CN116990443B - Accurate detection method for COD in high-chlorine low-COD water sample - Google Patents
Accurate detection method for COD in high-chlorine low-COD water sample Download PDFInfo
- Publication number
- CN116990443B CN116990443B CN202311264007.XA CN202311264007A CN116990443B CN 116990443 B CN116990443 B CN 116990443B CN 202311264007 A CN202311264007 A CN 202311264007A CN 116990443 B CN116990443 B CN 116990443B
- Authority
- CN
- China
- Prior art keywords
- sample
- cod
- concentration
- water sample
- detected
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 157
- 238000001514 detection method Methods 0.000 title claims abstract description 44
- 239000000460 chlorine Substances 0.000 title claims abstract description 37
- 229910052801 chlorine Inorganic materials 0.000 title claims abstract description 37
- 150000001875 compounds Chemical class 0.000 claims abstract description 100
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 90
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 90
- 238000000034 method Methods 0.000 claims abstract description 55
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 46
- 239000012895 dilution Substances 0.000 claims abstract description 25
- 238000010790 dilution Methods 0.000 claims abstract description 25
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 238000001556 precipitation Methods 0.000 claims abstract description 16
- 230000036284 oxygen consumption Effects 0.000 claims abstract description 8
- 239000000523 sample Substances 0.000 claims description 249
- 239000012086 standard solution Substances 0.000 claims description 54
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 51
- 239000012496 blank sample Substances 0.000 claims description 38
- DLFVBJFMPXGRIB-UHFFFAOYSA-N Acetamide Chemical compound CC(N)=O DLFVBJFMPXGRIB-UHFFFAOYSA-N 0.000 claims description 36
- ZHNUHDYFZUAESO-UHFFFAOYSA-N Formamide Chemical compound NC=O ZHNUHDYFZUAESO-UHFFFAOYSA-N 0.000 claims description 36
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 36
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 claims description 34
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 30
- 238000004448 titration Methods 0.000 claims description 21
- IMBKASBLAKCLEM-UHFFFAOYSA-L ferrous ammonium sulfate (anhydrous) Chemical compound [NH4+].[NH4+].[Fe+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O IMBKASBLAKCLEM-UHFFFAOYSA-L 0.000 claims description 20
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 18
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 claims description 15
- 239000000243 solution Substances 0.000 claims description 15
- QLOKJRIVRGCVIM-UHFFFAOYSA-N 1-[(4-methylsulfanylphenyl)methyl]piperazine Chemical compound C1=CC(SC)=CC=C1CN1CCNCC1 QLOKJRIVRGCVIM-UHFFFAOYSA-N 0.000 claims description 14
- 230000001502 supplementing effect Effects 0.000 claims description 14
- DOBUSJIVSSJEDA-UHFFFAOYSA-L 1,3-dioxa-2$l^{6}-thia-4-mercuracyclobutane 2,2-dioxide Chemical compound [Hg+2].[O-]S([O-])(=O)=O DOBUSJIVSSJEDA-UHFFFAOYSA-L 0.000 claims description 12
- 229910000370 mercury sulfate Inorganic materials 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 11
- YUVLVONHNMXKBW-UHFFFAOYSA-L [Ag+2].OS(O)(=O)=O.[O-]S([O-])(=O)=O Chemical compound [Ag+2].OS(O)(=O)=O.[O-]S([O-])(=O)=O YUVLVONHNMXKBW-UHFFFAOYSA-L 0.000 claims description 10
- GGCZERPQGJTIQP-UHFFFAOYSA-N sodium;9,10-dioxoanthracene-2-sulfonic acid Chemical compound [Na+].C1=CC=C2C(=O)C3=CC(S(=O)(=O)O)=CC=C3C(=O)C2=C1 GGCZERPQGJTIQP-UHFFFAOYSA-N 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 9
- 239000011790 ferrous sulphate Substances 0.000 claims description 8
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 8
- 239000000706 filtrate Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 8
- 238000009835 boiling Methods 0.000 claims description 7
- 239000012153 distilled water Substances 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 7
- 239000011449 brick Substances 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 230000007935 neutral effect Effects 0.000 claims description 6
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 150000001722 carbon compounds Chemical class 0.000 claims description 5
- 238000012952 Resampling Methods 0.000 claims description 4
- 229940096017 silver fluoride Drugs 0.000 claims description 4
- REYHXKZHIMGNSE-UHFFFAOYSA-M silver monofluoride Chemical compound [F-].[Ag+] REYHXKZHIMGNSE-UHFFFAOYSA-M 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- DGEZNRSVGBDHLK-UHFFFAOYSA-N [1,10]phenanthroline Chemical compound C1=CN=C2C3=NC=CC=C3C=CC2=C1 DGEZNRSVGBDHLK-UHFFFAOYSA-N 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 3
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 claims description 3
- 238000007865 diluting Methods 0.000 claims description 2
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 229910021607 Silver chloride Inorganic materials 0.000 abstract description 4
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 abstract description 4
- 238000004458 analytical method Methods 0.000 abstract description 3
- 238000012360 testing method Methods 0.000 description 14
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 11
- 229910052760 oxygen Inorganic materials 0.000 description 11
- 239000001301 oxygen Substances 0.000 description 11
- 230000029087 digestion Effects 0.000 description 10
- 239000000126 substance Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000004364 calculation method Methods 0.000 description 6
- 230000000873 masking effect Effects 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- -1 552.80mg/L Chemical class 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- ZBJWWKFMHOAPNS-UHFFFAOYSA-N loretin Chemical compound C1=CN=C2C(O)=C(I)C=C(S(O)(=O)=O)C2=C1 ZBJWWKFMHOAPNS-UHFFFAOYSA-N 0.000 description 2
- 229950010248 loretin Drugs 0.000 description 2
- 102000008857 Ferritin Human genes 0.000 description 1
- 238000008416 Ferritin Methods 0.000 description 1
- 108050000784 Ferritin Proteins 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- RCTYPNKXASFOBE-UHFFFAOYSA-M chloromercury Chemical compound [Hg]Cl RCTYPNKXASFOBE-UHFFFAOYSA-M 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000011895 specific detection Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/38—Diluting, dispersing or mixing samples
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/82—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a precipitate or turbidity
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Molecular Biology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Plasma & Fusion (AREA)
- Biomedical Technology (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
The invention provides an accurate detection method of COD in a high-chlorine low-COD water sample, which comprises the steps of firstly carrying out precipitation chlorine removal or dilution on the water sample, reducing the concentration of chloride ions to 1000mg/L or below, then adding a carbon straight-chain compound, calculating according to the mode that the carbon straight-chain compound is completely oxidized and converted into oxygen consumption, subtracting the conversion value of the carbon straight-chain compound from the COD concentration of the sample to be detected after adding the carbon straight-chain compound, obtaining the COD concentration of the sample to be detected before adding the carbon straight-chain compound, multiplying the COD concentration by the dilution multiple, and finally obtaining the COD concentration of the water sample; compared with the prior art, the method has the advantages that the carbon straight-chain compound is added, so that detection errors caused by taking away organic suspended matters by silver chloride precipitation are compensated, the detection precision is improved, the application range is improved, the method is suitable for clear water samples and turbid water samples, and the industrial application feasibility is high; belongs to the technical field of analysis and detection.
Description
Technical Field
The invention relates to the technical field of analysis and detection, in particular to an accurate detection method for COD in a high-chlorine low-COD water sample.
Background
Chemical Oxygen Demand (COD) is one of important indexes for detecting and evaluating the pollution degree of water quality in China, so that the accuracy of the chemical oxygen demand detection is particularly important. At present, the chemical oxygen demand of water is generally detected according to the specification of HJ 828-2017 'determination of chemical oxygen demand of water and dichromate method', and the principle is as follows: adding a known amount of potassium dichromate solution into a water sample, taking mercury sulfate as a chloride ion masking agent, taking sulfuric acid-silver sulfate as a catalyst, heating to boiling reflux, carrying out digestion reaction on the potassium dichromate and organic matters in the water sample, consuming the potassium dichromate, cooling to normal temperature after the reaction is finished, taking a ferron as an indicator, titrating unreduced potassium dichromate in the water sample by using ferrous ammonium sulfate, calculating the amount of unreduced potassium dichromate by using the titration amount of the ferrous ammonium sulfate, calculating the amount of consumed potassium dichromate, and calculating the mass concentration of consumed oxygen by using the amount of consumed potassium dichromate, namely the chemical oxygen demand CODcr.
However, the influence of chloride ions in the water sample on the detection result of the CODcr is large, although mercury sulfate is added as a chloride ion masking agent in digestion to enable the mercury sulfate and chloride ions to form a mercury chloride complex, the masking effect of the mercury sulfate is limited, a small amount of chloride ions still react with potassium dichromate, the potassium dichromate is consumed, the accuracy of the detection result is influenced, and particularly in the water sample with high chlorine and low COD, the deviation of the CODcr result caused by incomplete masking of the chloride ions is particularly remarkable. In addition, the added sulfuric acid-silver sulfate during digestion can form silver chloride precipitate with chloride ions to take away a part of organic suspended matters, so that the detection result of CODcr is inaccurate. The above problems are to be solved.
Disclosure of Invention
In order to solve the technical problems, the technical scheme adopted by the application is to provide an accurate detection method for COD in a high-chlorine low-COD water sample, so as to solve the technical problems of inaccurate detection result and lower detection precision of the existing COD detection method.
The embodiment of the application provides an accurate detection method for COD in a high-chlorine low-COD water sample, which comprises the following steps:
(1) Pretreatment: judging the type of a water sample, if the water sample is a clear water sample, measuring the chloride ion concentration of the water sample by adopting a potassium chromate indicator method, resampling, adding soluble silver salt according to the chloride ion concentration to precipitate and remove chlorine so that the chloride ion concentration is less than or equal to 1000mg/L, and filtering to obtain a filtrate to be tested; if the water sample is turbid, determining the chloride ion concentration by adopting a potassium chromate indicator method, determining the dilution factor of the water sample according to the chloride ion concentration to ensure that the chloride ion concentration is less than or equal to 1000mg/L, resampling, and preparing a sample to be tested according to the dilution factor;
(2) Rough measurement: taking distilled water as a blank sample, adopting a dichromate method to digest the sample to be detected and the blank sample, then adopting a ferrous sulfate indicator method and a ferrous ammonium sulfate standard solution to titrate the sample to be detected and the blank sample, and calculating to obtain the COD concentration of the sample to be detected;
(3) And (3) supplementing: judging whether the COD concentration of the sample to be detected in the step (2) is lower, if so, re-taking the sample to be detected and the blank, respectively supplementing the carbon straight-chain compound into the sample to be detected and the blank, repeating the operation of the step (2), calculating the COD concentration of the sample to be detected after supplementing the carbon straight-chain compound, and calculating the COD concentration of the sample to be detected before supplementing the carbon straight-chain compound according to the following formula:
wherein: a is that 1 The COD concentration of the sample to be detected before supplementing the carbon straight-chain compound is mg/L;
A 2 the COD concentration of the sample to be detected after the carbon straight-chain compound is added is mg/L;
A 0 converting the amount of the carbon linear compound to a converted value in mg/L in order to calculate the amount of oxygen consumption by completely oxidizing the carbon linear compound;
(4) And (3) calculating: and (3) calculating the COD concentration of the water sample according to the COD concentration and dilution factor of the sample to be detected before the carbon linear compound is added in the step (3).
Preferably, in the step (1), the pretreatment process of the clear water sample specifically comprises the following steps: regulating the pH value of a water sample to be neutral by using a sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator, dropwise adding a silver nitrate solution for titration, continuously shaking until brick red precipitation appears, recording the titration volume, and calculating the chloride ion concentration of the water sample; and then, taking the water sample again, adding soluble silver salt to precipitate according to the chloride ion concentration of the water sample to remove chlorine, so that the chloride ion concentration is less than or equal to 1000mg/L, and filtering to obtain a filtrate to obtain a sample to be detected.
Preferably, in the step (1), the concentration of the sodium hydroxide standard solution is 10g/L; the concentration of the potassium chromate indicator is 50g/L; the concentration of the silver nitrate solution is 0.141mol/L; the soluble silver salt is any one of solid silver nitrate and solid silver fluoride.
Preferably, in the step (1), the pretreatment process of the turbid water sample specifically comprises the following steps: and regulating the pH value of the water sample to be neutral by using a sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator, dropwise adding silver nitrate solution for titration, continuously shaking until brick red precipitation appears, recording the titration volume, calculating the chloride ion concentration of the water sample, determining the dilution factor of the water sample according to the chloride ion concentration to ensure that the chloride ion concentration is less than or equal to 1000mg/L, then re-taking the water sample, and adding deionized water according to the dilution factor for dilution to obtain the sample to be measured.
Preferably, in the step (1), the concentration of the sodium hydroxide standard solution is 10g/L; the concentration of the potassium chromate indicator is 50g/L; the concentration of the silver nitrate solution was 0.141mol/L.
Preferably, in the step (2), the specific operation process of rough measurement is as follows: taking distilled water as a blank sample, respectively and sequentially adding a mercury sulfate standard solution, a potassium dichromate standard solution and a silver sulfate-sulfuric acid standard solution into the sample to be tested and the blank sample, shaking uniformly, heating to slow boiling, and carrying out heat preservation treatment; then cooling to normal temperature, respectively dripping 3 drops of a ferrous sulfate indicator into a sample to be detected and a blank sample, dripping a ferrous ammonium sulfate standard solution for titration until the color is changed from yellow to reddish brown from blue-green, recording the titration volume, and calculating the COD concentration of the sample to be detected according to the following formula:
wherein: a is the COD concentration of the sample to be detected, mg/L;
c is the concentration of the standard solution of ferrous ammonium sulfate and mol/L;
V 0 the volume of the standard solution of ferrous ammonium sulfate consumed by the blank sample is mL;
V 1 the volume of the standard solution of ferrous ammonium sulfate consumed by the sample to be detected is mL;
V 2 is the volume of the sample to be measured, mL;
8000 is 1/4O 2 Converted values in mg/L of the molar mass.
Preferably, in the step (2), the concentration of the mercury sulfate standard solution is 100g/L; the concentration of the potassium dichromate standard solution is 0.25mol/L; the concentration of the silver sulfate-sulfuric acid standard solution is 10g/L; the volume ratio of the sample to be tested to the mercury sulfate standard solution, the potassium dichromate standard solution and the silver sulfate-sulfuric acid standard solution is 10:2:5:15; heating to 160-170 ℃ to boil, and preserving heat for 120min.
Preferably, in the step (2), the configuration process of the ferron indicator comprises the following steps: dissolving 0.7g of ferrous sulfate heptahydrate in 50mL of water, adding 1.5g of 1, 10-phenanthroline, stirring until the ferrous sulfate heptahydrate is dissolved, and diluting the ferrous sulfate heptahydrate with deionized water to 100mL to obtain the aqueous solution; the concentration of the standard solution of ferrous ammonium sulfate is 0.05mol/L.
Preferably, in the step (3), the COD concentration of the sample to be detected is lower than 100 mg/L.
Preferably, in the step (3), the carbon straight-chain compound is any one of ethylene glycol, formamide or acetamide; the amount of the carbon straight-chain compound added is 50-750 mg/L in terms of mg/L, wherein when the carbon straight-chain compound is ethylene glycol, the 1mg/L ethylene glycol is 1.29mg/L; when the straight-chain carbon compound is formamide, the conversion value of 1mg/L formamide is 0.35mg/L; when the carbon straight-chain compound is acetamide, the conversion value of 1mg/L of acetamide is 1.08mg/L.
The invention provides an accurate detection method of COD in a high-chlorine low-COD water sample, which comprises the steps of firstly carrying out precipitation chlorine removal or dilution on the water sample, reducing the concentration of chloride ions to 1000mg/L or below, then adding a carbon straight-chain compound, calculating according to the mode that the carbon straight-chain compound is completely oxidized and converted into oxygen consumption, subtracting the conversion value of the carbon straight-chain compound from the COD concentration of the sample to be detected after adding the carbon straight-chain compound, obtaining the COD concentration of the sample to be detected before adding the carbon straight-chain compound, multiplying the COD concentration by the dilution multiple, and finally obtaining the COD concentration of the water sample;
compared with the prior art, the invention has the beneficial effects that:
(1) According to the method, the clear water sample is subjected to precipitation and chlorine removal, and the turbid water sample is diluted, so that the concentration of chloride ions in the water sample is reduced to 1000mg/L or lower, the influence of the chloride ions on the CODcr detection result is reduced, the accuracy and stability of the detection result are improved, namely the detection precision is improved, and the method has important significance for accurately measuring the high-chlorine low-COD water sample;
(2) According to the invention, the carbon straight-chain compound is added, so that detection errors caused by taking away organic suspended matters by silver chloride precipitation are compensated, the detection precision is improved, the application range is increased, the method is suitable for clear water samples and turbid water samples, and the method has high industrial application feasibility.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly introduce the drawings that are needed in the embodiments or the description of the prior art, it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a process flow diagram of the accurate detection method of COD in a high-chlorine low-COD water sample.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application. The raw materials and the devices used in the invention are conventional commercial products unless specified, and the methods used in the invention are conventional methods unless specified.
(one) clear water sample
Example 1
The embodiment provides an accurate detection method for COD in a high-chlorine low-COD water sample, which comprises the following steps:
(1) Pretreatment: quantitatively weighing 100mL of water sample, regulating the pH of the water sample to be neutral by using a 10g/L sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator with the concentration of 50g/L, dropwise adding 0.141mol/L silver nitrate solution for titration, continuously shaking uniformly until brick red precipitation appears, recording the titration volume, and calculating the chloride ion concentration of the water sample to be 68022.52mg/L;
taking a water sample again, adding 32.60g of solid silver nitrate to precipitate according to the chloride ion concentration of the water sample to remove chlorine, filtering, taking filtrate, repeating the operation, calculating the chloride ion concentration of the filtrate to be 87mg/L, and meeting the requirement that the chloride ion concentration of the filtrate is less than or equal to 1000 mg/L;
and (3) taking the water again, adding 32.60g of solid silver nitrate to precipitate for chlorine removal, filtering, and taking filtrate to obtain a sample to be detected.
(2) Rough measurement: taking distilled water as a blank, quantitatively weighing 10mL of a sample to be measured and 10mL of the blank, sequentially adding 2mL of a mercury sulfate standard solution with the concentration of 100g/L, 5mL of a potassium dichromate standard solution with the concentration of 0.25mol/L and 15mL of a silver sulfate-sulfuric acid standard solution with the concentration of 10g/L into the sample to be measured and the blank respectively, shaking uniformly, heating to 165 ℃ for slow boiling, and preserving heat for 120min for digestion;
then cooling to normal temperature, respectively dripping 3 drops of a ferrous sulfate indicator into a sample to be detected and a blank, dripping a ferrous sulfate ammonium standard solution with the concentration of 0.05mol/L for titration until the color is changed from yellow to reddish brown from blue-green, recording the titration volume, and calculating the COD concentration of the sample to be detected to be 87.25mg/L according to the following formula;
wherein: a is the COD concentration of the sample to be detected, mg/L;
c is the concentration of the standard solution of ferrous ammonium sulfate and mol/L;
V 0 the volume of the standard solution of ferrous ammonium sulfate consumed by the blank sample is mL;
V 1 the volume of the standard solution of ferrous ammonium sulfate consumed by the sample to be detected is mL;
V 2 is the volume of the sample to be measured, mL;
8000 is 1/4O 2 Converted values in mg/L of the molar mass.
(3) And (3) supplementing: judging that the COD concentration of the sample to be detected calculated in the step (2) is 87.25mg/L and less than 100mg/L, taking 1L of the sample to be detected and 1L of the blank sample, respectively adding 388mg of glycol into the sample to be detected and the blank sample according to 388mg/L, stirring for 10min, taking 10mL of the sample to be detected and 10mL of the blank sample after adding the carbon straight-chain compound, repeating the operation of the step (2), calculating to obtain the COD concentration of the sample to be detected after adding the carbon straight-chain compound, namely 552.80mg/L, and calculating the COD concentration of the sample to be detected before adding the carbon straight-chain compound according to the following formula, namely 52.28mg/L;
wherein: a is that 1 The COD concentration of the sample to be detected before supplementing the carbon straight-chain compound is mg/L;
A 2 the COD concentration of the sample to be detected after the carbon straight-chain compound is added is mg/L;
A 0 the amount of the carbon linear compound added was converted to a conversion value in mg/L so that the carbon linear compound was completely oxidized to convert the amount to oxygen consumption, wherein when the carbon linear compound was ethylene glycol, the conversion value of 1mg/L of ethylene glycol was 1.29mg/L.
(4) And (3) calculating: and (3) calculating the COD concentration of the water sample according to the COD concentration and dilution factor (the dilution factor is 1 times when the clear water sample is not diluted) of the sample to be detected before the carbon linear compound is added, which are calculated in the step (3), wherein the COD concentration of the water sample is 52.28mg/L.
Example 2
The difference between the implementation method and the example 1 is that in the step (3), glycol is respectively added into the sample to be detected and the blank sample according to the amount of 78mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 151.69mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is 51.07mg/L, and the COD concentration of the water sample is 51.07mg/L.
Example 3
The difference between the implementation method and the example 1 is that in the step (3), ethylene glycol is respectively added into the sample to be detected and the blank sample according to the amount of 543mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 750.84mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is 50.37mg/L, and the COD concentration of the water sample is 50.37mg/L.
Example 4
The difference between the method and example 1 is that in the step (3), formamide (converted value of 1mg/L formamide is 0.35mg/L when the straight-chain carbon compound is formamide) is added to the sample to be tested and the blank sample according to the amount of 1428mg/L, the COD concentration of the sample to be tested after the straight-chain carbon compound is added is 551.21mg/L by calculation, the COD concentration of the sample to be tested before the straight-chain carbon compound is added is 51.41mg/L by calculation, and the COD concentration of the water sample is 51.41mg/L by calculation.
Example 5
The difference between the implementation method and the example 4 is that in the step (3), formamide is respectively added into the sample to be detected and the blank sample according to the amount of 285mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 151.65mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is calculated to be 51.90mg/L, and the COD concentration of the water sample is finally calculated to be 51.90mg/L.
Example 6
The difference between the implementation method and the example 4 is that in the step (3), formamide is respectively added into the sample to be detected and the blank sample according to the amount of 2000mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 751.12mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is calculated to be 51.12mg/L, and the COD concentration of the water sample is finally calculated to be 51.12mg/L.
Example 7
The difference between the method and example 1 is that in the step (3), acetamide is added to the sample to be measured and the blank sample in an amount of 463mg/L (when the carbon straight-chain compound is acetamide, the conversion value of 1mg/L acetamide is 1.08 mg/L), the COD concentration of the sample to be measured after the carbon straight-chain compound is added is 552.10mg/L, the COD concentration of the sample to be measured before the carbon straight-chain compound is added is 52.06mg/L, and finally the COD concentration of the water sample is 52.06mg/L.
Example 8
The difference between the implementation method and the example 7 is that in the step (3), acetamide is respectively added into the sample to be detected and the blank sample according to the amount of 92mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon-added straight-chain compound is obtained by calculation is 151.59mg/L, the COD concentration of the sample to be detected before the carbon-added straight-chain compound is 52.23mg/L, and the COD concentration of the water sample is 52.23mg/L.
Example 9
The difference between the implementation method and the example 7 is that in the step (3), acetamide is respectively added into the sample to be detected and the blank sample according to the amount of 648mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon-added straight-chain compound is obtained by calculation is 751.79mg/L, the COD concentration of the sample to be detected before the carbon-added straight-chain compound is calculated again to be 51.95mg/L, and the COD concentration of the water sample is finally calculated to be 51.95mg/L.
Comparative example 1
The implementation method adopts a 6B-1800 type chemical oxygen demand tester to test the water sample, and comprises the following specific operation processes: respectively measuring 3mL of water sample and 3mL of blank sample in a test tube, respectively adding COD specific detection reagent, shaking uniformly, and putting the test tube into a digestion hole to be digested for 10min at 165 ℃; after digestion is completed, taking out test tubes, putting the test tubes into a test tube rack, cooling for 2min according to regular air, adding 3mL of distilled water into each test tube after cooling is completed, covering the test tubes tightly, shaking the test tubes uniformly, putting the test tubes into a water tank, cooling the test tubes with water for 2min according to regular water, pouring the solution in the test tubes into a 3cm glass cuvette after cooling, and putting the test tubes into a 6B-1800 type chemical oxygen demand tester for measurement, wherein the COD concentration of a water sample is measured to be 50.23mg/L.
Comparative example 2
Taking 10mL of water sample, detecting the water sample after precipitation and chlorine removal by an online COD detector, and measuring the COD concentration of the water sample to be 49.51mg/L.
In order to more intuitively compare the COD concentration detection results of the water samples of examples 1 to 9 and comparative examples 1 to 2, the following Table 1 was formed.
TABLE 1 COD concentration detection results of water samples of examples 1 to 9 and comparative examples 1 to 2
As can be seen from Table 1, after the addition of the carbon straight-chain compound, the COD concentration value of the detected clear water sample is relatively close to the detection values of the 6B-1800 type chemical oxygen demand tester and the online COD detector, so that the detection method of the application has more accurate detection results of COD in the clear water sample.
(II) turbid water sample
Example 10
The embodiment provides an accurate detection method for COD in a high-chlorine low-COD water sample, which comprises the following steps:
(1) Pretreatment: quantitatively weighing 100mL of water sample, regulating the pH of the water sample to be neutral by using a 10g/L sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator with the concentration of 50g/L, dropwise adding 0.141mol/L silver nitrate solution for titration, continuously shaking uniformly until brick red precipitation appears, recording the titration volume, and calculating the chloride ion concentration of the water sample to be 59644.23mg/L;
determining the dilution multiple of the water sample to be 100 times according to the chloride ion concentration, so that the diluted water sample meets the requirement that the chloride ion concentration is less than or equal to 1000 mg/L;
and (4) re-sampling the water, and adding deionized water according to the dilution multiple for dilution to obtain a sample to be measured.
(2) Rough measurement: taking distilled water as a blank, quantitatively weighing 10mL of a sample to be measured and 10mL of the blank, sequentially adding 2mL of a mercury sulfate standard solution with the concentration of 100g/L, 5mL of a potassium dichromate standard solution with the concentration of 0.25mol/L and 15mL of a silver sulfate-sulfuric acid standard solution with the concentration of 10g/L into the sample to be measured and the blank respectively, shaking uniformly, heating to 165 ℃ for slow boiling, and preserving heat for 120min for digestion;
then cooling to normal temperature, respectively dripping 3 drops of a ferrous sulfate indicator into a sample to be detected and a blank, dripping a ferrous sulfate ammonium standard solution with the concentration of 0.05mol/L for titration until the color is changed from yellow to reddish brown from blue-green, recording the titration volume, and calculating the COD concentration of the sample to be detected to be 92.12mg/L according to the following formula;
wherein: a is the COD concentration of the sample to be detected, mg/L;
c is the concentration of the standard solution of ferrous ammonium sulfate and mol/L;
V 0 the volume of the standard solution of ferrous ammonium sulfate consumed by the blank sample is mL;
V 1 the volume of the standard solution of ferrous ammonium sulfate consumed by the sample to be detected is mL;
V 2 is the volume of the sample to be measured, mL;
8000 is 1/4O 2 Converted values in mg/L of the molar mass.
(3) And (3) supplementing: judging that the COD concentration of the sample to be detected calculated in the step (2) is 92.12mg/L less than 100mg/L, taking 1L of the sample to be detected and 1L of the blank sample, respectively adding 388mg of ethylene glycol into the sample to be detected and the blank sample according to 388mg/L, stirring for 10min, taking 10mL of the sample to be detected and 10mL of the blank sample after adding the carbon straight-chain compound, repeating the operation of the step (2), calculating to obtain the COD concentration of the sample to be detected after adding the carbon straight-chain compound, namely 554.20mg/L, and calculating the COD concentration of the sample to be detected before adding the carbon straight-chain compound according to the following formula, namely 53.68mg/L;
wherein: a is that 1 The COD concentration of the sample to be detected before supplementing the carbon straight-chain compound is mg/L;
A 2 the COD concentration of the sample to be detected after the carbon straight-chain compound is added is mg/L;
A 0 the amount of the carbon linear compound added was converted to a conversion value in mg/L so that the carbon linear compound was completely oxidized to convert the amount to oxygen consumption, wherein when the carbon linear compound was ethylene glycol, the conversion value of 1mg/L of ethylene glycol was 1.29mg/L.
(4) And (3) calculating: and (3) calculating the COD concentration of the water sample according to the COD concentration and the dilution factor of the sample to be detected before the carbon linear compound is added, which are calculated in the step (3), wherein the COD concentration of the water sample is 5368mg/L.
Example 11
The difference between the implementation method and the example 10 is that in the step (3), glycol is respectively added into the sample to be detected and the blank sample according to the amount of 78mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 152.32mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is 51.70mg/L, and the COD concentration of the water sample is 5170mg/L.
Example 12
The difference between the implementation method and the example 10 is that in the step (3), ethylene glycol is respectively added into the sample to be detected and the blank sample according to the amount of 543mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 752.14mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is calculated again to be 51.67mg/L, and the COD concentration of the water sample is finally calculated to be 5167mg/L.
Example 13
In the present embodiment, unlike in example 10, in step (3), formamide (converted value of 1mg/L formamide is 0.35mg/L when the carbon straight-chain compound is formamide) was added to the sample and the blank, and the other steps were the same, the COD concentration of the sample after adding the carbon straight-chain compound was calculated to be 552.71mg/L, the COD concentration of the sample before adding the carbon straight-chain compound was calculated to be 52.91mg/L, and the COD concentration of the water sample was finally calculated to be 5291mg/L.
Example 14
The difference between the implementation method and the example 13 is that in the step (3), formamide is respectively added into the sample to be detected and the blank sample according to the amount of 285mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 152.13mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is 52.38mg/L, and the COD concentration of the water sample is 5238mg/L.
Example 15
The difference between the implementation method and the example 13 is that in the step (3), formamide is respectively added into the sample to be detected and the blank sample according to the amount of 2000mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is 752.61mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is 52.61mg/L, and the COD concentration of the water sample is 5261mg/L.
Example 16
The difference between the method and example 10 is that in the step (3), acetamide is added to the sample to be measured and the blank sample in an amount of 463mg/L (when the carbon straight-chain compound is acetamide, the conversion value of 1mg/L acetamide is 1.08 mg/L), and the other steps are the same, the COD concentration of the sample to be measured after adding the carbon straight-chain compound is calculated to be 553.47mg/L, the COD concentration of the sample to be measured before adding the carbon straight-chain compound is calculated to be 53.43mg/L, and finally the COD concentration of the water sample is calculated to be 5343mg/L.
Example 17
The difference between the implementation method and the example 16 is that in the step (3), acetamide is respectively added into the sample to be detected and the blank sample according to the amount of 92mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon straight-chain compound is added is calculated to be 152.15mg/L, the COD concentration of the sample to be detected before the carbon straight-chain compound is added is calculated to be 52.79mg/L, and the COD concentration of the water sample is finally calculated to be 5279mg/L.
Example 18
The difference between the implementation method and the example 16 is that in the step (3), acetamide is respectively added into the sample to be detected and the blank sample according to the amount of 648mg/L, the other steps are the same, the COD concentration of the sample to be detected after the carbon-added straight-chain compound is obtained by calculation is 752.91mg/L, the COD concentration of the sample to be detected before the carbon-added straight-chain compound is calculated to be 53.07mg/L, and the COD concentration of the water sample is calculated to be 5307mg/L.
Comparative example 3
The specific operation process of the method is the same as that of comparative example 1, except that the water sample in the method is a turbid water sample, and the COD concentration of the water sample is 5235mg/L.
Comparative example 4
Taking 10mL of water sample, detecting the water sample after precipitation and chlorine removal by an online COD detector, and measuring the COD concentration of the water sample to be 5122mg/L.
In order to more intuitively compare the COD concentration detection results of the water samples of examples 10 to 18 and comparative examples 3 to 4, the following Table 2 was now formed.
TABLE 2 COD concentration detection results of the water samples of examples 10 to 18 and comparative examples 3 to 4
As can be seen from Table 2, after the addition of the carbon straight-chain compound, the COD concentration value of the detected turbid water sample is relatively close to the detection values of the 6B-1800 type chemical oxygen demand tester and the online COD detector, so that the detection method of the application has more accurate detection results of COD in the turbid water sample.
The invention provides an accurate detection method of COD in a high-chlorine low-COD water sample, which comprises the steps of firstly carrying out precipitation chlorine removal or dilution on the water sample, reducing the concentration of chloride ions to 1000mg/L or below, then adding a carbon straight-chain compound, calculating according to the mode that the carbon straight-chain compound is completely oxidized and converted into oxygen consumption, subtracting the conversion value of the carbon straight-chain compound from the COD concentration of the sample to be detected after adding the carbon straight-chain compound, obtaining the COD concentration of the sample to be detected before adding the carbon straight-chain compound, multiplying the COD concentration by the dilution multiple, and finally obtaining the COD concentration of the water sample;
compared with the prior art, (1) the method reduces the chloride ion concentration in the water sample to 1000mg/L or below by carrying out precipitation chlorine removal on the clear water sample and dilution on the turbid water sample, reduces the influence of chloride ions on the CODcr detection result, improves the accuracy and stability of the detection result, namely improves the detection precision, and has important significance for accurately measuring the water sample with high chlorine and low COD; (2) According to the invention, the carbon straight-chain compound is added, so that detection errors caused by taking away organic suspended matters by silver chloride precipitation are compensated, the detection precision is improved, the application range is improved, the method is suitable for clear water samples and turbid water samples, and the industrial application feasibility is high; can be widely applied to the technical field of analysis and detection.
It should be noted that:
(1) In examples 1 to 9, the solid silver nitrate was used as the soluble silver salt, and the soluble silver salt may be any one of solid silver nitrate and solid silver fluoride, and may be other soluble solid silver salts as long as it has a function of precipitating to remove chlorine; the addition amount of the soluble silver salt was calculated according to the following formula:
wherein: m is the addition amount of solid silver nitrate, g;
c is the chloride ion concentration of the water sample, mg/L;
v is the volume of a water sample, and L;
M 1 35.45 relative to the atomic mass of chlorine;
M 2 the molecular weight of the soluble silver salt was 169.87 for silver nitrate and 126.88 for silver fluoride.
(2) In examples 1 to 18, the digestion reaction was carried out by heating to 165℃and boiling slowly, and the digestion temperature was adjusted according to the actual conditions in actual production, and the digestion temperature was usually 160 to 170 ℃.
(3) In the above examples 1 to 18, the configuration process of the test ferritin indicator was as follows: 0.7g of ferrous sulfate heptahydrate is dissolved in 50mL of water, 1.5g of 1, 10-phenanthroline is added, and the mixture is stirred until the mixture is dissolved, and then the mixture is diluted to 100mL by deionized water to obtain the aqueous solution.
(4) In examples 1 to 18, ethylene glycol, formamide and acetamide were used as the carbon-linear compound, and the carbon-linear compound may be any of ethylene glycol, formamide and acetamide, or may be any other type of carbon-linear compound which is easily oxidized completely and has a high boiling point, and the purity of the carbon-linear compound is analytically pure.
(5) In examples 1 to 18, the conversion ratio of the carbon linear compound to the oxygen consumption by complete oxidation was derived from the data disclosed in the "organic chemical oxygen demand conversion Table".
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (8)
1. The accurate detection method of the COD in the high-chlorine low-COD water sample is characterized by comprising the following steps of:
(1) Pretreatment: judging the type of a water sample, if the water sample is a clear water sample, measuring the chloride ion concentration of the water sample by adopting a potassium chromate indicator method, resampling, adding soluble silver salt according to the chloride ion concentration to precipitate and remove chlorine so that the chloride ion concentration is less than or equal to 1000mg/L, and filtering to obtain a filtrate to be tested; if the water sample is turbid, determining the chloride ion concentration by adopting a potassium chromate indicator method, determining the dilution factor of the water sample according to the chloride ion concentration to ensure that the chloride ion concentration is less than or equal to 1000mg/L, resampling, and preparing a sample to be tested according to the dilution factor;
(2) Rough measurement: taking distilled water as a blank sample, adopting a dichromate method to digest the sample to be detected and the blank sample, then adopting a ferrous sulfate indicator method and a ferrous ammonium sulfate standard solution to titrate the sample to be detected and the blank sample, and calculating to obtain the COD concentration of the sample to be detected;
(3) And (3) supplementing: judging whether the COD concentration of the sample to be detected in the step (2) is lower, if so, re-taking the sample to be detected and the blank, respectively supplementing the carbon straight-chain compound into the sample to be detected and the blank, repeating the operation of the step (2), calculating the COD concentration of the sample to be detected after supplementing the carbon straight-chain compound, and calculating the COD concentration of the sample to be detected before supplementing the carbon straight-chain compound according to the following formula:
wherein: a is that 1 The COD concentration of the sample to be detected before supplementing the carbon straight-chain compound is mg/L;
A 2 the COD concentration of the sample to be detected after the carbon straight-chain compound is added is mg/L;
A 0 converting the amount of the carbon linear compound to a converted value in mg/L in order to calculate the amount of oxygen consumption by completely oxidizing the carbon linear compound;
(4) And (3) calculating: according to the COD concentration and dilution factor of the sample to be detected before the carbon linear compound is added in the step (3), calculating the COD concentration of the water sample;
in the step (3), the COD concentration of the sample to be detected is lower than 100 mg/L;
the carbon straight-chain compound is any one of ethylene glycol, formamide or acetamide; the amount of the carbon straight-chain compound added is 50-750 mg/L in terms of mg/L, wherein when the carbon straight-chain compound is ethylene glycol, the 1mg/L ethylene glycol is 1.29mg/L; when the straight-chain carbon compound is formamide, the conversion value of 1mg/L formamide is 0.35mg/L; when the carbon straight-chain compound is acetamide, the conversion value of 1mg/L of acetamide is 1.08mg/L.
2. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 1, wherein in the step (1), the pretreatment process of the clear water sample is specifically as follows:
regulating the pH value of a water sample to be neutral by using a sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator, dropwise adding a silver nitrate solution for titration, continuously shaking until brick red precipitation appears, recording the titration volume, and calculating the chloride ion concentration of the water sample; and then, taking the water sample again, adding soluble silver salt to precipitate according to the chloride ion concentration of the water sample to remove chlorine, so that the chloride ion concentration is less than or equal to 1000mg/L, and filtering to obtain a filtrate to obtain a sample to be detected.
3. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 2, wherein in the step (1), the concentration of the sodium hydroxide standard solution is 10g/L; the concentration of the potassium chromate indicator is 50g/L; the concentration of the silver nitrate solution is 0.141mol/L; the soluble silver salt is any one of solid silver nitrate and solid silver fluoride.
4. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 1, wherein in the step (1), the pretreatment process of the turbid water sample is specifically as follows:
and regulating the pH value of the water sample to be neutral by using a sodium hydroxide standard solution, dropwise adding 1 drop of potassium chromate indicator, dropwise adding silver nitrate solution for titration, continuously shaking until brick red precipitation appears, recording the titration volume, calculating the chloride ion concentration of the water sample, determining the dilution factor of the water sample according to the chloride ion concentration to ensure that the chloride ion concentration is less than or equal to 1000mg/L, then re-taking the water sample, and adding deionized water according to the dilution factor for dilution to obtain the sample to be measured.
5. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 4, wherein in the step (1), the concentration of the sodium hydroxide standard solution is 10g/L; the concentration of the potassium chromate indicator is 50g/L; the concentration of the silver nitrate solution was 0.141mol/L.
6. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 1, wherein in the step (2), the specific operation process of rough measurement is as follows:
taking distilled water as a blank sample, respectively and sequentially adding a mercury sulfate standard solution, a potassium dichromate standard solution and a silver sulfate-sulfuric acid standard solution into the sample to be tested and the blank sample, shaking uniformly, heating to slow boiling, and carrying out heat preservation treatment; then cooling to normal temperature, respectively dripping 3 drops of a ferrous sulfate indicator into a sample to be detected and a blank sample, dripping a ferrous ammonium sulfate standard solution for titration until the color is changed from yellow to reddish brown from blue-green, recording the titration volume, and calculating the COD concentration of the sample to be detected according to the following formula:
wherein: a is the COD concentration of the sample to be detected, mg/L;
c is the concentration of the standard solution of ferrous ammonium sulfate and mol/L;
V 0 the volume of the standard solution of ferrous ammonium sulfate consumed by the blank sample is mL;
V 1 the volume of the standard solution of ferrous ammonium sulfate consumed by the sample to be detected is mL;
V 2 is the volume of the sample to be measured, mL;
8000 is 1/4O 2 Converted values in mg/L of the molar mass.
7. The method for accurately detecting COD in a high-chlorine low-COD water sample according to claim 6, wherein in the step (2), the concentration of the mercury sulfate standard solution is 100g/L; the concentration of the potassium dichromate standard solution is 0.25mol/L; the concentration of the silver sulfate-sulfuric acid standard solution is 10g/L; the volume ratio of the sample to be tested to the mercury sulfate standard solution, the potassium dichromate standard solution and the silver sulfate-sulfuric acid standard solution is 10:2:5:15; heating to 160-170 ℃ to boil, and preserving heat for 120min.
8. The method for accurately detecting COD in a high chlorine low COD water sample according to claim 6, wherein in the step (2), the configuration process of the ferrioxate indicator is as follows: dissolving 0.7g of ferrous sulfate heptahydrate in 50mL of water, adding 1.5g of 1, 10-phenanthroline, stirring until the ferrous sulfate heptahydrate is dissolved, and diluting the ferrous sulfate heptahydrate with deionized water to 100mL to obtain the aqueous solution; the concentration of the standard solution of ferrous ammonium sulfate is 0.05mol/L.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311264007.XA CN116990443B (en) | 2023-09-28 | 2023-09-28 | Accurate detection method for COD in high-chlorine low-COD water sample |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311264007.XA CN116990443B (en) | 2023-09-28 | 2023-09-28 | Accurate detection method for COD in high-chlorine low-COD water sample |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116990443A CN116990443A (en) | 2023-11-03 |
| CN116990443B true CN116990443B (en) | 2024-02-06 |
Family
ID=88534262
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311264007.XA Active CN116990443B (en) | 2023-09-28 | 2023-09-28 | Accurate detection method for COD in high-chlorine low-COD water sample |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116990443B (en) |
Citations (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA874557A (en) * | 1971-06-29 | J. Overbeck Charles | Rapid field procedure for the determination of chemical oxygen demand | |
| WO2010132957A1 (en) * | 2009-05-22 | 2010-11-25 | Aqua Diagnostic Holdings Pty Ltd | Water analysis |
| CN102590464A (en) * | 2011-01-13 | 2012-07-18 | 中国石油化工股份有限公司 | Chemical oxygen demand determination method for water bodies |
| CN103645186A (en) * | 2013-12-24 | 2014-03-19 | 南京中锗科技股份有限公司 | Method for analyzing content of COD (chemical oxygen demand) in sewage with high chloride ion concentration |
| CN104020170A (en) * | 2014-06-12 | 2014-09-03 | 中国海洋石油总公司 | Method for determining chemical oxygen demand of high-chlorine waste water |
| CN104949970A (en) * | 2015-06-11 | 2015-09-30 | 郑州谱尼测试技术有限公司 | Method for measuring chemical oxygen demand of high-chlorine wastewater |
| CN105203475A (en) * | 2015-09-11 | 2015-12-30 | 中国石油化工股份有限公司 | Method of determining chemical oxygen demand in chlorine-containing water sample |
| CN105424902A (en) * | 2015-12-14 | 2016-03-23 | 北京伊普国际水务有限公司 | COD (chemical oxygen demand) determination method of high-chlorine wastewater |
| CN108732118A (en) * | 2018-08-30 | 2018-11-02 | 上海应用技术大学 | A kind of method of the Rapid Determination of COD content of high-chloride wastewater |
| CN109061041A (en) * | 2018-06-15 | 2018-12-21 | 深圳市深投环保科技有限公司 | The measuring method of the COD of waste water |
| CN110186916A (en) * | 2019-04-10 | 2019-08-30 | 成都市排水有限责任公司 | COD in a kind of water qualityCrMeasuring method |
| CN211318421U (en) * | 2019-12-27 | 2020-08-21 | 江苏旭龙水务有限公司 | Water quality on-line monitoring preprocessing device |
| CN112292599A (en) * | 2018-07-04 | 2021-01-29 | 哈希朗格有限公司 | Method for determining Chemical Oxygen Demand (COD) of high-chloride sample |
| CN113884451A (en) * | 2021-09-27 | 2022-01-04 | 乐山师范学院 | Method for measuring chemical oxygen demand in high-chlorine water |
| CN115236269A (en) * | 2022-07-18 | 2022-10-25 | 郑州航空港区明港水务有限公司 | COD (chemical oxygen demand) measuring device and using method thereof |
| CN116046487A (en) * | 2022-12-16 | 2023-05-02 | 南京水务集团有限公司 | Pretreatment method for mercury-free determination of chemical oxygen demand of high-chlorine surface water and preparation of digestion liquid |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10725011B2 (en) * | 2018-05-22 | 2020-07-28 | Saudi Arabian Oil Company | Determining chemical oxygen demand |
-
2023
- 2023-09-28 CN CN202311264007.XA patent/CN116990443B/en active Active
Patent Citations (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA874557A (en) * | 1971-06-29 | J. Overbeck Charles | Rapid field procedure for the determination of chemical oxygen demand | |
| WO2010132957A1 (en) * | 2009-05-22 | 2010-11-25 | Aqua Diagnostic Holdings Pty Ltd | Water analysis |
| CN102590464A (en) * | 2011-01-13 | 2012-07-18 | 中国石油化工股份有限公司 | Chemical oxygen demand determination method for water bodies |
| CN103645186A (en) * | 2013-12-24 | 2014-03-19 | 南京中锗科技股份有限公司 | Method for analyzing content of COD (chemical oxygen demand) in sewage with high chloride ion concentration |
| CN104020170A (en) * | 2014-06-12 | 2014-09-03 | 中国海洋石油总公司 | Method for determining chemical oxygen demand of high-chlorine waste water |
| CN104949970A (en) * | 2015-06-11 | 2015-09-30 | 郑州谱尼测试技术有限公司 | Method for measuring chemical oxygen demand of high-chlorine wastewater |
| CN105203475A (en) * | 2015-09-11 | 2015-12-30 | 中国石油化工股份有限公司 | Method of determining chemical oxygen demand in chlorine-containing water sample |
| CN105424902A (en) * | 2015-12-14 | 2016-03-23 | 北京伊普国际水务有限公司 | COD (chemical oxygen demand) determination method of high-chlorine wastewater |
| CN109061041A (en) * | 2018-06-15 | 2018-12-21 | 深圳市深投环保科技有限公司 | The measuring method of the COD of waste water |
| CN112292599A (en) * | 2018-07-04 | 2021-01-29 | 哈希朗格有限公司 | Method for determining Chemical Oxygen Demand (COD) of high-chloride sample |
| CN108732118A (en) * | 2018-08-30 | 2018-11-02 | 上海应用技术大学 | A kind of method of the Rapid Determination of COD content of high-chloride wastewater |
| CN110186916A (en) * | 2019-04-10 | 2019-08-30 | 成都市排水有限责任公司 | COD in a kind of water qualityCrMeasuring method |
| CN211318421U (en) * | 2019-12-27 | 2020-08-21 | 江苏旭龙水务有限公司 | Water quality on-line monitoring preprocessing device |
| CN113884451A (en) * | 2021-09-27 | 2022-01-04 | 乐山师范学院 | Method for measuring chemical oxygen demand in high-chlorine water |
| CN115236269A (en) * | 2022-07-18 | 2022-10-25 | 郑州航空港区明港水务有限公司 | COD (chemical oxygen demand) measuring device and using method thereof |
| CN116046487A (en) * | 2022-12-16 | 2023-05-02 | 南京水务集团有限公司 | Pretreatment method for mercury-free determination of chemical oxygen demand of high-chlorine surface water and preparation of digestion liquid |
Non-Patent Citations (6)
| Title |
|---|
| Accurate determination of low-level chemical oxygen demand using a multistep chemical oxidation digestion process for treating drinking water samples;Ma，YJ 等;Analytical Methods;第8卷(第18期);第3839-3846页 * |
| Improving quality of COD analysing using AgNO3 for wastewater samples with high chloride content;Pertiwi，T S 等;IPO Conference series：earth and environmental science;第1-8页 * |
| 化学需氧量(COD)测定中氯离子的干扰及消除方法探讨;陈辉;《北方环境》;第23卷(第12期);第146-148页 * |
| 滴定法与分光光度法测定COD比较研究;魏合芹;《资源节约与环保》(第7期);第83-85页 * |
| 银盐沉淀法快速测定火电厂高氯脱硫废水的COD;吴雨龙 等;《中国给水排水》;第30卷(第12期);第151-154页 * |
| 高氯离子低COD矿井水中COD的测定分析;李建红;《辽宁化工》;第45卷(第8期);第1112-1117页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116990443A (en) | 2023-11-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Satterfield et al. | Interferences in titanium sulfate method for hydrogen peroxide | |
| CN101713739B (en) | Reagent and method for determining chemical oxygen demand of high-chloride wastewater | |
| CN104949970A (en) | Method for measuring chemical oxygen demand of high-chlorine wastewater | |
| CN116990443B (en) | Accurate detection method for COD in high-chlorine low-COD water sample | |
| CN113504191A (en) | Method for measuring content of trace iron and aluminum in nickel-based solution | |
| CN111257503A (en) | Method for detecting chromium content of high-chromium-content aluminum alloy based on titration analysis method | |
| CN112113953A (en) | Quantitative detection method for element content in carbon composite lithium iron phosphate | |
| CN111443085A (en) | Method for rapidly detecting content of water-soluble chloride in feed | |
| CN112255225B (en) | Method for testing COD (chemical oxygen demand) of organic matters in waste hydrochloric acid containing iron | |
| CN115561186A (en) | Method for determining glucose in lithium-ion electrolytic copper foil electroplating solution | |
| CN110850026B (en) | Method for analyzing COD (chemical oxygen demand) of high-chloride acidic uranium solution | |
| CN114740144A (en) | Method for measuring iron ion concentration by full-automatic potentiometric titration | |
| Englis et al. | Spectrophotometric study of dichromate-chromic salt mixtures | |
| CN109085164B (en) | Method for accurately measuring vanadium content in vanadium-chromium hydrogen storage alloy | |
| Telep et al. | Ultraviolet Spectrophotometric Determination of Cerium | |
| CN110672786A (en) | Method for rapidly detecting COD (chemical oxygen demand) in industrial wastewater | |
| CN110426390B (en) | Method for detecting benzoyl peroxide in flour | |
| CN113252660A (en) | Method for analyzing chemical component content of high-temperature alloy corrosive liquid | |
| CN112697739A (en) | Calibration and calibration method for seawater COD sensor by spectrometry and COD sensor | |
| CN114354838B (en) | Method for measuring concentration of iron and vanadium ions in mixed solution | |
| CN110849872A (en) | Method for determining vanadium in high-content ferrovanadium alloy | |
| CN110849834A (en) | Reagent and method for determining chemical oxygen demand of sewage by rapid digestion and colorimetric determination | |
| CN110702844A (en) | Method for analyzing and determining aluminum content in organic nucleating agent by Fenton-like reagent | |
| McCrumb et al. | A new method for determining small amounts of dissolved oxygen | |
| Cartledge et al. | Determination of Cobalt as Trioxalatocobaltiate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |