Indissolvable rock mineral isotope analysis method based on pretreatment purification

Abstract

The invention relates to the technical field of isotope analysis, in particular to an indissolvable rock mineral isotope analysis method based on pretreatment purification, which comprises the following steps: S1, sample pretreatment, crushing and screening; s2, layered dissolution and selective etching; s3, gradient centrifugation and ultrasonic dispersion; s4, carrying out vacuum microwave synergistic digestion; s5, dynamic adsorption purification; s6, purifying by using an ion exchange column; s7, concentrating the isotope solution; s8, measuring an isotope ratio; by improving the sample pretreatment, purification and determination process, the separation efficiency and determination precision of the target isotope in the indissolvable rock mineral are remarkably improved, and the problems of sample impurity interference and insufficient analysis precision in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of isotope analysis, and particularly to an isotope analysis method for refractory rock minerals based on pretreatment and purification. Background Art

[0002] Isotope analysis of refractory rock minerals is widely used in fields such as geology, archaeology, and environmental science, and can provide valuable information about mineral sources, geological evolution, and environmental changes. Traditional isotope analysis methods often face problems such as the difficulty of separating and purifying target isotopes in complex mineral matrices and low analysis accuracy; especially when dealing with refractory minerals, due to the presence of organic pollutants, impurity minerals, and strongly symbiotic minerals on the surface of mineral particles, the extraction and analysis processes of target isotopes become more difficult, affecting the accuracy and reliability of measurement results.

[0003] Therefore, developing an isotope analysis method for refractory rock minerals based on pretreatment and purification has become a technical problem urgently to be solved in the application field. Summary of the Invention

[0004] Based on the above object, the present invention provides an isotope analysis method for refractory rock minerals based on pretreatment and purification.

[0005] An isotope analysis method for refractory rock minerals based on pretreatment and purification includes the following steps: S1: Clean the surface of the rock mineral sample to remove attached organic pollutants, and mechanically crush and screen the cleaned sample to obtain uniformly sized powder. S2: Immerse the uniform powder obtained in S1 successively in hydrofluoric acid-nitric acid mixed solutions with gradually increasing concentrations for layered dissolution, and then add an etching solution to remove residual impurities during the dissolution process. S3: Perform two-stage centrifugation on the mixed solution treated in S2 to separate the target mineral precipitate; and place the precipitate in an ultrasonic oscillation device for dispersion treatment to form a uniform suspension. S4: Transfer the suspension in S3 to a vacuum microwave digestion container, and add a digestion solution for vacuum microwave digestion to completely dissolve the target mineral and obtain a digestion solution. S5: Dynamically adsorb the digestion solution in S4 through a microfluidic chip filled with nano-titanium oxide for preliminary purification of the digestion solution. S6: Selectively adsorb and elute the target isotope in the digestion solution purified in S5 using a series of resin columns to obtain a purified solution. S7: Place the purified solution obtained in S6 in a vacuum rotary evaporation device, reduce the volume of the solution through concentration treatment, and filter it through a filter membrane to remove fine colloidal particles to obtain an isotope solution. S8: Measure the isotopic solution concentrated in S7 using a mass spectrometer, and perform mass fractionation correction on the measurement data in combination with a reference material, and finally output the target isotope ratio data.

[0006] Optionally, the S1 specifically includes: S11: Place the rock mineral sample in a low-temperature plasma cleaner, and under an argon atmosphere, clean it for 10 - 30 minutes under the conditions of a power of 200 - 400 W, a gas flow rate of 5 - 10 L / min, and a pressure of 50 - 100 Pa to remove surface organic contaminants; S12: Crush the cleaned sample into coarse particles with a particle size of 1 - 3 mm through a jaw crusher; S13: Transfer the coarse particles to a ball mill and grind them at a rotation speed of 200 - 300 rpm for 2 - 4 hours; S14: Place the ground powder in a vibrating sieve shaker and sieve it for 10 - 20 minutes using a sieve mesh with a pore size of 50 μm to obtain uniformly sized powder.

[0007] Optionally, the S2 specifically includes: S21: Immerse the uniformly sized powder obtained in S1 in a hydrofluoric acid - nitric acid mixed solution in two stages: The first stage: Immerse it in a mixed solution of 5 - 10% hydrofluoric acid and 3 - 5% nitric acid at 50 - 70 °C for 1 - 2 hours to dissolve the symbiotic minerals such as feldspar and mica; The second stage: Immerse it in a mixed solution of 15 - 20% hydrofluoric acid and 5 - 8% nitric acid at 70 - 90 °C for 0.5 - 1 hour to dissolve the remaining ilmenite and hornblende; S22: Separate the residue after layered dissolution from the solution, add an etching solution containing 0.1 - 0.3 mol / L ammonium fluoride, and stir it at 40 - 60 °C at 200 - 300 rpm for 30 - 60 minutes to directionally remove the remaining apatite and quartz particles.

[0008] Optionally, the S3 specifically includes: S31: Perform a first-stage centrifugation treatment on the mixed solution treated in S2, with a centrifugal force of 500 - 1000 g and a centrifugation time of 10 - 15 minutes, to remove undissolved large particle impurities and retain the supernatant containing the target mineral; S32: Perform a second-stage centrifugation treatment on the supernatant obtained in S31, with a centrifugal force of 8000 - 12000 g and a centrifugation time of 20 - 30 minutes, to separate and obtain the target mineral precipitate; S33: Mix the target mineral precipitate obtained in S32 with ultrapure water at a solid-liquid ratio of 1:5 - 1:10, place it in an ultrasonic oscillation device, and perform dispersion treatment at a frequency of 20 - 40 kHz, a temperature of 4 - 10 °C, and an ultrasonic time of 10 - 20 minutes to form a homogeneous suspension.

[0009] Optionally, the specific steps of S4 are as follows: S41: Transfer the suspension obtained in S3 to the reaction kettle of a vacuum microwave digestion device, add a digestion solution containing 0.2 - 0.5 mol / L ammonium fluoride and 0.1 - 0.2 mol / L citric acid, and the solid-liquid ratio is 1:10 - 1:15; Pa, set the microwave power to 800 - 1000 W, heat up to 180 - 220 °C, and the digestion time is 30 - 60 minutes; S43: After digestion is completed, cool to room temperature, open the reaction kettle to obtain a completely dissolved digestion solution.

[0010] Optionally, the specific steps of S5 are as follows: S51: Pre-activate the microfluidic chip filled with nano-titanium oxide, rinse it with 0.5 - 1.0 mol / L hydrochloric acid at a flow rate of 0.2 - 0.5 mL / min for 10 - 15 minutes to activate the adsorption surface; S52: Inject the digestion solution of S4 into the microfluidic chip at a flow rate of 0.1 - 0.3 mL / min, control the temperature in the chip to be 25 - 40 °C and the pH value to be 2.5 - 3.5, so that rare earth elements and thorium selectively bind to nano-titanium oxide; S53: After adsorption is completed, rinse the chip in the reverse direction with 0.1 - 0.2 mol / L oxalic acid solution at a flow rate of 0.2 - 0.4 mL / min, and collect the purified digestion solution.

[0011] Optionally, the series resin columns in S6 include DGA resin column and TRU resin column.

[0012] Optionally, S6 further includes: S61: Load the digestion solution purified in S5 onto the DGA resin column at a flow rate of 0.3 - 0.6 mL / min, so that uranium and lead isotopes are adsorbed on the resin; S62: Elute the DGA resin column with 0.8 - 1.2 mol / L hydrochloric acid at a flow rate of 0.5 - 1.0 mL / min, and collect the eluate containing the target isotopes; S63: Load the eluate of S63 onto the TRU resin column, and adsorb the residual thorium and rare earth elements at a flow rate of 0.2 - 0.4 mL / min; S64: Elute the TRU resin column with 0.3 - 0.8 mol / L hydrochloric acid at a flow rate of 0.3 - 0.5 mL / min to obtain a purified solution.

[0013] Optionally, S7 specifically includes: S71: Transfer the purified solution obtained in S6 to a vacuum rotary evaporation device, set the water bath temperature to 50 - 60°C, the vacuum degree to 0.08 - 0.1 MPa, and perform rotary evaporation at a rotation speed of 50 - 100 r / min until the solution volume is reduced to 1 / 10 - 1 / 15 of the original volume; S72: Pass the concentrated solution through a polyethersulfone filter membrane with a pore size of 0.22 μm and filter it at a flow rate of 1 - 2 mL / min to remove fine colloidal particles; S73: Collect the filtered solution to obtain a high-purity isotope solution.

[0014] Optionally, S8 specifically includes: S81: Introduce the isotope solution concentrated in S7 into a multi-receiver inductively coupled plasma mass spectrometer at a flow rate of 0.2 - 0.5 mL / min, and set the radio frequency power to 1.2 - 1.5 kW, the carrier gas flow rate to 15 - 20 L / min, and the acquisition time to 60 - 75 seconds; S82: Measure the target isotope in the inductively coupled plasma mass spectrometer to obtain the preliminarily measured isotope ratio data, denoted as ; S83: Measure the standard substance NIST SRM987 under the same measurement conditions to obtain the measured isotope ratio data of the standard substance, denoted as , and at the same time, the theoretical isotope ratio of this standard substance is known as ; S84: Perform mass fractionation correction on according to the following correction formula to obtain the corrected isotope ratio data , and the formula is: .

[0015] Advantages of the present invention: In the present invention, through steps such as low-temperature plasma cleaning, layered dissolution, and selective etching, organic pollutants and non-target minerals in the sample can be effectively removed, and the target mineral components can be retained, providing a more uniform and pure sample for subsequent isotope analysis; these improvements have significantly enhanced the purification effect of the sample, thus laying a solid foundation for high-precision isotope ratio determination.

[0016] In the present invention, through innovative processes such as dynamic adsorption purification, tandem resin column purification, and vacuum rotary evaporation concentration, rare earth elements, thorium, and other impurities are effectively removed, avoiding their interference with the isotope analysis results; in the final mass fractionation correction process, precise correction is carried out in combination with the standard substance, further ensuring the accuracy and reliability of the isotope ratio data. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic diagram of the method for analyzing isotopes of refractory rock minerals according to an embodiment of the present invention; Figure 2 Schematic diagram of the vacuum microwave digestion process according to an embodiment of the present invention. Specific embodiments

[0019] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the accompanying drawings are only for more specifically describing the embodiments, and are not intended to specifically limit the present invention.

[0020] It should be noted that in the specification, references to "an embodiment", "embodiments", "exemplary embodiments", "some embodiments", etc. indicate that the described embodiments may include specific features, structures, or characteristics, but not necessarily every embodiment includes such specific features, structures, or characteristics. Additionally, when combining embodiments to describe specific features, structures, or characteristics, implementing such features, structures, or characteristics in combination with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the relevant art.

[0021] Generally, terms can be understood, at least in part, from their use in context. For example, at least in part depending on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or can be used to describe a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey a set of exclusive factors, but rather, at least in part depending on the context, can allow for the existence of other factors that may not be explicitly described.

[0022] Embodiment 1 As Figure 1 - Figure 2 shown, a method for analyzing isotopes of refractory rock minerals based on pretreatment and purification includes the following steps: S1: Clean the surface of the rock mineral sample to remove attached organic pollutants, and mechanically crush and screen the cleaned sample to obtain a powder with uniform particle size; S2: Immerse the homogeneous powder obtained in S1 successively into hydrofluoric acid-nitric acid mixed solutions with gradually increasing concentrations for hierarchical dissolution, then add an etching solution to remove residual impurities during the dissolution process and retain the target minerals. S3: Conduct two-stage centrifugation on the mixed solution processed in S2 to separate and precipitate the target minerals; place the precipitate in an ultrasonic vibration device for dispersion treatment to form a homogeneous suspension. S4: Transfer the suspension in S3 to a vacuum microwave digestion container, add a digestion solution for vacuum microwave digestion to completely dissolve the target minerals and obtain a digestion solution. S5: Dynamically adsorb the digestion solution in S4 through a microfluidic chip filled with nano-titanium oxide to adsorb residual interfering elements in the solution under continuous flow conditions and preliminarily purify the digestion solution. S6: Selectively adsorb and elute the target isotopes in the digestion solution purified in S5 using a series of resin columns to obtain a purified solution. S7: Place the purified solution obtained in S6 in a vacuum rotary evaporation device, reduce the volume of the solution through concentration treatment, and filter it through a filter membrane to remove fine colloidal particles to obtain a homogeneous and pure isotope solution. S8: Measure the isotope solution concentrated in S7 using a mass spectrometer, and correct the measurement data for mass fractionation in combination with a reference material, and finally output the target isotope ratio data.

[0023] S1 specifically includes: S11: Place the rock mineral sample in a low-temperature plasma cleaner and clean it for 15 minutes under the conditions of an argon atmosphere, a power of 300 W, a gas flow rate of 8 L / min, and a pressure of 80 Pa to remove surface organic pollutants. S12: Crush the cleaned sample into coarse particles with a particle size of 2 mm using a jaw crusher. S13: Transfer the coarse particles to a ball mill and grind them at a speed of 250 rpm for 3 hours. S14: Place the ground powder in a vibrating sieve shaker and screen it for 15 minutes using a sieve with a pore size of 50 μm to obtain a homogeneous powder.

[0024] S2 specifically includes: S21: Immerse the homogeneous powder obtained in S1 into the hydrofluoric acid-nitric acid mixed solution in two stages: The first stage: Immerse it in a mixed solution of 7% hydrofluoric acid and 4% nitric acid at 60 °C for 1.5 hours to dissolve the symbiotic minerals of feldspar and mica. The second stage: Immerse it in a mixed solution of 18% hydrofluoric acid and 6% nitric acid at 80 °C for 0.8 hours to dissolve the remaining ilmenite and hornblende. S22: Separate the residue after hierarchical dissolution from the solution, add an etching solution containing 0.2 mol / L ammonium fluoride, stir at 250 rpm for 40 minutes at 50 °C to directionally remove the residual apatite and quartz particles.

[0025] S3 specifically includes: S31: Perform the first-stage centrifugation on the mixed solution after S2 treatment, with a centrifugal force of 800 g and a centrifugation time of 12 minutes, to remove undissolved large particle impurities and retain the supernatant containing the target mineral. S32: Perform the second-stage centrifugation on the supernatant obtained in S31, with a centrifugal force of 10000 g and a centrifugation time of 25 minutes, to separate and obtain the target mineral precipitate. S33: Mix the target mineral precipitate obtained in S32 with ultrapure water at a solid-liquid ratio of 1:7, place it in an ultrasonic oscillation device, and perform dispersion treatment at a frequency of 30 kHz, a temperature of 5 °C, and an ultrasonic time of 15 minutes to form a homogeneous suspension.

[0026] S4 specifically includes: S41: Transfer the suspension obtained in S3 to the reaction kettle of a vacuum microwave digestion device, add a digestion solution containing 0.3 mol / L ammonium fluoride and 0.15 mol / L citric acid, and the solid-liquid ratio is 1:12. Pa, set the microwave power to 900 W, heat up to 200 °C, and the digestion time is 50 minutes. S43: After digestion is completed, cool to room temperature, open the reaction kettle to obtain a completely dissolved digestion solution.

[0027] S5 specifically includes: S51: Pre-activate the microfluidic chip filled with nano-titanium oxide, rinse it with 0.8 mol / L hydrochloric acid at a flow rate of 0.3 mL / min for 12 minutes to activate the adsorption surface. S52: Inject the digestion solution of S4 into the microfluidic chip at a flow rate of 0.2 mL / min, control the temperature in the chip to be 30 °C and the pH value to be 3.0, so that rare earth elements (REE) and thorium (Th) selectively bind to nano-titanium oxide. S53: After adsorption is completed, rinse the chip reversely with 0.15 mol / L oxalic acid solution at a flow rate of 0.3 mL / min to collect the purified digestion solution.

[0028] The series-connected resin columns in S6 include a DGA resin column and a TRU resin column.

[0029] S6 also includes: S61: Load the purified digestion solution of S5 onto the DGA resin column at a flow rate of 0.4 mL / min, so that uranium (U) and lead (Pb) isotopes are adsorbed onto the resin. S62: Elute the DGA resin column with 1 mol / L hydrochloric acid at a flow rate of 0.7 mL / min, and collect the eluate containing the target isotope; S63: Load the eluate from S63 onto the TRU resin column, and adsorb the residual thorium (Th) and rare earth elements (REE) at a flow rate of 0.3 mL / min; S64: Elute the TRU resin column with 0.5 mol / L hydrochloric acid at a flow rate of 0.4 mL / min to obtain a purified solution.

[0030] S7 specifically includes: S71: Transfer the purified solution obtained in S6 to a vacuum rotary evaporation device, set the water bath temperature to 55 °C, the vacuum degree to 0.09 MPa, and perform rotary evaporation at a rotation speed of 80 r / min until the solution volume is reduced to 1 / 12 of the original volume; S72: Filter the concentrated solution through a polyethersulfone (PES) filter membrane with a pore size of 0.22 μm at a flow rate of 1.5 mL / min to remove fine colloidal particles; S73: Collect the filtered solution to obtain a high-purity isotope solution.

[0031] S8 specifically includes: S81: Introduce the isotope solution concentrated in S7 into a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) at a flow rate of 0.3 mL / min, and set the radio frequency power to 1.3 kW, the carrier gas flow rate to 18 L / min, and the acquisition time to 65 seconds; S82: Measure the target isotope in the plasma mass spectrometer to obtain the initially measured isotope ratio data to be 0.8123; S83: Measure the reference material NIST SRM987 under the same measurement conditions to obtain the measured isotope ratio data of the reference material to be 0.7654, and at the same time, the theoretical isotope ratio of this reference material is known to be 0.7876; S84: Perform mass fractionation correction on according to the following correction formula to obtain the corrected isotope ratio data The formula is: Substitute the values into this formula: Therefore, the corrected isotope ratio is 0.8321.

[0032] Example 2 S1: First, place the rock mineral sample in a low-temperature plasma cleaner and clean it for 10 minutes under an argon atmosphere at a power of 200 W, a gas flow rate of 5 L / min, and a pressure of 50 Pa to remove surface organic contaminants. Subsequently, crush the cleaned sample into coarse particles with a particle size of 1 mm using a jaw crusher, and then transfer the coarse particles to a ball mill and grind them at a rotation speed of 200 rpm for 2 hours. Then, place the ground powder in a vibrating sieve shaker and screen it for 10 minutes using a sieve with a pore size of 50 μm to obtain powder with a uniform particle size. S2: Immerse the uniform powder obtained in S1 in a hydrofluoric acid-nitric acid mixed solution in two stages: In the first stage, immerse it in a mixed solution of 5% hydrofluoric acid and 3% nitric acid at 50 °C for 1 hour. In the second stage, immerse it in a mixed solution of 15% hydrofluoric acid and 5% nitric acid at 70 °C for 0.5 hour. Then, separate the residue after layered dissolution from the solution, add an etching solution containing 0.1 mol / L ammonium fluoride, and stir it at 40 °C at 200 rpm for 30 minutes. S3: Perform the first-stage centrifugation on the mixed solution treated in S2 with a centrifugal force of 500 g and a centrifugation time of 10 minutes. Then, perform the second-stage centrifugation on the supernatant obtained in S31 with a centrifugal force of 8000 g and a centrifugation time of 20 minutes to separate the target mineral precipitate. Mix the target mineral precipitate obtained in S32 with ultrapure water at a solid-liquid ratio of 1:5, place it in an ultrasonic oscillator, and perform dispersion treatment at a frequency of 20 kHz, a temperature of 4 °C, and an ultrasonic time of 10 minutes to form a uniform suspension. S4: Transfer the suspension obtained in S3 to the reaction kettle of a vacuum microwave digestion device, add a digestion solution containing 0.2 mol / L ammonium fluoride and 0.1 mol / L citric acid, and the solid-liquid ratio is 1:10. Then, seal the reaction kettle and evacuate it to a pressure of 10⁻³ Pa, set the microwave power to 800 W, heat it to 180 °C, and the digestion time is 30 minutes. After digestion is completed, cool it to room temperature to obtain a completely dissolved digestion solution. S5: Pre-activate the microfluidic chip filled with nano-titanium oxide, rinse it with 0.5 mol / L hydrochloric acid at a flow rate of 0.2 mL / min for 10 minutes to activate the adsorption surface. Then, inject the digestion solution of S4 into the microfluidic chip at a flow rate of 0.1 mL / min, control the temperature inside the chip to be 25 °C and the pH value to be 2.5, so that rare earth elements and thorium selectively bind to nano-titanium oxide. After adsorption is completed, rinse the chip in the reverse direction with 0.1 mol / L oxalic acid solution at a flow rate of 0.2 mL / min, and collect the purified digestion solution. S6: Load the digested solution purified in S5 onto a DGA resin column at a flow rate of 0.3 mL / min, allowing uranium and lead isotopes to adsorb onto the resin. Then, elute the DGA resin column with 0.8 mol / L hydrochloric acid at a flow rate of 0.5 mL / min. Next, load the eluate onto a TRU resin column and adsorb the residual thorium and rare earth elements at a flow rate of 0.2 mL / min. Then, elute the TRU resin column with 0.3 mol / L hydrochloric acid at a flow rate of 0.3 mL / min to obtain a purified solution. S7: Transfer the purified solution obtained in S6 to a vacuum rotary evaporation device. Set the water bath temperature to 50 °C, the vacuum degree to 0.08 MPa, and perform rotary evaporation at a rotation speed of 50 r / min until the solution volume is reduced to 1 / 10 of the original volume. Then, filter the concentrated solution through a polyethersulfone membrane with a pore size of 0.22 μm at a flow rate of 1 mL / min to remove fine colloidal particles. Finally, obtain a high-purity isotope solution. S8: Introduce the isotope solution concentrated in S7 into a multi-collector inductively coupled plasma mass spectrometer at a flow rate of 0.2 mL / min, and set the radio frequency power to 1.2 kW, the carrier gas flow rate to 15 L / min, and the acquisition time to 60 seconds. The initially measured isotope ratio is 0.7568; the initially measured isotope ratio of the reference material NIST SRM987 is 0.7104; the theoretical isotope ratio of the reference material NIST SRM987 is 0.7876. Then, substitute the values into the formula: Therefore, the corrected isotope ratio is 0.839.

[0033] Example 3 S1: First, place the rock mineral sample in a low-temperature plasma cleaner and clean it for 30 minutes under the conditions of an argon atmosphere, a power of 400 W, a gas flow rate of 10 L / min, and a pressure of 100 Pa to remove surface organic contaminants. Subsequently, crush the cleaned sample to coarse particles with a particle size of 3 mm using a jaw crusher, and then transfer the coarse particles to a ball mill and grind them at a rotation speed of 300 rpm for 4 hours. Next, place the ground powder in a vibrating sieve shaker and screen it for 20 minutes using a sieve with a pore size of 50 μm to obtain powder with a uniform particle size. S2: Immerse the uniform powder obtained in S1 in a hydrofluoric acid-nitric acid mixture in two stages: In the first stage, immerse it in a mixture of 10% hydrofluoric acid and 5% nitric acid at 70 °C for 2 hours; in the second stage, immerse it in a mixture of 20% hydrofluoric acid and 8% nitric acid at 90 °C for 1 hour. Then, separate the residue after layered dissolution from the solution, and add an etching solution containing 0.3 mol / L ammonium fluoride and stir it at 60 °C at 300 rpm for 60 minutes. S3: Perform primary centrifugation on the mixed solution processed in S2, with a centrifugal force of 1000 g and a centrifugation time of 15 minutes. Then, perform secondary centrifugation on the supernatant obtained in S31, with a centrifugal force of 12000 g and a centrifugation time of 30 minutes to separate the target mineral precipitate. Mix the target mineral precipitate obtained in S32 with ultrapure water at a solid-liquid ratio of 1:10, place it in an ultrasonic oscillation device, and perform dispersion treatment at a frequency of 40 kHz, a temperature of 10 °C, and an ultrasonic time of 20 minutes to form a homogeneous suspension. S4: Transfer the suspension obtained in S3 to the reaction kettle of a vacuum microwave digestion device, add a digestion solution containing 0.5 mol / L ammonium fluoride and 0.2 mol / L citric acid, with a solid-liquid ratio of 1:15. Then, seal the reaction kettle and evacuate it to a pressure of 10⁻³ Pa, set the microwave power to 1000 W, heat up to 220 °C, and the digestion time is 60 minutes. After digestion is completed, cool it to room temperature to obtain a completely dissolved digestion solution. S5: Pre-activate the microfluidic chip filled with nano-titanium oxide, rinse it with 1 mol / L hydrochloric acid at a flow rate of 0.5 mL / min for 15 minutes to activate the adsorption surface. Then, inject the digestion solution of S4 into the microfluidic chip at a flow rate of 0.3 mL / min, control the temperature inside the chip to be 40 °C and the pH value to be 3.5, so that rare earth elements and thorium selectively bind to nano-titanium oxide. After adsorption is completed, rinse the chip in the reverse direction with 0.2 mol / L oxalic acid solution at a flow rate of 0.4 mL / min to collect the purified digestion solution. S6: Load the purified digestion solution of S5 onto a DGA resin column at a flow rate of 0.6 mL / min, so that uranium and lead isotopes are adsorbed onto the resin. Then, elute the DGA resin column with 1.2 mol / L hydrochloric acid at a flow rate of 1.0 mL / min. Next, load the eluate onto a TRU resin column and adsorb the residual thorium and rare earth elements at a flow rate of 0.4 mL / min. Then, elute the TRU resin column with 0.8 mol / L hydrochloric acid at a flow rate of 0.5 mL / min to obtain a purified solution. S7: Transfer the purified solution obtained in S6 to a vacuum rotary evaporation device, set the water bath temperature to 60 °C, the vacuum degree to 0.1 MPa, and perform rotary evaporation at a rotation speed of 100 r / min until the solution volume is reduced to 1 / 15 of the original volume. Then, filter the concentrated solution through a polyethersulfone filter membrane with a pore size of 0.22 μm at a flow rate of 2 mL / min to remove fine colloidal particles. Finally, obtain a high-purity isotope solution. S8: Import the isotope solution concentrated in S7 into a multi-collector inductively coupled plasma mass spectrometer at a flow rate of 0.5 mL / min, and set the radio frequency power to 1.5 kW, the carrier gas flow rate to 20 L / min, and the acquisition time to 75 seconds. The initially measured isotope ratio was 1.0456; the initially measured isotope ratio of the reference material NIST SRM 987 was 1.0103; the theoretical isotope ratio of the reference material NIST SRM 987 was 0.7876; then, substitute the values into the formula: Therefore, the corrected isotope ratio was 0.8151.

[0034] Table 1 Comparison of the efficiencies of each example As can be seen from Table 1 above, the extraction rate of Example 1 was 98%, significantly higher than that of Example 2 (95%) and Example 3 (92%); the sample purity of Example 1 was 99%, showing that it had the best effect during the purification process. In contrast, the sample purities of Example 2 and Example 3 were lower; Example 1 had the smallest error (0.2%), indicating that it had the highest accuracy when measuring the isotope ratio, and the errors of Example 2 and Example 3 were larger; the target isotope concentration of Example 3 was the highest (0.38 ng / mL), but the concentration of Example 1 (0.35 ng / mL) still performed well, far exceeding that of Example 2 at 0.32 ng / mL. Therefore, in terms of accuracy and performance, Example 1 performed best in most comparison items, proving that it was the optimal choice.

[0035] Table 2 Comparison of the performances in other aspects As can be seen from Table 2 above, the processing time of Example 2 was the shortest (8 hours), while that of Example 1 was 10 hours and that of Example 3 was 12 hours, showing that Example 2 was superior in terms of processing speed; the sample loss rate of Example 1 was the lowest (2%), indicating that it wasted less sample during the operation, while those of Example 2 (3%) and Example 3 (4%) were slightly higher; the operation simplicity score of Example 1 was the highest (9 points), indicating that its operation process was the simplest and easiest to perform. In contrast, the scores of Example 2 and Example 3 were lower; the experimental equipment utilization efficiency of Example 1 was the highest (95%), reflecting its efficient use of equipment during the experiment. In contrast, those of Example 2 (90%) and Example 3 (92%) were slightly inferior; the operation complexity of Example 1 was the lowest (3 points), meaning that its operation steps were relatively simple; while the operation complexities of Example 2 and Example 3 were higher. Therefore, although Example 2 was more efficient in terms of time, in terms of overall efficiency and operation convenience, Example 1 was still the best choice.

[0036] The present invention encompasses any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention. To enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention. However, those skilled in the art can fully understand the present invention even without these detailed descriptions. Additionally, well-known methods, processes, procedures, components, and circuits are not described in detail to avoid unnecessary confusion to the essence of the present invention.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for isotope analysis of refractory rock minerals based on pretreatment and purification, characterized in that: The following steps are involved: S1: Clean the surface of the rock mineral sample to remove the attached organic pollutants, and mechanically crush and sieve the cleaned sample to obtain powder with uniform particle size; S2: The uniform powder obtained in S1 is sequentially immersed in a hydrofluoric acid-nitric acid mixture with increasing concentrations for dissolution in layers, and then an etching solution is added to remove impurities remaining in the dissolution process; S3: subjecting the mixed solution treated in S2 to two-stage centrifugation to separate the target mineral precipitate; The precipitate is placed in an ultrasonic oscillation device for dispersion treatment to form a uniform suspension; S4: transferring the suspension of S3 to a vacuum microwave digestion container, and adding a digestion solution for vacuum microwave digestion to completely dissolve the target mineral to obtain a digestion solution; S5: The digestion solution of S4 is subjected to dynamic adsorption treatment through a microfluidic chip filled with nano-titanium oxide to preliminarily purify the digestion solution; S6: using a series of resin columns to selectively adsorb and elute the target isotope in the digestion solution purified by S5 to obtain a purified solution; S7: placing the purified solution obtained in S6 in a vacuum rotary evaporator, reducing the volume of the solution by concentration treatment, and filtering through a filter membrane to remove fine colloidal particles to obtain an isotope solution; S8: The isotope solution concentrated in S7 is measured by a mass spectrometer, and the measured data is mass fractionated and corrected in combination with standard substances, and the target isotope ratio data is finally output.

2. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S1 specifically includes: S11: Place the rock mineral sample in a low-temperature plasma cleaning instrument and clean it for 10-30 minutes under an argon atmosphere at a power of 200-400 W, a gas flow rate of 5-10 L / min, and a pressure of 50-100 Pa to remove surface organic pollutants; S12: crushing the cleaned sample into coarse particles with a particle size of 1-3 mm by a jaw crusher; S13: transferring the coarse particles to a ball mill and grinding at 200-300 rpm for 2-4 hours; S14: The ground powder is placed in a vibrating sieving device and sieved using a sieve with a pore size of 50 μm for 10-20 minutes to obtain a powder with a uniform particle size.

3. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S2 specifically includes: S21: The uniform powder obtained in S1 is immersed in a hydrofluoric acid-nitric acid mixture in two stages: The first stage: immerse in a mixture of 5-10% hydrofluoric acid and 3-5% nitric acid at 50-70°C for 1-2 hours to dissolve feldspar and mica paragenetic minerals; The second stage: immerse in a mixture of 15-20% hydrofluoric acid and 5-8% nitric acid at 70-90°C for 0.5-1 hour to dissolve the remaining ilmenite and amphibole; S22: separating the residue after layered dissolution from the solution, adding an etching solution containing 0.1-0.3 mol / L ammonium fluoride, stirring at 200-300 rpm for 30-60 minutes at 40-60° C., and directionally removing the residual apatite and quartz particles.

4. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S3 specifically includes: S31: subjecting the mixed solution treated in S2 to a first-stage centrifugal treatment, with a centrifugal force of 500-1000 g and a centrifugal time of 10-15 minutes, to remove undissolved large particle impurities and retain the supernatant containing the target mineral; S32: subjecting the supernatant obtained in S31 to a second-stage centrifugation treatment, with a centrifugal force of 8000-12000 g and a centrifugal time of 20-30 minutes, to separate and obtain a target mineral precipitate; S33: The target mineral precipitate obtained in S32 is mixed with ultrapure water at a solid-liquid ratio of 1:5-1:10, placed in an ultrasonic oscillation device, and dispersed at a frequency of 20-40 kHz, a temperature of 4-10°C, and an ultrasonic time of 10-20 minutes to form a uniform suspension.

5. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S4 specifically includes: S41: transferring the suspension obtained in S3 to a reactor of a vacuum microwave digestion device, adding a digestion solution containing 0.2-0.5 mol / L ammonium fluoride and 0.1-0.2 mol / L citric acid, with a solid-liquid ratio of 1:10-1:15; S42: Seal the reactor and evacuate to a pressure of 10 -3 Pa, set the microwave power to 800-1000W, raise the temperature to 180-220℃, and the digestion time to 30-60 minutes; S43: After the digestion is completed, the mixture is cooled to room temperature, and the reactor is opened to obtain a completely dissolved digestion solution.

6. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S5 specifically includes: S51: pre-activating the microfluidic chip filled with nano-titanium oxide by flushing it with 0.5-1.0 mol / L hydrochloric acid at a flow rate of 0.2-0.5 mL / min for 10-15 minutes to activate the adsorption surface; S52: injecting the digestion solution of S4 into the microfluidic chip at a flow rate of 0.1-0.3 mL / min, controlling the temperature in the chip to 25-40° C. and the pH value to 2.5-3.5, so that the rare earth elements and thorium are selectively combined with the nano-titanium oxide; S53: After the adsorption is completed, the chip is backwashed with 0.1-0.2 mol / L oxalic acid solution at a flow rate of 0.2-0.4 mL / min, and the purified digestion solution is collected.

7. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The series-connected resin columns in S6 include a DGA resin column and a TRU resin column.

8. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S6 further includes: S61: The digestion solution purified by S5 is loaded into the DGA resin column at a flow rate of 0.3-0.6 mL / min, so that the uranium and lead isotopes are adsorbed on the resin; S62: Elute the DGA resin column with 0.8-1.2 mol / L hydrochloric acid at a flow rate of 0.5-1.0 mL / min, and collect the eluate containing the target isotope; S63: Load the S63 eluate onto a TRU resin column to adsorb residual thorium and rare earth elements at a flow rate of 0.2-0.4 mL / min; S64: Elute the TRU resin column with 0.3-0.8 mol / L hydrochloric acid at a flow rate of 0.3-0.5 mL / min to obtain a purified solution.

9. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S7 specifically includes: S71: Transfer the purified solution obtained in S6 to a vacuum rotary evaporator, set the water bath temperature to 50-60°C, the vacuum degree to 0.08-0.1 MPa, and perform rotary evaporation at a speed of 50-100 r / min until the volume of the solution is reduced to 1 / 10-1 / 15 of the original volume; S72: filtering the concentrated solution through a polyethersulfone filter membrane with a pore size of 0.22 μm at a flow rate of 1-2 mL / min to remove fine colloidal particles; S73: Collect the filtered solution to obtain a high-purity isotope solution.

10. The isotope analysis method of refractory rock minerals based on pretreatment and purification according to claim 1, characterized in that: The S8 specifically includes: S81: The concentrated isotope solution of S7 is introduced into a multi-collector inductively coupled plasma mass spectrometer at a flow rate of 0.2-0.5 mL / min, and the RF power is set to 1.2-1.5 kW, the carrier gas flow rate is 15-20 L / min, and the acquisition time is 60-75 seconds; S82: Measure the target isotope in the plasma mass spectrometer to obtain preliminary isotope ratio data, recorded as ; S83: The standard material NISTSRM987 is measured under the same measurement conditions to obtain the measured isotope ratio data of the standard material, which is recorded as , and the theoretical isotope ratio of the standard substance is known to be ; S84: According to the following correction formula Perform mass fractionation correction to obtain corrected isotope ratio data , the formula is: .

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