A method for rapid measurement of the wettability of the surface of ore particles based on low-field nuclear magnetic resonance

Abstract

This invention discloses a method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance (NMR), belonging to the field of wettability measurement technology. This invention uses the seated drop method to test the contact angles of some energy, metallic, and non-metallic mineral particles, then obtains the T2 relaxation spectrum through low-field NMR testing, and finally obtains the T2 weighted average value T for different wetting times. 2g The value was calculated, and T was calculated for different wetting times. 2g The slope value k of the linear function was obtained by performing a linear quantitative fitting between the value and the wetting time. T2g Then k T2g k is obtained by performing a first-order linear fit with the corresponding mineral particle contact angle θ. T2g The relationship between the contact angle θ and the wettability of the mineral particles being tested is expressed as k. T2g The wettability of mineral particles is obtained from the relationship between the contact angle θ and the T2 weighted average value. The linear model established in this invention, which relates the slope of the wetting time fitting function to the contact angle, is accurate and reliable. It can complete the evaluation of the wettability of mineral particle surfaces in just 3 minutes, and has the advantages of being fast and efficient.

Description

Technical Field

[0001] This invention relates to a method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance, belonging to the field of wettability measurement technology. Background Technology

[0002] In the field of mineral separation technology, froth flotation has long been an effective means of enriching and recovering fine-grained minerals. The surface wettability of minerals has a crucial impact on their flotation effect. Generally, poor surface wettability results in good floatability, and coupled with the high adsorption efficiency of hydrocarbon reagents such as kerosene on the mineral surface, the flotation effect is better; conversely, poor surface wettability leads to poor floatability. Therefore, mineral surface wettability is closely related to its floatability, and accurate and rapid characterization of mineral surface wettability is of great significance and value for efficient mineral flotation and recovery.

[0003] Multiple mineral aggregates are generally called ores. The wettability of ores directly determines the hydrophilicity or hydrophobicity of mineral surfaces, which in turn affects the flotation effect. At present, scholars at home and abroad have proposed a variety of methods for characterizing the wettability of ore particle surfaces, including capillary permeation, seated drop method, surface energy and water film flotation methods. Among them, the seated drop method is the most commonly used method in the laboratory to evaluate the wettability of mineral particle surfaces. Mineral particles ground to a specified particle size are pressed into tablets, and the wettability of mineral surfaces is evaluated by the contact angle formed by water droplets on the surface of the tablets. However, this method has the following drawbacks: (1) Since the ore needs to be ground to a specified particle size, the measurement results cannot reflect the wettability of the ore at its original particle size, resulting in a certain degree of distortion in the measurement results. (2) Ore particle grinding, pressing, and characterization often require multiple equipment and a long time, resulting in low measurement efficiency of the seated drop method. (3) Some ore particles have poor adhesion and are difficult to press into tablets, so the seated drop method cannot be used to measure their contact angle. The capillary permeation method requires a constant and uniform particle packing during measurement, and the degree of particle compaction significantly affects the results. Surface energy characterization of particle wettability is time-consuming, and its accuracy requires further investigation. Water film flotation methods can only provide reference results with low reliability. To address the shortcomings of existing wettability characterization methods, there is an urgent need to propose a rapid, non-destructive, accurate, and adaptable method for characterizing the surface wettability of ore particles. Summary of the Invention

[0004] In order to overcome the problems in the background art, the purpose of this invention is to provide a method for rapid measurement of the surface wettability of mineral particles based on low-field nuclear magnetic resonance, which can be adapted to various types of ores, and solves the problems of difficulty in pressing mineral particles into tablets, long detection time, poor adaptability and damage to the original particle size of mineral particles in the process of measuring the wettability of mineral particles by existing techniques such as the seat drop method.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance includes the following steps:

[0007] (1) Selected energy ores, metal ores and non-metal ores were crushed and ground separately, then mixed with boric acid and pressed into tablets. The contact angle of the above ores was measured by the seat drop method.

[0008] (2) The above-mentioned ore particles are pre-dried to remove the free water contained inside the ore;

[0009] (3) Water was injected into the dried mineral particles, and then sealed. Low-field nuclear magnetic resonance tests were performed at 0.5 min, 1 min, 3 min, 5 min, and 10 min after wetting with water. T2 relaxation spectra at different wetting times were collected. Then, the T2 weighted average value of the T2 relaxation spectra at different wetting times was calculated. 2g value;

[0010] (4) T at different wetting times 2g The slope value k of the linear function was obtained by performing a linear quantitative fitting between the value and the wetting time. T2g ;

[0011] (5) The k of each mineral particle T2g k is obtained by performing a first-order linear fit with the corresponding mineral particle contact angle θ. T2g The relationship between the contact angle θ and the contact angle θ;

[0012] (6) The wettability of the mineral particles to be tested was subjected to low-field nuclear magnetic resonance (NMR) tests at 0.5 min, 1 min, 3 min, 5 min, and 10 min after wetting with injected water to obtain T2 relaxation spectra at different wetting times. The T2 weighted average value was used to calculate the T2 relaxation time at different wetting times. 2g Value, establish T 2g The linear functional relationship between the value and wetting time was established, and the slope value k was obtained. T2g The slope value k T2g Substitute k T2g The relationship between the contact angle θ and the wettability of mineral particles is obtained.

[0013] Preferably, energy minerals are natural deposits found on or beneath the earth's surface, formed by geological processes, existing in solid, gaseous, or liquid states, and possessing practical or potential energy value. The energy ores are solid energy minerals. Metallic ores refer to minerals from which metallic elements can be extracted after mining. Non-metallic ores, in contrast to metallic ores, comprise 91 types, primarily graphite, fluorite, dolomite, quartz, and phosphate rock.

[0014] More preferably, the energy ore is lignite, gas coal, or anthracite, the metallic ore is malachite, and the non-metallic ore is phosphate rock.

[0015] Preferably, in step (3), the mass-to-volume ratio of the dried mineral particles to water is 3-6g:0.5-1ml.

[0016] Preferably, T under different wetting times 2g The formula for calculating the value is:

[0017]

[0018] Among them, T 2g The T2 weighted average, T 2i Let T2 be the relaxation time at point i, and A be the relaxation time at point i. i Let A be the signal amplitude at point i corresponding to T2, and let A be the total signal amplitude of T2.

[0019] Preferably, the k T2g The relationship between the contact angle θ and the contact angle is:

[0020] θ = 31.1492 × k T2g +150.1447 (2);

[0021] In the formula, θ is the contact angle of the mineral particles, and k T2g The slope of a linear function is obtained by fitting the weighted average T2 value of mineral particles to the wetting time.

[0022] Preferably, in the low-field nuclear magnetic resonance test, the magnetic type is a permanent magnet, the resonance frequency is 12MHz, the magnetic field strength is 0.3±0.05T, the diameter of the nuclear magnetic resonance probe coil is 25mm, the magnet temperature is controlled at 32±0.1℃ during the nuclear magnetic resonance test, the pulse sequence is CPMG, the echo time is 0.1ms, the number of samplings is 32, the resampling waiting time is 6000ms, and the number of echoes is 18000.

[0023] The beneficial effects of this invention are:

[0024] (1) The method for surface wettability of ore particles described in this invention has a wide range of applicable ores and can be used to characterize the surface wettability of ore particles such as energy minerals (e.g., coal), non-metallic minerals and metallic minerals. Before testing, there is no need to press the ore particles into tablets, so as not to break the original particle size of the ore particles and avoid the influence of heterogeneity such as surface roughness and pore structure of the ore particles.

[0025] (2) The linear model between the T2 weighted average value and the slope of the wetting time fitting function established by this invention and the contact angle is accurate and reliable. It only takes 3 minutes to complete the evaluation of the wettability of mineral particles, which has the advantages of being fast and efficient.

[0026] (3) The low-field nuclear magnetic resonance equipment used in this invention can complete the test quickly without damaging the ore, avoiding the problem of distortion of wettability test results caused by the seat drop method, and truly achieving non-destructive testing. At the same time, the equipment also has the advantages of safety, low cost and easy operation. Attached Figure Description

[0027] Figure 1 The contact angle, T2 spectrum, and T2 spectrum of malachite in Example 1 are shown. 2g The fitting results with wetting time are shown in the figure, where (a) is the contact angle and T2 spectrum of malachite; (b) is the T2 spectrum. 2g The fitting results with wetting time are shown in the figure.

[0028] Figure 2 The contact angle, T2 spectrum, and T2 spectrum of lignite in Example 1 are shown. 2g The fitting results with wetting time are shown in the figure, where (a) is the contact angle and T2 spectrum of lignite; (b) is the T2 spectrum of lignite. 2g The fitting results with wetting time are shown in the figure.

[0029] Figure 3 The contact angle, T2 spectrum, and T2 spectrum of collophane in Example 1 are shown. 2g The fitting results with wetting time are shown in the figure, where (a) is the contact angle and T2 spectrum of collophane; (b) is the T2 spectrum of collophane. 2g The fitting results with wetting time are shown in the figure.

[0030] Figure 4 The contact angle, T2 spectrum, and T2 spectrum of the gas coal in Example 1 are shown. 2g The fitting results with wetting time are shown in the figure, where (a) is the contact angle and T2 spectrum of the gas coal; (b) is the T2 spectrum. 2g The fitting results with wetting time are shown in the figure.

[0031] Figure 5 The contact angle, T2 spectrum, and T2 spectrum of the anthracite in Example 1 are shown. 2g The fitting results with wetting time are shown in the figure, where (a) is the contact angle and T2 spectrum of anthracite; (b) is the T2 spectrum of anthracite. 2g The fitting results with wetting time are shown in the figure.

[0032] Figure 6 The contact angles of malachite, lignite, phosphate rock, gas coal, and anthracite with respect to T 2g -t function slope K T2g Quantitative relationship diagram. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] All chemical reagents not described in the embodiments and comparative examples of this invention were commercially available analytical grade reagents used in the experiments.

[0035] Example 1

[0036] A method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance includes the following steps:

[0037] a. Lignite, gas coal, and anthracite were selected as representative energy ores, while malachite and phosphate rock were selected as representative metallic and non-metallic ores, respectively. These ores were crushed and ground to below 74 μm. The particles were then compressed into tablets using a tableting machine and boric acid (the mass ratio of boric acid to particles was approximately 1:3). The contact angle of each ore was then characterized using the seated drop method. Figure 1 (a)-5(a) is shown.

[0038] b. Weigh 3g of each of the above-mentioned mineral particles (lignite, gas coal, anthracite, malachite, and phosphate rock), place them in a vacuum drying oven for pre-drying to remove the free water contained inside, and then place them in chromatographic bottles. After placing the chromatographic bottles in a nuclear magnetic resonance (NMR) measuring cylinder, perform NMR testing to ensure that the free water contained inside the mineral particles has been removed through drying.

[0039] c. Using a microsyringe, add 0.5 mL of distilled water to each of the dried mineral particles. Seal the chromatographic bottle and place it in a graduated cylinder. Perform low-field nuclear magnetic resonance (NMR) tests after adding the mineral particles to the distilled water for 0.5, 1, 3, 5, and 10 minutes, respectively. In this embodiment, the equipment used to characterize the T2 relaxation spectrum of the mineral particles is an NMRC12-010V low-field NMR nanopore analyzer manufactured by Suzhou Newmai Technology Co., Ltd. The single NMR test time is 3 minutes. The parameters for the low-field NMR test are: permanent magnet, resonance frequency of 12 MHz, magnetic field strength of 0.3 ± 0.05 T, probe coil diameter of 25 mm, magnet temperature controlled at 32 ± 0.1 ℃ during the NMR test, pulse sequence of CPMG, echo time of 0.1 ms, number of samples of 32, resampling waiting time of 6000 ms, and echo number of 18000.

[0040] d. In the low-field nuclear magnetic resonance testing project, T2 relaxation spectra were collected and calculated after distilled water was added to the mineral particles at different times, such as... Figure 1 As shown in (a)-5(a), each test takes 3 minutes, and then the T2 weighted average is calculated using the formula. Analysis of T under different wetting times 2g Value, where T 2i Let T2 be the relaxation time at point i, and A be the relaxation time at point i. i Let A be the signal amplitude at point i corresponding to T2, and let A be the total signal amplitude of T2.

[0041] e. Using the plotting and analysis software Origin 9.0, the T values ​​of the mineral particles after being wetted with distilled water for different times were analyzed. 2g A linear quantitative fitting was performed between the value and wetting time, and the slope value k of the linear function was analyzed. T2g ,like Figure 1 As shown in (b)-5(b); k 2g =k T2g *t+a, in this embodiment, malachite: k T2g = -3.8050, a = 282.6698, R 2 =0.9939. Lignite: kJ T2g = -3.7498, a = 179.4672, R 2 =0.9974. Phosphate: k T2g = -3.6373, a = 183.7846, R 2 =0.9988. Gas coal: kJ T2g =-2.0627, a=167.0392, R 2 =0.9989. Anthracite: kJ T2g = -0.9528, a = 244.9356, R 2 =0.9976.

[0042] f. Calculate the k value of the above-mentioned ore based on nuclear magnetic resonance testing. T2g A first-order linear fit was performed on the contact angle with the aforementioned ore to obtain k. T2g The relationship between the contact angle θ and the contact angle is: θ = 31.1492 × k T2g +150.1447, the goodness of fit R² is 0.9896, as shown. Figure 6 As shown, this indicates that k T2g There is a good linear relationship between it and the contact angle θ.

[0043] g. Place the chromatographic vial containing the wettable mineral particles to be tested (chalcopyrite, chalcopyrite, long-flame coal, coking coal, or quartz) into an NMR measuring cylinder. Perform the test under the NMR conditions specified in this invention (wetting times of 0.5, 1, 3, 5, and 10 min) and in step c. The test time is 3 min. Calculate the T2 weighted average value T from the T2 relaxation spectrum. 2g Value, establish T 2g The linear functional relationship between the value and wetting time is investigated, and the slope value k in the relationship is analyzed. T2g The slope value k T2g The wettability of mineral particles can be obtained by substituting the first-order linear equation established in this invention, and the results are shown in Table 1.

[0044] The contact angle of mineral particles was measured using the seated drop method, such as Figure 1As shown in (a)-5(a); in this embodiment, the contact angles of malachite, lignite, phosphate rock, gas coal, and anthracite are 33.68°, 34.72°, 35.50°, 80.39°, and 123.88°, respectively; Figure 1 As shown in (b)-5(b); k 2g =k T2g *t+a, in this embodiment, malachite: k T2g = -3.8050, R 2 =0.9939. Lignite: kJ T2g = -3.7498, R 2 =0.9974. Phosphate: k T2g = -3.6373, R 2 =0.9988. Gas coal: kJ T2g = -2.0627, R 2 =0.9989. Anthracite: kJ T2g = -0.9528, R 2 =0.9976. For example... Figure 6 As shown, k T2g The relationship between the contact angle θ and the contact angle is: θ = 31.1492 × k T2g The result was +150.1447, with a good fit R² of 0.9896, indicating high accuracy.

[0045] Table 1

[0046]

[0047]

[0048] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance, characterized in that: Includes the following steps: (1) Selected energy ores, metal ores and non-metal ores were crushed and ground separately, then mixed with boric acid and pressed into tablets. The contact angle of the mineral particles was then measured by the seat drop method. (2) The above-mentioned mineral particles are pre-dried to remove the free water contained inside the mineral particles; (3) Water was injected into the dried mineral particles, and then the particles were sealed. Low-field nuclear magnetic resonance tests were performed 0.5 min, 1 min, 3 min, 5 min, and 10 min after wetting with water. T2 relaxation spectra were collected at different wetting times. Then, the T2 weighted average value T of the T2 relaxation spectra at different wetting times was calculated. 2g value; (4) T under different wetting times 2g The slope value k of the linear function was obtained by performing a linear quantitative fitting between the value and the wetting time. T2g ; (5) The k of each mineral particle T2g k is obtained by performing a first-order linear fit with the corresponding mineral particle contact angle θ. T2g The relationship between the contact angle θ and the contact angle θ; (6) The wettability of the mineral particles to be tested was subjected to low-field nuclear magnetic resonance (NMR) tests at 0.5 min, 1 min, 3 min, 5 min, and 10 min after wetting with injected water to obtain T2 relaxation spectra at different wetting times. The T2 weighted average value was used to calculate the T2 relaxation time at different wetting times. 2g Value, establish T 2g The linear functional relationship between the value and wetting time was established, and the slope value k was obtained. T2g The slope value k T2g Substitute k T2g The relationship between the contact angle θ and the wettability of mineral particles is obtained.

2. The method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance according to claim 1, characterized in that: The energy minerals are lignite, gas coal, and anthracite; the metallic mineral is malachite; and the non-metallic mineral is phosphate rock.

3. The method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance according to claim 1, characterized in that: In step (3), the mass-to-volume ratio of the dried mineral particles to water is 3-6g:0.5-1ml.

4. The rapid characterization method for surface wettability of mineral particles based on low-field nuclear magnetic resonance according to claim 1, characterized in that: T under different wetting times 2g The formula for calculating the value is: （1）； Among them, T 2g The T2 weighted average, T 2i Let T2 be the relaxation time at point i, and A be the relaxation time at point i. i Let A be the signal amplitude at point i corresponding to T2, and let A be the total signal amplitude of T2.

5. The method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance according to claim 2, characterized in that: The k T2g The relationship between the contact angle θ and the contact angle is: （2）； In the formula, θ is the contact angle of the mineral particles, and k T2g The slope of a linear function is obtained by fitting the weighted average T2 value of mineral particles to the wetting time.

6. The method for rapid measurement of mineral particle surface wettability based on low-field nuclear magnetic resonance according to claim 1, characterized in that: In the low-field nuclear magnetic resonance (NMR) test, the magnetic type is a permanent magnet, the resonance frequency is 12 MHz, the magnetic field strength is 0.3±0.05T, the diameter of the NMR probe coil is 25 mm, the magnet temperature is controlled at 32±0.1 ℃ during the NMR test, the pulse sequence is CPMG, the echo time is at least 0.1 ms, the number of samples is at least 32, the resampling waiting time is at least 6000 ms, and the number of echoes is at least 18000.

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