CN113884452B - 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 120
- 229910052698 phosphorus Inorganic materials 0.000 title claims abstract description 120
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims abstract description 114
- 238000000034 method Methods 0.000 title claims abstract description 63
- 230000007797 corrosion Effects 0.000 title claims abstract description 61
- 238000005260 corrosion Methods 0.000 title claims abstract description 61
- 239000003112 inhibitor Substances 0.000 title claims abstract description 59
- 239000000498 cooling water Substances 0.000 title claims abstract description 19
- 239000000243 solution Substances 0.000 claims abstract description 172
- 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 60
- 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
- 230000029087 digestion Effects 0.000 claims abstract description 41
- 238000011161 development Methods 0.000 claims abstract description 40
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims abstract description 39
- 238000002835 absorbance Methods 0.000 claims abstract description 30
- 229960005070 ascorbic acid Drugs 0.000 claims abstract description 30
- 239000012085 test solution Substances 0.000 claims abstract description 25
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims abstract description 22
- 238000002360 preparation method Methods 0.000 claims abstract description 19
- 239000012086 standard solution Substances 0.000 claims abstract description 19
- 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 35
- 238000005259 measurement Methods 0.000 claims description 26
- 235000010323 ascorbic acid Nutrition 0.000 claims description 23
- 239000011668 ascorbic acid Substances 0.000 claims description 23
- 239000010413 mother solution Substances 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 18
- 235000018660 ammonium molybdate Nutrition 0.000 claims description 16
- 239000011609 ammonium molybdate Substances 0.000 claims description 16
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 claims description 16
- 229940010552 ammonium molybdate Drugs 0.000 claims description 16
- 229940026189 antimony potassium tartrate Drugs 0.000 claims description 16
- 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 16
- 229910019142 PO4 Inorganic materials 0.000 claims description 14
- 239000010452 phosphate Substances 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 14
- 239000012452 mother liquor Substances 0.000 claims description 13
- 238000010790 dilution Methods 0.000 claims description 12
- 239000012895 dilution Substances 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 238000003860 storage Methods 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- 238000011481 absorbance measurement Methods 0.000 claims description 3
- 238000009835 boiling Methods 0.000 claims description 2
- 238000005406 washing Methods 0.000 claims description 2
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 35
- 230000008569 process Effects 0.000 abstract description 12
- 238000003113 dilution method Methods 0.000 abstract description 2
- 238000010561 standard procedure Methods 0.000 description 24
- 239000000523 sample Substances 0.000 description 21
- 238000007865 diluting Methods 0.000 description 20
- 238000001514 detection method Methods 0.000 description 15
- 238000002474 experimental method Methods 0.000 description 14
- 238000005303 weighing Methods 0.000 description 11
- 230000006872 improvement Effects 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 6
- 238000005485 electric heating Methods 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 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
- 239000012488 sample solution Substances 0.000 description 4
- 239000011550 stock solution Substances 0.000 description 4
- 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
- 239000003109 Disodium ethylene diamine tetraacetate Substances 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
- HSNVNALJRSJDHT-UHFFFAOYSA-N P(=O)(=O)[Mo] Chemical compound P(=O)(=O)[Mo] HSNVNALJRSJDHT-UHFFFAOYSA-N 0.000 description 2
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002795 fluorescence method Methods 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 239000011964 heteropoly acid Substances 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- 238000002372 labelling Methods 0.000 description 2
- 238000002156 mixing Methods 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
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- UJQGVDNQDFTTLZ-VNHYZAJKSA-N 2-[(2r,4ar,8as)-4a-methyl-8-methylidene-1,2,3,4,5,6,7,8a-octahydronaphthalen-2-yl]prop-2-enoic acid Chemical compound C1CCC(=C)[C@@H]2C[C@H](C(=C)C(O)=O)CC[C@]21C UJQGVDNQDFTTLZ-VNHYZAJKSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- AUJJPYKPIQVRDH-UHFFFAOYSA-N antimony potassium Chemical compound [K].[Sb] AUJJPYKPIQVRDH-UHFFFAOYSA-N 0.000 description 1
- 239000012490 blank solution Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- MEFBJEMVZONFCJ-UHFFFAOYSA-N molybdate Chemical compound [O-][Mo]([O-])(=O)=O MEFBJEMVZONFCJ-UHFFFAOYSA-N 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 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
- AMWVZPDSWLOFKA-UHFFFAOYSA-N phosphanylidynemolybdenum Chemical compound [Mo]#P AMWVZPDSWLOFKA-UHFFFAOYSA-N 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 229910052700 potassium 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
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 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
- 238000001556 precipitation Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
Classifications
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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
-
- G—PHYSICS
- 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
-
- G—PHYSICS
- 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
- G01N1/44—Sample treatment involving radiation, e.g. heat
-
- 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
Abstract
The invention discloses a method for detecting total phosphorus content in a scale and corrosion inhibitor for industrial circulating cooling water, which comprises the steps of adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for color development, measuring the absorbance of the solution, and drawing a phosphorus standard curve to obtain 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 g/L-42.0 g/L into the twice diluted scale and corrosion inhibitor test solution to be tested for digestion; adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-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 explanation on the preparation process, digestion process, dilution process and color development process of reagent solution, and the addition amount and 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 relates to a method for detecting total phosphorus content in an anti-scale 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 purpose of saving water resources. However, during recycling, salt substances can be continuously separated out from the cooling water, microorganisms are bred, scaling corrosion of equipment is caused, the service life of the equipment is greatly reduced, and the economic burden of enterprises is increased. In order to solve the problem, the scale and corrosion inhibitor with different characteristics is developed successively, and the corrosion and scaling condition of equipment pipelines can be obviously improved by only adding a small amount of the reagent in production, so that the utilization rate of circulating cooling water is effectively improved.
In order to meet certain technical and economic indexes, a certain amount of phosphorus-containing monomer substances are often added into the scale and corrosion inhibitor, and the excessive phosphorus content can lead to rich oxidation of water, so that the accurate determination and strict control of the phosphorus content in the water treatment agent put into production and use on a large scale are particularly important. At present, most researches are carried out around the detection of the phosphorus content in water, mainly including an ICP method, a fluorescence method, an ion chromatography method, a spectrophotometry method and the like. The first three methods all adopt high-precision instruments and equipment, are high in price and have high requirements on the operation process. In comparison, the spectrophotometry adopts a spectrophotometer with higher cost performance, the operation is simple and easy, and the method is more generally applicable to the detection of the phosphorus content.
For the detection of the phosphorus content in the complex mixture of the scale and corrosion inhibitor, only the HG/T2430-2431-2018 is explicitly described at present. However, with reference to this method, it is difficult to prepare a satisfactory ammonium molybdate-sulfuric acid solution because the addition amount, concentration and order of addition of various reagents during the preparation of the ammonium molybdate-sulfuric acid solution affect the solution preparation result. In addition, when the absorbance of the scale and corrosion inhibitor solution after color development is measured, if sampling and solution preparation are performed in an amount specified in a line standard method, it is difficult to ensure that the digestion and color development reaction of the total phosphorus in the solution sufficiently occurs. In addition, when the absorbance of the developed solution is directly measured, the phosphorus content is far more than the upper measurement limit of absorbance stable reading, so that a larger error is generated in the measurement result, the reproducibility is poor, and therefore, accurate and reliable experimental data cannot be obtained.
The GB/T11893-1989 is mainly aimed at the determination of total phosphorus in water quality, and is the primary basis of a plurality of phosphorus content determination methods, and the method has the advantages of higher risk coefficient of partial reagents, higher instrument and equipment requirements and extremely harsh experimental conditions. When adopting potassium persulfate-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 is adopted for heating and digestion, perchloric acid and nitric acid are strong oxidants, the mixture of perchloric acid and organic matters is easy to explode when heated, the digestion process is required to be carried out for three times, an indicator is also required to be manually added after the digestion is completed, color development is carried out after the pH is regulated, the steps are complex, the requirements on operators are high, and time and labor are wasted.
In view of the technical defects of the two methods of HG/T2430-2431-2018 and GB/T11893-1989, the development of a method for detecting the total phosphorus content, which is safe to operate, simple and convenient in steps, low in cost, accurate in results and wide in content application range, in the scale and corrosion inhibitor direction is a problem to be solved by the person skilled in the art.
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 clearly describing the preparation process, digestion process, dilution process and color development process of reagent solution, and the addition quantity and addition sequence of various reagents.
In order to achieve the above purpose, the present invention provides the following technical solutions: the method for detecting the total phosphorus content in the scale and corrosion inhibitor for the industrial circulating cooling water comprises the following steps:
s1, adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for color development, measuring the absorbance of the solution, and drawing a phosphorus standard curve to obtain a linear regression equation;
s2, adding a sulfuric acid solution and an ammonium persulfate solution with the volume ratio of 1:30-1:50 and 40.0 g/L-42.0 g/L into the twice diluted scale and corrosion inhibitor test solution to be tested for digestion;
s3, adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-35.0 g/L ascorbic acid solution into the digested scale and corrosion inhibitor test solution to be tested for color development, measuring absorbance, and obtaining the total phosphorus content in the scale and corrosion inhibitor test solution to be tested according to the linear regression equation obtained in the step S1.
Further, 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 g-15.0 g of ammonium molybdate solid and 0.30 g-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 into a 500mL brown volumetric flask, fixing the volume, and placing into the brown volumetric flask for sealing and preserving at low temperature.
Further, in the steps S1 and S3, 2 mL-4 mL of an ammonium molybdate-sulfuric acid solution and 2 mL-4 mL of an ascorbic acid solution are added to develop color.
In step S1, the mass of the phosphate radical in the phosphorus standard solution is in the range of 0mg to 0.08mg.
In the step S2, 0.5000-1.0000 g of scale and corrosion inhibitor to be tested is diluted for the first time to fix the volume to 250mL or 500mL to obtain mother liquor A to be tested; and then carrying out secondary dilution and volume fixing on the mother solution A to be tested to obtain the liquid B to be tested.
Further, when the scale and corrosion inhibitor to be detected is a high phosphorus sample: 1 mL-5 mL of mother solution A to be tested is measured and diluted to 500mL to obtain solution B to be tested; when the scale and corrosion inhibitor to be detected is a low-phosphorus sample: and 1 mL-5 mL of mother solution A to be tested is measured and diluted to 250mL, so as to obtain solution B to be tested.
In step S2, 1 mL-3 mL of sulfuric acid solution and 3 mL-5 mL of ammonium persulfate solution are added into 10.0 mL-20.0 mL of to-be-tested solution B, the solution is heated to boiling to carry out 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 15 to 20 minutes under the water bath condition 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 is not more than 30min.
Further, in steps S1 and S3, absorbance measurement is performed in order of low phosphorus content from high, and after each measurement is completed, the cuvette is rinsed with clear water or alkaline washing solution.
Compared with the prior art, the invention has at least the following beneficial effects:
the method for detecting the total phosphorus content in the scale and corrosion inhibitor for industrial circulating cooling water provided by the invention adopts the preparation concentration of the reagent solution and the effective range of the addition amount in the subsequent digestion and color development reaction, and is beneficial to the experimenters to flexibly and accurately measure the phosphorus content: firstly, when an experimental reagent is prepared, the amount of the added reagent is ensured to meet the requirements of full color development and digestion of a sample (compared with the maximum treatment amount of phosphorus and the molar ratio of added ammonium molybdate and ascorbic acid in a national standard method and a line standard method, the range of proper preparation concentration and addition volume is screened out); secondly, the use 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 fixed value, and the requirement can be met only in a reasonable range, so that the experimental reagent is convenient and easy to obtain, economical and safe, the preparation method is simple and feasible, the requirement on operators is low, and the method is easy to repeat.
The invention further and carefully clarifies experimental operation details, and indicates the upper limit of stable reading and total phosphorus content measurement through measuring the phosphorus standard curve, so that a certain data support is provided for selecting proper dilution factors during sample measurement, the experimenter is helped to avoid adverse factors which possibly cause experimental failure to the greatest extent, and the smooth proceeding of the total phosphorus content measurement process is ensured.
Furthermore, the national standard method and the line standard method do not clearly indicate different dilution treatment methods for high and low phosphorus-containing samples, and if all samples are subjected to experiments strictly according to the methods in the national standard method and the line standard method, insufficient reaction or unstable reading may be caused, so that accurate experimental results cannot be obtained. The invention provides the point that dilution is carried out before digestion and direct measurement can be carried out after color development, and a flexible sample treatment method to be tested is listed, so that the total phosphorus in the sample can be ensured to fully undergo digestion and color development reaction, and stable, reliable and accurate experimental data can be obtained.
Furthermore, ammonium persulfate which is better in water solubility and lower in cost is used for digestion of the phosphorus-containing sample, instead of potassium persulfate which is poorer in water solubility and higher in cost or nitric acid-perchloric acid which is stronger in oxidability (national standard method), so that the experimental cost is reduced, and the simplicity and safety of operation are ensured; the digestion reaction can meet the experimental requirements only by using the electric heating sleeve, so that the sample is ensured to be fully digested, and compared with a high-pressure steam sterilizer in a national standard method or an electric furnace in a line standard method, the method has the advantages of higher operation safety and reduced equipment investment cost.
Further, the invention details the operation steps for 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 ensures the sufficient acidic environment, eliminates the interference of impurities, is favorable for preparing qualified solution, reduces the consumption of concentrated sulfuric acid, lowers the experiment cost, and ensures the safety of experiment operation.
Furthermore, the experimental instrument and equipment required by the invention are simpler and cheaper, the operation process is quicker and simpler, and the input cost of the experimental equipment is lower: the invention adopts a phosphorus-molybdenum blue spectrophotometry to measure the phosphorus content, and adopts an ultraviolet-visible spectrophotometer with higher cost performance and easy operation, compared with an ICP method, a fluorescence method and an ion chromatography method, which need to adopt expensive instruments to finish the phosphorus content measurement, the method is more economic and efficient.
Drawings
FIG. 1 is a phosphorus standard curve of example 1;
FIG. 2 is a phosphorus standard curve of example 2;
Detailed Description
The invention will be further described with reference to the drawings and detailed description which follow, but it should be understood that these examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention. Other embodiments, which are within the scope of the invention, will be apparent to those of ordinary skill in the art without undue burden.
The method for detecting the total phosphorus content in the scale and corrosion inhibitor for the industrial circulating cooling water comprises the following steps:
s1, preparing reagents required by experiments: 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution, 30.0 g/L-35.0 g/L ascorbic acid solution, 40.0 g/L-42.0 g/L ammonium persulfate solution and phosphorus standard solution.
S2, determination of a phosphorus standard curve: preparing monopotassium 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 of the solution, taking the quality of phosphate as an abscissa and the absorbance as an ordinate, and drawing a standard curve to obtain a linear regression equation.
S3, digestion of a sample: placing a certain amount of scale and corrosion inhibitor to be measured into a volumetric flask, and diluting to a fixed volume to obtain a scale, wherein the scale and corrosion inhibitor to be measured is used as mother liquor A to be measured; diluting the mother solution A to be tested by a certain multiple to obtain a solution B to be tested;
and (3) taking 10.0-20.0 mL of to-be-tested solution B, adding 1-3 mL of sulfuric acid solution and 3-5 mL of ammonium persulfate solution with the volume ratio of 1:30-1:50, placing the solution on an electric heating sleeve, heating and digesting, and steaming until half of the original volume is finished.
S4, color development and measurement of a sample: transferring the solution cooled to room temperature after 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 fixed volume to a scale, and placing the solution in a water bath at 25-30 ℃ for 15-20 min to generate a color reaction. The absorbance was measured at 710nm using a spectrophotometer using a 1cm path cuvette with reagent blank as reference.
S5, calculating the total phosphorus content: by substituting the measurement result of step S4 into the linear regression equation of step S2, the corresponding phosphate quality can be obtained, and the total Phosphorus (PO) in the sample can be calculated according to the following formula 4 3- ) The content is as follows:
wherein:
m 0 -calculating the total Phosphorus (PO) in the liquid to be tested from the standard curve 4 3- ) The mass unit is mg;
m-the actual mass of the weighing sample, with the unit of g;
V A -measuring the volume of mother liquor A to be measured in mL (V A )；
V B Measuring the volume of the test solution B in mL (V B )；
V 1 The total volume of the mother liquor A to be measured is in mL (V 1 )；
V 2 The total volume of the test solution B to be tested is in mL (V 2 )。
1. As an improvement of the present invention, the step S1 of preparing the solution comprises the steps of:
s1.1, ammonium molybdate-sulfuric acid solution (25.0 g/L-30.0 g/L): 12.5 g-15.0 g of ammonium molybdate solid is weighed and dissolved in about 80mL of water to obtain an ammonium molybdate aqueous solution, 0.30-0.40 g of antimony potassium tartrate solid is weighed and dissolved in about 80mL of water to obtain an antimony potassium tartrate solution, the ammonium molybdate aqueous solution is firstly added into 300mL of sulfuric acid solution with the volume ratio of 1:1-1:3, then the antimony potassium tartrate solution is added, the antimony potassium tartrate solution is transferred into a 500mL brown volumetric flask after being cooled, the antimony potassium molybdate aqueous solution is carefully diluted to the scale and is uniformly mixed, and the antimony potassium tartrate aqueous solution is placed into the brown volumetric flask after being cooled and sealed at low temperature for storage, and the storage period is not suitable to exceed two months.
S1.2, ascorbic acid solution (30.0 g/L-35.0 g/L): 30.0 g-35.0 g of ascorbic acid solid is weighed and dissolved in 500mL of water, 0.20 g-0.25 g of disodium ethylenediamine tetraacetate and 8 mL-10 mL of formic acid are added, the solution is diluted to a constant volume of 1L, and the solution is sealed in a brown bottle for low-temperature storage after uniform mixing, and the storage period is not more 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 constant volume to 50mL, and sealing and storing in dark and cool places, wherein the ammonium persulfate is prepared at present to prevent hydrolysis and deterioration.
S1.4, phosphorus standard solution (0.01 mg/mL or 0.02 mg/mL): firstly, a certain amount of potassium dihydrogen phosphate is placed under the condition of 110+/-5 ℃ and baked for 2-4 hours, 0.1430g (accurate to +/-0.2 mg) of solid is weighed after cooling, and the solid is diluted and fixed to 1L to obtain stock solution (0.1 mg/mL); and then 50.0mL of stock solution is taken, diluted and fixed to 500mL or 250mL to obtain the phosphorus standard solution.
As an improvement of the invention, the method for preparing the ammonium molybdate-sulfuric acid solution in the step S1.1 has more remarkable advantages compared with the national standard method and the line standard method, and the experimental results of the three preparation methods are shown in the table 1.
TABLE 1 experimental results of the preparation of 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 successfully prepared, and the method has good feasibility and repeatability;
b. compared with the national standard method, the method provided by the invention uses H with the volume ratio of 1:1, 1:1.5, 1:2 and 1:3 2 SO 4 The solution can meet the preparation requirement, and the environment with higher acidity ensures that ammonium molybdate exists stably in the solution, greatly reduces the consumption of concentrated sulfuric acid reagent, saves the experiment cost, and improves the experiment safety and controllability.
c. By comparing the experimental phenomena of the three methods, the preparation process of the ammonium molybdate-sulfuric acid solution is easy to be interfered by a plurality of factors. As the pH of the solution gradually decreased, the heptamolybdate ion ((M) O7 O 24 ) 6- ) Undergo a series of morphological changes to finally transform into white precipitate MoO 3 ·H 2 O; when the acidity of the solution is weaker, the stability of ammonium molybdate is poorer, and when the interference of trace reducing impurities and phosphate radical exists in the solution, the ammonium molybdate can be reduced into low-valence phosphomolybdic heteropolyacid, even phosphomolybdic blue. Directly placing ammonium molybdateIn an acidic environment with low pH, a large amount of H + The existence of the catalyst 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 reducing impurities and phosphate radical in the solution, and avoid white precipitation or generation of phosphomolybdic heteropolyacid and phosphomolybdic blue, thereby obtaining qualified colorless, clear and transparent ammonium molybdate-sulfuric acid solution.
As an improvement of the invention, the concentrations of the ammonium molybdate-sulfuric acid solution and the ascorbic acid solution prepared in the steps S1.1 and S1.2 and the addition amount of the two reagents in color development have sufficient rationality and flexibility.
As shown in table 2, the molar ratio of the ammonium molybdate concentration, the added amount, the ascorbic acid concentration, the added amount and the maximum value of the content of the treated phosphate in the national standard method and the standard method is compared, and the following conclusion is obtained:
a. the ratio of the upper limit of phosphorus quality detection to the molar quantity of the prepared reagent is partially contained in a feasible interval between a line standard method and a national standard method, and partially exceeds the national standard method, so that the concentration and volume parameter range of the selected reagent can ensure that the phosphate radical in the sample to be treated can fully undergo a color reaction;
b. compared with the national standard method and the line standard method, the method reduces the reagent consumption in single sample measurement, reduces the reagent consumption cost, and reduces the workload of repeated configuration of experimental reagents for experimental staff;
c. in view of the flexibility of operation, the amount or concentration of the reagent to be added is not limited to a certain value, as long as the experimental requirements can be satisfied within this range.
TABLE 2 comparison between the concentration, addition and throughput of solutions formulated by different methods
2. As an improvement of the present invention, the step S2 of drawing the phosphorus standard curve includes the steps of:
s2.1, measuring at least 6 phosphorus standard solutions with different volumes within a certain range, respectively placing the phosphorus standard solutions in 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 constant volume, and standing for 15-20 min under the water bath condition of 25-30 ℃ to generate a color reaction;
s2.3, using a spectrophotometer, adopting a cuvette with an optical path of 1cm, taking a reagent blank as a reference, and measuring the absorbance at 710 nm.
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 quality of phosphate radical is within 0 mg-0.08 mg, because when the quality of phosphate radical is more than 0.08mg, the absorbance readings between parallel samples have larger difference, and an accurate phosphorus standard curve cannot be obtained.
3. As an improvement of the present invention, the digestion process of the sample solution of step S3 comprises the steps of:
s3.1, accurately weighing 0.5000 g-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 for dissolving, transferring into a 250mL or 500mL volumetric flask, diluting and fixing the volume to scale, and obtaining mother liquor A to be measured; and then taking a certain amount of mother solution A to be tested, diluting the mother solution A to a certain volume, and obtaining the liquid B to be tested.
Preferably, the preparation process of the liquid B to be tested is required to follow the principle that dilution is carried out before digestion and direct measurement can be carried out after color development. Wherein, when the scale and corrosion inhibitor to be detected is a high phosphorus sample: 1 mL-5 mL of mother solution A to be tested is measured and diluted to 500mL to obtain solution B to be tested; when the scale and corrosion inhibitor to be detected is a low-phosphorus sample: and 1 mL-5 mL of mother solution A to be tested is measured and diluted to 250mL, so as to obtain solution B to be tested.
The dilution factor of the scale and corrosion inhibitor to be tested can be flexibly adjusted according to the initial experimental result, the weighing amount of the scale and corrosion inhibitor to be tested can be adjusted if necessary, the experiment is repeated for a plurality of times, and the back calculation error can be reduced to the greatest extent under the most suitable dilution factor, so that the more accurate experimental result is obtained.
S3.2, weighing 10.0-20.0 mL of to-be-tested solution B, adding a 100mL conical flask, adding 1-3 mL of sulfuric acid solution and 3-5 mL of ammonium persulfate solution with the volume ratio of 1:30-1:50, and heating the mixture on an electric heating sleeve to perform digestion reaction. When the volume of the solution in the flask was reduced to half of the original volume, the flask was removed and cooled to room temperature.
The ammonium persulfate is taken as a strong oxidizing medium, and sulfuric acid with the volume ratio of 1:30-1:50 is added in the digestion process to provide a certain acidic environment for digestion, and the ammonium persulfate can be decomposed under the acidic heating condition, so that the organic phosphine is converted into phosphate radical. However, if too concentrated acid is added during digestion, the subsequent color development process of phosphate radical is seriously affected, and the reason is mainly that the too high acidity of the solution can reduce the stability of phosphomolybdenum blue, so that the color development capability of the phosphomolybdenum blue is weakened, the ammonium molybdate-sulfuric acid solution in the color developing agent has certain acidity, and the color development effect is poor due to the superposition of the residual acid in the residual liquid after digestion and the acid effect generated by the residual acid, 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 more than 30 minutes, because the absorbance will show different degree of descending trend after the measurement time is more than 30 minutes, and the accuracy of the phosphorus content measurement cannot be ensured.
Example 1
The method for detecting the total phosphorus content in the scale and corrosion inhibitor for the industrial circulating cooling water comprises the following steps:
1. preparation of reagent solutions required by experiments:
(1) Ammonium molybdate-sulfuric acid solution (30.0 g/L): 15.0g of ammonium molybdate solid is weighed and dissolved in about 80mL of water, 0.36g of antimony potassium tartrate solid is weighed and dissolved in about 80mL of water, firstly, an ammonium molybdate aqueous solution is added into 300mL of sulfuric acid solution with the volume ratio of 1:1, then, the antimony potassium tartrate solution is added into the sulfuric acid solution, after the antimony potassium tartrate solution is cooled, the antimony potassium tartrate solution is transferred into a 500mL brown volumetric flask, carefully diluted to scale and uniformly mixed, and the antimony potassium tartrate solution is placed into the brown volumetric flask for sealing and low-temperature storage after being cooled, and the storage period is not more than two months.
(2) Ascorbic acid solution (35.0 g/L): 35.0g of ascorbic acid solid is weighed and dissolved in 500mL of water, 0.23g of disodium ethylenediamine tetraacetate and 9mL of formic acid are added, the solution is diluted to a volume of 1L, and after uniform mixing, the solution is stored in a brown bottle in a sealed low-temperature manner, and the storage period is not more than one month.
(3) Ammonium persulfate solution (42.0 g/L): 2.1g of ammonium persulfate is weighed, diluted to a constant volume of 50mL, stored in a dark place and a cool place, and prepared at present to prevent the hydrolysis and deterioration of the ammonium persulfate.
(4) Phosphorus standard solution (0.02 mg/mL): firstly, a certain amount of potassium dihydrogen phosphate is placed at 110 ℃ and dried for 4 hours, 0.1430g of solid is weighed after cooling, and the solid is diluted to a constant volume of 1L to obtain stock solution; and then 50.0mL of stock solution is taken, diluted and fixed to 250mL to obtain standard solution.
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 the phosphorus standard solutions into a 50mL volumetric flask, adding a small amount of water, and standing;
(2) Adding 4mL of ammonium molybdate-sulfuric acid solution and 4mL of ascorbic acid solution into the above solutions respectively, diluting with water to constant volume, and standing for 20min under the water bath condition of 30 ℃ to generate a color reaction;
(3) The absorbance was measured at 710nm using a spectrophotometer using a 1cm path cuvette with 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 quality 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 are more concentrated, the precision is higher, and the repeatability is better;
b. when the phosphorus mass is more than 0.08mg, the standard deviation of the measurement 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 (0.03 mg) measured by the national standard method and the upper limit (0.1 mg) measured by the line standard method, the upper limit (0.08 mg) measured by the method can effectively ensure the accuracy and precision of the detection result.
(4) According to the above experimental conclusion, experimental data of adding 0.0mL, 0.5mL, 1.0mL, 1.5mL, 2.0mL, 3.0mL, 4.0mL of phosphorus standard solution, respectively, were selected as the mass of phosphorus (as PO 4 3- Meter) is the abscissa, absorbance is the ordinate, and a phosphorus standard curve is drawn to obtain a linear regression equation, as shown in fig. 1. From linear correlation coefficient R 2 It can be seen that when the phosphate mass is in the range of 0mg to 0.08mg, the absorbance and the phosphate mass show a good linear correlation.
3. Determination of total phosphorus content in high phosphorus content scale and corrosion inhibitor:
3.1 preparation of the 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 into a 250mL volumetric flask, diluting to a certain volume, and obtaining mother liquor A to be measured; and then 1mL of mother solution A to be tested is measured and placed in a 500mL volumetric flask, and diluted to a certain volume to obtain solution B to be tested.
(2) And (3) marking: weighing 1.0001g of scale and corrosion inhibitor to be tested, placing the scale and corrosion inhibitor into a 250mL volumetric flask, diluting to a certain volume, and obtaining mother liquor A to be tested; and 5mL of mother solution A to be tested is measured, and the mother solution A to be tested is placed in a 500mL volumetric flask, diluted and fixed in volume, so as to obtain the liquid B to be tested.
3.2 digestion of the solution to be tested:
and taking 20.0mL of the solution B to be tested, adding a 100mL conical flask, adding 3mL of sulfuric acid solution and 5mL of ammonium persulfate solution with the volume ratio of 1:30, and heating the mixture on an electric heating sleeve to perform digestion reaction. When the volume of the solution in the flask was reduced to half of the original volume, the flask was removed and cooled to room temperature.
3.3 color development and measurement of the test solution to be tested:
(1) The method comprises the following steps: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 4mL of ammonium molybdate-sulfuric acid solution and 4mL of ascorbic acid solution, diluting to a fixed volume to a scale, placing in a water bath at 30 ℃ for 20min, using a spectrophotometer, adopting a 1cm optical path cuvette, taking a reagent blank as a reference, measuring the absorbance at 710nm, and the experimental result is shown in Table 4.
(2) And (3) marking:
a. direct measurement without dilution: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 4mL of ammonium molybdate-sulfuric acid solution and 4mL of ascorbic acid solution, diluting to a fixed volume to a scale, placing in a water bath at 30 ℃ for 20min, using a spectrophotometer, adopting a 1cm optical path cuvette, taking a reagent blank as a reference, measuring the absorbance at 710nm, and the experimental result is shown in Table 4.
b. 10-fold dilution after development: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 4mL of ammonium molybdate-sulfuric acid solution and 4mL of ascorbic acid solution, diluting to a certain volume to a scale, and placing in a water bath at 30 ℃ for 20min; taking 5mL of the developed solution, adding the solution into a 50mL volumetric flask, diluting to a fixed volume to a scale, shaking uniformly, using a spectrophotometer, adopting a 1cm optical path cuvette, taking a reagent blank as a reference, measuring the absorbance at 710nm, ensuring that the measurement is completed within 30min, and the experimental results are shown in Table 4.
Calculating the total phosphorus content in the scale and corrosion inhibitor to be measured:
wherein:
m 0 -calculating the total Phosphorus (PO) in the liquid to be tested from the standard curve 4 3- ) The mass unit is mg;
m-the actual mass of the weighing sample, with the unit of g;
V A -measuring the volume of mother liquor A to be measured in mL (V A )；
V B Measuring the volume of the test solution B in mL (V B )；
V 1 The total volume of the mother liquor A to be measured is in mL (V 1 )；
V 2 The total volume of the test solution B to be tested is in mL (V 2 )。
TABLE 4 determination of total phosphorus of high phosphorus scale and corrosion inhibitor
Example 2
1. Preparation of reagent solutions required by experiments:
the procedure of example 1 was repeated except that ammonium molybdate-sulfuric acid solution (25.0 g/L) (sulfuric acid solution having a volume ratio of 1:3 was used), ascorbic acid solution (30.0 g/L), ammonium persulfate solution (40.0 g/L), and phosphorus standard solution (0.02 mg/mL).
2. Phosphorus standard curve determination:
the detailed experimental procedure was the same as in example 1, except that 2mL of ammonium molybdate-sulfuric acid solution and 2mL of ascorbic acid solution were added at the time of color development as phosphorus mass (as PO 4 3- Meter) is taken as an abscissa, absorbance is taken as an ordinate, a phosphorus standard curve is drawn, a linear regression equation is obtained, y=3.2804x+0.0032, r 2 =0.9999, as shown in fig. 2.
3. Determination of total phosphorus content in the low phosphorus content scale and corrosion inhibitor:
3.1 preparation of the test solution:
(1) The method comprises the following steps: weighing 0.8001g of scale and corrosion inhibitor to be measured, placing the scale and corrosion inhibitor into a 250mL volumetric flask, and diluting to a certain volume to obtain mother liquor A to be measured; and 2mL of mother solution A to be tested is measured, and the mother solution A to be tested is placed in a 250mL volumetric flask, diluted and fixed in volume, so as to obtain liquid B to be tested.
(2) And (3) marking: weighing 1.0000g of scale and corrosion inhibitor to be measured, placing the scale and corrosion inhibitor into a 250mL volumetric flask, diluting to a certain volume, and obtaining mother solution A to be measured; and 5mL of mother solution A to be tested is measured, and the mother solution A to be tested is placed in a 250mL volumetric flask, diluted and fixed in volume, so as to obtain the liquid B to be tested.
3.2 digestion of the solution to be tested:
taking 20.0mL of the solution B to be tested, adding a 100mL conical flask, adding 1mL of sulfuric acid solution and 3mL of ammonium persulfate solution with the volume ratio of 1:50, and placing the solution on an electric heating sleeve for heating to perform digestion reaction. When the volume of the solution in the flask was reduced to half of the original volume, the flask was removed and cooled to room temperature.
3.3 color development and measurement of the test solution to be tested:
(1) The method comprises the following steps: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 2mL of ammonium molybdate-sulfuric acid solution and 2mL of ascorbic acid solution, diluting to a fixed volume to a scale, placing in a water bath at 25 ℃ for 15min, using a spectrophotometer, adopting a 1cm cuvette, taking a reagent blank as a reference, measuring the absorbance at 710nm, and the experimental result is shown in Table 5.
(2) And (3) marking:
a. direct measurement without dilution: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 2mL of ammonium molybdate-sulfuric acid solution and 2mL of ascorbic acid solution, diluting to a fixed volume to a scale, placing in a water bath at 25 ℃ for 15min, using a spectrophotometer, adopting a 1cm optical path cuvette, taking a reagent blank as a reference, measuring the absorbance at 710nm, and the experimental result is shown in Table 5.
b. 5-fold dilution after development: transferring the test solution cooled to room temperature after digestion in the previous step into a 50mL volumetric flask, adding 2mL of ammonium molybdate-sulfuric acid solution and 2mL of ascorbic acid solution, diluting to a certain volume to a scale, and placing in a water bath at 25 ℃ for 15min; 20.0mL of the developed solution is taken and added into a 50mL volumetric flask, diluted to a fixed volume to a scale, shaken uniformly, and then a spectrophotometer is utilized to measure the absorbance of the solution at 710nm by taking a reagent blank as a reference and adopting a 1cm optical path cuvette, so that the measurement is completed within 30min, and the experimental result is shown in Table 5.
Calculating the total phosphorus content in the scale and corrosion inhibitor to be measured:
wherein:
m 0 -calculating the total Phosphorus (PO) in the liquid to be tested from the standard curve 4 3- ) The mass unit is mg;
m-the actual mass of the weighing sample, with the unit of g;
V A ——the volume of mother liquor A to be measured is measured in mL (V A )；
V B Measuring the volume of the test solution B in mL (V B )；
V 1 The total volume of the mother liquor A to be measured is in mL (V 1 )；
V 2 The total volume of the test solution B to be tested is in mL (V 2 )。
TABLE 5 Total phosphorus determination results for Low phosphorus scale and Corrosion inhibitor
Example 3
Three samples with known total phosphorus content are taken, different amounts of phosphorus standard solutions are respectively added, and a labeling recovery experiment is carried out according to the detection method of the invention.
The detailed procedure was the same as in example 1, except that ammonium molybdate-sulfuric acid solution (28.0 g/L) (sulfuric acid solution having a volume ratio of 1:2 was used), ascorbic acid solution (32.0 g/L), ammonium persulfate solution (41.0 g/L); 2mL of sulfuric acid solution and 4mL of ammonium persulfate solution with volume ratio of 1:40 are added during digestion; 3mL of ammonium molybdate-sulfuric acid solution and 3mL of ascorbic acid solution were added for color development, and the color development was performed in a water bath at 28℃for 18min, and the results are shown in Table 6.
Table 6 labeling recovery experiment results
From the above two embodiments and the labeled recovery experiment, it can be seen that:
(1) Compared with the method, the total phosphorus content detected by the line marking method is lower, and the reason is that: when the total phosphorus in the sample to be tested is directly measured after the sample solution is undiluted and developed, the total phosphorus content in the sample solution is high, the amount of the added color developing agent and the digestion agent or the development time of 15min is insufficient to ensure that the digestion reaction and the development reaction take place sufficiently, and the phosphorus content is far more than the upper limit of the stable absorbance reading of the sample solution, so that reliable experimental data cannot be obtained; when the total phosphorus is measured by diluting the test solution for a certain multiple after the color development, the content of the phosphorus can be ensured to be within a detection range with stable absorbance, but the problems of insufficient digestion and color development of the total phosphorus are also existed, and a back calculation error exists, so that the measurement results are low.
(2) The experimental data of the sample to be measured in the standard method is more dispersed when the total phosphorus is directly measured after undiluted and developed, the standard deviation is larger, and 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 are concentrated, the standard deviation is smaller, the value is within 0.5%, and the result proves that the method has good repeatability.
(3) The relative standard deviation of the sample to be measured in the standard method is larger when the total phosphorus is directly measured after undiluted and developed, and the maximum value of the relative standard deviation is even more than 5%; the relative standard deviation of the total phosphorus detection method is smaller, the value of the total phosphorus detection method 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 adding 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 summary, the detection method adopted by the embodiment of the invention has the advantages of simple operation, economy, safety, high efficiency, flexibility, higher accuracy, higher precision and better reproducibility of results, and can be widely applied to the detection method of the total phosphorus content in the scale and corrosion inhibitor.
The above specific embodiments are to be considered 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 (5)
1. The method for detecting the total phosphorus content in the scale and corrosion inhibitor for the industrial circulating cooling water is characterized by comprising the following steps of:
s1, adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-35.0 g/L ascorbic acid solution into a series of phosphorus standard solutions with different concentrations for color development, measuring the absorbance of the solution, and drawing a phosphorus standard curve to obtain a linear regression equation;
s2, adding a sulfuric acid solution and an ammonium persulfate solution with the volume ratio of 1:30-1:50 and 40.0 g/L-42.0 g/L into the twice diluted scale and corrosion inhibitor test solution to be tested for digestion;
s3, adding 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution and 30.0 g/L-35.0 g/L ascorbic acid solution into the digested scale and corrosion inhibitor test solution to be tested for color development, measuring absorbance, and obtaining the total phosphorus content in the scale and corrosion inhibitor to be tested according to the linear regression equation obtained in the step S1;
in the steps S1 and S3, the preparation method of the 25.0 g/L-30.0 g/L ammonium molybdate-sulfuric acid solution comprises the following steps: respectively dissolving 12.5 g-15.0 g of ammonium molybdate solid and 0.30 g-0.40 g of antimony potassium tartrate solid in 80mL water to obtain an ammonium molybdate aqueous solution and an antimony potassium tartrate solution, adding the ammonium molybdate aqueous solution into a sulfuric acid solution with a volume ratio of 300mL being 1:1-1:3 to obtain a mixed solution, adding the antimony potassium tartrate solution into the mixed solution, cooling, transferring into a 500mL brown volumetric flask, fixing the volume, and placing into a brown flask for sealing and low-temperature storage;
in the step S2, the 0.5000 g~1.0000 g scale and corrosion inhibitor to be detected is diluted for the first time to a fixed volume, and the fixed volume is kept to 250mL or 500mL, so as to obtain mother liquor A to be detected; performing secondary dilution and constant volume on the mother solution A to be tested to obtain a solution B to be tested;
when the scale and corrosion inhibitor to be detected is a high phosphorus sample: 1 mL-5 mL of mother solution A to be tested is measured and diluted to 500mL, and solution B to be tested is obtained; when the scale and corrosion inhibitor to be detected is a low-phosphorus sample: 1 mL-5 mL of mother solution A to be tested is measured and diluted to 250mL, and solution B to be tested is obtained;
in the steps S1 and S3, adding 2-4 mL of ammonium molybdate-sulfuric acid solution and 2-4 mL of ascorbic acid solution for color development;
in the steps S1 and S3, the color development is carried out for 15-20 min under the water bath condition of 25-30 ℃; the absorbance was measured using a spectrophotometer at 710 nm.
2. 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 step S1, the mass range of phosphate radical in the phosphorus standard solution is 0 mg-0.08 mg.
3. 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 step S2, 1 mL-3 mL of sulfuric acid solution and 3 mL-5 mL of ammonium persulfate solution are added into 10.0 mL-20.0 mL of to-be-detected solution B, and the solution is 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.
4. The method for detecting total phosphorus content in scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in the steps S1 and S3, the time from color development to absorbance measurement is not more than 30min.
5. The method for detecting total phosphorus content in scale and corrosion inhibitor for industrial circulating cooling water according to claim 1, wherein in the steps S1 and S3, absorbance measurement is carried out according to the order of the phosphorus content from low to high, and after each measurement is completed, the cuvette is rinsed with clear water or alkaline washing liquid.
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