Rutile-iron ore slag-biochar composite material, preparation method and application

Abstract

The invention discloses a rutile-iron ore slag-biochar composite material as well as a preparation method and application thereof. The rutile-iron ore slag-biochar composite material is used for efficiently repairing heavy metal pollution through a multi-component synergistic effect. Experiments prove that the combined use effect of the three components is far better than that of single use or combined use of the three components, so that the combined use of the three components has a synergistic effect. The rutile in the material is directly converted into solar energy through photocatalysis, the energy consumption in the degradation process is reduced, the material is low in cost and environmentally friendly, the iron-ore slag and the biochar are both from industrial / agricultural wastes, the purpose of treating wastes with wastes is achieved, and a new path is provided for green, efficient, economical, environmentally friendly, free of secondary pollution and capable of continuously treating heavy metal pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to an environmental remediation material, and more particularly to a rutile-iron slag-biochar composite material, a preparation method and an application thereof. Background Art

[0002] In recent years, with the rapid development of China's social economy and industrialization, the problem of heavy metal pollution has become increasingly prominent, mainly existing in water bodies and soil environments. Investigations show that 70% of heavy metal pollution comes from mining and smelting activities. After these harmful elements enter the soil, once they exceed the standard, they will cause serious environmental pollution, resulting in economic losses and endangering the ecosystem and human health.

[0003] Nanomaterial adsorbents have received extensive attention in the field of heavy metal pollution control due to their unique potential adsorption characteristics such as high specific surface area, excellent reactivity and abundant adsorption sites. Related research at home and abroad has shown that nanorutile (TiO 2 ) has good adsorption effect and photocatalytic activity, showing environmental properties of adsorbing and degrading heavy metal pollutants such as arsenic and chromium. However, high-purity nanometer TiO 2 is expensive, and unmodified high-purity nanometer TiO 2 is prone to agglomeration in the soil and cannot play its role in pollution control well. Therefore, finding a suitable TiO 2 modification method to improve the adsorption efficiency of the material for heavy metal ions and reduce the treatment cost is the key to developing the application technology of mineral composite materials as adsorbents.

[0004] To give full play to the function of nanometer TiO 2 , some researchers have loaded it on carriers with special structures, large specific surface areas, good stability and strong adsorption capacities (such as biochar). Biochar has high aromaticity and porous structure, rich surface oxygen-containing functional groups and high ion exchange capacity, and is widely used in the fields of environmental remediation and soil improvement. However, raw biochar has limitations such as limited adsorption capacity, only adsorption without degradation, easy to cause secondary pollution and weak adsorption capacity for some high-valent heavy metals (such as hexavalent chromium). The combination of rutile and biochar not only successfully solves the agglomeration phenomenon of nanoparticles, but also improves the removal rate of heavy metals by pure rutile and raw biochar. However, the composite material is still expensive, and although the removal efficiency of heavy metals has been significantly improved, there is still room for improvement.

[0005] Iron ore slag is the main solid waste generated in the process of iron ore beneficiation, with an annual global emissions exceeding 100 million tons. At present, the main treatment method for iron ore slag is open stacking, which poses a great environmental risk. Previously, some scholars have tried to use iron ore slag to degrade heavy metal ion pollution in water and soil, and found that iron ore slag can remove heavy metal ions in water. However, due to agglomeration, its adsorption efficiency is not high and it cannot be put into large-scale use. Therefore, we tried to 2 compound three materials: nano-TiO

[0006] , iron ore slag and biochar, to solve the agglomeration problem during the use of single minerals and slag, improve the removal efficiency of heavy metals, and at the same time reduce the dosage and cost of the composite material, so as to achieve waste treatment with waste. Summary of the Invention

[0007] One of the purposes of the present invention is to provide a rutile-iron ore slag-biochar composite material and its preparation method.

[0008] Another purpose of the present invention is to provide the application of the above rutile-iron ore slag-biochar composite material.

[0009] To achieve the above purposes, the technical solution of the present invention is as follows:

[0010] A rutile-iron ore slag-biochar composite material, and its preparation method includes the following steps:

[0011] (1) Mix the raw materials of rutile, iron ore slag and biochar, place them in distilled water, fully mix them in an ultrasonic cleaner, and then dry them to constant weight in an 80°C drying oven;

[0012] (2) Weigh the dried mixed raw materials, place them in a covered ceramic crucible, press out the air, cover the crucible and wrap it tightly with tin foil;

[0013] (3) Put the ceramic crucible into a tube furnace, heat it from room temperature to 400°C and keep it for 120 minutes. After the pyrolysis time is reached, turn off the power of the tube furnace, and take out the crucible after the temperature in the furnace slowly drops to room temperature;

[0014] (4) Peel off the tin foil, grind it to 200 meshes, and prepare the rutile-iron ore slag-biochar composite material.

[0015] Preferably, the mass ratio of the rutile, iron slag and biochar raw material is 1:1:4.

[0016] Preferably, the rutile is nano rutile, and the biochar raw material is soybean straw, corn cob and bagasse, more preferably soybean straw. The rutile-iron slag-corn cob biochar composite material, rutile-iron slag-bagasse biochar composite material and rutile-iron slag-soybean straw biochar composite material are respectively prepared.

[0017] Preferably, the heating rate in step (3) is 10 °C / min.

[0018] Most importantly, the present invention proves through experiments that the above rutile-iron slag-biochar composite material can effectively degrade inorganic heavy metal ions and organic pollutants. The inorganic heavy metal ions include chromium, arsenic, etc.; the organic pollutants include methylene blue, etc.

[0019] And by using an LED lamp to simulate the solar light source, the degradation effects of the rutile-iron slag-biochar composite material on heavy metals in polluted wastewater or soil under light and dark conditions are observed. The results show that the degradation effect is better under light conditions. The light source in the present invention is natural light or simulated sunlight.

[0020] In the present invention, rutile, as a typical semiconductor mineral, can form photo holes with oxidation properties and photo-generated electrons with reduction properties under light conditions, promoting the adsorption and degradation of heavy metal ions. However, pure high-purity nano TiO 2 is prone to agglomeration in the soil and cannot play its role well.

[0021] Due to the hydration effect, free hydroxyl groups, carboxyl groups and other functional groups will be generated on the surface of iron slag to form complexes with various heavy metal cations. Iron slag has a large specific surface area and a multi-layer irregular mesoporous structure, which can promote the adsorption and degradation of heavy metals. At the same time, Fe in the iron slag 2+ can reduce high-valent heavy metal ions to low-toxic states, thereby realizing the degradation of heavy metals. However, the mineral components in iron slag, such as goethite, have problems of agglomeration and low adsorption efficiency in the actual application process, and other materials are needed to provide support to overcome the defect that the material itself is prone to agglomeration and improve the adsorption performance of iron slag.

[0022] Advantages of the present invention:

[0023] The present invention realizes the efficient remediation of heavy metal pollution through the multi-component synergistic effect of rutile-iron slag-biochar composite materials. In the materials, rutile photocatalytically directly converts and utilizes solar energy, reducing the energy consumption during the degradation process. Moreover, the materials are low-cost and environmentally friendly. Both iron slag and biochar are derived from industrial / agricultural waste, achieving "treating waste with waste", providing a new path for green, efficient, economically environmentally friendly, non-secondary pollution, and sustainable treatment of heavy metal pollution.

[0024] Biochar is a low-cost, environmentally friendly, and widely sourced environmental remediation material. Its large specific surface area, developed pore structure, and the presence of abundant active functional groups such as carbonyl, carboxyl, and hydroxyl groups on the surface endow biochar with good adsorption characteristics and strong ion complexation ability, enabling it to interact with heavy metal ions, organic pollutants, etc. in water, soil, or sediment, reducing their environmental risks. As a common mineral attachment material, biochar can be used as a good carrier for rutile and iron slag to prepare composite adsorption materials with the advantages of all three.

[0025] The present invention proves through experiments that the effect of using the three in combination is far greater than that of using them alone or in combination of two. It can be seen that the combination of the three plays a synergistic and enhancing role. Brief Description of the Drawings

[0026] Figure 1 It is a comparison chart of the degradation efficiency of laboratory-simulated chromium-containing wastewater by three ternary composite materials of the present invention.

[0027] Figure 2 It is a comparison chart of the degradation efficiency of laboratory-simulated chromium-containing wastewater by different adsorption materials of the present invention.

[0028] Figure 3 It is a comparison chart of the degradation efficiency of laboratory-simulated methylene blue-polluted wastewater of the present invention. Detailed Embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments, and the advantages and characteristics of the present invention will become clearer as the description progresses. However, the specific experimental methods involved in the following embodiments are all conventional methods or are implemented according to the conditions recommended in the manufacturer's instructions unless otherwise specified.

[0030] Unless otherwise specified, the technical means used in the embodiments are conventional means well-known to those skilled in the art. The test methods in the following embodiments are all conventional methods unless otherwise specified. Unless otherwise specified, the reagents and materials used can all be obtained by purchasing from the market.

[0031] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to persons skilled in the art. In addition, any methods and materials similar or equivalent to those described may be applied to the present invention. The preferred methods and materials described herein are for illustrative purposes only.

[0032] Preparation method of rutile-iron slag-biochar composite

[0033] The nanorutile, iron slag, and biochar raw materials (corn cob, sugarcane bagasse, or soybean straw) were respectively mixed in a mass ratio of 1:1:4 and placed in distilled water. After being thoroughly mixed in an ultrasonic cleaner, they were dried to a constant weight at 80 °C in a drying oven. 10 g of the dried mixed raw materials were weighed with a balance and placed in a 40 mL covered ceramic crucible. The air was squeezed out, the lid was covered, and it was tightly wrapped with tin foil. The ceramic crucible was placed in a tube furnace and heated from room temperature (about 25 °C) to 400 °C at a heating rate of 10 °C / min and held for 120 min. After the pyrolysis time reached, the power of the tube furnace was turned off. After the temperature in the furnace slowly dropped to room temperature, the crucible was taken out, the tin foil was peeled off, weighed one by one, ground to 200 mesh, and then sealed and stored in a sample bag. Rutile-iron slag-corn cob biochar, rutile-iron slag-sugarcane bagasse biochar, and rutile-iron slag-soybean straw biochar composites were respectively prepared.

[0034] In order to obtain better conclusions, the following experiments were carried out in the present invention.

[0035] Experimental example 1 Comparison of the degradation efficiency of three composites on chromium-containing wastewater

[0036] 100 mL of chromium solutions with a concentration of 30 mg / L were respectively prepared in 3 100 mL conical flasks using a chromium standard stock solution (10 g / L). Dilute H 2 SO 4 and NaOH were used to adjust the initial pH to be approximately equal to 2.5. 0.2 g of rutile-iron slag-corn cob biochar composite, rutile-iron slag-sugarcane bagasse biochar composite, and rutile-iron slag-soybean straw biochar composite were accurately weighed with an electronic balance and added to the prepared solutions. The adsorption test was carried out under the irradiation of an LED light source, and the chromium concentration in the solution was sampled and tested at a given time.

[0037] The experimental results of the removal of simulated chromium wastewater by the three ternary composites are as Figure 1As shown in the figure. It can be seen from the figure that under light illumination conditions, the removal rate of chromium by the rutile-iron slag-soybean straw biochar composite material is significantly higher than that of the other two composite materials, and the removal rate reaches 75.53% in 6 h. The removal effect of the rutile-iron slag-corn cob biochar composite material (55.47%) is slightly better than that of the rutile-iron slag-sugarcane bagasse biochar composite material (53.04%). Therefore, the rutile-iron slag-soybean straw biochar composite material was selected for subsequent simulation experiments.

[0038] Experimental Example 2 Comparison of the Degradation Efficiency of Different Adsorbents for Chromium-Containing Wastewater

[0039] Use a chromium standard stock solution (10 g / L) to prepare 100 mL of chromium solution with a concentration of 30 mg / L in 5 100 mL conical flasks respectively. Use dilute H 2 SO 4 and NaOH to adjust the initial pH to approximately 2.5. Weigh accurately two groups of 0.2 g of rutile-iron slag-soybean straw biochar composite material (1:1:4) with an electronic balance and add them to the prepared solution. One group conducts the adsorption experiment under the irradiation of an LED light source, and the other group conducts the adsorption experiment in the dark. Samples are taken at given times to measure the chromium concentration in the solution. In addition, weigh accurately 0.2 g of rutile-soybean straw biochar (1:2), iron slag-soybean straw biochar composite material (1:2), 0.2 g of rutile after pyrolysis alone, 0.2 g of iron slag, and 0.2 g of soybean straw biochar with an electronic balance and add them to the remaining prepared chromium solution. Conduct the adsorption experiment under the irradiation of an LED light source, and take samples at given times to measure the chromium concentration in the solution.

[0040] The experimental results of the removal of simulated chromium wastewater by different composite materials are as Figure 2 shown. Compared with the dark condition, the rutile-iron slag-soybean straw biochar composite material has a better adsorption effect under light illumination. Its removal rate reaches 75.53% in 6 h under light illumination, which is about 12% higher than the removal rate under dark conditions. This is because the valence band electrons of rutile (TiO 2 ) are excited to jump to the conduction band under light illumination, generating highly active electrons (e - ) and holes (h + ). The conduction band electrons can directly reduce Cr(Ⅵ) to Cr(III), while h+ oxidizes water or surface hydroxyl groups to generate ·OH radicals, indirectly promoting the reduction of Cr(VI). In addition, the photo-generated electrons of rutile promote the reduction of Fe 3+ in iron slag to Fe 2+ , maintaining the Fe 2+ / Fe 3+ cycle. The continuous supply of Fe 2+ significantly increases the chemical reduction rate of Cr(Ⅵ):

[0041] 3Fe 2+ +HCrO 4 - +7H + →3Fe 3+ +Cr 3+ +4H 2 O

[0042] At the same time, at 6 h, the removal rate of Cr(VI) by the ternary composite material is about 15% higher than that of the rutile-soybean straw biochar composite material, about 36% higher than that of the iron slag-soybean straw biochar composite material, and about 49% higher than that of the original biochar. The removal rates of chromium by uncomposited rutile and iron slag at 6 h are both lower than 20%, and the chromium removal rate of iron slag (19.08%) is slightly higher than that of rutile (12.50%).

[0043] Experimental Example 3 Comparison of the degradation efficiency of different adsorbents for methylene blue wastewater

[0044] The degradation experiment of methylene blue wastewater (Methylene Blue, MB) was simulated in the laboratory. 0.2 g of rutile-iron slag-soybean straw biochar, rutile-soybean straw biochar, iron slag-soybean straw biochar composite materials, and separately pyrolyzed rutile, iron slag, and the original biochar were added to 100 mL of an MB solution with a concentration of 40 mg / L (pH = 2.5) respectively, and the removal effects of different adsorbents on MB were observed. In addition, an LED lamp was used to simulate the sun light source, and the differences in the adsorption effects of the rutile-iron slag-biochar composite material on MB under light and dark conditions were observed. The removal effects of different adsorbents on MB are as Figure 3 shown.

[0045] As can be seen from the figure, compared with the dark condition, the removal rate of MB by the rutile-iron slag-soybean straw biochar composite under light is significantly accelerated, and its removal rate reaches 99.99% at 6 h, indicating that the composite has good photocatalytic activity. Under light, rutile is excited as a photocatalyst to generate electron-hole pairs, which in turn generate reactive oxygen species that can efficiently degrade MB. The removal rate of MB by the rutile-soybean straw biochar composite under light for 6 h is 82.79%, which is lower than that of the ternary composite. The iron slag-soybean straw biochar composite mainly relies on the chemical reduction of iron oxides and the physical adsorption of biochar, lacking photocatalytic degradation ability. Its removal rate at 6 h is 68.02%, significantly lower than the adsorption performance of the ternary composite, but slightly higher than that of pure biochar (60.65%). This is because the loading of iron slag increases the specific surface area of biochar, changes and enhances the surface functional groups of biochar, and provides more active adsorption sites, which is helpful for the adsorption of MB. The separately pyrolyzed rutile and iron slag particles are prone to agglomeration, and their degradation performance is poor, and the removal rate of MB is much lower than that of the original biochar.

[0046] Experimental Example 4 Degradation effect of the composite material of the present invention in arsenic-contaminated soil

[0047] The prepared rutile-iron slag-soybean straw biochar composite was applied to the arsenic-contaminated soil of the simulated site, and a potted Epipremnum aureum experiment was carried out by adding 5% of the composite. The Epipremnum aureum in the experimental group and the control group were both added with arsenic-contaminated soil, and normal soil was added to the blank group. The cultivation conditions of the three groups of Epipremnum aureum were the same. The difference was that 5% of the composite was additionally added to the potted Epipremnum aureum in the experimental group. After continuous remediation for 7 days, the fresh weight and dry weight of the three groups of Epipremnum aureum are shown in Table 1.

[0048] Table 1 Relevant parameters of the potted experiment of the laboratory-simulated arsenic-contaminated soil

[0049]

[0050]

[0051] As can be seen from Table 1, except for the blank group, the growth of Epipremnum aureum in the other two groups was affected by arsenic pollutants to a certain extent, but the growth of Epipremnum aureum in the experimental group was much better than that in the control group, indicating that the composite material of the present invention can weaken the toxicity of arsenic pollution to plants to a certain extent.

[0052] In summary, the rutile-iron slag-biochar composite remediation material described in the present invention significantly enhances the degradation effect on inorganic heavy metal ions such as chromium and arsenic, and organic pollutants such as methylene blue. The utilization of iron slag (industrial waste residue) and biochar (pyrolysis product of agricultural / forestry waste) conforms to the concept of "treating waste with waste" and reduces the material cost. Moreover, the composite material realizes the successful conversion of solar energy, with lower energy consumption and more thorough degradation. Through the synergy of multiple mechanisms, this composite material achieves efficient, green, and low-cost ecological restoration, and has significant application potential in the fields of soil remediation, water purification, and ecological restoration.

[0053] The above-described embodiments are only preferred embodiments of the present invention, which are merely used to explain the present invention and do not limit the scope of implementation of the present invention. For those skilled in the art of this technology, other implementation manners can of course be easily made through replacement or change according to the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A method for preparing a rutile-iron slag-biochar composite material, characterized in that: The preparation method comprises the following steps: (1) Mix rutile, iron slag and biochar raw materials and place them in distilled water, mix them thoroughly in an ultrasonic cleaner, and then dry them in a drying oven at 80°C to constant weight; (2) Weigh the dried mixed raw materials, place them in a ceramic crucible with a lid, press to squeeze out the air, cover with a lid, and wrap tightly with tin foil; (3) placing the ceramic crucible in a tubular furnace, heating from room temperature to 400°C and maintaining for 120 min. After the pyrolysis time is reached, turning off the power of the tubular furnace, and taking out the crucible after the temperature in the furnace slowly drops to room temperature; (4) Peel off the tin foil and grind to 200 mesh to prepare rutile-iron slag-biochar composite material.

2. The method for preparing the rutile-iron slag-biochar composite material according to claim 1, characterized in that: The mass ratio of the rutile, iron slag and biochar raw materials is 1:1:

4.

3. The method for preparing the rutile-iron slag-biochar composite material according to claim 1, characterized in that: The rutile is nano rutile, and the raw materials of biochar are soybean straw, corn cob and sugarcane bagasse.

4. The method for preparing the rutile-iron slag-biochar composite material according to claim 3, characterized in that: The biochar raw material is soybean straw.

5. The method for preparing the rutile-iron slag-biochar composite material according to claim 1, characterized in that: The heating rate in step (3) is 10°C / min.

6. The rutile-iron slag-biochar composite material prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the rutile-iron slag-biochar composite material according to claim 6 in degrading inorganic heavy metal ions and organic pollutants.

8. The use according to claim 7, characterized in that: The inorganic heavy metal ions include chromium and arsenic; the organic pollutants include methylene blue.

9. The use according to claim 7, characterized in that: The application is carried out under light conditions.

10. The use according to claim 7, characterized in that: The illumination comes from natural light or simulated sunlight.

Images