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Method for detecting chemical oxygen demand of water body

A chemical oxygen demand and measurement method technology, applied in the field of environmental monitoring, can solve the problems of expensive polarography, high cost, long analysis time, etc., and achieve the effect of accurate and reliable data, short detection time and high measurement accuracy

Inactive Publication Date: 2008-10-29
王光华 +3
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  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, the standard COD detection method has obvious disadvantages when used in online detection: (1) The analysis time is too long, and the digestion and determination process takes more than 2 hours.
(2) It requires high experimental skills of the operator, which increases the probability of errors; (3) It needs to consume expensive (Ag2SO4) and toxic (HgSO4) chemical reagents, which is costly and will cause water pollution
There are also unavoidable defects in the determination of COD value by electrochemical method. For example, the coulometric method needs to be titrated, which is time-consuming and troublesome; It is the most fatal shortcoming of this method; the polarograph required by the polarographic rule is relatively expensive, and the polarograph is not suitable for further development into an online COD analyzer

Method used

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  • Method for detecting chemical oxygen demand of water body
  • Method for detecting chemical oxygen demand of water body
  • Method for detecting chemical oxygen demand of water body

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0047] Take 36ml of standard COD solution with a COD concentration of 204mg / L, and add 9mL of supporting electrolyte solution. Cover the quartz glass window with a light-shielding plate to avoid ultraviolet light from irradiating the membrane electrode; inject the sample into the reactor, let the sample stay in the reactor for 90 seconds to fully contact the sample and the membrane electrode, and record the dark current in the detection circuit when the light is shaded and the background of the ultraviolet light detection system; remove the shading plate and let the ultraviolet light irradiate the membrane electrode to generate a photoresponse current; after the photoresponse current reaches a peak value and slowly decreases and reaches a steady state, record the photoresponse current and the UV sensor detection Obtain the ultraviolet light intensity reaching the membrane electrode; use the above * formula to calculate the unit light intensity response current; check the corres...

Embodiment 2

[0053] Take 36ml of water sample with a COD concentration of 82.6mg / L, and add 9mL of supporting electrolyte solution. The measurement process is as in Example 1, and the corresponding COD is found from the standard curve as follows:

[0054]

[0055] The national standard method measures the average value of this sample to be 82.1, the relative standard deviation is 1.21%, and the sample variance is 0.99.

[0056] S 2 本机 / S 2 传统 =4.63, look up the table to get F 0.005(5) =14.94>4.63, so the difference is not significant, that is, the comparability of the two analysis methods is very good.

Embodiment 3

[0058] Take 36ml of water sample with a COD concentration of 33.1mg / L, and add 9mL of supporting electrolyte solution. The measurement process is as in Example 1, and the corresponding COD is found from the standard curve as follows:

[0059]

[0060] The national standard method measures the average value of this sample to be 31.4, the relative standard deviation is 1.35%, and the sample variance is 0.18.

[0061] S 2 本机 / S 2 传统 =13.22, look up the table to get F 0.005(5) =14.94>13.22, so the difference is not significant, that is, the comparability of the two analysis methods is very good.

[0062] Note: The above examples are all commissioned inspections conducted by Jinan Environmental Monitoring Station.

[0063] Spike Recovery

[0064] Adding a standard solution (marked as 200138) with a concentration of 19.8mg / L in the sample solution with a COD concentration of 20.0mg / L, the calculated recovery rate of addition:

[0065] serial number

[0066] Acco...

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Abstract

It is an environmental water chemical oxygen demand (COD) measurement method, particularly based on nanometer photocatalysis principle to precess the water COD measurement method. Its main feature is using specialized preparation nanometer titanium dioxide membrane electrode as the working electrode to establish three electrodes system, and after photocatalysis, generating organic matter of the hole oxidation samples, so establishing responsive current in the detection loop circuit, and simultaneously, detecting the UV intensity arrived at membrane electrode, to calculate the response current generated by the unit light intensity correlated to the COD in samples. Using the unit light intensity response current, it can calculate the COD value in the samples. The method is mainly applicable to the water quality monitoring station, the monitoring laboratory, the sewage metering station, the sewage treatment plant, the water plant, the sewage plant, the water sector monitoring points, and other units. The method has rapid detection, no secondary pollution, low maintenance, high stability and precision, strong anti-jamming ability, not sensitive to chloride ion, and other features.

Description

technical field [0001] The invention relates to a method for measuring chemical oxygen demand (COD) in environmental water, in particular to a method for measuring chemical oxygen demand (COD) in water based on the principle of nanometer photocatalysis, and belongs to the technical field of environmental monitoring. Background technique [0002] Chemical Oxygen Demand (COD for short) is one of the important technical indicators to characterize the degree of organic pollution in water bodies. At present, the standard reflux method (potassium permanganate index method and potassium dichromate oxidation method) is the most widely used COD determination method at home and abroad. The former is mainly used for the analysis of groundwater and clean surface water, while the latter is mostly used for industrial wastewater. and domestic sewage analysis. The standard reflux method has the advantages of accurate measurement results and good reproducibility, but it also has obvious dis...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N21/17G01N31/00
Inventor 冉祥成刘曦旻张文华藏传梅王成艳管清洪
Owner 王光华
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