Method for extracting and detecting magnetic minerals in surface sediments in floating rice planting area

Abstract

The invention discloses a method for extracting and detecting magnetic minerals in surface sediments in a floating rice planting area, which comprises the following steps: S1, collecting the surface sediments in the floating rice planting area, and fully dispersing surface sediment samples on paper; s2, wrapping a super-strong magnet with a plastic film, and suspending the super-strong magnet above the sediment sample for repeated adsorption; s3, the adsorbed particles are placed in clear water again, magnetic separation is repeatedly conducted for four to six times, and further purification is conducted to obtain magnetic minerals; s4, carrying out pretreatment on the obtained magnetic mineral sample, and carrying out iron and oxygen element identification on the magnetic mineral by utilizing a scanning electron microscope and an energy spectrum analyzer; s5, identifying ferrite magnetic minerals in the surface sediment by using X-ray diffraction; and S6, drawing a low-temperature chi-T curve, a high-temperature chi-T curve and a hysteresis loop to determine the type of the ferrite magnetic minerals. The magnetic minerals such as Fe3O4 and Fe2O3 in the surface sediments in the floating rice planting area can be simply, conveniently, quickly, efficiently and accurately extracted and detected.

Description

Technical Field

[0001] The invention relates to the technical field of environmental monitoring and geological exploration, and in particular to a method for extracting and detecting magnetic minerals in surface sediments of a floating rice planting area. Background Art

[0002] In the fields of environmental monitoring, geological research and resource exploration, magnetic minerals such as Fe3O4 and Fe2O3 in surface sediments play a vital role. As key information carriers, they provide rich clues to geological processes and environmental pollution conditions. In recent years, floating rice planting technology has been used as an innovative model to achieve the suspended growth of rice on the water surface through advanced means such as floating beds, floating islands, and floating boards. This technology is particularly suitable for ecological restoration of coal mining subsidence areas and effectively responds to the unique challenges faced by this area. However, the sediments in coal mining subsidence areas are often rich in magnetic minerals such as Fe3O4 and Fe2O3. These minerals not only reflect the regional geological characteristics, but may also be accompanied by heavy metal pollution, posing a potential threat to the safety of floating rice planting. Therefore, in order to ensure the cleanliness and safety of the floating rice planting environment in coal mining subsidence areas, a detection method that can accurately monitor magnetic minerals such as Fe3O4 and Fe2O3 in sediments and their adsorption of heavy metals is urgently needed.

[0003] At present, although there are magnetic mineral extraction technologies, these methods are generally cumbersome and inefficient, and are easily interfered by various factors in practical applications, resulting in inaccurate or biased test results. In view of this, it is particularly important to develop a simple, fast, efficient and accurate Fe3O4 and Fe2O3 and other magnetic mineral extraction and detection technology, which will provide strong technical support for the treatment of heavy metal pollution in coal mining surface subsidence areas, ensure the ecological environment quality of floating rice planting areas, and promote the sustainable development of the ecological economy in the region. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for extracting and detecting magnetic minerals in surface sediments of floating rice planting areas, which can simply, quickly, efficiently and accurately extract and detect magnetic minerals such as Fe3O4 and Fe2O3 in surface sediments of floating rice planting areas.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a method for extracting and detecting magnetic minerals in surface sediments of a floating rice planting area, comprising the following steps:

[0006] Step S1: collecting surface sediments from the floating rice planting area, and fully dispersing the surface sediment samples on paper;

[0007] Step S2: Wrap the super-strong magnetite with a plastic film and suspend it above the sediment sample for repeated adsorption;

[0008] Step S3: placing the adsorbed particles back into clean water and repeatedly magnetically separating them four to six times to further purify the magnetic minerals;

[0009] Step S4: pre-treating the obtained magnetic mineral sample, and identifying the iron and oxygen elements of the magnetic mineral using a scanning electron microscope and an energy spectrum analyzer;

[0010] Step S5: using X-ray diffraction to identify ferromagnetic minerals in surface sediments;

[0011] Step S6: Draw low-temperature and high-temperature χ-T curves and hysteresis loops to determine the type of ferromagnetic minerals.

[0012] In a preferred embodiment of the present invention, the specific steps of step S1 include:

[0013] S101: Use a mud sampler to collect surface sediments from the floating rice planting area, use a plastic spoon to take the top 0-5 cm of sediment, use the mixed sampling method, put the sample into a polyethylene bag, and store it at low temperature;

[0014] S102: Remove animal and plant remains and large gravel impurities, and freeze-dry the samples for 48 hours;

[0015] S103: Grind in a mortar, pass through a 100-mesh nylon sieve, put into a dry ziplock bag, and store in a desiccator for testing.

[0016] In a preferred embodiment of the present invention, in step S2, the magnetite does not come into direct contact with the sediment during magnetic separation, but remains suspended 2 to 3 cm above the sediment sample.

[0017] In a preferred embodiment of the present invention, in step S4, the step of pre-treating the magnetic mineral sample comprises:

[0018] S401: evenly take out a small amount of the extracted magnetic minerals and place them on a glass slide, and use a polyethylene sheet to cut the samples into a straight line;

[0019] S402: Use conductive glue or silver paste to fix the sample to ensure the stability of the sample, and ensure that the sample surface is clean and the structure is intact during sample handling and preparation;

[0020] S403: The sediment sample is subjected to gold spraying treatment to eliminate charge accumulation.

[0021] In a preferred embodiment of the present invention, in step S4, the iron and oxygen elements of the magnetic minerals are identified using a FEIQuanta 250FEG scanning electron microscope and an AZtec X-Max 80 energy spectrometer.

[0022] The beneficial effects of the present invention are as follows: the present invention can simply, quickly, efficiently and accurately extract and detect magnetic minerals such as Fe3O4 and Fe2O3 in surface sediments in floating rice planting areas, provide powerful technical support for the treatment of heavy metal pollution in surface subsidence and waterlogging areas caused by coal mining, ensure the ecological environment quality of the "floating rice planting area", and promote the sustainable development of the ecological economy in the region. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic flow chart of a method for extracting and detecting magnetic minerals in surface sediments of a floating rice planting area according to the present invention;

[0024] Figure 2 are scanning electron microscope and energy spectrum images of the sediment samples shown;

[0025] Figure 3 is the X-ray diffraction pattern of the sediment sample shown;

[0026] Figure 4 is the temperature-dependent magnetic susceptibility (χ-T) curve of a representative sample of surface sediments;

[0027] Figure 5 is the low temperature magnetic measurement curve of a representative sample of surface sediments;

[0028] Figure 6 It is the hysteresis loop curve of the representative sample of surface sediment. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0030] See also Figure 1 , the embodiment of the present invention includes:

[0031] A method for extracting and detecting magnetic minerals in surface sediments of a floating rice planting area comprises the following steps:

[0032] Step S1: Collect surface sediments from the "floating rice" planting area and fully disperse the surface sediment samples on paper; the specific steps are:

[0033] First, the surface sediments of the lake bottom in the floating rice planting area were collected using a Peterson surface sediment sampler. In particular, a plastic spoon was used to take the top 0-5 cm of sediment to ensure that the sample was representative. Using the mixed sampling method, the samples were placed in polyethylene bags and stored under low temperature conditions to prevent the samples from deteriorating or contaminating. Then, impurities such as animal and plant remains, large pieces of gravel, etc. were removed from the samples to ensure the smooth progress of subsequent steps. 200g of the treated sample was freeze-dried for 48 hours to remove moisture from the sample. The freeze-dried sample was ground using an agate mortar and passed through a 100-mesh nylon sieve to obtain uniform and fine particles. The ground sample was placed in a dry ziplock bag and stored in a desiccator for testing.

[0034] Step S2: Wrap a small square piece of super-strong magnetite with a plastic film and suspend it above the sediment sample for repeated adsorption, aiming to extract the magnetic minerals and remove the non-magnetic impurities therein;

[0035] The specific operation method is to use a small square super-strong magnetite and wrap it with plastic film to prevent direct contact with the sediment. The magnetite is suspended slightly above the sediment sample 2 to 3 cm, and repeated adsorption operations are performed to extract magnetic minerals in the sample. In particular, the magnetite does not come into direct contact with the sediment to maintain a certain distance to prevent strong electromagnetic minerals from being magnetically selected.

[0036] Step S3: placing the adsorbed particles back into clean water and repeatedly magnetically separating them four to six times to further purify the magnetic minerals;

[0037] Step S4: Pre-treat the sample and identify the elements such as Fe and O in the magnetic minerals using a FEIQuanta 250FEG scanning electron microscope and an AZtec X-Max 80 energy dispersive spectrometer;

[0038] The pre-treatment steps include: 1. Take out a small amount of the extracted magnetic minerals evenly and place them on a glass slide, and use a polyethylene sheet to divide the sample into a "one" line; 2. Use conductive glue or silver paste to fix the sample to ensure the stability of the sample. At the same time, during the sample processing and preparation process, you must wear a mask and nitrile gloves and ensure that the surface of the laboratory operating table is clean and tidy to avoid contamination and damage, and ensure that the sample surface is clean and the structure is intact; 3. Spray gold on the sediment sample to eliminate charge accumulation and avoid unclear imaging caused by charge accumulation during electron beam scanning. Among them, the gold spraying treatment is usually carried out in a special gold spraying equipment, and the vacuum degree and gold spraying time are set.

[0039] The operation of the scanning electron microscope should be strictly followed in accordance with the operating manual of the scanning electron microscope and the energy spectrum analyzer to avoid equipment damage or data distortion caused by misoperation. The specific steps are: 1. Turn on the power switch and the preparation switch of the scanning electron microscope, wait for the equipment to preheat to a stable state, and ensure that the electron gun and the detector reach the best working state. 2. Open the vacuum chamber door, place the sample on the sample stage, close the vacuum chamber door, and start the vacuum pump to evacuate until the required vacuum degree is reached. 3. For the observation of magnetic minerals, a lower acceleration voltage is usually required to obtain better surface morphology information. The scanning electron microscope parameters are set to a voltage of 15kV and an aperture of 60Aperture. 4. Perform preliminary focus and positioning at low magnification, and then gradually increase the magnification, using the coarse and fine adjustment mechanisms to ensure a clear image. At the same time, in the backscattering mode, increase the brightness to 90% and adjust the contrast to 50%. 5. Under the optimal imaging conditions, capture and save the scanning electron microscope image of the sample.

[0040] The specific operating steps of the energy spectrum analyzer are as follows: 1. Turn on the power switch and software interface of the energy spectrum analyzer to perform initialization settings. 2. Select the area on the scanning electron microscope image that needs to be analyzed by energy spectrum. 3. During the scanning electron microscope image collection process, multiple images are collected for each sample to capture mineral features at different angles and different magnifications. During the energy spectrum surface scan data collection process, ensure that the equipment has been calibrated and perform data collection in accordance with standard operating procedures. 4. Start the data acquisition function of the energy spectrum analyzer and perform energy spectrum analysis on the selected area. 5. Process and analyze the collected energy spectrum data to determine the elemental composition and content in the sample. Usually, the energy spectrum analyzer will provide software tools for data decomposition and quantitative analysis.

[0041] Step S5: Using X-ray diffraction (XRD) to identify magnetic minerals such as Fe3O4 and Fe2O3 in surface sediments, including turning on the power of the equipment, putting in samples, setting scanning parameters, capturing and saving scanning electron microscope images, and performing energy spectrum analysis.

[0042] The detailed steps include: 1. Sample filling: load the dried powder sample into the XRD sample holder to ensure that the sample surface is flat and evenly filled. 2. Instrument calibration, power on and preheating: turn on the power switch of the X-ray diffractometer and wait for the equipment to preheat to a stable state. Wavelength calibration: ensure that the wavelength of the X-ray source is accurate, which is the basis for obtaining accurate diffraction data. Angle calibration: adjust the angle scanning system of the diffractometer to ensure the accuracy of the diffraction angle. Intensity calibration: calibrate the sensitivity of the detector to ensure that the measurement of the diffraction intensity is accurate and reliable. 3. Data collection, set test parameters: set the test parameters of the X-ray diffractometer, such as scanning range, scanning speed, step length, etc. according to the sample characteristics and analysis requirements. For the analysis of magnetic mineral components, it is usually necessary to select a wider scanning range to cover possible diffraction peaks. Place the sample: place the sample holder with the sample on the sample stage of the X-ray diffractometer, and adjust the sample position to ensure that the X-ray can be correctly irradiated on the sample. Start the test: start the X-ray diffractometer for testing. During the test, the X-ray source emits X-rays to irradiate the sample, and the diffractometer records the angle and intensity information of the diffracted beam. 4. Data analysis, data collection and processing: After the test is completed, the diffraction spectrum data is collected. Use professional XRD analysis software to perform smooth curves, subtract background, find peaks and other processing steps on the spectrum to improve the accuracy and reliability of the data. Phase retrieval and identification: Comparison with standard spectrum: Compare the processed diffraction spectrum with the known standard spectrum library to identify the mineral phases present in the sample. The standard spectrum library usually contains diffraction spectrum data of various minerals and is the basis for phase identification. 5. Result interpretation and application, result interpretation: According to the results of phase retrieval and quantitative analysis, the magnetic mineral components and their contents in the sample are interpreted, which helps to understand the mineral composition and magnetic properties of surface sediments. Through the above steps and processes, XRD technology can be systematically used to identify the magnetic mineral components in surface sediments, providing strong support for scientific research and practical applications in the field of magnetic minerals in surface sediments.

[0043] Step S6: Draw low-temperature and high-temperature χ-T curves and hysteresis loops to determine the type of ferromagnetic minerals.

[0044] The specific operation includes: firstly, measuring the magnetization intensity of the sample, recording the data of magnetization intensity (M) and magnetic field intensity (H), and calculating the magnetic susceptibility (χ); then, arranging the calculated magnetic susceptibility data in temperature order to form a χ-T data table; finally, using the drawing software (Origin), using the magnetic susceptibility (χ) as the ordinate and the temperature (T) as the abscissa, drawing the low-temperature and high-temperature χ-T curves. Using the magnetization intensity / saturation magnetization intensity (M / Ms) as the ordinate and Field (T) as the abscissa, draw the hysteresis loop. The type of ferrite magnetic mineral is determined by the low-temperature and high-temperature χ-T curves and hysteresis loops.

[0045] The feasibility of the method of the present invention is described below with reference to examples.

[0046] like Figure 2 As shown, based on the scanning electron microscope images and energy spectrum analysis results, the magnetic mineral components in the surface sediments were identified and quantitatively analyzed. Most of the magnetic iron oxide particles are spherical or irregular in shape. The iron concentration of the magnetic particles in spectrum 10 is 63.1%, the oxygen concentration is 29.2%, and the carbon concentration is 7.7%. The iron concentration of the magnetic particles in spectrum 11 is 72.5%, the oxygen concentration is 16.0%, and the carbon concentration is 11.5%. EDX analysis shows that the iron concentration of these magnetic particles is 63.1-72.5%. The spherical particles may be produced during the combustion of fossil fuels, while the angular iron oxide particles containing C may come from automobile brakes or soil dust. These Fe elements are important factors in the generation of magnetic signals, making it possible to predict and simulate the heavy metal concentrations of the surface sediments in the floating rice planting area based on the magnetic characteristics.

[0047] like Figure 3 As shown in Figure 2, the X-ray diffraction patterns of the sediment samples show that the iron phase in the sediment exists mainly in the form of magnetite Fe3O4, mixed with hematite Fe2O3 in different proportions, and the ferrimagnetic phases are magnetite, hematite, maghemite and mafite. The diversity of magnetic iron phases in the sediments indicates that their sedimentary sources are different.

[0048] like Figure 4 As shown, magnetic minerals in sediment samples can be identified based on their temperature-dependent magnetic susceptibility (χ-T) cycles. The heating and cooling curves of the high-temperature χ-T measurement show a Curie temperature of about 580°C, indicating that Fe3O4 is the main contributor to the magnetization. At temperatures <580°C, the magnetization intensity in the cooling curve (shown in blue) is higher than that in the heating curve (shown in red), reflecting the formation of new Fe3O4 during heating. The slightly lower magnetic susceptibility of the sediment samples at 600-700°C indicates the presence of Fe2O3.

[0049] like Figure 5 As shown in Figure 1, the curve shows a trend of first decreasing, then increasing, and finally decreasing again. The low-temperature χ-T curve shows a clear Verwey transition at about 120K, which further proves the existence of Fe3O4.

[0050] like Figure 6As shown in the figure, the shape of the hysteresis loop can better indicate the type of magnetic minerals, and the field strength at the closure of the hysteresis loop can be used to indicate the magnetic minerals that dominate the hysteresis behavior. The Loop curve results of the representative sediment sample show that when a 0-0.2T magnetic field is applied, the magnetization intensity of the sample rises rapidly, indicating that the sample contains a large number of ferrimagnetic minerals with low coercivity. The curve is close to closing and tends to be smooth near 0.250T, and is completely closed near 1T, indicating that the sample is dominated by ferrimagnetic minerals and contains a small amount of antiferromagnetic minerals.

[0051] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0052] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for extracting and detecting magnetic minerals in surface sediments in a floating rice planting area, characterized in that: The following steps are involved: Step S1: collecting surface sediments from the floating rice planting area, and fully dispersing the surface sediment samples on paper; Step S2: Wrap the super-strong magnetite with a plastic film and suspend it above the sediment sample for repeated adsorption; Step S3: placing the adsorbed particles back into clean water and repeatedly magnetically separating them four to six times to further purify the magnetic minerals; Step S4: pre-treating the obtained magnetic mineral sample, and identifying the iron and oxygen elements of the magnetic mineral using a scanning electron microscope and an energy spectrum analyzer; Step S5: using X-ray diffraction to identify ferromagnetic minerals in surface sediments; Step S6: Draw low-temperature and high-temperature χ-T curves and hysteresis loops to determine the type of ferromagnetic minerals.

2. The method for extracting and detecting magnetic minerals in surface sediments of floating rice planting areas according to claim 1, characterized in that: The specific steps of step S1 include: S101: Use a mud sampler to collect surface sediments from the floating rice planting area, use a plastic spoon to take the top 0-5 cm of sediment, use the mixed sampling method, put the sample into a polyethylene bag, and store it at low temperature; S102: Remove animal and plant remains and large gravel impurities, and freeze-dry the samples for 48 hours; S103: Grind in a mortar, pass through a 100-mesh nylon sieve, put into a dry ziplock bag, and store in a desiccator for testing.

3. The method for extracting and detecting magnetic minerals in surface sediments of floating rice planting areas according to claim 1, characterized in that: In step S2, during magnetic separation, the magnetite does not come into direct contact with the sediment and is kept suspended 2 to 3 cm above the sediment sample.

4. The method for extracting and detecting magnetic minerals in surface sediments of floating rice planting areas according to claim 1, characterized in that: In step S4, the step of pre-treating the magnetic mineral sample includes: S401: evenly take out a small amount of the extracted magnetic minerals and place them on a glass slide, and use a polyethylene sheet to cut the samples into a straight line; S402: Use conductive glue or silver paste to fix the sample to ensure the stability of the sample, and ensure that the sample surface is clean and the structure is intact during sample handling and preparation; S403: The sediment sample is subjected to gold spraying treatment to eliminate charge accumulation.

5. The method for extracting and detecting magnetic minerals in surface sediments of floating rice planting areas according to claim 1, characterized in that: In step S4, the iron and oxygen elements of the magnetic minerals were identified using a FEIQuanta 250FEG scanning electron microscope and an AZtec X-Max 80 energy dispersive spectrometer.

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