Method for measuring content of cyanate radicals in waste water containing thiocyanate radicals and cyanate radicals

Abstract

The invention relates to a method for measuring the content of cyanic acid radicals in thiocyanic acid radical and cyanic acid radical wastewater, which comprises the following steps: S1, measuring the absorbance A1 of a first part of a to-be-measured sample by using ferric nitrate spectrophotometry, and calculating the concentration C (SCN-) of SCN-in the first part of the to-be-measured sample according to the formula C (SCN-) = K1 * A1, the value range of K1 being 25.05 + / -1.35; s2, measuring the absorbance A3 of the second part of the to-be-detected sample by adopting an isonicotinic acid-barbituric acid spectrophotometric method; s3, calculating the concentration C (CN-) of CN-in the sample to be detected according to a formula C (CN-) = K3 * (A3-A2), wherein A2 is equal to K2 * C (SCN <->), the value range of K2 is 0.8969 + / -0.0541, and the value range of K3 is 0.5906 + / -0.0320. The method provided by the invention can effectively shield the interference of the thiocyanate radical in the wastewater on the detection of the cyanide, and is simple in operation method and rapid in detection.

Description

Technical Field

[0001] The present application relates to a method for determining the cyanate content in wastewater containing thiocyanate and cyanate. Background Art

[0002] In recent years, many industrial wastewaters contain cyanide, such as coal chemical wastewater, acrylic wastewater, etc. These wastewaters are highly toxic and have complex water components, requiring accurate and rapid detection technology. - Industrial wastewater often contains a large amount of other substances that interfere with the determination of cyanide, especially SCN. - In the case of the traditional national standard method (GB7486-87), when chloramine T and isonicotinic acid barbituric acid are used as color developers, the color developer and SCN - , CN - All of them can complex and develop color, thus seriously interfering with CN - The conventional pretreatment method requires long-term distillation, and the on-site measurement conditions often do not have sufficient experimental conditions. Therefore, a method that can be fast, accurate, and shield SCN is needed. - Affected CN - Measurement method. Summary of the invention

[0003] The purpose of the present invention is to provide a method for determining the cyanate content in wastewater containing thiocyanate and cyanate, which can effectively shield the interference of thiocyanate in the wastewater on cyanide detection, has simple operation method and rapid detection.

[0004] In order to achieve the above object, the present invention provides a method for determining the cyanate content in wastewater containing thiocyanate and cyanate, the method comprising:

[0005] S1, using ferric nitrate spectrophotometry to measure the absorbance A1 of the first part of the sample to be tested, and according to the formula C (SCN - )=K1×A1Calculate the SCN in the first part of the sample to be tested - The concentration C(SCN - ), K1 value range is 25.05±1.35;

[0006] S2, measuring the absorbance A3 of the second part of the sample to be tested by isonicotinic acid-barbituric acid spectrophotometry;

[0007] S3, according to the formula C(CN - )=K3×(A3-A2) to calculate CN in the sample to be tested - The concentration of C(CN - ); where A2=K2×C(SCN -), the value range of K2 is 0.8969±0.0541, and the value range of K3 is 0.5906±0.0320.

[0008] Optionally, in step S1, the measuring the absorbance A1 of the first part of the sample to be tested by ferric nitrate spectrophotometry includes: mixing the first part of the sample to be tested with ferric nitrate solution and fixing the volume, and measuring the absorbance A1 at 460 nm on a spectrophotometer.

[0009] Optionally, in step S1, relative to 10 mL of the first portion of the sample to be tested, the amount of the ferric nitrate solution is 4.8-5.2 mL, and the total volume of the first mixed solution obtained after constant volume is 50 mL.

[0010] Optionally, Fe(NO3)3·9H2O, water and concentrated nitric acid are mixed and fixed to volume to obtain the ferric nitrate solution; the concentration of the ferric nitrate solution is 0.12-0.13 mol / L; relative to 10g of Fe(NO3)3·9H2O, the amount of concentrated nitric acid used is 4-6mL.

[0011] Optionally, in step S2, the method of measuring the absorbance A3 of the second part of the sample to be tested by isonicotinic acid-barbituric acid spectrophotometry includes: mixing the second part of the sample to be tested, a buffer solution, a chloramine T solution and an isonicotinic acid-barbituric acid solution and making up the volume, and measuring the absorbance A3 at 600 nm on a spectrophotometer.

[0012] Optionally, in step S2, relative to 10 mL of the second part of the sample to be tested, the amount of the buffer solution is 5-8 mL, the amount of the chloramine T solution is 0.3-0.4 mL, the amount of the isonicotinic acid-barbituric acid solution is 5-6 mL, and the total volume of the second mixed solution obtained after constant volume is 25 mL.

[0013] Optionally, the buffer solution is selected from one or more of potassium dihydrogen phosphate buffer solution, sodium dihydrogen phosphate and acetic acid-sodium acetate, preferably potassium dihydrogen phosphate buffer solution; the concentration of the buffer solution is 0.95-1.05 mol / L; the concentration of the chloramine T solution is 9.5-10.5 g / L; the concentration of isonicotinic acid in the isonicotinic acid-barbituric acid solution is 23.75-26.25 g / L, and the concentration of barbituric acid is 11.875-13.125 g / L.

[0014] Optionally, the method further comprises: mixing anhydrous potassium dihydrogen phosphate and water, fixing the volume, and then adding glacial acetic acid to obtain the potassium dihydrogen phosphate buffer solution;

[0015] Relative to 100 g of anhydrous potassium dihydrogen phosphate, the amount of glacial acetic acid used is 1.4-1.5 mL.

[0016] Optionally, the detection limit of the isonicotinic acid-barbituric acid spectrophotometry for cyanate is 0.005-0.5 mg / L, and the detection limit of thiocyanate is 0.01-1 mg / L;

[0017] The detection limit of the thiocyanate by the ferric nitrate spectrophotometry is 0.2-20 mg / L.

[0018] Optionally, the measurement error of the method is less than 5.5%.

[0019] Through the above technical solution, the method disclosed in the present invention can effectively shield SCN in wastewater. - About CN - The operation method is simple, the detection is rapid, and CN can be accurately detected without complicated preprocessing. - The content provides convenience for on-site rapid detection of actual wastewater treatment processes.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 is the SCN of the ferric nitrate spectrophotometry in the method of the present invention - The standard curve of

[0023] Figure 2 The isonicotinic acid-barbituric acid spectrophotometric method SCN in the method of the present invention - The standard curve of

[0024] Figure 3 The isonicotinic acid-barbituric acid spectrophotometric method CN in the method of the present invention - The standard curve of DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0026] The present invention provides a method for determining the content of cyanate in wastewater containing thiocyanate and cyanate, the method comprising: S1, using ferric nitrate spectrophotometry to measure the absorbance A1 of the first part of the sample to be tested, and according to the formula C(SCN - )=K1×A1Calculate the SCN in the first part of the sample to be tested -The concentration C(SCN - ); K1 has a value range of 25.05±1.35; S2, using isonicotinic acid-barbituric acid spectrophotometry to measure the absorbance A3 of the second part of the sample to be tested; S3, according to the formula C(CN - )=K3×(A3-A2) to calculate CN in the sample to be tested - The concentration of C(CN - ); where A2 = 0.8969 × C (SCN - ), the value range of K2 is 0.8969±0.0541, and the value range of K3 is 0.5906±0.0320.

[0027] In the present invention, A2 represents SCN - The absorbance contributed in the isonicotinic acid-barbituric acid colorimetric method, the first part of the sample to be tested and the second part of the sample to be tested come from the same wastewater to be tested. The method of the present invention combines the two colorimetric methods of ferric nitrate spectrophotometry and isonicotinic acid-barbituric acid spectrophotometry to measure wastewater, which can effectively shield the interference of thiocyanate in wastewater on cyanate detection, has a simple operation method, rapid detection, no need for complex pretreatment process, and can achieve on-site rapid detection of wastewater treatment process.

[0028] In a preferred embodiment of the present disclosure, K1 is 25.05, K2 is 0.8969, and K3 is 0.5906.

[0029] In a specific embodiment of the present invention, in step S1, the absorbance A1 of the first part of the sample to be tested is measured by the ferric nitrate spectrophotometry method, comprising: mixing the first part of the sample to be tested with a ferric nitrate solution and fixing the volume, and measuring the absorbance A1 at 460 nm in a spectrophotometer. In a preferred embodiment, after the first part of the sample to be tested is added to a stoppered colorimetric tube, a ferric nitrate solution is added and fixed to the mark with water, and then the color is developed for 2-3 minutes, and the absorbance A1 is measured at 460 nm in a spectrophotometer using a 1 cm colorimetric dish and a sample blank as a reference solution.

[0030] In a specific embodiment of the present invention, in step S1, relative to 10 mL of the first portion of the sample to be tested, the amount of the ferric nitrate solution is 4.8-5.2 mL, and the total volume of the first mixed solution obtained after constant volume is 50 mL.

[0031] In the present invention, the preparation method of ferric nitrate solution is well known to those skilled in the art. In a preferred embodiment of the present invention, Fe(NO3)3·9H2O, water and concentrated nitric acid are mixed and constant volume is obtained to obtain the ferric nitrate solution. According to the present invention, the concentration of the ferric nitrate solution can vary in a large range, preferably the concentration of the ferric nitrate solution is 0.12-0.13 mol / L, more preferably 0.122-0.126 mol / L; relative to 10g of Fe(NO3)3·9H2O, the amount of concentrated nitric acid can also vary in a large range, preferably 4-6mL, more preferably 4.9-5.1mL.

[0032] In the present invention, the isonicotinic acid-barbituric acid spectrophotometry can adopt the "Total Cyanide Determination Method" (GB7486-87) well known to those skilled in the art. In a specific embodiment of the present invention, in step S2, the absorbance A3 of the second part of the sample to be tested is measured by the isonicotinic acid-barbituric acid spectrophotometry, comprising: mixing the second part of the sample to be tested, the buffer solution, the chloramine T solution and the isonicotinic acid-barbituric acid solution and making up the volume, and measuring the absorbance A3 at 600 nm on a spectrophotometer.

[0033] In a specific embodiment of the present invention, in step S2, relative to 10 mL of the second part of the sample to be tested, the amount of the buffer solution is 5-8 mL, preferably 5.5-6.5 mL, the amount of the chloramine T solution is 0.3-0.4 mL, preferably 0.35 mL, the amount of the isonicotinic acid-barbituric acid solution is 5-6 mL, preferably 6 mL, and the total volume of the second mixed solution obtained after constant volume is 25 mL.

[0034] In a specific embodiment of the present invention, the buffer solution is selected from one or more of potassium dihydrogen phosphate buffer solution, disodium hydrogen phosphate buffer solution and acetic acid-sodium acetate buffer solution, preferably potassium dihydrogen phosphate buffer solution; the concentration of the buffer solution is 0.95-1.05 mol / L; the concentration of the chloramine T solution is 9.5-10.5 g / L; the concentration of isonicotinic acid in the isonicotinic acid-barbituric acid solution is 23.75-26.25 g / L and the concentration of barbituric acid is 11.875-13.125 g / L.

[0035] In the present invention, the buffer solution, chloramine T solution and isonicotinic acid-barbituric acid solution can be prepared by methods well known to those skilled in the art.

[0036] In a specific embodiment of the present invention, the method further comprises: mixing anhydrous potassium dihydrogen phosphate and water, fixing the volume, and then adding glacial acetic acid to obtain the potassium dihydrogen phosphate buffer solution; relative to 100g of anhydrous potassium dihydrogen phosphate, the amount of water used is 0.734L, and the amount of glacial acetic acid used is 1.4-1.5mL.

[0037] The colorimetric standard curve involved in the present invention is highly linear, and the ferric nitrate spectrophotometric method is used to measure SCN. - The variance of the concentration calibration curve (R 2 ) is 0.9993, and SCN is measured by isonicotinic acid-barbituric acid spectrophotometry - R of the concentration curve 2 is 0.9998, isonicotinic acid-barbituric acid spectrophotometric method for CN - R of the concentration curve 2 is 0.9997, which can be used in shielded SCN - Accurately detect CN under the influence of - concentration.

[0038] In a specific embodiment of the present invention, the detection limit of the isonicotinic acid-barbituric acid spectrophotometry for cyanate is 0.005-0.5 mg / L, and the detection limit of the thiocyanate is 0.01-1 mg / L; the detection limit of the ferric nitrate spectrophotometry for thiocyanate is 0.2-20 mg / L.

[0039] In a specific embodiment of the present invention, the measurement error of the method is less than 5.5%.

[0040] The method of the invention can effectively shield the interference of thiocyanate in wastewater on cyanide detection, has simple operation method, rapid detection and relatively accurate detection result.

[0041] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0042] The wastewater used in the following examples and comparative examples is the wastewater from the acrylic fiber production of Anqing Petrochemical, which is a typical cyanide-containing wastewater in the petrochemical industry and contains a certain concentration of SCN. - , interference CN - Determination of.

[0043] Example 1

[0044] This embodiment provides a method for rapidly determining the content of SCN using the method of the present invention. - CN in wastewater - The steps for determining the standard curve are as follows:

[0045] The principle of the ferric nitrate colorimetric method is that when the pH is 0.5 to 1.5, trivalent iron ions react with SCN- to produce a deep red coordination compound with relatively stable absorbance. In the present invention, the standard curve of the ferric nitrate spectrophotometric method is obtained by measuring the method comprising the following steps: preparing a ferric nitrate solution (with a concentration of 0.124 mol / L, weighing Fe(NO3)3·9H2O 50g dissolved in 500mL water, add 25mL concentrated nitric acid, dilute to 1L with water), thiocyanate standard solution (concentration is 100.0μg / mL, weigh 0.1673g potassium thiocyanate and dissolve in water, transfer to a 1L volumetric flask, dilute to the scale with water, and shake well. When drawing the calibration curve, take 6 50mL stoppered colorimetric tubes, add the volumes of 100.0μg / mL thiocyanate standard solution respectively: 0, 0.50mL, 1.0mL, 2.0mL, 3.0mL, 5.0mL, add 5mL of ferric nitrate solution, dilute to the mark with water and shake well. At a wavelength of 480nm, use a 1cm colorimetric dish and the sample blank as the reference solution to measure the absorbance. The absorbance A1 value is the ordinate and SCN is the reference solution. - The concentration is the horizontal axis, and the SCN of the ferric nitrate spectrophotometer is - Standard curve, such as Figure 1 shown.

[0046] The principle of the isonicotinic acid-barbituric acid colorimetric method is that under weakly acidic conditions, cyanide in the water sample reacts with ammonium chloride T to generate hydrogen chloride, which then reacts with isonicotinic acid, hydrolyzes to form glutaraldehyde, and finally reacts with barbituric acid to generate a blue-purple compound, whose chromaticity is proportional to the mass concentration within a certain range. In addition, SCN - It also generates blue-violet compounds when reacting with the developer.

[0047] To eliminate SCN - Interference, first establish a separate SCN -Standard curve in the isonicotinic acid-barbituric acid colorimetric method. Prepare potassium dihydrogen phosphate buffer solution (the method is to weigh 136.1g of anhydrous potassium dihydrogen phosphate and dissolve it in water, dilute it to 1000mL, add 2mL of glacial acetic acid and shake well), ammonium chloride T solution (the preparation method is to weigh 1.0g of chloramine T and dissolve it in water, dilute it to 100mL, and prepare it before use), isonicotinic acid-barbituric acid colorimetric agent (the preparation method is to weigh 2.5g of isonicotinic acid and 1.25g of barbituric acid and dissolve it in sodium hydroxide solution, dilute it to 100mL, and prepare it before use), sodium hydroxide solution (the preparation method is to weigh 15g of sodium hydroxide and dissolve it in 1000mL of water), and thiocyanate standard solution (the concentration is 10.0μg / mL, and the above thiocyanate standard solution is diluted 10 times). When drawing the calibration curve, take 8 25mL stoppered colorimetric tubes, add 100.0μg / mL thiocyanate standard solution in the following volumes: 0, 0.10mL, 0.20mL, 0.30mL, 0.40mL, 0.50mL, 0.80mL, 1.0mL, dilute to 10mL with water, add 5mL of potassium dihydrogen phosphate buffer solution to each tube, quickly add 0.3mL of chloramine T solution, shake well and let stand for 1min, then add 6.0mL of isonicotinic acid-barbituric acid color developer, dilute to the mark with water, and mix well. Color develop at room temperature for 10min, measure the absorbance at 600nm in a spectrophotometer using a 10mm cuvette and the reagent blank (zero concentration) as the reference. Use the absorbance A2 value as the ordinate and SCN as the horizontal coordinate. - The concentration is the horizontal axis, and the SCN of isonicotinic acid-barbituric acid spectrophotometry is plotted. - Standard curve, such as Figure 2 shown.

[0048] Establish a separate CN - Standard curve in the isonicotinic acid-barbituric acid colorimetric method. The methods for preparing potassium dihydrogen phosphate buffer solution, ammonium chloride T solution, isonicotinic acid-barbituric acid colorimetric agent, and sodium hydroxide solution are the same as above. The cyanide standard solution is 50 mg / L cyanide standard diluted 100 times, and the concentration is 0.5 mg / L. When drawing the calibration curve, take 8 25 mL stoppered colorimetric tubes, add 0.5 mg / L cyanide standard solution in the following volumes: 0, 0.4 mL, 1.0 mL, 2.0 mL, 4.0 mL, 6.0 mL, 8.0 mL, 10 mL, dilute to 10 mL with water, add 5 mL of potassium dihydrogen phosphate buffer solution to each tube, quickly add 0.3 mL of chloramine T solution, shake well and let stand for 1 minute, then add 6.0 mL of isonicotinic acid-barbituric acid colorimetric agent, dilute to the mark with water, and mix well. Color development was carried out at room temperature for 10 minutes, and the absorbance was measured at 600 nm in a spectrophotometer using a 10 mm cuvette and the reagent blank (zero concentration) as a reference. The absorbance A2 value was used as the ordinate and SCN was used as the -The concentration is the horizontal axis, and the CN of "isonicotinic acid-barbituric acid spectrophotometry" is shown in Figure 2. - Standard curve, such as Figure 3 shown.

[0049] The following steps are used to determine the cyanate content in wastewater:

[0050] S1, using iron nitrate spectrophotometry to measure the absorbance of Anqing Petrochemical acrylic fiber production wastewater A1 is 0.2483, and according to the formula C (SCN - )=25.05×A1 to calculate SCN - The concentration is 6.22 mg / L;

[0051] S2. The isonicotinic acid-barbituric acid spectrophotometry was used to detect the Anqing Petrochemical acrylic fiber production wastewater sample diluted 20 times. The absorbance A3 was 0.585. The SCN in the Anqing Petrochemical acrylic fiber production wastewater sample diluted 20 times was - The concentration is 0.311 mg / L. According to the formula A2 = 0.8969 × C (SCN - ) to get SCN - The absorbance contribution of isonicotinic acid-barbituric acid colorimetric method was 0.279.

[0052] S3, according to the formula C(CN - )=0.5906×(A3-A2)The cyanide concentration in the water sample is calculated to be 3.61 mg / L.

[0053] Comparative Example 1

[0054] Using the standard method "Total Cyanide Determination Method" (GB7486-87), after (coagulation, sedimentation, distillation), the cyanide concentration of Anqing Petrochemical acrylic fiber production wastewater was determined to be 3.52 mg / L.

[0055] As can be seen from the above, the measurement error of the method of the present invention is only 2.6% compared with the existing method (Comparative Example 1). The method of the present invention can effectively shield the interference of thiocyanate in wastewater on cyanide detection, and the operation method is simple and the detection is rapid.

[0056] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0057] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0058] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for determining the cyanate content in wastewater containing thiocyanate and cyanate, the method comprising: S1, using ferric nitrate spectrophotometry to measure the absorbance A1 of the first part of the sample to be tested, and according to the formula C (SCN - )=K1×A1Calculate the SCN in the first part of the sample to be tested - The concentration C(SCN - ), K1 value range is 25.05±1.35; S2, measuring the absorbance A3 of the second part of the sample to be tested by isonicotinic acid-barbituric acid spectrophotometry; S3, according to the formula C(CN - )=K3×(A3-A2) to calculate CN in the sample to be tested - The concentration of C(CN - ); where A2=K2×C(SCN - ), the value range of K2 is 0.8969±0.0541, and the value range of K3 is 0.5906±0.0320.

2. The method according to claim 1, wherein: In step S1, the method of measuring the absorbance A1 of the first part of the sample to be tested by ferric nitrate spectrophotometry includes: mixing the first part of the sample to be tested with ferric nitrate solution and fixing the volume, and measuring the absorbance A1 at 460 nm using a spectrophotometer.

3. The method according to claim 2, wherein: In step S1, relative to 10 mL of the first part of the sample to be tested, the amount of the ferric nitrate solution is 4.8-5.2 mL, and the total volume of the first mixed solution obtained after constant volume is 50 mL.

4. The method according to claim 2, wherein: Fe(NO3)3·9H2O, water and concentrated nitric acid are mixed and fixed to volume to obtain the ferric nitrate solution; the concentration of the ferric nitrate solution is 0.12-0.13 mol / L; relative to 10g of Fe(NO3)3·9H2O, the amount of concentrated nitric acid used is 4-6mL.

5. The method according to claim 1, wherein: In step S2, the method of measuring the absorbance A3 of the second part of the sample to be tested by isonicotinic acid-barbituric acid spectrophotometry includes: mixing the second part of the sample to be tested, a buffer solution, a chloramine T solution and an isonicotinic acid-barbituric acid solution and making up the volume, and measuring the absorbance A3 at 600 nm on a spectrophotometer.

6. The method according to claim 4, wherein: In step S2, relative to 10 mL of the second part of the sample to be tested, the amount of the buffer solution is 5-8 mL, the amount of the chloramine T solution is 0.3-0.4 mL, the amount of the isonicotinic acid-barbituric acid solution is 5-6 mL, and the total volume of the second mixed solution obtained after constant volume is 25 mL.

7. The method according to claim 5, wherein: The buffer solution is selected from one or more of potassium dihydrogen phosphate buffer solution, sodium dihydrogen phosphate and acetic acid-sodium acetate, preferably potassium dihydrogen phosphate buffer solution; the concentration of the buffer solution is 0.95-1.05 mol / L; the concentration of the chloramine T solution is 9.5-10.5 g / L; the concentration of isonicotinic acid in the isonicotinic acid-barbituric acid solution is 23.75-26.25 g / L, and the concentration of barbituric acid is 11.875-13.125 g / L.

8. The method according to claim 7, wherein: The method further comprises: mixing anhydrous potassium dihydrogen phosphate and water, fixing the volume, and then adding glacial acetic acid to obtain the potassium dihydrogen phosphate buffer solution; Relative to 100 g of anhydrous potassium dihydrogen phosphate, the amount of glacial acetic acid used is 1.4-1.5 mL.

9. The method according to claim 1, wherein: The detection limit of the isonicotinic acid-barbituric acid spectrophotometry for cyanate is 0.005-0.5 mg / L, and the detection limit for thiocyanate is 0.01-1 mg / L; The detection limit of the thiocyanate by the ferric nitrate spectrophotometry is 0.2-20 mg / L.

10. The method according to claim 1, wherein: The measurement error of the method is less than 5.5%.

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