A pretreatment method for purifying Mg in highly fractionated granite

Abstract

The present invention discloses a pretreatment method for purifying Mg in highly fractionated granite, belonging to the technical field of Mg isotope. It solves the problems of low efficiency of the pretreatment method for Mg isotope in the prior art and inaccurate MC-ICPMS test results caused by matrix effect. The pretreatment method of the present invention includes: completely dissolving the rock sample; mixing the dissolved supernatant with NaOH solution and heating for reaction to obtain a co-precipitation supernatant; performing column chromatography with two washes on the co-precipitation supernatant. The composition of the first eluent includes HNO3 and HF, the molar concentration of HNO3 is 1.99 - 2.01M, the molar concentration of HF is 0.1 - 2M, and the composition of the second eluent includes HNO3, and the molar concentration of HNO3 is 0.94 - 0.96M. The present invention can be used for the pretreatment of purifying Mg in highly fractionated granite.

Description

Technical Field

[0001] The present invention relates to the field of chemical analysis technology, in particular to the field of Mg isotope technology. Specifically, the present invention relates to a pre-treatment method for purifying Mg in highly fractionated granite. Background Art

[0002] Highly fractionated granite is a rock with high aluminum, rich alkali, high potassium, low calcium, rich silicon and a small amount of iron and magnesium. The existing pre-treatment analysis methods for purifying Mg in rocks with low MgO content are mainly chromatography column method and co-precipitation method combined with chromatography column method.

[0003] The Mg isotope analysis method is inefficient when dealing with rocks with low MgO content, and the matrix elements are difficult to separate effectively. The presence of K, Ti and Mn will bring about a matrix effect, resulting in inaccurate test results of Mg isotope composition. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a pretreatment method for purifying Mg in highly fractionated granite, so as to solve the problems of low efficiency of the pretreatment method of Mg isotope in the prior art and inaccurate MC-ICPMS test results due to matrix effect.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions.

[0006] The present invention provides a pretreatment method for purifying Mg in highly fractionated granite, comprising the following steps:

[0007] Step 1: providing a rock sample to be tested, dissolving the rock sample completely to obtain a dissolved supernatant;

[0008] Step 2: Mix the dissolved supernatant with the NaOH solution and heat to react, so that Mg is converted into Mg(OH) 2 Precipitation, completing one coprecipitation, and obtaining a coprecipitation supernatant;

[0009] Step 3: The coprecipitation supernatant was subjected to column chromatography with two washes, one of which consisted of HNO 3 and HF, HNO 3 The molar concentration of HF is 1.99-2.01 M, the molar concentration of HF is 0.1-2 M, and the composition of the secondary eluent includes HNO 3 , HNO 3 The molar concentration is 0.94~0.96M.

[0010] Furthermore, HNO 3 The molar concentration of is 2M, and the molar concentration of HF is 0.5M.

[0011] Furthermore, HNO 3 The molar concentration is 0.95M.

[0012] Furthermore, step 1 includes the following steps:

[0013] Step 11: Weigh the rock powder sample, the mass of Mg in the rock powder sample is 20-100 μg;

[0014] Step 12: adding the first mixed acid to the rock powder sample, heating, standing and then evaporating to dryness;

[0015] Step 13: adding the second mixed acid to the solid obtained after evaporation in step 12, heating, standing and then evaporating to dryness;

[0016] Step 14: Add concentrated HNO to the solid obtained after evaporation in step 13 3 Then evaporate to dryness;

[0017] Step 15: Add HNO to the solid obtained after evaporation in step 14 3 Centrifuge to obtain the dissolved supernatant.

[0018] Furthermore, the first mixed acid comprises concentrated HF and concentrated HNO 3 , concentrated HF and concentrated HNO 3 The volume ratio is 3:1 to 2:1.

[0019] Furthermore, the amount of the first mixed acid is as follows: 10 mg of rock powder sample corresponding to concentrated HNO 3 The amount added is 1 ml.

[0020] Further, the second mixed acid comprises concentrated HCl and concentrated HNO 3 , concentrated HCl and concentrated HNO 3 The volume ratio is 3:1.

[0021] Furthermore, the amount of the second mixed acid is as follows: 10 mg of rock powder sample corresponding to concentrated HNO 3 The amount added is 1 ml.

[0022] Furthermore, step 2 includes the following steps:

[0023] Step 21: Add NaOH solution to the dissolved supernatant and heat it;

[0024] Step 22: centrifuging the mixed solution obtained in step 21 to obtain a first precipitate;

[0025] Step 23: adding water to the first precipitate, mixing and heating;

[0026] Step 24: centrifuging the mixed solution obtained in step 23 to obtain a second precipitate;

[0027] Step 25: Add concentrated HNO to the second precipitate 3 Heat until the second precipitate is completely dissolved and then evaporate to dryness;

[0028] Step 26: Add mixed acid to the solid obtained after evaporation in step 25, and centrifuge to obtain a coprecipitation supernatant.

[0029] Furthermore, in step 21, 1 to 2 ml of a 3.5 M NaOH solution is added to the dissolved supernatant.

[0030] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects.

[0031] A) The pretreatment method for purifying Mg in highly fractionated granite provided by the present invention combines a coprecipitation method and a chromatography column method to remove most of the matrix elements in the sample, such as Na, Al, K, Ca, Fe, Li, Zn, Rb, Sr, Cs, Ba, Pb, Th and U, while maintaining a high recovery rate of Mg (96-99%). By optimizing the elution step, 1.99-2.01MHNO 3 +0.1~2M HF mixed acid and 0.94~0.96M HNO 3 , effectively separating Mg from elements such as Ti and Mn. Specifically, 1.99-2.01M HNO 3 The eluent can effectively remove most of the matrix elements, but the leaching period of the matrix elements K and Ti still overlaps with Mg. The addition of 0.1-2M HF not only promotes the early leaching of Ti, but also shortens their leaching time, thus achieving effective separation of Ti and Mg. 0.94-0.96M HNO 3 The eluent can effectively distinguish the elution intervals of Mg and Mn, thereby achieving effective separation of Mg and Mn. Experimental results show that this pretreatment method is suitable for highly differentiated granites with MgO content as low as 0.04wt.% and peridotite with MgO content as high as 49.5wt.%, and the matrix effect is effectively controlled, improving the matrix effect in the multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS) test, and the recovery rate of Mg can reach 96-99%.

[0032] B) The pretreatment method for purifying Mg in highly fractionated granite provided by the present invention can significantly improve the treatment efficiency of samples with low MgO content by combining a coprecipitation method with a chromatography column method, and reduce the cost of a large amount of eluent and long treatment time that may be required by traditional methods.

[0033] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the embodiments of the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0035] Figure 1 This is the Mg isotope elution curve of rhyolite (JR1) in Example 1 of the present invention, and the sampling interval of Mg is 10-34 ml;

[0036] Figure 2 This is the Mg isotope elution curve of basalt (BHVO-2) in Example 1 of the present invention, and the sampling interval of Mg is 10-34 ml;

[0037] Figure 3 This is a comparison chart of the Mg isotope compositions of rock standards, mixed solutions and single standards with values ​​reported in literature from high MgO (49.5wt.%) to low MgO (0.04wt.%) content in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0039] The present invention provides a pretreatment method for purifying Mg in highly fractionated granite, which adopts a one-time coprecipitation method combined with a one-column method, and can purify highly fractionated granite with a MgO content as low as 0.04wt.% and peridotite with a MgO content as high as 49.5wt.%.

[0040] The pre-treatment method comprises the following steps:

[0041] Step 1: providing a rock sample, which is a purified highly fractionated granite sample, and dissolving the rock sample completely to obtain a dissolved supernatant;

[0042] Step 2: Mix the dissolved supernatant with the NaOH solution and heat to react, so that Mg is converted into Mg(OH) 2 Precipitation, removing almost all of the Al, K, Li, Zn, Rb, Sr, Cs, Ba, Pb, Th and U elements and part of the Na, Ti, Ca, Fe and Mn elements, completing one coprecipitation, and obtaining a coprecipitation supernatant;

[0043] Step 3: The coprecipitation supernatant was subjected to column chromatography with two washes to remove matrix elements, including Na, Ti, Fe, and Mn, and one column chromatography was completed, wherein the composition of one wash solution included HNO 3 and HF, HNO 3 The molar concentration of is 1.99 to 2.01 M (e.g., 2 M), the molar concentration of HF is 0.1 to 2 M (e.g., 0.5 M), and the composition of the secondary eluent includes HNO 3 , HNO 3 The molar concentration is 0.94 to 0.96 M (eg, 0.95 M).

[0044] Compared with the prior art, the pretreatment method for purifying Mg in highly fractionated granite provided by the present invention combines a coprecipitation method and a chromatography column method to remove most of the matrix elements in the sample, such as Al, K, Ti, Fe, Mn, Ca, Li, Zn, Rb, Sr, Cs, Ba, Pb, Th and U elements, while maintaining a high recovery rate of Mg (96-99%). By optimizing the elution step, 1.99-2.01M HNO 3 +0.1~2M HF mixed acid and 0.94~0.96M HNO 3 , effectively separating Mg from elements such as Ti and Mn. Specifically, 1.99-2.01M HNO 3 The eluent can effectively remove most of the matrix elements, but the leaching period of the matrix elements K and Ti still overlaps with Mg. The addition of 0.1-2M HF not only promotes the early leaching of Ti, but also shortens their leaching time, thus achieving effective separation of Ti and Mg. 0.94-0.96M HNO 3 The eluent can effectively distinguish the elution intervals of Mg and Mn, thereby achieving effective separation of Mg and Mn. Experimental results show that this pretreatment method is suitable for highly differentiated granites with MgO content as low as 0.04wt.% and peridotite with MgO content as high as 49.5wt.%, and the matrix effect is effectively controlled, improving the matrix effect in the multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS) test, and the recovery rate of Mg can reach 96-99%.

[0045] In addition, the above-mentioned pretreatment method can significantly improve the processing efficiency of low MgO content samples by combining one co-precipitation method with one chromatography column method, and reduce the cost of a large amount of eluent and long processing time that may be required by traditional methods.

[0046] Exemplarily, in order to improve the dissolution effect and achieve complete dissolution of the sample, the above step 1 includes the following steps:

[0047] Step 11: Weigh the rock powder sample and place it in a 7-15 ml beaker (Beaker made of PFA Teflon material). The mass of Mg in the rock powder sample is 20-100 μg.

[0048] Step 12: Add a first mixed acid to the rock powder sample, the first mixed acid comprising concentrated HF and concentrated HNO 3 , concentrated HF and concentrated HNO 3 The volume ratio of the first mixed acid is 3:1 to 2:1. The amount of the first mixed acid is as follows: 10 mg of rock powder sample corresponds to concentrated HNO 3 Add 1 ml, cover tightly and place on a hot plate at 120-130°C overnight (>12h), then evaporate to dryness on a hot plate at 100°C;

[0049] It should be noted that the method of adding the mixed acid is as follows: first add HNO 3 HF was then added to prevent CaF 2 Precipitation. HF is used to break the Si-O bond and generate volatile SiF 4 , while HNO 3 Provides an oxidizing environment.

[0050] Step 13: Add a second mixed acid to the solid obtained after evaporation in step 12, wherein the second mixed acid comprises concentrated HCl and concentrated HNO 3 , concentrated HCl and concentrated HNO 3 The volume ratio of aqua regia is 3:1, and the amount of the second mixed acid is as follows: 10 mg of rock powder sample corresponds to concentrated HNO 3 The amount of addition is 1 ml, cover tightly and let stand on a hot plate at 120-130℃ overnight (>12h), then evaporate to dryness at 100℃ on the hot plate. The purpose of adding aqua regia is to dissolve insoluble oxides such as ilmenite, chromite and spinel.

[0051] Step 14: Add 0.5-1 ml of concentrated HNO to the solid obtained after evaporation in step 13. 3 , and then evaporated to dryness on a hot plate at 100°C. This process is called "acid rushing" and its purpose is to promote the reaction of the remaining fluoride ions (F-) and chloride ions (Cl-) in the sample with the newly added hydrogen ions (H + ) to form volatile HCl and HF. If these ions are not completely removed, HF, HCl and HNO will be formed during the subsequent column separation (passing the column). 3 The mixed acid environment was originally based on HNO 3 The equilibrium calculation of the environment will be disrupted. This will lead to uncertain element leaching times and may cause experimental failure. Therefore, it is critical to ensure that F- and Cl- are adequately removed at the beginning of the step.

[0052] Step 15: Add 2% HNO3 After constant volume, centrifugation was performed to obtain the dissolved supernatant, the volume of which was 20 μg Mg corresponding to 1 ml 2% HNO 3 .

[0053] For step 2, it includes the following steps:

[0054] Step 21: Take 1 ml of the dissolved supernatant and add it to a 7 ml centrifuge tube. Add 1-2 ml of 3.5 M NaOH solution and heat it on a hot plate at 60-80°C for 30-60 min. The addition of excess NaOH solution can ensure that the Mg in the dissolved supernatant is completely converted to Mg(OH) 2 Some Fe, Ca and Ti precipitate in the form of Fe(OH) 3 , Ca(OH) 2 and Ti(OH) 4 Since MnO 2 It is difficult to dissolve in NaOH solution, so Mn is mainly in the form of MnO 2 Due to Al(OH) 3 It will react with excess NaOH to generate Al 2 Na 2 O 4 solution, resulting in the initial Al(OH) 3 Al precipitated in the form of AlO 2 - Ionic form dissolves in NaOH solution. Since Pb(OH) 2 Reacts with excess NaOH to generate Na 2 [Pb(OH) 4 ] solution, resulting in the initial formation of Pb(OH) 2 The Pb precipitated in the form of [Pb(OH) 4 ] 2- They dissolve in NaOH solution in the form of ions. K, Li, Rb, Cs and Ba are dissolved in the form of K + , Li + , Rb + , Cs + and Ba 2+ The plasma form is present in the lysis supernatant;

[0055] Step 22: Centrifuge the mixture obtained in step 21 to remove K + 、Na + , Li + , Rb + , Cs + 、[Pb(OH) 4 ] 2- 、AlO 2- The supernatant of the plasma is used to obtain the first precipitate. This step can remove 100% of Li, Rb, Cs, Pb, Th, U, 98.0% of Ba, 96.9% of Zn, 96.6% of Sr, 95.9% of K, 94.8% of Al, 19.2% of Fe, 11.3% of Ca, 8.2% of Ti, 7.3% of Mn, and bring 334% of Na, while 97.2% of Mg is completely retained in the first precipitate;

[0056] Step 23: Add 4-5 ml of water (e.g., ultrapure water, MQ water) to the first precipitate, shake to fully mix the first precipitate with the water, and heat on a hot plate at 60-80° C. for 30-60 min to make the Al(OH) 3 、Fe(OH) 3 , Ca(OH) 2 、Ti(OH) 4 、MnO 2 Or Na adsorbed in the first precipitate + , K + and Ba 2 The plasma further dissolved into the supernatant.

[0057] Step 24: Centrifuge the mixed solution obtained in step 23 to remove the Na-rich + , K + , Ba 2+ This step can remove 406% of Na, 4.4% of Al, 3.9% of K, 53.9% of Ca, 8.2% of Ti, 5.8% of Mn, 6.4% of Fe, 2.3% of Sr, 0.7% of Ba, etc. in the precipitate or adsorbed in the second precipitate, while 95.7% of Mg is retained in the second precipitate.

[0058] After two centrifugations, a total of 100% of Li, Rb, Cs, Pb, Th, and U were removed, 99.8% of K, 99.2% of Al, 98.9% of Sr, 98.7% of Ba, 96.9% of Zn, 72.5% of Na, 65.2% of Ca, 25.6% of Fe, 16.4% of Ti, and 13.1% of Mn, and 95.7% of Mg was retained in the second precipitate.

[0059] Step 25: Add 0.5-1 ml of concentrated HNO to the second precipitate 3 , heat at 60-80℃ on a hot plate for 30-60min, wait until the second precipitate is completely dissolved, transfer to a 7ml or 15ml beaker (PFA Teflon Beaker), open the lid, and evaporate to dryness at 100℃ on a hot plate;

[0060] Step 26: In 1 ml 2M HNO 3 The mixture was fixed to volume with a mixed acid of +0.5 M HF and then centrifuged to obtain the coprecipitation supernatant.

[0061] For step 3, it includes the following steps:

[0062] Step 31: 2 ml of AG50W-X12 (200-400 mesh) cation exchange resin was filled into a PFA Teflon column (6.4 mm ID*6.2 cm height, 30 ml capacity, short column);

[0063] Step 32: Use 10-15 ml MQ water and 5-10 ml 6M HNO in sequence. 3 Eluting cation exchange resin;

[0064] Step 33: Use 5-10 ml 2M HNO 3 +0.5M HF mixed acid balanced cation exchange resin;

[0065] Step 34: Take 1 ml of sample and load it;

[0066] Step 35: Use 7 ml 1.99-2.01 M HNO 3 The cation exchange resin is eluted with a mixed acid of 0.1-2M HF to remove elements such as K, Na, Al, Ti, and Fe. Select 1.99-2.01M HNO 3 Instead of 1M HNO 3 , in order to improve the separation efficiency. Using 1M HNO 3 For the eluent, Mg will elute in the 28-44 ml interval; and for 1.99-2.01 M HNO 3 The eluent can elute Mg in the range of 8 to 16 ml. 3 The eluent can effectively remove most of the matrix elements, but the leaching period of the matrix elements K and Ti still overlaps with Mg. By adding 0.1-2M HF, K and Ti are leached out earlier on the one hand, and their leaching time is shortened on the other hand, thus achieving effective separation of K and Ti from Mg.

[0067] Step 36: Use 2 ml of 0.94-0.96 M HNO 3 The cation exchange resin is eluted to significantly distinguish the elution intervals of Mg from those of Na, Al, Ti, and Fe to prevent the matrix effect caused by tailing of these elements. Although a concentration lower than 0.94M can improve the separation effect, the efficiency will be reduced. Although a concentration higher than 0.96M can improve the separation efficiency, it may cause the elution areas of Na, Al, Ti, Fe and Mg to be close or overlapped, causing a matrix effect.

[0068] Step 37: Use 22-24 ml of 0.94-0.96 M (e.g., 0.95 M) HNO 3 Receive Mg. Make the elution intervals of Mg and Mn elements significantly different to prevent the matrix effect caused by Mn element. Although the concentration below 0.94M can improve the separation effect, the efficiency will be reduced. If the concentration is higher than 0.96M, although the efficiency is improved, the elution areas of Mg and Mn will overlap, causing the matrix effect. HNO 3 If the volume is less than 22 ml, Mg is not completely absorbed, resulting in a decrease in Mg recovery. If the volume exceeds 24 ml, some Mn will be introduced, which will also cause a matrix effect.

[0069] The pre-treatment method of the present invention is described in detail below in conjunction with the embodiments:

[0070] Example 1

[0071] The specific parameters of the pre-treatment method of this embodiment are shown in Table 1.

[0072] The pre-treatment method of this embodiment is used to process the peridotite standard sample, basalt standard sample, andesite standard sample, granodiorite standard sample, rhyolite standard sample and the configured sample, see Figure 1 to Figure 2 , among which, the MgO content of peridotite standard sample (DTS-2) is 49.5wt.%, the MgO content of basalt standard sample (BHVO-2) is 7.26wt.%, the MgO content of andesite standard sample (AGV-2) is 1.79wt.%, the MgO content of granodiorite standard sample (GSP-2) is 0.91wt.%, and the MgO content of rhyolite standard samples (JR-1 and JR-2) is 0.12wt.% and 0.04wt.%, respectively. The MgO content of these rock standards ranges from 0.04wt.% to 49.5wt.%.

[0073] The Mg isotopes of the six rock standards that underwent the above pretreatment were tested using Nu Sapphire MC-ICPMS. The mass fractionation of the instrument was calibrated using the “standard-sample” interpolation method. The Mg isotope ratios were finally normalized to the international standard DSM3. The test results are expressed as δ 26,25 Mg(‰)=[( 26,25 Mg / 24 Mg) sample / ( 26,25 Mg / 24 Mg) DSM3 )-1]×1000, where ( 26,25 Mg / 24 Mg) sample For samples 26,25 Mg / 24The measured value of Mg ratio, ( 26,25 Mg / 24 Mg) DSM3 Two standard samples adjacent to the sample 26,25 Mg / 24 The Mg ratio determinations are averaged. Two internal standards (ERM143 Mg and Alfa Mg solution) are analyzed with each batch of samples to monitor accuracy and reproducibility. 26,25 Mg / 24 The long-term external precision of the Mg ratio was better than ±0.06‰ (2SD).

[0074] The geochemistry of rhyolite is similar to that of highly fractionated granite, usually with high SiO 2 content (>70wt.%), lower MgO content (mostly <0.2wt.%) and higher matrix element content. Therefore, the difficulty of purifying Mg in rhyolite is comparable to that of purifying Mg in highly fractionated granite. 26 Mg is -0.28~-0.19‰. The test results of this embodiment show that the δ 26 Mg is -0.27±0.01‰, which is consistent with previously published data within the error range.

[0075] Since the MgO content of the rhyolite standard JR-2 is lower (0.04wt.%), it is more difficult to purify Mg, resulting in no report on its Mg isotope composition. 26 Mg is -0.29±0.04‰.

[0076] At the same time, this example also measured the Mg isotope compositions of the other four rock standards: the δ 26 Mg is -0.06±0.01‰, and the δ 26 Mg is -0.16±0.01‰, and the δ 26 Mg is -0.28±0.03‰ and δ 26 Mg is -0.29±0.02‰. These data are consistent with previously published data within the error range ( Figure 3 ).

[0077] In addition, the sample was prepared as a mixed solution consisting of a single element Mg standard solution and a matrix element. The mass ratio of the elements in the mixed solution was Al:Ca:Fe:K:Mn:Na:Ti:Mn=19.4:1.37:1.77:10.46:0.22:8.51:0.19:0.20. The results of the two MC-ICPMS tests showed that the δ 26 Mg is -1.45±0.05‰ and -1.47±0.05‰. The MC-ICPMS test results show that the δ 26 Mg is -1.42±0.05‰. The three test results are consistent within the error range ( Figure 3 ).

[0078] For specific test results and literature reported values, see Figure 3 .

[0079] Comparative Example 1

[0080] The coprecipitation method combined with the chromatography column method was used. The specific parameters are shown in Tables 1 and 2, including the two-time coprecipitation method and the two-time chromatography column method. The two-time coprecipitation method: First, 1 ml of the sample was dissolved in a 2 ml centrifuge tube, 1 ml of 4 M NaOH was added, and the Mg(OH) was formed by ultrasonication for 15 minutes. 2 Precipitation. After centrifugation for 15 minutes, discard the supernatant (rich in K) and keep the precipitate. Repeat this process to further remove K. Then, convert the precipitate into HCl medium with 1 ml of concentrated HCl, centrifuge and take the supernatant for later use. Secondary chromatography column method: first use AG50W-X12 resin (eluted with 12M HCl), then use AG50W-X8 resin (eluted with 6M HCl) to purify the Mg solution.

[0081] The pretreatment method of Comparative Example 1 has the following problems: 1) The recovery rate of Mg is not high, which is 80-90%; 2) NaOH is added twice, which not only fails to remove the Na in the sample itself, but also greatly increases the introduction of the matrix element Na; 3) The removal rate of the matrix elements Ca, Sr, Ba and Th is low; 4) The subsequent chromatography column method is time-consuming (1 to 2 days), and the matrix effect problem of Mn is not solved, and it is only applicable to samples with MgO>0.28wt.%.

[0082] Table 1 Parameters of the pretreatment method of the present invention and comparative example 1

[0083]

[0084]

[0085] Table 2 Comparison results of the pre-treatment methods of Example 1 of the present invention and Comparative Example 1

[0086]

[0087] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A pretreatment method for purifying Mg in highly fractionated granite, characterized in that: The steps include: Step 1: providing a rock sample, and dissolving the rock sample completely to obtain a dissolved supernatant; Step 2: Mix the dissolved supernatant with the NaOH solution and heat to react, so that Mg is converted into Mg(OH)2 precipitation, completing one coprecipitation to obtain a coprecipitation supernatant; Step 3: performing column chromatography on the coprecipitation supernatant twice, wherein the composition of the first eluent includes HNO3 and HF, the molar concentration of HNO3 is 1.99-2.01M, the molar concentration of HF is 0.1-2M, and the composition of the second eluent includes HNO3, and the molar concentration of HNO3 is 0.94-0.96M; The step 1 comprises the following steps: Step 11: Weigh the rock powder sample, the mass of Mg in the rock powder sample is 20-100 μg; Step 12: adding the first mixed acid to the rock powder sample, heating, standing and then evaporating to dryness; Step 13: adding the second mixed acid to the solid obtained after evaporation in step 12, heating, standing and then evaporating to dryness; Step 14: Add concentrated HNO3 to the solid obtained after evaporation in step 13 and evaporate to dryness; Step 15: adding HNO3 to the solid obtained after evaporation in step 14, centrifuging to obtain a dissolved supernatant; The first mixed acid comprises concentrated HF and concentrated HNO3, and the volume ratio of concentrated HF to concentrated HNO3 is 3:1 to 2:1; The second mixed acid comprises concentrated HCl and concentrated HNO3, and the volume ratio of concentrated HCl to concentrated HNO3 is 3:1; The step 2 comprises the following steps: Step 21: Add NaOH solution to the dissolved supernatant and heat it; Step 22: centrifuging the mixed solution obtained in step 21 to obtain a first precipitate; Step 23: adding water to the first precipitate, mixing and heating; Step 24: centrifuging the mixed solution obtained in step 23 to obtain a second precipitate; Step 25: Add concentrated HNO3 to the second precipitate and heat, and evaporate to dryness after the second precipitate is completely dissolved; Step 26: Add mixed acid to the solid obtained after evaporation in step 25, and centrifuge to obtain a coprecipitation supernatant.

2. The pretreatment method for purifying Mg in highly fractionated granite according to claim 1, characterized in that: The molar concentration of HNO3 in the primary eluent is 2M, and the molar concentration of HF is 0.5M.

3. The pretreatment method for purifying Mg in highly fractionated granite according to claim 1, characterized in that: The molar concentration of HNO3 in the secondary eluent is 0.95M.

4. The pretreatment method for purifying Mg in highly fractionated granite according to claim 1, characterized in that: The dosage of the first mixed acid is as follows: the amount of concentrated HNO3 added corresponding to 10 mg of rock powder sample is 1 ml.

5. The pretreatment method for purifying Mg in highly fractionated granite according to claim 1, characterized in that: The dosage of the second mixed acid is as follows: the amount of concentrated HNO3 added corresponding to 10 mg of rock powder sample is 1 ml.

6. The pretreatment method for purifying Mg in highly fractionated granite according to claim 1, characterized in that: In step 21, 1 to 2 ml of a 3.5 M NaOH solution is added to the dissolved supernatant.

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