A method for preparing a catalyst by using red mud and acidolysis waste residue of titanium dioxide, and its product and application

Abstract

The present invention discloses a method for preparing a catalyst by using red mud and titanium dioxide acidolysis waste residue, and its product and application. The method includes the following steps: calcining the red mud, adding the titanium dioxide acidolysis waste residue and an auxiliary agent, stirring evenly, adding desulfurization waste liquid, stirring evenly, performing hydrothermal reaction, solid-liquid separation, and calcining to obtain the catalyst material. The preparation process of the present invention is simple, and the high-efficient resource utilization of red mud and titanium dioxide acidolysis waste residue can be realized. The catalyst prepared by the hydrothermal reaction and the secondary calcination process can efficiently remove COD, ammonia nitrogen, total phosphorus and heavy metal pollutants in the waste liquid through the photocatalytic function.

Description

Technical Field

[0001] The present invention relates to a method for preparing a catalyst by using red mud and acidolysis waste residue of titanium dioxide, and its product and application, belonging to the field of resource utilization of solid waste. Background Art

[0002] In the production process of alumina, red mud is the main solid waste. The acidolysis waste residue generated in the production process of titanium dioxide also faces similar treatment problems. It contains various valuable metal ions and harmful substances, and if directly discharged, it will cause environmental pollution. Traditional treatment methods are often costly and difficult to effectively recycle resources.

[0003] At present, the preparation of many catalysts relies on limited natural resources, such as some precious metals or rare metals, which not only increases the production cost of the catalyst but also limits its large-scale application. In addition, the preparation process of some catalysts is complex, requiring multiple-step reactions and complex process conditions, consuming a large amount of energy, having low production efficiency, and may generate new waste, causing secondary pollution to the environment.

[0004] Red mud is rich in various metal oxides, such as iron oxide, aluminum oxide, calcium oxide, titanium oxide, etc. These components have potential catalytic activity or excellent properties as catalyst carriers. For example, iron oxide is an environmentally friendly, low-cost and highly active catalyst active component; aluminum oxide has advantages such as high melting point and large specific surface area, and can be used as a carrier material for catalysts. The acidolysis waste residue of titanium dioxide contains valuable metal elements such as titanium. Through appropriate treatment and recycling, it can be converted into substances with catalytic activity, thereby fully exerting its potential value and turning waste into treasure. Therefore, developing a method for preparing a catalyst by using red mud and acidolysis waste residue of titanium dioxide can not only solve the pollution problems of these two industrial waste residues, realize the resource utilization of waste, reduce the production cost of the catalyst, but also promote the sustainable development of related industrial fields, with significant environmental and economic benefits. Summary of the Invention

[0005] Object of the Invention: The technical problem to be solved by the present invention is to provide a method for preparing a catalyst by using red mud and acidolysis waste residue of titanium dioxide, and its product and application.

[0006] Technical Solution: To solve the above technical problem, the present invention provides a method for preparing a catalyst by using red mud and acidolysis waste residue of titanium dioxide, comprising the following steps:

[0007] (1) Calcining the red mud to obtain calcined red mud;

[0008] (2) Mixing the acidolysis waste residue of titanium dioxide, an auxiliary agent, and the calcined red mud, and stirring evenly to obtain a titanium-loaded red mud mixture;

[0009] (3) Mix the desulfurized waste liquid and the titanium-loaded red mud mixture, stir evenly, conduct hydrothermal reaction, solid-liquid separation, and calcination to obtain the catalyst material.

[0010] Among them, in step (1), the calcination temperature is 650-950 °C, and the calcination time is 0.5-5.5 hours.

[0011] Among them, in step (2), the mass ratio of the titanium dioxide acidolysis waste residue, the auxiliary agent, and the calcined red mud is 2.5-12.5:0.5-5.5:100.

[0012] Among them, in step (2), the auxiliary agent is tetramethylammonium fluoride, tetrabutylammonium hydroxide, or cyclohexylimine.

[0013] Among them, in step (3), the liquid-solid ratio of the desulfurized waste liquid and the titanium-loaded red mud mixture is 2-4:1 mL / g.

[0014] Among them, in step (3), the temperature of the hydrothermal reaction is 180-360 °C, and the hydrothermal reaction time is 1-4 hours.

[0015] Among them, in step (3), the calcination temperature is 550-850 °C, and the calcination time is 0.5-4.5 hours.

[0016] The present invention also provides a catalyst prepared by the above method.

[0017] The present invention also provides the application of the catalyst in removing pollutants.

[0018] Among them, the pollutants include one or more of COD, total phosphorus, ammonia nitrogen, or mercury ions.

[0019] The present invention also provides the application of the catalyst in purifying landfill leachate.

[0020] Reaction mechanism: When red mud is calcined in a high-temperature environment, the moisture, organic matter, and some volatile impurities in the red mud can be quickly removed. At the same time, the high-temperature calcination promotes the decomposition of aluminum hydroxide in the red mud into alumina, and some hydrated salt substances will also dehydrate to transform into anhydrous salts. At the same time, some carbonates will decompose into oxides and gases such as carbon dioxide and are discharged, thereby increasing the specific surface area and activity of the red mud and creating favorable conditions for subsequent reactions. The titanium dioxide acidolysis waste residue contains a certain amount of valuable metal elements such as titanium. It is mixed with the calcined red mud and auxiliary agents. The auxiliary agents can promote the transfer of ions or molecules between different phases, accelerate the subsequent reaction, and can undergo a coordination reaction with metal ions under certain conditions to form complexes, changing the chemical properties and existence states of metal ions. After mixing, it is stirred evenly to ensure full contact between each component, providing a uniform solid-phase mixture for subsequent reactions, that is, the titanium-loaded red mud mixture, which is conducive to the interaction and reaction between various substances. The desulfurization waste liquid is mixed and stirred with the titanium-loaded red mud mixture, so that the ions in the desulfurization waste liquid react with the substances in the titanium-loaded red mud mixture to undergo a series of chemical reactions. Sulfite ions will undergo oxidation-reduction reactions with metal ions in the red mud, reducing the metal ions to a lower valence state, or interact with components such as titanium in the titanium dioxide acidolysis waste residue to form new compounds or complexes; at the same time, neutralization reactions, precipitation reactions, etc. will also occur during the mixing process, further changing the chemical composition and material form in the mixing system. The reduced mixture is placed in a hydrothermal reaction kettle, and under high-temperature and high-pressure hydrothermal conditions, the substances in the system will undergo complex chemical reactions. During the hydrothermal reaction process, the recombination and coordination of metal elements such as titanium, aluminum, and iron with sulfur elements and other substances are involved to form compounds or complexes with specific structures and properties. Titanium and sulfur will form substances such as titanium sulfide, or form complex composite oxides or sulfides with elements such as aluminum and iron in the red mud. These reactions help to improve the activity and stability of the catalyst material, and at the same time are conducive to fixing various valuable metal elements in the catalyst material to prevent their loss. After the hydrothermal reaction, part of the substances in the system exist in solid form, which is the primary reaction mud, and the other part is dissolved in the reaction solution. The primary reaction mud is calcined at a high temperature to further remove the possible remaining moisture, volatile impurities, and organic matter, etc., and at the same time, the solid substances undergo processes such as sintering and crystal form transformation, thereby forming a catalyst material with a stable structure and good catalytic performance. During the calcination process, the active components in the solid mud will be further oxidized, reduced (molten heat), or undergo other chemical reactions to form the final catalyst active phase and carrier structure. The composite metal oxide will decompose and recrystallize at high temperature to form a structure with higher activity, thereby improving the catalytic activity and stability of the catalyst.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: The preparation process of the present invention is simple, and the efficient resource utilization of red mud and titanium white acid hydrolysis waste residue can be realized. The catalyst prepared by the hydrothermal reaction and the secondary calcination process can efficiently remove COD, ammonia nitrogen, total phosphorus and heavy metal pollutants in the waste liquid through the photocatalytic function. Brief Description of the Drawings

[0022] Figure 1 It is a flow chart of the treatment method of the present invention. Detailed Embodiments

[0023] The technical solution of the present invention will be further described below with reference to the drawings.

[0024] Preparation of landfill leachate and mercury-containing landfill leachate: The landfill leachate used in the experiment was taken from Zhuji Sanfeng Environmental Energy Co., Ltd. The COD mass concentration of this batch of landfill leachate was 4152 mg / L, the total phosphorus concentration was 305 mg / L, and the ammonia nitrogen concentration was 1075 mg / L. 500 mg of mercury was added to 1 L of landfill leachate and stirred evenly to prepare the mercury-containing landfill leachate.

[0025] Red mud: Provided by Shandong Zibo Zhengheng Aluminum Co., Ltd., the main detected components include: 38.52% Fe2O3, 27.83% Al2O3, 12.49% SiO2, 11.36% Na2O, 5.61% TiO2, 0.57% CaO, 0.34% SO3 and other components (inevitable impurities and loss on ignition);

[0026] Titanium white acid hydrolysis waste residue: Provided by Shandong Dongjia Group Co., Ltd., the main detected components include: 8.96% Fe2O3, 7.14% Al2O3, 5.82% SiO2, 3.56% CaO, 2.75% Na2O, 29.67% TiO2, 8.81% SO3 and other components (inevitable impurities and loss on ignition);

[0027] Desulfurization waste liquid: Provided by Fujian Longking Co., Ltd., the components include 44.56% ammonium sulfate, 12.75% ammonium thiosulfate, 23.84% ammonium sulfite, 2.42% metal sulfide and other components (inevitable impurities and loss on ignition).

[0028] Example 1 Influence of the mass ratio of titanium white acid hydrolysis waste residue, auxiliary agent and calcined red mud on the performance of the prepared catalyst material

[0029] The red mud is calcined to obtain calcined red mud, where the calcination temperature is 650 °C and the calcination time is 0.5 hour. The titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud are mixed according to the mass ratios of 1:0.5:100, 1.5:0.5:100, 2:0.5:100, 2.5:0.2:100, 2.5:0.3:100, 2.5:0.4:100, 2.5:0.5:100, 7.5:0.5:100, 12.5:0.5:100, 2.5:3:100, 7.5:3:100, 12.5:3:100, 2.5:5.5:100, 7.5:5.5:100, 12.5:5.5:100, 12.5:6:100, 12.5:6.5:100, 12.5:7:100, 15:5.5:100, 17.5:5.5:100, 20:5.5:100, and stirred evenly to obtain a titanium-loaded red mud mixture, where the auxiliary agent is tetraethylammonium fluoride. The desulfurization waste liquid and the titanium-loaded red mud mixture are mixed according to a liquid-solid ratio of 2:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture is placed in a hydrothermal reaction kettle for hydrothermal reaction. After the hydrothermal reaction is completed, solid-liquid separation is performed to obtain the primary reaction mud, where the hydrothermal temperature is 180 °C and the hydrothermal time is 1 hour. The primary reaction mud is calcined, and after the calcination is completed, a catalyst material is obtained, where the calcination temperature is 550 °C and the calcination time is 0.5 hour.

[0030] Photocatalytic removal test: 1 g of the catalyst is put into 1 L of mercury-containing landfill leachate, stirred at a speed of 120 rmp while irradiated with an ultraviolet lamp for 120 min, and then centrifuged at a speed of 5000 rpm for solid-liquid separation. The concentrations of different pollutants in the separated liquid are detected and the removal rates are calculated. The specific detection and calculation are as follows:

[0031] COD concentration detection and calculation of COD removal capacity: The chemical oxygen demand COD concentration of the leachate is determined according to the national standard "Water Quality - Determination of Chemical Oxygen Demand - Dichromate Method" (HJ828-2017). The COD removal capacity is calculated according to formula (1), where R COD is the COD removal capacity (mg / g), c COD0 and c CODt are the COD concentrations (mg / L) of the domestic waste landfill leachate before and after treatment, respectively, m is the mass of the catalyst (1 g), and V is the volume of the landfill leachate (1 L).

[0032]

[0033] Total phosphorus concentration detection and total phosphorus removal capacity calculation: The total phosphorus concentration of the leachate was determined in accordance with the standard "Water Quality - Determination of Phosphate and Total Phosphorus - Continuous Flow - Ammonium Molybdate Spectrophotometry" (HJ 670-2013). The total phosphorus removal rate was calculated according to formula (2), where R TP is the total phosphorus removal capacity (mg / g), c TP0 and c TPt are the total phosphorus concentrations (mg / L) of the domestic waste leachate before and after treatment, respectively, m is the mass of the catalyst (1 g), and V is the volume of the waste leachate (1 L).

[0034]

[0035] Ammonia nitrogen concentration detection and ammonia nitrogen removal capacity calculation: The concentration of ammonia nitrogen in the leachate was determined in accordance with "Water Quality - Determination of Ammonia Nitrogen - Salicylic Acid Spectrophotometry" (HJ536-2009). The ammonia nitrogen removal capacity was calculated according to formula (3), where R N is the ammonia nitrogen removal capacity (mg / g), c N0 is the initial concentration of ammonia nitrogen in the leachate before treatment (mg / L), c Nt is the remaining concentration of ammonia nitrogen in the treated leachate (mg / L), m is the mass of the catalyst (1 g), and V is the volume of the waste leachate (1 L).

[0036]

[0037] Mercury ion concentration detection and removal capacity calculation: The mercury ion concentration in the leachate was determined in accordance with "Water Quality - Determination of Mercury, Arsenic, Selenium, Bismuth and Antimony - Atomic Fluorescence Spectrometry" (HJ 694-2014). The mercury ion removal capacity was calculated according to formula (4), where R Hg is the mercury ion removal capacity (mg / g), c Hg0 is the initial concentration of mercury ions in the leachate before treatment (mg / L), c Hgt is the mercury ion concentration in the treated leachate (mg / L), m is the mass of the catalyst (1 g), and V is the volume of the waste leachate (1 L).

[0038]

[0039] The test results of this example are shown in Table 1.

[0040] Table 1 Influence of the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud on the performance of the prepared catalyst material

[0041]

[0042] As can be seen from Table 1, when the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is less than 2.5:0.5:100 (as in Table 1, the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud = 2.5:0.4:100, 2.5:0.3:100, 2.5:0.2:100, 2:0.5:100, 1.5:0.5:100, 1:0.5:100 and lower ratios not listed in Table 1), the addition of titanium dioxide acidolysis waste residue and auxiliary agent is less, and the reaction of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is insufficient, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst as the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud decreases. When the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is equal to 2.5~12.5:0.5~5.5:100 (as in Table 1, the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud = 2.5:0.5:100, 7.5:0.5:100, 12.5:0.5:100, 2.5:3:100, 7.5:3:100, 12.5:3:100, 2.5:5.5:100, 7.5:5.5:100, 12.5:5.5:100), when the red mud is calcined in a high-temperature environment, the moisture, organic matter, and some volatile impurities in the red mud can be quickly removed. At the same time, the high-temperature calcination promotes the decomposition of aluminum hydroxide in the red mud into alumina, and some hydrated salt substances will also dehydrate to transform into anhydrous salts. At the same time, some carbonates will decompose into oxides and carbon dioxide and other gases and are discharged, thereby increasing the specific surface area and activity of the red mud and creating favorable conditions for subsequent reactions. The titanium dioxide acidolysis waste residue contains a certain amount of valuable metal elements such as titanium. When it is mixed with the calcined red mud and the auxiliary agent, the auxiliary agent can promote the transfer of ions or molecules between different phases, accelerate the progress of subsequent reactions, and it can undergo a coordination reaction with metal ions under certain conditions to form complexes, changing the chemical properties and existence states of metal ions. After mixing and stirring evenly, the components are in full contact with each other, providing a uniform solid-phase mixture for subsequent reactions, that is, titanium-loaded red mud mixture, which is conducive to the interaction and reaction between various substances. Finally, the prepared catalyst has a COD removal capacity higher than 2875 mg / g, a total phosphorus removal capacity higher than 189 mg / g, an ammonia nitrogen removal capacity higher than 632 mg / g, and a mercury removal capacity higher than 215 mg / g.When the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is greater than 12.5:5.5:100 (as shown in Table 1, when the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud = 12.5:6:100, 12.5:6.5:100, 12.5:7:100, 15:5.5:100, 17.5:5.5:100, 20:5.5:100 and higher ratios not listed in Table 1), the addition of titanium dioxide acidolysis waste residue and auxiliary agent is excessive, and the reaction of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is unbalanced, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst with the further increase of the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud. Generally speaking, considering the benefits and costs, when the mass ratio of titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is equal to 2.5 - 12.5:0.5 - 5.5:100, it is most beneficial to improve the catalytic performance of the prepared bismuth ferrite composite catalytic material.

[0043] Effect of the liquid - solid ratio of the mixture of desulfurization waste liquid and titanium - loaded red mud on the performance of the prepared catalyst material in Example 2

[0044] The red mud was calcined to obtain calcined red mud, where the calcination temperature was 800 °C and the calcination time was 3 hours. The titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud were mixed at a mass ratio of 12.5:5.5:100 and stirred evenly to obtain a titanium - loaded red mud mixture, where the auxiliary agent was tetrabutylammonium hydroxide. The desulfurization waste liquid and the titanium - loaded red mud mixture were mixed at a liquid - solid ratio of 0.5:1 mL / g, 1:1 mL / g, 1.5:1 mL / g, 2:1 mL / g, 3:1 mL / g, 4:1 mL / g, 4.5:1 mL / g, 5:1 mL / g, 5.5:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture was placed in a hydrothermal reaction kettle for hydrothermal reaction. After the hydrothermal reaction, solid - liquid separation was carried out to obtain the primary reaction mud, where the hydrothermal temperature was 270 °C and the hydrothermal time was 2.5 hours. The primary reaction mud was calcined, and after the calcination, a catalyst material was obtained, where the calcination temperature was 700 °C and the calcination time was 2.5 hours.

[0045] The photocatalytic removal test, COD concentration detection and COD removal capacity calculation, total phosphorus concentration detection and total phosphorus removal capacity calculation, ammonia nitrogen concentration detection and ammonia nitrogen removal capacity calculation, and mercury ion concentration detection and removal capacity calculation were all the same as in Example 1. The test results of this example are shown in Table 2.

[0046] Table 2 Effect of the liquid - solid ratio of the mixture of desulfurization waste liquid and titanium - loaded red mud on the performance of the prepared catalyst material

[0047]

[0048] As can be seen from Table 2, when the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud is less than 2:1 mL / g (as in Table 2, when the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud = 1.5:1 mL / g, 1:1 mL / g, 0.5:1 mL / g and lower ratios not listed in Table 2), less desulfurized waste liquid is added, and the reaction between the desulfurized waste liquid and the mixture of titanium-loaded red mud is insufficient, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst as the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud decreases. When the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud is equal to 2 - 4:1 mL / g (as in Table 2, when the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud = 2:1 mL / g, 3:1 mL / g, 4:1 mL / g), the desulfurized waste liquid is mixed and stirred with the mixture of titanium-loaded red mud, causing a series of chemical reactions between the ions in the desulfurized waste liquid and the substances in the mixture of titanium-loaded red mud. Sulfite ions will undergo redox reactions with metal ions in the red mud, reducing the metal ions to lower valence states, or interact with components such as titanium in the titanium dioxide acidolysis waste residue to form new compounds or complexes; at the same time, neutralization reactions, precipitation reactions, etc. will also occur during the mixing process, further changing the chemical composition and physical form of the mixed system. Finally, the prepared catalyst has a COD removal capacity higher than 3122 mg / g, a total phosphorus removal capacity higher than 214 mg / g, an ammonia nitrogen removal capacity higher than 676 mg / g, and a mercury removal capacity higher than 232 mg / g. When the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud is greater than 4:1 mL / g (as in Table 2, when the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud = 4.5:1 mL / g, 5:1 mL / g, 5.5:1 mL / g and higher ratios not listed in Table 2), the desulfurized waste liquid is added in excess, and the reaction between the desulfurized waste liquid and the mixture of titanium-loaded red mud is unbalanced, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst as the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud further increases. Generally speaking, considering the benefits and costs, when the liquid-solid ratio of the mixture of desulfurized waste liquid and titanium-loaded red mud is equal to 2 - 4:1 mL / g, it is most beneficial to improve the catalytic performance of the prepared bismuth ferrite composite catalytic material.

[0049] Effect of hydrothermal time on the performance of the prepared catalyst material in Example 3

[0050] The red mud is calcined to obtain calcined red mud, where the calcination temperature is 950 °C and the calcination time is 5.5 hours. The titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud are mixed according to a mass ratio of 12.5:5.5:100, and stirred evenly to obtain a titanium-loaded red mud mixture, where the auxiliary agent is cyclohexylamine. The desulfurization waste liquid and the titanium-loaded red mud mixture are mixed according to a liquid-solid ratio of 4:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture is placed in a hydrothermal reaction kettle for hydrothermal reaction. After the hydrothermal reaction is completed, solid-liquid separation is carried out to obtain the primary reaction mud, where the hydrothermal temperature is 360 °C and the hydrothermal time is 0.5 hour, 0.6 hour, 0.8 hour, 1 hour, 2.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours. The primary reaction mud is calcined, and after the calcination is completed, a catalyst material is obtained, where the calcination temperature is 850 °C and the calcination time is 4.5 hours.

[0051] The photocatalytic removal test, the detection of COD concentration and the calculation of COD removal capacity, the detection of total phosphorus concentration and the calculation of total phosphorus removal capacity, the detection of ammonia nitrogen concentration and the calculation of ammonia nitrogen removal capacity, and the detection of mercury ion concentration and the calculation of removal capacity are the same as those in Example 1. The test results of this example are shown in Table 3.

[0052] Table 3 Influence of hydrothermal time on the performance of the prepared catalyst material

[0053]

[0054] As can be seen from Table 3, when the hydrothermal time is less than 1 hour (such as in Table 3, the hydrothermal time = 0.8 hour, 0.6 hour, 0.5 hour and lower values not listed in Table 3), the hydrothermal time is short, and the reaction between the components of the reduction mixture is insufficient, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst with the decrease of the hydrothermal time. When the hydrothermal time is equal to 1 - 4 hours (such as in Table 3, the hydrothermal time = 1 hour, 2.5 hours, 4 hours), the reduction mixture is placed in a hydrothermal reactor, and under high-temperature and high-pressure hydrothermal conditions, complex chemical reactions will occur in the system. During the hydrothermal reaction process, the recombination and coordination of metal elements such as titanium, aluminum, and iron with sulfur elements and other substances will occur to form compounds or complexes with specific structures and properties. Titanium and sulfur will form substances such as titanium sulfide, or form complex composite oxides or sulfides with elements such as aluminum and iron in the red mud. These reactions help to improve the activity and stability of the catalyst material, and at the same time, it is beneficial to fix various valuable metal elements in the catalyst material to prevent their loss. After the hydrothermal reaction, part of the substances in the system exist in solid form, which is the primary reaction mud, and the other part is dissolved in the reaction solution. Finally, the prepared catalyst has a COD removal capacity higher than 3260 mg / g, a total phosphorus removal capacity higher than 227 mg / g, an ammonia nitrogen removal capacity higher than 707 mg / g, and a mercury removal capacity higher than 249 mg / g. When the hydrothermal time is greater than 4 hours (such as in Table 3, the hydrothermal time = 4.5 hours, 5 hours, 5.5 hours and higher values not listed in Table 3), the desulfurization waste liquid is added in excess, and the reaction between the desulfurization waste liquid and the titanium-loaded red mud mixture is unbalanced, resulting in a significant decrease in the COD, total phosphorus, ammonia nitrogen, and mercury removal capacities of the prepared catalyst with the further increase of the hydrothermal time. Generally speaking, considering the benefits and costs, when the hydrothermal time is equal to 1 - 4 hours, it is most beneficial to improve the catalytic performance of the prepared bismuth ferrite composite catalyst material.

[0055] Example 4 Influence of Different Comparative Processes on the Performance of the Prepared Catalyst Material

[0056] The process of the present invention: The red mud is calcined to obtain calcined red mud, where the calcination temperature is 950 °C and the calcination time is 5.5 hours. The titanium white acidolysis waste residue, auxiliary agent, and calcined red mud are mixed in a mass ratio of 12.5:5.5:100 and stirred evenly to obtain a titanium-loaded red mud mixture, where the auxiliary agent is ammonium fluoride. The desulfurization waste liquid and the titanium-loaded red mud mixture are mixed in a liquid-solid ratio of 4:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture is placed in a hydrothermal reactor for hydrothermal reaction. After the hydrothermal reaction is completed, solid-liquid separation is carried out to obtain the primary reaction mud, where the hydrothermal temperature is 360 °C and the hydrothermal time is 2.5 hours. The primary reaction mud is calcined, and after the calcination is completed, a catalyst material is obtained, where the calcination temperature is 850 °C and the calcination time is 2.5 hours.

[0057] Comparative Process 1: The red mud is calcined to obtain calcined red mud, where the calcination temperature is 950 °C and the calcination time is 5.5 hours. The auxiliary agent and the calcined red mud are mixed at a mass ratio of 5.5:100 and stirred evenly to obtain an auxiliary red mud mixture, where the auxiliary agent is ammonium fluoride. The desulfurization waste liquid and the auxiliary red mud mixture are mixed at a liquid-solid ratio of 4:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture is placed in a hydrothermal reaction kettle for hydrothermal reaction. After the hydrothermal reaction is completed, solid-liquid separation is carried out to obtain the primary reaction mud, where the hydrothermal temperature is 360 °C and the hydrothermal time is 2.5 hours. The primary reaction mud is calcined, and after the calcination is completed, a catalyst material is obtained, where the calcination temperature is 850 °C and the calcination time is 2.5 hours.

[0058] Comparative Process 2: The red mud is calcined to obtain calcined red mud, where the calcination temperature is 950 °C and the calcination time is 5.5 hours. The titanium dioxide acidolysis waste residue, the auxiliary agent, and the calcined red mud are mixed at a mass ratio of 12.5:5.5:100 and stirred evenly to obtain a titanium-loaded red mud mixture, where the auxiliary agent is ammonium fluoride. The desulfurization waste liquid and the titanium-loaded red mud mixture are mixed at a liquid-solid ratio of 4:1 mL / g and stirred evenly to obtain a reduction mixture. The reduction mixture is calcined, and after the calcination is completed, a catalyst material is obtained, where the calcination temperature is 850 °C and the calcination time is 2.5 hours.

[0059] The photocatalytic removal test, the detection of COD concentration and the calculation of COD removal capacity, the detection of total phosphorus concentration and the calculation of total phosphorus removal capacity, the detection of ammonia nitrogen concentration and the calculation of ammonia nitrogen removal capacity, and the detection of mercury ion concentration and the calculation of removal capacity are the same as those in Example 1. The test results of this example are shown in Table 4.

[0060] Table 4 Influence of Different Comparative Processes on the Performance of the Prepared Catalyst Material

[0061]

[0062] As can be seen from Table 4, the COD removal capacity, total phosphorus removal capacity, ammonia nitrogen removal capacity, and mercury ion removal capacity achieved by the catalyst material prepared by the process of the present invention are significantly higher than those of Comparative Process 1 and Comparative Process 2.

Claims

1. A method for preparing a catalyst from red mud and acidolysis waste residue of titanium dioxide, characterized in that, It includes the following steps: (1) Calcining the red mud to obtain calcined red mud; the temperature of the calcination is 650 - 950 °C; (2) Mixing the titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud, and stirring evenly to obtain a titanium-loaded red mud mixture; the auxiliary agent is tetramethylammonium fluoride, tetrabutylammonium hydroxide, or cyclohexylimine; the mass ratio of the titanium dioxide acidolysis waste residue, auxiliary agent, and calcined red mud is 2.5 - 12.5:0.5 - 5.5:100; (3) Mixing the desulfurization waste liquid and the titanium-loaded red mud mixture, stirring evenly, performing hydrothermal reaction, solid-liquid separation, and calcination to obtain the catalyst material; the temperature of the hydrothermal reaction is 180 - 360 °C, and the time of the hydrothermal reaction is 1 - 4 hours; the liquid-solid ratio of the desulfurization waste liquid and the titanium-loaded red mud mixture is 2 - 4:1 mL / g.

2. The method according to claim 1, characterized in that, In step (1), the time of the calcination is 0.5 - 5.5 hours.

3. The method according to claim 1, wherein In step (3), the temperature of the calcination is 550 - 850 °C, and the time of the calcination is 0.5 - 4.5 hours.

4. A catalyst prepared by the method according to any one of claims 1 - 3.

5. Use of the catalyst according to claim 4 in removing pollutants, characterized in that, The pollutants include one or more of COD, total phosphorus, ammonia nitrogen, or mercury ions.

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