A method for extracting and testing carbonate-bound chlorine in a carbonate geological sample

Abstract

The application discloses a kind of carbonate geological sample carbonate combined state chlorine extraction test methods, using deionized water to wash carbonate geological sample to no chlorine ion, after sample drying, add acetic acid solution to dissolve, obtain dissolving solution;Dissolving solution is added in cation exchange resin, and the solution after exchange is collected;10ppm In internal standard is added in the solution collected after resin exchange, the chlorine ion content in solution is detected using inductively coupled plasma mass spectrometry;Dilute dissolving solution using dilute nitric acid solution, use inductively coupled plasma optical emission spectrometry to detect the calcium magnesium content in dilution solution liquid, calculate carbonate combined state chlorine value, i.e. Cl / Ca value or Cl / (Ca+Mg) value.The application is washed by deionized water Sample, acetic acid dissolves sample, ICP-MS, ICP-OES detects solution element content, not only can effectively extract, test carbonate combined state chlorine in carbonate geological sample, avoid the pollution of non-carbonate mineral chlorine, also have the characteristics that experimental reagent is easy to obtain, simple operation, detection precision is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical analysis of carbonate geological samples. More specifically, the present application relates to a method for extracting and testing carbonate associated chloride in carbonate geological samples. BACKGROUND

[0002] It is found that the content of chloride ions in synthetic carbonate minerals (aragonite and calcite) and the content of chloride ions in carbonate minerals are in a linear relationship, which implies that carbonate geological samples may record the chloride content in seawater at the time of their formation, i.e. salinity, indicating that the content of chloride ions in carbonate minerals (carbonate associated chloride, expressed as Cl / (Ca+Mg)) can be used as a paleo-ocean salinity indicator.

[0003] Although there are a large number of experimental methods for analyzing the chloride content in geological samples, including sample pretreatment processes such as leaching, alkali fusion, high-temperature pyrolysis, water vapor distillation, etc., and chloride testing processes such as ion chromatography, neutron activation, plasma mass spectrometry / spectroscopy, electrochemical methods, X-ray fluorescence spectroscopy, spectrophotometry, etc., all of these sample pretreatment and testing methods currently extract total chloride from geological samples or directly test the total chloride content in the samples. There is no extraction and testing method for chloride in a certain specific mineral phase, especially for carbonate associated chloride. Geological samples are a complex matrix containing a large amount of chloride in non-carbonate mineral phases.

[0004] Therefore, the difficulty of extracting and testing carbonate associated chloride in geological samples lies in how to extract and test only the chloride in carbonate minerals (i.e. carbonate associated chloride) from carbonate geological samples, avoiding the contamination of chloride in non-carbonate minerals. SUMMARY

[0005] The present application provides a method for extracting and testing carbonate associated chloride in carbonate geological samples, which can effectively extract carbonate associated chloride in geological samples and avoid the contamination of chloride in non-carbonate minerals.

[0006] The present application provides a method for extracting and testing carbonate associated chloride in carbonate geological samples, the operation process of which is as shown in Figure 1 The method comprises the following steps:

[0007] 1) repeatedly rinse the carbonate geological sample with deionized water until no chloride ions are detected in the washing liquid, and then dry the sample.

[0008] 2) weigh the dried sample containing 0.5g of carbonate minerals, dissolve the dried sample with a quantitative acetic acid solution, centrifuge the sample, and obtain the dissolved supernatant.

[0009] 3) Add the supernatant into the prepared cation exchange resin column, add an appropriate amount of acetic acid solution, flush the cation resin column, and collect the solution after cation resin exchange.

[0010] 4) Add 10 ppm of In internal standard to the collected solution after resin exchange, and detect the content of chloride ions in the solution by inductively coupled plasma mass spectrometry (ICP-MS).

[0011] 5) Dilute the supernatant with dilute nitric acid solution, and detect the content of calcium and magnesium in the diluted solution by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0012] Further, the carbonate geological sample in step 1) is a powder sample with a particle size of about 200 mesh, the carbonate mineral is one of calcite or dolomite, and the content is greater than 50%, and the apatite mineral content is less than 5%.

[0013] Further, the conductivity of the deionized water in step 1) reaches 18.2 MΩ / cm, and does not contain chloride ions.

[0014] Further, the acetic acid solution in step 2) has a volume concentration of 4%, which is prepared from HPLC grade glacial acetic acid and deionized water.

[0015] Further, the carbonate mineral sample in step 2) is weighed at 0.5 g ± 0.001 g, 15 ml of 4% acetic acid solution is added to dissolve the calcite sample, and 16.39 ml of 4% acetic acid solution is added to dissolve the dolomite sample.

[0016] Further, the prepared cation exchange resin in step 3) is obtained by 50W-X8 cation resin after soaking in nitric acid and acetic acid.

[0017] Further, after adding the supernatant solution in step 3), 8-10 ml of 4% acetic acid solution is added to the cation exchange resin column to ensure that all chloride ions in the resin column are flushed down.

[0018] Further, the dilute nitric acid in step 5) is 2% nitric acid prepared from twice sub-boiling distilled pure grade nitric acid and deionized water.

[0019] Further, the ICP-MS and ICP-OES in step 5) detect the content of chloride ions and calcium and magnesium ions in the solution, respectively.

[0020] Further, the Cl / Ca value in step 5) is for the combined state chlorine content of the carbonate mineral being calcite; and the Cl / (Ca+Mg) value is for the combined state chlorine content of the carbonate mineral being dolomite.

[0021] The principle of the present application is that the non-carbonate mineral chlorine contamination in the carbonate geological sample is mainly from the chloride salt and the chloride ion from the apatite and clay mineral. Since the apatite content in the carbonate geological sample (limestone or dolomite) is usually low, the present extraction test method first selects the carbonate geological sample with the apatite content less than 5% to exclude the influence of the apatite mineral chlorine. Then, the carbonate geological sample powder is repeatedly washed with deionized water until no chloride ion is detected in the washing liquid. Through this step, the contamination from the chloride salt is eliminated. Then, the carbonate geological sample is dissolved using a 4% acetic acid solution to destroy the carbonate mineral and release the carbonate combined state chlorine. The 4% acetic acid is a very weak acid, and the volatility of the chloride ion therein is very weak, which will not cause the loss of chlorine during the experiment, as shown in the following formula: Figure 2 At the same time, the weak acidity of the 4% acetic acid will not dissolve the silicate mineral, avoiding the contamination from the clay mineral chlorine. By reasonably selecting the sample, repeatedly washing the sample with deionized water and dissolving the sample with a 4% acetic acid solution, the contamination from the apatite, chloride salt and clay mineral non-carbonate mineral chlorine is avoided respectively, and the extraction is effectively only for the carbonate combined state chlorine in the carbonate geological sample, and then the content of chlorine, calcium, magnesium and other elements is tested using ICP-MS and ICP-OES.

[0022] The present application uses the Cl / Ca value or the Cl / (Ca+Mg) value to represent the carbonate combined state chlorine content. When the carbonate mineral of the carbonate geological sample is calcite, the Cl / Ca value is used to represent the carbonate combined state chlorine content, and when the carbonate mineral of the carbonate geological sample is dolomite, the Cl / (Ca+Mg) value is used to represent the carbonate combined state chlorine content.

[0023] Compared with the existing extraction test method of the chlorine in the geological sample, the present application has the following beneficial effects:

[0024] 1) The method can extract and test the chlorine in the single mineral in the carbonate geological sample, i.e. the chlorine in the carbonate mineral (carbonate combined state chlorine), which can avoid the influence of the contamination from the chloride salt, phosphate and silicate in the whole rock.

[0025] 2) The chemical reagent used in the method has small toxicity, the sample pretreatment process is simple, the chlorine ion test is convenient, and the experimental results have good repeatability.

[0026] Other advantages, objects and features of the present application will be partly embodied by the following description, and partly understood by those skilled in the art through the study and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Flow chart of the method for extracting and testing carbonate-bound chlorine in carbonate geological samples.

[0028] Figure 2 Chloride ion recovery rate in 4% acetic acid solution with different contents over time.

[0029] Figure 3 Cl / (Ca+Mg) values of GSR-23, DYG-110, G-G mixture, D-G mixture, and GSR-23, DYG-110 without step one treatment. DETAILED DESCRIPTION

[0030] The present application provides a method for extracting and testing carbonate-bound chlorine in carbonate geological samples, the operation process is as shown in Figure 1 The specific implementation is as follows:

[0031] Step one: weigh 5g of carbonate geological sample and add it to a 50ml centrifuge tube, add 40ml of deionized water, shake on a shaker for 2 hours (1500r / min), centrifuge, pour out the washing liquid, and then add 40ml of deionized water to repeatedly wash the sample until the washing liquid no longer contains chloride ions;

[0032] Step two: dry the washed sample, weigh 0.5g of sample containing carbonate minerals according to the carbonate mineral content of the sample, add 15ml of 4% acetic acid solution for limestone samples, and add 16.39ml of 4% acetic acid solution for dolomite samples, shake on a shaker for 2 hours, and centrifuge the sample;

[0033] Step three: use a pipette to take 6ml of supernatant from the centrifuged solution in step two and add it to a prepared resin column, then add 8-10ml of 4% acetic acid to the resin column after the solution is filtered, and collect the filtrate;

[0034] Step four: add In element internal standard to the collected filtrate to make its content 10ppb;

[0035] Step five: use 4% acetic acid to prepare a chloride ion standard solution and add 10ppb of In internal standard, start ICP-MS, establish a calibration curve, and test the chloride content of the solution in step four;

[0036] Step six: dilute the solution in step two with dilute nitric acid, use ICP-OES to test the Ca and Mg element content, and calculate the carbonate-bound chlorine content, i.e. Cl / Ca value or Cl / (Ca+Mg) value.

[0037] The carbonate geological sample is a powder sample with a particle size greater than 200 mesh. The carbonate mineral is either calcite or dolomite, and its content is greater than 50%. The apatite mineral content is less than 5%.

[0038] The deionized water has a conductivity of 18.2 MΩ / cm and contains no chloride ions.

[0039] The acetic acid solution is a 4% (v / v) acetic acid solution prepared from HPLC-grade glacial acetic acid and deionized water.

[0040] The prepared cation exchange resin is composed of 50W-X8 cationic resin is obtained by soaking in nitric acid and acetic acid.

[0041] The dilute nitric acid is nitric acid with a volume concentration of 2%, prepared by pure nitric acid purified by double sub-boiling distillation and deionized water.

[0042] The cleaning process in step one requires that the final cleaning solution no longer contains chloride ions.

[0043] In step two, the sample dissolution process involves weighing a sample containing 0.5g ± 0.001g of carbonate minerals based on the sample's carbonate mineral content. 15ml of 4% acetic acid is added to dissolve the carbonate minerals in the calcite sample (limestone), and 16.39ml of 4% acetic acid solution is added to dissolve the carbonate minerals in the dolomite sample (dolomite).

[0044] In step three, after adding 6 ml of solution supernatant, add 8-10 ml of 4% acetic acid solution to the cation exchange resin column to ensure that all chloride ions in the resin column are flushed out.

[0045] In steps five and six, the elements are detected using ICP-MS and ICP-OES to determine the chloride ion content and calcium and magnesium ion content in the solution, respectively.

[0046] The chloride value of the carbonate-bound state in step six is ​​represented by the Cl / Ca value for calcite carbonate minerals and by the Cl / (Ca+Mg) value for dolomite carbonate minerals.

[0047] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement the experimental method with reference to the description. It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials mentioned are commercially available unless otherwise specified.

[0048] Example 1

[0049] The extraction test method of carbonate nodule of the above carbonate geological sample was used to extract and test the carbonate-bound chlorine of carbonate rock geological standard sample GSR-23 and carbonate geological sample DYG-110, and the experimental operation process was as follows:

[0050] Step one: 5 g of carbonate rock geological standard sample GSR-23 and carbonate geological sample DYG-110 were weighed in a 50 ml centrifuge tube, 40 ml of deionized water was added, and oscillation was carried out on a shaker for 2 hours (1500 r / min), centrifugation was carried out, the washing liquid was poured out, and 40 ml of deionized water was added again. The GSR-23 and DYG-110 samples were repeatedly washed until there was no chloride ion in the washing liquid;

[0051] Step two: The washed samples were dried, and according to the carbonate mineral content (98%) of the GSR-23 sample and the carbonate mineral content (65%) of the DYG-110 sample, 0.5102 g of the GSR-23 sample was weighed three times, 0.7692 g of the DYG-110 sample was weighed three times, and 15 ml of 4% acetic acid solution was added to each of the six samples, oscillation was carried out on a shaker for 2 hours, and the samples were centrifuged;

[0052] Step three: 6 ml of the supernatant of the six centrifuged solutions was respectively taken by a pipette and added to six prepared resin columns, and after the solution was filtered, 10 ml of 4% acetic acid was added to each resin column, and the filtrate was collected;

[0053] Step four: In elements were added to the collected filtrate to make the content 10 ppb;

[0054] Step five: Chloride standard solution was prepared using 4% acetic acid, 10 ppb of In internal standard was added, ICP-MS was started, the calibration curve was established, and the chlorine content of the solution in step four was tested;

[0055] Step six: The dissolved supernatant in step two was appropriately diluted with 2% nitric acid, ICP-OES was used to test the contents of Ca and Mg elements, and the carbonate-bound chlorine contents of the three GSR-23 samples and the three DYG-110 samples, i.e. the Cl / (Ca+Mg) values, were calculated.

[0056] The test results are shown in Table 1. Figure 3 Figure 3 ​It can be observed that consistent results were obtained for both GSR-23 and DYG-110 samples using the present application, with a Cl / (Ca+Mg) value of ~0.06 for GSR-23 and a Cl / (Ca+Mg) value of ~0.397 for DYG-110. In comparison to the GSR-23 and DYG-110 samples and the samples that were not repeatedly rinsed with deionized water (i.e. GSR-23 without water rinse and DYG-110 without water rinse), the Cl / (Ca+Mg) values of both samples decreased significantly by ~50%, indicating that the cleaning process of Step 1 effectively removed the chloride salt contaminants from the carbonate geological samples, and also indicating that the chloride salt contaminants are the most important contaminants of the carbonate-bound chloride in the carbonate geological samples, and that the repeated water rinsing process of Step 1 is critical in the extraction of the carbonate-bound chloride from the carbonate geological samples.

[0057] Example Two

[0058] In this example, the extraction test method for carbonate nodule from carbonate geological samples described above was used to extract the carbonate-bound chloride from a 1:1 mixture of carbonate rock geological standard GSR-23 and stream sediment GSD-15 (G-G mixture), and a 1:1 mixture of carbonate rock geological sample DYG-110 and stream sediment GSD-15 (D-G mixture), with the experimental procedure as follows:

[0059] Step 1: The cleaned GSR-23 carbonate rock geological standard and DYG-110 carbonate rock sample were each mixed with stream sediment GSD-15 in a 1:1 ratio to form a G-G mixture and a D-G mixture, respectively.

[0060] Step 1: 5 g of each of the G-G mixture and the D-G mixture was weighed into a 50 ml centrifuge tube, 40 ml of deionized water was added, and the mixture was shaken on a shaker for 2 hours (1500 r / min), centrifuged, and the washing solution was discarded. The GSR-23 and DYG-110 samples were repeatedly rinsed with 40 ml of deionized water until the washing solution no longer contained chloride ions.

[0061] Step 2: The cleaned samples were dried, and based on the carbonate mineral content of the G-G mixture (49%) and the carbonate mineral content of the D-G mixture (32.5%), 1.0204 g of the G-G mixture was weighed into three portions, and 1.5384 g of the D-G mixture sample was weighed into three portions. 15 ml of 4% acetic acid solution was added to each of the six samples, and the samples were shaken on a shaker for 2 hours and centrifuged.

[0062] Step 3: Use a pipette to take 6 ml of the supernatant of the centrifuged solution into each of the six prepared resin columns. After the solution is filtered, add 10 ml of 4% acetic acid to each resin column and collect the filtrate.

[0063] Step 4: Add an internal standard of In to the collected filtrate to make its concentration 10 ppb;

[0064] Step 5: Prepare a chloride ion standard solution using 4% acetic acid, add 10 ppb of In internal standard, start ICP-MS, establish a standard line, and test the chloride content of the solution from Step 4;

[0065] Step 6: Dilute the supernatant from Step 2 with 2% nitric acid (by volume). Use ICP-OES to test the Ca and Mg content. Calculate the carbonate-bound chlorine content (Cl / (Ca+Mg)) of the three GSR-23 samples and the three DYG-110 samples.

[0066] Test results are as follows Figure 3 As shown. From Figure 3 It can be observed that the Cl / (Ca+Mg) values ​​of samples GSR-23 and DYG-110 are almost identical to those of the GG and DG mixtures, respectively. GSD-15 is a stream sediment with a chlorine content of ~53 ppm, representing common silicate minerals in carbonate rock systems. Sample GSD-15 was mixed with DYG-110 and GSR-23 at a 1:1 ratio, which is equivalent to incorporating 50% silicate debris into the carbonate sample. The mixed sample was then dissolved using 4% acetic acid to extract the chlorine content. If the extracted chlorine content of the mixed sample was significantly higher than that of the DYG-110 and GSR-23 samples, it indicates that dissolving the sample in 4% acetic acid may have destroyed 50% of the GSD-15 sample component in the mixed sample, leading to the release of chlorine from its silicate minerals. If the chlorine content extracted from the mixed sample is similar to that in samples DYG-110 and GSR-23, it indicates that dissolving the sample in 4% acetic acid does not damage the silicate minerals in the sample.

[0067] After repeated rinsing with deionized water, the Cl / (Ca+Mg) values ​​of GSR-23 and DYG-110 samples were almost identical to those of the rinsed and dried GG and DG mixtures. This indicates that 4% acetic acid does not damage the silicate minerals (clay minerals) in the carbonate geological samples, thus preventing contamination by non-carbonate chlorine.

[0068] The above two examples fully demonstrate the method of the present application, i.e. a method for extracting and testing carbonate-bound chlorine in a carbonate geological sample - the experimental scheme of repeatedly flushing the carbonate rock sample with deionized water and then using 4% acetic acid for dissolution can effectively avoid the pollution of non-carbonate mineral chlorine, thereby effectively extracting carbonate-bound chlorine.

[0069] Although embodiments of the present application have been disclosed in connection with the above specification and drawings, it should be understood that they are not limited to the particular embodiments disclosed herein but rather, they are intended to cover modifications and equivalents, and are intended to cover all alternatives falling within the scope of the claims and equivalents thereof.

Claims

1. A method for extracting and testing carbonate-bound chloride in a carbonate geological sample, comprising: 1) repeatedly rinsing a carbonate geological sample with deionized water until no chloride ions are detected in the rinse solution, and then drying the sample; the carbonate geological sample should have a carbonate mineral content greater than 50% and an apatite mineral content less than 5%; 2) weighing the dried sample and dissolving the sample with a quantitative acetic acid solution, and centrifuging the sample to obtain a dissolved supernatant; the acetic acid solution has a concentration of 4% by volume; 3) adding the dissolved supernatant to a prepared cation exchange resin column, adding 8-10 ml of the 4% acetic acid solution to rinse the column, and collecting the solution after exchange with the cation exchange resin; the cation exchange resin is obtained by soaking AG® 50W-X8 cation exchange resin in nitric acid and acetic acid; 4) adding 10 ppm of In internal standard to the collected solution of step 3), and detecting the chloride ion content in the solution using an inductively coupled plasma mass spectrometer; 5) diluting the dissolved supernatant of step 2) with a dilute nitric acid solution, detecting the calcium and magnesium content of the diluted solution using an inductively coupled plasma spectrometer, and calculating the carbonate-bound chloride content of the carbonate geological sample, i.e. the Cl / Ca value or the Cl / (Ca+Mg) value.

2. The method for extracting and testing according to claim 1, wherein: the carbonate geological sample in step 1) is a powder sample with a particle size greater than 200 mesh.

3. The method for extracting and testing according to claim 2, wherein: the carbonate mineral is one of calcite or dolomite.

4. The method for extracting and testing according to claim 1, wherein: the deionized water in step 1) has a conductivity of 18.2 MΩ / cm and does not contain chloride ions.

5. The method for extracting and testing according to claim 1, wherein: the weighed amount of the dried sample in step 2) is 0.5 g ± 0.001 g.

6. The method for extracting and testing according to claim 1, wherein: the dissolution of the sample with the quantitative acetic acid solution in step 2) comprises: 15 ml of acetic acid solution to dissolve the sample with calcite as the carbonate mineral; and 16.39 ml of acetic acid solution to dissolve the sample with dolomite as the carbonate mineral.

7. The method for extracting and testing according to claim 1, wherein: the dilute nitric acid in step 5) has a concentration of 2% by volume and is prepared from double sub-boiling distilled pure nitric acid and deionized water.

8. The method for extracting and testing according to claim 1, wherein: the Cl / Ca value in step 5) is for the carbonate-bound chloride content when the carbonate mineral is calcite; and the Cl / (Ca+Mg) value is for the carbonate-bound chloride content when the carbonate mineral is dolomite.

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