Electrochemical method for measuring COD of surface water

Abstract

The invention relates to an electrochemical method for measuring COD of surface water. The electrochemical method comprises the following steps: (1) measuring background currents I1 and I2 of a background test solution consisting of deionized water and sodium sulfate under constant voltages V1 and V2; (2) measuring a response current I3 of a surface water test solution composed of surface water, deionized water and sodium sulfate under the constant voltage V1, respectively adding an organic matter capable of increasing the COD of the solution by X1 or chloride capable of increasing the chloride ion concentration of the solution by Y1, and measuring response currents I4 and I5 under the constant voltage V1; (3) according to the method in the step (2), respectively measuring the response current I6 of the surface water test solution, the response current I7 of the COD increased by X2 and the response current I8 of the chloride ion increased by Y2 under the constant voltage V2; and (4) calculating the COD value in the surface water according to a formula. The invention provides the method for measuring the response current of the surface water test solution under different conditionsby using the electrochemical device and calculating the COD value of surface water.

Description

technical field [0001] The invention belongs to the field of electrochemical measurement and relates to an electrochemical method for measuring surface water COD. Background technique [0002] As people pay more and more attention to the water environment, the demand for the measurement of surface water quality parameters is growing rapidly, especially the COD value of surface water. At present, the measurement methods of surface water COD are mainly potassium dichromate method and potassium permanganate method. The national standard method for surface water measurement is the potassium dichromate method (HJ 828-2017). Although the potassium dichromate method is more accurate, it also takes a long time. Potassium dichromate and mercury sulfate are used to determine the High lower limit (16mg / L) and other shortcomings. Potassium permanganate method is more suitable for detecting surface water with low COD, but it has disadvantages such as poor oxidation ability of potassium...

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Problems solved by technology

[0004] Studies have shown that the method of mercury sulfate shielding and silver nitrate precipitation can remove the influence of chloride ions in the solution, but because metal cations participate in the electrode reaction in the electrochemical process, which seriously affects the measurement of the response current, so this method cannot accurately measure surface water. COD value; measuring COD by measuring the concentration of chloride ions and then removing the influence of chloride ions is a more effective way to remove the influence of chloride ions. However, the common rapid measurement methods for chloride ions are not accurate, which seriously affects the measurement of COD. The analysis center The ion chromatography and silver nitrate titration method used are complex and time-consuming, and cannot meet the requirements of future on-line detection

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