A method for determining the iodate concentration of ammonia nitrogen-containing water during chlorine disinfection

Abstract

The present invention belongs to the field of environmental monitoring methods, and a method for determining the concentration of iodate in water disinfected by the breakpoint chlorination process is proposed. This method mainly quenches the intermediate products such as HOCl, HOI, and NH2Cl that interfere with the determination of iodate generated during the breakpoint chlorination process by adding H2O2, H2O2 enzyme, and FeSO4, and then adds an excessive amount of iodide ions under acidic conditions to react with iodate to generate I3 ‑ with a characteristic wavelength at 351 nm, and its concentration is measured using a UV spectrophotometer. By using this method, the concentration of iodate during the breakpoint chlorination process can be effectively determined.

Description

Technical Field

[0001] The invention belongs to the field of environmental monitoring and provides a method for measuring the iodate concentration in the process of chlorine disinfection of ammonia nitrogen-containing water. Background Art

[0002] Iodine is a trace element that exists in natural water such as seawater, fresh water and rainwater. There are three main forms of iodine in nature, namely iodide, iodate and organic iodine, which may be converted into each other in the environment and during water / wastewater treatment. Wastewater must also be disinfected before discharge to inactivate microorganisms. During the disinfection process, iodide can be oxidized by disinfectants to HOI / OI - , which further reacts with organic matter in natural / wastewater to form iodinated disinfection byproducts (DBPs). Iodinated DBPs have attracted increasing attention due to their significantly higher toxicity than brominated and chlorinated analogs. Since the three iodine forms can be converted into each other, it is necessary to measure all three iodine forms in source water and wastewater to predict the iodine levels that may be involved in the formation of iodinated DBPs. Among them, iodate is the most stable and harmless form of the three iodine forms, so the determination of iodate is particularly important.

[0003] Currently, iodate determination is mainly performed by ion chromatography post-column reaction and UV / visible detection, or by converting iodate to I3 - And measure I3 - The absorbance value at 288nm or 351nm is used. However, the former requires instruments, and the equipment is complex and expensive, which is not feasible for some laboratories or fields with limited resources. The latter is not suitable for disinfection systems. HOCl and HOI produced during the chlorination process are also converted to I3 - , thus interfering with the determination. This is especially true when the water contains ammonia nitrogen, because chlorine and ammonia nitrogen will produce more oxidation intermediates (NH2Cl, NHCl2, NCl3, etc.), which will greatly affect the determination results.

[0004] Therefore, although the current test method has a certain degree of accuracy and sensitivity, it still has some defects. It is urgent to invent a new method for determining iodate in ammonia nitrogen-containing water during chlorine disinfection. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing method for determining iodate in ammonia nitrogen-containing water, and to provide a simple, effective and more sensitive method for determining iodate in ammonia nitrogen-containing water during chlorine disinfection.

[0006] The technical solution proposed by the present invention to solve the technical problems in the prior art mainly includes the following steps:

[0007] 1) In the presence of IO3 -Add 0.5 mM H2O2 to a 5 ml water sample centrifuge tube, shake evenly, and react for 3 minutes to obtain solution A;

[0008] 2) Add 0.1 mg / L H2O2 enzyme to solution A, shake evenly, and react for 10 minutes to obtain solution B;

[0009] 3) Add 0.6 mM FeSO4 to solution B, shake evenly, and react for 10 minutes to obtain solution C;

[0010] 4) 0.08 M H3PO4 and 0.02 M KI were added to solution C in sequence and reacted for 1 minute to obtain solution D;

[0011] 5) Using an ultraviolet spectrophotometer to measure the absorbance value A of solution D at 351 nm;

[0012] 6) Calculate IO3 - Concentration: c = A / 25700 / (3*1000000) Unit: μM

[0013] The concentrations of the reagent stock solutions used in the above steps are as follows: H2O2 stock solution concentration [H2O2] = 0.1M, H2O2 enzyme stock solution concentration [H2O2 enzyme] = 10mg / L, FeSO4 stock solution [FeSO4] = 0.1M, KI stock solution concentration [KI] = 1M, H3PO4 stock solution concentration [H3PO4] = 4M.

[0014] Beneficial effects:

[0015] The beneficial effects of the present invention are:

[0016] 1) It effectively quenches other substances that interfere with the determination of iodate in ammonia-nitrogen-containing water during chlorine disinfection. This method can determine the iodate concentration more accurately.

[0017] 2) Because this method mainly relies on ultraviolet spectrophotometer to determine iodate concentration, it has a low detection limit and can be used to determine water samples with low iodate content;

[0018] 3) High sensitivity, not affected by other impurities in the water sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Iodate determination curve of ammonia nitrogen-containing water during chlorine disinfection. DETAILED DESCRIPTION

[0020] The present invention is further described below by specific examples and drawings. The examples of the present invention are intended to enable those skilled in the art to better understand the present invention, and do not limit the present invention in any way.

[0021] Example 1

[0022] Dynamic determination of IO3 during disinfection with 0.12 mM chlorine for water samples containing 0.6 mM ammonia nitrogen and 10 μM iodide ions - The specific implementation of the concentration is as follows:

[0023] 1) Take 5 ml of water sample into centrifuge tubes at 0 min, 1 min, 3 min, 5 min, 8 min, 10 min, 20 min, 30 min, 45 min and 60 min after adding chlorine for disinfection reaction;

[0024] 2) Immediately after sampling, add 0.5 mM H2O2 to the centrifuge tube, shake evenly, and react for 3 minutes to obtain solution A;

[0025] 2) Add 0.1 mg / L H2O2 enzyme to solution A, shake evenly, and react for 10 minutes to obtain solution B;

[0026] 3) Add 0.6 mM FeSO4 to solution B, shake evenly, and react for 10 minutes to obtain solution C;

[0027] 4) 0.08 M H3PO4 and 0.02 M KI were added to solution C in sequence and reacted for 1 minute to obtain solution D;

[0028] 5) Using an ultraviolet spectrophotometer to measure the absorbance value A of solution D at 351 nm;

[0029] 6) Calculate IO3 - Concentration: c = A / 25700 / (3*1000000) Unit: μM

[0030] 7) Determination results Figure 1 .

Claims

1. A method for determining the concentration of iodate in ammonia nitrogen-containing water during chlorine disinfection, mainly comprising the following steps: 1) In the presence of IO3 - Add 0.5 mM H2O2 to a 5 ml water sample centrifuge tube, shake evenly, and react for 3 minutes to obtain solution A; 2) Add 0.1 mg / L H2O2 enzyme to solution A, shake evenly, and react for 10 minutes to obtain solution B; 3) Add 0.6 mM FeSO4 to solution B, shake evenly, and react for 10 minutes to obtain solution C; 4) 0.08 M H3PO4 and 0.02 M KI were added to solution C in sequence and reacted for 1 minute to obtain solution D; 5) Using an ultraviolet spectrophotometer to measure the absorbance value A of solution D at 351 nm; 6) Calculate IO3 - Concentration: c = A / 25700 / (3*1000000) Unit: μM The concentrations of the reagent stock solutions used in the above steps are as follows: H2O2 stock solution concentration [H2O2] = 0.1M, H2O2 enzyme stock solution concentration [H2O2 enzyme] = 10mg / L, FeSO4 stock solution [FeSO4] = 0.1M, KI stock solution concentration [KI] = 1M, H3PO4 stock solution concentration [H3PO4] = 4M.

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