A composite seed for recovering lead ions in wastewater, a preparation method and a core seed granulation and salt separation process

Abstract

The present disclosure relates to the technical field of wastewater treatment, and particularly relates to a composite seed for recovering lead ions in wastewater, a preparation method and a core seed granulation and salt separation process. The composite seed disclosed by the present disclosure takes lead-aluminum layered double hydroxide as a matrix material, and a layered molybdenum disulfide is loaded on the surface of the composite seed to obtain a lead-specific composite seed. In the core seed granulation and salt separation process, for multi-element lead-containing wastewater, the composite seed can strengthen the selective capture / enrichment capacity of lead ions in the wastewater, significantly improve the purity and density of the granules, and the obtained granules have low water content and can be directly used in industrial production.

Description

Technical Field

[0001] This disclosure relates to the field of wastewater treatment technology, and in particular to a composite seed crystal for recovering lead ions from wastewater, its preparation method, and a nucleus crystal granulation and salt separation process. Background Technology

[0002] The research and application of new energy batteries have promoted the transformation of social energy, reduced dependence on traditional fossil fuels, lowered carbon emissions, and promoted the utilization of renewable energy. However, the mass production of new energy batteries has led to the generation of large amounts of wastewater containing precious metal ions. The discharge of this wastewater not only results in the loss of precious metal resources but also causes serious environmental pollution. Therefore, the resource recovery and comprehensive utilization of precious metal resources in new energy battery wastewater has significant economic and environmental benefits.

[0003] For the treatment of wastewater from new energy batteries, commonly used processes include chemical precipitation, electrolysis, and ion exchange. Electrolysis utilizes direct current to conduct oxidation-reduction reactions. By controlling the electrode potential, it can obtain single metals with relatively high purity, making it suitable for treating high-concentration wastewater and wastewater with good separation. However, it has high energy consumption and operating costs, and requires a heavy metal concentration in the wastewater greater than 2-3 g / L to achieve high current efficiency, making it unsuitable for treating low-concentration wastewater. Ion exchange can enrich and concentrate trace heavy metal ions in wastewater, making the regenerated liquid easier to recover. However, the capacity of ion exchange resins is limited, and the regeneration process requires the use of chemical agents, which can easily cause secondary pollution of water bodies. Chemical precipitation has the advantage of simple process and large water treatment capacity, but its treatment precision is limited. It often requires coupled ion exchange resin processes for final precision treatment to ensure that the effluent meets discharge standards. In addition, the large amount of high-moisture sludge generated by chemical precipitation requires further treatment, resulting in a lengthy process, large footprint, and high treatment costs. Furthermore, this method has weak selective recovery capability for precious metal ions in new energy battery wastewater.

[0004] In recent years, research on nucleogranulation and salt separation technology for the recovery of heavy metal ions from wastewater has increased, and some progress has been made. Nucleogranulation and salt separation technology can avoid sludge generation and reduce the cost of heavy metal ion recovery. However, for wastewater containing multiple metal ions, such as wastewater from new energy batteries containing cobalt, lead, zinc, and nickel ions, conventional commercial seed crystals such as quartz sand, garnet, coal gangue, hematite, and fluorite can only remove multiple metal ions simultaneously, failing to achieve selective recovery of lead ions. This results in lower purity of the final granules, thus reducing recovery efficiency.

[0005] Therefore, how to provide a special seed crystal that can selectively and efficiently recover lead ions from wastewater, thereby improving the purity of the resulting granules and increasing economic benefits, has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a composite seed crystal for recovering lead ions from wastewater, a preparation method, and a nucleus crystal granulation and salt separation process. The composite seed crystal uses lead-aluminum layered bimetallic hydroxide as the matrix material, and a lead-specific composite seed crystal is obtained by loading layered molybdenum disulfide onto the surface. The composite seed crystal enhances the selective capture / enrichment ability of lead ions in new energy battery wastewater, significantly improves the purity and density of the granules, and the resulting granules have a low water content, making them suitable for direct industrial application.

[0007] In a first aspect, this disclosure provides a composite seed crystal for recovering lead ions from wastewater, the composite seed crystal comprising a lead-aluminum layered bimetallic hydroxide and layered molybdenum disulfide loaded on the surface of the lead-aluminum layered bimetallic hydroxide.

[0008] In this disclosure, a lead-aluminum layered bimetallic hydroxide is used as the matrix material. Its crystal structure is similar to that of lead ion precipitates (obtained by the reaction of lead ions in lead-containing wastewater with a precipitant), which effectively reduces the nucleation energy barrier of lead ion precipitation on the seed crystal surface and enhances the selective adhesion and precipitation of lead ions. Furthermore, the selective enrichment ability of lead ions is further enhanced by loading layered molybdenum disulfide onto the surface of the matrix material. Each layer of the layered molybdenum disulfide consists of one layer of molybdenum atoms and two layers of sulfur atoms, with each sulfur atom forming a hexagonal ring structure around a central molybdenum atom. The molybdenum atoms are typically molybdenum atoms in the form of Mo... 4+ Sulfur atoms exist primarily in the form of S. 2- S exists in the form of 2- It has a strong bonding energy with lead ions and tends to form stable Pb-S bonds, thereby fixing lead ions to the material surface and achieving selective capture of lead ions in a multi-element ion coexistence system.

[0009] The following are preferred technical solutions of this disclosure, but are not intended to limit the technical solutions provided by this disclosure. The technical objectives and beneficial effects of this disclosure can be better achieved through the following technical solutions.

[0010] As a preferred technical solution of this disclosure, in the composite seed crystal, the mass ratio of the lead-aluminum layered bimetallic hydroxide to the layered molybdenum disulfide is 1:(0.15-0.6), for example, 1:0.15, 1:0.20, 1:0.25, 1:0.30, 1:0.35, 1:0.40, 1:0.45, 1:0.50, 1:0.55 or 1:0.60, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0011] In this disclosure, a suitable loading of layered molybdenum disulfide can synergistically enhance the capture effect of lead ions with the lead-aluminum layered bimetallic hydroxide matrix material. However, excessive loading of layered molybdenum disulfide can lead to overly strong adsorption. Because the lattice structure of molybdenum disulfide is inconsistent with that of the product to be precipitated, lead ions cannot nucleate and grow on the surface of molybdenum disulfide. Consequently, the resulting crystalline product cannot grow into dense spherical particles, thus failing to enhance the solid-liquid separation efficiency.

[0012] As a preferred technical solution of this disclosure, in the lead-aluminum layered bimetallic hydroxide, the molar ratio of lead to aluminum is (4-8):(1.5-5), such as 4:1.5, 4:5, 5:5, 7:4, 8:4 or 8:5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] In this disclosure, appropriate amounts of lead and aluminum are beneficial for enhancing the capture capacity of lead ions; however, excessive amounts of either lead or aluminum will lead to the collapse of the layered structure, resulting in a decrease in the specific surface area of ​​the material and a weakening of its ability to capture lead ions.

[0014] Secondly, this disclosure provides a method for preparing composite seed crystals as described in the first aspect, the method comprising the following steps:

[0015] Lead-aluminum layered bimetallic hydroxides were prepared by co-precipitation method;

[0016] Layered molybdenum disulfide was synthesized using a hydrothermal method;

[0017] The obtained lead-aluminum layered bimetallic hydroxide was mixed with a silane coupling agent and a first solvent to react and obtain an intermediate complex.

[0018] The intermediate complex was mixed with the obtained layered molybdenum disulfide to react and obtain a composite seed crystal for recovering lead ions from wastewater.

[0019] As a preferred technical solution of this disclosure, the step of preparing lead-aluminum layered bimetallic hydroxide by coprecipitation includes: mixing a mixed metal salt solution with an alkaline solution and reacting to obtain lead-aluminum layered bimetallic hydroxide; wherein the mixed metal salt solution includes soluble lead salt and soluble aluminum salt.

[0020] Preferably, the concentration of Pb in the mixed metal salt solution is 4-8 mol / L, such as 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L or 8 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the concentration of Al in the mixed metal salt solution is 1.5-5 mol / L, such as 1.5 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the alkaline solution includes sodium carbonate and / or sodium hydroxide.

[0023] Preferably, the concentration of sodium carbonate in the alkaline solution is 0.4-1.6 mol / L, such as 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L or 1.6 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] Preferably, the concentration of sodium hydroxide in the alkaline solution is 1-3.5 mol / L, such as 1 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or 3.5 mol / L, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] Preferably, the volume ratio of the mixed metal salt solution to the alkaline solution is 1:(1-5), such as 1:1, 1:2, 1:3, 1:4 or 1:5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the reaction temperature for preparing lead-aluminum layered bimetallic hydroxide by the co-precipitation method is 30-60℃, such as 30℃, 40℃, 50℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the reaction time for preparing lead-aluminum layered bimetallic hydroxide by the co-precipitation method is 30-120 min, such as 30 min, 60 min, 90 min or 120 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the lead-aluminum layered bimetallic hydroxide is further dried to obtain the product.

[0029] Preferably, the drying temperature is 30-40°C, such as 30°C, 32°C, 36°C or 40°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the drying time is 6-12 hours, such as 6 hours, 8 hours, 10 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] As a preferred technical solution of this disclosure, the steps of the hydrothermal synthesis of layered molybdenum disulfide include: mixing a molybdenum source and a sulfur source with a second solvent according to a stoichiometric ratio, and then vacuum drying the precipitate obtained after the reaction to obtain layered molybdenum disulfide.

[0032] Preferably, the molybdenum source comprises ammonium molybdate.

[0033] Preferably, the sulfur source includes thiourea and / or sodium thiosulfate.

[0034] Preferably, the second solvent comprises water.

[0035] Preferably, the reaction temperature for the hydrothermal synthesis of layered molybdenum disulfide is 150-170℃, such as 150℃, 155℃, 160℃, 165℃ or 170℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the reaction time for the hydrothermal synthesis of layered molybdenum disulfide is 8-10 hours, such as 8 hours, 8.5 hours, 9 hours or 10 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the hydrothermal synthesis of layered molybdenum disulfide is carried out under a protective atmosphere.

[0038] Preferably, the reaction pressure for the hydrothermal synthesis of layered molybdenum disulfide is 0.02-0.3 GPa, such as 0.02 GPa, 0.05 GPa, 0.1 GPa, 0.15 GPa, 0.2 GPa, 0.25 GPa or 0.3 GPa, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0039] Preferably, the vacuum drying temperature is 50-80℃, such as 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] As a preferred technical solution of this disclosure, the silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltri(β-methoxyethoxy)silane, such as a combination of vinyltriethoxysilane and vinyltrimethoxysilane, or a combination of vinyltrimethoxysilane and vinyltri(β-methoxyethoxy)silane, etc.

[0041] Preferably, the first solvent includes water.

[0042] Preferably, the mass ratio of the lead-aluminum layered bimetallic hydroxide to the silane coupling agent is 1:(0.04-0.4), for example, 1:0.04, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35 or 1:0.4, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0043] Preferably, the reaction time between the lead-aluminum layered bimetallic hydroxide and the silane coupling agent is 3-12 hours, such as 3 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, or 12 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the reaction temperature of the lead-aluminum layered bimetallic hydroxide with the silane coupling agent is 10-45°C, such as 10°C, 20°C, 30°C, 40°C or 45°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] As a preferred technical solution of this disclosure, the mass ratio of the intermediate complex to the molybdenum disulfide is 1:(0.1-0.6), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5 or 1:0.6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the reaction temperature of the intermediate complex with the molybdenum disulfide is 25-55°C, such as 25°C, 30°C, 35°C, 40°C, 45°C or 55°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the reaction time of the intermediate complex with the molybdenum disulfide is 30-150 min, such as 30 min, 60 min, 90 min, 120 min or 150 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Thirdly, this disclosure provides a nuclear crystal granulation and salt separation process, in which lead-containing wastewater is treated using composite seed crystals as described in the first aspect or composite seed crystals prepared by the preparation method described in the second aspect.

[0049] Preferably, the metal ions in the lead-containing wastewater also include one or more of cobalt, zinc, cadmium, or nickel.

[0050] As a preferred technical solution of this disclosure, the nucleus crystal granulation and salt separation process includes the following steps:

[0051] (1) Fill the composite seed crystals into the nucleation granulation reactor;

[0052] (2) The lead-containing wastewater and the precipitant are respectively introduced into the nucleation granulation reactor to make the seed crystals fluidized and react;

[0053] The regenerated water obtained after the reaction flows out from the upper end of the nucleogranulation reactor, and the granules obtained after the reaction are discharged from the lower end of the nucleogranulation reactor.

[0054] Preferably, the filling height of the composite seed crystal in step (1) is 15-25% of the height of the nucleus granulation reactor, such as 15%, 20% or 25%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the precipitant in step (2) includes a sodium carbonate solution and / or a sodium hydroxide solution.

[0056] Preferably, the concentration ratio of the precipitant in step (2) to the concentration of lead ions in the lead-containing wastewater is (0.4-0.8):1, for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1 or 0.8:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The unit of concentration is mg / L.

[0057] Preferably, the flow rate ratio of the precipitant to the flow rate of the lead-containing wastewater is 1:(15-20), such as 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The unit of flow rate is L / h.

[0058] Preferably, the reaction time in step (2) is 1-10 min, such as 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] In this disclosure, the flow rate of lead-containing wastewater, the concentration of the precipitant, and the flow rate can be selected and adjusted by those skilled in the art based on hydraulic and hydrochemical conditions.

[0060] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0061] This disclosure uses lead-aluminum layered bimetallic hydroxide as the matrix material and obtains a lead-specific composite seed crystal by loading layered molybdenum disulfide on its surface. The composite seed crystal enhances the selective capture / enrichment ability of lead ions in new energy battery wastewater, significantly improves the purity and density of the granules, and the resulting granules have low water content and can be directly used in industrial production. Attached Figure Description

[0062] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0063] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 The images show the FT-IR comparison of the composite seed crystals obtained in Examples 1-3 and Comparative Examples 2-3 of this disclosure.

[0065] Figure 2 The images show XRD comparisons of the composite seed crystals obtained in Examples 1-3 and Comparative Examples 2-3 of this disclosure.

[0066] Figure 3 This is a comparison chart showing the removal rates of cobalt ions, nickel ions, lead ions, and zinc ions in multi-element lead-containing wastewater by the composite seed crystals obtained in Examples 1-3 and Comparative Examples 2-3 of this disclosure.

[0067] Figure 4 This is a comparison chart showing the removal rates of cobalt, nickel, lead, and zinc ions in lead-containing wastewater using the five commercial seed crystals described in Comparative Example 1 of this disclosure. Detailed Implementation

[0068] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0069] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0070] Example 1

[0071] This embodiment provides a composite seed crystal for recovering lead ions from wastewater and its preparation method. The composite seed crystal includes a lead-aluminum layered bimetallic hydroxide and layered molybdenum disulfide loaded on the surface of the lead-aluminum layered bimetallic hydroxide.

[0072] The mass ratio of the lead-aluminum layered bimetallic hydroxide to the layered molybdenum disulfide is 1:0.6;

[0073] In the lead-aluminum layered bimetallic hydroxide, the molar ratio of lead to aluminum is 4:1.5.

[0074] The preparation method includes the following steps:

[0075] Preparation of lead-aluminum layered bimetallic hydroxides by coprecipitation method:

[0076] Prepare an alkaline solution comprising sodium carbonate and sodium hydroxide, wherein the concentration of sodium carbonate is 0.4 mol / L and the concentration of sodium hydroxide is 1 mol / L;

[0077] Prepare a mixed metal salt solution, including lead chloride and aluminum chloride, wherein the concentration of lead chloride is 4 mol / L and the concentration of aluminum chloride is 1.5 mol / L;

[0078] The above mixed metal salt solution and alkaline solution were mixed in a volume ratio of 1:1 and reacted at 30°C for 30 min. The resulting precipitate was separated into solid and liquid phases and dried at 30°C for 6 h to obtain lead-aluminum layered bimetallic hydroxide, denoted as Pb-Al-LDH.

[0079] Hydrothermal synthesis of layered molybdenum disulfide:

[0080] 2 mmol of ammonium molybdate tetrahydrate was dissolved in 60 mL of deionized water and stirred for 10 min. Then, 4 mmol of thiourea was added, and stirring was continued for 45 min to obtain a clear and transparent solution. The obtained clear and transparent solution was transferred to a 100 mL NSC classic quick-opening magnetically stirred reactor. After sealing, nitrogen gas was introduced, and the reaction was carried out at 100 MPa and 160 °C for 8 h to obtain a black precipitate. The obtained black precipitate was washed successively with deionized water and ethanol, and then dried under vacuum at 60 °C for 10 h to obtain layered molybdenum disulfide, denoted as MoS2.

[0081] 1 g of the obtained lead-aluminum layered bimetallic hydroxide and 0.04 g of vinyltriethoxysilane were added to 50 mL of water and heated in a water bath at 10 °C for 3 h to obtain an intermediate complex. Then, 0.6 g of layered molybdenum disulfide was added to it and heated in a water bath at 25 °C for 30 min to obtain a composite seed crystal, denoted as (Pb-Al-LDH)-MoS2(0.6), where 0.6 represents the mass ratio of MoS2 to Pb-Al-LDH.

[0082] Example 2

[0083] This embodiment provides a method for preparing a composite seed crystal for recovering lead ions from wastewater. The preparation method is the same as that in Example 1, except that: 1g of the obtained lead-aluminum layered bimetallic hydroxide and 0.22g of vinyltriethoxysilane are added to 50mL of water and heated in a water bath at 20°C for 6 hours to obtain an intermediate complex; then 0.3g of layered molybdenum disulfide is added to it and heated in a water bath at 45°C for 75 minutes to obtain a composite seed crystal, denoted as (Pb-Al-LDH)-MoS2(0.3).

[0084] Example 3

[0085] This embodiment provides a method for preparing a composite seed crystal for recovering lead ions from wastewater. The preparation method is the same as that in Example 1, except that: 1g of the obtained lead-aluminum layered bimetallic hydroxide and 0.4g of vinyltris(β-methoxyethoxy)silane are added to 50mL of water and heated in a water bath at 45°C for 12h to obtain an intermediate complex; then 0.15g of layered molybdenum disulfide is added to it and heated in a water bath at 55°C for 150min to obtain a composite seed crystal, denoted as (Pb-Al-LDH)-MoS2(0.15).

[0086] Comparative Example 1

[0087] This comparative example provides five commercially available seed crystals, specifically including:

[0088] The first commercially available seed crystal, quartz sand;

[0089] The second commercial seed crystal, garnet;

[0090] The third commercial seed crystal is coal gangue.

[0091] The fourth commercially available crystal is hematite;

[0092] The fifth commercially available crystal is fluorite.

[0093] Comparative Example 2

[0094] This comparative example provides a seed crystal, which is a lead-aluminum layered bimetallic hydroxide, prepared according to the preparation method in Example 1.

[0095] Comparative Example 3

[0096] This comparative example provides a seed crystal, which is layered molybdenum disulfide, prepared according to the preparation method in Example 1.

[0097] The composite seed crystals obtained in Examples 1-3 and the seed crystals obtained in Comparative Examples 2-3 were characterized.

[0098] The FT-IR comparison images of the composite seed crystals obtained in Example 1 ((Pb-Al-LDH)-MoS2(0.6)), Example 2 ((Pb-Al-LDH)-MoS2(0.3)), Example 3 ((Pb-Al-LDH)-MoS2(0.15)), Comparative Example 2 (Pb-Al-LDH), and Comparative Example 3 (MoS2) are shown below. Figure 1 As shown. From Figure 1 It can be seen that Pb-Al-LDH, (Pb-Al-LDH)-MoS2 (0.6), (Pb-Al-LDH)-MoS2 (0.3), and (Pb-Al-LDH)-MoS2 (0.15) are present at 682 cm⁻¹. -1 1407cm -1 and 1738cm -1 Characteristic peaks appeared at all locations, mainly attributed to the presence of the matrix material Pb-Al-LDH; for MoS2, a characteristic peak appeared at 1641 cm⁻¹. -1 1046cm -1 The obvious characteristic peaks appearing at the corresponding positions in the composite seed crystals indicate that MoS2 has been successfully loaded onto the surface of the Pb-A-LDH matrix material.

[0099] The XRD comparison images of the composite seed crystals obtained in Example 1 ((Pb-Al-LDH)-MoS2(0.6)), Example 2 ((Pb-Al-LDH)-MoS2(0.3)), Example 3 ((Pb-Al-LDH)-MoS2(0.15)), Comparative Example 2 (Pb-Al-LDH), and Comparative Example 3 (MoS2) are shown below. Figure 2 As shown. From Figure 2 It can be seen that the characteristic peaks of (Pb-Al-LDH)-MoS2(0.6), (Pb-Al-LDH)-MoS2(0.3), and (Pb-Al-LDH)-MoS2(0.15) at 14.5°, 39.7°, and 60.5° correspond to the characteristic peaks of MoS2, respectively, while Pb-Al-LDH does not show corresponding characteristic peaks at the above positions. For Pb-Al-LDH, the characteristic peaks at 24.7°, 26.9°, and 34.3° indicate that the synthesis of Pb-Al-LDH was successful, and the three composite seed crystals with different proportions also showed corresponding characteristic peaks at the above positions. This all indicates that MoS2 has been successfully loaded onto the surface of Pb-Al-LDH, which is consistent with the infrared spectrum.

[0100] Performance testing:

[0101] Using the composite seed crystals obtained in Examples 1-3, the five commercial seed crystals described in Comparative Example 1, and the seed crystals described in Comparative Examples 2-3 as test seed crystals, lead-containing wastewater was treated using a nucleus crystal granulation and salt separation process. The specific process included:

[0102] S1: Separately fill the test seed crystals into the 2m high nucleation granulation reactor, with the filling height being 20% ​​of the height of the nucleation granulation reactor;

[0103] S2: Lead-containing wastewater is introduced from the bottom of the nucleation granulation reactor at a flow rate of 20 L / h. At the same time, a sodium carbonate solution with a concentration of 124 mg / L is introduced from the lower end of the side wall of the nucleation granulation reactor at a flow rate of 1.2 L / h, so that the seed crystals to be tested are fluidized and reacted. The reaction time is 10 min.

[0104] The regenerated water obtained after the reaction flows out from the outlet of the nuclear crystal granulation reactor, and the granules obtained after the reaction are discharged from the granule outlet of the nuclear crystal granulation reactor.

[0105] The specific composition of lead-containing wastewater is shown in Table 1.

[0106] Table 1

[0107] lead ions cobalt ions Nickel ions Zinc ions Ion concentration (mg / L) 207.2 58.93 58.69 65.41

[0108] The concentrations and turbidity of the four ions in the reclaimed water were measured, and the results are shown in Table 2. The removal rates of the four ions in the reclaimed water were calculated, and the results are shown in Table 3.

[0109] Table 2

[0110]

[0111] Table 3

[0112]

[0113]

[0114] Furthermore, the comparison chart of the removal rates of cobalt ions, nickel ions, lead ions, and zinc ions in multi-element lead-containing wastewater by the composite seed crystals obtained in Example 1 ((Pb-Al-LDH)-MoS2(0.6)), Example 2 ((Pb-Al-LDH)-MoS2(0.3)), Example 3 ((Pb-Al-LDH)-MoS2(0.15)), Comparative Example 2 (Pb-Al-LDH), and Comparative Example 3 (MoS2) is shown below. Figure 3 As shown. From Figure 3It can be seen that, compared with Pb-Al-LDH materials and MoS2 materials, the composite seed crystals described in this disclosure have better selective separation and removal capabilities, with a removal rate of over 95.9% for lead ions, while the removal rates for the other three ions are all below 20%.

[0115] The comparison chart of the removal rates of cobalt ions, nickel ions, lead ions, and zinc ions by the five commercial seed crystals described in Comparative Example 1 in lead-containing multi-element wastewater is shown below. Figure 4 As shown. From Figure 4 It can be seen that the five commercially available crystal seeds all have good removal capabilities for cobalt, lead, zinc, and nickel ions in lead-containing wastewater. Among them, the five commercially available crystal seeds have a higher removal rate for lead ions compared to the other metal ions, but the maximum difference in removal rate compared to the other three ions does not exceed 30%. This indicates that the five commercially available crystal seeds have a weak selective recovery capability for lead ions, which is insufficient to separate and recover lead ions from the other three metal ions, resulting in low purity of the final granules and low recovery efficiency.

[0116] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0117] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite seed for recovering lead ions in wastewater, characterized by, The preparation method comprises the following steps: The lead-aluminum layered double hydroxide is prepared by a coprecipitation method; a mixed metal salt solution and an alkaline solution are mixed to obtain the lead-aluminum layered double hydroxide; the mixed metal salt solution comprises a soluble lead salt and a soluble aluminum salt; The layered molybdenum disulfide is synthesized by a hydrothermal method; a molybdenum source and a sulfur source are mixed with a second solvent in a stoichiometric ratio, and the obtained precipitate is vacuum dried to obtain the layered molybdenum disulfide; the molybdenum source comprises ammonium molybdate; the sulfur source comprises thiocyanic acid and / or sodium thiosulfate; The obtained lead-aluminum layered double hydroxide is mixed with a silane coupling agent and a first solvent to obtain an intermediate composite; the silane coupling agent comprises one or more of vinyltriethoxysilane, vinyltrimethoxysilane or vinyltris(β-methoxyethoxy)silane; The obtained intermediate composite is mixed with the obtained layered molybdenum disulfide to obtain a composite crystal seed for recovering lead ions in wastewater; the composite crystal seed comprises the lead-aluminum layered double hydroxide and the layered molybdenum disulfide loaded on the surface of the lead-aluminum layered double hydroxide.

2. The production method according to claim 1, characterized by, The concentration of Pb in the mixed metal salt solution is 4-8 mol / L; The concentration of Al in the mixed metal salt solution is 1.5-5 mol / L.

3. The preparation method according to claim 1, characterized in that, The alkaline solution comprises sodium carbonate and / or sodium hydroxide; The concentration of the sodium carbonate in the alkaline solution is 0.4-1.6 mol / L; The concentration of the sodium hydroxide in the alkaline solution is 1-3.5 mol / L; The volume ratio of the mixed metal salt solution to the alkaline solution is 1:(1-5).

4. The preparation method according to any one of claims 1 to 3, wherein The reaction temperature for preparing the lead-aluminum layered double hydroxide by the coprecipitation method is 30-60°C; The reaction time for preparing the lead-aluminum layered double hydroxide by the coprecipitation method is 30-120 min.

5. The preparation method according to any one of claims 1 to 3, wherein The second solvent comprises water; The reaction temperature for synthesizing the layered molybdenum disulfide by the hydrothermal method is 150-170°C; The reaction time for synthesizing the layered molybdenum disulfide by the hydrothermal method is 8-10 h; The reaction for synthesizing the layered molybdenum disulfide by the hydrothermal method is carried out in a protective atmosphere; The reaction pressure for synthesizing the layered molybdenum disulfide by the hydrothermal method is 0.02-3 GPa; The temperature for vacuum drying is 50-80°C.

6. The preparation method according to any one of claims 1 to 3, wherein The first solvent comprises water; The mass ratio of the lead-aluminum layered double hydroxide to the silane coupling agent is 1:(0.04-0.4); The reaction time of the lead-aluminum layered double hydroxide with the silane coupling agent is 3-12 h; The reaction temperature of the lead-aluminum layered double hydroxide with the silane coupling agent is 10-45°C.

7. The production method according to any one of claims 1 to 3, characterized by, The mass ratio of the intermediate composite to the molybdenum disulfide is 1:(0.1-0.6); The reaction temperature of the intermediate composite with the molybdenum disulfide is 25-55°C; The reaction time of the intermediate compound with the molybdenum disulfide is 30-150 min.

8. The composite seed crystal for recovering lead ions in waste water, prepared by the production method according to any one of claims 1 to 7, characterized by, The composite seed comprises lead-aluminum layered double hydroxide and layered molybdenum disulfide loaded on the surface of the lead-aluminum layered double hydroxide.

9. The composite seed crystal of claim 8, wherein, In the composite seed, the mass ratio of the lead-aluminum layered double hydroxide to the layered molybdenum disulfide is 1:(0.15-0.6).

10. The composite seed crystal of claim 8 or 9, wherein, In the lead-aluminum layered double hydroxide, the molar ratio of lead to aluminum is (4-8):(1.5-5).

11. A process for the prilling of a nuclear salt, characterized in that, In the core crystal granulation and salt separation process, the composite seed prepared by the preparation method of any one of claims 1-7 or the composite seed of any one of claims 8-10 is used to treat lead-containing wastewater; The metal ions in the lead-containing wastewater further include one or more of cobalt, zinc, cadmium or nickel.

12. The core granulation, prilling, and salting process of claim 11, wherein, The core crystal granulation and salt separation process comprises the following steps: (1) filling the core crystal granulation reactor with the composite seed; (2) introducing lead-containing wastewater and a precipitant into the core crystal granulation reactor respectively, so that the composite seed is in a fluidized state and reacts; The regenerated water obtained after the reaction flows out from the upper end of the core crystal granulation reactor, and the granulation body obtained after the reaction is discharged from the lower end of the core crystal granulation reactor.

13. The core crystal granulation and salt separation process according to claim 12, wherein the filling height of the composite seed in step (1) is 15-25% of the height of the core crystal granulation reactor; The precipitant in step (2) comprises sodium carbonate solution and / or sodium hydroxide solution; The concentration of the precipitant in step (2) is in the range of (0.4-0.8): 1 with respect to the concentration of lead ions in the lead-containing wastewater, and The concentration unit is mg / L; The flow rate ratio of the precipitant to the lead-containing wastewater is 1:(15-20), wherein the flow rate unit is L / h; The reaction time in step (2) is 1-10 min.

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