Nanosilver composite adsorbent for processing iodine-containing waste water and method of manufacturing the same

Abstract

A nano-silver composite adsorbent for treating iodine-containing wastewater and its preparation method are disclosed. As an adsorbent for treating polluted and radioactive iodine-containing wastewater, the nano-silver composite adsorbent is prepared using a hydrothermal method, comprising nano-scale silver linear powder and a surface-modified support substrate. It includes a support substrate with high surface area and adsorption efficiency, and a silver-containing adsorbent material coated on the support substrate. The silver-containing adsorbent material is made from nano-scale silver linear powder and is a nano-composite functional iodine-removing adsorbent material for adsorbing and removing iodide ions from wastewater. This method offers a simple adsorption process for iodide ions and has significant advantages for extracting iodide ions from seawater, thereby improving the removal efficiency of pollutants in wastewater and meeting discharge standards.

Description

Technical Field

[0001] This invention relates to a nano-silver composite adsorbent for treating iodine-containing wastewater and its preparation. The method of preparation, particularly, relates to a nano-silver composite adsorbent composed of nano-scale silver wire-shaped powder prepared by hydrothermal method and a surface-modified support substrate, especially a material that can adsorb iodine ions, has significant advantages in extracting iodine ions from seawater, and thus improves the removal efficiency of pollutants in wastewater. Prior Technology

[0002] Countries around the world are at a critical juncture in their energy transition, working towards achieving net-zero emissions goals. Zero-carbon energy: The International Energy Agency (IEA) believes that nuclear energy can accelerate the global decarbonization of electricity, helping to reduce dependence on fossil fuels during the transition and strengthening the security of energy transition systems by coordinating with renewable energy sources. Taiwan lacks its own energy resources, relying on imports for over 98% of its energy, and has a high dependence on fossil fuels, thus facing carbon emission issues as well. Taiwan is actively transitioning its energy sector, currently favoring a nuclear-free homeland in its use of nuclear energy. However, due to nuclear power safety concerns, subsequent processing procedures are necessary. Therefore, developing key technologies for nuclear power plant decommissioning and nuclear waste treatment, and establishing independent nuclear back-end industry technology capabilities, is also an important government policy.

[0003] According to statistics from 2005, nuclear power plants worldwide accounted for approximately [a certain percentage] of total electricity generation. With nuclear energy accounting for 16% of the world's total energy consumption, it has become one of the world's major energy sources. However, nuclear power plant leaks, caused by unforeseen disasters, have made people realize that there are still safety concerns regarding the application of nuclear energy. Besides nuclear leaks, the large amounts of radioactive wastewater discharged during normal operation of nuclear power plants also contain significant amounts of radioactive nuclides. If not properly handled, these radioactive materials will cause enormous pollution damage to the ecology, environment, and human health. Therefore, the safe handling and disposal of nuclear pollution has become a global challenge. In recent decades, scientists from various countries have been deeply concerned about this issue, hoping to find solutions to remove or fix these radioactive nuclides.

[0004] In light of the experience gained from the Fukushima nuclear power plant accident in Japan, the radioactive materials generated by the accident that need to be dealt with... The contaminated water, due to the mixing of seawater and groundwater, has a complex composition and a large volume. The required radioactive wastewater treatment procedures and systems differ in scale from those used in routine wastewater treatment at nuclear power plants and facilities, and the material requirements for the purification process are also significantly greater. Taiwan should learn from the experience gained in handling this incident and develop key technologies for radioactive wastewater treatment systems to prepare for similar accidents involving reactor cores or used nuclear fuel storage.

[0005] During nuclear fuel reprocessing, radioactive materials such as waste gas, wastewater, and waste residue are produced. If leaked or released into the environment, soluble radioactive nuclides can easily enter water samples without proper handling, posing a potential risk of radioactive contamination. Although radioactive materials decay naturally over time, reducing their specific activity, their cumulative effects on marine organisms cannot be ignored.

[0006] Radioactive nuclei dissolved in water can be absorbed by microorganisms, algae, and plankton. Radioactive nuclei are absorbed by organisms, plants, or crops, and gradually accumulate and concentrate through layers of the food chain. When radioactive nuclei accumulate in the human body beyond a certain concentration after passing through water, they can severely affect normal metabolism and lead to various serious diseases.

[0007] According to relevant standards and regulations of the International Atomic Energy Agency and the former State Environmental Protection Administration, radioactivity... Wastewater is classified into the following three levels: Level 1: Low-level radioactive wastewater (activity < 3.7*10 6 Bq / L); Second stage: Intermediate-level wastewater (activity between 3.7*10⁶ and 3.7*10¹⁰ Bq / L); and Level 3: High-level radioactive wastewater (activity > 3.7*10 10 Bq / L).

[0008] The treatment and disposal of radioactive wastewater generally follows two basic principles: one is... Low-level radioactive wastewater is diluted and diffused before being discharged into the water body in accordance with discharge standards; The second approach involves concentrating and solidifying radioactive wastewater, isolating it from the human environment for a long period, and then allowing it to decay naturally. This second principle has a wider applicability, suitable for high, medium, and low-level radioactive wastewater. The goal of radioactive wastewater treatment is to obtain the highest possible Decontamination Factor (DF) and Concentration Factor (CF). DF refers to the ratio of the radioactive concentration to the quality concentration in the influent and effluent; CF refers to the ratio of the original volume of the influent radioactive wastewater to the volume of the concentrated radioactive products after treatment. Higher DF and CF indicate better radioactive removal from the water sample and a smaller volume of concentrated waste, thus facilitating the solidification and isolation of the concentrated radioactive waste. To date, various physical, chemical, biological, and membrane separation technologies have been developed and applied to the treatment of radioactive wastewater. Radioactive wastewater treatment technologies each have their own characteristics. Among them, (1) chemical co-precipitation involves adding chemicals to the wastewater to remove nuclei and fine suspended particles. The nuclei are concentrated in the sludge and then separated by physical means (such as filtration). It is suitable for treating wastewater with low activity, alkalinity and high concentration of salt. The method is simple and has low setup and operation costs. (2) Ion exchange resins are suitable for treating wastewater with extremely low concentrations, such as adsorbents. (3) Membrane treatment includes reverse osmosis and membrane distillation. Its advantages are that there is no temperature change or phase change and low energy consumption. However, its concentrate must be further concentrated by evaporation. (4) Evaporation concentration has a good effect on removing pollutants from high-concentration inorganic wastewater. It has the highest pollutant removal factor among current wastewater treatment methods. The distillate after treatment can be recycled and reused, and the concentrated wastewater will be further solidified.

[0009] Generally, the radioactive nuclides that may be present in nuclear wastewater mainly include iodine-125. Radioactive nuclides released in nuclear leaks typically include I-125, I-129, I-131, Cs-134, Cs-137, Ra-226, and Ra-228. I-129, I-131, and Cs-137 are the most common radioactive nuclides released during such accidents. Compared to other radioactive nuclides, these are more easily absorbed by the human body and pose a significant risk. Therefore, removing radioactive iodine and cesium is a crucial element in the treatment of radioactive wastewater.

[0010] There are approximately 26 isotopes of iodine, most of which are artificial radioactive isotopes, among which... The more important isotopes in natural and nuclear facilities are I-125, I-129, and I-131, as shown in Table 2 below. The types and characteristics of isotopic radiation from iodine. Table 2 isotope Radiation type half life Specific activity (Bq / g) I 123 gamma radiation 13.2 h 7.1 x 10^16 I 125 gamma radiation 58.8 d 6.6 x 10^14 I 129 γ radiation and β radiation 1.57x10 7y 6.5x10 6 I 131 γ radiation and β radiation 8.04 d 4.6x10 15

[0011] I-125 and I-129 are the main elements in radioactive wastewater, characterized by high radioactivity. The proliferation of fission products and the long half-life of radioactive iodine pose significant risks to human health and the environment. I-131, with its relatively short half-life, can be temporarily stored and allowed to decay naturally. I-129, however, is a long-half-life nuclear species and a major source of long-term radioactive iodine hazards; it cannot be removed through natural decay.

[0012] Currently, the main methods for removing iodine from water are ion exchange resin method and absorption method. Methods include adsorption. Ion exchange resins are suitable for capturing iodine from low-concentration wastewater, and the adsorbents have good selectivity. However, the adsorbents are easily affected by other impurities in the wastewater, and the operation process is relatively cumbersome. Liquid absorption is a widely used technology for iodine removal. Commonly used liquid absorption methods include sodium hydroxide washing, dissolution with mercuric nitrate (Hg(NO3)2) and nitric acid, nitric acid dissolution oxidation, electrolytic absorption with cobalt (Co3+) ion-containing nitric acid solution, and organosilicon solvent absorption. However, liquid absorption processes are relatively complex, and the iodine in the absorbent must ultimately be converted into a stable solid compound.

[0013] Adsorption methods possess advantages such as simple technology, large adsorption capacity, and high selectivity. Currently, adsorption has become the most competitive method. Adsorption removes radioactive iodine nuclides from water samples by adsorbing them onto the surface or within the pores of an adsorbent. Because it introduces fewer other chemicals into the water sample, it is a simpler and less polluting method, and therefore has wide applications. However, adsorption is susceptible to interference from other ions in the water, resulting in problems such as low adsorption capacity, frequent regeneration, and high treatment costs. Therefore, there is a need to develop more economical, easily prepared, conveniently stored, highly efficient, and highly selective adsorbent materials. Current research on adsorbent technologies mainly includes activated carbon adsorption, microporous exchange resin adsorption, silver exchange or silver-impregnated zeolite, silica gel, or alumina adsorption. Silver-impregnated adsorbents are widely used due to their good adsorption capacity for elemental iodine (I₂) and organic iodine (CH₃I), high adsorption capacity and efficiency, and the non-flammable nature of the adsorbent support. Supports typically have high surface area and are porous. Common examples include activated carbon (AC), γ-alumina (γ-Al₂O₃), silicon dioxide (SiO₂), cerium dioxide (CeO₂), magnesium oxide (MgO), titanium dioxide (TiO₂), zirconium dioxide (ZrO₂), MCM-41 composed of silicates and aluminates, cobalt tetroxide (Co₃O₄), lanthanum trioxide (La₂O₃), and zeolites. Different materials and morphologies can affect their metal loading and adsorption / desorption capabilities.

[0014] Activated carbon is a black carbonaceous substance, mainly composed of carbon (C), hydrogen (H), and oxygen (O). Or trace amounts of other elements, due to their low bulk density and large specific surface area, are often used as adsorbents. Activated carbon is generally considered to have a carbon crystalline structure similar to graphite, with strong cross-linking between its crystals forming its multi-dimensional porous structure. Activated carbon is chemically stable and can be used in a wide range of pH levels. Its diverse and abundant porosity and pore structure, high specific surface area, and surface functional groups give it high selectivity and high reactivity in catalysis. Due to the unsaturation of activated carbon atoms, they chemically combine with atoms and atomic groups other than carbon components, forming various surface functional groups. The type and number of surface functional groups of activated carbon determine its surface chemical properties, which in turn determine its surface adsorption characteristics. By changing the type and number of surface functional groups of activated carbon, its adsorption capacity for specific adsorbents can be improved. To achieve optimal adsorption, different adsorbents require different surface environmental conditions for activated carbon. Therefore, to meet the different application needs of activated carbon, pretreatment procedures are often performed to obtain the required surface environmental conditions. Iodide ions (I⁻) in solution can react with silver ions (Ag⁺), copper ions (Cu⁺), bismuth ions (Bi³⁺), lead ions (Pb²⁺), and mercury ions (Hg²⁺) to form insoluble compounds. However, Hg²⁺ and Pb²⁺ are themselves toxic. The secondary pollution it causes makes it unsuitable for direct application in water treatment; Ag-based adsorbent materials have poor adsorption properties. Its performance is excellent, and relevant literature has been published in the field of iodine removal.

[0015] Activated carbon possesses a high specific surface area, porous structure, and unique surface functional groups, making it suitable for various applications. Adsorption of radioactive iodide ions in water samples. In relevant literature, reference one (Sato et al.) used powdered activated carbon (PAC) as the adsorbent.

[0016] When the initial concentration of radioactive iodide ions in water is 40–50 µg / L, 1.0% PAC has a significant effect on… The adsorption efficiency of iodide ions is approximately 60%. Reference 2 (Hoskins et al.) utilized silver-impregnated granular activated carbon (Ag / GAC) to adsorb iodide ions from water. Compared to pure GAC (Granular Activated Carbon), the adsorption performance of iodide ions was significantly improved after silver impregnation. The adsorption principle is that silver ions on the surface of Ag / GAC first react with iodide ions to precipitate, and then the remaining iodide ions are adsorbed by GAC. At an initial iodide ion concentration of 8–1576 µmol / L, an Ag / GAC dosage of 1.0 g / L, a pH of 7–8, and a silver impregnation concentration of 1.05%, the iodide ion adsorption capacity was increased by approximately 97.3 µmol / L compared to GAC. Reference 3 (Choung et al.) utilized black carbon to adsorb radioactive iodide ions from water. When the iodide ion concentration is 10-106 µg / L, the addition of 5 g / L of black carbon under acidic conditions results in an adsorption capacity of 10 mg / g for iodide ions, which is more than 100 times that of iodate ions (IO3-).

[0017] Currently, there are related patents that disclose the use of a zeolite containing two types of zeolite (i.e., type X zeolite and type A zeolite). A method for treating waste gas containing iodine or organic iodine using silver-containing zeolite molded articles (zeolite) without binders. However, the silver in this invention tends to aggregate during its production process. Aggregated silver does not contribute to adsorption and leads to a reduction in the specific surface area of ​​the zeolite and pore blockage, thus significantly deteriorating the adhesion properties of the silver-containing zeolite. This problem becomes particularly pronounced when the zeolite is used in the form of molded articles. Furthermore, the zeolite molded articles described in this patent exhibit poor silver dispersibility.

[0018] Another related patent uses a granulated X-type zeolite for the adsorption of radioactive iodine. The agent, wherein the micropore size of type X zeolite is adjusted to replace the ion exchange sites of type X zeolite with the molecular size of hydrogen, and the silver content is greater than 36 wt% in the dry state; the particle size is 10x20 mesh; however, this The salt structure contained in the adsorbent is easily carried away and destroyed under superheated steam conditions at 150°C, leading to... Efficiency decreased.

[0019] Generally, the adsorption properties increase with increasing silver content. However, when carrying... When the silver content exceeds 50% by weight, silver aggregation becomes significant, with a large amount of metallic silver and silver clusters, especially metallic silver. Metallic silver not only clogs the pores of the zeolite but also easily detaches from zeolite molded products, resulting in zeolite molded products with low silver adsorption per unit weight. Furthermore, when the silver content exceeds 50% by weight, production costs become excessively high, thus limiting industrial applications.

[0020] Since the Fukushima nuclear power plant leak in Japan in 2011, related reports have continued to show... Radioactive iodine was detected in the surrounding air, water, and organisms such as fish. Iodine nuclides are highly mobile, making them one of the most difficult radionuclides to handle. However, research on the removal of radioactive iodine from water bodies is still limited, especially emergency treatment technologies for removing radioactive iodine nuclides from water. Therefore, it is necessary to prepare for potential future sudden and large-scale radioactive iodine pollution in water bodies. Thus, it is essential to develop an invention that can solve the problem of radioactive iodine pollution in water bodies and address the shortcomings of existing technologies. Summary of the Invention

[0021] The main objective of this invention is to overcome the aforementioned problems encountered in the prior art and to improve... A nano-silver composite adsorbent composed of nano-scale silver wire-shaped powder is provided, which has the effect of adsorbing iodide ions, and can also increase the adsorption and removal effect of iodide ions and increase the adsorption sites. It can be used as an adsorbent in wastewater treatment systems and improve the removal rate of radioactive nuclides. The nano-silver composite adsorbent and its preparation method are also provided.

[0022] Another objective of this invention is to provide a method for adsorption via extracted nano-silver composites. This agent removes iodine from iodine-containing wastewater, radioactive wastewater, or routine wastewater from nuclear power plants and facilities to meet discharge standards and ensure uncontaminated water samples. It utilizes nano-silver composite adsorbents for treating iodine-containing wastewater. Its production method.

[0023] Another object of the present invention is to provide a product manufactured using impregnation and hydrothermal methods. Nano-silver composite adsorbent for the treatment of iodine-containing wastewater and its preparation method.

[0024] To achieve the above objectives, this invention provides a nano-silver composite adsorbent, suitable for applications requiring specific nanomaterials. The iodine-containing wastewater containing pollution and radioactivity comprises a support substrate with high specific surface area and uniform dispersion, and a silver-containing adsorbent material coated on the support substrate to increase iodine adsorption or chelation; wherein the support substrate is modified and activated activated carbon (AC), or an organic or inorganic material with high specific surface area and uniform dispersion, and the silver-containing adsorbent material is composed of nano-scale silver linear powder, which is uniformly dispersed on the support substrate to form the nano-silver composite adsorbent.

[0025] In the above embodiments of the present invention, the BET of the support substrate (Brunauer-Emmett-Teller) Specific surface area of ​​at least 560 m² / g.

[0026] To achieve the above objectives, the present invention further relates to a nano-silver composite adsorbent for treating iodine-containing wastewater. The preparation method of the additive includes at least the following steps: Step 1: Immersing AC as a support substrate in an alkaline solution with a concentration between 0.2 and 2 N for activation and surface functional group enhancement pretreatment, immersing the support substrate uniformly in the alkaline solution for 12 to 16 hours, drying at low temperature, and then calcining at 85 to 125°C to prepare a modified and activated support substrate; Step 2: Dissolving 0.1 to 0.3 g of chloride salt and 1 to 10 g of high molecular weight polyvinylpyrrolidone (PVP) in an ethylene glycol solution by stirring at 100 to 150°C, adding 10 to 30 mL of silver-containing aqueous solution, and then hydrothermally reacting in an autoclave at 110 to 160°C for 2 to 6 hours, followed by washing and drying with water and ethanol to prepare nano-sized silver wire-like powder; and Step 3: Mixing 1 to 5 g of ethylene glycol with... The nano-sized silver linear powder (wt%) is used as the silver source. After stirring evenly to disperse the nano-sized silver linear powder in an ethylene glycol solution, the modified and activated support substrate is added, so that the nano-sized silver linear powder is impregnated on the modified and activated support substrate. After low-temperature drying, a silver-containing adsorbent is obtained, which is then calcined at 300~650°C in a hydrogen atmosphere to prepare a nano-silver composite adsorbent.

[0027] In the above embodiments of the present invention, the average length of the nano-scale silver wire-like powder is 500±20% nm, width is 50±20% nm.

[0028] In the above embodiments of the present invention, the alkaline solution is selected from sodium hydroxide aqueous solution, hydroxide... At least one of the group consisting of potassium aqueous solution and lithium hydroxide aqueous solution.

[0029] In the above embodiments of the present invention, the chloride salt is selected from sodium chloride and potassium chloride. At least one soluble salt in the group formed.

[0030] In the above embodiments of the present invention, the silver-containing aqueous solution is selected from silver nitrate, silver sulfate, and An aqueous solution containing at least one silver compound from the group consisting of silver acetate and silver chloride.

[0031] In the above embodiments of the present invention, the nano-silver composite adsorbent can be modified as needed. The composition ratio of the activated support substrate to the nanoscale silver wire-shaped powder.

[0032] In the above embodiments of the present invention, step one involves drying at a low temperature of 50-70°C for 1-3 days. After 8 hours, heat to 85-125°C at a rate of 3-5°C / min and calcine for 8-12 hours.

[0033] In the above embodiments of the present invention, step three involves drying at a low temperature of 100~140°C for 3 days. After ~5 hours, in the hydrogen atmosphere, the temperature is increased to 300~650°C at 3~5°C / min and calcined for 0.5~3.5 hours. Simple Explanation of the Diagram

[0034] Figure 1 is a schematic diagram of the structure of the nano-silver composite adsorbent of the present invention. Figure 2 is a schematic diagram of the manufacturing process of the nano-silver composite adsorbent of the present invention. Figure 3 shows the adsorption efficiency test of continuous iodine removal using the nano-silver composite adsorbent of this invention. Implementation

[0035] Please refer to Figures 1 through 3, which respectively illustrate the nano-silver composite adsorption of the present invention. The diagram shows the structure of the adsorbent, the manufacturing process of the nano-silver composite adsorbent of the present invention, and the test diagram of the continuous iodine removal adsorption efficiency of the nano-silver composite adsorbent of the present invention. As shown in the figure: This invention relates to a nano-silver composite adsorbent for treating iodine-containing wastewater and its preparation method. The proposed nano-silver composite adsorbent 1 is a nano-composite functional iodine removal adsorbent material composed of linear nano-silver materials, which has the effect of adsorbing iodine ions. It can also increase the iodine ion adsorption and removal effect and increase the adsorption sites. It can also be used as an adsorbent in wastewater treatment systems and improve the removal rate of radioactive nuclides. It is suitable for removing iodine from iodine-containing polluted wastewater, radioactive waste liquid, or routine wastewater from nuclear power plants and nuclear facilities to meet discharge standards and for use in pollution-free water samples. The nano-silver composite adsorbent 1 includes a support substrate 11 with high specific surface area and good dispersibility, and a silver-containing adsorbent material 12 coated on the support substrate 11 to increase iodine adsorption or chelation. It can effectively adsorb iodine ions (I-) in water and solve the problem of reducing radioactive pollutants in discharged wastewater. The composition ratio of the silver-containing adsorbent material 12 and the support substrate 11 can be adjusted as needed.

[0036] The aforementioned support substrate 11 is a modified and activated activated carbon. Carbon (AC), or organic or inorganic substances with high specific surface area and good dispersibility; and the silver-containing adsorbent 12 is composed of nano-scale silver wire-like powder, thereby uniformly dispersing it in the support substrate. The nano-silver composite adsorbent 1 is formed by the above-disclosed structure 11. The ratio of the silver-containing adsorbent material 12 to the support substrate 11 can be adjusted according to the needs to achieve various adsorption and dispersion ratios. In this embodiment, 2.24% has the best effect. Thus, the above-disclosed structure constitutes a novel nano-silver composite adsorbent 1 suitable for treating polluted and radioactive iodine-containing wastewater.

[0037] The above-described process for manufacturing nano-silver composite adsorbent 1, suitable for treating iodine-containing wastewater, is... Includes the following steps: Step 1 (s11): Using AC (acrylic acid) cleaned with deionized water to remove surface tar (hereinafter referred to as AC support substrate), 50 grams of AC support substrate are immersed in 100 mL of an alkaline solution with a concentration between 0.2 and 2 N for activation and pretreatment to increase surface functional groups. The AC support substrate is then uniformly immersed in the alkaline solution for 12-16 hours using ultrasonic vibration. After removing the AC support substrate and filtering out excess alkaline solution, it is dried at a low temperature of 50-70°C for 1-3 hours, and then calcined at 85-125°C for 8-12 hours at a rate of 3-5°C / min to prepare a... A modified and activated AC support substrate was formed. Step 2 s12: Mix 0.1~0.3 g of chloride salt with 1~10 g of high molecular weight polyvinylpyrrolidone Polyvinylpyrrolidone (PVP) was dissolved in ethylene glycol solution at 100-150°C with stirring. 10-30 mL of silver-containing aqueous solution was added dropwise. The mixture was then subjected to hydrothermal reaction at 110-160°C for 2-6 hours in an autoclave. After washing and drying with water and ethanol, nano-sized silver wire-like powder was prepared. Step 3 (s13): Using 1-5 wt% of the nano-scale silver wire-shaped powder mixed with ethylene glycol as the silver source, stir evenly to disperse the nano-scale silver wire-shaped powder in the ethylene glycol solution, then add the modified and activated AC support substrate, so that the nano-scale silver wire-shaped powder is impregnated on the modified and activated AC support substrate. After drying at a low temperature of 100-140°C for 3-5 hours, a silver-containing adsorbent is obtained. Then, in a hydrogen atmosphere, the temperature is increased to 300-650°C at 3-5°C / min for 0.5-3.5 hours to prepare a nano-silver composite adsorbent.

[0038] The above describes the nanomaterials obtained by the present invention through a simple hydrothermal method and impregnation method. Silver composite adsorbent 1 is suitable for adsorbing and removing iodine ions from iodine-containing radioactive waste liquid. Thus, the process disclosed above constitutes a novel method for preparing a highly efficient composite adsorbent with adsorption effect.

[0039] In one preferred embodiment of the present invention, the AC support substrate has good... Support substrate with high temperature resistance, conductivity, adsorption, corrosion resistance and high specific surface area.

[0040] In one preferred embodiment of the present invention, the AC support after modification and activation... The BET (Brunauer-Emmett-Teller) specific surface area of ​​the substrate is 560 m² / g or more, further optimized to 600 m² / g or more, and even more preferably 700 m² / g or more. This allows the adsorbent surface of the present invention to effectively contact the adsorbate, and gives the resulting molded article high adsorption characteristics, increasing the total silver ratio that silver ions can carry on the AC support substrate, thereby making silver more effectively adsorbed.

[0041] In one preferred embodiment of the present invention, the alkaline solution is selected from an aqueous sodium hydroxide solution. It is at least one of the group consisting of potassium hydroxide aqueous solution and lithium hydroxide aqueous solution. Sodium hydroxide, which is inexpensive, is preferred.

[0042] In one preferred embodiment of the present invention, the nano-scale silver wire-like powder has a flat surface. The average length is 500 nm and the width is 50 nm.

[0043] In one preferred embodiment of the present invention, the chloride salt is selected from sodium chloride, At least one soluble salt from the group consisting of potassium chloride.

[0044] In one preferred embodiment of the present invention, the silver-containing aqueous solution is selected from silver nitrate, An aqueous solution containing at least one silver compound from the group consisting of silver sulfate, silver acetate, and silver chloride. Silver nitrate, which is inexpensive, is preferred.

[0045] In one preferred embodiment of the present invention, the modified and activated support substrate and the The composition and ratio of nano-scale silver wire-like powder can be adjusted according to requirements for impregnation or carrying.

[0046] The following examples are merely illustrative to illustrate the details and meaning of the present invention, and are not intended to limit it. The scope of the patent application for this invention.

[0047] A preferred embodiment of the formulation of the nano-silver composite adsorbent of the present invention is to use it hydrothermally. An adsorbent composed of nano-sized silver wire-like powder synthesized by a certain method is used as an adsorbent material for removing iodine-containing radioactive waste liquid. The implementation steps are as follows: Step 1: Wash 50g of AC support substrate with deionized water to thoroughly remove surface tar and impurities. Then, immerse it in 100mL of 2N sodium hydroxide alkaline solution for 16 hours. After ultrasonic vibration to ensure the AC support substrate is evenly immersed in the alkaline solution, filter out excess alkaline solution from the AC support substrate by vacuuming. Dry it at a low temperature of 60°C for 2 hours, and then calcine it at 105°C for 12 hours to prepare a modified and activated AC support substrate. Step 2: Dissolve 0.3 g of sodium chloride and 10 g of PVP in ethylene glycol solution at 150°C. Add 30 mL of silver nitrate solution. The molar ratio of silver to sodium chloride is 1:1. The solution gradually turns milky white from clear to transparent. Then, perform hydrothermal reaction at 140°C for 2 hours in an autoclave. After washing and drying with water and ethanol, nano-scale silver linear powder with an average length of 500 nm is prepared. Step 3: Using 20 mL of ethylene glycol mixed with 1 g of nano-sized silver wire-shaped powder as the silver source, the mixture was stirred evenly to disperse the nano-sized silver wire-shaped powder in the ethylene glycol solution. Then, 19 g of modified and activated AC support substrate was added, so that the nano-sized silver wire-shaped powder was impregnated on the modified and activated AC support substrate. After drying at a low temperature of 120°C for 4 hours, a silver-containing adsorbent was obtained. Then, it was calcined at 600°C in a hydrogen atmosphere to prepare a nano-silver composite adsorbent.

[0048] This invention utilizes the nano-silver composite adsorbent prepared by the above-mentioned impregnation method and hydrothermal method to perform... Adsorption efficiency and decontamination factor testing of the adsorbent. The concentration of iodine-containing wastewater in general discharges, calculated through radioactivity conversion, is approximately 10.0 ppm. This invention uses solid KI dissolved in deionized water as simulated radioactive raw water. At 25°C, the initial concentration of iodine in the simulated solution was prepared to be 15.0 ppm. Furthermore, for the decontamination factor efficiency test, feed wastewater from the Nuclear Research Institute was used, with the activity concentration primarily based on samples taken on February 10, 2022. Two liters of a radioactive iodine-129 (I-129) solution (activity 600 Bq / L) were prepared for the decontamination factor test.

[0049] [Adsorbent Adsorption Performance Testing Procedure] Take 20.0 mL sample vials, add 0.2 g of nano-silver composite adsorbent and 10.0 mL of simulated iodine solution to each vial, mix, and ultrasonically shake for 12 hours. Let stand for 2 hours to allow activated carbon to precipitate. Extract the supernatant from the sample vials, filter through a 0.45 μm syringe filter, and then determine the iodide ion concentration in the filtrate using ICP. Repeat the experiment three times and take the average value. The iodide ion concentration was detected using ICP-OES. The standard solution for iodide ions was prepared using deionized water.

[0050] [Procedure for Determination of Pollutant Removal Factors] Take 20.0 mL sample vials, add 0.2 g of nano-silver composite adsorbent to each vial, and mix with 10.0 mL of I-129 solution (activity 600 Bq / L) prepared from wastewater from the Nuclear Research Institute. Shake at 140 rpm / min for 4 hours, then let stand for 1 hour to allow activated carbon to precipitate. Extract the supernatant from the sample vials, filter it through a 0.45 μm syringe filter, and analyze the activity after adsorption. The decontamination factor (DF) is calculated as follows: Decontamination factor (DF) = Initial activity / Final activity.

[0051] This invention uses a nano-silver composite adsorbent (Ag / InerAC) packed into a laboratory-grade column. Continuous adsorption tests were conducted with a fixed adsorbent loading of 20 cm³. KI solid dissolved in deionized water was used as a simulated radioactive wastewater. At room temperature (25°C), the initial concentration of iodide ions in the simulated wastewater solution was measured by ICP to be 15.96 ppm. As shown in Figure 3, this invention uses a nano-silver composite adsorbent for continuous iodine removal adsorption efficiency testing. At a fixed flow rate of approximately 4.2 L / d (liquid hourly space velocity, LSHV, 8.75 h⁻¹), the continuous iodine removal efficiency remained >99%.

[0052] The emission limit for I-129 is 8.3 Bq / L. Table 1 below shows the nano-silver composite adsorbent. Decontamination factor test. At a calcination temperature of 350°C, the nano-silver composite adsorbent pretreated with 0.2 N and impregnated with silver showed a residual viability of 1.04 Bq / L, with a calculated decontamination factor of approximately 574.65. The nano-silver composite adsorbent pretreated with 2 N showed a calculated decontamination factor of 690.84. The nano-silver composite adsorbent with the best decontamination factor was the one pretreated with 2 N at a calcination temperature of 600°C, with a residual viability of 0.795 Bq / L and a calculated decontamination factor of approximately 755. Table 1 Nano silver composite adsorbent silver configuration Survival DF Ag / 0.2N InerAC(350) silver particles 1.613 372 Ag / 0.2N InerAC(350) silver line 1.04 574.65 Ag / 2N InerAC(350) silver line 0.87 690.84 Ag / 0.2N InerAC(600) silver line 1.18 508.38 Ag / 2N InerAC(600) silver line 0.795 754.67

[0053] The nano-silver composite adsorbent prepared in this invention, after the above-mentioned actual tests, has the ability to remove... The effectiveness of the adsorption of iodine in wastewater verifies that the nano-silver composite adsorbent of this invention is suitable for removing iodine from water bodies present during normal operation and accident conditions of nuclear facilities.

[0054] The nano-silver composite adsorbent produced in this invention is a composite bifunctional catalyst that can effectively utilize... This technology addresses the issue of iodine removal and reduction in iodine content in wastewater. Furthermore, the composition and ratio of nano-scale silver wire-like powder and support substrate can be adjusted as needed. Its structure exhibits high specific surface area and porous properties. Therefore, compared with adsorbents produced by other methods, it can produce a more efficient iodine removal effect.

[0055] Therefore, this invention provides a method for reducing or removing iodine content in wastewater solutions, and the provided method is... The silver-nano composite adsorbent exhibits excellent performance and allows for easy control of the composition ratio of nano-scale silver linear powder and support substrate to achieve good efficiency. It also boasts good chemical stability and mechanical strength. The adsorption process for iodide ions is simple, as the silver and iodide ions are bonded together, eliminating the need for iodide ion oxidation. Furthermore, it is easily regenerated after adsorbing iodide ions, and its adsorption performance remains excellent after regeneration. This makes it a significant advantage for extracting iodide ions from brine.

[0056] In summary, this invention relates to a nano-silver composite adsorbent for treating iodine-containing wastewater and its... The manufacturing method can effectively improve the various shortcomings of conventional methods, and can remove radioactive iodine nuclides from water samples or during accidents in general nuclear power plants or facilities. It can effectively reduce the risk of wastewater discharge with radioactive iodine pollution and meet the discharge standards. As a result, the invention is more advanced, more practical and more in line with the needs of users. It has met the requirements for an invention patent application, and therefore a patent application is filed in accordance with the law.

[0057] However, the above description is merely a preferred embodiment of the present invention and should not be construed as limiting it. The scope of this invention; therefore, any simplifications made in accordance with the scope of the patent application and the contents of the invention specification are hereby excluded. All equivalent changes and modifications to the single element should still fall within the scope of this invention patent.

[0058] 1: Nano-silver composite adsorbent 11: Carrier base material 12: Silver-containing adsorbent materials s11~s13: Steps

Claims

1. A method for preparing a nano-silver composite adsorbent for treating iodine-containing wastewater, comprising at least the following steps: Step 1: Immersing AC as a support substrate in an alkaline solution with a concentration between 0.2 and 2 N for activation and pretreatment to increase surface functional groups, wherein the support substrate is uniformly immersed in the alkaline solution for 12 to 16 hours, then dried at low temperature and calcined at 85 to 125°C to prepare a modified and activated support substrate; Step 2: Dissolving 0.1 to 0.3 g of chloride salt and 1 to 10 g of high molecular weight polyvinylpyrrolidone (PVP) in an ethylene glycol solution by stirring at 100 to 150°C, adding 10 to 30 mL of a silver-containing aqueous solution, and then hydrothermally reacting in an autoclave at 110 to 160°C for 2 to 6 hours, followed by washing and drying with water and ethanol to prepare a nano-scale silver wire-like powder; and Step 3: Mixing 1 to 5 g of ethylene glycol with... The nano-sized silver wire-shaped powder (wt%) is used as the silver source. After stirring evenly to disperse the nano-sized silver wire-shaped powder in an ethylene glycol solution, the modified and activated support substrate is added, so that the nano-sized silver wire-shaped powder is impregnated on the modified and activated support substrate. After low-temperature drying, a silver-containing adsorbent is obtained, which is then calcined at 300-650°C in a hydrogen atmosphere to prepare a nano-silver composite adsorbent.

2. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, The average length of this nanoscale silver wire-like powder is 500±20% nm, and the width is 50±20% nm.

3. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, The alkaline solution is selected from at least one of the group consisting of aqueous solutions of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

4. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, The chloride salts are selected from at least one soluble salt in the group consisting of sodium chloride and potassium chloride.

5. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, The silver-containing aqueous solution is an aqueous solution containing at least one silver compound selected from the group consisting of silver nitrate, silver sulfate, silver acetate, and silver chloride.

6. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, The composition ratio of the modified and activated support substrate to the nano-scale silver linear powder can be adjusted as needed.

7. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, This step involves drying at a low temperature of 50–70°C for 1–3 hours, followed by heating at a rate of 3–5°C / min to 85–125°C for 8–12 hours.

8. The method for preparing the nano-silver composite adsorbent for treating iodine-containing wastewater as described in claim 1, wherein, After drying at a low temperature of 100–140°C for 3–5 hours in the third step, the temperature is increased to 300–650°C in the hydrogen atmosphere at a rate of 3–5°C / min for 0.5–3.5 hours.

Images