Method for rapidly measuring surface wettability of ore grains based on low-field nuclear magnetic resonance

Abstract

The invention discloses a method for rapidly measuring the surface wettability of ore grains based on low-field nuclear magnetic resonance, and belongs to the technical field of wettability measurement. According to the method, contact angles of part of energy, metal and non-metal ore particles are respectively tested through a seat drop method, then a T2 relaxation spectrum is obtained through a low-field nuclear magnetic resonance test, then a T2 weighted average value T2g value at different wetting times is obtained, linear quantitative fitting is carried out on the T2g value at different wetting times and the wetting time, and the wetting time is calculated. Obtaining a slope value kT2g of the linear function; performing first-order linear fitting on the kT2g and a corresponding ore grain contact angle theta to obtain a relational expression between the kT2g and the contact angle theta, and obtaining the wettability of the to-be-measured wettability ore grains through the relational expression between the kT2g and the contact angle theta. The linear model between the slope value and the contact angle of the T2 weighted average and wetting time fitting function established by the method is accurate and reliable, the evaluation of the surface wettability of the ore grains can be completed in only 3 minutes, and the method has the advantages of rapidness, high efficiency and the like.

Description

Technical Field

[0001] The invention relates to a method for quickly measuring the wettability of mineral particle surfaces based on low-field nuclear magnetic resonance, and belongs to the technical field of wettability measurement. Background Art

[0002] In the field of mineral separation technology, froth flotation has always been an effective means of enriching and recovering fine-particle minerals, and the surface wettability of minerals has a crucial impact on their flotation effect. Usually, the poor surface wettability of minerals leads to good floatability. In addition, hydrocarbon agents such as kerosene have high adsorption efficiency on the mineral surface, which makes the mineral flotation effect better; otherwise, it is poor. It can be seen that the surface wettability of minerals is closely related to their floatability. Accurate and rapid characterization of the surface wettability of minerals will be of great significance and value to the efficient flotation recovery of minerals.

[0003] Aggregates of various minerals are usually called ores. The wettability of ores directly determines the hydrophilicity of the mineral surface, which in turn affects the flotation effect of the mineral. At present, scholars at home and abroad have proposed a variety of methods for characterizing the surface wettability of ore particles, mainly including capillary permeation method, sessile drop method, surface energy and water film flotation method, among which the sessile drop method is the most commonly used method in the laboratory to evaluate the surface wettability of ore particles. The ore particles ground to a specified particle size are pressed into tablets, and the contact angle formed by water droplets on the surface of the formed tablets is used to evaluate the surface wettability of the mineral. However, this method has the following disadvantages: (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 certain distortion in the measurement results. (2) The grinding, pressing and characterization of ore particles often require multiple equipment and a long time, resulting in low measurement efficiency of the sessile drop method. (3) Some ore particles have poor adhesion and are difficult to be pressed into tablets, so their contact angles cannot be measured using the sessile drop method. The capillary permeability method requires that the filling of mineral particles be kept constant and uniform during the measurement process, and the degree of compaction of mineral particles has a great influence on the measurement results. It takes a long time to characterize the wettability of mineral particles by surface energy, and its measurement accuracy needs further study. The results of wettability measurement by water film flotation method can only be used as a reference and have low credibility. In view of the shortcomings of the above-mentioned existing wettability characterization methods, it is urgent to propose a fast, 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 technology, the purpose of the present invention is to provide a method for quickly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance, which can be adapted to a variety of ore types to solve the problems of difficulty in pressing and forming mineral particles, long detection time, poor adaptability and destruction of the original particle size of ore particles in the process of measuring the wettability of ore particles by existing technologies such as the sessile drop method.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0006] A method for rapidly measuring the wettability of mineral particle surfaces based on low-field nuclear magnetic resonance comprises the following steps:

[0007] (1) Selecting some energy ores, metal ores and non-metallic ores, crushing and grinding them respectively, mixing them with boric acid and pressing them into tablets, and then measuring the contact angles of the above ores respectively by using the sessile drop method;

[0008] (2) pre-drying the above-mentioned ore particles to remove free water contained in the ore;

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

[0010] (4) T under different wetting times 2g The linear quantitative fitting of the value and the wetting time was performed to obtain the slope value k of the linear function. T2g ;

[0011] (5) The k of each mineral particle T2g The first-order linear fitting is performed with the corresponding contact angle θ of the mineral particles to obtain k T2g The relationship between the contact angle θ:

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

[0013] Preferably, energy minerals are natural enrichments that exist on the surface or underground, are formed by geological processes, are in solid, gaseous and liquid states, and have energy value that provides practical or potential significance. The energy ore is a solid energy mineral. The metal ore refers to a mineral from which metal elements can be extracted after mining. The non-metallic ore is relative to the metal ore, and there are 91 types, mainly graphite, fluorite, dolomite, quartz, phosphate rock, etc.

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

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

[0016] Preferably, T under different wetting times 2g The value is calculated as

[0017]

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

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

[0020] θ=31.1492×k T2g +150.1447 (2);

[0021] Where θ is the contact angle of the mineral particles, k T2g The slope value of the linear function fitted between the weighted average value of mineral particle T2 and wetting time.

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

[0023] Beneficial effects of the present invention:

[0024] (1) The method for measuring the surface wettability of ore particles of the present invention is applicable to a wide range of ores, and can be used to characterize the surface wettability of ore particles of energy minerals (such as coal), non-metallic minerals, and metal minerals. Before testing, the ore particles do not need to be pressed into tablets, and the original particle size of the ore particles is not crushed, thereby avoiding the influence of heterogeneity such as the surface roughness and pore structure of the ore particles.

[0025] (2) The linear model between the slope value of the T2 weighted average value and the wetting time fitting function and the contact angle established in the present invention 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 the present invention can quickly complete the test without destroying the ore, avoiding the problem of distorted wettability test results caused by the sessile drop method, and is truly non-destructive. At the same time, the equipment also has the advantages of safety, low cost, and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0032] Figure 6 The contact angles of malachite, lignite, collophanite, gas coal and anthracite and T 2g -t function slope K T2g Quantitative relationship diagram. DETAILED DESCRIPTION

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

[0034] All chemical reagents not specified in the examples and comparative examples of the present invention were commercially available analytically pure for experiments.

[0035] Example 1

[0036] A method for rapidly measuring the wettability of mineral particle surfaces based on low-field nuclear magnetic resonance comprises the following steps:

[0037] a. Select lignite, gas coal and anthracite as representative ores of energy, malachite and collophanite as representative ores of metal and non-metal, respectively. Crush and grind the above ores to less than 74 μm, press the ore particles with the help of a tablet press and boric acid (the mass ratio of boric acid to ore particles is about 1:3), and then use the sessile drop method to characterize the contact angles of the above ores, such as Figure 1 (a)-5(a) is shown.

[0038] b. Weigh 3g of the above-mentioned ore particles (lignite, gas coal, anthracite, malachite, collophanite) respectively, put them into a vacuum drying oven for pre-drying to remove the free water contained inside, and then put them into chromatographic bottles respectively. The chromatographic bottles are placed in nuclear magnetic resonance test cylinders and then nuclear magnetic resonance tests are performed to ensure that the free water contained in the ore particles is removed by drying.

[0039] c. Add 0.5 mL of distilled water to the dried mineral particles with the help of a micro-syringe, seal the chromatographic bottle and put it into a measuring cylinder, and perform low-field nuclear magnetic resonance test after adding distilled water to the mineral particles 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 the NMRC12-010V low-field nuclear magnetic nanopore analyzer produced by Suzhou Newmai Technology Co., Ltd. The single nuclear magnetic test time is 3 minutes, and the parameters of the low-field nuclear magnetic resonance test are as follows: the magnetic type is a permanent magnet, the resonance frequency is 12 MHz, the magnetic field strength is 0.3 ± 0.05 T, the diameter of the nuclear magnetic probe coil is 25 mm, the magnet temperature is controlled at 32 ± 0.1 ° C during the nuclear magnetic test, the pulse sequence is CPMG, the echo time is 0.1 ms, the number of sampling times is 32, the repeated sampling waiting time is 6000 ms, and the number of echoes is 18000.

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

[0041] e. Using the drawing analysis software Origin 9.0, the T 2g The linear quantitative fitting of the value and the wetting time was performed to analyze the slope value k of the linear function. T2g ,like Figure 1 (b)-5(b); k 2g =k T2g *t+a, in this example, malachite: k T2g =-3.8050, a = 282.6698, R 2 =0.9939. Lignite: k T2g =-3.7498, a = 179.4672, R 2 =0.9974. Collophanite: k T2g =-3.6373, a = 183.7846, R 2 =0.9988. Gas coal: k T2g =-2.0627, a = 167.0392, R 2 =0.9989. Anthracite: k T2g =-0.9528, a = 244.9356, R 2 =0.9976.

[0042] f. Calculate the k of the above ore by nuclear magnetic test T2g A first-order linear fit is performed with the contact angle of the above ore to obtain k T2g The relationship between the contact angle θ is: θ = 31.1492 × k T2g +150.1447, the fitting degree R2 is 0.9896, such as Figure 6 This indicates that k T2g There is a good linear relationship between the contact angle θ.

[0043] g. Place the chromatographic bottle containing the wettability ore particles to be tested (chrysocolla, chalcopyrite, long flame coal, coking coal or quartz) into a nuclear magnetic resonance test cylinder, and test under the nuclear magnetic resonance conditions specified in step c under the wetting time of 0.5, 1, 3, 5, and 10 min specified in the present invention. The test time is 3 min, and the T2 weighted average value T is calculated from the T2 relaxation spectrum. 2g value, establish T 2g The linear function relationship between the value and the wetting time, and the slope value k in the relationship is analyzed T2g , the slope value k T2g Substituting the first-order linear equation established in the present invention into the equation, the wettability of the mineral particles can be obtained. The results are shown in Table 1.

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

[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 rather than 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 in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance, characterized in that: The following steps are involved: (1) Selecting some energy ores, metal ores and non-metallic ores, crushing and grinding them respectively, mixing them with boric acid and pressing them into tablets, and then measuring the contact angles of the above ores respectively by using the sessile drop method; (2) pre-drying the above-mentioned ore particles to remove free water contained in the ore; (3) Water was injected into the dried mineral particles, and then the particles were sealed and low-field nuclear magnetic resonance tests were performed 0.5 min, 1 min, 3 min, 5 min, and 10 min after the water injection. T2 relaxation spectra at different wetting times were collected, and then the T2 weighted average values ​​T at different wetting times were calculated based on the T2 relaxation spectra. 2g value; (4) T under different wetting times 2g The linear quantitative fitting of the value and the wetting time was performed to obtain the slope value k of the linear function. T2g ; (5) The k of each ore particle T2g The first-order linear fitting is performed with the corresponding contact angle θ of the mineral particles to obtain k T2g The relationship between the contact angle θ: (6) The wettability of the mineral particles to be tested was tested by low-field nuclear magnetic resonance at 0.5 min, 1 min, 3 min, 5 min, and 10 min after water injection to obtain T2 relaxation spectra at different wetting times. The T2 weighted average value at different wetting times was calculated. 2g value, establish T 2g The linear function relationship between the value and the wetting time and the slope value k is obtained T2g , the slope value k T2g Substitute k T2g The relationship between the contact angle θ and the wettability of the mineral particles is obtained.

2. The method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance according to claim 1, characterized in that: The energy ores are lignite, gas coal, anthracite, the metal ore is malachite, and the non-metallic ore is collophanite.

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

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

5. The method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance according to claim 2, characterized in that: The k T2g The relationship between the contact angle θ is: θ=31.1492×k T2g +150.1447 (2); Where θ is the contact angle of the mineral particles, k T2g The slope value of the linear function fitted between the weighted average value of mineral particle T2 and wetting time.

6. The method for rapidly measuring the surface wettability of mineral particles based on low-field nuclear magnetic resonance according to claim 1, characterized in that: In the low-field nuclear magnetic resonance test, the magnetic type is a permanent magnet, the resonance frequency is 12 MHz, the magnetic field strength is 0.3±0.05 T, the diameter of the nuclear magnetic resonance probe coil is 25 mm, the magnet temperature is controlled at 32±0.1°C during the nuclear magnetic resonance test, the pulse sequence is CPMG, the echo time is at least 0.1 ms, the number of sampling times is at least 32, the repeated sampling waiting time is at least 6000 ms, and the number of echoes is at least 18000.

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