Method for purifying sewage containing heavy metal ions through hydration-adsorption coupling

Abstract

The invention discloses a method for purifying sewage containing heavy metal ions through hydration-adsorption coupling. The method comprises the following steps that a reaction container is taken, a circumferential partition component with fluid permeability is arranged in the reaction container, and the circumferential partition component extends along the central axis of the container and divides the interior of the reaction container into an inner area and an outer area; filling the outer area with an adsorbent, adding to-be-treated sewage containing heavy metal ions into the area containing the adsorbent, controlling environmental conditions, and introducing guest molecules capable of forming hydrates into the other area for hydration reaction; and collecting a solid hydrate generated by the hydration reaction, and decomposing the solid hydrate to obtain a purified water sample. According to the scheme, the adsorption effect of the adsorbent and the'salt elimination 'effect in the hydration process are cooperated to achieve a coupling effect, so that the heavy metal removal effect is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal ion removal, and in particular to a method for purifying sewage containing heavy metal ions by hydration-adsorption coupling. Background Art

[0002] Heavy metals are natural components of the earth's crust and are widely present in the lithosphere and hydrosphere. 2+ )、Zn ion(Zn 2+ ), chromium (III / VI) ions, nickel ions (Ni 2+ ), cadmium ions (Cd 2+ ) and other heavy metal elements, which play an irreplaceable role in processes such as electroplating, metallurgy, and battery manufacturing. However, heavy metal pollutants have significant bioaccumulation and environmental persistence - they can form toxic enrichment in organisms through the biomagnification effect of the food chain, and most heavy metal ions are difficult to decay through natural degradation processes, ultimately endangering human health and destroying the balance of the ecosystem through the ecological chain.

[0003] Heavy metal ions are difficult to remove due to their low concentration. Low-concentration heavy metal ions are sparsely distributed in the solution, and the probability of contact with the adsorbent or membrane material is significantly reduced, resulting in insufficient driving force for processes such as adsorption and ion exchange. Therefore, the development of efficient heavy metal deep removal technology is of great significance to achieving water environment safety.

[0004] In the existing technology system, chemical precipitation achieves solid-liquid separation by generating metal hydroxide or sulfide precipitation, but it has defects such as large sludge output and low metal recovery rate; electrochemical method relies on power input and has high equipment maintenance costs; although ion exchange method has selectivity advantages, the resin regeneration cycle limits its engineering applicability; membrane separation technology faces the dual challenges of membrane pollution and operating energy consumption. In contrast, adsorption has become the most widely used heavy metal removal technology due to its operational flexibility, process compatibility and cost advantages of commercial adsorbents.

[0005] However, the large-scale application of the adsorption method still faces a key bottleneck: limited by the saturation effect of adsorption sites, the adsorption capacity of the adsorbent in actual application is significantly different from the theoretical value. Although the development of new adsorbent materials has breakthrough potential in theory, technical and economic limitations such as complex material synthesis process and poor stability of large-scale preparation make it difficult to meet engineering needs in the short term. Therefore, within the framework of the existing adsorbent system, improving purification efficiency by optimizing mass transfer efficiency and other strategies has become a more feasible technical path at this stage.

[0006] Hydrates are solid cage-like substances formed by guest molecules and host water molecules under low temperature and high pressure. Guest molecules include gas molecules such as methane, ethane, and carbon dioxide, as well as liquid molecules such as tetrahydrofuran and cyclopentane. The treatment of heavy metals by the hydrate method is a new technology for treating heavy metals proposed in recent years. The treatment of heavy metals by the hydrate method utilizes the "salt exclusion effect" during the formation of hydrates to exclude heavy metals outside the hydrates, thereby obtaining relatively pure water and achieving the purpose of heavy metal treatment. The hydrate method can theoretically completely remove heavy metals, but due to reasons such as the adhesion of heavy metal solutions, the efficiency of heavy metal removal needs to be further improved, and it also requires the assistance of other methods. Patent application document CN108996767A discloses a method for removing metal ions by hydration-adsorption. This method decomposes the hydrate after circulating the aqueous solution of hydrated metal ions through hydration-adsorption or adsorption-hydration at least once, thereby obtaining a purified aqueous solution. It combines the hydration and adsorption effects and realizes the removal of metal ions through the generation and decomposition of hydrates. The metal ions are enriched in the liquid phase during the hydration process, thereby improving the adsorption efficiency of the subsequent adsorbent and solving the shortcomings of the single method for removing metal ions to a certain extent. However, this method has relatively cumbersome operation steps and requires multiple steps such as hydration, adsorption cycle, and rinsing to obtain a purified solution. Further, this method also has the following technical bottlenecks: The reaction system needs to maintain a stirring state throughout the process to ensure mass transfer efficiency, resulting in a significant increase in power consumption; especially when using gaseous guest molecules to enhance mass transfer, the system needs to be equipped with a high-pressure sealed stirring kettle, which poses higher requirements for the pressure-bearing performance and dynamic sealing technology of the equipment. The dual requirements of airtightness guarantee and continuous mechanical stirring significantly increase the manufacturing cost and operation and maintenance complexity of special equipment and become the key restrictive factors for the industrial application of this process.

[0007] Therefore, it is of great significance to develop a new purification method. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling, which has simple operation and significantly improves the efficiency of removing heavy metal ions by the adsorption method at low cost.

[0009] According to one aspect of the present invention, a method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling is provided, including the following steps: Take a reaction vessel, and a circumferential partition member with fluid permeability is arranged inside the reaction vessel. The circumferential partition member extends along the central axis of the vessel and divides the interior of the reaction vessel into an inner region and an outer region; Fill the adsorbent in the external region, add the heavy metal ion-containing sewage to be treated into the region containing the adsorbent, control the environmental conditions, and introduce the guest molecules capable of forming hydrates into another region for the hydration reaction; collect the solid hydrates generated by the hydration reaction, and decompose the solid hydrates to obtain the purified water sample. Wherein, the adsorbent includes at least one of solid or gel porous adsorbent materials, and the circumferential partition member allows the reaction medium to pass through but restricts the migration of the adsorbent.

[0010] The method for purifying heavy metal-containing sewage by hydration-adsorption coupling according to the embodiment of the present invention has at least the following beneficial effects: The solution of the present invention couples the hydration and adsorption processes. When the hydrate is formed, it will be pressed into another region through the circumferential partition member, which is more conducive to the removal of heavy metals by the hydrate method; at the same time, the adsorbent firmly locks the adsorbed heavy metals to the adsorbent, preventing too many heavy metals from being carried out by the formed hydrates into the cylindrical cavity. Through the synergistic effect of the adsorption of the adsorbent and the "salt removal" effect of the hydration process, a coupling effect is achieved, thereby significantly improving the heavy metal removal effect. Structures (which can be through-hole structures, etc.) that allow the reaction medium to pass through but restrict the migration of the adsorbent are provided on the circumferential partition member. The existence of these structures and the porous structures in the adsorbent (and the gaps between solid or gel adsorbent particles) greatly increase the nucleation interface and improve the mass transfer efficiency. At the same time, these structures can also form a continuous mass transfer channel, allowing the guest molecules to pass through continuously, avoiding the situation where the hydration process cannot continue due to the coverage of the surface hydrate, or the need for stirring to improve the mass transfer efficiency and achieve a continuous hydration-adsorption coupling process. When the hydrate is in-situ generated on the surface of the member, the unoccupied fluid channels and the porous structures of the adsorbent (and the gaps between solid or gel adsorbent particles) can still maintain the transmission of the guest molecules, ensuring the timely replenishment of liquid water and guest molecules to the reaction interface, thereby breaking through the mass transfer attenuation bottleneck caused by the coverage of the hydrate surface layer in traditional reactors and the limitation that continuous water purification can only be achieved through continuous stirring.

[0011] According to some embodiments of the present invention, the reaction medium includes guest molecules and water. The circumferential partition member is provided with a pore structure for fluid passage.

[0012] According to some embodiments of the present invention, the heavy metal ions include at least one of copper ions (Cu 2+ ), zinc ions (Zn 2+ ), chromium ions (Cr 2+ ), nickel ions (Ni 2+ ), or cadmium ions (Cd 2+ ). Copper ions (Cu 2+ ), zinc ions (Zn 2+ ), chromium ions (Cr 2+ ), nickel ions (Ni2+ ), cadmium ions (Cd 2+ ), are common heavy metal ions in sewage, and the same applies to other heavy metal ions.

[0013] According to some embodiments of the present invention, the guest molecules include gaseous guest molecules and / or liquid guest molecules.

[0014] According to some embodiments of the present invention, the guest molecules include at least one of methane, ethane, propane, carbon dioxide, tetrahydrofuran or cyclopentane.

[0015] According to some embodiments of the present invention, the guest molecules include gaseous guest molecules. Gaseous guest molecules exhibit significant advantages in the removal of heavy metal ions by the hydration method, including higher diffusion efficiency, stronger selectivity, lower energy consumption, wider application range and more precise structure control. These advantages make gaseous guest molecules superior to liquid molecules in terms of environmental protection, economy and technical feasibility, providing a more efficient solution for the treatment of heavy metal pollution.

[0016] According to some embodiments of the present invention, the guest molecules include a carbon dioxide and propane composition.

[0017] According to some embodiments of the present invention, the concentration of heavy metal ions in the heavy metal ion-containing sewage is 1 - 1000 mg / L. Due to the dual characteristics of trace-level concentration and high ecological toxicity (such as carcinogenicity, teratogenicity, bioaccumulation) of heavy metal ions, the purification process needs to break through the bottleneck of traditional metal ion treatment technologies, not only requiring deep removal of ultra-low concentrations, but also taking into account the stabilization control of the heavy metal forms during the treatment process to prevent secondary pollution or toxicity transformation. The solution of the present invention cleverly achieves up-to-standard discharge or resource recovery through multi-technology coupling (such as selective adsorption - hydration).

[0018] According to some embodiments of the present invention, the concentration of heavy metal ions in the heavy metal ion-containing sewage is 100 - 600 mg / L.

[0019] According to some embodiments of the present invention, the concentration of heavy metal ions in the heavy metal ion-containing sewage is 300 - 500 mg / L.

[0020] According to some embodiments of the present invention, the reaction vessel is a reaction kettle.

[0021] According to some embodiments of the present invention, the reaction kettle is a static kettle. Using a static reaction kettle eliminates the need for stirring, saving energy consumption. At the same time, the static reaction kettle also reduces the requirements for the device, significantly saving economic costs. It can be an atmospheric pressure kettle or a high-pressure reaction kettle. Gaseous guest molecules use a high-pressure reaction kettle, while liquid guest molecules use an atmospheric pressure kettle.

[0022] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -10°C to 20°C, such as -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C or 20°C, etc.

[0023] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 2°C to 10°C.

[0024] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -5°C to 20°C.

[0025] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 0°C to 20°C.

[0026] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 0°C to 1°C.

[0027] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -1°C to 1°C.

[0028] According to some embodiments of the present invention, the guest molecule is a gaseous guest molecule, and the environmental conditions include a pressure lower than the standard atmospheric pressure.

[0029] According to some embodiments of the present invention, the adsorbent includes a solid porous adsorbent material. Using the solid porous adsorbent material can better separate heavy metal ions in sewage from water.

[0030] According to some embodiments of the present invention, the adsorbent includes 3A molecular sieve. Other porous adsorbent materials can also be used.

[0031] According to some embodiments of the present invention, the method further includes a step of desorbing and recycling the adsorbent after adsorbing heavy metal ions. The adsorbent material can be recycled, further reducing costs. At the same time, after the hydrate decomposes, the guest molecules of the hydrate can also be recycled.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural view (top view) of the high-pressure reactor used in Examples 1 - 2 of the present invention; Figure 2 is a schematic structural view of the circumferential partition member used in Examples 1 - 2 of the present invention; Figure 3 It is a schematic structural diagram of the device adopted in Embodiments 1-2 of the present invention.

[0034] Description of the drawings: 1. High-pressure reactor; 101. Inner region; 102. Outer region; 11. Circumferential partition member; 1101. Side wall; 1102. Bottom; 12. Adsorbent; 13. High-pressure horizontal valve; 14. Temperature sensor; 15. Pressure signal transmitter; 2. Gas cylinder; 3. Vacuum pump; 4. Circulating temperature control system; 5. Computer. Detailed implementation manners

[0035] The following will clearly and completely describe the concept of the present invention and the technical effects produced in combination with the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention. The test methods used in the embodiments are all conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, are all reagents and materials that can be obtained from commercial channels. Unless otherwise specified, the same parameter values are taken in each embodiment. The following-described embodiments are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0036] In the description of the present invention, the description referring to terms such as "some embodiments" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0037] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0038] Embodiment 1 This example provides a method for purifying heavy metal ion-containing sewage by coupling hydration and adsorption. Specifically, it includes the following steps: Take a high-pressure reactor 1 as the reaction vessel, and the structure of the high-pressure reactor 1 is as shown in Figure 1 shown. A circumferential partition member 11 with an inner diameter smaller than that of the reactor is arranged in the high-pressure reactor 1 (its structure is as shown in Figure 2 shown, presenting a cylindrical mesh structure, with a hole structure (but the adsorbent cannot pass through) provided on its side wall 1101, an open top, and a closed bottom 1102), and the circumferential partition member 11 divides the high-pressure reactor 1 into an inner region 101 and an outer region 102. After wetting the adsorbent 3A molecular sieve with a 500 mg / L copper sulfate solution, it is filled in the outer region 102.

[0039] After sealing the high-pressure reactor and evacuating the vacuum (just exhausting the air), turn on the constant temperature water bath system to control the temperature of the reactor to 273.6 K. Introduce carbon dioxide to form hydrates. When the 3A molecular sieve is wetted with the copper sulfate solution, the adsorption of the 3A molecular sieve has already started to play a role in enriching heavy metals. When the hydrates are formed, the solid hydrates will be attracted to the cavity inside the mesh structure member. In this process, the heavy metals in the 3A molecular sieve are carried away by the hydrates, playing a good adsorption role, and at the same time, it also plays a role in extruding the hydrates out of the mesh structure member, achieving synergy, that is, the coupling effect. Decompose and collect the solid hydrates and measure them. The removal efficiency of copper sulfate can reach 89.9%.

[0040] The above process is realized by a device as shown in Figure 3 shown. Specifically, the device includes the following structures: a high-pressure reactor (autoclave) 1, a gas cylinder 2, a vacuum pump 3, a circulating temperature control system 4, and a computer 5. A circumferential partition 11 is arranged in the high-pressure reactor 1, and the circumferential partition 11 divides the inside of the high-pressure reactor into an inner region and an outer region, and the adsorbent 12 is filled in the outer region. The circulating temperature control system 4 is used for temperature control. The high-pressure reactor 1 is located in the ethylene glycol-water mixed liquid circulating temperature control tank of the circulating temperature control system. High-pressure horizontal valves 13, a temperature sensor 14, and pressure transmitters 15 are provided on the high-pressure reactor 1. Among them, the high-pressure horizontal valve is connected to the vacuum pump 3, and both the temperature sensor 14 and the pressure transmitter 15 are communicatively connected to the computer 5. The gas cylinder 2 is loaded with carbon dioxide, and the gas cylinder 2 is connected to the high-pressure reactor 1, and a control valve is provided on the connecting pipeline.

[0041] Example 2 This example provides a method for purifying heavy metal ion-containing sewage by coupling hydration and adsorption. Specifically, it includes the following steps: Take a high-pressure reactor 1 as the reaction vessel, and the structure of the high-pressure reactor 1 is as shown in Figure 1 shown. Inside the high-pressure reactor 1, a circumferential partition member 11 with an inner diameter smaller than that of the reactor is provided (its structure is as shown in Figure 2 shown, presenting a cylindrical net structure, with a hole structure (through which the adsorbent cannot pass) provided on its side wall 1101, an open top, and a closed bottom 1102), and the circumferential partition member 11 divides the high-pressure reactor 1 into an inner region 101 and an outer region 102. After wetting the adsorbent 3A molecular sieve with a 300 mg / L copper sulfate solution, it is filled into the outer region 102.

[0042] After sealing the high-pressure reactor, evacuate it, and turn on the constant temperature water bath system to control the temperature of the reactor at 273.6 K. Introduce carbon dioxide to form hydrates. The copper sulfate solution passes through the 3A molecular sieve, and the adsorption of the 3A molecular sieve has played a role in enriching heavy metals. When the hydrates are formed, the solid hydrates will be attracted into the cavity inside the net structure member. In this process, the heavy metals in the 3A molecular sieve are carried away by the hydrates, playing a good adsorption role, and at the same time, it also plays a role in extruding the hydrates out of the net structure member, achieving synergy, that is, the coupling effect. Decompose and collect the solid hydrates and measure them, and the removal efficiency of copper sulfate can reach 89%.

[0043] This process is also realized by using the device as shown in Figure 3 shown.

[0044] Comparative Example 1 This example provides a method for adsorbing and purifying heavy metal ion-containing sewage. The difference from Example 2 is that the temperature is not controlled to the hydration condition and is under room temperature conditions. Measure the copper ion content in the purified water sample and calculate the removal efficiency of copper sulfate to be 79%.

[0045] It can be seen from the above examples and comparative examples that the solution of the present invention cleverly couples the adsorption of the adsorbent with the hydration process, constructs a synergistic strengthening system, and significantly improves the heavy metal removal effect. This coupling system effectively overcomes the technical bottlenecks of the insufficient actual adsorption capacity and unstable effect existing in a single technology, can achieve a breakthrough improvement in the heavy metal removal rate only through simple operations, does not require stirring, greatly saves energy consumption, and significantly reduces the process transformation cost without introducing new chemical reagents or complex reaction devices, and has significant technical and economic advantages.

[0046] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can also be made without departing from the purpose of the present invention.

Claims

1. A method for purifying heavy metal ion-containing sewage by coupling hydration and adsorption, characterized in that: The method includes the following steps: Take a reaction vessel, in which a circumferential dividing member with fluid permeability is arranged. The circumferential dividing member extends along the central axis of the vessel and divides the interior of the reaction vessel into an inner region and an outer region; Fill the adsorbent in the outer region, add the heavy metal ion-containing sewage to be treated into the region containing the adsorbent, control the environmental conditions and introduce guest molecules capable of forming hydrates into the other region for hydrate reaction; Collect the solid hydrates formed by the hydrate reaction, decompose the solid hydrates to obtain the purified water sample; Wherein, the adsorbent includes at least one of solid or gel porous adsorbent materials, and the circumferential dividing member allows the reaction medium to pass through but restricts the migration of the adsorbent.

2. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, wherein: The heavy metal ions include at least one of copper ions, zinc ions, chromium ions, nickel ions or cadmium ions.

3. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, wherein: The guest molecules include gaseous guest molecules and / or liquid guest molecules.

4. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, wherein: The guest molecules include at least one of methane, ethane, propane, carbon dioxide, tetrahydrofuran or cyclopentane.

5. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, characterized in that: The concentration of heavy metal ions in the heavy metal ion-containing sewage is 1 to 1000 mg / L.

6. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, characterized in that: The environmental conditions include a temperature of -10°C to 20°C.

7. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 6, wherein: The environmental conditions include a temperature of -1°C to 1°C.

8. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, characterized in that: The reaction vessel is a static reactor.

9. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to any one of claims 1 to 8, characterized in that: The guest molecules are gaseous guest molecules, and the environmental conditions include a pressure lower than the standard atmospheric pressure.

10. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to any one of claims 1 to 8, characterized in that: The adsorbent is a solid porous adsorbent material.

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