Rapid chemical oxygen demand testing method and application

Abstract

The invention discloses a method for quickly testing chemical oxygen demand, which comprises the following steps of: 1, preparing a test solution which comprises the following components: A, a potassium dichromate solution (c is equal to 0.0250 mol / L); b, a mercury sulfate solution (100g / L); c, a silver sulfate-sulfuric acid solution (10g / L); 2, preparing a standard water sample; step 3, preparing a comparison reference sample, sequentially adding the standard water sample, the reagent B and the reagent A into the colorimetric tube, uniformly shaking, adding the reagent C into the colorimetric tube by using a pipette, uniformly shaking, and standing until the reaction is finished; 4, developing the water sample to be detected, sequentially adding the water sample to be detected, the reagent B and the reagent A into the colorimetric tube, uniformly shaking, adding the reagent C into the colorimetric tube by using the pipette, uniformly shaking, and standing until the reaction is finished; and 5, carrying out color comparison on the to-be-detected water sample obtained in the step 4 and a comparison reference sample.

Description

[0001] The present application is a divisional application, the original application is entitled "Method for rapidly testing chemical oxygen demand", the application number is 202211281412.8, and the application date is October 19, 2022. TECHNICAL FIELD

[0002] The present application relates to the technical field of water quality monitoring, in particular to a method for rapidly testing chemical oxygen demand. BACKGROUND

[0003] At present, in the field of water environment monitoring, chemical oxygen demand is one of the most common and most commonly used detection parameters, and almost all environmental monitoring standards related to water bodies have emission regulations on chemical oxygen demand. Chemical oxygen demand is an index for measuring the content of reducing substances in water bodies, and is one of the important parameters for judging the degree of water pollution.

[0004] At present, the commonly used national and local standards and industry standards generally stipulate that the testing method for chemical oxygen demand is HJ / T399-2007 "Determination of Chemical Oxygen Demand in Water by Rapid Digestion Spectrophotometry" and HJ828-2017 "Determination of Chemical Oxygen Demand in Water by Dichromate Method". The principles of these two methods are similar, both of which use silver sulfate as a catalyst and mercury sulfate as a chloride shielding agent to digest the water sample with potassium dichromate solution in a strong acid environment, and then measure the consumption of potassium dichromate by spectrophotometry or titration, thereby calculating the chemical oxygen demand of the water sample.

[0005] Both of the above-mentioned methods require professional instruments for experiments at high temperatures, and the experiments must be long. For small and medium-sized enterprise wastewater treatment systems, neither of these two methods is very suitable. The chemical oxygen demand detection requirements of small and medium-sized enterprise wastewater treatment systems have the following characteristics: 1. Convenient and fast; 2. Low cost; 3. Try not to use special instruments; 4. Analysis accuracy can be appropriately relaxed; 5. Most of the water samples are discharge outlets and biochemical reaction tank samples, and the digestion difficulty is relatively low, and the chemical oxygen demand value is not high; 6. High detection frequency.

[0006] The chemical oxygen demand rapid detection scheme currently sold on the market generally requires the purchase of instruments that can perform high-temperature digestion, while a small number of detection schemes that do not require the purchase of instruments have high single-test costs due to the selling price, which is not an economical choice for small and medium-sized enterprises. SUMMARY

[0007] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a method for rapidly testing chemical oxygen demand, which can shorten the detection time and improve the detection efficiency.

[0008] The method for quickly testing chemical oxygen demand according to the embodiment of the application comprises the following steps:

[0009] Step 1: configuring a test solution, the test solution comprising:

[0010] A, potassium dichromate solution (c=0.0250 mol / L);

[0011] B, mercury sulfate solution (100 g / L);

[0012] C, silver sulfate-sulfuric acid solution (10 g / L);

[0013] Step 2: preparing a standard water sample;

[0014] Step 3: preparing a comparison reference sample, sequentially adding the standard water sample, reagent B and reagent A into a colorimetric tube, shaking, using a pipette to add reagent C into the colorimetric tube, and then shaking and waiting for the reaction to end;

[0015] Step 4: coloring the water sample to be tested, sequentially adding the water sample to be tested, reagent B and reagent A into a colorimetric tube, shaking, using a pipette to add reagent C into the colorimetric tube, and then shaking and waiting for the reaction to end;

[0016] Step 5: comparing the water sample to be tested, which has completed step 4, with the comparison reference sample by colorimetry.

[0017] The method for quickly testing chemical oxygen demand according to the embodiment of the application has at least the following beneficial effects: after reagent C is added into the colorimetric tube and mixed with the solution in the colorimetric tube, the solution in the colorimetric tube can be slightly boiled in a short time, the user does not need to purchase additional special instruments to heat and digest the solution, the result of single detection can be obtained in a short time, at the same time, the analysis accuracy can meet the level requirement, the user detection efficiency is greatly improved, the detection time is shortened, rapid detection is realized, and the detection cost is low.

[0018] The method for quickly testing chemical oxygen demand according to the embodiment of the application further comprises step 4: preparing a reference water sample.

[0019] The method for quickly testing chemical oxygen demand according to the embodiment of the application, step 4 and step 2 can be performed synchronously.

[0020] The method for quickly testing chemical oxygen demand according to the embodiment of the application, in step 3, the water sample to be tested is 10 ml, reagent B is 1 ml, reagent A is 2 ml, and reagent C is 15 ml.

[0021] The method for quickly testing chemical oxygen demand according to the embodiment of the application, in step 3, after reagent C is added into the colorimetric tube, the solution in the colorimetric tube is allowed to stand for 3 to 5 min after the reaction ends.

[0022] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the attendant drawings or can be learned by practice of the application. DETAILED DESCRIPTION

[0023] In the description of the application, the meaning of one or more is one or more, the meaning of multiple is two or more, greater than, less than, more than, etc. is understood as not including the number, above, below, within, etc. is understood as including the number. If the first, second is described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0024] In the description of the application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and those skilled in the art can reasonably determine the specific meaning of the above words in the application in combination with the specific content of the technical scheme.

[0025] The embodiment of the application provides a method for quickly testing chemical oxygen demand, comprising:

[0026] Step 1: configure a test solution, the test solution comprising:

[0027] A, potassium dichromate solution (c=0.0250mol / L);

[0028] B, mercury sulfate solution (100g / L);

[0029] C, silver sulfate-sulfuric acid solution (10g / L);

[0030] Step 2: make a standard water sample;

[0031] Step 3: make a comparison reference sample, sequentially add the standard water sample, reagent B and reagent A into the colorimetric tube, shake well, then use a pipette to add reagent C into the colorimetric tube, shake again, and wait for the reaction to end;

[0032] Step 4: color the water sample to be tested, sequentially add the water sample to be tested, reagent B and reagent A into the colorimetric tube, shake well, then use a pipette to add reagent C into the colorimetric tube, shake again, and wait for the reaction to end;

[0033] Step 5: compare the colorimetry of the water sample to be tested in step 4 with the comparison reference sample.

[0034] Specifically, the application provides an embodiment as a reference:

[0035] Embodiment 1:

[0036] Preparation of reagent A: accurately weigh the reference reagent grade potassium dichromate with constant weight at 105 DEG C. 12.258 g, dissolve with water and dilute to 1000 ml, and then dilute 10 times.

[0037] Preparation of reagent B: weigh 10 g of mercury sulfate and dissolve in 100 ml of sulfuric acid solution (1+9).

[0038] Preparation of reagent C: weigh 10 g of silver sulfate, dissolve in 1 L of concentrated sulfuric acid, stand for 1-2 d, and shake carefully before use.

[0039] The above reagents are all stored in glass bottles.

[0040] Preparation of chemical oxygen demand standard solution (50 mg / L): accurately weigh potassium hydrogen phthalate dried at 105 DEG C for 2 h. 0.4251 g, dissolve with water and dilute to 1000 ml, and then dilute 10 times.

[0041] The water sample to be tested, the chemical oxygen demand (COD) standard solution can be detected by colorimetry at the same time, or by colorimetry before and after, all according to the following method: take 10 ml of the water sample to be tested and the chemical oxygen demand standard solution (50 mg / L) respectively, add 50 ml of colorimetric tube, add reagent B 1 ml, reagent A 2 ml in order, shake, take reagent C 15 ml with a pipette, slowly add it to the colorimetric tube along the wall, after adding it into the tube, the solution boils slightly, heats, and stands for 3 to 5 minutes. According to the color of the solution in the tube, judge whether the chemical oxygen demand of the water sample to be tested exceeds 50 mg / L, the lighter the color of the solution, the higher the value of the chemical oxygen demand. The chemical oxygen demand (COD) standard solution is a standard water sample.

[0042] The water samples discharged after treatment of different types of industrial wastewater are used as the water samples to be tested, and the above water samples are determined for accurate chemical oxygen demand values according to HJ828-2017 "Determination of chemical oxygen demand in water by dichromate method".

[0043]

[0044] According to the conditions of the detection method provided in the application, the lighter the color of the solution in the colorimetric tube, the higher the COD value of the water sample to be tested.

[0045] The user only needs to visually inspect to quickly obtain the detection result, greatly improving the detection efficiency.

[0046] In the description of the specification, reference to "one embodiment", "some embodiments", "an exemplary embodiment", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "in some embodiments", "in an exemplary embodiment", "an example", "a specific example", or "some examples" in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0047] Although embodiments of the application have been shown and described, it will be appreciated that those skilled in the art can make various changes, modifications, substitutions and alterations thereto without departing from the principles and scope of the application, which are defined by the claims and their equivalents.

Claims

1. A rapid method for testing chemical oxygen demand, characterized in that, include: Prepare the test solution; Prepare standard water samples; Create a baseline sample for comparison; To develop color in the water sample to be tested, add the water sample to be tested, reagent B, and reagent A to the colorimetric tube in sequence, shake well, then use a pipette to add reagent C to the colorimetric tube, shake well again, and wait for the reaction to finish. The water sample to be tested, which has completed step 4, is compared with the reference sample by colorimetry. The test solutions include: A) potassium dichromate solution; B) mercuric sulfate solution; and C) silver sulfate-sulfuric acid solution. The specific process for preparing the comparative reference sample is as follows: add standard water sample, reagent B, and reagent A to the colorimetric tube in sequence, shake well, then use a pipette to add reagent C to the colorimetric tube, shake well again, and wait for the reaction to complete.

2. The application of the method as described in claim 1 in water quality monitoring.

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