A method for determining the content of phosphorite in deep-sea sediments

Abstract

The application discloses a method for determining the content of apatite in deep-sea sediments, and belongs to the technical field of component analysis. The method is characterized in that each mineral in the sediments is analyzed by X-ray diffraction spectrum and infrared spectrum, and the content of apatite in the sediments is finally accurately obtained through data processing. The content of apatite obtained by the method has a positive correlation with the content of P2O5 and CaO in the sediments, which indicates that the method has high accuracy, and the method is adaptable to sediment samples in different sea areas. The method has important significance for analyzing the occurrence mineral characteristics and content of rare earth elements in deep-sea sediments, identifying the ore-forming characteristics and formation mechanism of the deep-sea sediments, and smelting and utilizing the deep-sea sediments.

Description

Technical Field

[0001] This invention belongs to the field of component analysis technology, specifically relating to a method for determining the apatite content in deep-sea sediments. Background Technology

[0002] Rare earth resources are key mineral resources widely used in emerging industries such as new materials, new energy and information technology, and their importance is self-evident.

[0003] Deep-sea rare earth elements, also known as deep-sea rare earth-rich sediments, are a new type of rare earth resource discovered in recent years. They are mainly distributed in deep-sea basins at depths of 4000-6000 meters, rich in medium to heavy rare earth elements, with resource potential far exceeding that of terrestrial deposits. The discovery of deep-sea rare earth elements will profoundly impact the global rare earth resource landscape. Although the discovery and attention given to deep-sea rare earth-rich sediments as a new type of seabed resource came relatively late (first reported in 2011), given the similar occurrence environments of deep-sea rare earth elements and polymetallic nodules, and their frequent co-occurrence, the main mining technologies for polymetallic nodules are also applicable to deep-sea rare earth elements. It is generally believed that deep-sea rare earth elements, along with polymetallic nodules, may become among the first deep-sea mineral resources to be developed.

[0004] The discovery of deep-sea rare earth-rich sediments has attracted widespread attention both domestically and internationally, leading to extensive research on their rare earth enrichment mechanisms and controlling factors. Among these, the host minerals of rare earth elements in these sediments are a key issue in the study of rare earth mineralization and form the basis for research on the development and utilization of rare earth resources in deep-sea sediments. Recent research indicates that biogenic apatite is the main host mineral of rare earth elements in rare earth-rich sediments and is also the final host mineral. However, due to the low crystallinity and other crystalline characteristics of apatite in these sediments, X-ray diffraction analysis cannot effectively identify the spectral signal of apatite. Furthermore, the apatite spectral signal is interfered with by signals from other minerals, making it difficult to directly determine the relative content of apatite.

[0005] Therefore, establishing a method that can accurately calculate the relative content of apatite in deep-sea sediments is of great significance for analyzing the mineral characteristics and content of rare earth elements in deep-sea sediments, clarifying the mineralization characteristics and formation mechanism of deep-sea sediments, and for the beneficiation and utilization of deep-sea sediments. Summary of the Invention

[0006] This invention provides a method for determining the apatite content in deep-sea sediments, comprising the following steps: (1) X-ray analysis of the relative content of minerals X-ray diffraction patterns were used to identify and analyze sediments, and the relative mineral content in the sediments was obtained. (2) Determine the ratio of apatite to quartz mineral content. The infrared spectrum of the sediment was measured. Based on the identification of quartz and apatite peaks, the peak area of ​​the characteristic peaks of quartz and apatite was integrated to determine the peak area ratio of apatite and quartz, so as to obtain the mineral content ratio of apatite and quartz. (3) Mineral content normalization treatment The relative content of apatite was obtained by combining the ratio of apatite to quartz content obtained by infrared spectroscopy with the relative content of quartz obtained by X-ray diffraction spectroscopy. Then, the relative contents of each mineral were normalized, and the relative contents of each mineral in the sediment after normalization were calculated, so as to finally obtain the relative contents of apatite in the sediment accurately.

[0007] In the above calculation method, the formula for calculating the relative mineral content in the sediment in step (1) is as follows: ; In the formula: x i K represents the percentage content of mineral i among n quantifiable minerals. i I is the intensity factor of mineral i; i Let be the integral intensity of mineral i.

[0008] In the above method, in step (1), the mineral is one or more of the following minerals: quartz, feldspar, illite, montmorillonite, calcium cross zeolite, rock salt, kaolinite and clinoptilolite; the selection of minerals can be adjusted according to the actual situation of the minerals contained in the sediment, with X-ray identification and analysis as the standard.

[0009] In the above method, in step (2), the characteristic peak of quartz in the infrared spectrum is selected at 798 cm⁻¹. -1 The characteristic peak of apatite was selected at 565 cm⁻¹. -1 .

[0010] In the above method, in step (3), the formula for calculating the relative content of each mineral in the normalization process is as follows: relative content of each mineral = content of each mineral / total content of all minerals.

[0011] In the above calculation formula, the content of each mineral is the relative content of each mineral determined by X-ray, or the relative content of apatite obtained by calculation; the total content of all minerals is the sum of the relative content of all minerals determined by X-ray and the relative content of apatite obtained by calculation.

[0012] In one specific implementation, the formula defines the content of each mineral as the relative content of quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, or clinoptilolite determined by X-ray diffraction, or the relative content of apatite obtained by calculation; the total content of all minerals is the sum of the relative contents of quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite determined by X-ray diffraction and the relative content of apatite obtained by calculation.

[0013] To calibrate the accuracy of the above method in determining apatite content, the content of major elements in sediments can be measured, and the correlation between major elements and apatite content can be analyzed.

[0014] In the above calibration procedure, ICP-OES was used to measure the content of major elements in the sediment; the major elements were P2O5 and CaO.

[0015] In this invention, the purpose of determining the contents of the major elements P2O5 and CaO is to verify the accuracy of the method described in this invention in determining the apatite content of sediments. If the obtained apatite content is found to be positively correlated with the contents of the major elements P2O5 and CaO, it indicates that the determination method of this invention is relatively accurate.

[0016] This invention provides the application of the above method in the analysis of the mineral characteristics and content of rare earth elements in deep-sea sediments, as well as in the beneficiation and utilization of deep-sea sediments.

[0017] The beneficial effects of this invention are as follows: This invention establishes a method for determining the relative content of apatite in deep-sea sediments. The apatite content obtained by this method shows a significant positive correlation with the P2O5 and CaO contents of the sediments, indicating that the method for determining the relative content of apatite described in this invention has high accuracy and is applicable to sediment samples from different sea areas. This method is of great significance for analyzing the mineral characteristics and content of rare earth elements in deep-sea sediments, clarifying the mineralization characteristics and formation mechanisms of deep-sea sediments, and for the beneficiation and utilization of deep-sea sediments. Attached Figure Description

[0018] Figure 1 Quartz in the infrared spectrum of Pacific sediment 67-PGC23 (600-602 cm⁻¹) (left: 798 cm⁻¹) -1 ) and apatite (right: 565 cm) -1 Characteristic peak area; Figure 2 This is a graph showing the relationship between apatite content and P2O5 and CaO content in sediments. Detailed Implementation

[0019] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0020] Example 1 The following steps were taken for testing and analysis of sediments collected from deep-water basins (generally exceeding 4000 m in depth) in the Indian and Pacific Oceans: 1. Sample processing Pre-freeze the wet sediment sample and freeze-dry it in a freeze dryer or dry it in an oven at 60 °C. Grind it to about 200 mesh (74 μm) with an agate mortar and pestle and mix it well.

[0021] 2. Analysis process The ground deep-sea sediments were subjected to infrared spectroscopy and X-ray diffraction analysis using Fourier transform infrared spectroscopy and X-ray diffraction analysis respectively, to obtain the infrared spectrum and X-ray diffraction spectrum of the deep-sea sediments.

[0022] The testing procedure for X-ray diffraction analysis follows the operational requirements for whole-rock mineral identification of sediments in Part 12 of the "Marine Survey Specifications: Marine Geological Survey" (GB / T 12763.12). Specifically, this includes: an X-ray diffraction analyzer scanning range of 3°~65° (2θ), a step size of 0.02°, and a scanning speed of 2° / min; and a goniometer accuracy better than 0.05° (2θ).

[0023] 3. Processing of Analysis Results (1) X-ray analysis of the relative content of minerals The relative contents (W) of minerals such as quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite in deep-sea sediments were identified and analyzed using X-ray diffraction patterns. -1 ).

[0024] The spectral identification and analysis process follows the operational requirements for whole-rock mineral identification and quantitative analysis of sediments in the "Marine Survey Specifications Part 12: Marine Geological Survey" (GB / T12763.12). Specific operations include: smoothing the diffraction data using computer software, subtracting the background, and completing diffraction peak separation and retrieval. The diffraction data is then compared with JCPDS (Joint Committee on Powder Diffraction Standards) cards to ultimately determine the phase composition. Whole-rock mineral quantitative analysis generally uses the method employed by Cook et al. (1975) in the Deep Sea Drilling Project (DSDP) to calculate the relative mineral content. The relative mineral content is calculated using the following formula: In the formula: x i K represents the percentage content of mineral i among n quantifiable minerals. i I is the intensity factor of mineral i; i Let be the integral intensity of mineral i.

[0025] The calculation results are shown in Table 1: Table 1. Data on the content of major and trace elements and the relative mineral content of sediments. (2) Calculation of the ratio of apatite to quartz mineral content using infrared spectroscopy The ratio of apatite to quartz in deep-sea sediments was obtained using infrared spectral data. Specific procedures included: baseline correction, peak identification, and integration of the diffraction data using computer software. After identifying the quartz and apatite peaks (some deep-sea sediment samples had low apatite content, making peak identification impossible), the characteristic peaks of quartz and apatite were integrated by peak area integration, such as... Figure 1 As shown, the characteristic peak of quartz is generally selected at 798 cm⁻¹. -1 The characteristic peak of apatite is generally selected at 565 cm⁻¹. -1 Calculate the peak area ratio (A) of apatite and quartz. 磷灰石 / A 石英 To obtain the ratio of apatite to quartz mineral content.

[0026] The calculation results are shown in Table 2.

[0027] (3) Mineral content normalization treatment The relative content of apatite (W) was calculated by combining the ratio of apatite to quartz obtained from infrared spectroscopy with the relative quartz content obtained from X-ray diffraction spectroscopy. 磷灰石-2 The relative contents of each mineral were normalized again, and the relative contents (W) of minerals such as apatite, quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite in deep-sea sediments were calculated comprehensively. -3 ).

[0028] Formulas for calculating the relative content of each mineral after normalization: The relative content of each mineral = the content of each mineral / the total content of all minerals; In the above formula, the content of each mineral is the relative content of quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, or clinoptilolite determined by X-ray diffraction, or the relative content of apatite obtained by calculation; the total content of all minerals is the sum of the relative contents of quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite determined by X-ray diffraction and the relative content of apatite obtained by calculation.

[0029] The results of the normalization process are shown in Table 2: Table 2. Calculation of apatite to quartz content ratio and normalized relative mineral content in sediments using infrared spectroscopy. (4) Calibration To calibrate the accuracy of the method described in this invention in determining apatite content, the contents of major elements (P2O5 and CaO) and rare earth elements (REE) in sediments can be measured using ICP-OES and ICP-MS, respectively, and the correlation between major elements (P2O5 and CaO) and apatite content can be analyzed.

[0030] The test results are as follows Figure 2 As shown: Based on the above test results, after normalization calculations, the apatite content in the sediment showed a significant positive correlation with the P2O5 and CaO contents. This indicates that the method for calculating the relative apatite content described in this invention has high accuracy and is applicable to sediment samples from different sea areas. Apatite's chemical composition is calcium phosphate, with the chemical formula Ca5(PO4)3(F,Cl,OH). The P2O5 and CaO contents in sediments mainly originate from apatite. Therefore, the significant positive correlation between the calculated apatite content and the tested P2O5 and CaO contents demonstrates the accuracy of the method described in this invention.

[0031] In practical applications, due to the low crystallinity of apatite in sediments, X-ray diffraction analysis cannot effectively identify the spectral signal of apatite. Furthermore, the apatite spectral signal is also interfered with by signals from other minerals, making it difficult to directly determine the relative content of apatite using X-ray analysis. In other words, X-ray diffraction analysis can effectively identify minerals such as quartz in deep-sea sediments, but it cannot directly identify apatite within them.

[0032] Infrared spectroscopy is advantageous in identifying the relative content of quartz and apatite, but it is more difficult to identify other minerals. Therefore, by analyzing the ratio of quartz to apatite through infrared spectroscopy, and combining this with the relative content of other minerals such as quartz obtained through X-rays, the relative content of apatite can be calculated.

[0033] The relative contents of X-ray identifiable minerals in the sediment obtained through X-ray diffraction analysis sum to 100%. The ratio of apatite to quartz can be obtained through infrared spectroscopy. Using this ratio, combined with the relative quartz content obtained from X-ray analysis, the relative content of apatite can be calculated. At this point, the sum of the relative contents of the X-ray-identified minerals and the calculated relative content of apatite will exceed 100%. Through normalization, the relative contents of each mineral can be obtained with a sum of 100%.

[0034] Furthermore, quartz is a common and stable mineral in sediments, and its signal peaks in X-ray diffraction and infrared spectra are clear and easily identifiable. Therefore, quartz is the best intermediate mineral for both spectral analysis methods.

[0035] In summary, this invention obtains the relative contents of X-ray identifiable minerals in sediments (i.e., quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite, excluding apatite) through X-ray diffraction analysis, with the sum of these relative mineral contents reaching 100%. Then, the ratio of apatite to quartz content in the sediments is obtained using infrared spectroscopy. Using this ratio, combined with the relative quartz content obtained from X-ray analysis, the relative content of apatite can be calculated. At this point, the sum of the relative contents of the X-ray-identified minerals and the calculated relative content of apatite will exceed 100%. Then, by dividing each mineral's relative content by (the relative content of the X-ray-identified minerals + the calculated relative content of apatite), the relative content of each mineral (including apatite) can be recalculated; this calculation process is the normalization process. At this point, the sum of the relative contents of each mineral reaches 100%, thus achieving the determination of apatite content in sediments.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for determining the apatite content in deep-sea sediments, characterized in that, Includes the following steps: (1) X-ray analysis of the relative content of minerals X-ray diffraction patterns were used to identify and analyze sediments, and the relative mineral content in the sediments was obtained; the minerals were one or more of the following: quartz, feldspar, illite, montmorillonite, calcium cross-zeolite, rock salt, kaolinite, and clinoptilolite. (2) Determine the ratio of apatite to quartz mineral content. The infrared spectrum of the sediment was measured. Based on the identification of quartz and apatite peaks, the peak area of ​​the characteristic peaks of quartz and apatite was integrated to determine the peak area ratio of apatite and quartz, so as to obtain the mineral content ratio of apatite and quartz. (3) Mineral content normalization treatment The relative content of apatite was obtained by combining the ratio of apatite to quartz content obtained by infrared spectroscopy with the relative content of quartz obtained by X-ray diffraction spectroscopy. Then, the relative contents of each mineral were normalized and the relative contents of each mineral in the sediment after normalization were calculated, thus obtaining the relative content of apatite in the sediment. In step (3), the normalization process is performed using the following formula for calculating the relative content of each mineral: relative content of each mineral = content of each mineral / total content of all minerals; the content of each mineral is the relative content of each mineral determined by X-ray or the relative content of apatite obtained by calculation; the total content of all minerals is the sum of the relative content of all minerals determined by X-ray and the relative content of apatite obtained by calculation.

2. The method for determining the apatite content of deep-sea sediments according to claim 1, characterized in that, In step (1), the formula for calculating the relative mineral content in the sediment is as follows: ； In the formula: x i K represents the percentage content of mineral i among n quantifiable minerals. i I is the intensity factor of mineral i; i Let be the integral intensity of mineral i.

3. The method for determining the apatite content of deep-sea sediments according to claim 1, characterized in that, In step (2), the characteristic peak of quartz in the infrared spectrum is selected at 798 cm⁻¹. -1 The characteristic peak of apatite was selected at 565 cm⁻¹. -1 .

4. The method for determining the apatite content of deep-sea sediments according to claim 1, characterized in that, The method further includes the following steps: measuring the content of major elements in sediments using ICP-OES and analyzing the correlation between major elements and apatite content.

5. The method for determining the apatite content of deep-sea sediments according to claim 4, characterized in that, The major elements are P2O5 and CaO.

6. The application of the method described in claim 1 in the analysis of the mineral characteristics and content of rare earth elements in deep-sea sediments and in the beneficiation and utilization of deep-sea sediments.

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