A method for separating waste desulfurizer and preparing magnesium aluminum hydrotalcite

Abstract

The invention relates to a method for separating a waste desulfurizing agent and preparing magnesium aluminum hydrotalcite, and belongs to the technical field of solid waste utilization. The method can obtain the resource recovery of the components of the waste desulfurizing agent, especially cerium and vanadium, prevent the loss and waste of heavy metals, reduce the pollution to the environment, meet the environmental protection requirements of sustainable development, and the magnesium aluminum hydrotalcite prepared by using the magnesium aluminum component with the highest content has a complete product structure and a large specific surface area, which not only reduces the production cost of the magnesium aluminum hydrotalcite, but also realizes the high added value utilization of the solid waste resource process, and has great economic and environmental significance.

Description

Technical Field

[0001] The invention relates to a method for separating a waste desulfurizing agent and preparing magnesium aluminum hydrotalcite, belonging to the technical field of solid waste utilization. Background Art

[0002] Desulfurizers are widely used in many chemical industries such as coal chemical industry, natural gas, oil refining, hydrogen extraction, biogas, etc. for the removal of sulfides. Industrial desulfurizers are mainly composed of MgO, Al2O3 as main components and a certain amount of cerium oxide, vanadium oxide and other auxiliary agents. The typical composition of De-SOx agent is 36~40% magnesium oxide, 46~50% aluminum oxide, 10~14% cerium oxide and 2~3% vanadium oxide. Cerium in the desulfurizer acts as an oxidant and can oxidize SO2 to SO3; vanadium can accelerate the oxidation rate of SO2 and the rate of sulfate reduction to H2S. However, with the continuous recycling of desulfurizers, the desulfurization activity gradually decreases, and the desulfurization effect cannot be achieved. Moreover, the vanadium in the desulfurizer will poison the molecular sieve in the catalytic cracking catalyst and deactivate it. The desulfurizer is difficult to escape the fact that it will eventually be scrapped. Waste desulfurizers have gradually become a new source of solid pollution. It is imperative to reasonably handle these waste desulfurizers.

[0003] At present, the main treatment methods for solid waste desulfurizers include regeneration, landfill, acid recovery, etc. Among them, the regeneration method has a limited number of regeneration times and affects the desulfurization efficiency; the landfill method is not only expensive, but also causes environmental pollution and waste of resources; the acid recovery has problems such as large acid consumption, difficult separation of impurity components and high requirements for operating equipment. Li Li et al. used sulfuric acid to leach mixed solids in patent CN 111607704A, and then added a carbonizing agent to the leachate to complete the treatment of waste desulfurizer. However, this method uses a large amount of concentrated sulfuric acid, the operation is complicated, and some components are difficult to separate. According to the properties of different components of the waste desulfurizer, the multi-stage dissolution-precipitation filtration method can be used to recover different components, especially rare earth metals and harmful heavy metals, and then the main components are reused, which can realize the green comprehensive recycling of waste desulfurizers.

[0004] Magnesium aluminum hydrotalcite is a type of layered inorganic material with a special structure. The interlayer anions are exchangeable, and the interlayer spacing changes regularly with the different interlayer ions. It is widely used in ion exchange, adsorption separation, catalysis, medicine, flame retardancy and other fields. At present, the synthesis methods of hydrotalcite include coprecipitation, hydrothermal synthesis, roasting reduction, ion exchange, sol-gel method, etc. Among them, the coprecipitation method is most suitable for industrial production application due to its advantages such as simple operation, easy control and low equipment requirements. It is the most basic and most commonly used method.

[0005] In the prior art, Zhu Binglong et al. separated precious metal platinum from carrier alumina in patent CN 111777085 A of waste dehydrogenation catalyst, and then prepared magnesium aluminum hydrotalcite by hydrothermal method. The preparation method is complicated, requires additional preparation of seed crystals, and has high requirements on equipment.

[0006] Waste desulfurizer contains rich magnesium and aluminum elements, and the aluminum-magnesium molar ratio is close to 1:1. It can be used as a raw material for preparing magnesium-aluminum hydrotalcite with a wide range of uses. However, the auxiliary components such as cerium and vanadium contained in it will directly cause the loss of rare earth metal elements if not recycled, and will pollute the environment. At present, there is no report on the separation and recovery of waste desulfurizer products and the use of their magnesium and aluminum components to prepare hydrotalcite. Summary of the invention

[0007] The purpose of the present invention is to provide a method for separating waste desulfurizer components and preparing magnesium-aluminum hydrotalcite, which can obtain the resource recovery of waste desulfurizer components, especially cerium and vanadium, prevent the loss and waste of heavy metals, reduce pollution to the environment, meet the environmental protection requirements of sustainable development, and use the magnesium-aluminum components with the highest content to prepare the magnesium-aluminum hydrotalcite product with a complete structure and a large specific surface area, which not only reduces the production cost of the magnesium-aluminum hydrotalcite, but also realizes the high added value utilization of the solid waste resource process, and has great economic and environmental significance.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for separating waste desulfurizing agent and preparing magnesium aluminum hydrotalcite, the method comprising the following steps:

[0010] (1) adding a certain amount of sodium hydroxide to the waste desulfurizer, mixing and grinding to obtain a mixed powder;

[0011] (2) roasting the mixed powder in step (1), adding water after cooling, stirring, leaching, filtering, and collecting the residue S1 and the filtrate L1 respectively;

[0012] (3) heating the filtrate L1 in step (2) to a certain temperature, adding barium ions, and filtering to obtain a filter residue S2 and a filtrate L2;

[0013] (4) After the filter residue S1 in step (2) is washed with pure water until it is neutral, a certain amount of dilute nitric acid solution is added at room temperature, and after reaction, the filter residue S3 and filtrate L3 are obtained by filtration, and the filtrate L2 and filtrate L3 in step (3) are fixed to volume;

[0014] (5) Adding a precipitant to the filtrate L2 in step (3) and the filtrate L3 in step (4) in a certain proportion under controlled temperature conditions to carry out a parallel flow co-precipitation reaction, performing an aging treatment after the reaction, and then separating the mother liquor from the product after the aging treatment, washing and drying, to obtain the target magnesium aluminum hydrotalcite product.

[0015] The waste desulfurizer in step (1) mainly comprises MgO, Al2O3 as main components and a certain amount of cerium, vanadium and other auxiliary agents.

[0016] Preferably, the mass ratio of the waste desulfurizing agent to sodium hydroxide in step (1) is 1:1.0-2.0.

[0017] Preferably, the calcination in step (2) is carried out in a muffle furnace, the calcination temperature is 400-600°C, and the calcination time is 1-3 hours. The calcination in the muffle furnace at high temperature can remove organic impurities adsorbed on the surface of the waste desulfurizer, and react in a molten state. After the reaction product is dissolved in water, the amphoteric characteristics of aluminum oxide and vanadium oxide, aluminum and vanadium oxides are all transferred to the liquid phase and dissolved in the filtrate L1, and the insoluble matter S1 is mainly composed of cerium and magnesium oxides.

[0018] Preferably, in step (3), the heating temperature of the filtrate L1 is 30-50° C.; and the barium ions are one or both of barium hydroxide and barium nitrate.

[0019] Preferably, the barium ion is barium hydroxide.

[0020] Preferably, the mass concentration of the dilute nitric acid solution in step (4) is 10-20%.

[0021] In step (3), the filtrate L2 is a sodium aluminate solution, and the filter residue is a Ba3(VO4)2 precipitate.

[0022] Vanadium oxide can react with barium ions to form a precipitate Ba3(VO4)2. Adding a certain amount of barium ions can separate vanadium from aluminum, and collecting the filter residue to recover vanadium.

[0023] The solubility of Ba3(VO4)2 precipitate is the lowest in the solution at 30~50℃, and at this temperature, almost all of the vanadium exists in the filter residue in the form of Ba3(VO4)2 precipitate.

[0024] The filter residue S3 in step (4) is a cerium dioxide precipitate.

[0025] The filtrate L3 in step (4) is a magnesium nitrate solution.

[0026] Preferably, the feed rate of filtrate L2 and filtrate L3 is 1:1~3; the precipitant is one or more of sodium hydroxide, ammonia water, and sodium carbonate; the pH range of the parallel co-precipitation reaction is 8.5~10, and the controlled temperature is 30~80°C; the aging is standing at the reaction temperature for 1~4 hours.

[0027] The mother liquor separation in step (5) is carried out by plate and frame filter pressing, centrifuge separation, etc.

[0028] The washing in step (5) is to wash the reactants three or more times with deionized water to remove unreacted sodium ions, nitrate ions, etc. adsorbed on the surface, preferably three times.

[0029] Preferably, the drying in step (5) is carried out at a temperature of 60 to 120° C. for 2 to 10 hours.

[0030] The beneficial effects of the present invention are:

[0031] The invention adopts a multi-stage leaching-precipitation filtration method with simple operation and low cost to realize the recovery and collection of various components of the waste desulfurizer, prevent the loss and waste of heavy metals such as cerium and vanadium, and reduce pollution to the environment. It also makes full use of the abundant magnesium and aluminum components to prepare magnesium-aluminum hydrotalcite with complete structure, large specific surface area and uniform pore distribution, realizes the secondary utilization of solid waste resources, meets the high added value utilization and environmental protection requirements in the process of solid waste resource utilization, and has great economic and environmental significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 2 are XRD patterns of different embodiments of the present invention.

[0033] Figure 2 This is a specific surface area diagram of Example 1 of the present invention.

[0034] Figure 3 This is the pore distribution diagram of Example 1 of the present invention.

[0035] Figure 4 This is the SEM image of Example 1 of the present invention. DETAILED DESCRIPTION

[0036] Example 1

[0037] (1) First, the waste desulfurizer was placed in a planetary ball mill and ball-milled for 30 minutes to obtain waste desulfurizer powder particles. Then, 50.0 g of the waste desulfurizer powder particles and 50.0 g of sodium hydroxide were weighed and mixed and added to the planetary ball mill. Then, the mixture was ball-milled for another 15 minutes to obtain a mixed powder.

[0038] (2) The obtained mixed powder was placed in a muffle furnace and calcined at 500°C for 1 hour. After calcination, it was cooled to room temperature and dissolved in 200 ml of pure water. The mixture was stirred at room temperature for 60 minutes, and then the solution was filtered to obtain an oxide residue containing magnesium and cerium and a filtrate containing aluminum and vanadate ions.

[0039] (3) The filtrate containing aluminum and vanadate ions in step (2) is heated to 40°C in a water bath, and a small amount of barium hydroxide is added dropwise until no white precipitate is produced. The addition is stopped. The Ba3(VO4)2 precipitate and the purified sodium aluminate solution are obtained by filtration, and the precipitate is washed, dried, and recovered.

[0040] (4) The oxide residue containing magnesium and cerium in step (2) is washed with pure water until it becomes neutral and then placed in a beaker. 100 ml of a 20% by volume dilute nitric acid solution is added and stirred to dissolve. The residue is filtered to obtain a cerium dioxide precipitate insoluble in dilute nitric acid and a magnesium nitrate filtrate soluble in nitric acid. The cerium dioxide precipitate is washed, dried and collected as required as a rare earth oxide. The purified sodium aluminate solution and magnesium nitrate solution are fixed to 250 ml.

[0041] (5) The sodium aluminate filtrate in step (3) and the magnesium nitrate filtrate in step (4) were fed at a feed rate ratio of 1:2, and a mixed solution of sodium carbonate and sodium hydroxide in a molar ratio of 1:10 was used as a precipitant. The pH was controlled to be 10, and co-precipitation was carried out at 50°C. After the precipitation was completed, the mixture was allowed to stand for 1 hour and centrifuged. The filter residue was washed three times with pure water and then dried at 80°C for 10 hours to obtain a magnesium aluminum hydrotalcite product. 42.1 g of magnesium aluminum hydrotalcite was obtained, and the yield was 83.85%.

[0042] Example 2

[0043] (1) First, the waste desulfurizer was placed in a planetary ball mill and ball-milled for 30 minutes to obtain waste desulfurizer powder particles. Then, 50.0 g of the waste desulfurizer powder particles and 60.0 g of sodium hydroxide were weighed and mixed and added to the planetary ball mill. Then, the mixture was ball-milled for another 60 minutes to obtain a mixed powder.

[0044] (2) The obtained mixed powder was placed in a muffle furnace and calcined at 400°C for 3 hours. After calcination, it was cooled to room temperature, dissolved in 200 ml of pure water, stirred at room temperature for 30 minutes, and then the solution was filtered to obtain an oxide residue containing magnesium and cerium and a filtrate containing aluminum and vanadate ions.

[0045] (3) The filtrate containing aluminum and vanadate ions in step (2) is heated to 30°C in a water bath, and a small amount of barium hydroxide is added dropwise until no white precipitate is produced. The addition is stopped. Ba3(VO4)2 precipitate and sodium aluminate solution are obtained by filtration, and the precipitate is washed, dried, and recovered.

[0046] (4) The oxide residue containing magnesium and cerium in step (2) is washed with pure water until it becomes neutral and then placed in a beaker. 100 ml of a 20% by volume dilute nitric acid solution is added and stirred to dissolve. The residue is filtered to obtain a cerium dioxide precipitate insoluble in dilute nitric acid and a magnesium nitrate filtrate soluble in nitric acid. The cerium dioxide precipitate is washed, dried and collected as required as a rare earth oxide. The purified sodium aluminate solution and magnesium nitrate solution are fixed to 250 ml.

[0047] (5) The sodium aluminate filtrate in step (3) and the magnesium nitrate filtrate in step (4) were fed at a feed rate ratio of 1:1, and 20% by mass of sodium hydroxide was used as a precipitant. The pH was controlled to be 9, and co-precipitation was carried out at 80°C. After the precipitation was completed, the mixture was allowed to stand for aging for 2 hours, and then centrifuged and filtered. The filter residue was washed three times with pure water and then dried at 120°C for 2 hours to obtain 48.5 g of magnesium aluminum hydrotalcite product with a yield of 66.37%.

[0048] Example 3

[0049] (1) First, the waste desulfurizer was placed in a planetary ball mill and ball-milled for 30 minutes to obtain waste desulfurizer powder particles. Then, 50.0 g of the waste desulfurizer powder particles and 100.0 g of sodium hydroxide were weighed and mixed and added to the planetary ball mill. Then, the mixture was ball-milled for another 60 minutes to obtain a mixed powder.

[0050] (2) The obtained mixed powder was placed in a muffle furnace and calcined at 600°C for 2 hours. After calcination, it was cooled to room temperature, dissolved in 200 ml of pure water, stirred at room temperature for 30 minutes, and then the solution was filtered to obtain an oxide residue containing magnesium and cerium and a filtrate containing aluminum and vanadate ions.

[0051] (3) The filtrate containing aluminum and vanadate ions in step (2) is heated to 50°C in a water bath, and a small amount of barium hydroxide is added dropwise until no white precipitate is produced. The addition is stopped. Ba3(VO4)2 precipitate and sodium aluminate solution are obtained by filtration, and the precipitate is washed, dried, and recovered.

[0052] (4) The oxide residue containing magnesium and cerium in step (2) is washed with pure water until it becomes neutral and then placed in a beaker. 200 ml of a 10% by volume dilute nitric acid solution is added and stirred to dissolve. The residue is filtered to obtain a cerium dioxide precipitate insoluble in dilute nitric acid and a magnesium nitrate filtrate soluble in nitric acid. The cerium dioxide precipitate is washed, dried and collected as required as a rare earth oxide. The purified sodium aluminate solution and magnesium nitrate solution are fixed to 250 ml.

[0053] (5) The sodium aluminate filtrate in step (3) and the magnesium nitrate filtrate in step (4) were fed at a feed rate ratio of 1:3, and a 10% by mass sodium hydroxide mixed solution was used as a precipitant. The pH was controlled to be 8.5, and co-precipitation was carried out at 30° C. After the precipitation was completed, the mixture was allowed to stand for aging for 4 h, and then centrifuged and filtered. The filter residue was washed three times with pure water and then dried at 60° C. for 8 h to obtain 38.2 g of magnesium aluminum hydrotalcite product with a yield of 76.08%.

[0054] The products in the above examples 1-3 were subjected to XRD tests respectively. Figure 1As shown in the figure, after comparison with the standard card 89-0460, the prepared sample has typical diffraction peaks (003), (006) and (009) of magnesium aluminum hydrotalcite, the baseline is stable, and the characteristic diffraction peaks are strong and sharp, indicating that the crystal structure of the magnesium aluminum hydrotalcite product is relatively regular and the crystal phase is relatively single. Then, the specific surface area analyzer is used to characterize the BET and pore distribution of the product of Example 1, as shown in the figure. Figure 2 and Figure 3 As shown in the figure, the characterization results are: specific surface area 191.21m² / g, total pore volume 0.29 cm³ / g, mesopore volume 0.28 cm³ / g, most probable pore diameter 11.4nm, and uniform pore diameter distribution. Then, the morphology of the sample in Example 1 was analyzed using a scanning electron microscope. Figure 4 As shown, the prepared magnesium aluminum hydrotalcite crystals are stacked in clusters and have a regular crystal shape.

[0055] The embodiments described in the present invention are merely descriptions of the preferred implementation modes of the present invention and should not be regarded as limitations of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in the field should all fall within the protection scope of the present invention. The protection scope of the present invention should be based on the scope defined by the claims.

Claims

1. A method for separating waste desulfurizer and preparing magnesium aluminum hydrotalcite, characterized in that: The method comprises the following steps: (1) adding a certain amount of sodium hydroxide to the waste desulfurizer, mixing and grinding to obtain a mixed powder; (2) roasting the mixed powder in step (1), adding water after cooling, stirring, leaching, filtering, and collecting the residue S1 and the filtrate L1 respectively; (3) heating the filtrate L1 in step (2) to a certain temperature, adding barium ions, and filtering to obtain a filter residue S2 and a filtrate L2; (4) After the filter residue S1 in step (2) is washed with pure water until it is neutral, a certain amount of dilute nitric acid solution is added at room temperature, and after reaction, the filter residue S3 and filtrate L3 are obtained by filtration, and the filtrate L2 and filtrate L3 in step (3) are fixed to volume; (5) adding a precipitant to the filtrate L2 in step (3) and the filtrate L3 in step (4) in a certain proportion under controlled temperature conditions to carry out a co-current co-precipitation reaction, performing an aging treatment after the reaction, and then separating the mother liquor from the product after the aging treatment, washing and drying, to obtain the target magnesium aluminum hydrotalcite product; The waste desulfurizer in step (1) mainly comprises MgO, Al2O3 as main components and a certain amount of cerium and vanadium additives; the filtrate L2 in step (3) is a sodium aluminate solution, and the filter residue S2 is a Ba3(VO4)2 precipitate; the filter residue S3 in step (4) is a cerium dioxide precipitate; the filtrate L3 in step (4) is a magnesium nitrate solution; The feed rate ratio of filtrate L2 and filtrate L3 is 1:1~3; the precipitant is one or more of sodium hydroxide, ammonia water, and sodium carbonate; the pH range of the parallel co-precipitation reaction is 8.5~10, and the controlled temperature is 30~80°C; the aging is standing at the reaction temperature for 1~4 hours.

2. The method for separating and preparing magnesium aluminum hydrotalcite from waste desulfurizing agent according to claim 1, characterized in that: The mass ratio of the waste desulfurizing agent to sodium hydroxide in step (1) is 1:1.0-2.

0.

3. The method for separating and preparing magnesium aluminum hydrotalcite from waste desulfurizing agent according to claim 1, characterized in that: The calcination in step (2) is carried out in a muffle furnace, the calcination temperature is 400-600° C., and the calcination time is 1-3 hours.

4. The method for separating and preparing magnesium aluminum hydrotalcite from waste desulfurizing agent according to claim 1, characterized in that: In step (3), the heating temperature of the filtrate L1 is 30-50° C.; the barium ions are one or both of barium hydroxide and barium nitrate.

5. The method for separating and preparing magnesium aluminum hydrotalcite from waste desulfurizing agent according to claim 1, characterized in that: The mass concentration of the dilute nitric acid solution in step (4) is 10-20%.

6. The method for separating and preparing magnesium aluminum hydrotalcite from waste desulfurizing agent according to claim 1, characterized in that: The drying in step (5) is carried out at a temperature of 60 to 120° C. for 2 to 10 hours.

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