Pretreatment method for determining silicon content in uranium-containing nitric acid slurry system

Abstract

The invention discloses a method for measuring the silicon content in a uranium-containing nitric acid slurry system. The method comprises the following steps: (a) drawing a standard curve; (b) pretreating a sample; (c) measuring the silicon content. The method comprises the following steps: converting non-active silicon into active silicon by utilizing hydrofluoric acid; cost is low, application range is wide, and sensitivity is high; the problem of measuring the silicon content in the uranium-containing nitric acid slurry system is solved, and the method has guiding significance for technically solving the blockage of the reboiler.

Description

Technical Field

[0001] The invention relates to the technical field of silicon content determination, and specifically to a pre-treatment method for determining silicon content in a uranium-containing nitric acid slurry system. Background Art

[0002] During the operation of the nitric acid distillation system, the uranium-containing nitric acid slurry system has experienced nitrate crystal precipitation and excessive concentration multiples. The uranium-containing nitric acid slurry system is sludge-like and blocks the reboiler tubes. In order to explore methods to avoid the uranium-containing nitric acid slurry system from being viscous or nitrate precipitation, the continuous use cycle of the equipment can be extended. It is now necessary to study the influence of the component content in the uranium-containing nitric acid slurry system on its state (such as fluidity). According to operating experience, it is found that the Si content in the uranium ore concentrate raw material is positively correlated with the amount of nitric acid insoluble substances in the waste liquid (raffinate water and uranium-containing nitric acid slurry system). The main manifestation is that when the Si content is greater than 0.01%, the reboiler is easy to be blocked, the viscosity of the uranium-containing nitric acid slurry system increases, and the evaporation capacity of the distillation tower decreases. It is inferred that the silicon content in the uranium-containing nitric acid slurry system is directly related to the blockage of the reboiler. It is now necessary to establish a detection method for the silicon content in the uranium-containing nitric acid slurry system, specifically a pretreatment method for the determination of the silicon content in the uranium-containing nitric acid slurry system.

[0003] The silicon in the uranium-containing nitric acid slurry system exists in the form of dissolved silicates and a small amount of free silicon dioxide. There are many methods for determining the silicon content, including gravimetric method, hydrochloric acid evaporation and dehydration method, titration method and spectrophotometry. The gravimetric method, hydrochloric acid evaporation and dehydration method, and titration method are cumbersome, time-consuming, and have a long cycle. They are suitable for water samples with high silicon content (≥20mg / L). When the silicon content is below 2%, it is advisable to use spectrophotometry, which is divided into two types: silicon molybdenum yellow and silicon molybdenum blue spectrophotometry. Because the silicon molybdenum blue method has a lower detection limit and higher sensitivity, in general analysis, the silicon molybdenum blue spectrophotometry is used for the determination of small amounts of silicon.

[0004] The silicon content is determined by using silicomolybdic acid formed by silicate to oxidize luminol to produce chemiluminescence. The patent number is CN1090045A. The detection limit of the above method is 2.5μg / L SiO2. It is suitable for the silicon content in steam, water and metal. The measurement result is the active silicon content.

[0005] The silicate radical is used to catalyze the oxidation of iodine ions by ammonium molybdate to produce free iodine, and the produced elemental iodine is used to oxidize luminol to produce chemiluminescence analysis of the silicon content in the sample. This method requires a longer analysis time and is difficult to meet the requirements of random sampling analysis in industrial chemical analysis.

[0006] This method uses hydrofluoric acid to convert insoluble silicon dioxide into fluorosilicic acid, then adds aluminum chloride solution to mask the excess hydrofluoric acid and dissociate all the fluorosilicic acid to make silicon become soluble silicon dioxide, and uses the silicon molybdenum yellow method and the silicon molybdenum blue method for determination to obtain the total silicon content. Summary of the invention

[0007] The purpose of the present invention is to provide a pretreatment method for measuring the silicon content in a uranium-containing nitric acid slurry system, which uses hydrofluoric acid to convert inactive silicon into hydrosilicic acid, and adds aluminum chloride to mask the remaining hydrofluoric acid and dissociate the hydrosilicic acid. The method achieves accurate measurement of the total silicon content in the uranium-containing nitric acid slurry system, which has guiding significance for solving the process of reboiler blockage.

[0008] The technical solution of the present invention is as follows: A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system comprises the following steps;

[0009] (a) Drawing of standard curve;

[0010] (b) sample pretreatment;

[0011] Take uranium-containing nitric acid slurry, adjust the pH to 6-8 with NaOH solution, and then filter it; add polyacrylamide to the filtered aqueous solution to obtain a water sample to be tested;

[0012] (c) Determination of silicon content;

[0013] Pipette 10-50mL of treated water sample into a polyethylene bottle, add pure water to 50.0mL; add hydrochloric acid solution and shake well, add hydrofluoric acid solution and shake well, and heat;

[0014] Cool the heated water sample to room temperature, then add aluminum chloride; add 1-3 ml of 10% ammonium molybdate aqueous solution; add 10% oxalic acid solution, and then add 1-3 ml of reducing agent;

[0015] The absorbance was measured on a spectrophotometer to determine the total silicon content in the water sample.

[0016] In the step (a), 0 mL, 0.5 mL, 1.0 mL, 1.5 mL, 2.0 mL, and 2.5 mL of a 100 μg / mL silica standard solution are respectively pipetted into a group of polyethylene bottles, and pure water is added to dilute to 100 mL, at which time the silica concentrations are 0 ug / mL, 0.5 ug / mL, 1.0 ug / mL, 1.5 ug / mL, 2.0, and 2.5 ug / mL; 3.0 mL of aluminum chloride is added respectively, shaken, and then 1.0 mL of hydrofluoric acid solution is added, and allowed to stand for 5 min; then 1.0 mL of hydrochloric acid solution is added, shaken, and then 2.0 mL of 10% ammonium molybdate solution is added, and allowed to stand for 5 min, then 2.0 mL of 10% oxalic acid solution is added, shaken, and allowed to stand for 1 min, and then 2.0 mL of a reducing agent is added, and allowed to stand for 10 min. On a spectrophotometer, 440 nm, 20 mm cuvette is used, and the absorbance is measured with pure water as a reference, and a standard curve is drawn according to the measured absorbance.

[0017] In the step (b), the pH is adjusted to 7 using NaOH solution.

[0018] In the step (b), 100 mL of uranium-containing nitric acid slurry is taken, the pH is adjusted to 6-8 with a NaOH solution, and then the slurry is filtered; 100 mL of the filtered aqueous solution is taken, 0.5 g of cationic polyacrylamide and 0.5 g of anionic polyacrylamide are added, the solution is shaken for 5 seconds, allowed to stand for 20 minutes, and then filtered again to obtain a water sample to be tested.

[0019] In the step (c), 25 mL of the treated water sample was injected into a polyethylene bottle, and pure water was added to 50.0 mL; 1.0 mL of hydrochloric acid solution was added, and the mixture was shaken well; 1.0 mL of hydrofluoric acid solution was added, and the mixture was shaken well; the mixture was placed in a boiling water bath and heated for 15 minutes. A blank test was used for comparison.

[0020] In the step (c), the heated water sample is cooled to room temperature, and then 3.0 mL of aluminum chloride is added; 2 mL of 10% ammonium molybdate aqueous solution is added, shaken and allowed to stand, 2 mL of 10% oxalic acid solution is added, shaken and allowed to stand, and then 2 mL of reducing agent is added, shaken and allowed to stand.

[0021] In the step (c), 2 ml of 10% ammonium molybdate aqueous solution is added, shaken and allowed to stand for 5 min, and then 2 ml of reducing agent is added, shaken and allowed to stand for 5 min.

[0022] In the step (c), the absorbance is measured on a spectrophotometer using a wavelength of 440 nm and a 20 mm cuvette with pure water as a reference.

[0023] When calculating the result, the formula

[0024] c=m*p…………………………(1)

[0025] Where:

[0026] c——Silicon content concentration of uranium-containing nitric acid slurry system, unit: μg / mL;

[0027] m——concentration obtained from the standard curve, unit: μg / mL;

[0028] p——dilution multiple.

[0029] The reducing agent is 1-amino-2-naphthol-4-sulfonic acid.

[0030] The remarkable effects of the present invention are:

[0031] 1) This method uses hydrofluoric acid to convert inactive silicon into active silicon;

[0032] 2) The analytical method has low cost, wide application range and high sensitivity;

[0033] 3) This method solves the problem of determining the silicon content in the uranium-containing nitric acid slurry system, and has guiding significance for solving the reboiler blockage process. DETAILED DESCRIPTION

[0034] Many specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application, so the present application is not limited by the specific implementation disclosed below.

[0035] The terms used in one or more embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit one or more embodiments of the present application. The singular forms of "a", "said" and "the" used in one or more embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in one or more embodiments of the present application refers to and includes any or all possible combinations of one or more associated listed items.

[0036] It should be understood that, although the terms first, second, etc. may be used to describe various information in one or more embodiments of the present application, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0037] 1) Choice of technical route

[0038] When the silicon content is below 2%, it is advisable to use spectrophotometry, because the detection limit of the molybdenum blue method is lower and the sensitivity is higher. In general analysis, the molybdenum blue spectrophotometry is used for the determination of small amounts of silicon. The total silicon in water includes soluble silicates and a small amount of insoluble silicon dioxide. The chemical properties of insoluble silicon dioxide are very inactive, and hydrofluoric acid is the only good acid to dissolve it. Use hydrofluoric acid to convert insoluble silicon dioxide into fluorosilicic acid, then add aluminum chloride solution to mask the excess hydrofluoric acid, and dissociate all the fluorosilicic acid, so that silicon becomes soluble silicon dioxide. The total silicon content can be obtained by measuring it using the molybdenum blue method.

[0039] 2) Measurement

[0040] A method for determining silicon content in a uranium-containing nitric acid slurry system comprises the following steps:

[0041] (a) Drawing of standard curve

[0042] 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 mL of silica standard solution (100 μg / mL intermediate stock solution obtained by diluting GSB 04-1752-2004 (b), 1000 μg / mL standard solution) were respectively transferred into a group of polyethylene bottles, and diluted to 100 mL with pure water using a burette. The silica concentrations were 0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 μg / mL, respectively. 3.0 mL of aluminum chloride was added, shaken well, and 1.0 mL of hydrofluoric acid solution was accurately added with a plastic pipette, and allowed to stand for 5 min. 1.0 mL of hydrochloric acid solution was added, shaken well, 2.0 mL of 10% ammonium molybdate solution was added, allowed to stand for 5 min, 2.0 mL of 10% oxalic acid solution was added, shaken well, allowed to stand for 1 min, and 2.0 mL of 1-amino-2-naphthol-4-sulfonic acid reducing agent was added, the molecular formula of which is H2NC 10 H5(OH)SO3H, let stand for 10 minutes. Measure the absorbance on a spectrophotometer at 440nm, 20mm cuvette, and pure water as a reference, and draw a standard curve based on the measured absorbance.

[0043] (b) Sample pretreatment

[0044] Adjusting pH: taking 100 mL of uranium-containing nitric acid slurry, adjusting the pH with NaOH solution. In different embodiments, the pH was adjusted to pH=6, pH=7, and pH=8, respectively, and then filtering was performed.

[0045] Take 100 mL of the filtered aqueous solution, add 0.5 g of cationic polyacrylamide and 0.5 g of anionic polyacrylamide to remove interference from suspended particles, organic matter, etc. in the aqueous solution, shake for 5 seconds, let it stand for 20 minutes, and then filter it again to obtain the water sample to be tested.

[0046] (c) Determination of silicon content

[0047] The treated water sample was injected into a polyethylene bottle. In different embodiments, 10 mL, 25 mL, and 50 mL of the treated water sample were injected into the polyethylene bottle, and pure water was added to 50.0 mL using a burette. 1.0 mL of hydrochloric acid solution was added, shaken well, 1.0 mL of hydrofluoric acid solution was accurately added using a pipette, shaken well, the bottle cap was tightly closed, and the bottle was placed in a boiling water bath and heated for 15 minutes. A blank test was used for comparison.

[0048] Place the heated water sample in cold water to cool until the water temperature in the bottle reaches room temperature, then add 3.0 mL of aluminum chloride, shake well, and let stand for 5 minutes.

[0049] Add 10% ammonium molybdate aqueous solution. In different embodiments, 1 ml, 2 ml, and 3 ml of 10% ammonium molybdate aqueous solution are added respectively, shaken and placed. In different embodiments, shaken and placed for 3 min, 5 min, and 7 min respectively; add 2 mL of 10% oxalic acid solution, shaken and placed for 1 min, and then add 1-amino-2-naphthol-4-sulfonic acid reducing agent. In different embodiments, 1 mL, 2 mL, and 3 mL of reducing agent are added respectively, shaken and placed; in different embodiments, placed for 3 min, 5 min, and 7 min respectively.

[0050] Use a 440nm wavelength and a 20mm cuvette on a spectrophotometer, and use pure water as a reference to measure the absorbance. Multiply the value obtained from the standard curve by the dilution factor (adjusting the pH value is the first dilution, and determining the silicon content and removing the treated water sample is the second dilution), which is the total silicon content (μg / mL) in the water sample.

[0051] 3) Result calculation

[0052] c=m*p……………………(1)

[0053] Where:

[0054] c——Silicon content concentration of uranium-containing nitric acid slurry system (μg / mL);

[0055] m——concentration obtained from the standard curve (μg / mL);

[0056] p——dilution multiple.

[0057] The above description is only a preferred embodiment of this patent and is not intended to limit this patent. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this patent should be included in the scope of protection of this patent.

[0058] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0059] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0060] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The optional embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can understand and use the present application well.

Claims

1. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system, characterized in that: The steps include: (a) Drawing of standard curve; (b) sample pretreatment; Take uranium-containing nitric acid slurry, adjust the pH to 6-8 with NaOH solution, and then filter it; add polyacrylamide to the filtered aqueous solution to obtain a water sample to be tested; (c) Determination of silicon content; Pipette 10-50mL of treated water sample into a polyethylene bottle, add pure water to 50.0mL; add hydrochloric acid solution and shake well, add hydrofluoric acid solution and shake well, and heat; Cool the heated water sample to room temperature, then add aluminum chloride; add 1-3 ml of 10% ammonium molybdate aqueous solution; add 10% oxalic acid solution, and then add 1-3 ml of reducing agent; The absorbance was measured on a spectrophotometer to determine the total silicon content in the water sample.

2. The pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 1, characterized in that: In the step (a), 0 mL, 0.5 mL, 1.0 mL, 1.5 mL, 2.0 mL, and 2.5 mL of a 100 μg / mL silica standard solution are respectively pipetted into a group of polyethylene bottles, and pure water is added to dilute to 100 mL, at which time the silica concentrations are 0 ug / mL, 0.5 ug / mL, 1.0 ug / mL, 1.5 ug / mL, 2.0, and 2.5 ug / mL; 3.0 mL of aluminum chloride is added respectively, shaken, and then 1.0 mL of hydrofluoric acid solution is added, and allowed to stand for 5 min; then 1.0 mL of hydrochloric acid solution is added, shaken, and then 2.0 mL of 10% ammonium molybdate solution is added, and allowed to stand for 5 min, then 2.0 mL of 10% oxalic acid solution is added, shaken, and allowed to stand for 1 min, and then 2.0 mL of a reducing agent is added, and allowed to stand for 10 min. On a spectrophotometer, 440 nm, 20 mm cuvette is used, and the absorbance is measured with pure water as a reference, and a standard curve is drawn according to the measured absorbance.

3. The pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 1, characterized in that: In the step (b), the pH is adjusted to 7 using NaOH solution.

4. The pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 1, characterized in that: In the step (b), 100 mL of uranium-containing nitric acid slurry is taken, the pH is adjusted to 6-8 with a NaOH solution, and then the slurry is filtered; 100 mL of the filtered aqueous solution is taken, 0.5 g of cationic polyacrylamide and 0.5 g of anionic polyacrylamide are added, the solution is shaken for 5 seconds, allowed to stand for 20 minutes, and then filtered again to obtain a water sample to be tested.

5. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 4, characterized in that: In the step (c), 25 mL of the treated water sample was injected into a polyethylene bottle, and pure water was added to 50.0 mL; 1.0 mL of hydrochloric acid solution was added, and the mixture was shaken well; 1.0 mL of hydrofluoric acid solution was added, and the mixture was shaken well; the mixture was placed in a boiling water bath and heated for 15 minutes. A blank test was used for comparison.

6. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 4, characterized in that: In the step (c), the heated water sample is cooled to room temperature, and then 3.0 mL of aluminum chloride is added; 2 mL of 10% ammonium molybdate aqueous solution is added, shaken and allowed to stand, 2 mL of 10% oxalic acid solution is added, shaken and allowed to stand, and then 2 mL of reducing agent is added, shaken and allowed to stand.

7. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 6, characterized in that: In the step (c), 2 ml of 10% ammonium molybdate aqueous solution is added, shaken and allowed to stand for 5 min, and then 2 ml of reducing agent is added, shaken and allowed to stand for 5 min.

8. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 4, characterized in that: In the step (c), the absorbance is measured on a spectrophotometer using a wavelength of 440 nm and a 20 mm cuvette with pure water as a reference.

9. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 8, characterized in that: When calculating the result, the formula c=m*p............(1) Where: c——Silicon content concentration of uranium-containing nitric acid slurry system, unit: μg / mL; m——concentration obtained from the standard curve, unit: μg / mL; p——dilution multiple.

10. A pretreatment method for determining silicon content in a uranium-containing nitric acid slurry system according to claim 2 or 7, characterized in that: The reducing agent is 1-amino-2-naphthol-4-sulfonic acid.