Ultrasonic-assisted equipment and method for preparing sodium ferrate from red mud

Abstract

The invention relates to ultrasonic-assisted equipment for preparing sodium ferrate from red mud, which comprises a reaction kettle, a heating plate, a vibrating plate, a red mud alkaline leaching residue slurry storage tank, a sodium hypochlorite storage tank, a temperature measuring element and a stirrer device, and is characterized in that the heating plate and the vibrating plate are sequentially arranged at the bottom of the reaction kettle, and the heating plate is attached to the bottom of the reaction kettle; an ultrasonic vibration head is arranged at the bottom of the vibration plate; the temperature measuring element is arranged on the reaction kettle through a connecting piece, and a temperature measuring probe of the temperature measuring element extends into the reaction kettle; the stirrer device is arranged above the reaction kettle through a fixed bracket, and a stirring rod of the stirrer device extends into the reaction kettle; the red mud alkaline leaching residue slurry storage tank is communicated with the red mud alkaline leaching residue slurry inlet; and the sodium hypochlorite storage tank is communicated with the sodium hypochlorite feeding hole. The sodium ferrate prepared by the method is high in concentration, high in generation rate and high in process safety, and ultrasonic equipment is simple in structure and low in cost.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of high - iron red mud solid waste, and relates to an apparatus and method for preparing sodium ferrate from red mud assisted by ultrasound. Background Art

[0002] Red mud is an alkaline by - product generated during the production of alumina from bauxite. It contains various chemical components, mainly including iron oxide, alumina, titanium oxide, silicon dioxide, sodium oxide, etc. Among them, the content of iron oxide is relatively high, usually exceeding 30%, which is why it is called high - iron red mud. Red mud particles are fine and have a large specific surface area, usually between 10 - 30 m 2 / g, which is closely related to the grinding degree of bauxite. At the same time, high - iron red mud also has a certain plasticity and a relatively high porosity. In addition, the pH value of high - iron red mud is 10.0 - 12.0, showing strong alkalinity, and it belongs to Class II general industrial solid waste, which is one of the main reasons why it is regarded as a harmful industrial waste residue.

[0003] Traditional treatment methods are divided into dam - building storage and sea - dumping. A large amount of alkaline substances and heavy metals contained in red mud, if directly discharged without treatment, will not only occupy a large amount of land resources, but also cause serious pollution to the surrounding soil, water bodies and ecological systems. Dumping into the sea seriously pollutes groundwater and marine ecology and endangers human health. In addition, due to its characteristics such as high water content, high compressibility and good plasticity, red mud is used as building raw materials such as concrete, new wall materials, plastic fillers, road base materials, anti - seepage materials, paving materials, etc., and has broad application prospects, thus realizing the recycling of resources. Therefore, when dealing with and utilizing high - iron red mud, it is necessary to comprehensively consider its various characteristics and adopt scientific and reasonable processes and technical means to achieve its resource utilization and harmless treatment.

[0004] Since the iron grade in high - iron red mud is relatively high and it contains various valuable elements, it is regarded as a precious secondary resource. Therefore, recovering iron elements from high - iron red mud is an important research direction for red mud resource utilization. In order to improve the comprehensive utilization rate of high - iron red mud and reduce production costs, it is necessary to develop an apparatus and method for preparing sodium ferrate from red mud assisted by ultrasound, turning red mud into a valuable resource and achieving the goal of saving resources and protecting the environment. Summary of the Invention

[0005] Object of the Invention

[0006] To solve the above - mentioned problem of resource utilization of high - iron red mud solid waste, the present invention provides an apparatus and method for preparing sodium ferrate from red mud assisted by ultrasound, aiming to efficiently synthesize sodium ferrate from the iron elements in high - iron red mud to ensure the high - value recycling of high - iron red mud.

[0007] Technical Solution

[0008] An apparatus for preparing sodium ferrate from red mud assisted by ultrasound, comprising a reaction kettle, a heating plate, a vibration plate, a storage tank for red mud alkaline leaching residue slurry, a sodium hypochlorite storage tank, a temperature measuring element and a stirrer device.

[0009] The reaction kettle is provided with a feeding port for red mud alkaline leaching residue slurry, a feeding port for sodium hypochlorite and a discharging port; the heating plate and the vibration plate are sequentially arranged at the bottom of the reaction kettle, and the heating plate is in contact with the bottom of the reaction kettle, and an ultrasonic vibration head is arranged at the bottom of the vibration plate.

[0010] The temperature measuring element is arranged on the reaction kettle through a connecting piece, and the temperature measuring probe of the temperature measuring element extends into the reaction kettle.

[0011] The stirrer device is arranged above the reaction kettle through a fixing bracket, and the stirring rod of the stirrer device extends into the reaction kettle.

[0012] The storage tank for red mud alkaline leaching residue slurry is communicated with the feeding port for red mud alkaline leaching residue slurry; the sodium hypochlorite storage tank is communicated with the feeding port for sodium hypochlorite.

[0013] As a further description of the above solution, it further comprises a fixed base, the fixed base is provided with a fixing frame, and the vibration plate and the heating plate are sequentially fixed on the fixing frame.

[0014] As a further description of the above solution, it further comprises a slurry pump. The reaction kettle is of a ring structure, and the reaction kettle is a closed space surrounded by a top wall, a side wall and a bottom wall; the slurry pump is installed inside the reaction kettle, and the feeding end and the discharging end of the slurry pump face in opposite directions. When the slurry pump operates, it can drive the solution in the reaction kettle to circulate in the ring structure of the reaction kettle; the number of the heating plates and the vibration plates is greater than or equal to 1, and the temperature measuring element is a thermocouple or a thermal resistor.

[0015] As a further description of the above solution, the stirrer device is fixedly arranged on the fixing bracket through a connecting piece; a plurality of ultrasonic vibration heads are arranged; the slurry pump is a pneumatic slurry pump, and the pneumatic slurry pump is connected with an external air source through an air pipe; the discharging port is connected with a discharging pipe, a valve is arranged on the discharging pipe, and both the discharging pipe and the slurry pump are made of stainless steel.

[0016] As a further description of the above solution, it further comprises a peristaltic pump and a feeding pipe. The storage tank for red mud alkaline leaching residue slurry is communicated with the feeding port for red mud alkaline leaching residue slurry through the feeding pipe, and the feeding pipe is provided with a peristaltic pump and a flowmeter.

[0017] The sodium hypochlorite storage tank is communicated with the feeding port for sodium hypochlorite through the feeding pipe, and the feeding pipe is provided with a peristaltic pump and a flowmeter.

[0018] As a further description of the above solution, the agitator device is electrically connected to power supply a, and the ultrasonic vibration head is electrically connected to power cord b.

[0019] A method for preparing sodium ferrate based on ultrasonic-assisted red mud using the above equipment includes the following steps:

[0020] Step 1: Put the red mud alkali leaching residue of high-iron into a vacuum drying oven for drying. After drying, take it out and grind it into powder with the size controlled at 200 - 250 mesh.

[0021] Step 2: Mix the sodium hydroxide solution and the red mud alkali leaching residue of high-iron evenly to make a slurry, and inject it into the storage tank for red mud alkali leaching residue slurry.

[0022] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump and enter it into the ultrasonic circulation-assisted heating reactor from the feed port of the red mud alkali leaching residue slurry, and react with the sodium hypochlorite solution injected from the other side's sodium hypochlorite feed port to prepare sodium ferrate.

[0023] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times.

[0024] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0025] As a further description of the above solution, in Step 2, the concentration of the sodium hydroxide solution used is 8 - 18 mol / L; in Step 3, the concentration of sodium hypochlorite is 1.13 - 1.41 mol / L, and the solid-liquid ratio of the red mud alkali leaching residue to the two reagents used is 1:20 - 1:70 kg / L. Under the action of ultrasonic waves, hydroxyl radicals are generated in the mixed solution of the reactor.

[0026] As a further description of the above solution, in Step 3, the feeding flow rate of the red mud alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, and the feeding flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h; after the feeding of the red mud alkali leaching residue slurry and the sodium hypochlorite solution is completed, start the heating plate to heat to 55 - 75 °C, then turn on the switches of the agitator device, the slurry pump and the ultrasonic vibration head to make the mixed solution flow, and perform ultrasonic vibration and stirring; the ultrasonic power of the ultrasonic vibration head is 480 - 600 W, the rotation speed of the stirring device is 300 - 400 rpm, and the time of both ultrasonic vibration and stirring is 10 - 35 min. After the reaction is completed, turn on the valve switch of the discharge pipe to make the product flow out through the discharge pipe, and the flow rate of the slurry pump is 0.25 - 0.3 m 3 / h.

[0027] Advantages and effects

[0028] 1. The present invention prepares sodium ferrate(VI) in a reaction kettle made of stainless steel, which is alkali-resistant and light-shielding, so that the prepared sodium ferrate(VI) will not decompose due to light exposure. The red mud alkali leaching residue slurry and sodium hypochlorite solution are fed according to the set flow rate, breaking the traditional direct addition method and making the contact and mixing between different components more sufficient.

[0029] 2. A method for preparing sodium ferrate(VI) by ultrasonic-assisted red mud innovatively applies ultrasonic waves to the process of preparing sodium ferrate(VI). The cavitation effect generated by ultrasonic waves can not only accelerate the mass transfer process, improve the oxidation performance of the solution by generating hydroxyl radicals, and promote the oxidation of ferric oxide in the alkali leaching residue to hexavalent iron; the addition of ultrasonic waves not only increases the formation rate of sodium ferrate(VI), but also shortens the reaction time. Compared with the process of directly preparing sodium ferrate(VI), the sodium ferrate(VI) prepared by the present invention has a high concentration, a fast formation rate, high process safety, a simple ultrasonic equipment structure, and low equipment cost. The concentration of sodium ferrate(VI) synthesized after ultrasonic assistance reaches a good effect, and the concentration of synthesized sodium ferrate(VI) is not less than 12 mmol / L. This shows that the ultrasonic-assisted method of the present invention realizes the efficient preparation of sodium ferrate(VI). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the drawings and specific embodiments. The protection scope of the present invention is not limited to the description of the following content.

[0031] Figure 1 is a schematic structural diagram of the equipment for preparing sodium ferrate(VI) by ultrasonic-assisted red mud according to the embodiment of the present invention;

[0032] Figure 2 is the influence of different ultrasonic powers on the concentration of hydroxyl radicals generated under ultrasonic assistance of the present invention;

[0033] Figure 3 is Figure 1 the schematic connection structure diagram of the stirrer device and the fixed bracket in

[0034] Description of the reference numerals in the drawings:

[0035] 1. Reaction kettle, 2. Stirring rod, 3. Temperature measuring element, 4. Slurry pump, 5. Red mud alkali leaching residue slurry feed inlet, 6. Sodium hypochlorite feed inlet, 7. Discharge port, 8. Heating plate, 9. Vibration plate, 10. Ultrasonic vibration head, 11. Fixed base, 12. Stirrer device, 13. Flowmeter, 14. Peristaltic pump, 15. Red mud alkali leaching residue slurry storage tank, 16. Feed pipe, 17. Ultrasonic reaction zone, 18. Power supply a, 19. Power supply b, 20. Fixed frame, 21. Sodium hypochlorite storage tank, 22. Connector, 23. Fixed bracket, 24. Fixed nail, 25. Vent pipe.

[0036] The specific implementation method is through

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] An apparatus for preparing sodium ferrate from red mud by ultrasonic assistance according to an embodiment of the present invention includes a reaction kettle 1, a heating plate 8, a vibration plate 9, a red mud alkali leaching residue slurry storage tank 15, a sodium hypochlorite storage tank 21, a temperature measuring element and a stirrer device 12. The reaction kettle 1 is provided with a red mud alkali leaching residue slurry inlet 5, a sodium hypochlorite inlet 6 and a discharge port 7. Specifically, a predetermined distance is provided between the red mud alkali leaching residue slurry inlet 5 and the sodium hypochlorite inlet 6 to avoid the situation that the alkali leaching residue slurry may be quickly washed down by the sodium hypochlorite solution before being fully dispersed when they are too close, resulting in local accumulation of the alkali leaching residue slurry in the sodium hypochlorite solution and making it difficult to form a uniform mixture, which affects the subsequent reaction. The heating plate 8 and the vibration plate 9 are sequentially arranged at the bottom of the reaction kettle 1, and the heating plate 8 is in contact with the bottom of the reaction kettle 1. An ultrasonic vibrator head 10 is provided at the bottom of the vibration plate 9.

[0039] The temperature measuring element is arranged on the reaction kettle 1 through a connecting piece, and the temperature measuring probe of the temperature measuring element 3 extends into the reaction kettle 1. The stirrer device 12 is arranged above the reaction kettle 1 through a fixed bracket 23, and the stirring rod 2 of the stirrer device 12 extends into the reaction kettle 1. The red mud alkali leaching residue slurry storage tank 15 is communicated with the red mud alkali leaching residue slurry inlet 5. The sodium hypochlorite storage tank 21 is communicated with the sodium hypochlorite inlet 6. The present invention prepares sodium ferrate from the alkali leaching residue after sodium roasting-alkali leaching of red mud. Sodium ferrate has strong oxidizing properties and can release a large amount of oxygen atoms when dissolved in water, which can efficiently remove bacteria, viruses, heavy metal ions and organic substances in water without producing any harmful by-products. It is regarded as a green disinfectant and is widely used in many fields such as urban sewage treatment, industrial wastewater treatment, and drinking water purification. This design prepares sodium ferrate in the reaction kettle 1. The reaction kettle 1 is made of stainless steel, which has alkali resistance and can also avoid light, so that the prepared sodium ferrate will not decompose due to exposure to light. The red mud alkali leaching residue slurry and the sodium hypochlorite solution are fed according to the set flow rate, breaking the traditional direct addition method and making the contact and mixing between different components more sufficient.

[0040] The device for preparing sodium ferrate from red mud by ultrasonic assistance according to the embodiment of the present invention further includes a fixed base 11, wherein the fixed base 11 is provided with a fixing frame 20, and a vibrating plate 9 and a heating plate 8 are sequentially and fixedly arranged on the fixing frame 20. Specifically, there are two fixing frames 20, and the cross-section of the fixing frame 20 is an L-shaped structure; two symmetrical installation grooves are formed in the top surface of the fixed base 11, and the bottom of each fixing frame 20 is fixedly arranged in the installation groove, and the vibrating plate 9 and the heating plate 8 are fixed to the fixing frame 20 by bolts.

[0041] The device for preparing sodium ferrate from red mud by ultrasonic assistance according to the embodiment of the present invention further includes a slurry pump 4. The reaction kettle is of a ring structure. The reaction kettle 1 is a closed space surrounded by a top wall, a side wall and a bottom wall. When the solution flows in the annular channel of the annular reaction kettle 1, it is easier to form a relatively stable circulation flow, which is beneficial to the circulation and mixing of the solution and is more favorable for the process of uniform mixing and continuous reaction. Moreover, the heat transfer area of the annular reaction kettle 1 is relatively large, and when the solution flows in the annular channel, the contact with the kettle wall is relatively uniform, which is beneficial to heat transfer; the slurry pump 4 is installed inside the reaction kettle 1, and the feeding end and the discharging end of the slurry pump 4 face in opposite directions. When the slurry pump 4 operates, it can drive the solution in the reaction kettle 1 to circulate in the annular structure of the reaction kettle 1, so that the solution is mixed more uniformly; the number of the heating plates 8 and the vibrating plates 9 is greater than or equal to 1. The temperature measuring element 3 is a thermocouple or a thermal resistor. The function of the temperature measuring element is to measure the temperature when the reaction occurs in the reaction kettle 1. Specifically, the thermocouple is arranged on the outer wall of the reaction kettle 1 through a fixing nail 24, and then the temperature measuring probe of the thermocouple extends into the interior of the reaction kettle 1.

[0042] A plurality of stirrer devices 12 are arranged in the embodiment of the present invention. Each stirrer device 12 is fixedly arranged on a fixed bracket 23 through a connecting member 22, and the stirring rod 2 of the stirrer device 12 passes through the fixed bracket 23 and extends into the reaction kettle 1; a plurality of ultrasonic vibration heads 10 are provided. Specifically, the fixed base 11 is provided with a fixed groove matching the ultrasonic vibration head 10, and the bottom of the ultrasonic vibration head 10 is fixedly arranged in the fixed groove, so that when the ultrasonic vibration head 10 vibrates, the whole device will not be affected, and the wear or damage of the device components is reduced; the slurry pump 4 is a pneumatic slurry pump, and the pneumatic slurry pump is connected to an external air source through an air pipe 25; the discharge port 7 is connected with a discharge pipe, and a valve is arranged on the discharge pipe. Both the discharge pipe and the slurry pump 4 are made of stainless steel.

[0043] The equipment for preparing sodium ferrate from red mud by ultrasonic assistance according to the embodiment of the present invention further includes a peristaltic pump 14 and a feed pipe 16. The red mud alkaline leaching residue slurry storage tank 15 is connected to the red mud alkaline leaching residue slurry feed port 5 through the feed pipe 16, and the feed pipe 16 is provided with a peristaltic pump 14 and a flow meter 13. The sodium hypochlorite storage tank 21 is connected to the sodium hypochlorite feed port 6 through the feed pipe 16, and the feed pipe 16 is provided with a peristaltic pump 14 and a flow meter 13. During operation, the feed port 5 of the red mud alkaline leaching residue slurry enters the reaction kettle 1 through the peristaltic pump 14 via the feed pipe 16, and the sodium hypochlorite feed port 6 enters the reaction kettle 1 through the peristaltic pump 14 via the feed pipe 16. The end of the feed pipe 16 is connected with a flow meter 13. The red mud alkaline leaching residue slurry storage tank 15 is filled with red mud alkaline leaching residue slurry, and the sodium hypochlorite storage tank 21 is filled with sodium hypochlorite solution. The feeding speed of the materials is adjusted by the flow meter 13. If the feeding speed is too fast, the mass transfer and heat transfer processes in the reaction system may not be able to keep up in time, resulting in too high a concentration of local reactants and a relatively low concentration in other areas, and the reaction cannot proceed fully, and the overall reaction rate will decrease instead. A slow feeding speed directly leads to a reduction in the amount of reactants entering the reaction system, and the amount of products generated within a certain period of time will also decrease accordingly, reducing the production efficiency. The inside of the reaction kettle 1 is an ultrasonic reaction zone 17, which is used as a place for preparing sodium ferrate.

[0044] The stirrer device 12 of the embodiment of the present invention is electrically connected to the power supply a18, and the ultrasonic vibration head 10 is electrically connected to the power supply line b19.

[0045] A method for preparing sodium ferrate from red mud by ultrasonic assistance using the above equipment includes the following steps:

[0046] Step 1: Put the red mud alkaline leaching residue of high iron into a vacuum drying oven for drying. After drying, take it out and grind it into powder with a size controlled at 200-250 mesh.

[0047] Step 2: Mix the sodium hydroxide solution and the red mud alkaline leaching residue of high iron evenly to make a slurry, and inject it into the red mud alkaline leaching residue slurry storage tank 15, where the concentration of the sodium hydroxide solution used is 8-18 mol / L.

[0048] Step 3: Transfer the slurry obtained in Step 2 through the peristaltic pump 14 and enter the ultrasonic circulation assisted heating reaction kettle 1 from the red mud alkaline leaching residue slurry feed port 5 to react with the sodium hypochlorite solution injected from the other sodium hypochlorite feed port 6 to prepare sodium ferrate. The concentration of the sodium hypochlorite used is 1.13-1.41 mol / L, and the solid-liquid ratio of the red mud alkaline leaching residue of high iron to the two reagents is 1:20-1:70 kg / L. Under the action of ultrasonic waves, hydroxyl radicals are generated in the mixed solution in the reaction kettle 1. In Step 3, the feeding flow rate of the red mud alkaline leaching residue slurry is 0.15-0.3 m 3 / h, and the feeding flow rate of sodium hypochlorite is 0.2-0.3 m3 / h; After the red mud alkaline leaching residue slurry and the sodium hypochlorite solution are fed, start heating the heating plate 8 to 55-75 °C, then turn on the switches of the stirrer device 12, the slurry pump 4 and the ultrasonic vibrator head 10 to make the mixed solution flow, and perform ultrasonic vibration and stirring; among them, the ultrasonic power of the ultrasonic vibrator head 10 is 480-600 W, the rotation speed of the stirring device 12 is 300-400 rpm, and the time of ultrasonic vibration and stirring is both 10-35 min. After the reaction is completed, turn off the switches of the stirrer device 12, the slurry pump 4 and the ultrasonic vibrator head 10, and turn on the valve switch of the discharge pipe to make the product flow out through the discharge pipe. The flow rate of the slurry pump 4 is 0.25-0.3 m 3 / h;

[0049] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge and centrifuge it 3-5 times to remove excess impurities;

[0050] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0051] In Step 3 of the present invention, the mechanism of ultrasonic promotion of sodium ferrate formation can be divided into physical effects and chemical effects:

[0052] In terms of physical effects: The cavitation effect caused by ultrasonic waves breaks the intermolecular attraction of the liquid-phase medium molecules, and cavitation nuclei with a lifespan of about 0.1 μs are formed in the solution. The explosion of cavitation nuclei generates high-speed microjets in the solution. The high-speed microjets generate strong impact forces at the liquid-solid interface, break the solid film layer at the contact interface, reduce the liquid film thickness between the contact interfaces, and shorten the reaction diffusion path. The sodium ferrate formed on the surface of the alkaline leaching residue quickly diffuses into the solution, and the unreacted iron(III) oxide in the alkaline leaching residue can quickly contact with the sodium hydroxide and sodium hypochlorite solutions to continue to generate sodium ferrate, improving the formation efficiency of sodium ferrate.

[0053] In terms of chemical effects: The cavitation nucleus explosion generated by ultrasonic waves instantaneously triggers local high temperature and high pressure, forming local "hot spots", which promotes the cleavage of the O-H bond in water molecules to generate hydroxyl radicals, as shown in the following reaction. Hydroxyl radicals are strong oxidants, which can increase the oxidation potential of the system, improve the oxidation performance of the sodium ferrate synthesis system, and further promote the oxidation of iron(III) oxide in the alkaline leaching residue to sodium ferrate. The reaction equation for preparing sodium ferrate from iron(III) oxide is shown below. Through EPR tests at different ultrasonic powers, it can be seen that as the ultrasonic power increases, the diffraction peak of hydroxyl radicals increases, the concentration of hydroxyl radicals also increases, and the oxidizing property in the solution also increases. The test results are shown in the attached Figure 2 .

[0054] H2O → H· + ·OH

[0055] Fe2O3 + 4NaOH + 3NaClO → 2Na2FeO4 + 3NaCl + 2H2O

[0056] The present invention is further illustrated below by specific experimental examples as follows:

[0057] Example 1

[0058] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0059] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud;

[0060] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed port, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0061] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0062] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0063] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the alkali-leached residue of high-iron red mud to the two reagents is 1:20 kg / L, the feed flow rate of the alkali-leached residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0064] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0065] The concentration of sodium ferrate prepared in this example is 12.76 mmol / L.

[0066] Example 2

[0067] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0068] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud;

[0069] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0070] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge and centrifuge it 3 - 5 times to remove excess impurities;

[0071] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0072] In Step 3, the concentration of sodium hydroxide used is 13 mol / L, the concentration of sodium hypochlorite is 1.3 mol / L, the solid-liquid ratio of red mud alkali leaching residue to the two reagents is 1:50 kg / L, the feed flow rate of the alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, and the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0073] In Step 3, the reaction temperature is 65 °C, the ultrasonic power is 600 W, and the ultrasonic time is 20 min.

[0074] In this example, the concentration of the prepared sodium ferrate is 13.12 mmol / L.

[0075] Example 3

[0076] Step 1: Put the red mud alkali leaching residue of high iron into a vacuum drying oven to dry it. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0077] Step 2: Mix the sodium hydroxide solution and the red mud alkali leaching residue of high iron evenly to make a slurry, and inject it into the red mud alkali leaching residue slurry storage tank 15;

[0078] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0079] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge and centrifuge it 3 - 5 times to remove excess impurities;

[0080] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0081] In Step 3, the concentration of sodium hydroxide used is 18 mol / L, the concentration of sodium hypochlorite is 1.41 mol / L, the solid-liquid ratio of red mud alkali leaching residue of high iron to the two reagents is 1:70 kg / L, the feed flow rate of the alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0082] In step 3, the reaction temperature is 75 °C, the ultrasonic power is 600 W, and the ultrasonic time is 35 min.

[0083] The concentration of sodium ferrate prepared in this example is 12.83 mmol / L.

[0084] Comparative Example 1

[0085] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0086] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 of the alkali-leached residue slurry of red mud;

[0087] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter the ultrasonic circulation-assisted heating reaction kettle 1 from the feed port to react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0088] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0089] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0090] In the said Step 3, the concentration of sodium hydroxide used is 6 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the alkali-leached residue of red mud to the two reagents is 1:20 kg / L, and the feed flow rate of the alkali-leached residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0091] In step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0092] The concentration of sodium ferrate prepared in this example is 11.94 mmol / L.

[0093] Comparative Example 2

[0094] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0095] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of red mud containing iron(III) oxide evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud containing iron(III) oxide;

[0096] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0097] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge and centrifuge it 3 - 5 times to remove excess impurities;

[0098] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0099] In Step 3, the concentration of the sodium hydroxide used is 19 mol / L, the concentration of the sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the alkali-leached residue of red mud containing iron(III) oxide to the two reagents is 1:20 kg / L, the feed flow rate of the alkali-leached residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of the sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0100] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0101] The concentration of the sodium ferrate prepared in this example is 12.01 mmol / L.

[0102] Comparative Example 3

[0103] Step 1: Put the alkali-leached residue of red mud containing iron(III) oxide into a vacuum drying oven for drying, take it out after drying and grind it into powder, and control the particle size within 200 - 250 mesh;

[0104] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of red mud containing iron(III) oxide evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud containing iron(III) oxide;

[0105] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0106] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge and centrifuge it 3 - 5 times to remove excess impurities;

[0107] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0108] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 0.8 mol / L, the solid-liquid ratio of red mud alkali leaching residue to the two reagents is 1:20 kg / L, and the feed flow rate of the alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0109] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0110] The concentration of sodium ferrate prepared in this example is 11.65 mmol / L.

[0111] Comparative Example 4

[0112] Step 1: Put the red mud alkali leaching residue of high-iron into a vacuum drying oven for drying. After drying, take it out and grind it into powder with the size controlled at 200 - 250 mesh;

[0113] Step 2: Mix the sodium hydroxide solution and the red mud alkali leaching residue of high-iron evenly to make a slurry, and inject it into the storage tank 15 of the alkali leaching residue slurry;

[0114] Step 3: Transfer the slurry obtained in Step 2 through the peristaltic pump 14 and enter the ultrasonic circulation-assisted heating reaction kettle 1 from the feed port to react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0115] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0116] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0117] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.7 mol / L, the solid-liquid ratio of red mud alkali leaching residue to the two reagents is 1:20 kg / L, and the feed flow rate of the alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0118] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0119] The concentration of sodium ferrate prepared in this example is 11.85 mmol / L.

[0120] Comparative Example 5

[0121] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh.

[0122] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud.

[0123] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it from the feed port into the ultrasonic circulation-assisted heating reaction kettle 1, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate.

[0124] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities.

[0125] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0126] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the alkali-leached residue of red mud to the two reagents is 1:10 kg / L, the feeding flow rate of the alkali-leached residue slurry is 0.15 - 0.3 m 3 / h, the feeding flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0127] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0128] In this example, the concentration of the prepared sodium ferrate is 10.26 mmol / L.

[0129] Comparative Example 6

[0130] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh.

[0131] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry of red mud.

[0132] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it from the feed port into the ultrasonic circulation-assisted heating reaction kettle 1, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate.

[0133] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities.

[0134] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0135] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of red mud alkali leaching residue to the two reagents is 1:80 kg / L, the feeding flow rate of alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feeding flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0136] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0137] In this example, the concentration of sodium ferrate prepared is 10.43 mmol / L.

[0138] Comparative Example 7

[0139] Step 1: Put the red mud alkali leaching residue of high-iron into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh;

[0140] Step 2: Mix the sodium hydroxide solution and the red mud alkali leaching residue evenly to make a slurry, and inject it into the storage tank 15 of alkali leaching residue slurry;

[0141] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter from the feed port into the ultrasonic circulation-assisted heating reactor 1 to react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0142] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0143] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0144] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of red mud alkali leaching residue to the two reagents is 1:20 kg / L, the feeding flow rate of alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feeding flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0145] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 240 W, and the ultrasonic time is 10 min.

[0146] In this example, the concentration of sodium ferrate prepared is 11.17 mmol / L.

[0147] Comparative Example 8

[0148] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled within 200 - 250 mesh.

[0149] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry.

[0150] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate.

[0151] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities.

[0152] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0153] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the alkali-leached residue of red mud to the two reagents is 1:20 kg / L, the feed flow rate of the alkali-leached residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0154] In Step 3, the reaction temperature is 30 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0155] In this example, the concentration of sodium ferrate prepared is 8.39 mmol / L.

[0156] Comparative Example 9

[0157] Step 1: Put the alkali-leached residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled within 200 - 250 mesh.

[0158] Step 2: Mix the sodium hydroxide solution and the alkali-leached residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 for the alkali-leached residue slurry.

[0159] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate.

[0160] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0161] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0162] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid - liquid ratio of red mud alkali - leaching residue to the two reagents is 1:20 kg / L, the feed flow rate of the alkali - leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0163] In Step 3, the reaction temperature is 90 °C, the ultrasonic power is 480 W, and the ultrasonic time is 10 min.

[0164] In this example, the concentration of the prepared sodium ferrate is 10.14 mmol / L.

[0165] Comparative Example 10

[0166] Step 1: Put the red mud alkali - leaching residue of high - iron into a vacuum drying oven for drying. After drying, take it out and grind it into powder with the size controlled at 200 - 250 mesh;

[0167] Step 2: Mix the sodium hydroxide solution and the red mud alkali - leaching residue evenly to make a slurry, and inject it into the red mud alkali - leaching residue slurry storage tank 15;

[0168] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it from the feed port into the ultrasonic - circulation assisted heating reactor 1 to react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate;

[0169] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities;

[0170] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0171] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid - liquid ratio of red mud alkali - leaching residue to the two reagents is 1:20 kg / L, the feed flow rate of the alkali - leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0172] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 5 min.

[0173] In this example, the concentration of sodium ferrate prepared is 9.33 mmol / L.

[0174] Comparative Example 11

[0175] Step 1: Put the sodium-immobilized roasting alkali leaching residue of high-iron red mud into a vacuum drying oven for drying. After drying, take it out and grind it into powder, with the size controlled at 200 - 250 mesh.

[0176] Step 2: Mix the sodium hydroxide solution and the sodium-immobilized roasting alkali leaching residue of high-iron red mud evenly to make a slurry, and inject it into the storage tank 15 of the red mud alkali leaching residue slurry.

[0177] Step 3: Transfer the slurry obtained in Step 2 through a peristaltic pump 14 and enter it into the ultrasonic circulation-assisted heating reactor 1 from the feed inlet, and react with the sodium hypochlorite solution injected from the other side to prepare sodium ferrate.

[0178] Step 4: Put the sodium ferrate solution obtained in Step 3 into a centrifuge for centrifugal separation 3 - 5 times to remove excess impurities.

[0179] Step 5: A pure sodium ferrate solution can be obtained through Step 4.

[0180] In Step 3, the concentration of sodium hydroxide used is 8 mol / L, the concentration of sodium hypochlorite is 1.13 mol / L, the solid-liquid ratio of the red mud alkali leaching residue to the two reagents is 1:20 kg / L, the feed flow rate of the alkali leaching residue slurry is 0.15 - 0.3 m 3 / h, the feed flow rate of sodium hypochlorite is 0.2 - 0.3 m 3 / h, and the flow rate of the slurry pump 4 is 0.25 - 0.3 m 3 / h.

[0181] In Step 3, the reaction temperature is 55 °C, the ultrasonic power is 480 W, and the ultrasonic time is 50 min.

[0182] In this example, the concentration of sodium ferrate prepared is 11.51 mmol / L.

[0183] The main component contents of the sodium-immobilized roasting alkali leaching residue of high-iron red mud used in the above examples are shown in Table 1.

[0184] Table 1

[0185] Component <![CDATA[Fe2O3]]> <![CDATA[NaAlSiO4]]> <![CDATA[Na2Ti6O 13 > Content % 84.36％～86.04％ 3.72％～5.58％ 6.82％～8.23％

[0186] The concentration values of sodium ferrate synthesized under various influencing factors after ultrasonic assistance in the above examples and comparative examples are shown in Table 2.

[0187] Table 2

[0188]

[0189]

[0190] The flow rate parameter of the slurry feed pump is 0.15~0.3m 3 / h, the flow rate parameter of sodium hypochlorite feed pump is 0.2~0.3m 3 / h, the flow rate parameter of the slurry pump is 0.25~0.3m 3 / h, the above three parameters are fixed values.

[0191] From the data of the embodiments and comparative examples, it can be seen that:

[0192] (1) It can be seen from the data in Table 2 of Examples 1 to 3 that the process of the embodiment of the present invention can prepare sodium ferrate at the specified sodium hydroxide concentration, sodium hypochlorite concentration, the ratio of high-iron red mud alkali leaching residue to the two reagents, the ultrasonic power, the ultrasonic time and the reaction temperature to obtain a sodium ferrate solution with a relatively high concentration.

[0193] (2) From the data in Table 2 of Comparative Examples 1 to 2, it can be seen that when the concentration of sodium hydroxide used does not reach the standard specified in the present invention, the concentration of the prepared sodium ferrate is relatively low, mainly because in the process of preparing sodium ferrate, the conversion of ferric oxide to hexavalent iron requires a strong alkaline system; when the concentration of sodium hydroxide used is greater than the standard specified in the present invention, the excessively high concentration of sodium hydroxide increases the viscosity of the solution, and a high-viscosity solution is not conducive to the synthesis of sodium ferrate.

[0194] (3) From the data in Table 2 of Comparative Examples 3 to 4, it can be seen that when the concentration of sodium hypochlorite used does not reach the standard specified in the present invention, the reaction is incomplete, and unreacted impurities such as ferric oxide will remain, thereby reducing the concentration of sodium ferrate; when the concentration of sodium hypochlorite used is greater than the standard specified in the present invention, when the concentration is too high and a side reaction is triggered, some other oxidation products or by-products will be generated. These impurities will be mixed into the product, which will also reduce the concentration of sodium ferrate.

[0195] (4) By comparing Examples 5 to 6, the data in Table 2 show that: the concentration of sodium ferrate generated will be reduced when the ratio of high-iron red mud alkali leaching residue to the two reagents is too large or too small. When the ratio is too large, the local reactant concentration is too high, which reduces the selectivity and purity of the main product and may cause some unnecessary side reactions. When the ratio is too small, the solid reactant may be over-dispersed, the contact between the reactants is insufficient, and the generation rate of the product is reduced.

[0196] (5) From Comparative Example 7 and the data in Table 2, it can be seen that when the ultrasonic power used does not reach the standard defined in the present invention, the concentration of sodium ferrate prepared needs to be further improved, and the influence of ultrasonic power on the preparation of sodium ferrate is significant.

[0197] (6) From Comparative Examples 8 - 9 and the data in Table 2, it can be seen that when the ultrasonic temperature used does not reach the standard defined in the present invention, at low temperatures, the reaction rate between substances such as sodium hypochlorite and iron(III) oxide will decrease significantly, resulting in an extended time required for the reaction to reach equilibrium; when the ultrasonic temperature used is greater than the standard defined in the present invention, too high a temperature will promote the decomposition of sodium hypochlorite, thereby reducing the oxidizing property of the synthesis system, and the concentration of sodium ferrate will also decrease accordingly.

[0198] (7) From Comparative Examples 10 - 11 and the data in Table 2, it can be seen that when the ultrasonic time used does not reach the standard defined in the present invention, the amount of sodium ferrate generated is small; when the ultrasonic time used is greater than the standard defined in the present invention, too long a reaction time promotes the thermal decomposition of sodium ferrate, resulting in a decrease in the concentration of sodium ferrate.

[0199] In summary, the ultrasonic - assisted method proposed in the embodiments of the present invention promotes the synthesis of sodium ferrate, not only shortening the reaction time but also improving the reaction efficiency. The preparation method of the present invention improves the oxidizing property of the reaction system through the hydroxyl radicals generated by ultrasonic waves, and the ultrasonic vibration can greatly accelerate the diffusion rate of substances in the reaction system. During the preparation of sodium ferrate, sodium hypochlorite can contact and mix with the iron source more quickly, shortening the time of mass transfer and improving the overall efficiency of the reaction. Ultrasonic waves can also make various substances in the reaction system mix more evenly, avoiding the situation of too high or too low local concentration. In the traditional preparation method, incomplete reaction or low product purity may occur due to uneven mixing, while ultrasonic assistance can effectively solve this problem and provide a more uniform environment for the reaction. As can be seen from Table 2, after ultrasonic assistance, the concentration of synthesized sodium ferrate reaches a good effect, and the concentration of synthesized sodium ferrate is not less than 12 mmol / L, which is beneficial to improving the yield and quality of sodium ferrate. Therefore, the ultrasonic - assisted method proposed in the embodiments of the present invention has good application value and prospects in the field of preparing sodium ferrate.

[0200] Obviously, the above - described embodiments of the present invention are merely examples for clearly explaining the present invention, and are not limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. An ultrasonic-assisted red mud preparation of sodium ferrate equipment, characterized in that: It comprises a reaction kettle (1), a heating plate (8), a vibration plate (9), a red mud alkali leaching residue slurry storage tank (15), a sodium hypochlorite storage tank (21), a temperature measuring element and a stirrer device (12), The reactor (1) is provided with a red mud alkali leaching residue slurry feed port (5), a sodium hypochlorite feed port (6) and a discharge port (7); the heating plate (8) and the vibration plate (9) are sequentially arranged at the bottom of the reactor (1), and the heating plate (8) is in contact with the bottom of the reactor (1); the bottom of the vibration plate (9) is provided with an ultrasonic vibrator (10); The temperature measuring element is arranged on the reaction kettle (1) via a connecting piece, and the temperature measuring probe of the temperature measuring element (3) extends into the reaction kettle (1); The stirrer device (12) is arranged above the reaction kettle (1) via a fixed bracket (23), and the stirring rod (2) of the stirrer device (12) extends into the reaction kettle (1); The red mud alkali leaching residue slurry storage tank (15) is connected to the red mud alkali leaching residue slurry feed port (5); the sodium hypochlorite storage tank (21) is connected to the sodium hypochlorite feed port (6).

2. The ultrasonic-assisted red mud preparation of sodium ferrate according to claim 1, characterized in that: It also comprises a fixed base (11), wherein the fixed base (11) is provided with a fixed frame (20), and the vibration plate (9) and the heating plate (8) are fixedly arranged on the fixed frame (20) in sequence.

3. The ultrasonic-assisted red mud preparation of sodium ferrate according to claim 2, characterized in that: It also includes a slurry pump (4), the reactor (1) is an annular structure, and the reactor (1) is a closed space surrounded by a top wall, a side wall and a bottom wall; the slurry pump (4) is installed inside the reactor (1), the feed end and the discharge end of the slurry pump (4) are in opposite directions, and when the slurry pump (4) is in operation, it can drive the solution in the reactor (1) to circulate in the annular structure of the reactor (1); the number of the heating plates (8) and the vibration plates (9) is greater than or equal to 1, and the temperature measuring element (3) is a thermocouple or a thermal resistor.

4. The ultrasonic-assisted red mud preparation of sodium ferrate according to claim 3, characterized in that: The agitator device (12) is fixedly arranged on a fixed bracket (23) via a connecting piece (22); a plurality of ultrasonic vibrators (10) are arranged; the slurry pump (4) is a pneumatic slurry pump, and the pneumatic slurry pump is connected to an external air source via a vent pipe (25); the discharge port (7) is connected to a discharge pipe, and a valve is arranged on the discharge pipe, and the discharge pipe and the slurry pump (4) are both made of stainless steel.

5. The ultrasonic-assisted red mud preparation of sodium ferrate according to claim 1 or 2, characterized in that: It also includes a peristaltic pump (14) and a feed pipe (16); the red mud alkali leaching residue slurry storage tank (15) is connected to the red mud alkali leaching residue slurry feed port (5) through the feed pipe (16); and the feed pipe (16) is provided with a peristaltic pump (14) and a flow meter (13); The sodium hypochlorite storage tank (21) is connected to the sodium hypochlorite feed port (6) via a feed pipe (16), and the feed pipe (16) is provided with a peristaltic pump (14) and a flow meter (13).

6. The ultrasonic-assisted red mud preparation of sodium ferrate according to claim 3, characterized in that: The stirrer device (12) is electrically connected to a power source a (18), and the ultrasonic vibrator (10) is electrically connected to a power source line b (19).

7. A method for preparing sodium ferrate using the apparatus according to claim 1, characterized in that: The following steps are involved: Step 1: Place the high iron red mud alkali leaching residue in a vacuum drying oven and dry it. After drying, take it out and grind it into powder with a size controlled at 200-250 meshes; Step 2: Evenly mix the sodium hydroxide solution and the high-iron red mud alkali leaching residue to form a slurry, and inject it into the red mud alkali leaching residue slurry storage tank (15); Step 3: the slurry obtained in step 2 is transferred through a peristaltic pump (14) and then enters the ultrasonic circulation assisted heating reactor (1) from the red mud alkali leaching residue slurry feed port (5) to react with the sodium hypochlorite solution injected from the sodium hypochlorite feed port (6) on the other side to prepare sodium ferrate; Step 4: Place the sodium ferrate solution obtained in step 3 into a centrifuge and centrifuge for 3 to 5 times; Step 5: Through step 4, a pure sodium ferrate solution can be obtained.

8. The method according to claim 7, characterized in that: In step 2, the concentration of the sodium hydroxide solution used is 8-18 mol / L; in step 3, the concentration of sodium hypochlorite is 1.13-1.41 mol / L, the solid-liquid ratio of the high-iron red mud alkali leaching residue to the two reagents is 1:20-1:70 kg / L, and under the action of ultrasound, hydroxyl radicals are generated in the mixed solution of the reaction kettle (1).

9. The method according to claim 8, characterized in that: In step 3, the feed flow rate of the high iron red mud alkali leaching slag slurry is 0.15-0.3m 3 / h, the sodium hypochlorite feed flow rate is 0.2~0.3m 3 / h; after the red mud alkali leaching residue slurry and the sodium hypochlorite solution are fed, the heating plate (8) is started to heat to 55-75°C, and then the stirrer device (12), the slurry pump (4) and the ultrasonic vibrator (10) are turned on to make the mixed solution flow, and ultrasonic vibration and stirring are performed; the ultrasonic power of the ultrasonic vibrator (10) is 480-600W, the rotation speed of the stirring device (12) is 300-400rpm, wherein the ultrasonic vibration and stirring time are both 10-35min, after the reaction is completed, the valve switch of the discharge pipe is opened to allow the product to flow out through the discharge pipe, and the flow rate of the slurry pump (4) is 0.25-0.3m 3 / h.

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