Method of determining chemical oxygen demand in chlorine-containing water sample

Abstract

The invention discloses a method of determining chemical oxygen demand in a chlorine-containing water sample. The method comprises the following steps: first homogenizing the chlorine-containing water sample, then centrifugally separating an appropriate amount of the treated water sample at a high speed to obtain a clear solution I and a precipitate I; adding a potassium dichromate solution into the clear solution I, then gradually dropwise adding silver nitrate, precipitating chlorine ions in the clear solution I, stopping when a brick-red precipitate appears to obtain a sample I; centrifugally separating the sample I, and collecting a clear solution II; sufficiently mixing the precipitate I and the clear solution II to obtain a mixed solution, transferring an appropriate amount of the mixed solution into a digestion tank, adding the potassium dichromate solution and a silver sulfate-sulfuric acid solution, oscillating, uniformly shaking, and microwave digesting to obtain a sample II; finally cooling the sample II to the room temperature, uniformly shaking, transferring the sample II into a colorimetric tube, determining the content of trivalent chromium ions on a spectrophotometer by adopting a colorimetric method, and further calculating to obtain a COD value of the chlorine-containing water sample. The method is simple to operate, high in accuracy and capable of meeting the requirement for rapidly acquiring data in the on-situ detection.

Description

technical field [0001] The invention relates to the technical field of measuring chemical oxygen demand, in particular to a method for measuring chemical oxygen demand in chlorine-containing water samples. Background technique [0002] As an important indicator of water quality monitoring, chemical oxygen demand (COD) can reflect the relative content of organic matter in water. The higher the COD value, the more serious the pollution of reducing substances in water. In recent years, the development of industry has led to an increase in the amount of industrial wastewater. Affected by factors such as production raw materials, process flow and operating conditions, the water quality has become more complicated; coupled with increasingly stringent environmental protection requirements, COD indicators need to be checked for both effluent and recycling. accurate monitoring and control. [0003] The current national standard method for the determination of COD is the GB / T111914 d...

AI Technical Summary

Problems solved by technology

In the experiment, the traditional reflux device was replaced by rapid digestion, which is simple to operate and saves time, and the experimental equipment is easy to carry, but this method still has the problem of chloride ion interference as mentioned above

[0005] In order to solve the deficiencies in the above-mentioned technologies, CN103645186A proposes to adopt the silver salt precipitation method to eliminate the influence of high chlorine, but still needs to add mercury sulfate solution in the follow-up; although CN104020170A solves the use problem of highly toxic reagents, it needs to adopt titration method, operation The steps are cumbersome; CN103616273A provides a fast digestion method without the use of mercury salts and silver salts, but this method needs to feed inert gas, which is not suitable for determination under field conditions

At present, there is no patented technology that can not only ensure that the experimental operation is simple and suitable for field application, but also ensure that the experiment is environmentally friendly and the accuracy of the results is high.

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