A process for the preparation of zeolite molecular sieves for water treatment using red mud

Abstract

This invention discloses a process for preparing zeolite molecular sieves for water treatment using red mud, belonging to the field of zeolite molecular sieve preparation for water treatment; the preparation steps of this invention for preparing zeolite molecular sieves for water treatment using red mud include: (1) pretreatment of red mud; (2) mixing the red mud pretreated in step (1) with alkali melt slag, introducing alkali source and silicon source for mixing and aging; (3) subjecting the material aged in step (2) to primary hydrothermal treatment; (4) dispersing the material from the primary hydrothermal treatment in step (3) in manganese recovery liquid, then adding sodium chlorate solution for mixing, and performing secondary hydrothermal treatment to obtain zeolite molecular sieves; the alkali melt slag is obtained by calcining leaching residue with sodium hydroxide; the manganese recovery liquid is obtained by leaching liquid recovery treatment; the leaching residue and leaching liquid are obtained by acid leaching of electrolytic manganese slag; this invention uses electrolytic manganese slag and red mud to prepare zeolite molecular sieves with high adsorption efficiency for heavy metals and ammonia nitrogen in wastewater.

Description

Technical Field

[0001] This invention relates to the field of zeolite molecular sieve preparation for water treatment, specifically a process for preparing zeolite molecular sieves for water treatment using red mud. Background Technology

[0002] Red mud and electrolytic manganese slag are major solid wastes generated by the alumina and electrolytic manganese industries, respectively, with huge annual output and consistently low comprehensive utilization rates. Red mud is highly alkaline and contains large amounts of oxides such as iron, aluminum, silicon, and calcium; electrolytic manganese slag is rich in silicon, aluminum, and residual pollutants such as manganese and ammonia nitrogen. Direct stockpiling of these two types of waste not only occupies significant land resources, but the heavy metal ions and ammonia nitrogen they contain may also migrate into the soil and water bodies through leaching, posing a serious threat to the ecological environment and human health.

[0003] Zeolite molecular sieves are widely used in wastewater treatment due to their regular pore structure, large specific surface area, and excellent ion exchange performance. Traditional preparation of zeolite molecular sieves often relies on high-purity chemical reagents or natural minerals, resulting in high costs. In recent years, the preparation of zeolite molecular sieves using industrial solid waste as raw material has become a research hotspot. This approach not only achieves resource utilization of waste but also reduces the production cost of zeolite.

[0004] However, zeolite molecular sieves prepared from single solid wastes such as red mud or electrolytic manganese slag often suffer from problems such as low crystallinity, unsatisfactory pore structure, and limited adsorption capacity for wastewater pollutants such as heavy metals and ammonia nitrogen.

[0005] Therefore, there is an urgent need to develop a process that can synergistically utilize red mud and electrolytic manganese slag to prepare zeolite molecular sieves with high adsorption efficiency for heavy metals and ammonia nitrogen. Summary of the Invention

[0006] The purpose of this invention is to provide a process for preparing zeolite molecular sieves for water treatment using red mud, so as to solve the technical problems mentioned in the background art.

[0007] The technical solution to achieve the objective of this invention is: This invention provides a process for preparing zeolite molecular sieves for water treatment using red mud, the preparation steps of which include: (1) Pretreatment of red mud; (2) The red mud pretreated in step (1) is mixed with the alkali-melted slag, and an alkali source and a silicon source are introduced for mixing and aging; (3) Perform a hydrothermal treatment on the material aged in step (2); (4) Disperse the material from the first hydrothermal treatment in step (3) in the manganese recovery solution, then add sodium chlorate solution to mix, and perform a second hydrothermal treatment to obtain zeolite molecular sieve.

[0008] Further, step (1) is as follows: drying, grinding and sieving the red mud.

[0009] Further, step (2) is as follows: the alkali-melted slag and the red mud pretreated in step (1) are mixed at a mass ratio of (0.8~1):1, and then 4~6wt% sodium hydroxide solution and silicon source are added and stirred for 0.5~1h, and then aged at room temperature in a sealed manner for 1~24h; the molar ratio of silicon oxide to aluminum oxide in the material aged in step (2) is 1.5~5; the molar ratio of sodium oxide to aluminum oxide is 0.5~3.

[0010] Furthermore, the alkali-melted slag is obtained by calcining a mixture of leaching residue and sodium hydroxide; the manganese recovery solution is obtained by recycling and treating the leaching solution.

[0011] Further, the preparation steps of the leaching residue are as follows: electrolytic manganese slag and 10wt% sulfuric acid solution are mixed at a solid-liquid ratio of 1:(7~8), stirred at 90~95℃ for 3~4h, and then filtered to obtain leaching solution and filter residue. The filter residue is washed until neutral, dried, and ground to obtain leaching residue.

[0012] Further, the preparation steps of the manganese recovery solution are as follows: add 0.047~0.055 times the volume of the leachate to a 3wt% hydrogen peroxide solution, then add 5wt% calcium oxide solution to adjust the pH to 4.5~5, stir at room temperature for 30 min, filter and collect the filtrate, raise the temperature to 88~92℃, add 0.1~0.12 parts by weight of manganese fluoride from the leachate, stir for at least 2 h, filter and collect the filtrate, add 0.00023~0.00032 parts by weight of barium sulfide from the leachate at 55~65℃, stir for 50~60 min, filter and collect the filtrate to obtain the manganese recovery solution.

[0013] Furthermore, a template agent may be added in step (2), and the amount of template agent added is 3% of the total mass of alumina in the red mud and alkali molten slag.

[0014] Furthermore, in step (3), the hydrothermal temperature is 70~180℃ and the hydrothermal reaction time is 3~24h.

[0015] Further, step (4) is as follows: the material from the first hydrothermal treatment in step (3) is dispersed in the manganese recovery liquid by ultrasonic dispersion for 30-40 min, and then sodium chlorate solution is added. The ratio of sodium chlorate to manganese in the manganese recovery liquid is (0.4-0.48):1. The mixture is stirred and dispersed for 30-60 min, and then hydrothermally treated at 80-95℃ for 3-12 h.

[0016] Furthermore, the mass ratio of the material in the primary hydrothermal process to the mass of manganese in the manganese recovery solution is (2~4):0.632.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The process of preparing zeolite molecular sieves for water treatment using red mud of the present invention firstly acid-leaching electrolytic manganese slag to obtain leaching residue and leaching solution; then the leaching residue is mixed with sodium hydroxide and calcined to obtain alkali-fused slag; then the leaching solution is recovered to obtain manganese recovery solution; then the red mud is pretreated; next, the pretreated red mud is mixed with alkali-fused slag, and alkali source and silicon source are introduced for mixed aging; then the aged material is subjected to a first hydrothermal treatment; finally, the material from the first hydrothermal treatment is dispersed in the manganese recovery solution, and then sodium chlorate solution is added and mixed for a second hydrothermal treatment to obtain zeolite molecular sieves; thus realizing the reuse of two solid wastes, electrolytic manganese slag and red mud, and the zeolite molecular sieves obtained have high adsorption efficiency for heavy metals and ammonia nitrogen in wastewater.

[0018] (2) Because the electrolytic manganese slag contains a large number of impurities, which severely restricts the utilization rate of its effective components, it is necessary to release the amorphous silica and alumina in it through leaching treatment. Therefore, the electrolytic manganese slag was acid leached and successfully separated into leaching residue rich in silica and alumina and leaching solution containing manganese.

[0019] (3) In this invention, hydrogen peroxide solution is added to the leachate to oxidize ferrous iron to ferric iron, and then iron and aluminum impurities are effectively removed by neutralization precipitation. Then, manganese fluoride is added under heating conditions, and fluoride ions are released by utilizing its high solubility in water. The fluoride ions react with calcium and magnesium ions to form insoluble calcium fluoride and magnesium fluoride precipitates, thereby deeply removing calcium and magnesium ions. Then, barium sulfide is added under heating conditions, and the sulfur ions released react with copper and zinc ions to form CuS and ZnS precipitates, which are removed by filtration, thereby recovering and purifying manganese in the leachate.

[0020] (4) By introducing a template agent, the present invention regulates the pore structure and skeleton charge distribution of zeolite molecular sieve, thereby optimizing the microstructure and specific surface area of ​​the material and significantly improving the adsorption of pollutants in water by zeolite molecular sieve.

[0021] (5) In this invention, the material after the first hydrothermal treatment is uniformly dispersed in the manganese recovery liquid, and a second hydrothermal reaction is carried out after adding sodium chlorate solution to obtain zeolite molecular sieve; sodium chlorate is used as an oxidant to oxidize divalent manganese in situ, thereby introducing manganese dioxide into the zeolite molecular sieve framework. The introduction of manganese dioxide not only significantly increases the specific surface area of ​​the zeolite molecular sieve, but also endows the material with more abundant surface active sites. Thanks to electrostatic attraction, complexation, sieve effect of pore structure and excellent ion exchange characteristics of zeolite itself, the adsorption efficiency of zeolite molecular sieve for heavy metal ions and ammonia nitrogen in water is further improved. Attached Figure Description

[0022] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 The X-ray diffraction pattern of red mud, the raw material used in a specific embodiment of the present invention, is shown.

[0023] Figure 2 This is a scanning electron microscope image of a zeolite molecular sieve according to a specific embodiment of the present invention. Detailed Implementation

[0024] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0028] The composition of the electrolytic manganese slag of the present invention is as follows: silicon dioxide 38.47 wt%, aluminum oxide 11.87 wt%, sulfur trioxide 22.53 wt%, calcium oxide 14.87 wt%, ferric oxide 4.69 wt%, manganese oxide 3.31 wt%, potassium oxide 1.85 wt%, magnesium oxide 1.42 wt%, and other components 0.99 wt%.

[0029] Figure 1 The X-ray diffraction pattern of the red mud of this application is as follows: silicon dioxide 15.72 wt%, aluminum oxide 34.14 wt%, calcium oxide 1.03 wt%, ferric oxide 31.81 wt%, titanium oxide 5.44 wt%, sodium oxide 10.29 wt%, magnesium oxide 1.42 wt%, and other 0.15 wt%.

[0030] Example 1 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) Mix electrolytic manganese slag with 10wt% sulfuric acid solution at a solid-liquid ratio of 1:7, stir at 90℃ for 4h, then filter to obtain leachate and filter residue. Wash the filter residue until neutral, dry and grind to obtain leachate residue. (2) The leaching residue and sodium hydroxide were mixed at a mass ratio of 1:1.1, calcined at 750°C for 2.5 h, and ground to obtain alkali-fused slag; (3) Add 3wt% hydrogen peroxide solution (0.047 times the volume of the leachate) to the leachate, then add 5wt% calcium oxide solution to adjust the pH to 4.5. After stirring at room temperature for 30 min, filter and collect the filtrate. Heat to 88℃, add 0.1 parts by weight of manganese fluoride from the leachate, stir for 2 h, and then filter and collect the filtrate. Add 0.00023 parts by weight of barium sulfide from the leachate at 55℃, stir for 50 min, and then filter and collect the filtrate to obtain manganese recovery solution. (4) Dry, grind, and pass the red mud through a 200-mesh sieve to obtain pretreated red mud; (5) Mix the alkali-melted slag with the pretreated red mud at a mass ratio of 0.8:1, then add 4wt% sodium hydroxide solution, silicon source tetraethyl orthosilicate, and template agent tetrapropylammonium bromide and stir for 0.5h, then seal and age at room temperature for 1h; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material is 1.5; the molar ratio of sodium oxide to aluminum oxide is 0.5; the amount of template agent added is 3% of the total mass of aluminum oxide in the red mud and alkali-melted slag; (6) The material aged in step (5) was transferred into a high-pressure reactor and hydrothermally reacted at 70°C for 24 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, dried at 100°C overnight, ground, and passed through a 200-mesh sieve to obtain the material after one hydrothermal reaction. (7) The material of the first hydrothermal treatment was ultrasonically dispersed in the manganese recovery solution for 30 min, and then 30% sodium chlorate solution was added. The molar ratio of sodium chlorate to manganese in the manganese recovery solution was 0.4:1. The mixture was stirred and dispersed for 30 min, and then hydrothermally treated at 80℃ for 12 h. The mass ratio of the material of the first hydrothermal treatment to the manganese in the manganese recovery solution was 2:0.632. The mixture was filtered, washed with deionized water until the pH of the filtrate was less than 9.5, and dried at 100℃ overnight to obtain zeolite molecular sieve.

[0031] Example 2 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) Mix electrolytic manganese slag with 10wt% sulfuric acid solution at a solid-liquid ratio of 1:8, stir at 95℃ for 3.5h, then filter to obtain leachate and filter residue. Wash the filter residue until neutral, dry and grind to obtain leachate residue. (2) The leaching residue and sodium hydroxide were mixed at a mass ratio of 1:1.2, calcined at 800℃ for 2 hours, and ground to obtain alkali-fused slag; (3) Add 3wt% hydrogen peroxide solution (0.05 times the volume of the leachate) to the leachate, then add 5wt% calcium oxide solution to adjust the pH to 5. Stir at room temperature for 30 min, then filter and collect the filtrate. Heat to 90℃, add 0.12 parts by weight of manganese fluoride from the leachate, stir for 2 h, then filter and collect the filtrate. Add 0.0003 parts by weight of barium sulfide from the leachate at 60℃, stir for 60 min, then filter and collect the filtrate to obtain manganese recovery solution. (4) Dry, grind, and pass the red mud through a 200-mesh sieve to obtain pretreated red mud; (5) Mix the alkali-melted slag with the pretreated red mud at a mass ratio of 1:1, then add 5wt% sodium hydroxide solution, silicon source tetraethyl orthosilicate, and template agent tetrapropylammonium bromide and stir for 1 hour, then seal and age at room temperature for 1 hour; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material is 2; the molar ratio of sodium oxide to aluminum oxide is 1; the amount of template agent added is 3% of the total mass of aluminum oxide in the red mud and alkali-melted slag; (6) The material aged in step (5) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 8 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, dried at 100°C overnight, ground, and passed through a 200-mesh sieve to obtain the material after one hydrothermal reaction. (7) The material of the first hydrothermal treatment is dispersed in the manganese recovery solution by ultrasonic dispersion for 30 min, and then 30% sodium chlorate solution is added. The molar ratio of sodium chlorate to manganese in the manganese recovery solution is 0.48:1. The mixture is stirred and dispersed for 30~60 min, and then hydrothermally treated at 90℃ for 8 h. The mass ratio of the material of the first hydrothermal treatment to the manganese in the manganese recovery solution is 3:0.632. The mixture is filtered, washed with deionized water until the pH of the filtrate is less than 9.5, and dried at 100℃ overnight to obtain zeolite molecular sieve.

[0032] Example 3 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) Mix electrolytic manganese slag with 10wt% sulfuric acid solution at a solid-liquid ratio of 1:8, stir at 95℃ for 3h, then filter to obtain leachate and filter residue. Wash the filter residue until neutral, dry and grind to obtain leachate residue. (2) The leaching residue and sodium hydroxide were mixed at a mass ratio of 1:1.3, calcined at 850°C for 1.5 h, and ground to obtain alkali-fused slag; (3) Add 3wt% hydrogen peroxide solution (0.055 times the volume of the leachate) to the leachate, then add 5wt% calcium oxide solution to adjust the pH to 5. Stir at room temperature for 30 min, then filter and collect the filtrate. Heat to 92℃, add 0.12 parts by weight of manganese fluoride from the leachate, stir for 2 h, then filter and collect the filtrate. Add 0.00032 parts by weight of barium sulfide from the leachate at 65℃, stir for 50 min, then filter and collect the filtrate to obtain manganese recovery solution. (4) Dry, grind, and pass the red mud through a 200-mesh sieve to obtain pretreated red mud; (5) Mix the alkali-melted slag with the pretreated red mud at a mass ratio of 1:1, then add 6wt% sodium hydroxide solution, silicon source tetraethyl orthosilicate, and template agent tetrapropylammonium bromide and stir for 1 hour, then seal and age at room temperature for 24 hours; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material is 5; the molar ratio of sodium oxide to aluminum oxide is 3; the amount of template agent added is 3% of the total mass of aluminum oxide in the red mud and alkali-melted slag; (6) The material aged in step (5) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 24 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, dried at 100°C overnight, ground, and passed through a 200-mesh sieve to obtain the material after one hydrothermal reaction. (7) The material of the first hydrothermal treatment was ultrasonically dispersed in the manganese recovery solution for 40 min, and then 30% sodium chlorate solution was added. The molar ratio of sodium chlorate to manganese in the manganese recovery solution was 0.48:1. The mixture was stirred and dispersed for 60 min, and then hydrothermally treated at 95℃ for 3 h. The mass ratio of the material of the first hydrothermal treatment to the manganese in the manganese recovery solution was 4:0.632. The mixture was filtered, washed with deionized water until the pH of the filtrate was less than 9.5, and dried at 100℃ overnight to obtain zeolite molecular sieve.

[0033] Comparative Example 1 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) Mix electrolytic manganese slag with 10wt% sulfuric acid solution at a solid-liquid ratio of 1:8, stir at 95℃ for 3.5h, then filter, wash until neutral, dry, and grind to obtain leaching residue; (2) The leaching residue and sodium hydroxide were mixed at a mass ratio of 1:1.2, calcined at 800℃ for 2 hours, and ground to obtain alkali-fused slag; (3) Dry, grind and pass the red mud through a 200-mesh sieve to obtain pretreated red mud; (4) Mix the alkali-melted slag with the pretreated red mud at a mass ratio of 1:1, then add 5wt% sodium hydroxide solution, silicon source tetraethyl orthosilicate, and template agent tetrapropylammonium bromide and stir for 1 hour, then seal and age at room temperature for 1 hour; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material is 2; the molar ratio of sodium oxide to aluminum oxide is 1; the amount of template agent added is 3% of the total mass of aluminum oxide in the red mud and alkali-melted slag; (5) The material aged in step (4) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 8 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, and dried at 100°C overnight to obtain zeolite molecular sieve.

[0034] Comparative Example 2 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) Mix electrolytic manganese slag with 10wt% sulfuric acid solution at a solid-liquid ratio of 1:8, stir at 95℃ for 3.5h, then filter to obtain leachate and filter residue. Wash the filter residue until neutral, dry and grind to obtain leachate residue. (2) The leaching residue and sodium hydroxide were mixed at a mass ratio of 1:1.2, calcined at 800℃ for 2 hours, and ground to obtain alkali-fused slag; (3) Add 3wt% hydrogen peroxide solution (0.05 times the volume of the leachate) to the leachate, then add 5wt% calcium oxide solution to adjust the pH to 5. Stir at room temperature for 30 min, then filter and collect the filtrate. Heat to 90℃, add 0.12 parts by weight of manganese fluoride from the leachate, stir for 2 h, then filter and collect the filtrate. Add 0.0003 parts by weight of barium sulfide from the leachate at 60℃, stir for 60 min, then filter and collect the filtrate to obtain manganese recovery solution. (4) Dry, grind, and pass the red mud through a 200-mesh sieve to obtain pretreated red mud; (5) Mix the alkali-melted slag with the pretreated red mud at a mass ratio of 1:1, then add 5wt% sodium hydroxide solution and silicon source tetraethyl orthosilicate and stir for 1 hour, then seal and age at room temperature for 1 hour; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material is 2; the molar ratio of sodium oxide to aluminum oxide is 1; the amount of template agent added is 3% of the total mass of aluminum oxide in the red mud and alkali-melted slag; (6) The material aged in step (5) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 8 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, dried at 100°C overnight, ground, and passed through a 200-mesh sieve to obtain the material after one hydrothermal reaction. (7) The material of the first hydrothermal treatment is dispersed in the manganese recovery solution by ultrasonic dispersion for 30 min, and then 30% sodium chlorate solution is added. The molar ratio of sodium chlorate to manganese in the manganese recovery solution is 0.48:1. The mixture is stirred and dispersed for 30~60 min, and then hydrothermally treated at 90℃ for 8 h. The mass ratio of the material of the first hydrothermal treatment to the manganese in the manganese recovery solution is 3:0.632. The mixture is filtered, washed with deionized water until the pH of the filtrate is less than 9.5, and dried at 100℃ overnight to obtain zeolite molecular sieve.

[0035] Comparative Example 3 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) The red mud is dried, ground, and passed through a 200-mesh sieve to obtain pretreated red mud; (2) The pretreated red mud was stirred with 5wt% sodium hydroxide solution, silicon source tetraethyl orthosilicate, and template agent tetrapropylammonium bromide for 1 hour, and then aged at room temperature in a sealed container for 1 hour; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material was 2; the molar ratio of sodium oxide to aluminum oxide was 1; and the amount of template agent added was 3% of the total mass of aluminum oxide in the red mud; (3) The material aged in step (2) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 8 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, and dried at 100°C overnight to obtain zeolite molecular sieve.

[0036] Comparative Example 4 A process for preparing zeolite molecular sieves for water treatment using red mud, comprising the following steps: (1) The red mud is dried, ground, and passed through a 200-mesh sieve to obtain pretreated red mud; (2) The pretreated red mud was stirred with 5wt% sodium hydroxide solution and silicon source tetraethyl orthosilicate for 1 hour, and then sealed and aged at room temperature for 1 hour; wherein, the molar ratio of silicon oxide to aluminum oxide in the aged material was 2; the molar ratio of sodium oxide to aluminum oxide was 1; and the amount of template agent added was 3% of the total mass of aluminum oxide in the red mud; (3) The material aged in step (2) was transferred into a high-pressure reactor and hydrothermally reacted at 180°C for 8 hours. After the reaction was completed, the material was cooled, filtered, washed with deionized water until the pH of the filtrate was less than 9.5, and dried at 100°C overnight to obtain zeolite molecular sieve.

[0037] Example of effect Ammonia nitrogen removal rate: Prepare a 25 mg / L ammonium ion solution. Take 200 mL of the ammonia nitrogen solution into a 250 mL stoppered conical flask, add 0.2 g of the zeolite molecular sieve prepared in the example, and shake at 200 r / min for 30 minutes in a constant temperature shaking oven at 25℃. After reaching adsorption equilibrium, take the supernatant and filter it through a 0.45 μm filter membrane. Determine the ammonia nitrogen concentration using Nessler's reagent spectrophotometry. Ammonia nitrogen removal rate = 100% * (C0 - C) e ) / C0,C0,C e These are the initial and equilibrium concentrations, in mg / L.

[0038] Heavy metal adsorption efficiency: 0.3g of the zeolite molecular sieve prepared in the example was placed in 200mL of a 200mg / L CdCl2 solution, the pH was adjusted to 6, and the solution was shaken in a shaker at 25℃ and 200 rpm for 2 h. Subsequently, the Cd ion concentration in the solution was measured by atomic absorption spectrophotometer, and the pH value was adjusted by NaOH and HCl solutions. Heavy metal adsorption efficiency = 100%*(C1-C2) / C1, where C1 and C2 are the initial concentration and the concentration at 2 h, respectively.

[0039] Table 1 below shows the performance test results of the zeolite molecular sieves prepared in the examples: Table 1

[0040] As shown in Table 1, the zeolite molecular sieves prepared in Examples 1-3 have a larger specific surface area and higher ammonia nitrogen removal rate and heavy metal removal rate.

[0041] The difference between Comparative Example 1 and Example 2 is that no recycled and purified leachate was introduced for secondary hydrothermal treatment; the difference between Comparative Example 2 and Example 2 is that no template agent was introduced; Comparative Example 3 is a prior art method that only uses red mud to introduce a template agent to prepare zeolite molecular sieves; the difference between Comparative Example 4 and Comparative Example 3 is that no template agent was introduced. After comparison, Example 2 uses leaching residue from electrolytic manganese slag and red mud as raw materials, and introduces recycled and purified leachate for secondary hydrothermal treatment, resulting in a larger specific surface area and higher removal rates of ammonia nitrogen and heavy metals from wastewater.

[0042] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for preparing zeolite molecular sieves for water treatment using red mud, characterized in that, The preparation steps include: (1) Pretreatment of red mud; (2) The red mud pretreated in step (1) is mixed with the alkali-melted slag, and an alkali source and a silicon source are introduced for mixing and aging; (3) Perform a hydrothermal treatment on the material aged in step (2); (4) Disperse the material from the first hydrothermal treatment in step (3) in the manganese recovery solution, then add sodium chlorate solution to mix, and perform a second hydrothermal treatment to obtain zeolite molecular sieve.

2. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, The step (1) is as follows: dry, grind and sieve the red mud.

3. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, The step (2) is as follows: the alkali-melted slag and the red mud pretreated in step (1) are mixed at a mass ratio of (0.8~1):1, and then 4~6wt% sodium hydroxide solution and silicon source are added and stirred for 0.5~1h, and then aged at room temperature in a sealed manner for 1~24h; the molar ratio of silicon oxide to aluminum oxide in the material aged in step (2) is 1.5~5; the molar ratio of sodium oxide to aluminum oxide is 0.5~3.

4. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, The alkali-melted slag is obtained by calcining a mixture of leaching residue and sodium hydroxide; the manganese recovery solution is obtained by recycling and treating the leaching solution.

5. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 4, characterized in that, The preparation steps of the leaching residue are as follows: electrolytic manganese slag and 10wt% sulfuric acid solution are mixed at a solid-liquid ratio of 1: (7~8), stirred at 90~95℃ for 3~4h, and then filtered to obtain leaching solution and filter residue. The filter residue is washed until neutral, dried, and ground to obtain leaching residue.

6. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 4, characterized in that, The preparation steps of the manganese recovery solution are as follows: Add 0.047~0.055 times the volume of the leachate to a 3wt% hydrogen peroxide solution, then add 5wt% calcium oxide solution to adjust the pH to 4.5~5, stir at room temperature for 30 min, filter and collect the filtrate, raise the temperature to 88~92℃, add 0.1~0.12 parts by weight of manganese fluoride from the leachate, stir for at least 2 h, filter and collect the filtrate, add 0.00023~0.00032 parts by weight of barium sulfide from the leachate at 55~65℃, stir for 50~60 min, filter and collect the filtrate to obtain the manganese recovery solution.

7. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, In step (2), a template agent may also be added, and the amount of template agent added is 3% of the total mass of alumina in the red mud and alkali molten slag.

8. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, In step (3), the hydrothermal temperature is 70~180℃ and the hydrothermal reaction time is 3~24h.

9. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 1, characterized in that, The step (4) is as follows: the material from the first hydrothermal treatment in step (3) is dispersed in the manganese recovery liquid by ultrasonic dispersion for 30-40 min, and then sodium chlorate solution is added. The ratio of sodium chlorate to manganese in the manganese recovery liquid is (0.4-0.48):

1. The mixture is stirred and dispersed for 30-60 min, and then hydrothermally treated at 80-95℃ for 3-12 h.

10. The process for preparing zeolite molecular sieves for water treatment using red mud according to claim 9, characterized in that, The mass ratio of the material in the primary hydrothermal treatment to the mass of manganese in the manganese recovery solution is (2~4):0.632.

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