Method for determining chlorine ions in vanadium electrolyte

Abstract

The invention relates to a method for determining trace chlorine ions in a vanadium electrolyte. The method comprises (A) oxidizing a vanadium electrolyte sample into pentavalent vanadium and simultaneously diluting the sample by a certain factor to obtain a pentavalent vanadium ion electrolyte, (B) putting the pentavalent vanadium ion electrolyte as a substrate solution into a colorimetric tube,adding nitric acid into the electrolyte, carrying out acidification, and adding a silver nitrate solution into the electrolyte, adding water to dilute the mixed solution and carrying out volume metering to obtain a test solution, or directly adding water to dilute the acidified electrolyte and carrying out volume metering to obtain a test solution, (C) drawing a working curve and checking a linearcorrelation coefficient of the working curve at the same time, and (D) determining the absorbance of the test solution with the silver nitrate solution obtained in step the (B), calculating the corresponding chlorine concentration through the blank test solution without the silver nitrate solution based on the absorbance according to the linear equation, and multiplying the chlorine concentrationby the dilution factor to obtain the chloride ion concentration of the vanadium electrolyte. The method can fast and accurately detect the trace chlorine ion content of the vanadium electrolyte, is easy to operate and needs unharsh experimental conditions.

Description

technical field [0001] The invention relates to a method for determining chloride ions in a vanadium electrolyte. Background technique [0002] The vanadium redox flow battery system consists of stacks, electrolyte solutions, electrolyte solution storage and supply systems, system control systems, charge and discharge systems and other parts. The core part of the system is the electrolyte and the stack. The electrolyte is composed of vanadium ions in different valence states and a certain concentration of sulfuric acid. The electrolyte circulates in the stack and flows on the porous electrodes on both sides of the ion exchange membrane. Reduction and oxidation reactions occur separately. The presence of certain impurity ions in the electrolyte will seriously affect the stability of the electrolyte, the charge and discharge efficiency of the battery, the rate of capacity decay and the life of the stack. Chloride ions are an important impurity element in the vanadium electro...

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Problems solved by technology

The molar method is more accurate for the determination of substances with higher chloride ion content, but it will cause large analysis errors for samples with low chloride ion content, and the color resolution of the titration end point is not obvious and easy to cause errors; the mercury method will produce after the experiment. Toxic mercury-containing waste liquid has a great impact on environmental pollution and the health of operators, and the color judgment of the end point of the mercury method is inaccurate

Because the potentiometric titration method uses silver nitrate standard solution for titration, the resulting silver chloride precipitate is unstable, so the measurement accuracy of this method is not high, and the silver nitrate reagent is costly and toxic, and is easy to pollute the environment; the volumetric method can be divided into nitric acid Silver volumetric method and mercury nitrate volumetric method, the silver nitrate volumetric method is a precipitation titration method, the end point color change is not sensitive, the mercury nitrate volumetric method titration end point color change is very sensitive, but the pH value of the test solution must be strictly controlled within a certain range, and the experimental conditions are harsh

These methods are not suitable for the determination of chloride ion content in vanadium electrolyte

At present, there is no literature report on the detection method of trace chloride ion content in the vanadium battery electrolyte

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