CN1185480C - Method for testing water body COD - Google Patents
Method for testing water body COD Download PDFInfo
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- CN1185480C CN1185480C CNB021478236A CN02147823A CN1185480C CN 1185480 C CN1185480 C CN 1185480C CN B021478236 A CNB021478236 A CN B021478236A CN 02147823 A CN02147823 A CN 02147823A CN 1185480 C CN1185480 C CN 1185480C
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Abstract
The present invention relates to a method for measuring chemical oxygen demand (COD) of a water body, which belongs to a method for measuring the COD of the water body by using chemical and optical means. The method aims to overcome the defects of the existing measurement methods and provide a COD analysis method which has the advantages of simple structure and convenient popularization and application, and the method can fast and accurately realize the real-time monitoring for the COD of the water body. The method comprises the following steps: (1) counteracting a standard solution which has a determined value of the COD by using a potassium dichromate method and adjusting the pH value to 2.5 to 5.5; (2) adding a luminol solution and an H2O2 solution in a reaction chamber, and then adding counteracting liquor in the reaction chamber; (3) detecting the luminescence intensity of mixed liquor by using a photoelectric diode or a triode; (4) repeating the steps (1) to (3) for the standard solution with different COD values and plotting a relation curve of luminescence intensity to COD; and (5) repeating the steps (1) to (3) for a water sample to be measured under the same conditions. Thus, the COD value can be calculated according to the luminescence intensity on the relation curve (4).
Description
Technical field
The invention belongs to measuring method, particularly utilize chemistry and optical instrument to measure the method for chemical oxygen demand of water body.
Background technology
Chemical oxygen demand (COD) (COD) is one of important technology index that characterizes water body organic contamination degree, the COD assay method adopts to such an extent that be at most standard circumfluence method (permanganate indices method and potassium dichromate method oxidizing process) both at home and abroad at present, the former is mainly used in the analysis of underground water and cleaner surface water, and the latter is used for the analysis of industrial waste water and sanitary sewage more.It is accurate that standard circumfluence method has measurement result, high repeatability and other advantages, but also have significant disadvantages, and the time-consuming electricity that takes, reagent dosage is big, and a large amount of silver salt, mercury salt, abandoning of chromic salts are easily caused secondary pollution.For the needs of the automatic on-line monitoring of satisfying the COD value, for many years, vast analytical work person and efforts at environmental protection person are devoted to the research and development of new method and new COD automatic analyzer always.But up to the present, most methods is still under test, for the needs of the protection that conforms, carry out COD fast, the research of online auto monitoring, have far reaching significance for timely grasp and control water body COD situation.
The COD analytical approach mainly is divided into two classes by its measuring principle at present: one, spectrophotometric method; Two, electrochemical methods.Spectrphotometric method for measuring COD mainly is divided into two kinds of patterns: potassium dichromate is cleared up a photometric method and ultraviolet one visible spectrophotometry (254mm).After the former clears up water sample, with its absorbance of spectrphotometric method for measuring; The latter is without clearing up, the correlativity between the UV at 254mm place absorption signal size based on water sample COD value and water sample, with Xe (or low pressure mercury lamp) is light source, at the signal at 254mm place and the absorption signal of visible light (546mm), the two difference can be obtained water sample COD value by twin-beam Instrument measuring water sample after linearization process.When deciding COD value of waste water, because sample without clearing up direct mensuration, has so just caused this method not ideal to the accuracy of a lot of COD value of waste water mensuration with the UV instrumentation.The photomultiplier that these two kinds of patterns all need light source, light path system and use as detecting device so just causes instrument cost higher, and difficult C﹠M especially is difficult to be suitable for the actual working environment of factory.
Electrochemical method mainly comprises coulometry, potential method, electrostatic current method, polarography etc.Its main pattern has: potassium dichromate clears up-and coulometric titration, hydroxy and ozone (mixed oxygenant) oxidation and ozone oxidation-electrochemical measurement method, the same coulometry of the former principle, the latter's principle is electrolytic hydroxy and ozone or the ozone that adds, organism in reactive tank in the direct oxidation water sample, produce the electric weight of ozone-depleting with electrolysis oxygenant institute's consumed current or by ozone-depleting amount or electrolysis, according to Faraday's law, can calculate water sample COD value after calibrated.Also there is its inevitable shortcoming in electrochemical process measure CO D, need carry out titration as coulometry, time-consuming and trouble; Electrode in potentiostatic method and oxygenant-electrochemical measurement method easily poisons, and the electrochemical method poor reproducibility, and this is the most fatal shortcoming of this method; The required polarograph of polarogram rule is more expensive, and polarograph is unsuitable for being developed further into online COD analyser.
Summary of the invention
Chemical oxygen demand of water body assay method of the present invention, purpose is the defective that overcomes above-mentioned technology, provides a kind of simple in structure, COD analytical approach of being easy to promote the use of, to realize the real-time monitoring to water body COD quickly and accurately.
The present invention is a kind of chemical oxygen demand of water body assay method, comprise the steps: that (1) is that the mark liquid of determined value carries out the chromium method and clears up to chemical oxygen demand (COD), (2) pH value of digestion solution with dilution is adjusted between the 2.5-5.5, (3) in reaction chamber, add luminol analytic liquid and superoxol, add digestion solution again, form mixed liquor, (4) utilize photodiode or phototriode to detect the luminous intensity of mixed liquor, (5) be that the mark liquid of different determined values repeats above-mentioned (1)-(4) step to chemical oxygen demand (COD) respectively, set up the linear relationship curve of standard mixed liquor luminous intensity and chemical oxygen demand (COD), stand-by, (6) detected water sample is repeated above-mentioned (1)-(4) step according to the same terms, the luminous intensity of surveying according to (5) described linear relationship curve, extrapolate the chemical oxygen demand value of water sample.
Described chemical oxygen demand of water body assay method, luminol analytic liquid concentration can be 2.5 * 10
-4-7 * 10
-4M, superoxol concentration can be 5 * 10
-2-9 * 10
-2M.
Described chemical oxygen demand of water body assay method, the volume ratio of mixed liquor is: luminol analytic liquid 3-5, superoxol 1.5-2.5, digestion solution 2.5-3.5
The principle of this assay method is that potassium dichromate oxidation of organic compounds in acid solution is reduced into trivalent chromium, and trivalent chromium can catalysis Luminol-H
2O
2System produces very strong chemiluminescence because this luminescence system not only classics but also luminous intensity were big, so only need utilize photodiode just the light intensity of this system generation to be detected, and then reach the purpose of monitoring water body COD value.
Assay method of the present invention mainly contains following advantage:
The one, chemiluminescence method measure in the water body chromic highly sensitive, the range of linearity is wide, analysis speed is fast.
The 2nd, the detectability of COD is low: because this luminescence system range of linearity is wide, luminous intensity is big, thereby can realize the accurate mensuration of low COD value water sample.Experiment is found, only needs wanting the appropriate change experiment condition, just can accurately measure the COD value of COD=3mg/L water sample.This point COD analyser in the past is irrealizable, and the detectability of COD analyser was generally more than COD=10mg/L in the past.
The 3rd, the simplicity of this determinator: behind the Specimen eliminating, only need a simple photodiode or phototriode just can realize mensuration to COD, do not need light source and power supply, and conventional spectrophotometry COD must need the photomultiplier of light source, light path system and detection usefulness at least; The galvanochemistry rule needs electrode and more expensive instrument.
The 4th, applicability is strong: can be used for the laboratory off-line monitoring or carry out scientific research, also can further develop the automatic on-line monitoring that is used for COD.
Description of drawings
Fig. 1 is the luminous intensity-COD canonical plotting under a kind of test condition;
Fig. 2 is the luminous intensity-COD canonical plotting under the another kind of test condition;
Fig. 3 is the luminous intensity under another test condition-COD canonical plotting.
Embodiment
Embodiment one:
Main agents K
2Cr
2O
7Solution 1.500mol/L, (NH4)
2FeSO
4Solution 0.1mol/L, Ag
2SO
4-H
2SO
4Mixed liquor: 0.1g:100ml, phthalic acid potassium standard solution 2.084mmol/L (above solution is all by the GB11914-89 preparation).Luminol analytic liquid: measure 250mll * 10
-3The luminol stock solution of M (preparing with the reagent that plucka produces) in the 500ml beaker, adds 50mlEDTA solution, 4.2 gram NaHCO
3, 30 gram KBr and 250ml water are to be made into 500 ml solns after 12 with the NaOH solution adjusting pH of 2M.Luminol concentration is 5 * 10 in this solution
-4M.H
2O
2Solution 8 * 10
-2M (includes 1 * 10
-3The EDTA of M).EDTA solution 0.01M.KBr solution 2.5M.It is pure that above reagent is analysis, and institute's water all is a redistilled water.
The preparation of test solution (mark liquid)
By GB11914-89 with actual waste water sample (standard specimen) reflux clear up and cool off after, be diluted to 100ml, measure the 0.25ml digestion solution in the 25ml volumetric flask, successively to the KBr solution that wherein adds 2.5ml2.5M, 2.5ml0.01M EDTA solution, and to regulate pH with the NaOH solution of 2M be about 3.0, and constant volume is to 25ml.Filtering out silver bromide post precipitation reserved filtrate that the adding because of potassium bromide produces does to measure and uses.Add 0.4ml luminol analytic liquid successively in the cuvette of reaction chamber, 0.2mlH2O2 solution covers the door of reaction chamber then, injects 0.3ml filtrate with syringe at last, writes down luminous signal.
With COD be 0,25,50,100,200,300,400,500 respectively, the O-phthalic hydrogen potassium standard solution of 600mg/L by the GB11914-89 method reflux clear up after, by top condition digestion solution is measured, and the drawing curve, see Fig. 1.Get regression equation: Y=1.0344X-23.584, ((wherein X is a luminous value to R=0.9990, the mV of unit; Y is the COD value, the mg/L of unit).The range of linearity of COD value is 0-600mg/L.
With COD is that the food wastewater of 180.5mg/L (standard method measured value) carries out 6 parallel laboratory tests, the results are shown in Table 1.As shown in Table 1, the COD mean value that this method records is 179.9mg/L, and relative standard deviation is 6%.
Table 1 precision experimental result
| Sample number | 1 | 2 | 3 | 4 | 5 | 6 | Mean value | The coefficient of variation |
| Actual measurement COD value (mg/L) | 187.6 | 184.9 | 193.8 | 165.4 | 170.3 | 177.6 | 179.9 | 6.0％ |
Several different waste water recovery of standard addition see Table 2.As shown in Table 2, in 100 ± 10% scopes, accuracy is better substantially for recovery of standard addition.
Table 2 waste water recovery of standard addition
| The waste water title | Sample COD (mg/L) | Mark-on COD (mg/L) | (sample+mark) actual measurement COD (mg/L) | Standard specimen is added (mg/L) | Add yield |
| Food wastewater | 307.0 | 50 | 358.8 | 51.8 | 103.6 |
| Waste water from dyestuff 1 | 341.6 | 100 | 431.1 | 89.5 | 89.5 |
| Waste water from dyestuff 2 | 450.6 | 100 | 543.6 | 93.0 | 93.0 |
| Percolate | 416.6 | 100 | 519.5 | 102.9 | 102.9 |
| Organic wastewater | 206.7 | 100 | 304.5 | 97.7 | 97.7 |
| East Lake water sample | 25.2 | 250 | 288.7 | 263.5 | 105.4 |
Adopt this method that several different waste water are measured, and compare with standard method, it the results are shown in Table 3.As shown in Table 3, this method is used for the mensuration of COD, and precision and accuracy as a result is all better, can be used for the mensuration of various waste water CODs.
The comparison of two kinds of method COD of table 3 measurement result
| The waste water title | Standard method records COD value A (mg/L) | Chemoluminescence method records COD value B (mg/L) | Relative error (B-A) ÷ A*100 |
| Food wastewater | 317.8 | 307.0 | -3.40 |
| Waste water from dyestuff 1 | 350.6 | 341.6 | -2.57 |
| Waste water from dyestuff 2 | 447.8 | 450.6 | 0.63 |
| Percolate | 446.4 | 416.6 | -6.67 |
| Organic wastewater | 196.5 | 206.7 | 5.19 |
| East Lake water sample | 28.7 | 25.2 | -12.2 |
Embodiment two:
With the Potassium Hydrogen Phthalate is standard specimen, is respectively 25,75,125,250,375,500 and after the mark liquid of 625mg/mL clears up backflow by GB11914-89 with the COD value, dilute 20 times after test condition: luminol analytic liquid concentration: 3 * 10
-4M, concentration of hydrogen peroxide: 6 * 10
-2M, test solution pH:4.0-4.5, sampling volume: 0.3mL, the adding volume ratio of luminol analytic liquid, hydrogen peroxide and test solution is 4: 2: 3.Measure.Get following typical curve, Y=4.6066X+29.995, R=0.9952.See Fig. 2.
Embodiment three:
With the Potassium Hydrogen Phthalate is standard model, is respectively 0,25,100,200,300,400,500 and after the mark liquid of 600mg/mL clears up backflow by GB11914-89 with the COD value, dilute 100 times after test condition: luminol analytic liquid concentration: 6 * 10
-4M, concentration of hydrogen peroxide: 9 * 10
-2M, test solution pH:2.5, sampling volume: 0.6mL, luminol analytic liquid, hydrogen peroxide and test solution volume ratio 3.5: 1.8: 2.8.Measure.Get following typical curve: Y=0.9801X-6.2329, R=0.9965.See Fig. 3.
Claims (3)
1. a chemical oxygen demand of water body assay method comprises the steps:
(1) be that the mark liquid of determined value carries out the chromium method and clears up to chemical oxygen demand (COD),
(2) pH value of digestion solution with dilution is adjusted between the 2.5-5.5,
(3) in reaction chamber, add luminol analytic liquid and superoxol, add digestion solution again, form mixed liquor,
(4) utilize photodiode or phototriode to detect the luminous intensity of mixed liquor,
(5) be that the mark liquid of different determined values repeats above-mentioned (1)-(4) step to chemical oxygen demand (COD) respectively, set up the linear relationship curve of standard mixed liquor luminous intensity and chemical oxygen demand (COD), stand-by;
(6) detected water sample is repeated above-mentioned (1)-(4) step according to the same terms, the luminous intensity of surveying according to (5) described linear relationship curve, extrapolate the chemical oxygen demand value of water sample.
2. chemical oxygen demand of water body assay method as claimed in claim 1 is characterized in that luminol analytic liquid concentration is 2.5 * 10
-4-7 * 10
-4M, superoxol concentration are 5 * 10
-2-9 * 10
-2M.
3. chemical oxygen demand of water body assay method as claimed in claim 1 or 2 is characterized in that the volume ratio of mixed liquor is: luminol analytic liquid 3-5: superoxol 1.5-2.5: digestion solution 2.5-3.5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021478236A CN1185480C (en) | 2002-12-12 | 2002-12-12 | Method for testing water body COD |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021478236A CN1185480C (en) | 2002-12-12 | 2002-12-12 | Method for testing water body COD |
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|---|---|
| CN1419117A CN1419117A (en) | 2003-05-21 |
| CN1185480C true CN1185480C (en) | 2005-01-19 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674936B (en) * | 2013-12-11 | 2016-05-04 | 常熟理工学院 | A kind of based on electrochemical luminescence COD method for quick and device |
| CN110683993B (en) * | 2019-10-16 | 2022-11-04 | 黄冈师范学院 | Preparation method and application of ferrous phthalhydrazide |
| CN114965446B (en) * | 2022-03-28 | 2024-08-13 | 华东师范大学 | Method for measuring chemical oxygen demand in sewage and wastewater by using chemiluminescence quenching method |
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