CN113884452A - Method for detecting total phosphorus content in scale and corrosion inhibitor for industrial circulating cooling water - Google Patents
Method for detecting total phosphorus content in scale and corrosion inhibitor for industrial circulating cooling water Download PDFInfo
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- 239000011574 phosphorus Substances 0.000 title claims abstract description 126
- 229910052698 phosphorus Inorganic materials 0.000 title claims abstract description 126
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims abstract description 117
- 238000000034 method Methods 0.000 title claims abstract description 76
- 230000007797 corrosion Effects 0.000 title claims abstract description 66
- 238000005260 corrosion Methods 0.000 title claims abstract description 66
- 239000003112 inhibitor Substances 0.000 title claims abstract description 65
- 239000000498 cooling water Substances 0.000 title claims abstract description 24
- 239000000243 solution Substances 0.000 claims abstract description 162
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 78
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims abstract description 62
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims abstract description 44
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims abstract description 38
- 238000011161 development Methods 0.000 claims abstract description 34
- 229960005070 ascorbic acid Drugs 0.000 claims abstract description 31
- 230000029087 digestion Effects 0.000 claims abstract description 31
- 238000002835 absorbance Methods 0.000 claims abstract description 30
- 239000012085 test solution Substances 0.000 claims abstract description 24
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims abstract description 22
- 238000002360 preparation method Methods 0.000 claims abstract description 18
- 239000012086 standard solution Substances 0.000 claims abstract description 18
- 238000010790 dilution Methods 0.000 claims abstract description 15
- 239000012895 dilution Substances 0.000 claims abstract description 15
- 238000012417 linear regression Methods 0.000 claims abstract description 10
- 239000002211 L-ascorbic acid Substances 0.000 claims abstract description 7
- 235000000069 L-ascorbic acid Nutrition 0.000 claims abstract description 7
- 150000003017 phosphorus Chemical class 0.000 claims abstract description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 36
- 238000007865 diluting Methods 0.000 claims description 33
- 235000010323 ascorbic acid Nutrition 0.000 claims description 24
- 239000011668 ascorbic acid Substances 0.000 claims description 24
- 235000018660 ammonium molybdate Nutrition 0.000 claims description 20
- 239000011609 ammonium molybdate Substances 0.000 claims description 20
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 claims description 20
- 229940010552 ammonium molybdate Drugs 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 19
- 239000007787 solid Substances 0.000 claims description 18
- 238000005259 measurement Methods 0.000 claims description 15
- 229910019142 PO4 Inorganic materials 0.000 claims description 14
- 229940026189 antimony potassium tartrate Drugs 0.000 claims description 14
- WBTCZEPSIIFINA-MSFWTACDSA-J dipotassium;antimony(3+);(2r,3r)-2,3-dioxidobutanedioate;trihydrate Chemical compound O.O.O.[K+].[K+].[Sb+3].[Sb+3].[O-]C(=O)[C@H]([O-])[C@@H]([O-])C([O-])=O.[O-]C(=O)[C@H]([O-])[C@@H]([O-])C([O-])=O WBTCZEPSIIFINA-MSFWTACDSA-J 0.000 claims description 14
- 239000010452 phosphate Substances 0.000 claims description 14
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- 230000002829 reductive effect Effects 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 11
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- 239000002253 acid Substances 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 4
- 239000011550 stock solution Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 3
- 235000019796 monopotassium phosphate Nutrition 0.000 description 3
- 238000002798 spectrophotometry method Methods 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 description 2
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 2
- 238000003556 assay Methods 0.000 description 2
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- 235000019253 formic acid Nutrition 0.000 description 2
- 239000011964 heteropoly acid Substances 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 2
- 230000004660 morphological change Effects 0.000 description 2
- TVBSSDNEJWXWFP-UHFFFAOYSA-N nitric acid perchloric acid Chemical compound O[N+]([O-])=O.OCl(=O)(=O)=O TVBSSDNEJWXWFP-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012490 blank solution Substances 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 1
- LWIHDJKSTIGBAC-UHFFFAOYSA-K potassium phosphate Substances [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
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- 238000005070 sampling Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000012421 spiking Methods 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/38—Diluting, dispersing or mixing samples
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/44—Sample treatment involving radiation, e.g. heat
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N21/78—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator producing a change of colour
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Abstract
The invention discloses a method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water, which comprises the steps of adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for developing, measuring the absorbance, drawing a phosphorus standard curve, and obtaining a linear regression equation; adding a sulfuric acid solution and an ammonium persulfate solution with the volume ratio of 1: 30-1: 50 and 40.0-42.0 g/L into the scale and corrosion inhibitor test solution to be measured after twice dilution for digestion; adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into the digested scale and corrosion inhibitor test solution to be detected for color development, measuring absorbance, and obtaining the total phosphorus content in the scale and corrosion inhibitor to be detected according to a linear regression equation; the invention makes clear explanations on the preparation process, the digestion process, the dilution process and the color development process of the reagent solution as well as the addition amount and the addition sequence of various reagents, and can flexibly, simply, accurately and efficiently detect the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water.
Description
Technical Field
The invention belongs to the technical field of chemical element detection, and particularly belongs to a method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water.
Background
In recent years, industrial circulating cooling water is often adopted in the fields of petrochemical industry, electric power, steel and the like to meet the heat exchange requirement in production so as to achieve the aim of saving water resources. However, when the water is recycled, salt substances are continuously separated out from the cooling water, microorganisms are bred, and the equipment is scaled and corroded, so that the service life of the equipment is greatly shortened, and the economic burden of enterprises is increased. In order to solve the problem, scale and corrosion inhibitors with different characteristics are developed in sequence, and the corrosion and scaling conditions of equipment pipelines can be obviously improved only by adding a small amount of the agent in production, so that the utilization rate of circulating cooling water is effectively improved.
In order to meet certain technical and economic indexes, some phosphorus-containing monomer substances are often added into the scale and corrosion inhibitor, and the excessive phosphorus content can cause nutrient-rich oxidation of water, so that the accurate determination and strict control of the phosphorus content in the water treatment agent which is put into production and used on a large scale are very important. At present, most of researches surround the detection of the content of phosphorus in water, and an ICP method, a fluorescence method, an ion chromatography method, a spectrophotometry method and the like are mainly used. The first three methods all adopt high-precision instruments and equipment, are expensive and have higher requirements on the operation process. In contrast, the spectrophotometry method adopts a spectrophotometer with higher cost performance, the operation is simple and easy to implement, and the method is more generally suitable for detecting the phosphorus content.
The detection of the phosphorus content in the complex mixture of the scale and corrosion inhibitor is only clearly explained in HG/T2430-2431-2018 at present. However, according to this method, it is difficult to prepare a satisfactory ammonium molybdate-sulfuric acid solution because the addition amounts, the addition concentrations, and the addition order of various reagents in the preparation of the ammonium molybdate-sulfuric acid solution affect the solution preparation results. In addition, when the absorbance of the scale and corrosion inhibitor solution after color development is measured, if sampling and solution preparation are carried out according to the amount specified in the standard practice method, it is difficult to ensure that the total phosphorus in the solution is sufficiently digested and subjected to color development reaction. In addition, when the absorbance of the developed solution is directly measured, the phosphorus content far exceeds the measurement upper limit of the stable absorbance reading, so that a measurement result has large errors and poor reproducibility, and accurate and reliable experimental data cannot be obtained.
GB/T11893-1989 is mainly aimed at the determination of total phosphorus in water, and is the primary basis of a plurality of phosphorus content determination methods, and the method has the advantages of high risk coefficient of part of required reagents, high requirements on instruments and equipment, and extremely harsh experimental conditions. When potassium persulfate is adopted for high-temperature high-pressure digestion, the whole experimental process is required to be heated for 30min in a high-pressure steam sterilizer at 120 ℃; when nitric acid-perchloric acid are adopted for heating and digestion, perchloric acid and nitric acid are both strong oxidants, the mixture of perchloric acid and organic matters is very easy to explode when heated, the digestion process needs to be carried out in three times, an indicator needs to be added manually after digestion is finished, and color development is carried out after pH is adjusted, so that the steps are complex, the requirement on operators is high, and time and labor are wasted.
In view of the technical defects of the HG/T2430-2431-2018 and GB/T11893-1989 methods, the development of a total phosphorus content detection method which is safe in operation, simple in steps, low in cost, accurate in result and wide in content application range in the direction of the scale and corrosion inhibitor is an urgent problem to be solved by technical personnel in the field.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water, which can flexibly, simply, accurately and efficiently detect the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water by making clear explanations on the preparation process, the digestion process, the dilution process, the color development process of a reagent solution, the addition amount and the addition sequence of various reagents.
In order to achieve the purpose, the invention provides the following technical scheme: a method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water comprises the following steps:
s1, adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for developing, measuring the absorbance, drawing a phosphorus standard curve, and obtaining a linear regression equation;
s2, adding a sulfuric acid solution and an ammonium persulfate solution in a volume ratio of 1: 30-1: 50 and 40.0-42.0 g/L into the test solution of the scale and corrosion inhibitor to be measured after twice dilution, and digesting;
s3, adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into the digested scale and corrosion inhibitor test solution to be detected for color development, measuring absorbance, and obtaining the total phosphorus content in the scale and corrosion inhibitor test solution to be detected according to the linear regression equation obtained in the step S1.
Furthermore, in the steps S1 and S3, the preparation method of the ammonium molybdate-sulfuric acid solution with the concentration of 25.0g/L to 30.0g/L is as follows: respectively dissolving 12.5-15.0 g of ammonium molybdate solid and 0.30-0.40 g of antimony potassium tartrate solid in 80mL of water to obtain an ammonium molybdate aqueous solution and an antimony potassium tartrate solution, adding the ammonium molybdate aqueous solution into 300mL of sulfuric acid solution with the volume ratio of 1: 1-1: 3 to obtain a mixed solution, adding the antimony potassium tartrate solution into the mixed solution, cooling, transferring the mixed solution into a 500mL brown volumetric flask, fixing the volume, and sealing and storing the mixed solution in the brown flask at low temperature.
Further, in steps S1 and S3, 2mL to 4mL of an ammonium molybdate-sulfuric acid solution and 2mL to 4mL of an ascorbic acid solution were added to develop color.
Further, in step S1, the mass range of phosphate in the phosphorus standard solution is 0mg to 0.08 mg.
Further, in step S2, performing first dilution and volume fixing on 0.5000g to 1.0000g of the scale and corrosion inhibitor to be measured, and performing volume fixing to 250mL or 500mL to obtain a mother solution a to be measured; and then carrying out secondary dilution and volume fixing on the mother solution A to be tested to obtain a solution B to be tested.
Further, when the scale and corrosion inhibitor to be measured is a high-phosphorus-containing sample: measuring 1-5 mL of mother solution A to be tested to be diluted to 500mL to obtain a solution B to be tested; when the scale and corrosion inhibitor to be detected is a low-phosphorus-containing sample: measuring 1 mL-5 mL of mother solution A to be tested, and diluting to 250mL to obtain a liquid B to be tested.
Further, in step S2, 1mL to 3mL of sulfuric acid solution and 3mL to 5mL of ammonium persulfate solution are added to 10.0mL to 20.0mL of test solution B, and heated to boiling for digestion reaction, and when the volume of the solution is reduced to half of the original volume, the reaction is ended.
Further, in the steps S1 and S3, the color development is carried out for 15min to 20min under the condition of water bath at the temperature of 25 ℃ to 30 ℃; the absorbance was measured at 710nm using a spectrophotometer.
Further, in steps S1 and S3, the time from the development to the measurement of absorbance does not exceed 30 min.
Further, in steps S1 and S3, the absorbance measurements are performed in the order of decreasing phosphorus content to increasing phosphorus content, and the cuvette is rinsed with clean water or alkaline washing solution after each measurement.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention provides a method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water, which adopts the preparation concentration of a reagent solution and the effective range of the addition amount in the subsequent digestion and color reaction, and is beneficial to experimenters to flexibly and accurately determine the phosphorus content: firstly, ensuring that the amount of the added reagent can meet the requirements of full color development and digestion of a sample when an experimental reagent is prepared (comparing the maximum treatment amount of phosphorus in a national standard method and a standard method with the molar ratio of ammonium molybdate and ascorbic acid added, and screening out the range of proper preparation concentration and addition volume); secondly, the usage amount of the reagent in the experiment is reduced as much as possible, and the reagent consumption cost is reduced; considering the operation flexibility again, the amount or concentration of the added reagent is not limited to a certain value, the requirement can be met only within a reasonable range, the experimental reagent is convenient and easy to obtain, economic and safe, the preparation method is simple, convenient and feasible, the requirement on operators is not high, and the method is easy to repeat.
The invention deeply and finely expounds the experimental operation details, indicates the upper limit of stable reading and total phosphorus content determination by determining the phosphorus standard curve, provides a certain data support for selecting a proper dilution factor when a sample is determined, helps experimenters avoid adverse factors possibly causing experimental failure to the maximum extent, and ensures the smooth operation of the total phosphorus content determination process.
Further, the national standard method and the standard practice method do not explicitly indicate different dilution treatment methods for high and low phosphorus-containing samples, and if all samples are tested strictly according to the methods in the national standard method and the standard practice method, reaction insufficiency or unstable reading may be caused, so that an accurate test result cannot be obtained. The invention provides the idea that the total phosphorus in the sample can be diluted before digestion and can be directly measured after color development, and a flexible sample treatment method to be measured is listed, so that the total phosphorus in the sample can be fully subjected to digestion and color development reaction, and stable, reliable and accurate experimental data can be obtained.
Furthermore, the ammonium persulfate with better water solubility and lower cost is used for digesting the phosphorus-containing sample, but the potassium persulfate with poorer water solubility and higher cost or the nitric acid-perchloric acid (national standard method) with stronger oxidizability is not used, so that the experimental cost is reduced, and the simplicity and the safety of the operation are ensured; the digestion reaction of the invention can reach the experimental requirement only by using the electric heating sleeve, and the full digestion reaction of the sample is ensured.
Further, the invention details the operation steps of preparing the ammonium molybdate-sulfuric acid solution, when preparing the ammonium molybdate-sulfuric acid solution, sulfuric acid with the volume ratio of 1: 1-1: 3 is adopted, the given acidity range not only ensures sufficient acidic environment, eliminates the interference of impurities, is beneficial to preparing qualified solution, but also reduces the use amount of concentrated sulfuric acid, reduces the experiment cost and ensures the safety of experiment operation.
Furthermore, the experimental equipment needed by the invention is simple and cheap, the operation process is rapid and simple, and the investment cost of the experimental equipment is low: the method adopts a phosphomolybdic blue spectrophotometry to measure the phosphorus content, uses an ultraviolet-visible spectrophotometer which has higher cost performance and is easy to operate, and is more economic and efficient compared with an ICP method, a fluorescence method and an ion chromatography method which need expensive instruments to measure the phosphorus content.
Drawings
FIG. 1 is a phosphorus standard curve for example 1;
FIG. 2 is a phosphorus standard curve for example 2;
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific embodiments, but it should be noted that these examples are only for illustrating the present invention, and are not intended to limit the scope of the present invention. Other embodiments, which can be made by one of ordinary skill in the art without inventive faculty, are within the scope of the invention.
A method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water comprises the following steps:
s1, preparing reagents required by the experiment: 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution, 30.0-35.0 g/L ascorbic acid solution, 40.0-42.0 g/L ammonium persulfate solution and phosphorus standard solution.
S2, phosphorus standard curve determination: preparing potassium dihydrogen phosphate solutions with different concentrations, adding 2-4 mL of ammonium molybdate-sulfuric acid solution and 2-4 mL of ascorbic acid solution, fully developing, measuring the absorbance, drawing a standard curve by taking the mass of phosphate radical as a horizontal coordinate and the absorbance as a vertical coordinate, and obtaining a linear regression equation.
S3, digestion of the sample: placing a certain amount of scale and corrosion inhibitor to be measured in a volumetric flask, diluting to a constant volume to a scale, and taking the scale and corrosion inhibitor as mother liquor A to be measured; diluting the mother solution A to be tested by a certain multiple to obtain a mother solution B to be tested;
taking 10.0-20.0 mL of the solution B to be tested, adding 1-3 mL of sulfuric acid solution and 3-5 mL of ammonium persulfate solution in the volume ratio of 1: 30-1: 50, placing on an electric heating sleeve, heating and digesting, and steaming to half of the original volume.
S4, color development and measurement of the sample: and (4) transferring the solution cooled to room temperature after the digestion in the step S3 into a volumetric flask, adding 2-4 mL of ammonium molybdate-sulfuric acid solution and 2-4 mL of ascorbic acid solution, diluting to a constant volume to scale, placing the solution in a water bath condition at 25-30 ℃ for 15-20 min, and carrying out a color reaction. The absorbance was measured at 710nm using a spectrophotometer with a 1cm optical path cuvette and reagent blank as a reference.
S5, calculation of total phosphorus content: by substituting the measurement result of step S4 into the linear regression equation of step S2, the corresponding phosphate radical mass can be obtained, and the total Phosphorus (PO) in the sample can be calculated according to the following formula4 3-) The content is as follows:
in the formula:
m0calculating from the standard curve the total Phosphorus (PO) in the test liquid4 3-) Mass in mg;
m is the actual mass of the weighed sample, and the unit is g;
VAmeasuring the volume of the mother liquor A to be measured, wherein the unit is mL (V)A)；
VBMeasuring the volume of the fluid B to be tested in mL (V)B)；
V1The total volume of the mother liquor A to be tested is mL (V)1)；
V2Total volume of fluid B to be tested in mL (V)2)。
1. As a modification of the present invention, the step S1 of preparing the solution includes the steps of:
s1.1, ammonium molybdate-sulfuric acid solution (25.0 g/L-30.0 g/L): weighing 12.5-15.0 g of ammonium molybdate solid, dissolving the ammonium molybdate solid in about 80mL of water to obtain an ammonium molybdate aqueous solution, weighing 0.30-0.40 g of antimony potassium tartrate solid, dissolving the antimony potassium tartrate solid in about 80mL of water to obtain an antimony potassium tartrate solution, firstly adding the ammonium molybdate aqueous solution into 300mL of sulfuric acid solution with the volume ratio of 1: 1-1: 3, then adding the antimony potassium tartrate solution into the sulfuric acid solution, cooling, transferring the antimony potassium tartrate solution into a 500mL brown volumetric flask, carefully diluting to a scale, uniformly mixing, cooling, placing the mixture into the brown flask, sealing and storing at a low temperature, wherein the storage period is not more than two months.
S1.2, ascorbic acid solution (30.0 g/L-35.0 g/L): weighing 30.0g to 35.0g of ascorbic acid solid, dissolving the ascorbic acid solid in about 500mL of water, adding 0.20g to 0.25g of disodium ethylene diamine tetraacetate and 8mL to 10mL of formic acid, diluting to a constant volume of 1L, uniformly mixing, sealing in a brown bottle, and storing at a low temperature, wherein the storage period is not longer than one month.
S1.3, ammonium persulfate solution (40.0 g/L-42.0 g/L): weighing 2.0 g-2.1 g of ammonium persulfate, diluting to a constant volume of 50mL, and storing in a dark and cool place in a sealed manner to prevent the ammonium persulfate from being hydrolyzed and deteriorated.
S1.4, phosphorus standard solution (0.01mg/mL or 0.02 mg/mL): firstly, a certain amount of potassium dihydrogen phosphate is placed at the temperature of 110 +/-5 ℃ and dried for 2-4 h, 0.1430g (accurate to +/-0.2 mg) of solid is weighed after cooling, and the solid is diluted to a constant volume of 1L to obtain stock solution (0.1 mg/mL); and then taking 50.0mL of stock solution, diluting to a constant volume of 500mL or 250mL to obtain the phosphorus standard solution.
As an improvement of the present invention, the method for preparing the ammonium molybdate-sulfuric acid solution in step S1.1 has significant advantages compared with the national standard method and the standard practice method, and the experimental results of the three preparation methods are shown in table 1.
TABLE 1 Experimental results for preparing ammonium molybdate-sulfuric acid solutions according to different methods
From the above table, it can be seen that:
a. according to the method, the ammonium molybdate-sulfuric acid solution meeting the requirements can be prepared smoothly, and the method has good feasibility and repeatability;
b. compared with the national standard method, the method uses H with the volume ratio of 1:1, 1:1.5, 1:2 and 1:32SO4The solution can meet the preparation requirement, the high acidity environment not only ensures the stable existence of ammonium molybdate in the solution, but also greatly reduces the consumption of concentrated sulfuric acid reagent, saves the experiment cost, and simultaneously improves the practicabilityAnd (6) testing safety and controllability.
c. By comparing the experimental phenomena of the three methods, the preparation process of the ammonium molybdate-sulfuric acid solution is easily interfered by various factors. As the pH of the solution gradually decreased, the heptamolybdate ion ((M)O7O24)6-) Undergoes a series of morphological changes and finally turns into white precipitated MoO3·H2O; when the solution is weak in acidity, the ammonium molybdate is poor in stability, and when trace reducing impurities and phosphate interference exist in the solution at the same time, the ammonium molybdate can be reduced to low-valence phosphomolybdic heteropoly acid, even phosphomolybdic blue. While ammonium molybdate is directly put in an acid environment with lower pH value, and a large amount of H+The existence of the compound can effectively inhibit the morphological change of the molybdate radical, ensure the maximum stability of the molybdate radical, ensure that the molybdate radical is not easy to react with trace reductive impurities and phosphate radicals in the solution, and avoid the generation of white precipitates or phosphomolybdic heteropoly acid and phosphomolybdic blue, thereby obtaining the qualified colorless, clear and transparent ammonium molybdate-sulfuric acid solution.
As a modification of the invention, the concentrations of the ammonium molybdate-sulfuric acid solution and the ascorbic acid solution as set forth in steps S1.1 and S1.2, and the amounts of the two reagents added during color development, are sufficiently reasonable and flexible.
As shown in table 2, the molar ratio of the ammonium molybdate concentration, the addition amount, the ascorbic acid concentration, the addition amount and the maximum value of the content of the treated phosphate radical in the national standard method and the standard method is calculated, and the following conclusions are made:
a. the ratio of the upper limit of phosphorus quality detection to the molar weight of the prepared reagent is partially contained in a feasible interval between a standard method and a national standard method and partially exceeds the national standard method, so that the concentration and volume parameter ranges of the selected reagent can certainly ensure that phosphate radicals in a sample to be treated can fully generate a color reaction;
b. compared with the national standard method and the standard method, the method reduces the reagent dosage during the measurement of a single sample, reduces the reagent consumption cost, and reduces the workload of repeated configuration of the experimental reagent by experimenters;
c. in view of the operational flexibility, the amount or concentration of the added reagent is not limited to a certain value, and the experimental requirements can be satisfied within this range.
TABLE 2 comparison of solution concentrations, addition and treatment amounts prepared by different methods
2. As a modification of the present invention, the step S2 of drawing a phosphorus standard curve includes the following steps:
s2.1, measuring at least 6 phosphorus standard solutions with different volumes within a certain range, respectively placing the phosphorus standard solutions into 50mL volumetric flasks, and then adding a small amount of water;
s2.2, respectively adding 2-4 mL of ammonium molybdate-sulfuric acid solution and 2-4 mL of ascorbic acid solution into the solution and the reagent blank solution, diluting with water to a constant volume, and standing for 15-20 min under the condition of water bath at 25-30 ℃ to generate a color reaction;
and S2.3, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path and taking a reagent blank as a reference.
As an improvement of the invention, the volume range of the phosphorus standard solution measured in the step S2.1 needs to ensure that the mass of the phosphate radical is within 0 mg-0.08 mg, and the reason is that when the mass of the phosphate radical is more than 0.08mg, the absorbance reading difference between parallel samples is large, and an accurate phosphorus standard curve cannot be obtained.
3. As a modification of the present invention, the digestion process of the sample solution of step S3 includes the following steps:
s3.1, accurately weighing 0.5000-1.0000 g of scale and corrosion inhibitor to be measured (accurate to +/-0.2 mg) (phosphorus-containing samples with different concentrations can be properly adjusted), adding water to dissolve the scale and transferring the scale and corrosion inhibitor to a volumetric flask of 250mL or 500mL, diluting and fixing the volume to scale to obtain mother liquor A to be measured; and taking a certain amount of mother liquor A to be tested, diluting the mother liquor A to a certain volume, and obtaining a test liquor B to be tested.
Preferably, the preparation process of the test solution B needs to follow the principle that the test solution B is diluted before digestion and can be directly measured after color development. Wherein, when the scale and corrosion inhibitor to be measured is a high-phosphorus-containing sample: measuring 1-5 mL of mother solution A to be tested to be diluted to 500mL to obtain a solution B to be tested; when the scale and corrosion inhibitor to be detected is a low-phosphorus-containing sample: measuring 1 mL-5 mL of mother solution A to be tested, and diluting to 250mL to obtain a liquid B to be tested.
The dilution multiple of the scale and corrosion inhibitor to be measured can be flexibly adjusted according to the preliminary experiment result, the weighing amount of the scale and corrosion inhibitor to be measured can be adjusted if necessary, the experiment is repeated for many times, and the back calculation error can be reduced to the greatest extent under the optimum dilution multiple, so that a more accurate experiment result is obtained.
S3.2, measuring 10.0-20.0 mL of to-be-tested solution B, adding into a 100mL conical flask, adding 1-3 mL of sulfuric acid solution and 3-5 mL of ammonium persulfate solution in a volume ratio of 1: 30-1: 50, and heating on an electric heating sleeve to perform digestion reaction. When the volume of the solution in the flask was reduced to half, it was removed and cooled to room temperature.
Ammonium persulfate is used as a strong oxidizing medium, sulfuric acid with the volume ratio of 1: 30-1: 50 is added in the digestion process, so that a certain acidic environment is provided for digestion, and the ammonium persulfate can be decomposed under an acidic heating condition, so that organic phosphine is converted into phosphate radicals. However, if too concentrated acid is added during digestion, the subsequent color development process of the phosphate radical can be seriously influenced, and the main reasons for this are that the stability of phosphomolybdic blue is reduced due to too high acidity of the solution, so that the color development capability of the phosphomolybdic blue is weakened, the ammonium molybdate-sulfuric acid solution in the color development agent has certain acidity, and the color development effect is deteriorated due to the superimposed acidity effect generated by the acid remaining in the residual liquid after digestion and the acid remaining in the residual liquid, so that the actual color development result cannot be obtained.
As an improvement of the invention, the total time from color development to measurement of the phosphorus standard solution and the scale and corrosion inhibitor test solution to be measured in the steps S2 and S4 is not longer than 30min, because the absorbance shows a descending trend in different degrees after the measurement time is longer than 30min, and the accuracy of the phosphorus content measurement cannot be ensured.
Example 1
A method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water comprises the following steps:
1. preparation of reagent solution required by experiment:
(1) ammonium molybdate-sulfuric acid solution (30.0 g/L): weighing 15.0g of ammonium molybdate solid, dissolving the ammonium molybdate solid in about 80mL of water, weighing 0.36g of antimony potassium tartrate solid, dissolving the antimony potassium tartrate solid in about 80mL of water, adding an ammonium molybdate aqueous solution into 300mL of sulfuric acid solution with a volume ratio of 1:1, adding an antimony potassium tartrate solution, transferring the ammonium molybdate aqueous solution into a 500mL brown volumetric flask after cooling, carefully diluting to a scale, uniformly mixing, cooling, placing the mixture into the brown flask, sealing and storing at a low temperature, wherein the storage period is not longer than two months.
(2) Ascorbic acid solution (35.0 g/L): weighing 35.0g of ascorbic acid solid, dissolving in about 500mL of water, adding 0.23g of disodium ethylenediamine tetraacetic acid and 9mL of formic acid, diluting to a constant volume of 1L, mixing uniformly, and storing in a brown bottle in a sealed low-temperature manner, wherein the storage period is not longer than one month.
(3) Ammonium persulfate solution (42.0 g/L): weighing 2.1g of ammonium persulfate, diluting to a constant volume of 50mL, storing in a dark and cool place, and preparing immediately before use to prevent the ammonium persulfate from being hydrolyzed and deteriorated.
(4) Phosphorus standard solution (0.02 mg/mL): firstly, a certain amount of monopotassium phosphate is placed at 110 ℃ and dried for 4 hours, 0.1430g of solid is weighed after cooling, and the solution is diluted to a constant volume of 1L to obtain a stock solution; then 50.0mL of stock solution is taken, diluted to a constant volume of 250mL, and standard solution is obtained.
2. Phosphorus standard curve determination:
(1) measuring 0.0mL, 0.5mL, 1.0mL, 1.5mL, 2.0mL, 3.0mL, 4.0mL, 5.0mL and 6.0mL of phosphorus standard solution, respectively placing in a 50mL volumetric flask, adding a small amount of water, and standing;
(2) respectively adding 4mL of ammonium molybdate-sulfuric acid solution and 4mL of ascorbic acid solution into the solution, diluting with water to a constant volume, and standing in a water bath at 30 ℃ for 20min to generate a color reaction;
(3) the absorbance was measured at 710nm using a spectrophotometer using a 1cm optical path cuvette with a reagent blank as a reference, and the results are shown in Table 3.
TABLE 3 determination of phosphorus Standard Curve
From the above table, it can be seen that:
a. when the phosphorus mass is 0-0.08 mg, the standard deviation of the measurement result is less than 0.1%, the relative standard deviation is less than 0.5%, the detection data is more concentrated, the precision is higher, and the repeatability is better;
b. when the phosphorus quality is more than 0.08mg, the standard deviation of the determination result is more than 2 percent, the relative standard deviation is more than 5 percent, the detection data is more dispersed, the precision is lower, and the repeatability is poorer;
c. compared with the upper limit (0.03mg) measured by the national standard method and the upper limit (0.1mg) measured by the standard method, the upper limit (0.08mg) measured by the method can effectively ensure the accuracy and precision of the detection result.
(4) Based on the above experimental findings, the experimental data of adding 0.0mL, 0.5mL, 1.0mL, 1.5mL, 2.0mL, 3.0mL, 4.0mL of phosphorus standard solution respectively is selected as the phosphorus mass (as PO)4 3-Meter) is the abscissa and absorbance is the ordinate, a phosphorus standard curve is plotted, resulting in a linear regression equation, as shown in figure 1. By a linear correlation coefficient R2When the mass of the phosphate radical is in the range of 0mg to 0.08mg, the absorbance and the mass of the phosphate radical show good linear correlation relationship.
3. And (3) determining the total phosphorus content in the high-phosphorus-content scale and corrosion inhibitor:
3.1 preparation of a test solution:
(1) the method comprises the following steps: weighing 0.5000g of scale and corrosion inhibitor to be measured, placing the scale and corrosion inhibitor to be measured in a 250mL volumetric flask, diluting and fixing the volume to obtain mother liquor A to be measured; and measuring 1mL of mother liquor A to be tested, placing the mother liquor A in a 500mL volumetric flask, diluting and fixing the volume to obtain a solution B to be tested.
(2) A line marking method: weighing 1.0001g of scale and corrosion inhibitor to be measured, placing the scale and corrosion inhibitor to be measured in a 250mL volumetric flask, diluting and fixing the volume to obtain mother liquor A to be measured; and measuring 5mL of mother liquor A to be tested, placing the mother liquor A in a 500mL volumetric flask, diluting and fixing the volume to obtain a solution B to be tested.
3.2 digestion of the test solution:
and (3) taking 20.0mL of the solution B to be tested, adding the solution into a 100mL conical flask, adding 3mL of sulfuric acid solution and 5mL of ammonium persulfate solution in a volume ratio of 1:30, and heating the solution on an electric heating jacket to perform digestion reaction. When the volume of the solution in the flask was reduced to half, it was removed and cooled to room temperature.
3.3 color development and determination of the liquid to be tested:
(1) the method comprises the following steps: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 4mL ammonium molybdate-sulfuric acid solution and 4mL ascorbic acid solution, diluting to a constant volume to scale, placing the solution in a water bath condition at 30 ℃ for 20min, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path and taking a reagent blank as a reference, wherein the experimental results are shown in Table 4.
(2) A line marking method:
a. directly measured without dilution: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 4mL ammonium molybdate-sulfuric acid solution and 4mL ascorbic acid solution, diluting to a constant volume to scale, placing the solution in a water bath condition at 30 ℃ for 20min, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path and taking a reagent blank as a reference, wherein the experimental results are shown in Table 4.
b. Dilution 10-fold assay after development: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 4mL ammonium molybdate-sulfuric acid solution and 4mL ascorbic acid solution, diluting to a constant volume to scale, and placing for 20min under the condition of 30 ℃ water bath; taking 5mL of the developed solution, adding the solution into a 50mL volumetric flask, diluting and fixing the volume to a scale, shaking up, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path with a reagent blank as a reference, and ensuring that the measurement is completed within 30min, wherein the experimental results are shown in Table 4.
Calculating the total phosphorus content in the scale and corrosion inhibitor to be measured:
in the formula:
m0calculating from the standard curve the total Phosphorus (PO) in the test liquid4 3-) Mass in mg;
m is the actual mass of the weighed sample, and the unit is g;
VAmeasuring the volume of the mother liquor A to be measured, wherein the unit is mL (V)A)；
VBMeasuring the volume of the fluid B to be tested in mL (V)B)；
V1The total volume of the mother liquor A to be tested is mL (V)1)；
V2Total volume of fluid B to be tested in mL (V)2)。
TABLE 4 Total phosphorus determination of high phosphorus scale and corrosion inhibitors
Example 2
1. Preparation of reagent solution required by experiment:
ammonium molybdate-sulfuric acid solution (25.0g/L) (sulfuric acid solution was used in a volume ratio of 1: 3), ascorbic acid solution (30.0g/L), ammonium persulfate solution (40.0g/L), and phosphorus standard solution (0.02mg/mL), and the procedure was as described in example 1.
2. Phosphorus standard curve determination:
detailed procedure as in example 1, except that 2mL of ammonium molybdate-sulfuric acid solution and 2mL of ascorbic acid solution were added during development, based on phosphorus mass (as PO)4 3-Meter) is the abscissa and absorbance is the ordinate, a phosphorus standard curve is drawn to obtain a linear regression equation, y is 3.2804x +0.0032, R20.9999, as shown in fig. 2.
3. The determination of the total phosphorus content in the low-phosphorus scale and corrosion inhibitor comprises the following steps:
3.1 preparation of a test solution:
(1) the method comprises the following steps: weighing 0.8001g of scale and corrosion inhibitor to be detected, placing the scale and corrosion inhibitor to be detected in a 250mL volumetric flask, diluting and fixing the volume to obtain a mother solution A to be detected; and measuring 2mL of mother liquor A to be tested, placing the mother liquor A in a 250mL volumetric flask, diluting and fixing the volume to obtain a solution B to be tested.
(2) A line marking method: weighing 1.0000g of scale and corrosion inhibitor to be measured, placing the scale and corrosion inhibitor to be measured in a 250mL volumetric flask, diluting and fixing the volume to obtain mother liquor A to be measured; and measuring 5mL of mother liquor A to be tested, placing the mother liquor A in a 250mL volumetric flask, diluting and fixing the volume to obtain a solution B to be tested.
3.2 digestion of the test solution:
and (3) taking 20.0mL of the solution B to be tested, adding the solution into a 100mL conical flask, adding 1mL of sulfuric acid solution and 3mL of ammonium persulfate solution in a volume ratio of 1:50, and heating the solution on an electric heating jacket to perform digestion reaction. When the volume of the solution in the flask was reduced to half, it was removed and cooled to room temperature.
3.3 color development and determination of the liquid to be tested:
(1) the method comprises the following steps: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 2mL ammonium molybdate-sulfuric acid solution and 2mL ascorbic acid solution, diluting to a constant volume to scale, placing the solution in a water bath condition at 25 ℃ for 15min, measuring the absorbance at 710nm by using a spectrophotometer and a 1cm cuvette and taking a reagent blank as a reference, wherein the experimental results are shown in Table 5.
(2) A line marking method:
a. directly measured without dilution: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 2mL ammonium molybdate-sulfuric acid solution and 2mL ascorbic acid solution, diluting to a constant volume to scale, placing the solution in a water bath at 25 ℃ for 15min, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path and taking a reagent blank as a reference, wherein the experimental results are shown in Table 5.
b. Dilution 5-fold assay after development: transferring the test solution which is digested in the previous step and cooled to room temperature into a 50mL volumetric flask, adding 2mL ammonium molybdate-sulfuric acid solution and 2mL ascorbic acid solution, diluting to a constant volume to scale, and placing for 15min under the condition of water bath at 25 ℃; and (3) adding 20.0mL of the developed solution into a 50mL volumetric flask, diluting to a constant volume to scale, shaking uniformly, measuring the absorbance at 710nm by using a spectrophotometer and a cuvette with a 1cm optical path and taking a reagent blank as a reference, and ensuring that the measurement is completed within 30min, wherein the experimental results are shown in Table 5.
Calculating the total phosphorus content in the scale and corrosion inhibitor to be measured:
in the formula:
m0calculating from the standard curve the total Phosphorus (PO) in the test liquid4 3-) Mass in mg;
m is the actual mass of the weighed sample, and the unit is g;
VAmeasuring the volume of the mother liquor A to be measured, wherein the unit is mL (V)A)；
VBMeasuring the volume of the fluid B to be tested in mL (V)B)；
V1The total volume of the mother liquor A to be tested is mL (V)1)；
V2Total volume of fluid B to be tested in mL (V)2)。
TABLE 5 Total phosphorus determination of low phosphorus scale and corrosion inhibitors
Example 3
Taking three samples with known total phosphorus content, adding different amounts of phosphorus standard solutions respectively, and carrying out a standard addition recovery experiment according to the detection method of the invention.
The detailed procedure is the same as in example 1, except that an ammonium molybdate-sulfuric acid solution (28.0g/L) (a sulfuric acid solution in a volume ratio of 1:2 is used), an ascorbic acid solution (32.0g/L), and an ammonium persulfate solution (41.0 g/L); 2mL of sulfuric acid solution with the volume ratio of 1:40 and 4mL of ammonium persulfate solution are added during digestion; when the color was developed, 3mL of an ammonium molybdate-sulfuric acid solution and 3mL of an ascorbic acid solution were added, and the color was developed by a water bath at 28 ℃ for 18min, and the results are shown in Table 6.
TABLE 6 test results of recovery with addition of a label
From the above two specific examples and the spiking recovery experiment, it can be seen that:
(1) compared with the method of the invention, the total phosphorus content detected by the line marking method is lower, and the reasons are that: when the total phosphorus is directly measured after a sample test solution to be measured is not diluted and developed, the content of the total phosphorus in the test solution is high, the addition amount of a color developing agent and a digesting agent or the development time of 15min is not enough to ensure that the digestion reaction and the color development reaction are fully performed, and the phosphorus content is far more than the upper limit of the stable absorbance reading of the phosphorus, so that reliable experimental data cannot be obtained; when the test solution is diluted by a certain multiple after developing color to measure the total phosphorus, although the phosphorus content can be ensured to be in a detection range with stable absorbance, the problems of insufficient digestion and color development of the total phosphorus exist, and the back calculation error exists, so the measurement results are low.
(2) In the standard method, the experimental data is more dispersed when the total phosphorus is directly measured after a sample to be measured is not diluted and developed, the standard deviation is larger, the higher the total phosphorus content is, the larger the standard deviation is, and the maximum value is even more than 2%; the experimental data of the method for detecting the total phosphorus is concentrated, the standard deviation is small, the value is within 0.5%, and the result proves that the method has good repeatability.
(3) In the standard method, the relative standard deviation is large when the total phosphorus is directly measured after a sample to be measured is not diluted and developed, and the maximum value is even more than 5%; the relative standard deviation of the total phosphorus detected by the method is small, the value of the relative standard deviation is not more than 1%, and the result proves that the method has higher precision.
(4) According to the method, after three groups of standard addition recovery tests are tried, the recovery rate is found to be more than 98%, the quality control requirement of an environmental water quality detection laboratory is met, and the result proves that the method has higher accuracy.
In conclusion, the detection method adopted by the embodiment of the invention has the advantages of simple and convenient operation, economy, safety, high efficiency, flexibility, higher accuracy, higher precision and better result reproducibility, and can be widely applied to the detection method of the total phosphorus content in the scale and corrosion inhibitor.
The present embodiments are to be considered as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (10)
1. A method for detecting the total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water is characterized by comprising the following steps:
s1, adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for developing, measuring the absorbance, drawing a phosphorus standard curve, and obtaining a linear regression equation;
s2, adding a sulfuric acid solution and an ammonium persulfate solution in a volume ratio of 1: 30-1: 50 and 40.0-42.0 g/L into the test solution of the scale and corrosion inhibitor to be measured after twice dilution, and digesting;
s3, adding 25.0-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0-35.0 g/L ascorbic acid solution into the digested scale and corrosion inhibitor test solution to be detected for color development, measuring absorbance, and obtaining the total phosphorus content in the scale and corrosion inhibitor to be detected according to the linear regression equation obtained in the step S1.
2. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water as claimed in claim 1, wherein in the steps S1 and S3, the preparation method of the ammonium molybdate-sulfuric acid solution with the concentration of 25.0g/L to 30.0g/L comprises the following steps: respectively dissolving 12.5-15.0 g of ammonium molybdate solid and 0.30-0.40 g of antimony potassium tartrate solid in 80mL of water to obtain an ammonium molybdate aqueous solution and an antimony potassium tartrate solution, adding the ammonium molybdate aqueous solution into 300mL of sulfuric acid solution with the volume ratio of 1: 1-1: 3 to obtain a mixed solution, adding the antimony potassium tartrate solution into the mixed solution, cooling, transferring the mixed solution into a 500mL brown volumetric flask, fixing the volume, and sealing and storing the mixed solution at low temperature in the brown flask.
3. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water as claimed in claim 1, wherein in steps S1 and S3, 2 mL-4 mL ammonium molybdate-sulfuric acid solution and 2 mL-4 mL ascorbic acid solution are added for color development.
4. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in step S1, the mass range of phosphate radical in the phosphorus standard solution is 0 mg-0.08 mg.
5. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in step S2, 0.5000g to 1.0000g of the scale and corrosion inhibitor to be detected is subjected to first dilution to fix the volume to 250mL or 500mL to obtain a mother solution A to be detected; and then carrying out secondary dilution and volume fixing on the mother solution A to be tested to obtain a solution B to be tested.
6. The method for detecting the total phosphorus content in the industrial circulating cooling water scale and corrosion inhibitor according to claim 5, wherein when the scale and corrosion inhibitor to be detected is a high-phosphorus-content sample: measuring 1-5 mL of mother solution A to be tested to be diluted to 500mL to obtain a solution B to be tested; when the scale and corrosion inhibitor to be detected is a low-phosphorus-containing sample: measuring 1 mL-5 mL of mother solution A to be tested, and diluting to 250mL to obtain a liquid B to be tested.
7. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in step S2, 1mL to 3mL of sulfuric acid solution and 3mL to 5mL of ammonium persulfate solution are added to 10.0mL to 20.0mL of liquid B to be tested, the solution is heated to boiling for digestion reaction, and the reaction is ended when the volume of the solution is reduced to half of the original volume.
8. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in the steps S1 and S3, the color development is carried out for 15min to 20min under the condition of water bath at 25 ℃ to 30 ℃; the absorbance was measured at 710nm using a spectrophotometer.
9. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water as claimed in claim 1, wherein the time from the color development to the absorbance measurement in steps S1 and S3 is not more than 30 min.
10. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water as claimed in claim 1, wherein in steps S1 and S3, the absorbance measurements are performed in the order of the phosphorus content from low to high, and the cuvette is rinsed with clear water or alkaline washing solution after each measurement.
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| WO2024066180A1 (en) * | 2022-09-28 | 2024-04-04 | 广东邦普循环科技有限公司 | Method for measuring total phosphorus content of non-ferrous metal extraction waste liquid |
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