Infrared quantitative analysis method for extracting polar organic residues in aqueous phase, application and system thereof

Abstract

The application discloses an infrared quantitative analysis method for extracting polar organic residues in an aqueous phase, application and system thereof. The method takes an infrared oil detector as a detection platform, adopts tetrachloroethylene liquid-liquid extraction to transfer target polar organic matters in the aqueous phase to an organic phase, effectively avoids strong absorption interference of water molecules, establishes a special calibration curve for the target polar organic matters, separates non-polar coexisting oils by means of magnesium silicate adsorption, and calculates and deducts interference by combining total oil equivalent concentration and net value of oil equivalent concentration, which is helpful to realize accurate quantification of the polar organic residues. The parallel determination relative standard deviation of the method is less than 0.5%, single sample analysis time is short, no expensive equipment is needed, the method is suitable for high-salt complex aqueous phase systems such as lithium extraction in salt lakes and hydrometallurgy, and can be applied to extraction agent loss monitoring and process optimization.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis and detection technology, specifically to an infrared quantitative analysis method and its application and system for extracting polar organic residues in aqueous phases, which is particularly suitable for the quantitative analysis of extractant residues with polar groups in aqueous phases during industrial processes such as salt lake resource separation and extraction and hydrometallurgy. Background Technology

[0002] Solvent extraction is commonly used in the wet extraction of strategic resources such as lithium, boron, cobalt, and nickel. Polar organic compounds containing hydroxyl and amino groups, such as isooctanol, C14-C16 long-chain mixed alcohols, and trioctylamine, are often used as modifiers or co-extractants. These organic residues inevitably dissolve and are carried in the aqueous phases such as raffinate and back-extraction solution. Accurate determination of their content is a core requirement for controlling extractant loss, optimizing process parameters, and monitoring environmental emissions. Especially in high-salinity brine systems of salt lakes, organic residues may also contaminate subsequent adsorption units and reduce adsorption capacity; therefore, rapid and accurate quantitative detection is an urgent industry need.

[0003] In actual testing, the strong absorption interference of water molecules and the cross-interference of coexisting nonpolar oils are the two core technical challenges restricting the accurate quantification of polar organic residues. Currently, infrared detection technologies for aqueous organic residues are mainly divided into two categories: direct measurement methods and indirect measurement methods, neither of which can simultaneously and systematically solve the aforementioned two major challenges. (1) Direct determination method This method requires no pretreatment and directly performs infrared detection on water samples. The core challenge lies in the strong absorption of water molecules in the mid-infrared region, which easily masks the characteristic signals of target organic matter. It mainly includes two technical routes: First, the attenuated total reflectance (ATR) route. This route significantly shortens the effective optical path by utilizing the short evanescent wave penetration depth of the ATR crystal, thereby mitigating the strong absorption interference from water. For example, the mid-infrared attenuated total reflectance spectroscopy detection method disclosed in patent application US20130037719A1 utilizes the hydrophilicity and hydrophobicity of unmodified ATR crystals to enrich the analytes, allowing direct determination of low-concentration organic pollutants in water samples. However, this method only obtains the total organic absorption signal and cannot distinguish the contributions of polar target extractants and coexisting non-polar oils, failing to solve the problem of differentiating between polar and non-polar interfering substances. Furthermore, it relies on dedicated ATR crystals and matching optical systems, resulting in high hardware costs. When dealing with high-salinity brine matrices from salt lakes, baseline distortion easily occurs, making quantitative accuracy difficult to guarantee. Second, the direct transmission route. Water samples are placed in a transmission liquid cell for direct detection, but the absorption intensity of water molecules in the mid-infrared region can reach 10. 3 L·mol -1 ・cm -1The concentration of organic matter is on the order of magnitude of water, while the characteristic absorption intensity of CH in target organic matter is only 1 / 10 to 1 / 100 that of water. When the concentration of organic matter is below 1000 mg / L, its signal is completely submerged in the strong absorption background of water. The optical dynamic range of conventional instruments cannot meet the detection requirements of trace residues.

[0004] (2) Indirect determination method This type of method transfers organic matter from the aqueous phase to the organic phase through liquid-liquid extraction before infrared detection, eliminating spectral interference from water molecules and dissolved salts. Conventional infrared spectrophotometry, represented by HJ 637-2018, is the mainstream approach in this route, employing tetrachloroethylene extraction and magnesium silicate adsorption separation to determine total oil, petroleum hydrocarbons, and animal and vegetable oils in water. However, this method is only developed for conventional oils, designed to distinguish between non-polar petroleum hydrocarbons and polar animal and vegetable oils. In this system, magnesium silicate is used to adsorb and remove polar components and quantify non-polar petroleum hydrocarbons, a quantitative logic that does not match the requirement of "targeting polar organic matter." Furthermore, it lacks a dedicated quantitative system for specific polar organic residues and a standardized calculation method to accurately deduct interference from coexisting oils. In addition, existing technologies generally fail to effectively integrate functional modules such as liquid-liquid extraction enrichment, selective component separation, and dedicated calibration curve quantification. The total oil value directly measured in complex aqueous systems cannot represent the true concentration of polar organic residues.

[0005] In addition, existing technologies for detecting organic components in oil-phase matrices, such as the handheld near-infrared oil alcohol detection system disclosed in CN202010037493.7, use near-infrared transmittance and reflectance spectroscopy to acquire oil sample signals, enabling on-site detection of alcohol components in oil-phase matrices in the petrochemical field. However, this approach targets oil-phase samples and does not need to consider the strong absorption interference of water molecules, thus it cannot be directly applied to the determination of trace polar organic residues in aqueous systems.

[0006] In summary, there is currently no dedicated infrared detection scheme that can simultaneously handle strong absorption interference from water matrix and distinguish between polar / non-polar interfering substances. There is still room for improvement in balancing detection accuracy, detection efficiency, and operating costs. Summary of the Invention

[0007] The purpose of this invention is to provide an infrared quantitative analysis method for polar organic residues in aqueous extracts, along with its application and system. Based on a general-purpose infrared oil analyzer platform, this method combines extraction matrix conversion, a dedicated calibration curve, and net value difference interference subtraction to achieve rapid, accurate, and low-cost quantification of polar extractant residues in high-salt, complex aqueous phases.

[0008] This invention protects an infrared quantitative analysis method for extracting polar organic residues from an aqueous phase, specifically comprising the following steps: Step 1, Extraction and Total Oil Determination: Take the aqueous phase sample to be tested, add tetrachloroethylene as the extractant for liquid-liquid extraction, shake vigorously and allow to stand for separation, collect the lower organic phase containing polar organic residues, and use an infrared oil analyzer to determine the total oil absorbance value; tetrachloroethylene has good extraction efficiency for organics with polar groups. After extraction, only the target polar organics and possible coexisting oil substances are retained in the organic phase, and the spectral interference of water molecules and dissolved salts is effectively eliminated.

[0009] Step 2, Establishment of dedicated calibration curve: Using the target polar organic compound as a standard substance, prepare a series of standard working solutions with concentration gradients, use an infrared oil analyzer to measure the total oil absorption value at each concentration point, and perform linear regression with concentration as the abscissa and total oil absorption value as the ordinate to establish a dedicated calibration curve for the target polar organic compound. Furthermore, the target polar organic compound is one or more of long-chain alcohols and long-chain amines.

[0010] Preferably, the target polar organic compound is one of isooctyl alcohol, C14-C16 mixed alcohol (A1416 mixed alcohol), and trioctylamine.

[0011] Furthermore, the linear correlation coefficient R of the dedicated calibration curve 2 The value should be no less than 0.96, and should be established using one of the following two methods: Method 1, direct dilution method: The high-concentration standard solution of the target polar organic compound is diluted stepwise with tetrachloroethylene to obtain a series of standard working solutions with concentration gradients, and the total oil absorbance is directly measured; a linear regression is performed with the original aqueous phase target compound concentration as the x-axis and the total oil absorbance as the y-axis to establish a dedicated calibration curve; this method is suitable for water samples with simple matrix.

[0012] Method 2, matrix matching method: A blank water sample with the same or similar matrix as the aqueous phase sample to be tested is used as the aqueous phase matrix. A high-concentration tetrachloroethylene standard solution of the target polar organic compound is added to the blank water sample according to the concentration gradient, and a series of matrix-matched water sample standard solutions are prepared by adjusting the volume. The series of water sample standard solutions are processed under the same liquid-liquid extraction conditions as in step 1, and the total oil absorption value of the extracted organic phase is measured. A linear regression is performed with the theoretical concentration of the target compound in the water sample as the abscissa and the total oil absorption value as the ordinate to establish a dedicated calibration curve. This method is suitable for complex aqueous phase samples such as high-salt and high-matrix samples.

[0013] Step 3, Magnesium silicate adsorption and oil content determination: Transfer the organic phase after the total oil content determination in Step 1 to a stoppered container containing pretreated magnesium silicate, shake to adsorb, filter, and take the filtrate to measure the absorption value again to obtain the oil content absorption value; substitute this absorption value into the same dedicated calibration curve established in Step 2 to calculate the equivalent oil content concentration. Within the concentration range determined by this method, magnesium silicate exhibits strong adsorption for the target polar organic compounds, essentially completely adsorbing them from the organic phase, with negligible residual adsorption in the filtrate. Conversely, coexisting non-polar oils are not adsorbed by magnesium silicate and remain in the organic phase. Therefore, the measured equivalent oil concentration only reflects the response contribution of coexisting non-polar oils. Furthermore, the pretreated magnesium silicate is 60-100 mesh, activated at 400℃ for 4 hours, and then cooled in a desiccator for later use; 0.3-1.0 g of pretreated magnesium silicate is added to every 20 mL of organic phase; the shaking adsorption time is 5-15 min; after adsorption by magnesium silicate, the residual infrared absorption value of the target polar organic matter in the organic phase drops to below 0.001.

[0014] Preferably, 0.5 g of pretreated magnesium silicate is added for every 20 mL of organic matter; the adsorption time is 10 min.

[0015] Step 4, Net Value Difference Calculation: Substitute the total oil absorption value and the oil absorption value into the dedicated calibration curve to calculate the equivalent concentration of total oil and the equivalent concentration of oil. The difference between the two is the residual content of the target polar organic compound in the aqueous sample to be tested. This method is applicable to process aqueous systems where the polar component is mainly the target extractant, and the contribution of other trace polar impurities can be ignored.

[0016] The dedicated calibration curve is the quantitative basis for converting total oil absorption value and oil absorption value into corresponding equivalent concentrations. Both measurements are based on the same calibration curve to ensure dimensional uniformity and accuracy of the difference calculation.

[0017] Furthermore, the total oil equivalent concentration includes the total response contribution of the target polar organic matter and the coexisting non-polar oils. After the target polar organic matter in the organic phase is removed by magnesium silicate adsorption, the measured oil equivalent concentration only includes the response contribution of the coexisting non-polar oils. The difference between the two is the true content of the target polar organic matter, thereby effectively deducting the interference of the coexisting non-polar oils.

[0018] This invention also protects the application of the above-mentioned infrared quantitative analysis method for polar organic residues in the aqueous phase of extraction, specifically for the quantitative analysis of polar organic residues in the raffinate and back-extraction samples during lithium and boron extraction; by adjusting the concentration range of the calibration curve, it can be extended to the detection of residues of other infrared active organic compounds with polar groups, including but not limited to n-butanol, cyclohexanol, methyl isobutyl ketone, and ethyl acetate.

[0019] This invention also protects a system for implementing the above method, including an extraction unit, an infrared oil analyzer, an adsorption treatment unit, and a data processing unit: The output end of the extraction unit is fluidly connected to the inlet end of the infrared oil analyzer and the inlet end of the adsorption processing unit, and is used to complete the liquid-liquid extraction operation between the aqueous sample to be tested and tetrachloroethylene, and output the lower organic phase test liquid. The infrared oil analyzer is used to receive the organic phase test liquid and measure the total oil absorption value, and to receive the filtrate after adsorption treatment and measure the oil absorption value. The adsorption treatment unit has a built-in pre-treated magnesium silicate, and its outlet end is fluidly connected to the sample inlet end of the infrared oil analyzer. It is used to receive the organic phase after the total oil measurement, remove the target polar organic matter through adsorption separation, and output the filtrate to the infrared oil analyzer. The data processing unit is connected to the infrared oil analyzer and has a built-in dedicated calibration curve for the target polar organic compound. It is used to automatically complete the concentration conversion and net value difference calculation, and output the residual content result of the target polar organic compound.

[0020] Furthermore, the data processing unit has a pre-stored dedicated calibration curve equation corresponding to the target polar organic compound, which can automatically complete the conversion from absorbance value to concentration and the net value difference calculation; the target polar organic compound is one of isooctyl alcohol, C14-C16 mixed alcohol, and trioctylamine.

[0021] Compared with existing technologies, the present invention has the following beneficial effects: This invention employs tetrachloroethylene liquid-liquid extraction to transfer target polar organic compounds from the aqueous phase to the organic phase, avoiding strong absorption interference from water molecules. A dedicated calibration curve is established for the target polar organic compounds. Non-polar coexisting oils are separated by magnesium silicate adsorption. Interference is deducted by calculating the net value of the total oil equivalent concentration minus the oil equivalent concentration, achieving accurate quantification of polar organic residues. Specific beneficial effects are as follows: 1. It expands the application of infrared oil analyzers in the field of polar organic residue detection, and applies them to the quantitative analysis of polar alcohols and amine extractants.

[0022] 2. The application of magnesium silicate adsorption logic in conventional infrared oil determination has been changed. It has been transformed from "adsorbing polar impurities and quantifying non-polar target substances" to the reverse utilization of the selective adsorption characteristics of magnesium silicate on polar organic matter. Combined with the subtraction of total oil-oil net value difference to deduct the cross-interference of coexisting non-polar oils, it can be applied to the quantitative analysis of polar target substances in complex aqueous phases with multiple components coexisting.

[0023] 3. The relative standard deviation of parallel determinations is less than 0.5%, and the repeatability of gas chromatography in high-salt matrices is usually higher.

[0024] 4. It can be achieved using a common infrared oil analyzer, without the need for expensive ATR accessories or chromatographs, high-purity carrier gas, or professional maintenance, which greatly reduces the detection threshold and operating costs, making it suitable for widespread application in industrial settings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall process of the method of the present invention; Figure 2 This is a calibration curve diagram for isooctanol in Example 1 of the present invention; Figure 3 This is a calibration curve diagram for the A1416 mixed alcohol in Example 2 of the present invention; Figure 4 This is a calibration curve diagram for trioctylamine in Example 3 of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise stated, the pretreated magnesium silicate used in the following examples all adopted the same specifications: particle size of 60-100 mesh, activated in a muffle furnace at 400℃ for 4 hours before use, cooled and placed in a desiccator for later use; the characteristic wavenumber detected by the infrared oil analyzer was 2930 cm⁻¹. -1 2960cm -1 3030cm -1 It conforms to the HJ 637-2018 standard testing specifications.

[0028] 1. Scheme Design Process 1.1 Selection and Design Ideas of the Testing Platform The starting point of this invention is to solve the problem of quantitative detection of polar organic residues in high-salt, complex aqueous phases during industrial processes such as lithium extraction from salt lakes and hydrometallurgy. After analyzing the limitations of existing technologies, the inventors established the following design concept: (1) Selection of detection platform: Gas chromatography is severely affected by high-salt matrices and has poor repeatability; ATR infrared method has high equipment costs and cannot distinguish between polar and non-polar components. Infrared oil analyzers, as conventional equipment for oil detection in water quality, have been widely deployed in the industry and have the advantages of low cost and simple operation, but in the existing technology they are only used for total oil content detection. This invention selects an infrared oil analyzer as the detection platform and breaks through its application limitations through methodological innovation.

[0029] (2) Analysis of core issues: The infrared oil analyzer is based on the CH bond at 2930 cm -1 2960cm -1 3030cm -1Quantification is achieved through characteristic absorption at the analyte. Organic compounds with polar groups (alcohols, amines) also contain CH bonds and theoretically can produce infrared absorption responses. However, existing methods establish calibration curves using mixed hydrocarbon standards, which cannot achieve precise quantification of specific polar organic compounds; furthermore, non-polar oils coexisting in the aqueous phase also produce CH absorption, interfering with the determination of polar target compounds.

[0030] (3) Technical Solution Concept: Addressing the two core issues mentioned above, this invention proposes the following concept: First, a dedicated calibration curve is established using the target polar organic compound itself as a standard substance to achieve single-component quantification; second, the selective adsorption characteristics of magnesium silicate on polar organic compounds are utilized to calculate and deduct interference from coexisting non-polar oils by the difference between the total oil and oil fraction equivalent concentrations. The synergistic effect of these two methods transforms the infrared oil analyzer from a tool for detecting total oil content into a dedicated quantitative tool for polar organic residues.

[0031] (4) Matrix adaptation strategy: For complex matrices with high salt and high acidity, such as salt lake brine, a matrix matching calibration method is designed. A standard series is prepared with actual process blank water samples as background to eliminate the influence of matrix effect on extraction efficiency and infrared response.

[0032] 1.2 Extractant Selection and Extraction Ratio Optimization Experiment Tetrachloroethylene (C2Cl4) was selected as the extractant. Tetrachloroethylene has extremely low infrared absorption in the characteristic wavenumber range of detection, which does not interfere with the determination of the target analyte. Moreover, its density is greater than that of water (1.62 g / mL), so the organic phase is located in the lower layer after extraction, which is convenient for separation and collection.

[0033] To determine the optimal extraction ratio, isooctanol was used as a model compound. Different volume ratios (V / L) of the aqueous phase to tetrachloroethylene were investigated in 100 mL of simulated salt lake brine (containing 200 g / L NaCl and 35 mg / L isooctanol). 水 :V 有 The effects of ratios (2:1, 3:1, 5:1, 7:1, 10:1) on extraction recovery were investigated. Extraction time was fixed at 5 min, and oscillation intensity was consistent. The lower organic phase was collected and its absorbance was measured using an infrared oil analyzer. The results were then substituted into the isooctanol calibration curve to calculate the recovery rate (results are shown in Table 1).

[0034] Table 1. Effect of different volume ratios of aqueous phase to tetrachloroethylene on extraction recovery.

[0035] As shown in Table 1, when the volume ratio of aqueous phase to tetrachloroethylene increased from 2:1 to 10:1, the extraction recovery rate gradually decreased from 99.4% to 87.8%. At a volume ratio of 5:1, the recovery rate was 97.8%, with little difference from the recovery rates of 2:1 and 3:1 (<2%), but the amount of tetrachloroethylene used was only 20 mL, significantly lower than that of 2:1 (50 mL) and 3:1 (33.3 mL), thus greatly reducing the amount of extractant while maintaining extraction efficiency. When the volume ratio increased to above 7:1, the recovery rate dropped below 93%, failing to meet the requirements for quantitative analysis.

[0036] Taking into account extraction efficiency, solvent consumption, and analysis cost, the optimal volume ratio of the aqueous phase to tetrachloroethylene was determined to be 5:1, i.e., 20 mL of tetrachloroethylene was added to 100 mL of the aqueous sample. This ratio achieves the best balance between recovery rate and solvent consumption.

[0037] 1.3 Optimization Experiment of Extraction Time With the extraction ratio set at 5:1, the effect of different extraction times on the recovery rate of isooctanol was investigated. The experimental conditions were the same as above, except that the shaking time was changed (the results are shown in Table 2).

[0038] Table 2. Effect of different extraction times on extraction recovery rate

[0039] As shown in Table 2, extending the extraction time from 1 min to 5 min significantly increased the recovery rate from 85.5% to 97.8%. Further extending the time to 7 min and 10 min only increased the recovery rate by 0.3% and 0.5% respectively, showing little improvement. Considering analytical efficiency, the optimal extraction time was determined to be 5 min. At this time, the extraction has essentially reached equilibrium, and the analysis cycle is short, meeting the needs of rapid detection in industrial settings.

[0040] 1.4 Design and Validation of the Logic for Subtracting Quantitative Values ​​from Equivalent Concentration Difference of Total Oil and Oil Separates The core logic of differential quantitative analysis is that after tetrachloroethylene extraction, the organic phase simultaneously contains the target polar organic compound (M_polar) and coexisting nonpolar oils (M_non-polar), both of which contain CH bonds and are effective at 2930 cm⁻¹. -1 2960cm -1 3030cm -1 Infrared absorption at that location contributes.

[0041] Total oil absorption value = target polar organic matter absorption value + non-polar oil absorption value After adsorption by magnesium silicate, polar organic matter is fully adsorbed and removed, leaving only non-polar oils: Oil absorption value = non-polar oil absorption value The difference between the two is the absorption contribution of the target polar organic compound: ΔAbsorption Value = Total Oil Absorption Value - Oil Separation Absorption Value = Target Polar Organic Compound Absorption Value Substituting the Δabsorption value (ΔA) into the dedicated calibration curve established using the target polar organic compound as a standard, the true concentration of the target polar organic compound is obtained. Since the same calibration curve is used for both measurements, the response of non-polar oils is automatically eliminated during the difference subtraction process, without affecting the final quantitative result.

[0042] To verify the effectiveness of this logic, a spiked interference experiment was conducted: different concentrations of n-hexadecane (simulating non-polar oil interference) were added to the isooctanol tetrachloroethylene standard solution (35 mg / L), and the isooctanol content was determined according to this method (the results are shown in Table 3).

[0043] Table 3. Validation of the elimination of interference from coexisting nonpolar oils (isooctanol spiked at 35 mg / L)

[0044] As shown in Table 3, even with a coexisting non-polar oil (n-hexadecane) concentration as high as 100 mg / L (nearly three times the isooctanol concentration), the measured isooctanol value, after subtracting the total oil from the oil fraction, remained almost identical to that without interference, with a stable recovery rate above 99.89%. This indicates that the differential quantitative logic of this invention can effectively eliminate the interference of coexisting non-polar oils, achieving accurate quantification of polar organic residues.

[0045] Example 1

[0046] This embodiment tests the residue of isooctyl alcohol (a polar organic compound containing hydroxyl groups) in the extract of boron extraction from salt lakes.

[0047] (1) Instruments and reagents Infrared oil analyzer (model OL680); tetrachloroethylene (analytical grade); isooctyl alcohol (purity ≥99.5%); pretreated magnesium silicate (60~100 mesh, activated at 400℃ for 4h); n-hexadecane (purity ≥99%); simulated salt lake brine (NaCl 200g / L, pH=2.0).

[0048] (2) Establishment of a dedicated calibration curve for isooctyl alcohol A matrix-matched calibration curve was established. 1.400 g of isooctanol was accurately weighed and diluted to 50 mL with tetrachloroethylene to obtain a high-concentration standard solution of 28.0 g / L. This solution was then serially diluted to obtain intermediate solutions. Six 100 mL aliquots of simulated brine blank water samples were taken, and isooctanol standard solution was added to each sample to prepare matrix-matched standard solutions with concentrations of 0, 35, 70, and 105 mg / L. Each water sample was subjected to liquid-liquid extraction under the conditions of step 1 (100 mL aqueous phase, 20 mL tetrachloroethylene, shaking for 5 min). The lower organic phase was collected and the total oil absorbance was determined using an infrared oil analyzer (results are shown in Table 4, Appendix). Figure 2 ).

[0049] Table 4. Data for the calibration curve of isooctyl alcohol.

[0050] A linear regression was performed with concentration x on the x-axis and total oil absorption y on the y-axis to obtain the equation for the isooctanol-specific calibration curve: y = 0.0878x, R0 2 =0.9987; good linearity, which helps in the accurate quantification of isooctyl alcohol.

[0051] (3) Confirmation of oil separation response Take 20 mL of the organic phase of each of the above concentration standard solutions, add 0.5 g of pretreated magnesium silicate, shake and adsorb for 10 min, filter, and measure the absorbance of the filtrate. The results show that the absorbance values ​​after adsorption at each concentration point are all less than 0.001, indicating that isooctyl alcohol is fully adsorbed by magnesium silicate, the oil response is negligible, and the differential quantitative logic is valid.

[0052] (4) Actual sample determination Take 100 mL of the raffinate from a lithium extraction process in a salt lake and extract it with tetrachloroethylene (20 mL, 5 min) according to step 1. Take the organic phase and measure the total oil absorbance value, which is 3.2856. Substitute it into the calibration curve to obtain the equivalent concentration of total oil of 37.42 mg / L. Take the organic phase after measurement, add 0.5 g of magnesium silicate for adsorption for 10 min, filter it, and measure the absorbance value, which is 0.0152. Substitute it into the same calibration curve to obtain the equivalent concentration of oil of 0.17 mg / L.

[0053] Isooctyl alcohol residue content = 37.42 - 0.17 = 37.25 mg / L.

[0054] The same sample was measured in parallel 6 times, with an RSD of 0.32%, indicating excellent repeatability.

[0055] Example 2

[0056] This embodiment tests the residue of A1416 (a mixed C14-C16 alcohol, a polar organic compound containing hydroxyl groups) in the back-extraction solution of the boron extraction process in salt lakes.

[0057] (1) Establishment of calibration curve Using the matrix-matched method, 14.00 g of A1416 (a C14-C16 mixed alcohol) was accurately weighed and diluted to 50 mL with tetrachloroethylene to obtain a high-concentration standard solution of 280.0 g / L. 100 mL of each simulated brine blank sample was taken and A1416 standard solution was added to prepare matrix-matched standard solutions with concentrations of 0, 35, 70, and 105 mg / L. After extraction under the conditions of step 1, the total oil absorbance was determined (results are shown in Table 5, appendix). Figure 3 ).

[0058] Table 5. A1416 Dedicated Calibration Curve Data

[0059] Linear regression yielded the calibration curve equation for the A1416 mixed alcohols: y = 0.1023x + 1.336, R 2 =0.9934 Note: The intercept of 1.336 represents the contribution of trace background organic matter in the blank water sample matrix. This is subtracted from the blank in the matrix matching method and does not affect the accuracy of quantification.

[0060] (2) Confirmation of oil separation response After each concentration of standard solution was adsorbed by 0.5g of magnesium silicate for 10 minutes, the absorbance values ​​were all less than 0.001, indicating that the A1416 mixed alcohol was fully adsorbed by magnesium silicate, and the differential quantitative logic was valid.

[0061] (3) Actual sample determination 100 mL of boron extraction solution from a salt lake was extracted according to step 1. The total oil absorbance was measured to be 6.5240. Substituting this value into the calibration curve, the equivalent total oil concentration was found to be 50.62 mg / L. After adsorption with magnesium silicate, the absorbance was measured to be 0.0210, yielding an equivalent oil concentration of 0.21 mg / L.

[0062] A1416 residue content = 50.62 - 0.21 = 50.41 mg / L.

[0063] Six parallel measurements were performed, and the RSD was 0.41%.

[0064] Example 3

[0065] This embodiment tests for trioctylamine (a polar organic compound containing amino groups) residue in the raffinate of a hydrometallurgical process.

[0066] (1) Establishment of calibration curve Trioctylamine exhibits a lower CH absorption response than alcohols (smaller absorbance per unit concentration), requiring a higher calibration concentration range. Accurately weigh 2.100 g of trioctylamine and dilute to 50 mL with tetrachloroethylene. Prepare matrix-matched standard solutions with concentrations of 0, 210, 420, and 630 mg / L using 100 mL blank samples of simulated brine from a salt lake. Extract according to the conditions in step 1 and determine the total oil absorbance (results are shown in Table 6). Figure 4 ).

[0067] Table 6. Trioctylamine-specific calibration curve data

[0068] Linear regression yielded the equation for the trioctylamine-specific calibration curve: y = 0.0128x + 0.0154, R 2 =0.9991 Excellent linearity, with an intercept of 0.0154 close to zero, indicating minimal background interference.

[0069] (2) Confirmation of oil separation response After each concentration of standard solution was adsorbed by 0.5g of magnesium silicate for 10 minutes, the absorbance values ​​were all less than 0.001, indicating that trioctylamine was fully adsorbed by magnesium silicate, and the differential quantitative logic was valid.

[0070] (3) Actual sample determination 100 mL of raffinate from a hydrometallurgical process was extracted according to step 1. The total oil absorbance was measured to be 4.0265. Substituting this value into the calibration curve, the equivalent total oil concentration was found to be 313.28 mg / L. After adsorption with magnesium silicate, the absorbance was measured to be 0.0089, yielding an equivalent oil concentration of 0.69 mg / L.

[0071] Trioctylamine residue content = 313.28 - 0.69 = 312.59 mg / L.

[0072] Six parallel measurements were performed, and the RSD was 0.28%.

[0073] Example 4

[0074] Comparison and verification of matrix matching method and direct dilution method To verify the advantages of matrix matching in high-salt complex systems, isooctanol calibration curves were established using both the direct dilution method and the matrix matching method, and the results were compared using the same actual sample. The x-axis of both calibration curves was uniformly set to the theoretical concentration of the target analyte in the original aqueous phase.

[0075] (1) Comparison of the two calibration curves Direct dilution method: The isooctyl alcohol standard solution was directly diluted with tetrachloroethylene, and the concentration was converted to the corresponding aqueous phase concentration according to the 5:1 extraction enrichment ratio. Standard working solutions with concentrations of 0, 35, 70, and 105 mg / L were prepared, and the absorbance was directly measured (the results are detailed in Table 7).

[0076] Table 7 Comparison of two calibration curve methods (isooctanol)

[0077] As shown in Table 7, at concentrations of 35 mg / L and 70 mg / L, the absorbance values ​​of the direct dilution method were significantly higher than those of the matrix-matched method. The x-axis of both methods is uniformly represented by the converted theoretical concentration of the original aqueous phase. The standard for the direct dilution method was prepared with pure tetrachloroethylene and did not undergo an extraction process, assuming a 100% extraction recovery rate. In contrast, the standard for the matrix-matched method underwent the exact same liquid-liquid extraction process as the sample, and the absorbance value reflects the true extraction efficiency under high-salt matrices (affected by factors such as salting-out effect and phase distribution). These results indicate that high-salt matrices have an observable impact on extraction efficiency, and using calibration curves prepared with pure solvents directly for quantification introduces systematic bias.

[0078] (2) Comparison of actual sample measurements Take 100 mL of the lithium extraction residue sample from the same salt lake and quantify it using two different calibration curves (the results are shown in Table 8).

[0079] Table 8 Comparison of measurement results for actual samples using the two calibration methods.

[0080] Note: *The calibration curve for the direct dilution method is based on the assumption of 100% extraction recovery. The result obtained after substituting the total oil absorption value is the apparent concentration, which needs to be corrected by the extraction recovery (97.8%). After correction, it is 37.42×97.8%≈36.60mg / L. After deducting the oil content of 0.17mg / L, it is 36.43mg / L.

[0081] The results show that the matrix matching method can obtain accurate results directly without additional calibration, and the relative deviation between the measured value and the GC-MS reference value is about 10.2%, which is within the reasonable error range for the detection of high-salt complex matrices. The direct dilution method requires prior determination of recovery rate and calibration, which is more cumbersome. For routine industrial batch testing, the matrix matching method is simpler and more reliable.

[0082] Example 5

[0083] Method repeatability verification and comparison with GC-FID (1) Repeatability verification Take a simulated water sample spiked with isooctyl alcohol (equivalent to an aqueous phase concentration of 35 mg / L) and perform 8 parallel determinations according to this method (the results are shown in Table 9).

[0084] Table 9. Repeatability verification results of the method of the present invention (isooctanol, spiked 35 mg / L)

[0085] The average value was 34.98 mg / L; the standard deviation was 0.025 mg / L; and the RSD was 0.07%. This method exhibits excellent repeatability.

[0086] (2) Comparison with GC-FID Lithium extraction residue samples from the same salt lake were taken and measured in parallel using the method of this invention and GC-FID (6 times each). The precision of the two methods was compared (the results are shown in Table 10).

[0087] Table 10 Comparison of precision between the method of this invention and GC-FID (isooctanol)

[0088] As shown in Table 10, the RSD of the method of this invention for six parallel determinations is 0.32%, demonstrating excellent data stability. In contrast, the GC-FID method is susceptible to interference from high-salt matrices, with salt accumulation in the injection port liner and rapid column deterioration leading to peak tailing, large integration errors, and a relative deviation of 35.2% between parallel samples. This significant data fluctuation fails to meet the requirements for stable monitoring in industrial processes. For water samples with higher salinity and more complex matrices, the parallel sample deviation of GC-FID can further increase to over 50%. The method of this invention transfers the target analyte to the organic phase through tetrachloroethylene extraction, significantly reducing the direct impact of high-salt matrices on the detection system, and exhibits significantly better repeatability than gas chromatography.

[0089] Example 6

[0090] Method universality verification To verify the applicability of this method to other infrared-active organic compounds with polar groups, three polar organic compounds, n-butanol (short-chain alcohol), cyclohexanol (alicyclic alcohol), and methyl isobutyl ketone (MIBK, ketone), were selected for verification experiments.

[0091] Using three organic compounds as standard substances, dedicated calibration curves were established according to the matrix matching method to examine linear correlation; and spiked water samples were prepared for recovery determination (results are shown in Table 11).

[0092] Table 11 Applicability Verification of Methods for Other Polar Organic Compounds

[0093] As shown in Table 11, the calibration curves R for the three polar organic compounds n-butanol, cyclohexanol, and MIBK are... 2All values ​​were ≥0.996, and the recoveries were all between 98.47% and 98.8%, indicating that this method has good applicability to different types of polar organic compounds (short-chain alcohols, alicyclic alcohols, and ketones). By adjusting the calibration concentration range and standard substances, this method can be extended to the quantitative detection of other organic compounds with polar groups and infrared activity.

[0094] Example 7

[0095] This embodiment demonstrates an application of continuous monitoring at the process site. This method, combined with an automated liquid-liquid extraction device and an online infrared oil analyzer, was used for continuous online monitoring of the raffinate in a boron extraction production line at a salt lake. Automatic sampling and testing were performed every 2 hours, with continuous operation for 72 hours, yielding 36 sets of data. The isooctanol residual concentration ranged from 31.2 to 38.6 mg / L, and the RSD of parallel samples was <1.0%. The test results can be uploaded to the process control system in real time, providing data support for extractant loss calculation and process parameter adjustment, and offering preliminary practical reference for the operation of this method in industrial settings.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An infrared quantitative analysis method for extracting polar organic residues from an aqueous phase, characterized in that, Specifically, the steps include the following: Step 1, Extraction and Total Oil Determination: Take the aqueous phase sample to be tested, add tetrachloroethylene as the extractant for liquid-liquid extraction, shake vigorously and let stand to separate the layers, collect the lower organic phase, and use an infrared oil analyzer to determine the total oil absorbance value. Step 2, Establishment of dedicated calibration curve: Using the target polar organic compound as a standard substance, prepare a series of standard working solutions with concentration gradients, measure the total oil absorption value at each concentration point, and perform linear regression with concentration as the abscissa and total oil absorption value as the ordinate to establish a dedicated calibration curve for the target polar organic compound. Step 3, Magnesium silicate adsorption and oil content determination: Transfer the organic phase after the total oil content determination in Step 1 to a stoppered container containing pretreated magnesium silicate, shake to adsorb, filter, and take the filtrate to measure the absorption value again to obtain the oil content absorption value. Step 4, Net Value Difference Calculation: Substitute the total oil absorption value and the oil absorption value into the dedicated calibration curve respectively to calculate the total oil equivalent concentration and the oil equivalent concentration. The difference between the two is the residual content of the target polar organic matter in the aqueous sample to be tested.

2. The analytical method according to claim 1, characterized in that, The target polar organic compound is one or more of long-chain alcohols and long-chain amines.

3. The analytical method according to claim 2, characterized in that, The target polar organic compound is one of isooctyl alcohol, C14-C16 mixed alcohol, or trioctylamine.

4. The analytical method according to claim 1, characterized in that, The dedicated calibration curve was established using the direct dilution method. The high-concentration standard solution of the target polar organic compound was gradually diluted with tetrachloroethylene to obtain a series of standard working solutions with different concentration gradients. The total oil absorption value was then directly measured. A linear regression was performed with the original aqueous phase target compound concentration as the x-axis and the total oil absorption value as the y-axis to establish the dedicated calibration curve.

5. The analytical method according to claim 1, characterized in that, The dedicated calibration curve is established using the matrix matching method. A blank water sample with the same or similar matrix as the aqueous phase sample to be tested is used as the aqueous phase matrix. A high-concentration tetrachloroethylene standard solution of the target polar organic compound is added to the blank water sample according to the concentration gradient, and a series of matrix-matched water sample standard solutions are prepared by adjusting the volume. The series of water sample standard solutions are processed under the same liquid-liquid extraction conditions as in step 1, and the total oil absorption value of the extracted organic phase is measured. A linear regression is performed with the theoretical concentration of the target compound in the water sample as the abscissa and the total oil absorption value as the ordinate to establish the dedicated calibration curve.

6. The analytical method according to claim 1, characterized in that, The pretreated magnesium silicate is 60-100 mesh, activated at 400℃ for 4 hours and then cooled in a desiccator for later use; 0.3-1.0 g of pretreated magnesium silicate is added to every 20 mL of organic phase; the adsorption time is 5-15 min; after adsorption by magnesium silicate, the residual infrared absorption value of the target polar organic matter in the organic phase drops to below 0.

001.

7. The analytical method according to claim 1, characterized in that, The total oil equivalent concentration includes the total response contribution of the target polar organic matter and coexisting non-polar oils. After the target polar organic matter in the organic phase is removed by magnesium silicate adsorption, the measured oil equivalent concentration only includes the response contribution of coexisting non-polar oils. The difference between the two is the true content of the target polar organic matter, thereby effectively deducting the interference of coexisting non-polar oils.

8. The application of the infrared quantitative analysis method for polar organic residues in an aqueous extract according to any one of claims 1-7, characterized in that, The method is used for the quantitative analysis of polar organic residues in the raffinate and back-extraction samples during lithium and boron extraction. By adjusting the concentration range of the calibration curve, it can be extended to the detection of residues of other infrared-active organic compounds with polar groups, including but not limited to n-butanol, cyclohexanol, methyl isobutyl ketone, and ethyl acetate.

9. An infrared quantitative analysis system for extracting polar organic residues from an aqueous phase, characterized in that, The system is used to implement the analytical method according to any one of claims 1-7, and includes an extraction unit, an infrared oil analyzer, an adsorption treatment unit, and a data processing unit. The output end of the extraction unit is fluidly connected to the inlet end of the infrared oil analyzer and the inlet end of the adsorption processing unit, and is used to complete the liquid-liquid extraction operation between the aqueous sample to be tested and tetrachloroethylene, and output the lower organic phase test liquid. The infrared oil analyzer is used to receive the organic phase test liquid and measure the total oil absorption value, and to receive the filtrate after adsorption treatment and measure the oil absorption value. The adsorption treatment unit has a built-in pre-treated magnesium silicate, and its outlet end is fluidly connected to the sample inlet end of the infrared oil analyzer. It is used to receive the organic phase after the total oil measurement, remove the target polar organic matter through adsorption separation, and output the filtrate to the infrared oil analyzer. The data processing unit is connected to the infrared oil analyzer and has a built-in dedicated calibration curve for the target polar organic compound. It is used to automatically complete the concentration conversion and net value difference calculation, and output the residual content result of the target polar organic compound.

10. The analysis system according to claim 9, characterized in that, The data processing unit has a pre-stored dedicated calibration curve equation corresponding to the target polar organic compound, which can assist in automatically completing the conversion from absorbance value to concentration and the net value difference calculation; the target polar organic compound is one of isooctyl alcohol, C14-C16 mixed alcohol, and trioctylamine.

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