A method for testing and separating inorganic nitrogen in ancient sediments.

Abstract

This invention discloses a method for testing and separating inorganic nitrogen in ancient sediments. The method involves crushing the sediment into powder and drying the powder; oxidizing a measured amount of the oxidized powder at a controlled temperature; extracting a portion of the oxidized powder as an experimental sample and subjecting it to vacuum treatment; measuring the nitrogen content of the vacuum-treated sample using an elemental analyzer; calculating the inorganic nitrogen content in the sediment through analogy; and further, placing another portion of the oxidized sediment powder in a container, adding deionized water, and stirring thoroughly; adding hydrochloric acid solution to the container and reacting thoroughly to remove carbonate minerals from the sediment powder; centrifuging the sediment powder multiple times until a suspension is formed and no further precipitation occurs; and centrifuging the suspension to obtain a solid sample. This invention enables rapid and accurate testing of inorganic nitrogen content, and the extracted nitrogen-containing clay minerals have high purity.

Description

Technical Field

[0001] This invention relates to the field of inorganic nitrogen testing and research technology, specifically to a method for testing inorganic nitrogen in ancient sediments and separating inorganic nitrogen. Background Technology

[0002] Nitrogen in sediments can be divided into organic nitrogen and inorganic nitrogen. Organic nitrogen, as the name suggests, is mainly found in organic matter and exists in the form of organic compounds such as pyridine, pyrrole, and porphyrin. Inorganic nitrogen, on the other hand, is mainly found in clay minerals and exists in the form of ammonium nitrogen. Specifically, the inorganic nitrogen in sediments mainly originates from NH4 released during the microbial degradation, diagenesis, and shallow metamorphism of sedimentary organic matter. + Because K + and NH4 + Having similar ionic radii, NH4 + Will enter the K-containing + The clay mineral lattice or interlayer becomes structurally stable fixed nitrogen, and it may also be adsorbed by clay minerals with large specific surface area to become adsorbed nitrogen.

[0003] At relatively low temperatures, these ammonium-containing clay minerals are relatively stable, making it difficult to directly test their content or isolate them for study. Existing methods for testing inorganic nitrogen content in sediments primarily involve subtracting organic nitrogen from total nitrogen in sedimentary rocks. This method involves purifying and separating organic matter from sediments, specifically using acid to dissolve and separate silicate and carbonate minerals to obtain pure organic matter. The nitrogen content in this pure organic matter is then measured, and the inorganic nitrogen content is calculated. During this separation process to obtain kerogen, inorganic nitrogen may be released as NH4+. + The NH4+ is released into the solution in a form that may adsorb some of the organic matter due to its adsorption properties. + This results in inaccurate test results, and the test method is destructive to inorganic nitrogen. Although it can obtain the content of inorganic nitrogen, it cannot be used to study the characteristics of clay minerals containing inorganic nitrogen independently.

[0004] In addition, inorganic nitrogen can be obtained by oxidizing and removing organic nitrogen from sediments using oxidants (such as hydrogen peroxide). However, for ancient sediment samples with a high degree of metamorphism, the organic matter in them has a stable structure due to degradation and thermal metamorphism, and the oxidants cannot completely oxidize the organic nitrogen. Summary of the Invention

[0005] The purpose of this invention is to provide an effective method for separating and testing inorganic nitrogen in sediments, in order to solve the technical problems of inaccurate measurement methods of inorganic nitrogen in the prior art and the inability to separate and study the characteristics of clay minerals containing inorganic nitrogen.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A method for testing inorganic nitrogen in ancient sediments includes the following steps:

[0008] The sediment was crushed into powder, and the sediment powder was dried.

[0009] A measured amount of sediment powder is heated and oxidized to remove organic matter from the sediment powder;

[0010] Experimental samples were extracted from the oxidized sediment powder and subjected to vacuum treatment to eliminate the influence of background nitrogen levels in the air.

[0011] The nitrogen content of the experimental sample after vacuum treatment was tested using an elemental analyzer.

[0012] The inorganic nitrogen content in the sediment was calculated by analogy.

[0013] As a preferred embodiment of the present invention, the specific steps for removing organic matter from the sediment powder are as follows:

[0014] Take a fixed amount of the sediment powder and spread it evenly in the cleaned and dried heat-conducting container. Record the mass M1 of the heat-conducting container and the mass M2 of the heat-conducting container after the sediment powder is placed in it.

[0015] The heat-conducting container containing the sediment sample was placed in a heating furnace for heat treatment.

[0016] The heat-conducting container is cooled after heat treatment, and its mass M3 is recorded at this time.

[0017] As a preferred embodiment of the present invention, the heating furnace has a heating rate of 200°C / h, and after reaching the rated temperature, it is kept at a constant temperature for 24 hours to fully oxidize and remove organic matter.

[0018] As a preferred embodiment of the present invention, the inorganic nitrogen content in sediments is obtained through analogy calculation as follows:

[0019] Inorganic nitrogen content = nitrogen element content × [(M3-M1) / (M2-M1)];

[0020] Wherein, M2 is the mass of the heat-conducting container after the deposit powder is placed in it; M1 is the mass of the heat-conducting container after cleaning and drying; and M3 is the mass of the heat-conducting container after the deposit powder is heat-treated and cooled.

[0021] To solve the above-mentioned technical problems, the present invention further provides the following technical solution: a method for separating inorganic nitrogen from ancient sediments, comprising the following steps:

[0022] Take the remaining sample from the oxidized sediment powder and place it in a container. Add deionized water and stir thoroughly.

[0023] Add hydrochloric acid solution to the container and allow it to react fully to remove carbonate minerals from the sediment powder;

[0024] The sediment powder was centrifuged multiple times until the sediment powder solution no longer precipitated and formed a suspension;

[0025] The suspension was centrifuged to obtain a solid sample.

[0026] As a preferred embodiment of the present invention, the sediment powder is subjected to multiple centrifugation processes, which are divided into a washing and centrifugation stage and a suspension separation stage.

[0027] The washing and centrifugation stage is implemented as follows:

[0028] Pour the mixture after adding hydrochloric acid solution and allowing it to react fully into a centrifuge tube and centrifuge.

[0029] Add deionized water to the mixture after centrifugation, pour it into a centrifuge tube, and repeat the centrifugation to remove the added hydrochloric acid;

[0030] Discard the supernatant solution after centrifugation and check its pH value. If the pH value is not equal to 7, pour it into a centrifuge tube and repeat the centrifugation. Repeat this process multiple times until the pH value of the supernatant solution after centrifugation is equal to 7. At this point, the added hydrochloric acid is considered to have been completely removed.

[0031] As a preferred embodiment of the present invention, the suspension separation stage is implemented as follows:

[0032] Add the cleaned sample to deionized water and stir thoroughly. Let it stand in a dust-free environment until the upper solution is clear.

[0033] Discard the supernatant solution after it has settled, add deionized water and stir thoroughly. Repeat this process several times until the supernatant solution stops precipitating after standing for more than 72 hours, forming a suspension. At this point, the minerals in the suspension are nitrogen-containing clay minerals with a diameter of less than 2 μm.

[0034] As a preferred embodiment of the present invention, the solid sample is dried to obtain clay minerals containing inorganic nitrogen.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] This invention provides a method that can accurately test the inorganic nitrogen content in sediments and separate inorganic nitrogen-containing minerals. It utilizes high-temperature oxidation to remove organic matter, enabling rapid and accurate testing of inorganic nitrogen content in ancient sedimentary rocks with a high degree of organic matter removal. The method also achieves the separation and purification of inorganic nitrogen-containing minerals through mineral separation and purification, allowing for the separate testing of inorganic nitrogen clay minerals. Attached Figure Description

[0037] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall process for testing and separating inorganic nitrogen in an embodiment of the present invention;

[0039] Figure 2 This is a comparison of the X-ray diffraction patterns of minerals in sedimentary rock samples that have undergone high-temperature treatment and those that are original sedimentary rock samples in an embodiment of the present invention.

[0040] Figure 3 This is a comparison chart showing the results of the kerogen extraction method in this embodiment of the invention and the inorganic nitrogen content test results of the sample using this method. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] like Figure 1 As shown, this invention provides a method for testing inorganic nitrogen in ancient sediments. Existing testing methods usually involve adding oxidants (such as hydrogen peroxide) to oxidize the organic matter in the sediments. However, the organic matter in ancient sedimentary rocks has undergone diagenesis and thermal metamorphism, making its structure more stable and difficult to oxidize with oxidants such as hydrogen peroxide. Therefore, it must be removed by high temperature.

[0043] This embodiment utilizes a high-temperature oxidation method to remove organic matter, which can quickly and accurately test the inorganic nitrogen content in ancient sedimentary rocks, and achieves a high degree of organic matter removal.

[0044] Includes the following steps:

[0045] (1) The sediment is crushed into powder and the sediment powder is dried.

[0046] Specifically, the sediment is crushed into a powder smaller than 200 mesh using a sample crusher to allow for sufficient contact between organic matter and oxygen. The sediment powder is then dried to remove the influence of moisture.

[0047] (2) Take a certain amount of sediment powder and heat it to oxidize it in order to remove the organic matter in the sediment powder.

[0048] Since almost all organic nitrogen is in organic matter, organic nitrogen is also removed when organic matter is removed at high temperatures.

[0049] The specific steps for removing organic matter from the sediment powder are as follows:

[0050] Take a fixed amount of the deposit powder and spread it evenly in a cleaned and dried heat-conducting container (such as a small ceramic crucible). Place the cleaned crucible in a drying oven to dry it, removing the potential influence of moisture in the crucible. Record the mass M1 of the heat-conducting container and the mass M2 of the heat-conducting container after the deposit powder is placed in it.

[0051] The heat-conducting container containing the sediment sample is placed in a heating furnace for heat treatment. The heating furnace has a heating rate of 200℃ / h and is kept at the rated temperature for 24 hours to fully oxidize and remove organic matter.

[0052] The heat-conducting container is cooled after heat treatment. Specifically, the heat-conducting container is placed in a drying cabinet and cooled to room temperature. It is then weighed and its mass M3 is recorded.

[0053] It should also be noted that the inorganic nitrogen in the sediments mainly originates from NH4 released during the microbial degradation, diagenesis, and mild metamorphism of sedimentary organic matter. + Because K + and NH4 + Having similar ionic radii, NH4 + Will enter the K-containing + The clay mineral lattice or interlayer becomes structurally stable fixed nitrogen, while NH4+ + It may also be adsorbed by clay minerals with a large specific surface area, becoming adsorbed nitrogen.

[0054] To verify that the temperature-increasing oxidation method of this embodiment does not affect the storage of inorganic nitrogen, the mineral composition of the original sediment sample and the sediment powder oxidized at high temperature in this embodiment was tested using XRD. Figure 2As shown, the results obtained are as follows: the mineral composition of the original sediment sample is quartz (57.3%), plagioclase (7.6%), and illite (38.65%), and the mineral composition after high-temperature oxidation is quartz (53.2%), plagioclase (6.2%), and illite (40.2%).

[0055] This shows that high-temperature oxidation basically does not change the mineral composition of the sediment samples, and therefore does not destroy the crystal structure of the minerals. In other words, heat treatment has little effect on the content of inorganic nitrogen. Moreover, according to the test data, high-temperature conditions do not affect adsorbed nitrogen. In addition, the proportion of adsorbed nitrogen in ancient sediments is small, and its contribution to inorganic nitrogen is minimal. Therefore, the high-temperature oxidation process does not affect the content of inorganic nitrogen composed of fixed nitrogen or adsorbed nitrogen.

[0056] In addition, after repeated tests on different samples, 450℃ can remove almost all organic matter in ancient rocks without causing loss of inorganic nitrogen or damage to minerals. Therefore, temperatures below or above 450℃ are not suitable. 450℃ is the rated temperature for removing organic matter.

[0057] (3) Extract experimental samples from the oxidized deposit powder and vacuum treat the experimental samples to eliminate the influence of the background value of nitrogen in the air. Specifically, place the experimental samples into a tin boat and wrap them, and squeeze them fully to eliminate the influence of the background value of nitrogen in the air.

[0058] (4) The nitrogen content of the experimental sample after vacuum treatment was tested using an elemental analyzer. Specifically, the nitrogen content was measured using a Vario EL III elemental analyzer. The nitrogen at this time was inorganic nitrogen.

[0059] (5) The inorganic nitrogen content in the sediment was obtained by analogy calculation.

[0060] The method for calculating the inorganic nitrogen content in sediments by analogy is as follows:

[0061] Inorganic nitrogen content = nitrogen element content × [(M3-M1) / (M2-M1)];

[0062] Wherein, M2 is the mass of the heat-conducting container after the deposit powder is placed in it; M1 is the mass of the heat-conducting container after cleaning and drying; and M3 is the mass of the heat-conducting container after the deposit powder is heat-treated and cooled.

[0063] To verify the experimental effect of the method for testing inorganic nitrogen in sediments provided in this embodiment, mature organic-rich shale from the Lower Cambrian period in southern China was selected, and the results of the original kerogen separation method and the method of this technology were compared.

[0064] Twelve Lower Cambrian organic-rich shale samples were selected from southeastern Chongqing. Inorganic nitrogen content was tested using both the kerogen extraction method and the method described in this embodiment. The results show that the inorganic nitrogen content measured using this embodiment is comparable to that obtained using the kerogen extraction method. Details are attached. Figure 3 As shown, the method of this embodiment is reliable. The content tested by the kerogen extraction method is lower than that tested by the method of this embodiment, indicating that some NH4 is released during the acid dissolution process of the kerogen extraction method. + The inorganic nitrogen content test results were lower due to adsorption by organic matter, which proves that the test solution of this technology is not only simpler in procedure than the original method, but also more accurate. Compared with the existing technology, it is very easy to obtain accurate inorganic nitrogen measurement results.

[0065] In addition, this embodiment also provides a method for separating inorganic nitrogen from ancient sediments. Based on the above-mentioned method for testing inorganic nitrogen in ancient sediments, the method achieves the separation and purification of minerals containing inorganic nitrogen through mineral separation and purification, and can test inorganic nitrogen clay minerals separately.

[0066] Specifically, the following steps are included:

[0067] (1) Take out another part of the remaining sample from the oxidized sediment powder and put it into a container. Add deionized water and stir thoroughly. At this time, the solution in the container is turbid.

[0068] Of the deposited powder after heating and oxidation, a portion is placed in a tin boat for measuring the inorganic nitrogen content.

[0069] (2) Add hydrochloric acid solution to the container and react fully to remove carbonate minerals from the sediment powder. Generally, a hydrochloric acid solution with a concentration of 6 mol / L is selected to remove carbonate minerals in the sediment that may cause problems, so as to carry out the subsequent separation of nitrogen-containing clay minerals.

[0070] (3) The sediment powder is centrifuged multiple times until the sediment powder solution no longer precipitates to form a suspension.

[0071] The sediment powder is subjected to multiple centrifugation processes, which are divided into a washing and centrifugation stage and a suspension separation stage.

[0072] The washing and centrifugation stage is implemented as follows:

[0073] (I) Pour the mixture after adding hydrochloric acid solution and reacting fully into a centrifuge tube and centrifuge;

[0074] (II) Add deionized water to the mixture after centrifugation, pour it into a centrifuge tube, and repeat the centrifugation.

[0075] (III) Discard the supernatant solution after centrifugation and test the pH value of the supernatant solution after centrifugation. If the pH value is not equal to 7, pour it into a centrifuge tube and repeat the centrifugation. Repeat this process multiple times until the pH value of the supernatant solution after centrifugation is equal to 7. This indicates that the hydrochloric acid in the sediment powder solution has been basically removed.

[0076] The suspension separation stage uses a static suspension method to separate ammonium-containing clay minerals with a diameter of less than 2 μm. The specific implementation method is as follows:

[0077] Add the cleaned sample to deionized water and stir thoroughly. Let it stand in a dust-free environment until the upper solution becomes clear due to precipitation.

[0078] Discard the supernatant solution after it has settled, add deionized water and stir thoroughly. Repeat this process several times until the supernatant solution stops precipitating after standing for more than 72 hours, forming a suspension. At this point, the suspended particles in the suspension are considered to be ammonium-containing clay minerals with a diameter of less than 2 μm.

[0079] (4) Centrifuge the suspension to obtain a solid sample, dry the solid sample to obtain clay minerals containing inorganic nitrogen.

[0080] Therefore, in the step of testing inorganic nitrogen in sediments in this embodiment, after acidification and washing of the sediments after heating and oxidation, organic nitrogen is removed to the greatest extent. After multiple centrifugation operations, ammonium-containing clay minerals with a diameter of less than 2 μm are obtained. At this time, the inorganic nitrogen-containing minerals are separated, and the inorganic nitrogen clay minerals can be tested separately.

[0081] Obviously, in the above methods, the degree of removal of organic nitrogen directly affects the purity of the obtained ammonium-containing clay minerals. In this embodiment, the organic nitrogen has been removed from the sediment after high-temperature oxidation, thus improving the extraction purity of inorganic nitrogen clay minerals.

[0082] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A method of testing for inorganic nitrogen in ancient sediments, characterised in that, The method comprises the following steps: crushing the deposit into powder, and drying the deposit powder; taking a certain amount of the deposit powder and heating and oxidizing the same to remove organic matter in the deposit powder; wherein the specific implementation steps for removing the organic matter in the deposit powder are as follows: taking a certain amount of the deposit powder and fully laying the same in a heat-conducting container after cleaning and drying, recording the mass M1 of the heat-conducting container and the mass M2 of the heat-conducting container after the deposit powder is put into the same; putting the heat-conducting container containing the deposit powder into a heating furnace for heat treatment; the heating furnace has a heating rate of 200℃ / h, and after being heated to a rated temperature, the same is kept at the rated temperature for 24 hours to sufficiently oxidize and remove the organic matter, wherein the rated temperature for removing the organic matter is 450℃; cooling the heat-conducting container after the heat treatment, and recording the mass M3 of the heat-conducting container at this time; taking a test sample from the deposit powder after the heating and oxidizing, and vacuum treating the test sample to eliminate the influence of the background value of nitrogen in air; using an element analyzer to test the nitrogen element content of the test sample after the vacuum treatment; calculating the inorganic nitrogen content in the deposit by analogy; wherein the implementation manner for calculating the inorganic nitrogen content in the deposit is as follows: inorganic nitrogen content=nitrogen element content×[(M3-M1) / (M2-M1)]; wherein M2 is the mass of the heat-conducting container after the deposit powder is put into the same, M1 is the mass of the heat-conducting container after cleaning and drying, and M3 is the mass of the heat-conducting container after the deposit powder is heat treated and cooled.

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