Determination method of octadecylamine in potassium fertilizer flotation slurry

Abstract

The present invention discloses a method for determining octadecylamine in potash flotation slurry and its application. The determination method includes the following steps: Step 1, prepare a determination system; Step 2, determination of salt concentration in the liquid phase: use nitrate titration method to determine the chlorine content in the slurry liquid phase, and convert it into the equivalent concentration of potassium chloride; Step 3, draw a standard curve; Step 4, treatment of flotation slurry samples: add an antifoaming agent to the flotation slurry. After the bubbles are eliminated and the solid phase is deposited, the solid-liquid two phases are centrifuged to separate, and the obtained liquid phase is the slurry liquid phase, and the obtained solid phase is freeze-dried to obtain a solid phase sample; Step 5, determination of the octadecylamine content in the slurry liquid phase and the solid phase sample. The present invention can accurately determine the content of octadecylamine in the flotation slurry and clarify its distribution situation.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical detection, and particularly relates to a method for determining octadecylamine in a potassium fertilizer flotation slurry and its application. Background Art

[0002] When producing potassium chloride by the cold crystallization - positive flotation method, octadecylamine is usually used as a flotation collector and added into the pulp in the pulp - adjusting process for the flotation separation of potassium chloride. In this process, octadecylamine is distributed between the solid - liquid two - phases in the slurry. The analysis of the distribution of octadecylamine in the slurry can provide basic data for the evaluation, optimization of the flotation process and intelligent production control.

[0003] In the current potassium fertilizer production process, there is a situation where the yield of potassium chloride fluctuates greatly due to fluctuations in the ore source composition and the sun - drying conditions of carnallite ore. Usually, the way of changing the dosage of the flotation agent is adopted to ensure that the potassium chloride yield meets the standard. During this period, the adjustment of the flotation agent dosage is mainly based on actual operation experience without exact theoretical basis, and the content of octadecylamine in the slurry, its distribution in the solid - liquid phases, and the influence of the octadecylamine content on the potassium chloride yield are all unclear. Therefore, timely and accurately detecting the content and distribution of octadecylamine in the slurry can provide basic data for the evaluation, optimization of the flotation process and intelligent production control. The methods for determining the content of octadecylamine in solution include gas chromatography, liquid chromatography, and spectrophotometry. Among them, the spectrophotometry has simple instruments and convenient operation, and is suitable for on - site detection in production.

[0004] Hu Jiayuan et al. (CN102062728B) provided a method for determining the concentration of octadecylamine without adding a chromogenic agent. Glacial acetic acid is added to the solution to be measured, and the absorbance in the ultraviolet region is directly measured, which can effectively measure octadecylamine in the content range of 10 - 50mg / L. Octadecylamine has low solubility in water, and due to the salting - out effect, its solubility in high - concentration potassium chloride is even smaller. This method is not suitable for determining the content of low - content octadecylamine.

[0005] Evtushenko et al. used methyl orange as a chromogenic agent at pH = 2.5 to directly measure the absorbance value to obtain the concentration of octadecylamine in water. Sun Deshun et al. first added salicylaldehyde to react with octadecylamine to form salicylaldimine, and then added bromocresol green for color development to measure the absorbance value to obtain the octadecylamine content. For the above two methods without using an extractant, chromogenic agents are added. Since the chromogenic agent itself has absorbance, an excessive amount is usually added and not accurately quantified during the measurement, which is likely to cause background interference to the absorbance measurement of the complex, resulting in a decrease in the measurement precision, especially for low - content samples, the measurement error is large.

[0006] Ronald M. Silverstein used methyl orange as the chromogenic reagent and chloroform, dichloroethane, and diethyl ether as the extractants to determine the amine content in boiler system water. The Chinese electric power industry standard "Determination of Alkyl Octadecylamine in Water" (DL / T 1042. 2007) also recommends using methyl orange as the complexing chromogenic reagent. At pH = 3 - 4, chloroform extraction and spectrophotometry are used to determine the octadecylamine in power plant boiler wastewater.

[0007] When determining the octadecylamine in potassium fertilizer flotation reagents, Liang Huibin used gas chromatography and auramine - 2 spectrophotometry respectively to determine the content of octadecylamine hydrochloride in saturated potassium chloride solution. When using gas chromatography, after chloroform extraction, solvent evaporation and concentration are required. The determination process is cumbersome and chloroform volatilization causes air pollution; when using auramine - 2 spectrophotometry, the detection limit of the determination is low, which is suitable for the determination of the content of octadecylamine hydrochloride in pure potassium chloride solution. In the actual potassium chloride system, magnesium and calcium ions are often contained, and auramine - 2 will form precipitates with magnesium and calcium ions in the solution, affecting its complexation and color development with octadecylamine, resulting in inaccurate determination and being not applicable to the actual system.

[0008] Diao Xiangrui et al. used bromocresol green spectrophotometry to determine the octadecylamine content in potassium chloride. When drawing the standard curve, the amount of chromogenic reagent added to different - concentration octadecylamine solutions is different, and the ratio of the organic phase to the aqueous phase is not fixed during the chloroform extraction step. If this method is used to determine unknown samples, the amount of chromogenic reagent used cannot be determined, and the influence on the extraction efficiency and the entire analysis process cannot be determined either, so the accuracy cannot be guaranteed when determining actual samples. Since octadecylamine is highly soluble in chloroform, the above - mentioned methods all use chloroform as the extractant. However, chloroform is highly volatile and has the possibility of being carcinogenic, is sensitive to light, can decompose into highly toxic phosgene, and is controlled by dangerous chemicals and precursor chemicals.

[0009] Li Bing used methyl orange as the chromogenic reagent and ethyl acetate instead of chloroform as the extractant to determine the octadecylamine content in water. Ethyl acetate has lower toxicity, but ethyl acetate has a certain solubility in water (0.1 mL / mL) and will undergo a certain degree of hydrolysis. When used to extract the methyl orange - octadecylamine complex, the recovery rate may not be high and the determination result may be on the low side.

[0010] When using spectrophotometry to determine low-content octadecylamine at present, chloroform is mainly used as the extractant. Chloroform is extremely volatile and will quickly volatilize in each step of the determination operation, resulting in affected determination accuracy and low determination precision. In addition, chloroform has the possibility of causing cancer, is sensitive to light, can be decomposed into highly toxic phosgene, posing a health threat to the determination experimenters. Moreover, chloroform is under the control of dangerous chemicals and precursor chemicals, and there are strict requirements for its purchase, use, and storage. When using ethyl acetate instead of chloroform as the extractant, the toxicity of ethyl acetate is relatively low, but ethyl acetate has a certain solubility in water (0.1 mL / mL). When used to extract the methyl orange octadecylamine complex, the recovery rate may not be high and the determination result may be on the low side.

[0011] When using bromocresol green as the indicator, since bromocresol green has a small solubility in water, ethanol is usually used for dissolution and preparation. The present invention uses a water-soluble indicator as the color-developing agent and uses distilled water for dissolution and preparation, avoiding the introduction of ethanol into the determination system, reducing the solubility of the octadecylamine complex in the aqueous phase, and further improving the accuracy of the determination method.

[0012] In the flotation slurry, there are three phases: solid-liquid-foam. The presence of solid-containing foam suspended on the surface of the slurry will lead to inaccurate analytical measurements. Summary of the Invention

[0013] The purpose of the present invention is to address the technical defects existing in the prior art. The present invention provides a method for determining octadecylamine in a potassium fertilizer flotation slurry, using a water-soluble indicator as the color-developing agent and long-chain alkane for extraction and color development.

[0014] Another aspect of the present invention is to provide the application of the method for determining octadecylamine in the potassium fertilizer flotation slurry.

[0015] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0016] A method for determining octadecylamine in a potassium fertilizer flotation slurry, the flotation slurry includes a solid phase, a liquid phase, and solid-containing foam, and includes the following steps:

[0017] Prepare a measurement system, which includes an independent potassium chloride standard (preferably of analytical reagent grade), a water-soluble indicator, a buffer solution, and an octadecylamine standard stock solution. Among them, weigh the water-soluble indicator and make up the volume with distilled water to obtain a water-soluble indicator solution; the octadecylamine standard stock solution includes multiple octadecylamine standard solutions with different concentrations, and the concentrations of the multiple octadecylamine standard solutions change in a gradient. It is prepared by the following steps: accurately weigh a predetermined mass of octadecylamine, dissolve it in a long-chain alkane and make up the volume, and then dilute it respectively to obtain octadecylamine standard solutions with different concentrations; the pH of the buffer solution is 4.5 - 6.0; in the measurement system, the volume ratio of the organic phase (each octadecylamine standard solution) to the aqueous phase (including the water-soluble indicator solution and the buffer solution) is (0.05 - 9):1

[0018] Determination of the salt concentration in the liquid phase: The chloride content in the slurry liquid phase is determined by nitrate titration and converted to the equivalent concentration of potassium chloride;

[0019] Draw a standard curve:

[0020] Step a, accurately weigh pure potassium chloride, accurately measure a predetermined volume of the buffer solution, the water-soluble indicator solution, and distilled water and add them to the pure potassium chloride. After complete dissolution, the concentration of the potassium chloride aqueous phase is the same as the equivalent concentration of the potassium chloride. Then, add the octadecylamine standard solution according to the volume ratio of the organic phase to the aqueous phase of (0.05 - 9):1; fully react and extract. After standing and separating layers, using the long-chain alkane as the blank, adopt a quartz cuvette to perform an absorption spectrum scan on the organic phase layer in the wavelength range of 800 - 200 nm, select the measurement wavelength. Preferably, the wavelength corresponding to the peak value of the absorbance is the measurement wavelength. More preferably, first select the wavelength corresponding to the maximum absorbance as the measurement wavelength and perform steps 1.2 - 1.3. If the obtained standard curve is linear, use this measurement wavelength. If the obtained standard curve is not linear, then select other wavelengths corresponding to the peaks to perform steps 1.2 - 1.3 until the standard curve is linear;

[0021] Step b, accurately weigh the same mass of pure potassium chloride as in step a, accurately measure the same volume of the buffer solution, the water-soluble indicator solution, and distilled water as in step a and add them to the pure potassium chloride. Then, according to the same volume ratio of the organic phase to the aqueous phase as in step a, successively add octadecylamine standard solutions with gradient concentrations, preferably octadecylamine standard solutions of equal volume. Fully react and extract. After standing and separating layers, using the long-chain alkane as the blank, adopt a quartz cuvette to measure the absorbance of the organic phase layer at the selected measurement wavelength;

[0022] Step c, use the concentration of each octadecylamine standard solution as the abscissa and the absorbance obtained in step b corresponding to it as the ordinate to draw a standard curve;

[0023] Flotation slurry sample processing: add defoaming agent to the flotation slurry to eliminate bubbles and solid phase sedimentation, then centrifuge to separate the solid and liquid phases. The obtained liquid phase is the slurry liquid phase, and the obtained solid phase is freeze-dried to obtain a solid phase sample;

[0024] Determination of the content of octadecylamine in the slurry liquid phase: accurately measure the slurry liquid phase, the mass of the salt in the slurry liquid phase (the mass of the salt is the mass of potassium chloride calculated based on the equivalent concentration of potassium chloride) is the same as the mass of pure potassium chloride in step a, accurately measure the same volume of buffer solution, water-soluble indicator solution, and distilled water as in step a, and fully dissolve them. Then, add a long-chain alkane according to the same volume ratio of the organic phase to the aqueous phase as in step a; fully react and extract, let it stand and separate, and then use a long-chain alkane and a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the slurry liquid phase by using a standard curve;

[0025] Determination of the content of octadecylamine in the solid phase sample: Accurately weigh the solid phase sample obtained in step 3, the mass of the solid phase sample is the same as the mass of pure potassium chloride in step a, and accurately measure the same volume of buffer solution, water-soluble indicator solution, and distilled water in step a in sequence and add them to the solid phase sample. After sufficient dissolution, add long-chain alkane according to the same volume ratio of organic phase to aqueous phase as in step a; after sufficient extraction and shaking, let it stand and separate the layers, use the long-chain alkane as a blank, use a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the solid phase sample using the standard curve.

[0026] In the above technical solution, the dissolving, coloring and extraction are all carried out in the same closed container.

[0027] In the above technical solution, the concentration range of the octadecylamine stock solution is 0.5 mg / L-100 mg / L.

[0028] In the above technical solution, the water-soluble indicator is a water-soluble indicator solution with a concentration of 0.1-20 g / L.

[0029] In the above technical solution, the buffer solution is an acetic acid-sodium acetate buffer solution, which is prepared by the following steps: weighing anhydrous sodium acetate and dissolving it in distilled water, adding acetic acid to adjust the pH of the solution to obtain an acetic acid-sodium acetate buffer solution with a pH of 4.5-6.0.

[0030] In the above technical solution, the water-soluble indicator is bromocresol green sodium salt, bromocresol green potassium salt, bromophenol blue sodium salt or bromophenol blue potassium salt.

[0031] In the above technical solution, the long chain alkane is C n H 2n+2 , n = 7-14. The water-soluble indicator is in excess relative to octadecylamine to allow complete color development.

[0032] In the above technical solution, the volume ratio of the acetic acid - sodium acetate buffer solution to the water - soluble indicator solution is (5 - 100):1.

[0033] In the above technical solution, it is characterized in that the defoaming agent is an organosilicon defoaming agent, and 0.1 - 20 mL of the defoaming agent is added to each liter of the slurry.

[0034] On the other hand of the present invention, an application of the method for determining octadecylamine in the potassium fertilizer flotation slurry in evaluating the dosage of flotation reagents.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. For determining the content of low - content substances in a complex system, the accuracy of the determination method determines the quality of the determination method. The present invention uses long - chain alkanes as extraction agents, which have good solubility for octadecylamine and the octadecylamine complex of the chromogenic agent, are insoluble in water, will not cause loss of octadecylamine extraction, and have low volatility and low toxicity, high determination accuracy, and little harm to the human body and the environment; ethanol is not introduced, and it will not cause loss of the octadecylamine complex of the chromogenic agent in water.

[0037] 2. During the determination process of the present invention and when drawing the standard curve, the potassium chloride sample is directly added to the colorimetric determination system, avoiding the loss of octadecylamine due to hydrophobic adsorption on the container wall during the sample dissolution process. At the same time, when using this determination system, the dissolution, color development, and extraction are all carried out in the same closed container, further improving the accuracy of the octadecylamine content determination.

[0038] 3. The present invention selects a liquid long - chain alkane with low volatility and low toxicity and a carbon chain length as close as possible to that of octadecylamine. The better the similarity solubility with octadecylamine, the better the extraction color development property, sensitivity, and accuracy.

[0039] 4. The chromogenic agent molecules and octadecylamine molecules complex to form macromolecules, which are extracted into the organic phase for color development by the "similar - solubility" principle. The chromogenic agent itself cannot be extracted due to insufficient hydrophobicity. Due to the salting - out effect, the salt concentration in the solution will promote the complexation of chromogenic agent molecules and octadecylamine molecules to form macromolecules for extraction. The higher the potassium chloride concentration, the greater the absorbance, and the higher the determination sensitivity.

[0040] 5. During the determination process of the present invention, a defoaming agent is added to the determination system to remove bubbles, so that the solid phase suspended on the liquid surface due to the presence of bubbles is deposited, but it does not affect the adsorption of octadecylamine on the solid phase; the solid - liquid two - phase is separated by centrifugation, and the solid phase is freeze - dried, avoiding partial volatilization loss of octadecylamine adsorbed on the solid phase during the high - temperature drying process. Then, the octadecylamine content in the solid and liquid phases is measured respectively, and the content of octadecylamine in the flotation slurry can be accurately measured, and its distribution can be clarified. Description of the Drawings

[0041] Figure 1 It is the spectral scanning curve of the sodium bromocresol green - heptane system in Example 1.

[0042] Figure 2 It is the standard curve for the determination of octadecylamine in the sodium bromocresol green - heptane system in Example 1.

[0043] Figure 3 It is the spectral scanning curve of the potassium bromocresol green - tetradecane system in Example 2.

[0044] Figure 4 It is the standard curve for the determination of octadecylamine in the potassium bromocresol green - tetradecane system in Example 2.

[0045] Figure 5 It is the spectral scanning curve of the sodium bromophenol blue - dodecane system in Example 3.

[0046] Figure 6 It is the standard curve for the determination of octadecylamine in the sodium bromophenol blue - dodecane system in Example 3. Detailed implementation manners

[0047] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Example 1

[0049] A method for determining octadecylamine in a potassium fertilizer flotation slurry includes the following steps:

[0050] (1) Solution preparation: Weigh sodium bromocresol green and dissolve it in distilled water, then make up the volume to a volumetric flask to prepare a sodium bromocresol green solution with a concentration of 20 g / L; weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to prepare an acetic acid - sodium acetate buffer solution with pH = 6.0; accurately weigh 0.5000 g of octadecylamine, dissolve it in C7H 16 and make up the volume to 1 L in a volumetric flask, and obtain an octadecylamine standard stock solution with a concentration gradient through dilution, with concentrations of 4, 8, 16, 24, 32, and 40 mg / L respectively.

[0051] (2) Determination of the salt concentration in the liquid phase of the slurry: Use the mercuric nitrate titration method to determine the chlorine content in the liquid phase of the slurry, and convert it to the equivalent concentration of potassium chloride as 300 g / L.

[0052] (3) Standard curve drawing:

[0053] Step 3.1, accurately weigh 29.9997 g of potassium chloride of guaranteed reagent grade and add it to a volumetric flask. Then, accurately measure 75.00 mL of acetic acid - sodium acetate buffer solution, 0.75 mL of water-soluble indicator solution, and 24.25 mL of distilled water in sequence and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1. After shaking and dissolving, make the concentration of potassium chloride in the aqueous solution 300 g / L.

[0054] According to the volume ratio of the organic phase to the aqueous phase of 0.05:1, add 5.00 mL of a standard stock solution of octadecylamine with a concentration of 16 mg / L; cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for layering. Using C7H 16 as the blank, use a quartz cuvette to perform an absorption spectrum scan on the organic phase layer in the wavelength range of 800 - 200 nm, and select the measurement wavelength as 624 nm;

[0055] Step 3.2, using the same method as in Step 3.1, add 5.00 mL of standard stock solutions of octadecylamine with concentrations of 4, 8, 16, 24, 32, and 40 mg / L respectively, measure the absorbance at 624 nm, and plot the standard curve as shown in the figure.

[0056] (4) Treatment of slurry sample: According to 20 mL / L of slurry, add an organosilicon defoamer to the slurry. After the bubbles are eliminated and the solid phase is deposited, centrifuge to separate the solid and liquid phases. The solid phase is freeze-dried for later use.

[0057] (5) Determination of octadecylamine content: Using the same conditions as in step (3):

[0058] ①Accurately measure the liquid phase solution, buffer solution, and water-soluble indicator solution in step (2) and add them to a volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1; according to the volume ratio of the organic phase to the aqueous phase of 0.05:1, add C7H 16 ; cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for layering. Using C7H 16 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the content of octadecylamine in the liquid phase as 0.394 mg / L through the standard curve.

[0059] ②Accurately weigh the solid phase sample in step (4) and add it to a volumetric flask. Then, accurately measure the buffer solution, water-soluble indicator solution, and distilled water in sequence and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 100:1; after shaking and dissolving, make the concentration of potassium chloride in the aqueous solution 300 g / L. According to the volume ratio of the organic phase to the aqueous phase of 0.05:1, add C7H 16 ; cover the volumetric flask and shake it well. After sufficient reaction and extraction, let it stand for layering. Using C7H 16The absorbance of the organic phase was measured using a quartz cuvette as a blank, and the content of octadecylamine in the solid phase was calculated to be 6.27 mg / kg using the standard curve.

[0060] The content of flotation reagent in both solid and liquid phases is relatively low, resulting in less foaming, and the amount of reagent added needs to be increased.

[0061] Example 2

[0062] A method for determining octadecylamine in potash fertilizer flotation slurry comprises the following steps:

[0063] (1) Solution preparation: Weigh bromocresol green potassium salt, dissolve it in distilled water and dilute it to a volumetric flask to prepare a 0.1 g / L bromocresol green potassium salt solution; weigh anhydrous sodium acetate, dissolve it in distilled water, add acetic acid to adjust the pH of the solution, and prepare an acetic acid-sodium acetate buffer solution with a pH of 4.5; accurately weigh 0.2000 g of octadecylamine, dissolve it in C 14 H 30 The solution was diluted to 500 mL in a volumetric flask and diluted to obtain a standard stock solution of octadecylamine with gradient concentrations.

[0064] (2) Determination of salt concentration in the slurry liquid phase: The chlorine content in the slurry liquid phase was determined by mercury nitrate titration, and the equivalent concentration converted to potassium chloride was 303 g / L.

[0065] (3) Drawing of standard curve: Step 3.1, accurately weigh 3.0283 g of high-grade pure potassium chloride and add it to a volumetric flask. Accurately weigh 5.00 mL of buffer solution, 1.00 mL of water-soluble indicator solution, and 4.00 mL of distilled water and add them to the volumetric flask in sequence. The volume ratio of buffer solution to water-soluble indicator solution is 5:1. After shaking and dissolving, the potassium chloride concentration is 303 g / L.

[0066] According to the volume ratio of organic phase to aqueous phase of 9:1, add 90.00mL of 32mg / L octadecylamine standard stock solution; cover the volumetric flask and shake it evenly. After sufficient reaction and extraction, let it stand and separate the layers. 14 H 30 As blank, a quartz cuvette was used to scan the absorption spectrum of the organic phase layer from 800 to 200 nm, and the measurement wavelength was selected as 394 nm;

[0067] In step 3.2, use the same method as step 3.1 to add 90.00 mL of octadecylamine standard stock solution with concentrations of 8, 16, 32, 64, 80, and 96 mg / L, respectively. Measure the absorbance at 394 nm and draw a standard curve.

[0068] (4) Slurry sample treatment: Add silicone defoaming agent to the slurry at a concentration of 1 mL / L. After the bubbles are eliminated and the solid phase is deposited, centrifuge to separate the solid and liquid phases. The solid phase is freeze-dried and set aside for use.

[0069] (5) Determination of octadecylamine content: The same conditions as in step (3) are adopted:

[0070] ①Accurately measure the liquid phase solution, buffer solution, and water-soluble indicator solution in step (2) and add them to a volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 5:1; according to the volume ratio of the organic phase to the aqueous phase of 9:1, add C 14 H 30 ; After covering the volumetric flask and shaking it well, after fully reacting and extracting, let it stand for layering, and using C 14 H 30 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the liquid phase to be 15.85 mg / L through the standard curve;

[0071] ②Accurately weigh the solid phase sample in step (4) and add it to a volumetric flask. Then accurately measure the buffer solution, water-soluble indicator solution, and distilled water in sequence and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 5:1; after shaking and dissolving, make the potassium chloride concentration in the aqueous solution 303 g / L. According to the volume ratio of the organic phase to the aqueous phase of 9:1, add C 14 H 30 ; After covering the volumetric flask and shaking it well, after fully reacting and extracting, let it stand for layering, and using C 14 H 30 as the blank, use a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the solid phase to be 251.43 mg / kg through the standard curve.

[0072] The content of the flotation reagent in the solid and liquid phases is slightly high, and the amount of foam is moderate.

[0073] Example 3

[0074] (1) Solution preparation: Weigh sodium bromophenol blue and dissolve it in distilled water and make up the volume to a volumetric flask to prepare a sodium bromophenol blue solution with a concentration of 10 g / L; weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution, and prepare an acetic acid-sodium acetate buffer solution with pH = 5.0; accurately weigh 0.5000 g of octadecylamine and dissolve it in C 12 H 26 and make up the volume to 500 mL in a volumetric flask to prepare a standard stock solution of octadecylamine.

[0075] (2) Determination of the salt concentration in the slurry liquid phase: The mercury nitrate titration method is used to determine the chlorine content in the slurry liquid phase, and the equivalent concentration of potassium chloride is converted to 295 g / L.

[0076] (3) Drawing of standard curve: In step 3.1, accurately weigh 5.9011 g of high-grade pure potassium chloride and add it to a volumetric flask. Accurately weigh 12.00 mL of buffer solution, 0.50 mL of bromophenol blue sodium salt solution, and 7.50 mL of distilled water and add them to the volumetric flask in sequence. The volume ratio of buffer solution to water-soluble indicator solution is 24:1. After shaking and dissolving, the potassium chloride concentration is 295 g / L.

[0077] According to the volume ratio of organic phase to aqueous phase of 0.2:1, add 4.00 ml of 16 mg / L octadecylamine standard stock solution; cover the volumetric flask and shake it evenly. After sufficient reaction and extraction, let it stand and separate the layers. 12 H 26 As blank, a quartz cuvette was used to scan the absorption spectrum of the organic phase layer in the wavelength range of 800-200nm, and the measurement wavelength was selected as 568nm;

[0078] In step 3.2, use the same method as step 3.1 to add 4.00 mL of octadecylamine standard stock solution with concentrations of 2, 4, 8, 16, 20, and 24 mg / L, respectively, measure the absorbance, and draw a standard curve as shown in the figure.

[0079] (4) Slurry sample treatment: Add an organosilicon defoamer to the slurry at a concentration of 0.2 mL / L. After the bubbles are eliminated and the solid phase is deposited, centrifuge to separate the solid and liquid phases. The solid phase is freeze-dried and set aside for use.

[0080] (5) Determination of octadecylamine content: Use the same conditions as step (3):

[0081] ① Accurately measure the liquid phase solution, buffer solution, and water-soluble indicator solution in step (2) and add them to a volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 24:1. Add C 12 H 26 ; Cover the volumetric flask and shake it evenly. After sufficient reaction and extraction, let it stand for stratification and then use C 12 H 26 The absorbance of the organic phase was measured using the blank, and the content of octadecylamine in the liquid phase was calculated to be 1.26 mg / L using the standard curve.

[0082] ② Accurately weigh the solid phase sample in step (4) and add it to a volumetric flask. Accurately weigh the buffer solution, water-soluble indicator solution, and distilled water in sequence and add them to the volumetric flask. The volume ratio of the buffer solution to the water-soluble indicator solution is 24:1. After shaking and dissolving, the concentration of potassium chloride in the aqueous solution is 295g / L. Add C 12 H 26 ; Cover the volumetric flask and shake it evenly. After sufficient reaction and extraction, let it stand for stratification and then use C 12 H 26The absorbance of the organic phase was measured using the blank, and the content of octadecylamine in the solid phase was calculated to be 20.13 mg / kg using the standard curve.

[0083] The content of flotation reagent in the solid and liquid phases is moderate, and the amount of foaming is relatively small.

[0084] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining octadecylamine in a potassium fertilizer flotation slurry, characterized in that, The flotation slurry includes solid phase, liquid phase and solid-containing foam, and comprises the following steps: Prepare a determination system, which includes a potassium chloride standard, a water-soluble indicator, a buffer solution and an octadecylamine standard stock solution that are independent of each other. Among them, weigh the water-soluble indicator and make up the volume with distilled water to obtain a water-soluble indicator solution; the octadecylamine standard stock solution includes multiple octadecylamine standard solutions with different concentrations, and the concentrations of the multiple octadecylamine standard solutions vary in a gradient manner. It is prepared by the following steps: accurately weigh a predetermined mass of octadecylamine, dissolve it in a long-chain alkane and make up the volume, and then dilute it respectively to obtain octadecylamine standard solutions with different concentrations; the pH of the buffer solution is 4.5-6.0; Step 1, determination of salt concentration in the liquid phase: Use the nitrate titration method to determine the chlorine content in the liquid phase of the slurry, and convert it into the equivalent concentration of potassium chloride; Step 2, draw a standard curve: Step 2.1, accurately weigh pure potassium chloride, accurately measure a predetermined volume of buffer solution, water-soluble indicator solution and distilled water and add them to the pure potassium chloride. After fully dissolving, the concentration of potassium chloride in the aqueous phase is the same as the equivalent concentration of the potassium chloride. Then add the octadecylamine standard solution according to the volume ratio of the organic phase to the aqueous phase of (0.05-9):1; fully react and extract, after standing and separating layers, using the long-chain alkane as the blank, adopt a quartz cuvette to perform absorption spectrum scanning on the organic phase layer in the wavelength range of 800-200 nm, select the measurement wavelength, and the wavelength corresponding to the peak value of the absorbance is the measurement wavelength. First, select the wavelength corresponding to the maximum absorbance as the measurement wavelength and perform steps 2.2-2.

3. If the obtained standard curve is linear, use this measurement wavelength. If the obtained standard curve is not linear, then select other wavelengths corresponding to the peaks to perform steps 2.2-2.3 until the standard curve is linear; Step 2.2, accurately weigh the same mass of pure potassium chloride as in step a, accurately measure the same volume of buffer solution, water-soluble indicator solution and distilled water as in step 2.1 and add them to the pure potassium chloride, and then add the octadecylamine standard solutions with gradient concentrations in turn according to the same volume ratio of the organic phase to the aqueous phase as in step 2.1, which are octadecylamine standard solutions with equal volumes. Fully react and extract, after standing and separating layers, using the long-chain alkane as the blank, adopt a quartz cuvette to measure the absorbance of the organic phase layer at the selected measurement wavelength respectively; Step 2.3, use the concentration of each octadecylamine standard solution as the abscissa and the absorbance obtained in step 2.2 corresponding to it as the ordinate to draw a standard curve; Step 3, treatment of the flotation slurry sample: Add an antifoaming agent to the flotation slurry. After the bubbles are eliminated and the solid phase is deposited, centrifuge to separate the solid-liquid two phases. The obtained liquid phase is the liquid phase of the slurry, and the obtained solid phase is freeze-dried to obtain a solid phase sample; Step 4, determination of octadecylamine content in the slurry liquid phase: Accurately measure the slurry liquid phase. The mass of the salt in the slurry liquid phase is the same as the mass of pure potassium chloride in Step 2.

1. After accurately measuring the same volume of buffer solution, water-soluble indicator solution, and distilled water as in Step 2.1 and fully dissolving them, add long-chain alkane according to the same volume ratio of organic phase to water phase as in Step 2.1; react and extract fully, and after standing and separating layers, use a quartz cuvette with long-chain alkane to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the slurry liquid phase through the standard curve; Step 5, determination of octadecylamine content in the solid phase sample: Accurately weigh the solid phase sample obtained in Step 3. The mass of the solid phase sample is the same as the mass of pure potassium chloride in Step 2.

1. Then, accurately measure the same volume of buffer solution, water-soluble indicator solution, and distilled water as in Step 2.1 and add them to the solid phase sample. After fully dissolving, add long-chain alkane according to the same volume ratio of organic phase to water phase as in Step 2.1; extract and shake well fully, and after standing and separating layers, use long-chain alkane as the blank, and use a quartz cuvette to measure the absorbance of the organic phase layer, and calculate the octadecylamine content in the solid phase sample through the standard curve.

2. The method for determining octadecylamine in a potassium fertilizer flotation slurry as described in claim 1, characterized in that, The dissolution, color development, and extraction are all carried out in the same closed container.

3. The method for determining octadecylamine in a potassium fertilizer flotation slurry as described in claim 1, characterized in that, The concentration range of the octadecylamine stock solution is 0.5 mg / L - 100 mg / L.

4. The method for determining octadecylamine in a potassium fertilizer flotation slurry according to claim 1, characterized in that, The water-soluble indicator is a water-soluble indicator solution with a concentration of 0.1 - 20 g / L.

5. The method for determining octadecylamine in the potassium fertilizer flotation slurry according to claim 1, characterized in that, The buffer solution is an acetic acid-sodium acetate buffer solution, and the acetic acid-sodium acetate buffer solution is prepared through the following steps: Weigh anhydrous sodium acetate and dissolve it in distilled water, add acetic acid to adjust the pH of the solution to obtain an acetic acid-sodium acetate buffer solution with a pH of 4.5 - 6.

0.

6. The method for determining octadecylamine in a potassium fertilizer flotation slurry as described in claim 1, characterized in that, The water-soluble indicator is sodium bromocresol green, potassium bromocresol green, sodium bromophenol blue, or potassium bromophenol blue.

7. The method for determining octadecylamine in the potassium fertilizer flotation slurry according to claim 1, wherein The long-chain alkane is C n H 2n+2 , where n = 7 - 14.

8. The method for determining octadecylamine in a potassium fertilizer flotation slurry according to claim 1, characterized in that, The buffer solution is an acetic acid-sodium acetate buffer solution, and the volume ratio of the acetic acid-sodium acetate buffer solution to the water-soluble indicator solution is (5 - 100):

1.

9. The method for determining octadecylamine in a potassium fertilizer flotation slurry as described in claim 1, wherein The defoaming agent is an organosilicon defoaming agent, and 0.1 - 20 mL of the defoaming agent is added to each liter of the slurry.

10. Application of the method for determining octadecylamine in the potassium fertilizer flotation slurry according to any one of claims 1 - 9 in evaluating the dosage of flotation reagents.

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