Method for measuring chemical oxygen demand of high-chlorine wastewater

Abstract

The invention discloses a method for measuring the chemical oxygen demand of high-chlorine wastewater. The method is applicable to the scope that the chemical oxygen demand (COD) is higher than or equal to 100 mg / L and the chloridion concentration is lower than or equal to 1%. When the COD and the chloridion concentration exceed the scope, the method can be available through proper dilution of a sample. The method comprises the following steps: (1) preparation of a concentrated sulfuric acid saturated copper sulfate catalyst; (2) drawing of a CODCl<-> chloridion calibration curve; (3) measurement of the chloridion content of a sample solution according to a silver nitrate titration method; (4) measurement of the total COD of the sample solution : selecting a defined amount of the sample solution for measurement of the total COD of the sample solution according to the method in step (2); (5) calculation of the difference between the total COD and CODCl<->, namely the actual COD of the sample solution. The method has the advantages that adding of mercury sulfate and silver sulfate is not needed, so that the cost is low, and secondary environmental pollution is avoided; the method is simple and easy to operate, and accurate and reliable in measurement result.

Description

technical field [0001] The invention belongs to the technical field of water quality detection, and in particular relates to a method for measuring the chemical oxygen demand of high-chlorine wastewater. technical background [0002] COD Cr It refers to the chemical oxygen demand measured with potassium dichromate as the oxidizing agent. The value of COD is measured by the potassium dichromate method, and some factors will affect the size of COD, resulting in COD Cr ≠COD, theoretically COD>COD Cr , while COD is used in practical applications Cr to represent COD. Chemical Oxygen Demand (COD Cr ) reflects the status of water pollution by reducing substances, is an important index to evaluate the degree of water pollution, and is one of the must-test items for the Ministry of Environmental Protection to implement water pollution control, energy conservation and emission reduction. The national standard method GB / T11914-1989 for the determination of chemical oxygen dema...

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Problems solved by technology

However, the conversion coefficient K of this method is an empirical coefficient. Different wastewater has different K values. It is difficult to accurately determine the size of K in practical applications.

At the same time, this method needs to add sodium azide when eliminating the interference of nitrite, which itself is highly toxic and has the risk of explosion

[0005] In addition to the above methods, there are also mercury salt method, nitrate precipitation method, sealed digestion method, bismuth absorbent method, etc., but due to serious environmental pollution, complicated operation, low accuracy and other reasons, they cannot be effectively implemented.

[0006] Aiming at the difficult problems in the determination of COD in high-chlorine wastewater at the present stage: polluting the environment, low accuracy, high cost, etc., the applicant proposed a new method for the determination of COD in high-chloride wastewater by analyzing and researching a large number of water samples

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