CN109061041A - The measuring method of the COD of waste water - Google Patents
The measuring method of the COD of waste water Download PDFInfo
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- CN109061041A CN109061041A CN201810623811.5A CN201810623811A CN109061041A CN 109061041 A CN109061041 A CN 109061041A CN 201810623811 A CN201810623811 A CN 201810623811A CN 109061041 A CN109061041 A CN 109061041A
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- 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
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- 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
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Abstract
The present invention provides a kind of measuring method of the COD (COD) of waste water, comprising: step A: wastewater sample and sulfuric acid are mixed in digestion tube open heating, make chloride ion with the volatilization of chlorination hydrogen form, obtains chloride ion content in 1000mg/L water sample below；Step B: the step A waste water obtained and sulfuric acid mixture are directly sequentially added into screening agent, digestion agent and catalyst and measure COD using closed Catalytic digestion method.Method sample of the invention avoid conventional method because in the sample after dilution causes dilution COD be less than method detection limit due to unmeasured problem.
Description
Technical field
The present invention relates to the measuring method of the COD of waste water (COD) more particularly to high chlorine (1%~13%) are low
The COD measuring method of COD (< 300mg/L) waste water.
Background technique
Waste water, such as react (temperature is up to 90 DEG C when reaction) with liquid alkaline from basic copper chloride and prepare copper oxide generation
Waste water, basic copper chloride are prepared by copper-containing etching waste solution, and the waste water is colourless, and pH value 9 or so, salinity is up to 30%, there is ammonia taste (ammonia
Nitrogen 200mg/L or so), chlorine ion concentration is up to 10% or so, and some is up to 13%.The waste water contains a certain amount of COD
(COD) (< 300mg/L) makes its COD reach IV class in GB 3838-2002 " water environment quality standard " table 1 after need to handling
Standard (COD < 30mg/L).Since chlorine ion concentration is up to 10% or more in the waste water, generated when to the measurement of COD serious dry
It disturbs and is difficult to be measured.
Excessive H is first added in a kind of measuring method proposition of existing waste water COD2SO4, temperature 70 C water-bath go dechlorination from
Son eliminates the influence of high concentration Cl ion pair COD measurement result.However such method sample has a dilution, method sensitivity decrease,
It is unsuitable for the sample measurement of the low COD of above-mentioned high chlorine.
Summary of the invention
The present invention provides a kind of high chlorine (1%~13%) with preferable accuracy and precision low COD (< 300mg/L)
The COD measuring method of waste water.
A kind of measuring method of the COD of waste water (COD) comprising: step A: wastewater sample mixes simultaneously with sulfuric acid
Opening heating makes chloride ion with the volatilization of chlorination hydrogen form, obtains chloride ion content in 1000mg/L water sample below；Step B: will
The water sample that step A is obtained measures COD using closed Catalytic digestion method.
Compared to the prior art, method sample of the invention avoids conventional method because in the sample after diluting caused by dilution
COD unmeasured problem less than method detection limit.
Specific embodiment
The measuring method of the COD (COD) for the waste water that embodiment of the present invention provides, includes the following steps:
Step A: wastewater sample is mixed with sulfuric acid and open heating, makes chloride ion with the volatilization of chlorination hydrogen form, obtain chlorine from
Sub- content is in 1000mg/L water sample below；
Step B: the water sample that step A is obtained measures COD using closed Catalytic digestion method.
The wastewater sample of present embodiment is that copper oxide produces wash water, and basic copper chloride reacts production copper oxide with liquid alkaline,
Copper oxide crude product originally water washing, resulting wash water are copper oxide production wash water.The wash water pH value 9 or so, salinity is up to
30%, have ammonia taste (ammonia nitrogen 200mg/L or so), chlorine ion concentration is up to 10% or more, and some is up to 13%.
The wastewater sample of acquisition should be placed in vial, and be analyzed as early as possible.It cannot such as analyze in time and preferably add ρ=1.84g/L
Sulfuric acid is placed at 4 DEG C and saves, the holding time is no more than 5 days to pH < 2.Present embodiment is to sample 3ml calculating.
3ml sulfuric acid solution (1 volume sulphur is added using directly taking 3ml wastewater sample in COD digestion tube in the step A
Acid: 4 volume of water) it shakes up, digestion tube is inserted into 100~165 DEG C of 60~80min of heating in COD digestion instrument, preferably 165 DEG C are spacious
Mouth heating 60min, makes chloride ion with the volatilization of chlorination hydrogen form.
It is described except chlorine process includes taking out the digestion tube gently to shake 2-3 time, dechlorination terminates after cooling moisturizing to 6ml or so simultaneously
It shakes up.
The closed Catalytic digestion method of the step B includes:
Screening agent is added under thermal condition to shake up；
Digestion agent is added to shake up；
Catalyst is added to shake up, is put into COD digestion instrument and clears up 25min；
It is transferred in conical flask after cooling, with 20-30ml water washing digestion tube and is transferred in conical flask together；
Ferroin indicator is added, is titrated with iron ammonium sulfate standard solution, makes solution colour by yellow through blue-green
Become bronzing.Record the consumption volume of iron ammonium sulfate standard solution.
The screening agent of above-mentioned addition is the mercuric sulfate (HgSO of the 100g/L of 1ml4) solution.Sulfuric acid mercury solution can be using title
10g mercuric sulfate is taken, is dissolved in 100ml sulfuric acid solution (1 volume sulfuric acid: 9 volume of water), shakes up acquisition.Under thermal condition plus shelter
Agent is to prevent analysis salt.
COD uses concentration for c (1/6K when being greater than 50mg/L2CrO7)=0.25mol/L digestion agent, when COD is greater than 50mg/L
Use concentration for c (1/6K2CrO7)=0.05mol/L digestion agent, the additional amount of digestion agent are 3ml.c(1/6K2CrO7)=
Using 12.25g potassium bichromate is weighed when 0.25mol/L, 50g aluminum aluminum sulfate and 10g ammonium molybdate are dissolved in 500ml water, are added
The 200ml concentrated sulfuric acid is transferred in 1000ml volumetric flask after cooling, is diluted with water to graticule acquisition.c(1/6K2CrO7)=
Using 2.45g potassium bichromate is weighed when 0.05mol/L, 50g aluminum aluminum sulfate and 10g ammonium molybdate are dissolved in 500ml water, are added
The 200ml concentrated sulfuric acid is transferred in 1000ml volumetric flask after cooling, is diluted with water to graticule acquisition.
Catalyst sulfuric acid silver-sulfuric acid solution the additional amount is 2.5ml, and the silver sulfate-sulfuric acid solution is used and weighed
4.4g silver sulfate is added in the 250ml concentrated sulfuric acid (ρ=1.84g/L), places 1-2 days and is allowed to dissolve, and mixes and be made, before use
Carefully shake up.Due to the sulfuric acid being added in step A, catalyst sulfuric acid silver-sulfuric acid solution dosage is without excessive herein, it is only necessary to
2.5ml can reach catalytic effect.
Wastewater sample 0.025mol/L iron ammonium sulfate standard solution of the COD greater than 50mg/L and 50ml buret are to sky
White and sample is titrated；COD is less than wastewater sample the 0.01mol/L iron ammonium sulfate standard solution and 25ml drop of 50mg/L
Determine pipe to titrate blank and sample.0.025mol/L iron ammonium sulfate standard solution is prepared: weighing 19.5g iron ammonium sulfate
[(NH4)2Fe(SO4)2·6H2O] it is dissolved in the water, it is added the 20ml concentrated sulfuric acid (ρ=1.84g/L), is diluted to after solution is cooling
2L is obtained.The preparation of 0.01mol/L iron ammonium sulfate standard solution: by the l ferrous ammonium sulfate solution water of above-mentioned 0.025mol/L
Dilute 2.5 times of acquisitions.It demarcates before use.
Ferroin indicator is using dissolution seven hydrated sulfuric acid of 0.7g Asia (FeSO4·7H2O) in 50ml water, 1.5g is added
Phen, stirring are diluted to 100ml acquisition to dissolving.
COD digestion instrument (IV type of XJ-) can be used when abovementioned steps heat；25mlCOD digestion tube can be used in digestion tube；Drop
Fixed pipe is acid buret.
Above-mentioned blank test replaces sample with 3ml water, other processes and sample treatment and continuous mode are completely the same, including
Be added reagent type and measure also consistent (including sulfuric acid, screening agent, digestion solution and catalyst).Use sulfuric acid sub- as wastewater sample
The titration of iron ammonium standard solution, records the consumption volume of iron ammonium sulfate standard solution, with the average value V of double blank titration results0
It participates in calculating.
COD is calculated according to the following formula, it need to also be multiplied by extension rate if sample has dilution.
In formula: c-l ferrous ammonium sulfate solution concentration, mol/L；
V0- bis- blank consume the average value of iron ammonium sulfate standard solution volume, ml；
V1- sample consumption iron ammonium sulfate standard solution volume, ml；
V2- sample volume, ml；
8000—1/4O2Scaled value of the molal weight as unit of mg/L.
In precision control, every batch of sample Duplicate Samples must not be less than 10%, and the relative deviation of Duplicate Samples must not exceed ±
10% (more than lower limit of quantitation).Chloride ion content in measurement sample is needed before measuring sample, if chloride ion content is more than 13%
It needs to investigate whether chloride ion content reaches 1000mg/L hereinafter, otherwise measurement result can be made higher after dechlorination.Preferably through height
The industrial wastewater of (80 DEG C or more) processing of temperature or technique and chloride ion content up to 1%~13%.For containing volatilization in sample
Property organic matter, thermally labile organic matter it is not applicable.
Parallel dechlorination experiment is carried out to the sample containing chlorine 13% according to the above method, chloride ion average content 748mg/L (presses body
Product 3ml is calculated, RSD%=10.9, n=6), measurement result is shown in Table 1.
1 copper oxide of table produces chlorinity (calculating by volume 3ml) after waste water dechlorination
There is good accuracy and precision to the measurement result of standard specimen according to the above method.With primary standard substance O-phthalic
Potassium hydrogen phthalate (KHC8H4O4) and sodium chloride preparation standard specimen (COD100mg/L, Cl content 9%), the mark is measured in parallel using this method
The average result of sample COD is 101mg/L (RSD%=3.42, n=6), and measurement result is shown in Table 2.
The COD measurement result of 2 standard specimen of table (COD100mg/L, Cl content 9%)
There is good accuracy and precision to the measurement result of raw water.It is measured in parallel raw water COD's using this method
Average result is 155mg/L (RSD%=2.69, n=11), and measurement result is shown in Table 3.
The COD measurement result of 3 raw water of table
| Serial number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | It is average | SD | RSD |
| COD(mg/L) | 164 | 156 | 157 | 154 | 157 | 150 | 150 | 157 | 150 | 157 | 155 | 155 | 4.17 | 2.69% |
Mark-on test: taking 3ml sample in 25mlCOD digestion tube, and 1ml COD500mg/L is added, and scalar quantity is
166.7mg/L (is calculated) by 3ml volume, measures COD according to the above method, and mark-on sample average measurement result is 334mg/L (RSD%
=2.18, n=9), recovery of standard addition average result is 107% (RSD%=4.06, n=9), and measurement result is shown in Table 4.
4 raw water COD recovery of standard addition result of table
There is good accuracy and precision to the measurement result of processed waste water according to the above method.It is flat using this method
The average result of row measurement processed waste water COD is 5.33mg/L (RSD%=47.2, n=10), due to processed waste water COD
Near method detection limit, precision is not required measurement result.Mark-on test: take 3ml sample in 25mlCOD digestion tube
In, 1ml COD100mg/L is added, scalar quantity is 33.3mg/L (calculating by 3ml volume), measures COD, mark-on according to the above method
Sample average measurement result is 35.6mg/L (RSD%=4.17, n=10), and recovery of standard addition average result is 90.8% (RSD%
=4.90, n=10), measurement result is shown in Table 5.
5 processed waste water COD measurement result of table and recovery of standard addition result
A certain amount of sulfuric acid is added in the present invention in wastewater sample, removes chloride ion in sample in a heated condition, so that
Chloride ion content drops to 1000mg/L or less.The potassium bichromate solution for adding known quantity is urged under strong acid media with silver salt
Agent, after airtight heating resolution, using ferroin as indicator, with the dichromic acid not being reduced in iron ammonium sulfate Titration Water Sample
Potassium is calculated the mass concentration of oxygen demand by the meter of the potassium bichromate consumed.Method sample of the invention is not diluted, avoids passing
System method because dilution, such as by chlorine ion concentration be diluted to 1000mg/L or less cause dilution after sample in COD less than method inspection
Rising limit and unmeasured problem.The detection of the method for the present invention is limited to 8mg/L, Determination Limit 32mg/L, determination of the upper limit
700mg/L。
The measuring method of aforementioned disclosed chemical oxygen demand of waste water, can be in not disobeying spirit and scope of the invention
Under modified application, the present invention is simultaneously not from being limited to above-mentioned revealed embodiment.
Claims (10)
1. a kind of measuring method of the COD of waste water (COD) comprising:
Step A: wastewater sample is mixed with sulfuric acid and open heating, makes chloride ion with the volatilization of chlorination hydrogen form, obtains chloride ion and contain
Amount is in 1000mg/L water sample below；
Step B: the water sample that step A is obtained measures COD using closed Catalytic digestion method.
2. the measuring method of the COD of waste water as described in claim 1, which is characterized in that the step A is used and directly taken 3ml
Wastewater sample is added 3ml sulfuric acid and shakes up in COD digestion tube, and digestion tube is inserted into 100~165 DEG C of heating in COD digestion instrument
60~80min makes chloride ion with the volatilization of chlorination hydrogen form.
3. the measuring method of the COD of waste water as claimed in claim 2, which is characterized in that described except chlorine process includes taking out institute
It states digestion tube gently to shake, moisturizing to 6ml and shakes up after dechlorination terminates cooling.
4. the measuring method of the COD of waste water as claimed in claim 2, which is characterized in that the closed Catalytic digestion of the step B
Method includes:
1ml screening agent is added under thermal condition to shake up；
3ml digestion agent is added to shake up；
2.5ml catalyst is added to shake up, is put into COD digestion instrument and clears up 25min；
It is transferred in conical flask after cooling, with 20-30ml water washing digestion tube and is transferred in conical flask together；
Ferroin indicator is added, is titrated with iron ammonium sulfate standard solution, becomes solution colour through blue-green from yellow
Bronzing records the consumption volume of iron ammonium sulfate standard solution.
5. the measuring method of the COD of waste water as claimed in claim 4, which is characterized in that the screening agent is the 100g/L of 1ml
Sulfuric acid mercury solution.
6. the measuring method of the COD of waste water as claimed in claim 4, which is characterized in that COD is used when being greater than 50mg/L
0.25mol/L digestion agent 1/6K2CrO7, 0.05mol/L digestion agent 1/6K2CrO7 is used when COD is less than 50mg/L, digestion agent
Additional amount is 3ml.
7. the measuring method of the COD of waste water as claimed in claim 4, which is characterized in that the catalyst is silver sulfate-sulfuric acid
Solution additional amount is 2.5ml, and the silver sulfate-sulfuric acid solution is added in the 250ml concentrated sulfuric acid, puts using 4.4g silver sulfate is weighed
It sets and is allowed within 1-2 days dissolve, and mix and be made.
8. the measuring method of the COD of waste water as claimed in claim 4, which is characterized in that COD is greater than the wastewater sample of 50mg/L
Blank and sample are titrated with 0.025mol/L iron ammonium sulfate standard solution and 50ml buret；COD is less than 50mg/L
Wastewater sample blank and sample are titrated with 0.01mol/L iron ammonium sulfate standard solution and 25ml buret.
9. the measuring method of the COD of waste water as described in claim 1, which is characterized in that the detection of the method is limited to 8mg/
L, Determination Limit 32mg/L.
10. the measuring method of the COD of waste water as described in claim 1, which is characterized in that the waste water chloride ion content reaches
The waste water of 1%~13% and COD < 300mg/L.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255225A (en) * | 2020-09-25 | 2021-01-22 | 斯瑞尔环境科技股份有限公司 | Method for testing COD (chemical oxygen demand) of organic matters in iron-containing waste hydrochloric acid |
| CN115015509A (en) * | 2022-06-09 | 2022-09-06 | 江苏省环境监测中心 | Method for determining chemical oxygen demand of wastewater containing chlorine and bromine simultaneously |
| CN116990443A (en) * | 2023-09-28 | 2023-11-03 | 山东天信医药科技有限公司 | Accurate detection method for COD in high-chlorine low-COD water sample |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255225A (en) * | 2020-09-25 | 2021-01-22 | 斯瑞尔环境科技股份有限公司 | Method for testing COD (chemical oxygen demand) of organic matters in iron-containing waste hydrochloric acid |
| CN112255225B (en) * | 2020-09-25 | 2024-02-02 | 斯瑞尔环境科技股份有限公司 | Method for testing COD (chemical oxygen demand) of organic matters in waste hydrochloric acid containing iron |
| CN115015509A (en) * | 2022-06-09 | 2022-09-06 | 江苏省环境监测中心 | Method for determining chemical oxygen demand of wastewater containing chlorine and bromine simultaneously |
| CN115015509B (en) * | 2022-06-09 | 2023-08-18 | 江苏省环境监测中心 | Method for determining chemical oxygen demand of wastewater containing chlorine and bromine simultaneously |
| CN116990443A (en) * | 2023-09-28 | 2023-11-03 | 山东天信医药科技有限公司 | Accurate detection method for COD in high-chlorine low-COD water sample |
| CN116990443B (en) * | 2023-09-28 | 2024-02-06 | 山东天信医药科技有限公司 | Accurate detection method for COD in high-chlorine low-COD water sample |
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