Method for microcosmically regulating and controlling coal mine iron-containing tailings and application

Abstract

The invention aims to provide a method for microcosmic regulation and control of coal mine iron-containing tailings and application, and belongs to the technical field of materials and wastewater treatment.The coal mine iron-containing tailings are subjected to microstructure regulation and control through mechanical ball milling, active sites exposed on the surfaces of the iron-containing tailings are increased, and the iron-containing tailings are subjected to microcosmic regulation and control; further, the electron transfer efficiency between the iron-containing tailings and the persulfate is enhanced, and the degradation of the phenol wastewater is promoted. On one hand, the coal mine iron-containing tailings can be subjected to resource utilization, on the other hand, deep removal of the non-degradable coking phenol-containing wastewater can be achieved, the method is a novel economic and efficient coal mine iron-containing tailings resource comprehensive utilization technology, and the method has important significance for providing a theoretical basis and technical support for treatment of coal chemical industry phenol-containing wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of material and wastewater treatment, and particularly relates to a method for micro-regulating iron-containing tailings in coal mines and its application. Background Art

[0002] Phenol wastewater is one of the main phenolic pollutants in coking wastewater, with the characteristics of high yield, difficult degradation and high toxicity. As one of the 129 priority controlled pollutants listed by my country and the United States Environmental Protection Agency, the discharge of phenol wastewater into water resources will not only seriously endanger the survival of aquatic organisms, but also pose a serious threat to human health. my country has clearly stipulated that for the discharge of phenol wastewater, in addition to strictly controlling the COD value, the discharge concentration of phenol wastewater must also be less than 0.5 mg / L. Therefore, how to efficiently and quickly remove phenol from wastewater has become a concern of many researchers.

[0003] Persulfate-based advanced oxidation processes (PS-AOPs) have become an effective means of deep wastewater treatment because of their strong oxidation ability, fast reaction speed and environmental friendliness, and can quickly degrade organic pollutants in water. At present, the heterogeneous catalysts of AOP systems mainly include carbon-based materials, transition metals (such as Fe, Co, Cu, Mn, Ni, Ru) and transition metal oxide materials. Among them, iron-based materials have the advantages of abundant reserves, environmental friendliness and high activity, and are more suitable for use as heterogeneous catalysts activated by persulfate. A variety of iron-based catalysts that have been developed, such as zero-valent iron, iron oxide, ferrous sulfide, etc., are used as Fenton-like catalysts to remove pollutants from wastewater.

[0004] Iron-containing tailings in Shanxi coal mines are a mixed mineral whose main components are iron oxides, SiO2, etc. Due to the versatility of its composition and structure and the effective redox activity of its components, it provides the possibility for the preparation of low-cost, efficient and stable iron-based heterogeneous catalysts.

[0005] In order to improve the catalytic efficiency of iron-containing coal mine tailings, it is very important to make full use of the iron active sites on the surface of iron-containing tailings. Summary of the invention

[0006] The purpose of the present invention is to provide a method and application of micro-control of iron-containing coal mine tailings, so as to realize the high-value utilization of iron-containing coal mine tailings. Through the method of the present invention, the vacancy defects on the surface of iron-containing coal mine tailings can be increased, and the catalytic activity of iron-containing coal mine tailings can be improved. At the same time, the method is applied to the deep treatment of actual wastewater, which is beneficial to the high-value utilization of iron-containing coal mine tailings. It is an effective strategy that follows the concept of sustainable development and circular economy and realizes "waste treatment with waste".

[0007] The present invention adopts the following technical solution: A method for micro-controlling iron-containing tailings in coal mines comprises the following steps: S1. The iron-containing tailings of the coal mine are initially crushed into block particles by a hammer, washed with ultrapure water for 3-4 times to remove dust and impurities on the surface, and then dried in an oven at 80°C for 24 hours; S2, mixing the dried lump coal mine iron-containing tailings with ball milling beads in proportion, and ball milling them in an agate ball mill, and preparing coal mine iron-containing tailings with different degrees of defects by adjusting the speed and time of ball milling; S3, placing the iron-containing tailings after ball milling on a 300-mesh sieve for screening to obtain coal mine iron-containing tailings material with a size of 300 mesh.

[0008] Furthermore, the mass ratio of the coal mine iron-containing tailings to the ball milling beads is 1:10.

[0009] Furthermore, the ball milling speeds are 100 rpm, 200 rpm, 400 rpm, and 600 rpm, respectively; and the ball milling time is 1 h, 2 h, 3 h, and 4 h, respectively.

[0010] A micro-control method for the removal of phenol from iron-containing coal mine tailings is provided.

[0011] A method for micro-controlling the application of iron-containing tailings of coal mines to phenol in water bodies comprises the following steps: S1. Add the regulated iron-containing coal tailings into the prepared phenol solution, and stir evenly in a magnetic stirrer; S2. After stirring evenly, add persulfate to initiate the reaction.

[0012] Furthermore, the volume of the phenol solution is 100-1000 mL, the concentration is 25-100 mg / L, and the pH is 3-11.

[0013] Furthermore, the amount of the regulated coal mine iron-containing tailings added is 0.1-0.5g.

[0014] Furthermore, the concentration of the persulfate is 2-12 mM, and the reaction time is 0-60 min.

[0015] Ball milling can effectively increase the surface area of ​​the material, provide more active sites and promote catalytic performance. In addition, through high-energy milling of solid materials, the accumulation of mechanical energy on the particle surface will cause the material to undergo a unique transformation and change the physical and chemical properties of the material. By optimizing the ball milling conditions, the pyrite particle size can be effectively reduced and the surface chemical properties can be changed.

[0016] The present invention regulates the microstructure of the iron-containing tailings of the coal mine by mechanical ball milling, increases the active sites exposed on the surface of the iron-containing tailings, thereby enhancing the electron transfer efficiency between the iron-containing tailings and persulfate, and promoting the degradation of phenol wastewater. On the one hand, the iron-containing tailings of the coal mine can be utilized as resources, and on the other hand, the deep removal of the difficult-to-degrade coking phenol-containing wastewater can be achieved. It is an economical and efficient new technology for the comprehensive utilization of iron-containing tailings of the coal mine, and it is of great significance to provide a theoretical basis and technical support for the treatment of phenol-containing wastewater in coal chemical industry.

[0017] The beneficial effects of the present invention are as follows: 1. The present invention regulates the iron-containing coal tailings by mechanical ball milling. Compared with natural iron-containing coal tailings, the iron-containing coal tailings regulated by ball milling effectively reduce the particle size and change the surface chemical properties.

[0018] 2. The micro-controlled iron-containing tailings of coal mines prepared by the present invention have a large number of sulfur defects, lattice S (II) and surface Fe (II) active sites, which lays a foundation for improving the efficiency of activating persulfate.

[0019] 3. The experimental results show that the activated persulfate of iron-containing coal mine tailings after micro-control shows efficient removal and mineralization performance for phenol. Under the optimal process conditions, the phenol removal rate can reach up to 100%, and the mineralization rate can reach 64.7%.

[0020] 4. Based on the advantages of simple preparation method, low cost and high efficiency of micro-control of iron-containing tailings from coal mines, the iron-containing tailings of the present invention provide a theoretical basis in the activated persulfate advanced salt advanced oxidation technology, realizing the new concept of "treating waste with waste" for comprehensive resource utilization of iron-containing tailings from coal mines to treat phenol-containing wastewater from coal chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The efficiency of persulfate activated by the iron-containing tailings of coal mine prepared in Example 1 in degrading phenol; Figure 2 The efficiency of persulfate activated by the iron-containing tailings of coal mine prepared in Example 2 in degrading phenol; Figure 3 The efficiency of activating different concentrations of persulfate to degrade phenol by the iron-containing tailings of coal mine prepared in Example 3; Figure 4 The mineralization behavior of phenol degradation by activated persulfate of iron-containing coal mine tailings prepared in Example 4; Figure 5 The EPR spectrum of the iron-containing coal mine tailings prepared in Example 5; Figure 6 The XRD pattern of the iron-containing coal mine tailings prepared in Example 6; Figure 7 This is the XPS graph of the iron-containing coal mine tailings prepared in Example 7. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The iron-containing coal mine tailings described in the following embodiments are all collected from the abandoned tailings piled up in a coal mine in Shanxi.

[0024] The ball milling beads are made of zirconium oxide and other materials with high density, high hardness, excellent chemical stability and biocompatibility.

[0025] Example 1 The collected waste coal mine iron tailings were initially crushed into block particles by hammer, washed with ultrapure water for 3 to 4 times to remove surface dust and impurities, and then dried in an oven at 80°C for 24 h. The dried block coal mine iron tailings were mixed with ball milling beads at a mass ratio of 1:10, loaded into an agate ball mill, and ball milled at 200 rpm for 1 h, 2 h, 3 h and 4 h to obtain coal mine iron tailings treated with different ball milling times. The tailings with different ball milling times were tested for phenol degradation by activated persulfate, and all degradation experiments were carried out in a 250 mL glass beaker. First, 0.3 g of tailings treated with different ball milling times were added to 100 mL of phenol solution with a concentration of 100 mg / L. Secondly, 4 mM persulfate was added to trigger the reaction, and the magnetic stirrer was continuously stirred at a speed of 430 r / min. During the reaction, 2 mL of sample was taken out at specific time intervals and filtered into a liquid brown vial through a 0.22 μm organic disposable filter head. Finally, the brown sample vial was tested by high performance liquid chromatography. The experimental results are shown in Figure 1 The experimental results show that the unmilled iron-containing tailings have a poor activation effect on persulfate (62.3%, 20 min). With the increase of ball milling time, the effect of activating persulfate gradually increases within the same reaction time, reaching 83% when the ball milling time is 4 h, which is 20.7% higher than the degradation effect of the unmilled tailings, indicating that the increase of ball milling time significantly enhances the ability of tailings to remove phenol.

[0026] Example 2 The iron-containing tailings of coal mines after preliminary washing and drying in Example 1 were mixed with ball milling beads at a mass ratio of 1:10, and were placed in an agate ball mill and ball milled at 100 rpm, 200 rpm, 400 rpm and 600 rpm for 2 h to obtain iron-containing tailings of coal mines treated with different ball milling speeds. The tailings treated with different ball milling speeds were tested for the degradation of phenol by activated persulfate. The experimental results are shown in FIG. Figure 2 As shown. The results show that the higher the ball milling speed, the higher the phenol degradation efficiency and the faster the reaction rate. The removal rate of phenol in tailings after ball milling for 2 h at a ball milling speed of 600 rpm can reach 86%. Compared with the degradation effect of tailings without ball milling (62.3%), the removal rate of phenol increased by 23.7%. The high ball milling speed greatly improved the ability of tailings to activate persulfate and promote the removal of phenol. This is attributed to the fact that high ball milling speed can increase the vacancy defects on the surface of iron-containing tailings, which play a key role in promoting electron transfer in the degradation process of phenol.

[0027] Experimental Example 3 Combined with the experimental results of Example 1 and Example 2, for energy consumption and economic considerations, the ball milling time was finally selected to be 2 h and the ball milling speed was 400 rpm. The dried blocky coal mine iron-containing tailings were mixed with ball milling beads at a mass ratio of 1:10, loaded into an agate ball mill jar and ball milled at a speed of 400 rpm for 2 h to obtain the coal mine iron-containing tailings.

[0028] 0.3 g of the prepared iron-containing coal tailings was added to 100 mL of 100 mg / L phenol solution. Secondly, 2 mM, 4 mM, 8 mM and 12 mM persulfate were added to trigger the reaction to explore the removal effect of different concentrations of PMS on phenol. During the reaction, 2 mL of samples were taken out at specific time intervals and filtered through a 0.22 μm organic disposable filter head. Finally, the filtered samples were tested for phenol concentration by high performance liquid chromatography. The experimental results are shown in Figure 2. Figure 3 As shown. The results show that with the increase of PMS concentration (0-4 mM), the removal rate of phenol gradually increases. When the PMS concentration is 4 mM, the system has the best effect of removing phenol (100%). However, excessive PMS will inhibit the removal of phenol. This is because as the concentration of PMS increases, it can consume a significant concentration of SO4 •– , as well as additional PMS, which leads to reduced degradation efficiency.

[0029] Experimental Example 4 The dried lump coal mine iron-containing tailings were mixed with ball mill beads at a mass ratio of 1:10, placed in an agate ball mill and ball milled at a speed of 400 rpm for 2 h to obtain the coal mine iron-containing tailings.

[0030] 0.3 g of the prepared iron-containing coal tailings was added to 100 mL of 100 mg / L phenol solution. Secondly, the reaction was triggered by adding 4 mM persulfate. During the reaction, 2 mL of the sample was taken out at specific time intervals and filtered through a 0.22 μm organic disposable filter head. Finally, the filtered sample was tested by a total organic carbon analyzer. The experimental results are as follows: Figure 4 The results showed that the iron-containing tailings obtained after ball milling at 400 rpm for 2 h could significantly activate persulfate, and the mineralization rate of phenol was as high as 64.7% after 20 min of reaction.

[0031] Experimental Example 5 The dried lump coal mine iron-containing tailings were mixed with ball mill beads at a mass ratio of 1:10, placed in an agate ball mill and ball milled at a speed of 400 rpm for 2 h to obtain the coal mine iron-containing tailings.

[0032] Electron paramagnetic resonance (EPR) tests were performed on iron-containing coal mine tailings before and after ball milling. Figure 5 The EPR spectra of coal mine iron tailings before and after ball milling. The results show that the signal peak of coal mine iron tailings at g=2.003 after ball milling is significantly enhanced, which proves that a large number of sulfur vacancy defects are generated in the iron tailings after ball milling, which is also an important active site.

[0033] Experimental Example 6 The dried lump coal mine iron-containing tailings were mixed with ball mill beads at a mass ratio of 1:10, placed in an agate ball mill and ball milled at a speed of 400 rpm for 2 h to obtain the coal mine iron-containing tailings.

[0034] X-ray diffraction (XRD) analysis was performed on the iron-bearing tailings of the coal mine. Figure 6 The figure shows the main characteristic peaks of iron-containing tailings in coal mines. The results show that the main characteristic peaks of iron-containing tailings in coal mines are FeS2 and FeS. It further shows that iron-containing tailings in coal mines are rich in S and Fe elements, and mechanical ball milling can easily produce lattice defects on the surface of iron-containing tailings, thereby regulating the microstructure.

[0035] Experimental Example 7 The dried lump coal mine iron-containing tailings were mixed with ball mill beads at a mass ratio of 1:10, placed in an agate ball mill and ball milled at a speed of 400 rpm for 2 h to obtain the coal mine iron-containing tailings.

[0036] X-ray photoelectron spectroscopy (XPS) tests were performed on iron-containing coal mine tailings before and after ball milling. Figure 7The XPS spectrum of Fe 2P in iron-containing coal tailings. The results show that ball milling destroys the oxide layer on the surface of coal tailings, which is conducive to the redox reaction. As the reaction proceeds, the surface Fe (II) content of coal tailings before and after the reaction increases from 46.06% to 49.43%, indicating that Fe (II) is well regenerated during the reaction, achieving a good cycle of Fe species valence states, laying a foundation for improving the efficiency of activated persulfate.

[0037] Matters not covered in the present invention are known technologies. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for micro-controlling iron-containing tailings in coal mines, characterized in that: The steps include: S1. The iron-containing tailings of the coal mine are initially crushed into block particles by a hammer, washed with ultrapure water for 3-4 times to remove dust and impurities on the surface, and then dried in an oven at 80°C for 24 hours; S2, mixing the dried lump coal mine iron-containing tailings with ball milling beads in proportion, and ball milling them in an agate ball mill, and preparing coal mine iron-containing tailings with different degrees of defects by adjusting the speed and time of ball milling; S3, placing the iron-containing tailings after ball milling on a 300-mesh sieve for screening to obtain coal mine iron-containing tailings material with a size of 300 mesh.

2. A method for micro-controlling iron-containing tailings in coal mines according to claim 1, characterized in that: The mass ratio of the coal mine iron-containing tailings to the ball mill beads is 1:

10.

3. A method for micro-controlling iron-containing tailings in coal mines according to claim 1, characterized in that: The ball milling speeds are 100 rpm, 200 rpm, 400 rpm, and 600 rpm, respectively; and the ball milling times are 1 h, 2 h, 3 h, and 4 h, respectively.

4. The iron-containing tailings of a coal mine prepared by the method according to claim 1 are used for phenol in water.

5. The application of micro-control of iron-containing tailings in coal mines according to claim 4 is characterized in that: The steps include: S1. Add the regulated iron-containing coal tailings into the prepared phenol solution, and stir evenly in a magnetic stirrer; S2. After stirring evenly, add persulfate to initiate the reaction.

6. The application of micro-control of iron-containing tailings in coal mines according to claim 5, characterized in that: The volume of the phenol solution is 100-1000 mL, the concentration is 25-100 mg / L, and the pH is 3-11.

7. The application of micro-control of iron-containing tailings in coal mines according to claim 5, characterized in that: The amount of the regulated iron-containing coal tailings added is 0.1-0.5g.

8. The application of micro-control of iron-containing tailings in coal mines according to claim 5, characterized in that: The concentration of the persulfate is 2-12 mM, and the reaction time is 0-60 min.

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