A method for purifying heavy metal ion-containing sewage by coupling hydration and adsorption

Abstract

The present invention discloses a method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling. The method comprises the following steps: taking a reaction vessel, wherein 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 internal region and an external region; filling an adsorbent in the external region, adding the heavy metal ion-containing sewage to be treated into the region containing the adsorbent, controlling the environmental conditions and introducing a guest molecule capable of forming a hydrate into the other region for a hydration reaction; collecting the solid hydrate generated by the hydration reaction, and decomposing the solid hydrate to obtain a purified water sample. The solution of the present invention synergistically combines the adsorption effect of the adsorbent and the "salt removal" effect of the hydration process to achieve a coupling effect, thereby significantly improving the heavy metal removal effect.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal ion removal, and particularly relates to a method for coupling hydration and adsorption to purify heavy metal ion-containing sewage. Background Art

[0002] Heavy metals, as natural components of the earth's crust, are widely present in the lithosphere and hydrosphere systems. In modern industrial systems and the people's livelihood fields, there is a rigid demand for heavy metal elements such as copper ions (Cu 2+ ), zinc ions (Zn 2+ ), chromium (Ⅲ / Ⅵ) ions, nickel ions (Ni 2+ ), cadmium ions (Cd 2+ ), etc. These elements play an irreplaceable role in processes such as electroplating, metallurgy, and battery manufacturing. However, heavy metal pollutants have significant bioaccumulation and environmental persistence - their toxic enrichment can form in organisms through the biomagnification effect of the food chain, and most heavy metal ions are difficult to achieve concentration attenuation through natural degradation processes, ultimately endangering human health and disrupting 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 contact probability with adsorbents or membrane materials 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 for achieving water environment safety.

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

[0005] However, the large-scale application of the adsorption method still faces key bottlenecks: limited by the adsorption site saturation effect, there is a significant difference between the adsorption capacity of the adsorbent in the actual application process and the theoretical value. Although the development of new adsorption materials has potential breakthroughs in theory, technical and economic limitations such as complex material synthesis processes and poor stability in large-scale preparation make it difficult to meet the engineering requirements in the short term. Therefore, within the framework of the existing adsorbent system, optimizing strategies such as mass transfer efficiency to improve purification efficiency has become a more feasible technical path at the present 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. In theory, the hydrate method can completely remove heavy metals. However, 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 involves subjecting an aqueous solution of hydrated metal ions to at least one cycle of hydration-adsorption or adsorption-hydration, and then decomposing the hydrate to obtain a purified aqueous solution. It combines the hydration and adsorption effects, and realizes the removal of metal ions through the formation and decomposition of hydrates. The metal ions are enriched in the liquid phase during the hydration process, thereby enhancing the adsorption efficiency of the subsequent adsorbent, and to a certain extent solving the shortcomings of the single method for removing metal ions. However, this method has relatively cumbersome operating steps, and it 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, becoming the key restrictive factor 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 proposes a method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling, which is simple to operate 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 proposed, 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;

[0010] Fill the adsorbent in the external region, add the heavy metal ion-containing sewage to be treated to the region containing the adsorbent, control the environmental conditions, and introduce guest molecules capable of forming hydrates into another region for a hydration reaction; collect the solid hydrates generated by the hydration reaction, and decompose the solid hydrates to obtain the purified water sample.

[0011] Among them, 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.

[0012] 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 synergy of the adsorption effect of the adsorbent and the "salt excretion" effect of the hydration process, a coupling effect is achieved, thereby significantly improving the heavy metal removal effect. Structures that allow the reaction medium to pass through but restrict the migration of the adsorbent (which can be through-hole structures, etc.) 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 inability to continue the hydration process due to the coverage of the surface hydrates, 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 guest molecules, ensuring the timely replenishment of liquid water and guest molecules to the reaction interface, thus breaking through the mass transfer attenuation bottleneck caused by the surface coverage of hydrates in traditional reactors and the limitation of continuous water purification that requires continuous stirring.

[0013] 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.

[0014] 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 (Ni 2+ ), cadmium ions (Cd 2+ ), which are common heavy metal ions in sewage, and are also applicable to other heavy metal ions.

[0015] According to some embodiments of the present invention, the guest molecules include gaseous guest molecules and / or liquid guest molecules.

[0016] According to some embodiments of the present invention, the guest molecules include at least one of methane, ethane, propane, carbon dioxide, tetrahydrofuran or cyclopentane.

[0017] 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 finer 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.

[0018] According to some embodiments of the present invention, the guest molecules include a carbon dioxide and propane composition.

[0019] 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 form during the treatment process to prevent secondary pollution or toxicity transformation. The solution of the present invention ingeniously achieves up-to-standard discharge or resource recovery through multi-technology coupling (such as selective adsorption - hydration).

[0020] 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.

[0021] 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.

[0022] According to some embodiments of the present invention, the reaction vessel is a reaction kettle.

[0023] 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, greatly saving economic costs. It can be an atmospheric pressure kettle or a high-pressure reaction kettle. For gaseous guest molecules, a high-pressure reaction kettle is used, while for liquid guest molecules, an atmospheric pressure kettle is used.

[0024] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -10°C to 20°C. For example, it can be -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.

[0025] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 2°C to 10°C.

[0026] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -5°C to 20°C.

[0027] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 0°C to 20°C.

[0028] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from 0°C to 1°C.

[0029] According to some embodiments of the present invention, the environmental conditions include a temperature ranging from -1°C to 1°C.

[0030] 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.

[0031] According to some embodiments of the present invention, the adsorbent includes a solid porous adsorbent material. Using a solid porous adsorbent material can better separate heavy metal ions in sewage from water.

[0032] According to some embodiments of the present invention, the adsorbent includes 3A molecular sieve. Other porous adsorbent materials can also be used.

[0033] 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.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic structural diagram (top view) of the high-pressure reactor used in Examples 1 - 2 of the present invention;

[0036] Figure 2It is a schematic structural diagram of the circumferential separation member adopted in Embodiments 1-2 of the present invention;

[0037] Figure 3 It is a schematic structural diagram of the device adopted in Embodiments 1-2 of the present invention.

[0038] Description of the drawings: 1. High-pressure reactor; 101. Internal area; 102. External area;

[0039] 11. Circumferential separation member; 1101. Side wall; 1102. Bottom;

[0040] 12. Adsorbent;

[0041] 13. High-pressure horizontal valve;

[0042] 14. Temperature sensor;

[0043] 15. Pressure signal transmitter;

[0044] 2. Gas cylinder;

[0045] 3. Vacuum pump;

[0046] 4. Circulating temperature control system;

[0047] 5. Computer. Detailed implementation manners

[0048] The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the 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 embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention.

[0049] In the description of the present invention, the description referring to the terms "some embodiments" etc. 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 any one or more embodiments or examples in a suitable manner.

[0050] In the description of the present invention, if the first, second, etc. are described only for the purpose of distinguishing technical features, they should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or the sequence of the indicated technical features.

[0051] Example 1

[0052] 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 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 Figure 2 shown, presenting a cylindrical net structure, with a hole structure (but the adsorbent cannot pass through) for fluid penetration 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 internal area 101 and an external area 102. After wetting the adsorbent 3A molecular sieve with a 500 mg / L copper sulfate solution, it is filled into the external area 102.

[0053] After sealing the high-pressure reactor, evacuate it (just discharge the air), 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. 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 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. 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 conduct measurements, and the removal efficiency of copper sulfate can reach 89.9%.

[0054] The above process is carried out as Figure 3The device shown is implemented. Specifically, the device includes the following structures: an autoclave 1, a gas cylinder 2, a vacuum pump 3, a circulating temperature control system 4, and a computer 5. A circumferential partition member 11 is provided inside the autoclave 1. The circumferential partition member 11 divides the inside of the autoclave into an inner region and an outer region. An adsorbent 12 is filled in the outer region. The circulating temperature control system 4 is used for temperature control. The autoclave 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 autoclave 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 filled with carbon dioxide. The gas cylinder 2 is connected to the autoclave 1, and a control valve is provided on the connecting pipeline.

[0055] Example 2

[0056] This example provides a method for coupling hydration and adsorption to purify heavy metal ion-containing sewage. Specifically, it includes the following steps: Take an autoclave 1 as the reaction vessel. The structure of the autoclave 1 is as Figure 1 shown. A circumferential partition member 11 with an inner diameter smaller than that of the reaction vessel is provided inside the autoclave 1 (its structure is as Figure 2 shown, presenting a cylindrical mesh structure. Its side wall 1101 is provided with a pore structure through which fluid can penetrate (but the adsorbent cannot pass through). The top is open, and the bottom 1102 is closed). The circumferential partition member 11 divides the autoclave 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 in the outer region 102.

[0057] After sealing the autoclave, evacuate the vacuum, and turn on the constant temperature water bath system to control the temperature of the reaction vessel at 273.6 K. Introduce carbon dioxide to form a hydrate. The copper sulfate solution passes through the 3A molecular sieve, and the adsorption effect of the 3A molecular sieve has played a role in enriching heavy metals. When the hydrate forms, the solid hydrate 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 hydrate, playing a good adsorption role. At the same time, it also plays a role in extruding the hydrate out of the mesh structure member, achieving synergy, that is, the coupling effect. Decompose and collect the solid hydrate and measure it. The removal efficiency of copper sulfate can reach 89%.

[0058] This process is also implemented using the device as Figure 3 shown.

[0059] Comparative Example 1

[0060] This example provides a method for adsorptive purification of heavy metal ion-containing sewage. The difference from Example 2 is that the temperature is not controlled to the hydration condition and is at room temperature. The copper ion content in the purified water sample is measured, and the removal efficiency of copper sulfate is calculated to be 79%.

[0061] It can be seen from the above examples and comparative examples that the solution of the present invention cleverly couples the adsorption effect of the adsorbent with the hydration process to construct a synergistic enhancement system, significantly improving the heavy metal removal effect. This coupling system effectively overcomes the technical bottlenecks of the actual insufficient adsorption capacity and unstable effect existing in a single technology. It can achieve a breakthrough improvement in the heavy metal removal rate with only simple operations, without stirring, greatly saving energy consumption. Without introducing new chemical reagents or complex reaction devices, the process transformation cost is significantly reduced, having significant technical and economic advantages.

[0062] The above has made a detailed description of the embodiments of the present invention, 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 be made without departing from the gist of the present invention.

Claims

1. A method for purifying heavy metal ion-containing sewage by coupling hydration and adsorption, characterized in that: It 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 outer region with an adsorbent, add the heavy metal ion-containing sewage to be treated into the region containing the adsorbent, control the environmental conditions and introduce a guest molecule capable of forming a hydrate into the other region for a hydration reaction; Collect the solid hydrate generated by the hydration reaction, decompose the solid hydrate to obtain a purified water sample; Wherein, the adsorbent includes at least one of a solid or gel porous adsorbent material, 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, characterized in that: 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, characterized in that: The guest molecule includes a gaseous guest molecule and / or a liquid guest molecule.

4. The method for purifying heavy metal ion-containing sewage by hydration-adsorption coupling according to claim 1, wherein: The guest molecule includes 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, wherein: 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, wherein: The reaction vessel is a static reaction kettle.

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 molecule is a gaseous guest molecule, 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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