.22 or 0.45 μm as the research object, the water samples were adjusted to be neutral with HCl and NaOH, and different types of nanofiltration membranes were used in the test for pretreatment of the DON test to control the concentration of the water samples is about 6 times. The influence of three types of nanofiltration membranes on the measurement results is compared. The analytical instruments used in the test are shown in Table 1.

[0048] Table 1 Instruments and equipment used in the test

[0049]

[0050] From attached Figure 4 It can be found that: under the condition of no nanofiltration membrane pretreatment, the same water sample was directly measured by the differential method for 4 times, and the DON concentration in the water sample varied from -0.1 to 0.4mg / L, and the standard deviation was 0.21mg / L , the effective DON concentration value cannot be obtained at all; after pretreatment by di...

example 2

[0052] Taking the water samples filtered by 0.22 or 0.45 μm from a water plant as the research object, the effects of the pH of the water samples at 3, 4, 5, 6, 7, 8, 9, and 10 on the determination of DON by this pretreatment method were studied respectively. . The analytical instruments used in the test process are shown in Table 1. In the test, the nanofiltration membrane 3 was used as the separation component, and the concentration ratio of the water sample was controlled to be 6 times. Under different pH conditions, the measurement results of DON and the changes of DIN / TDN values ​​are as follows: attached Figure 5 shown. It can be seen from the comparison of the figures that the measured value of DON is the highest when the pH is between 6.5 and 7.5. The reason for the analysis is that the interception effect of nanofiltration membranes on inorganic ions in water is different under different pH values, which ultimately leads to different proportions of DIN / TDN; when pH...

example 3

[0054] Taking the water samples filtered by 0.22 or 0.45 μm from a waterworks factory as the research object, the test adopts the method of adjusting the volume of different filtered samples and keeping the same volume of concentrated water. 5, 7.5, 12.5, 25cm 3 / cm 2 , and the corresponding concentration ratios are 2, 4, 6, 10, 20 respectively, and the final DON results are compared, the results are as attached Figure 6 shown. It can be seen from the figure that the ratio of the total volume of the concentrated water sample to the area of ​​the filter membrane is controlled at 7.5-12.5cm 3 / cm 2 , when the corresponding concentration ratio is 6-10 times, the DIN proportion in the obtained concentrated water (i.e. the water before the membrane) is the lowest, and the DON content is the highest. Too high concentration ratio has resulted in obvious concentration polarization and DON loss phenomenon.

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Abstract

The invention relates to a method for measuring concentration of low-concentration soluble organic nitrogen in water, in which the nano filtration membrane separation technology is employed to accurately measure concentration of soluble organic nitrogen. In the preparation process before pretreatment, membrane with a pore diameter being more than or equal to 0.22mu m and less than or equal to 0.45mu m is employed to remove particle impurities of a water sample.300-500mL of filtered water sample is taken, pH value is adjusted to 6.0-9.0; in the process of pretreatment, selective nano filtration membrane with a cut-off molecular weight being 150-500 Dalton is adopted for dead-end or cross flow filtration; so that 6-15 times of concentration and enrichment of DON in the water sample can be achieved; the DON content is obtained by using the total nitrogen to reduce other forms of nitrogen content of other measurements and then dividing actual concentration times. In the invention, accuracy and precision of DON measurement are greatly improved, so that the problems that negative values often appear in the direct water sample determination method and concentration standard deviation is large are solved; in addition, the whole measurement process of the measurement method is simple and effective, easy to operate, low in cost, so that the measurement method can be widely applied to surface water and ground watermonitoring and monitoring and analysis of small, medium and large waterplants.

Description

technical field [0001] The invention belongs to the fields of environmental protection and water treatment, and relates to an effective method for measuring dissolved organic nitrogen (DON) in water. Background technique [0002] At present, the micro-polluted raw water in my country generally has problems such as excessive organic matter content, high concentration of nitrogen-containing compounds, peculiar smell of water body, high chroma, and algae blooms. In view of the widespread presence of dissolved organic matter (DOM) in water is very easy to undergo halogenation reaction with chlorine to form trihalomethane, haloacetic acid, haloacetonitrile, furanone (MX) and other chlorinated disinfection by-products, so the organic matter in slightly polluted raw water Elimination control has been a continuing focus of interest in the field. DON occupies a considerable proportion in DOM, and its content is about 0.5% to 10%. The main types include NHs, aminos, nitriles, purines...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N33/18G01N30/96G01N21/31G01N1/34G01N1/40C02F1/00
Inventor 李伟徐斌高乃云夏圣骥李大鹏田富箱
Owner TONGJI UNIV
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