Preparation method of modified nickel tailings and application thereof in efficient degradation of RB-19

Abstract

The present invention provides a preparation method of modified nickel tailings. The nickel tailings are subjected to drying, sieving and ball milling to obtain pretreated nickel tailings; the pretreated nickel tailings are mixed with NaOH solution and EDTA-2Na, and after hydrothermal reaction, solid-liquid separation and washing are carried out to obtain a first product; a phosphoric acid solution is dripped on the surface of the first product, and after calcination treatment, the product is ground to obtain modified nickel tailings. The present invention also provides the application of the above-mentioned modified nickel tailings. In the wastewater containing RB-19, the above-mentioned modified nickel tailings and persulfate are added, and after adjusting the pH value of the system, standing for a certain time can degrade RB-19. The present invention realizes the resource utilization of nickel tailings, transforms the chemical form of heavy metals in the tailings, the obtained catalyst has excellent catalytic performance, the removal rate of RB-19 reaches more than 96%, and magnetic recovery treatment can be adopted. This method is simple and feasible, has no secondary pollution, is fast and convenient, and has low cost, and has wide industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of solid waste and harmless treatment of wastewater, and specifically relates to a preparation method of modified nickel tailings, and also relates to an application of the modified nickel tailings in the efficient catalytic degradation of RB-19 by persulfate. Background Art

[0002] Nickel-based materials are a common type of highly efficient catalyst in the environmental catalytic system, but nickel-based materials may cause serious heavy metal pollution during mining and processing. Taking the mining of nickel minerals as an example, there are currently more than a hundred nickel tailing ponds in China due to this, and the amount of nickel tailings stored in the open air is as high as 30 million tons. The cost of extracting heavy metals from these tailings is relatively high, but during the long-term stacking process, they will migrate into the surrounding surface water, groundwater and soil, causing serious pollution and damage to the local environment. In the current environment, resource utilization of tailings to turn waste into treasure is the most effective method to control heavy metal pollution and increase the value of tailings.

[0003] Organic wastewater containing azo dyes is highly toxic to the environment and humans because the decomposition process of azo dyes will produce various carcinogenic aromatic amines. Traditional treatment methods for organic wastewater include chemical coagulation / flocculation, adsorption, membrane filtration, etc., but these treatment methods can only transfer azo dye pollutants rather than degrade them, and cannot achieve the purpose of harmlessness. Therefore, advanced oxidation processes (AOPs) are considered an alternative method for organic wastewater treatment because AOPs can achieve the purpose of degrading azo dyes. Currently, there are many types of AOPs processes, and the use of catalysts is an indispensable part of them, and they are generally materials products made of transition metals.

[0004] Transition metal catalyst materials are generally pure-phase metal elements or metal oxides. By being compounded with carriers, they become products with high catalytic ability and are widely used in fields such as wastewater pollution and automotive exhaust pollution control. However, these pure-phase catalyst materials have serious disadvantages such as complex preparation processes, high preparation costs, short product lifetimes, etc., and the output is limited. And currently, the demand for catalysts in various fields is huge, resulting in the continuous increase in the price of catalysts, which restricts the development prospects of this system. In the technology of tailings resource utilization, converting the residual transition metals in tailings into catalysts is one of the important emerging ways.

[0005] Research shows that the by-products of the transition metal processing process can also be used to activate peroxymonosulfate (PMS) after activation to achieve a Fenton-like reaction, and then become catalyst materials in the field of organic wastewater treatment. The raw material cost of this product is low, the production process is simple, the operation is easy, and it has the advantages of high catalytic efficiency, easy availability, and easy separation and recovery.

[0006] Based on this, a preparation method of modified nickel tailings applicable to the treatment of organic wastewater containing azo dyes is provided to achieve the efficient degradation of azo dye pollutants, which is of great significance for the resource utilization of tailings and environmental protection and is also a technical problem that researchers urgently need to solve. Summary of the Invention

[0007] One of the objectives of the present invention is to provide a preparation method of modified nickel tailings with a simple preparation process, excellent catalytic performance, and easy recovery.

[0008] Another objective of the present invention is to provide a method for removing RB-19 from wastewater with low cost, convenient operation, high treatment efficiency, and the effluent quality meeting the relevant standard requirements.

[0009] The technical solution adopted by the present invention to achieve the first objective is as follows: A preparation method of modified nickel tailings is provided, including the following steps:

[0010] S1. The nickel tailings are subjected to drying, sieving, and ball milling to obtain pretreated nickel tailings;

[0011] S2. The pretreated nickel tailings are mixed with NaOH solution and EDTA-2Na, and hydrothermally reacted for a certain period of time, followed by suction filtration and washing to obtain a first product;

[0012] S3. Phosphoric acid solution is dripped onto the surface of the first product, and then it is calcined at 450-650 °C for 3-5 h. The calcined product is ground to obtain modified nickel tailings.

[0013] In the above preparation method, first, nickel tailings are used as raw materials. Compared with other tailings (such as phosphorus slag, manganese slag, etc.), nickel tailings contain relatively high contents of Fe2O3 and NiO. The catalytic performance of Ni is superior to that of Mn and P, and at the same time, Ni also has the characteristic of being magnetically recyclable. Secondly, the present invention adopts a combination of ball milling, water bath and calcination to achieve the modification of nickel tailings. Among them, ball milling treatment obtains finely ground tailings particles and promotes dispersion, so that they can fully contact with NaOH in the subsequent alkali modification process; in the alkali modification step, NaOH solution and EDTA-2Na (disodium ethylenediaminetetraacetate) are mixed with nickel tailings, and the alkali modification effect is better; EDTA-2Na is a relatively common complexing agent or surfactant, which can form M-EDTA with transition metals M (Fe, Ni, Co, etc.), helping to separate transition metals from relatively stable mineral phases to form an active state, and then generating a chemically active state with higher activity in an alkaline environment to become a catalytically active component. Finally, considering that the nickel tailings raw materials have not been subjected to high-temperature treatment, after undergoing pretreatment and alkali modification, the sample structure will be unstable, affecting its catalytic effect. The present invention adopts a preparation scheme of loading phosphate groups on the material surface and then calcining it under appropriate temperature conditions. This operation can not only further remove impurities and stabilize the sample structure, but also the phosphate groups loaded on the product surface help to further improve the activity of the catalyst.

[0014] Furthermore, in step S3, controlling the calcination temperature at 450 - 650 °C and the calcination time at 3 - 5 h can enable the iron- and nickel-containing mineral phases to remove crystal water or interlayer water, form a small amount of magnetic oxides and form abundant pores in the layered structure of the material, increasing the specific surface area of the material and being beneficial to the electron transfer during the process of degrading organic pollutants. If the temperature is lower than this range, incomplete removal of interlayer water will occur, the porosity of the material will decrease, resulting in insufficient contact between the material and pollutants, and thus reducing the degradation efficiency; if the temperature is higher than this range, partial collapse of the silicon-aluminum-based structure of the material will occur, and a small amount of active components such as iron and nickel will be reorganized and inactivated again, also resulting in a reduction in efficiency.

[0015] The preparation method provided by the present invention can complete the transformation of the morphology of nickel tailings under relatively mild conditions. On the one hand, it can improve the utilization value of the residual heavy metals in the tailings, and on the other hand, it can also solve the problem of harmless treatment of bulk tailings, achieving the purpose of turning waste into treasure.

[0016] Further, in step S1, the drying conditions include: storing the nickel tailings in an oven at 60-90°C for more than 48 hours. This operation can prevent particle agglomeration from affecting the modification effect. The mesh number for sieving is preferably 100-150 meshes. In addition, during the ball milling process, the ball milling time should not be too long to avoid particle agglomeration from affecting the dispersion effect. Preferably, the ball milling rate is 300-500 rpm, and the ball milling time is 5-20 minutes.

[0017] In the present invention, after sieving and ball milling, the tailings can be made into uniformly sized and suitable granular form, enabling the nickel tailings to come into more sufficient contact with the modifier during the subsequent activation process, so that more transition metals become the catalyst active components.

[0018] Further, in step S2, if the proportion of nickel tailings is too high, there will be too many unmodified impurities in the product, covering the active transition metal components and resulting in a decrease in the catalytic efficiency of the product. While if the proportion of the alkali modifier is too high, the transition metals will precipitate from the mineral phase to hydroxide, also leading to a decrease in the catalytic efficiency.

[0019] Preferably, in step S2, the mass-to-volume ratio of the pretreated nickel tailings to the NaOH solution is 1:(3-5) g / mL; the concentration of the NaOH solution is 2-4 mol / L. It has been found through research that when the concentration of the NaOH solution exceeds 4 mol / L, the catalytic performance of the product will decline. Controlling the mass-to-volume ratio of the pretreated nickel tailings to the NaOH solution at 1:(3-5) g / mL can achieve a higher catalytic effect.

[0020] Further, in step S2, the dosage of EDTA-2Na is mainly determined by the catalytic active (iron, nickel) components contained in the nickel tailings. Since the above components only account for a small part of the tailings, when the dosage of EDTA-2Na is too much, some EDTA-2Na fails to play a role and remains on the material surface after filtration, which may pollute the water body during the use of the catalyst, causing secondary pollution. Therefore, preferably, the mass ratio of the pretreated nickel tailings to EDTA-2Na is 100:(0.5-2).

[0021] Further, in step S2, the temperature of the hydrothermal reaction is 100-120°C, and the time of the hydrothermal reaction is 2-3 hours.

[0022] Further, the solid-liquid separation in step S2 can be carried out by suction filtration: let the product after the hydrothermal reaction stand, remove most of the supernatant and the upper light brown suspension, transfer the remaining dark brown substance to the suction filtration funnel, perform suction filtration and wash it with deionized water multiple times to obtain the first product.

[0023] Preferably, in order to increase the content of the active components of the modified nickel tailings and reduce the usage amount of the modified nickel tailings during application, the present invention can also perform a magnetic separation operation in step S2 and step S3. Specifically, in step S2, the solid-liquid separation is carried out by magnetic separation: a flaky magnet is arranged around the inner wall of the hydrothermal reaction vessel, and the first magnetic separation is carried out during the hydrothermal reaction process, and the product obtained by magnetic separation is used as the first product for subsequent operations; then in step S3, after the calcined product is ground, it is subjected to a second magnetic separation with a magnetic field intensity of 0.1-1T, and finally the modified nickel tailings are obtained. In the above operations, by experiencing a pre-magnetic separation during the preparation process and a second magnetic separation during the modification process, more impurities are removed, and the obtained catalytic structure is mainly composed of iron and nickel, which can exert a better catalytic effect with a smaller dosage.

[0024] Further, in the step S3, the mass-volume ratio of the first product to the phosphoric acid solution is 100:(2-10) g / mL; the concentration of the phosphoric acid solution is 0.5-2 mol / L. In the present invention, controlling the dropping amount of the phosphoric acid solution can load the phosphate groups on the material surface, which helps to further improve the activity of the catalyst. If the dropping amount of the phosphoric acid solution is too large or the concentration is too high, some aluminum salts and calcium salts will form insoluble phosphates with the phosphate groups, and their structures are unstable under acidic conditions, resulting in the loss of phosphate groups; if the dropping amount of the phosphoric acid solution is too small or the concentration is too low, the content of phosphate groups is low, which is difficult to be loaded on the material surface, increasing the cost while unable to improve the catalytic efficiency. Preferably, the mass-volume ratio of the first product to the phosphoric acid solution is 100:(4-6) g / mL, and the concentration of the phosphoric acid solution is 1 mol / L.

[0025] The modified nickel tailings prepared by the present invention have an overall composite layered nano-folded structure (500-1000 nm), which greatly increases its specific surface area. At the same time, iron and nickel elements are distributed on its surface, and it has the function of catalyzing persulfate.

[0026] The technical solution adopted by the present invention to achieve the second object is: to provide an application of the modified nickel tailings prepared by the preparation method according to the first object of the present invention in the efficient catalytic degradation of RB-19 by persulfate.

[0027] RB-19 (reactive blue), as a common dye, compared with other organic dyes, RB-19 has the characteristics of being easy to decolorize but difficult to mineralize. This makes the organic wastewater containing RB-19 have a greater treatment difficulty compared with other wastewaters. The modified nickel tailings prepared by the present invention have undergone alkali modification and calcination operations. The calcium iron oxides and nickel mineral phases contained in the product can activate PMS as a catalyst and degrade pollutants through electron transfer, not only achieving the decolorization of RB-19, but also effectively mineralizing and degrading it.

[0028] In the present invention, compared with other oxidants (such as hydrogen peroxide, etc.), persulfate cooperates with the modified nickel tailings, and can achieve better degradation effect on the premise of lower dosage. Preferably, the persulfate is selected from the group consisting of potassium persulfate, sodium persulfate, ammonium persulfate, or a combination of one or more thereof.

[0029] Furthermore, the application includes: adding the modified nickel tailings and persulfate into the wastewater containing RB-19, the mass ratio of the modified nickel tailings to the persulfate is (5-30):1, adjusting the pH of the system to 1-5, standing for a certain time, and obtaining the treated wastewater. Preferably, the pH of the system is adjusted to 1.5-2.5.

[0030] Furthermore, according to the content of RB-19 in the wastewater, the dosage of the modified nickel tailings and persulfate is determined. Preferably, in the wastewater containing RB-19, the concentration of RB-19 is 20-400 mg / L, and the mass ratio of the modified nickel tailings to RB-19 is 1:(1-20).

[0031] Preferably, in the above application, 0.1 mol / L NaOH and 0.1 mol / L H2SO4 are used to adjust the pH of the system.

[0032] Furthermore, the application also includes: recovering the modified nickel tailings after treating the wastewater by means of suction filtration or magnetic attraction, fully drying the recovered modified nickel tailings, and reusing them for the treatment of the wastewater containing RB-19. In the present invention, the recovered modified nickel tailings can be directly reused, and still have a high treatment efficiency. Through research, it is found that even if the calcium-iron mineral phase changes, it still has the ability of electron transfer, and the dissolution amount of iron ions is extremely small.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The modified nickel tailings prepared by the preparation method provided by the present invention are used in combination with persulfate PMS to treat the wastewater with an RB-19 concentration of 20-400 mg / L. The degradation rate of RB-19 reaches more than 96%, and the degradation process can be completed within 30 minutes, which has high efficiency; the dosage of the catalyst (modified nickel tailings) and persulfate is low, and the modified nickel tailings can be magnetically recovered without secondary pollution and low cost.

[0035] (2) The chromaticity of the final effluent quality of the wastewater treated by the modified nickel tailings provided by the present invention is 2-16, which is far lower than the standard of not exceeding 70 specified in the National Discharge Standard of Water Pollutants for the Textile Dyeing and Finishing Industry (GB / T 4287-2012), and meets the first-class standard of the maximum allowable discharge concentration of the basic control items in the Environmental Quality Standard for Surface Water (GB3838-2002) of not exceeding 30.

[0036] (3) The preparation method of the modified nickel tailings provided by the present invention has a simple process and wide application, can achieve large-scale industrial application, and has good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a process flow chart of the application of the modified nickel tailings provided in Example 1 of the present invention in degrading RB-19 in wastewater;

[0038] Figure 2 It is an XRD pattern of the modified nickel tailings prepared in Example 1; among them, NCT-0 is nickel tailings, NCT-β is the modified nickel tailings material prepared in Example 1; A-NCT-β is the modified nickel tailings residue separated after the degradation test in Application Example 1;

[0039] Figure 3 It is an SEM-EDS pattern of the modified nickel tailings (NCT-β) prepared in Example 1;

[0040] Figure 4 It is an XPS (X-Ray Photoelectron Spectroscopy) elemental analysis result chart of the modified nickel tailings (NCT-β) prepared in Example 1;

[0041] Figure 5 It is an ESR analysis pattern of the modified nickel tailings (NCT-β) prepared in Example 1;

[0042] Figure 6 It is the degradation effect of the repeated use of the modified nickel tailings (NCT-β) prepared in Example 1 on RB-19. DETAILED DESCRIPTION OF THE INVENTION

[0043] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0044] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0045] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the present invention.

[0046] The nickel tailings (NCT-0) used in the following examples were all waste materials to be disposed of stored in a tailings pond near a nickel mine mining site in Kunming, Yunnan. The main components (XRF analysis) of the nickel tailings (NCT-0) are shown in Table 1.

[0047] Table 1

[0048]

[0049] The main parameters of the examples and comparative examples of the present invention are shown in Table 2 below:

[0050] Table 2

[0051]

[0052]

[0053] Example 1

[0054] Step 1: Place the nickel tailings (NCT-0) in an oven at 80 °C and dry for 48 h, then grind through a 100-mesh sieve; then perform ball milling (rotation speed of 400 rpm) for 10 min to obtain pretreated nickel tailings (NCT-0);

[0055] Step 2: Weigh 100 g of the pretreated nickel tailings NCT-0 and mix it with 300 mL of 3 M NaOH solution and 1 g of EDTA-2Na; place the above reactants in a polytetrafluoroethylene conical flask and react in a water bath at 105 °C for 2 h; then let it stand to remove most of the supernatant and the upper light brown suspended substances, transfer the remaining dark brown substances to a suction filtration funnel, perform suction filtration and wash with deionized water 5 times to obtain solid NCT-α;

[0056] Step 3: Place the solid NCT-α obtained in Step 2 in a cylindrical crucible, evenly drop 5 mL of 1 M H3PO4 solution on the material surface, and calcine at 550 °C for 4 h to obtain modified nickel tailings (NCT-β).

[0057] Figure 2 XRD pattern (X-ray diffraction analysis) of the modified nickel tailings (NCT-β) prepared in Example 1; among them, NCT-0 is nickel tailings, NCT-β is the modified nickel tailings material prepared in Example 1, and A-NCT-β is the modified nickel tailings residue separated after the degradation test in Application Example 1. It can be found from the figure that the crystalline substances of the nickel tailings are mainly CaAl2O4·10H2O and SiO2, and after modification, they are mainly CaAl2SiO8·4H2O and part of the calcium-iron mineral phases (Ca2Fe2O5 and Ca2Fe9O 13 ), and a small amount of CaFe3O5 and (Mg,Fe)CO3 appear after the degradation is completed.

[0058] Figure 3 SEM-EDS image (scanning electron microscope energy dispersive spectrometer) of the modified nickel tailings (NCT-β) prepared in Example 1; It can be clearly seen from the figure that the overall modified nickel tailings (NCT-β) is a composite layered nano-folded structure (500 - 1000 nm), which greatly increases its specific surface area. At the same time, iron and nickel elements (with the function of catalyzing persulfate) are distributed on its surface.

[0059] Figure 4 XPS image (X-ray photoelectron spectroscopy analysis) of the modified nickel tailings (NCT-β) prepared in Example 1; The iron and nickel elements in the modified nickel tailings (NCT-β) prepared in Example 1 of the present invention are mainly Fe2O3, FePO4 and NiO. After calcination, the phosphate group will combine with the iron element and adhere to the material surface, which not only protects the material from corrosion but also improves the electron transfer efficiency. And the change of the element map after degradation is not obvious, indicating that the material can maintain good stability during the reaction process.

[0060] Figure 5 ESR image (electron paramagnetic resonance spectrometer) of the modified nickel tailings (NCT-β) prepared in Example 1; It can be seen from the figure that the NCT-β and persulfate system can generate hydroxyl radicals (a) and superoxide radicals (b) (when detecting free radicals, water is used to replace the same volume of RB-19 wastewater. For example, NCT-β + PMS represents the system of NCT-β + water + persulfate).

[0061] Example 2

[0062] Step 1: Place the nickel tailings (NCT-0) in an oven at 80 °C for 48 h, then grind it through a 100-mesh sieve; then perform ball milling (rotation speed of 300 rpm) for 10 min to obtain the pretreated nickel tailings (NCT-0);

[0063] Step 2: Weigh 100 g of the pretreated nickel tailings NCT-0 and mix it with 300 mL of 2 M NaOH solution and 0.5 g of EDTA-2Na; Place the above reactants in a polytetrafluoroethylene conical flask and react in a water bath at 110 °C for 2 h; Then let it stand to remove most of the supernatant and the upper light brown suspended substances, transfer the remaining dark brown substances to a suction filter funnel, filter with suction and wash 5 times with deionized water to obtain the solid NCT-α;

[0064] Step 3: Place the solid NCT-α obtained in Step 2 in a cylindrical crucible, evenly drop 10 mL of 0.5 M H3PO4 solution on the material surface, and calcine at 550 °C for 3 h to obtain the modified nickel tailings (NCT-β).

[0065] Example 3

[0066] Step 1: Place the nickel tailings (NCT-0) in an oven at 80 °C and dry for 48 h, then grind through a 100-mesh sieve; then perform ball milling (rotation speed of 500 rpm) for 10 min to obtain the pretreated nickel tailings (NCT-0);

[0067] Step 2: Weigh 100 g of the pretreated nickel tailings NCT-0, mix it with 200 mL of 4 M NaOH solution and 2 g of EDTA-2Na; place the above reactants in a polytetrafluoroethylene conical flask and react in a water bath at 120 °C for 2 h; then let it stand to remove most of the supernatant and the upper light brown suspension, transfer the remaining dark brown substance to a suction funnel, filter by suction and wash with deionized water 5 times to obtain solid NCT-α;

[0068] Step 3: Place the solid NCT-α obtained in Step 2 in a cylindrical crucible, evenly drop 2 mL of 2 M H3PO4 solution on the material surface, and calcine at 650 °C for 3 h to obtain modified nickel tailings (NCT-β).

[0069] Example 4

[0070] Step 1: Place the nickel tailings (NCT-0) in an oven at 80 °C and dry for 48 h, then grind through a 100-mesh sieve; then perform ball milling (rotation speed of 400 rpm) for 8 min to obtain the pretreated nickel tailings (NCT-0);

[0071] Step 2: Weigh 100 g of the pretreated nickel tailings NCT-0, mix it with 100 mL of 4 M NaOH solution and 1 g of EDTA-2Na; place the above reactants in a polytetrafluoroethylene conical flask and react in a water bath at 110 °C for 3 h; then let it stand to remove most of the supernatant and the upper light brown suspension, transfer the remaining dark brown substance to a suction funnel, filter by suction and wash with deionized water 5 times to obtain solid NCT-α;

[0072] Step 3: Place the solid NCT-α obtained in Step 2 in a cylindrical crucible, evenly drop 4 mL of 1 M H3PO4 solution on the material surface, and calcine at 450 °C for 4 h to obtain modified nickel tailings (NCT-β).

[0073] Example 5

[0074] Step 1: Place the nickel tailings (NCT-0) in an oven at 80 °C and dry for 48 h, then grind through a 100-mesh sieve; then perform ball milling (rotation speed of 400 rpm) for 12 min to obtain the pretreated nickel tailings (NCT-0);

[0075] Step 2: Weigh 100 g of pretreated nickel tailings NCT-0, mix it with 300 mL of 3M NaOH solution and 1 g of EDTA-2Na; place the above reactants in a polytetrafluoroethylene conical flask, and react for 2 h in a water bath at 110 °C; then let it stand to remove most of the supernatant and the upper light brown suspended substances, transfer the remaining dark brown substances to a suction filtration funnel, filter by suction and wash with deionized water 5 times to obtain solid NCT-α;

[0076] Step 3: Place the solid NCT-α obtained in Step 2 in a cylindrical crucible, evenly drop 6 mL of 1M H3PO4 solution on the material surface, and calcine at 450 °C for 5 h to obtain modified nickel tailings (NCT-β).

[0077] Example 6

[0078] Step 1: Place nickel tailings (NCT-0) in an oven at 80 °C and dry for 48 h, then grind it through a 100-mesh sieve; then perform ball milling treatment (rotation speed of 400 rpm) for 10 min to obtain pretreated nickel tailings (NCT-0);

[0079] Step 2: Weigh 100 g of pretreated NCT-0, mix it with 300 mL of 3M NaOH solution and 1 g of EDTA-2Na; place the above reactants in a polytetrafluoroethylene conical flask, and stick a circular thin magnet on the container wall, react in a water bath at 105 °C for 2 h, and perform simple magnetic separation on the material while the water bath reaction is in progress. The separated part of the sample is denoted as NCT-1;

[0080] Step 3: Place the solid NCT-1 obtained in Step 2 in a cylindrical crucible, evenly drop 5 mL of 1M H3PO4 solution on the material surface, and calcine at 550 °C for 4 h to obtain modified nickel tailings NCT-α.

[0081] Step 4: Perform secondary separation on the solid NCT-α obtained in Step 3 by a magnetic separator, with a magnetic field strength of 0.5 T, and the obtained sample is denoted as NCT-I.

[0082] Next, the application performance of the modified nickel tailings prepared in the above examples was tested. In the following application examples: The content and chromaticity of RB-19 in the simulated wastewater (GB 3838-2002) were measured by ultraviolet spectrophotometry, and the content of COD in the simulated wastewater was determined by the dichromate method (GB 11914-89); the pH of the system was adjusted with 0.1M NaOH and 0.1M H2SO4; the persulfate used was potassium persulfate (KPS).

[0083] Application Example 1

[0084] Application of modified nickel tailings in the degradation of RB-19 in wastewater. The specific steps are as follows:

[0085] Experiment 1. The operation process is as Figure 1 shown in the operation flow chart:

[0086] Prepare an RB-19 simulated wastewater with an RB-19 concentration of 50 mg / L by using reactive blue RB-19 solid and deionized water. Take 100 mL of the above-prepared RB-19 simulated wastewater, add 0.5 mg of NCT-β prepared in Example 1 and 0.025 mg of KPS thereto; then adjust the pH value of the system to 2.0, manually shake well to obtain a mixed system, let it stand for 30 min, and then measure the contents of RB-19 and COD in the solution, further calculate the removal rates of RB-19 and COD, and then filter to recover the NCT-β at the bottom.

[0087] Calculate the removal rate of RB-19 in the RB-19 simulated wastewater:

[0088]

[0089] In the formula, D is the removal rate. When calculating the removal rate of RB-19, C0 is the RB-19 concentration of the original system (i.e., the RB-19 simulated wastewater); C is the RB-19 concentration in the system after reacting for 30 min;

[0090] At the same time, calculate the removal rate of COD in the RB-19 simulated wastewater:

[0091]

[0092] In the formula, D is the removal rate. When calculating the removal rate of COD, C′0 is the COD concentration of the original system (the RB-19 simulated wastewater); c is the COD concentration in the system after reacting for 30 min.

[0093] After detection and calculation, in this application example, after reacting for 30 min, the removal rate of RB-19 reaches 99.75%, and the removal rate of COD is 86.97%. In the treated wastewater, the content of RB-19 is 1.295 mg / L, and the chromaticity is 3, which is far lower than the standard of not exceeding 70 stipulated in the National Discharge Standard of Water Pollutants for the Textile Dyeing and Finishing Industry (GB / T 4287-2012), and meets the requirement of the first-class standard of the maximum allowable discharge concentration of the basic control items in the Environmental Quality Standard for Surface Water (GB 3838-2002) not exceeding 30, and can be directly discharged or further recycled.

[0094] Experiments 2 and 3 investigated the removal effects of NCT-β on RB-19 and COD in wastewater under different system pH conditions. The experimental procedure was the same as that of Application Experiment 1 above. The difference was that the system pH was adjusted to 3.0, 4.0, and 5.0 respectively. After 30 min, the removal rates of RB-19 were calculated to be 99.23%, 99.12%, and 98.88% respectively, and the removal rates of COD were 86.01%, 85.18%, and 85.06% respectively.

[0095] Experiments 4 and 5 investigated the removal effects of NCT-0 and NCT-α on RB-19 in wastewater. The experimental procedure was the same as that of Experiment 1 above. The difference was that NCT-β was replaced with equal masses of NCT-0 and NCT-α respectively. After 30 min, the removal rates of RB-19 by NCT-0 and NCT-α were calculated to be 31.88% and 62.47% respectively, and the removal rates of COD were 15.62% and 28.07% respectively.

[0096] In the present invention, the principle of NCT-β degradation is as follows:

[0097] NCT-β catalyzes PMS to generate hydroxyl radicals and sulfate radicals. The former is the main substance attacking RB-19 to achieve the purpose of degradation. The reaction process is as follows:

[0098] SO·4 + OH - →·OH + SO4 2-

[0099] In the NCT-β / PMS system, a strong superoxide radical signal also appeared in the later stage of the reaction. O·2 is a reaction substance jointly generated by PMS / O2 and can further activate persulfate to generate sulfate radicals under aerobic conditions, thereby supplementing the hydroxyl radicals in the system and maintaining the degradation of RB-19.

[0100] Application Example 2

[0101] The application of modified nickel tailings in the degradation of RB-19 in wastewater is as follows:

[0102] Experiment 1: As Figure 1 shown in the operation flowchart: Using solid RB-19 and deionized water to prepare a simulated RB-19 wastewater with a RB-19 concentration of 100.0 mg / L. Take 200 mL of the above simulated RB-19 wastewater, add 2 mg of NCT-β prepared in Example 1 and 0.1 mg of KPS thereto; adjust the pH value of the system to 2.0, manually shake to obtain a mixed system, and measure the contents of RB-19 and COD in the solution after standing for 30 min, calculate their removal rates, and then filter and recover the NCT-β at the bottom.

[0103] After 30 minutes, the removal rate of RB-19 was calculated to be 98.69%, and the COD removal rate was 85.36%. For the treated wastewater, the content of RB-19 was 1.31 mg / L and the chromaticity was 8, far lower than the standard of not exceeding 70 stipulated in the National Discharge Standard of Water Pollutants for the Textile Dyeing and Finishing Industry (GB / T 4287-2012), and meeting the requirement of the first-class standard of the maximum allowable discharge concentration of the basic control items in the Environmental Quality Standard for Surface Water (GB 3838-2002) not exceeding 30, so it can be directly discharged or further used for resource utilization.

[0104] Further, under the same experimental conditions as above, the application performance of the modified nickel tailings prepared in Examples 2-6 was tested (the test sample in Example 6 was NCT-I, and the dosage was 2 mg), and the test results are shown in Table 3 below:

[0105] Table 3

[0106]

[0107] Application Example 3

[0108] The application of the modified nickel tailings in degrading RB-19 in wastewater is as follows:

[0109] Experiment 1: As shown in the Figure 1 operation flow chart: Use solid RB-19 and deionized water to prepare a simulated RB-19 wastewater with a concentration of 200.0 mg / L. Take 400 mL of the above simulated RB-19 wastewater, add 4 mg of NCT-β prepared in Example 1 and 0.2 mg of KPS to it; adjust the pH value of the system to 2.0, manually shake well to obtain a mixed system, and after standing for 30 minutes, measure the contents of RB-19 and COD in the solution and calculate their removal rates, and then filter and recover the modified nickel tailings at the bottom.

[0110] After 30 minutes, the RB-19 removal rate reached 96.58%, and the COD removal rate was 80.17%. For the treated wastewater, the content of RB-19 was 6.84 mg / L and the chromaticity was 16, far lower than the standard of not exceeding 70 stipulated in the National Discharge Standard of Water Pollutants for the Textile Dyeing and Finishing Industry (GB / T 4287-2012), and meeting the requirement of the first-class standard of the maximum allowable discharge concentration of the basic control items in the Environmental Quality Standard for Surface Water (GB 3838-2002) not exceeding 30, so it can be directly discharged or further used for resource utilization.

[0111] Application Example 4

[0112] (I) The application of the recovered modified nickel tailings in degrading RB-19 in wastewater is as follows:

[0113] The NCT-β after the reaction in Application Examples 1-3 (all using the product of Example 1) was recovered by suction filtration. The NCT-β obtained after solid-liquid separation by suction filtration was dried in an oven at 80 °C for 48 h to achieve the regeneration of NCT-β. Then, as Figure 1 shown in the operation flow chart, Experiment 1 in Application Examples 1-3 was repeated respectively. The removal of RB-19 and COD was calculated as shown in Table 4:

[0114] Table 4

[0115]

[0116] As can be seen from Table 4, the recovered NCT-β still has good RB-19 removal performance.

[0117] (2) The reusability of materials is an important indicator for judging the stability and economy of a catalyst. The used NCT-β in Application Example 1 was recovered, ultrasonically rinsed with deionized water, and then dried in an oven at 80 °C for 48 h to achieve the regeneration of NCT-β. Then, it was reused five times according to the steps of Experiment 1 in Application Example 1. The results are as Figure 6 shown.

[0118] As can be seen from the above figure, the NCT-β prepared in Example 1 still has a good degradation efficiency for RB-19 after being recycled and regenerated five times. The degradation efficiency only slightly decreases during each reuse, and the final removal rate can still reach more than 80.29%.

[0119] The above are only preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. Those skilled in the art should be able to realize that all equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of modified nickel tailings, characterized in that, It includes the following steps: S1. The nickel tailings are subjected to drying, sieving and ball milling to obtain pretreated nickel tailings; S2. The pretreated nickel tailings are mixed with NaOH solution and EDTA-2Na, and hydrothermally reacted at a temperature of 100-120 °C for 2-3 h. After solid-liquid separation and washing, a first product is obtained; S3. A phosphoric acid solution is dripped onto the surface of the first product, and then it is calcined in an environment of 450-650 °C for 3-5 h. The calcined product is ground to obtain modified nickel tailings.

2. The preparation method according to claim 1, wherein In step S1, the mesh number of sieving is 100-150 meshes; the rate of ball milling is 300-500 rpm, and the time of ball milling is 5-20 min.

3. The preparation method according to claim 1, characterized in that, In step S2, the mass-volume ratio of the pretreated nickel tailings to the NaOH solution is 1:(1-3) g / mL; the concentration of the NaOH solution is 2-4 mol / L.

4. The preparation method according to claim 3, wherein The mass ratio of the pretreated nickel tailings to EDTA-2Na is 100:(0.5-2).

5. The preparation method according to claim 1, wherein, In step S3, the mass-volume ratio of the first product to the phosphoric acid solution is 100:(2-10) g / mL; the concentration of the phosphoric acid solution is 0.5-2 mol / L.

6. Application of modified nickel tailings in highly efficient catalytic degradation of reactive blue by persulfate, characterized in that, The modified nickel tailings are prepared by the preparation method according to any one of claims 1-5.

7. The application according to claim 6, wherein The modified nickel tailings and persulfate are added to the wastewater containing reactive blue. The mass ratio of the modified nickel tailings to the persulfate is (5-30):

1. The pH of the system is adjusted to 2-5, and after standing for a certain time, the treated wastewater is obtained.

8. The application according to claim 7, wherein In the wastewater containing reactive blue, the concentration of reactive blue is 20-400 mg / L.

9. The application according to claim 7, characterized in that, The application further includes: recovering the modified nickel tailings after treating the wastewater by means of suction filtration or magnetic attraction, fully drying the recovered modified nickel tailings, and reusing them for treating the wastewater containing reactive blue.

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