CN113164911A

CN113164911A - Radioactive cesium detergent and method for decontaminating water-depth-customized radioactive cesium using same

Info

Publication number: CN113164911A
Application number: CN201980080567.5A
Authority: CN
Inventors: 郑盛旭; 黄庭环; 申宇湜; 金永傧
Original assignee: Korea Basic Science Institute KBSI
Current assignee: Korea Basic Science Institute KBSI
Priority date: 2018-12-06
Filing date: 2019-11-25
Publication date: 2021-07-23
Anticipated expiration: 2039-11-25
Also published as: JP2022511035A; KR102183844B1; JP7123262B2; CN113164911B; WO2020116841A1; KR20200069092A

Abstract

The present invention provides the following radioactive cesium detergents: the composition containing the clay mineral and the foaming agent can adsorb or remove radioactive cesium in water, and the foaming rate depending on the water depth can be adjusted by adjusting the contents of the clay mineral and the foaming agent. The present invention finally includes the technical idea of maximizing the horizontal dispersion performance by adjusting the sedimentation rate of zeolite or the like as a radioactive cesium detergent, thereby proposing a new model in the field of radioactive cesium detergent in water.

Description

Radioactive cesium detergent and method for decontaminating water-depth-customized radioactive cesium using same

Technical Field

The present technology relates to a technique for removing contaminants in water, and more particularly to a technique relating to a detergent and a method for removing radioactive cesium, which are capable of effectively removing radioactive cesium present in various deep water sites in water.

Background

In 2011, 3 months and 3 days, the fukushima nuclear power station accident causes the pollution of soil, animals, plants, wastes and the like by radioactive substances, thereby causing very serious environmental problems. Radioactive substances generated when a nuclear power plant has an accident are mainly radioactive iodine, radioactive cesium and the like. Radioactive iodine has a relatively short half-life of about 8 days, radioactive cesium has a long half-life of about 30 years, and cesium has chemical properties similar to potassium, and therefore, it is concentrated in a muscle or the like during absorption, and causes immunodeficiency and various cancers (infertility, bone marrow cancer, lung cancer, thyroid cancer, breast cancer, etc.) or the like.

Minerals such as zeolite must be in direct contact with contaminants such as radioactive cesium in order to remove these contaminants. When radioactive cesium flows into a place with a fixed capacity such as a clean water treatment plant, there is no problem in contact between zeolite and cesium, but in a place with an unfixed capacity such as lake water, there is a possibility that the contact is limited by spraying on the water surface. Further, since the specific gravity of zeolite is 2.0 to 2.4 and the sedimentation rate in water is high, the zeolite may not have a sufficient residence time for reacting with radioactive cesium. Also, in a relatively large fresh water body such as an octant lake, the deepest water depth is 23m, and the average water depth is 6m, in which case there is a possibility that the pollutants may not be uniformly distributed at different depths due to a stratification phenomenon or the like caused by a change in water temperature.

Disclosure of Invention

Technical problem

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a radioactive cesium decontaminant capable of efficiently dispersing radioactive cesium in a horizontal direction while providing a sufficient residence time in the case where a contaminant may be unevenly distributed in different water depths depending on the scale of a water system, and capable of decontaminating radioactive cesium in a water depth-customized manner.

Further, an object of the present invention is to provide a method for removing radioactive cesium, which can effectively remove radioactive cesium in water according to water depth by using the radioactive cesium removal agent.

Means for solving the problems

Specific examples of the present application are described below with reference to the drawings. In the following description, various specific details, such as specific forms, compositions, and steps, are described in order to fully understand the present invention. However, the specific example may be implemented without one or more of these specific details, or may be implemented together with other known methods and forms. In other instances, well known processes and manufacturing techniques have not been described in particular detail in order to avoid unnecessarily obscuring the present invention. Throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, form, combination, or characteristic described in connection with the embodiment is included in one or more embodiments of the present invention. Therefore, the expression "in one specific example" or "specific example" in various places throughout the specification does not necessarily mean the same specific example. Furthermore, the particular features, aspects, combinations, or characteristics may be combined in any suitable manner in one or more embodiments.

Unless specifically defined otherwise herein, all scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In the present invention, "radioactive material" means a main pollutant generated in a major nuclear accident. In the case of nuclear reactor power plants which are currently widely spread, nuclear fission in nuclear reactors is accompanied by the production of a large amount of radioactive byproducts. The main radioactive materials may be fission products and active elements of extremely dangerous radioactive isotopes, such as iodine 131, cesium 134, cesium 137, cerium 144, rhodium 106, cobalt 60, strontium 90, radium 226, uranium 234, uranium 235, uranium 238, plutonium 239, and the like, but are not limited thereto.

In the present invention, "contaminated water" may refer to an aqueous solution in which a radioactive substance is dissolved. When a serious nuclear accident occurs, the radioactive materials with high volatility are gasified and move to the atmosphere at the initial stage of the serious accident, and can flow into the surface environment through radioactive dust or rainfall. Radioactive substances such as radioactive cesium can be dissolved in the contaminated water in an ionic form. Or can be strongly bound to and contained in clay and organic matter.

In the present invention, zeolite (zeolite) is known as a mineral group belonging to a network silicate, and has many pores of several nanometers inside, and has a high removal efficiency for various pollutants. Since moisture and malodor can be removed by absorption and heavy metals can be captured, it can also be used as a material for an ion exchanger. In particular, natural zeolite is mostly collected in the form of "zeolite tuff (zeolitic tuff)" in which fine-grained tuff is deteriorated, and chemically, as hydrous silicate minerals containing a small amount of Na, K, Ca, Mg, Sr or Ba as cations, there are clinoptilolite (clinoptilolite), Mordenite (Mordenite), Heulandite (Heulandite), phillipsite (phillipsite), erionite (erionite), chabazite (chabazite), ferrierite (ferrierite), and the like, but not limited thereto.

In the present invention, sodium bicarbonate generates HCO during decomposition by the action of heat during drying₃Gas, thereby creating pores or pores, Na⁺The residue may be left in the adsorbent after firing and contribute to the formation of structural force. And, in the process of forming the above-mentioned pores or pores,functions to adhere or fix the natural zeolite, citric acid, corn starch to the adsorbent material of the present invention without an outer membrane.

The corn starch of the present invention may be amylose-containing starch extracted from corn, but is not limited thereto. Also, starch complexes such as high amylose corn starch and complexes of corn starch may be used. The maize of the invention may be one obtained in the natural state or by standard crossing techniques including crossbreeding, translocation, inversion, transformation, or any other genetic or chromosomal manipulation including these variations, but is not limited thereto.

The starch of the present invention is prepared by physical processing procedures including extrusion molding, precompression, cooking of the starch slurry, spray drying and Fluidized bed agglomeration (Fluidized bed agglomeration), but is not limited thereto. In one example, the process may be an extrusion process. The starch particles having gelatinized and non-gelatinized portions are produced by pre-gelatinizing the starch portion by the treatment. In one example, the gelatinized starch is substantially combined with non-gelatinized particles (i.e., granules). In the present invention, corn starch serves to stabilize the dosage form of the detergent.

According to an example of the present invention, it relates to a detergent, which is a radioactive pollutant detergent, for removing radioactive substances contained in polluted water, comprising: a zeolite; sodium bicarbonate; and citric acid.

In the present invention, the above detergent may comprise: 30-60 weight percent zeolite; 20 to 40 weight percent of sodium bicarbonate; and 10-40 weight percent citric acid, but not limited thereto.

In the present invention, the above detergent may comprise: 40-60 weight percent zeolite; 20 to 40 weight percent of sodium bicarbonate; and 10 to 20 weight% of citric acid, the detergent may be used to remove radioactive substances contained in the middle water system, but is not limited thereto.

In the present invention, the above detergent may comprise: 30-40 weight percent zeolite; 30-40 weight percent of sodium bicarbonate; and 20 to 40 weight% of citric acid, the detergent may be used to remove radioactive substances contained in the deep water system, but is not limited thereto.

In the present invention, the detergent may further include corn starch, and preferably, the detergent may include the corn starch in an amount of 5 to 20 wt%, but is not limited thereto.

In the present invention, the weight ratio of the zeolite, the sodium bicarbonate, the citric acid and the corn starch in the detergent may be 2: 1 to 2: 0.5 to 1: 0.25 to 1, but is not limited thereto.

In the present invention, the weight ratio of zeolite, sodium bicarbonate, citric acid and corn starch contained in the detergent may be 2: 1: 0.5, and the detergent may be used to remove radioactive materials contained in the middle water system, but is not limited thereto.

In the present invention, the weight ratio of zeolite, sodium bicarbonate, citric acid and corn starch contained in the detergent may be 2: 1: 0.5: 0.25, and the detergent may be used to remove radioactive materials contained in the deep water system, but is not limited thereto.

In the present invention, the above zeolite may comprise 50 to 60 weight percent of heulandite and 40 to 50 weight percent of mordenite, but is not limited thereto.

In the present invention, the specific surface area of the zeolite may be 50m²/g～70m²Or the average pore volume may be 0.1ml/g to 0.15ml/g, or the average pore diameter may be 5nm to 15nm or the cation exchange capacity may be 60meq/100g to 120meq/100g, but is not limited thereto.

ADVANTAGEOUS EFFECTS OF INVENTION

The radioactive cesium decontamination agent according to an embodiment of the present invention includes a clay mineral such as zeolite for adsorbing radioactive cesium, and a foaming component, and the contents of the clay mineral and the foaming component may be adjusted to adjust the foaming speed of the decontamination agent. In this way, the expression speed or position of the decontamination effect can be adjusted according to various depths or water depths, and customized decontamination can be performed according to various water depths of the water system. This ultimately means that radioactive cesium contamination sources present in all water depths can be carefully removed, in such a way that the decontamination efficiency of radioactive cesium in water can be maximized.

Therefore, when the above-mentioned detergent is sprayed on various horizontal areas of a water system contaminated with radioactive cesium, and simultaneously, various combinations of detergents are sprayed, uniform detergent effects can be exhibited in the horizontal and vertical areas.

However, the weight per unit, the capacity per unit, and the like of the detergent may be variously modified in consideration of the capacity, the area, the water depth, and the like of the water system.

The present invention finally includes the technical idea of maximizing the horizontal dispersion performance by adjusting the sedimentation rate of zeolite or the like as a radioactive cesium detergent, thereby proposing a new model in the field of radioactive cesium detergent in water.

Drawings

Fig. 1a is a graph showing the results of X-ray diffraction analysis on a Zeolite (ZG) sample, fig. 1b is a graph showing the results of X-ray diffraction analysis on a korean celebration zeolite (KGZ) sample, and fig. 1c is a graph showing the results of X-ray diffraction analysis on a korean bulrush zeolite (KPZ) sample.

FIG. 2 is a graph showing the results of adsorption partition coefficients of low-concentration cesium (Cw ≈ 50 μ g/L) on various clay minerals.

Fig. 3 is a schematic view showing a large-sized column water tank.

Fig. 4 is a graph showing the results of a 40L water tank preparation experiment.

FIGS. 5a to 5f are graphs showing the change in turbidity concentration over time using a zeolite powder detergent. FIG. 5a is a graph showing the change in turbidity concentration after 1 minute using a zeolite powder type detergent, FIG. 5b is a graph showing the change in turbidity concentration after 3 minutes using a zeolite powder type detergent, FIG. 5c is a graph showing the change in turbidity concentration after 10 minutes using a zeolite powder type detergent, FIG. 5d is a graph showing the change in turbidity concentration after 60 minutes using a zeolite powder type detergent, FIG. 5e is a graph showing the change in turbidity concentration after 120 minutes using a zeolite powder type detergent, and FIG. 5f is a graph showing the change in turbidity concentration after 1440 minutes using a zeolite powder type detergent.

Fig. 6a to 6f are graphs showing the change in cesium concentration over time using zeolite powder type detergents. Fig. 6a is a graph showing the change in cesium concentration after 1 minute using a zeolite powder type detergent, fig. 6b is a graph showing the change in cesium concentration after 3 minutes using a zeolite powder type detergent, fig. 6c is a graph showing the change in cesium concentration after 10 minutes using a zeolite powder type detergent, fig. 6d is a graph showing the change in cesium concentration after 60 minutes using a zeolite powder type detergent, fig. 6e is a graph showing the change in cesium concentration after 120 minutes using a zeolite powder type detergent, and fig. 6f is a graph showing the change in cesium concentration after 1440 minutes using a zeolite powder type detergent.

FIGS. 7a to 7f are graphs showing the change in turbidity concentration over time using the detergent of example 1. FIG. 7a is a graph showing a change in turbidity concentration after 1 minute using the detergent of example 1, FIG. 7b is a graph showing a change in turbidity concentration after 3 minutes using the detergent of example 1, FIG. 7c is a graph showing a change in turbidity concentration after 10 minutes using the detergent of example 1, FIG. 7d is a graph showing a change in turbidity concentration after 60 minutes using the detergent of example 1, FIG. 7e is a graph showing a change in turbidity concentration after 120 minutes using the detergent of example 1, and FIG. 7f is a graph showing a change in turbidity concentration after 1440 minutes using the detergent of example 1.

FIGS. 8a to 8f are graphs showing the change in cesium concentration over time using the detergent of example 1. Fig. 8a is a graph showing a change in cesium concentration after 1 minute using the detergent of example 1, fig. 8b is a graph showing a change in cesium concentration after 3 minutes using the detergent of example 1, fig. 8c is a graph showing a change in cesium concentration after 10 minutes using the detergent of example 1, fig. 8d is a graph showing a change in cesium concentration after 60 minutes using the detergent of example 1, fig. 8e is a graph showing a change in cesium concentration after 120 minutes using the detergent of example 1, and fig. 8f is a graph showing a change in cesium concentration after 1440 minutes using the detergent of example 1.

FIGS. 9a to 9f are graphs showing the change in turbidity concentration over time using the detergent of example 2. FIG. 9a is a graph showing a change in turbidity concentration after 1 minute using the detergent of example 2, FIG. 9b is a graph showing a change in turbidity concentration after 3 minutes using the detergent of example 2, FIG. 9c is a graph showing a change in turbidity concentration after 10 minutes using the detergent of example 2, FIG. 9d is a graph showing a change in turbidity concentration after 60 minutes using the detergent of example 2, FIG. 9e is a graph showing a change in turbidity concentration after 120 minutes using the detergent of example 2, and FIG. 9f is a graph showing a change in turbidity concentration after 1440 minutes using the detergent of example 2.

FIGS. 10a to 10f are graphs showing the change in cesium concentration over time using the detergent of example 2. Fig. 10a is a graph showing a change in cesium concentration after 1 minute using the detergent of example 2, fig. 10b is a graph showing a change in cesium concentration after 3 minutes using the detergent of example 2, fig. 10c is a graph showing a change in cesium concentration after 10 minutes using the detergent of example 2, fig. 10d is a graph showing a change in cesium concentration after 60 minutes using the detergent of example 2, fig. 10e is a graph showing a change in cesium concentration after 120 minutes using the detergent of example 2, and fig. 10f is a graph showing a change in cesium concentration after 1440 minutes using the detergent of example 2.

Figure 11a shows one embodiment of a dosage form of the detergents of examples 1 and 2, and figure 11b shows one embodiment of a dosage form of the detergents of examples 3 and 4.

FIGS. 12a to 12d show the dispersion state of the detergent of example 3 after administration for various times. FIG. 12a shows a state of dispersion after 2 seconds from the administration of the detergent of example 3, FIG. 12b shows a state of dispersion after 8 seconds from the administration of the detergent of example 3, FIG. 12c shows a state of dispersion after 20 seconds from the administration of the detergent of example 3, and FIG. 12d shows a state of dispersion after 40 seconds from the administration of the detergent of example 3.

FIGS. 13a to 13d show the dispersion state of the detergent of example 4 after administration for various times. FIG. 13a shows a state of dispersion after 2 seconds from the administration of the detergent of example 4, FIG. 13b shows a state of dispersion after 5 seconds from the administration of the detergent of example 4, FIG. 13c shows a state of dispersion after 20 seconds from the administration of the detergent of example 4, and FIG. 13d shows a state of dispersion after 40 seconds from the administration of the detergent of example 4.

FIGS. 14a to 14c show the dispersion state of the detergent of comparative example 11 after administration for various times. FIG. 14a shows the state of dispersion after 4 seconds from the administration of the detergent of comparative example 11, FIG. 14b shows the state of dispersion after 20 seconds from the administration of the detergent of comparative example 11, and FIG. 14c shows the state of dispersion after 60 seconds from the administration of the detergent of comparative example 11.

FIGS. 15a to 15c show the dispersion state of the detergent of comparative example 12 after administration for various times. FIG. 15a shows the state of dispersion after 2 seconds from the administration of the detergent of comparative example 12, FIG. 15b shows the state of dispersion after 5 seconds from the administration of the detergent of comparative example 12, and FIG. 15c shows the state of dispersion after 70 seconds from the administration of the detergent of comparative example 12.

FIGS. 16a to 16d show the dispersion state of the detergent of comparative example 13 after administration for various times. FIG. 16a shows the dispersion state after 4 seconds from the administration of the detergent of comparative example 13, FIG. 16b shows the dispersion state after 8 seconds from the administration of the detergent of comparative example 13, and FIG. 16c shows the dispersion state after 20 seconds from the administration of the detergent of comparative example 13.

Fig. 17a shows a state after 15 seconds from the introduction of a detergent prepared in a formulation of 10g at the same compounding ratio as in example 3 into two water tanks at different temperatures of 0c (left side) and 20 c (right side), respectively.

Fig. 17b shows a state after 15 seconds from the introduction of a detergent prepared in 12g dosage form at the same compounding ratio as in example 4 into two water tanks at different temperatures of 0 ℃ (left side) and 20 ℃ (right side), respectively.

Fig. 18a shows desorption rates from 14 days to about 70 days in low concentration and high concentration as an example of the present invention, to observe desorption effects of illite at different temperatures and concentrations for different times.

Fig. 18b shows desorption rates from 14 days to about 70 days as low concentration and high concentration to observe desorption effects of zeolite at different temperatures and concentrations for different times as an example of the present invention.

Detailed Description

Modes for carrying out the invention

Hereinafter, the radioactive cesium decontamination agent and the decontamination method of radioactive cesium using the water depth customization type of the substance according to the present invention will be described in detail with reference to the drawings, experimental data, and the like. However, the following description is only an exemplary description for helping understanding of the present invention, and the technical idea of the present invention is not limited by the following description. The technical idea of the present invention can be explained or limited only by the scope of claims of the invention described later.

Preparation of samples for detergents

A natural zeolite sample (ZG) was selected as the base material for the radioactive cesium detergent. Fig. 1a is a graph showing the results of X-ray diffraction analysis on a Zeolite (ZG) sample. The zeolite was selected from a sample produced in the celebration state area of north celebration, korea. The most widely marketed 45 μm particle size product of the celecoxib zeolite (KGZ) products is purchased. Meanwhile, table 1 below is a table showing the composition ratios of the constituent components (minerals) confirmed by the above diffraction analysis results. Referring to fig. 1a and table 1, it was confirmed by X-ray diffraction analysis that the zeolite consisted of heulandite and mordenite, which are minerals belonging to zeolite, and the composition ratio consisted of about 53% heulandite and about 47% mordenite.

Punjin Zeolite (KPZ) from Korea Punjin, preferably Punjin Yinyiao gulf of Korea, is also composed of heulandite and mordeniteStone composition, similar to the properties of korea celebration zeolite (KGZ). Fig. 1b is a graph showing the results of X-ray diffraction analysis on a sample of the korean celebration zeolite, and fig. 1c is a graph showing the results of X-ray diffraction analysis on a sample of the korean pekou zeolite. As shown in table 1, although the composition ratio of the korean celebration zeolite and korean pu zeolite is slightly different, the X-ray diffraction analysis results show substantially similar peak morphologies (fig. 1b and 1 c). The specific surface area of the zeolite is about 60m²(ii)/g, showing a very small particle size, and a cation exchange capacity of about 72meq/100g to 100meq/100g, showing a very high value compared to Korea Rongkui illite as a comparative object (Table 2). In particular, the specific surface area and the cation exchange amount can be factors that affect the adsorption capacity.

TABLE 1

Mineralogical characterization of Zeolite (ZG) samples

Table 2 shows the results of evaluating the characteristics of the prepared zeolite samples. FIG. 2 is a graph showing the results of adsorption partition coefficients of low-concentration cesium (Cw ≈ 50 μ g/L) on various clay minerals. Meanwhile, table 3 is a table showing the adsorption distribution coefficient of each mineral in a quantitative manner. Referring to tables 2 and 3 and FIG. 2, the specific surface area of the zeolite was about 65m²The cation exchange capacity was about 100meq/100g, and both showed very high values. Results of small-scale adsorption experiments using 50mL vials (final), partition coefficient (K) for cesium_d) It appeared to be very high, about 600000L/kg, a value about 100 to 1000 times higher than other minerals. The main adsorption mechanism carried out in zeolites is the cation exchange reaction that is manifested in the pores, which can be explained by the high specific surface area and cation exchange capacity of the zeolite contributing to the increased removal of cesium by the zeolite.

TABLE 2

TABLE 3

From the results of observing the desorption effect of the illite and the zeolite at different concentrations in different time periods, the desorption degree of the two minerals does not change greatly along with the change of the time period, but most of the minerals are desorbed in the early stage of the reaction. Illite exhibits a desorption rate of about 20% at low concentrations and about 50% at high concentrations, and no difference in desorption characteristics depending on temperature was observed. It is worth mentioning that at high concentrations the desorption shows a tendency to increase slightly with time. On the other hand, zeolite shows a high desorption rate at a low concentration, but in all cases, the desorption rate is less than 1%, showing very excellent adsorption stability.

In this preparation example, zeolite is merely exemplified as the clay mineral used as the detergent, but it is needless to say that the use of another mineral such as illite, bentonite, sericite, or the like is included in the scope of the technical idea of the present invention. Further, various kinds of the above minerals may be mixed and used depending on the application water system.

In situ simulation experiment

In all of the conventional laboratory experiments for confirming the adsorption efficiency of cesium by using a natural mineral such as zeolite, a 50mL vial having a small volume was used, and the zeolite in the vial was uniformly reacted with cesium to the utmost extent by continuous stirring. The above method has a cesium adsorption performance that can be theoretically maximized(Qm, single plane maximum adsorption, ideal adsorption model (Langmuir model)) and adsorption efficiency. However, in an actual environment in which a detergent such as zeolite was sprayed, 100% contact was impossible as in the experimental environment, and therefore, in order to confirm the efficiency in the environment of the above-mentioned scale, an experiment was performed by manufacturing a large-sized clear water tank of 1 ton scale. Fig. 3 is a schematic view showing a large-sized column water tank. Referring to fig. 3, in order to confirm the dispersion of the detergent and the cesium removal rate at different distances and at different depths in the water tank, a tube for collecting a sample was manufactured and provided using acryl. The tube used for taking the sample had a diameter of 20mm (inner diameter 14mm) and a total extension of 1.7 m. In order to allow the water quality sample to flow in 30cm units, a screen of 5cm length was perforated at intervals of 30cm after being separated from the bottom, and the holes were arranged in 4 sections in total. After the water tank was filled with 1 ton of water, to reflect the competitive ionic effects that may occur in the actual field, the main cations (Ca, Mg, Na and K) and the main anions (Cl, SO) were added₄、HCO₃) The water quality was adjusted to be similar to that of the octatang lake as the site of the simulation, and was adjusted to be a low-concentration cesium (about 50. mu.g/L) environment homogeneously. Then, a detergent was added to confirm turbidity and cesium removal efficiency.

Before spraying the detergent, a water quality sample for confirming the initial water quality was collected using a Peristaltic Pump (peristatic Pump), and then the detergent was put in to collect a sample for confirming the change with time. When the sample was collected, about 25mL of the sample was collected at a flow rate of 15 mL/min. The turbidity of the collected sample was measured, and then the sample was placed in a centrifuge at 3500rpm for 30 minutes, and the supernatant was collected. The pH of the supernatant was lowered to 2 or less using nitric acid, and the supernatant was stored at a temperature of 4 ℃ or less, and the cesium concentration was measured using ICP-MS.

The species of cesium that can be used in this experiment is not limited. One factor of radionuclide movement in Aquatic environments is the action of stabilizing nuclides, and thus movement of stable Cesium in Aquatic environments is probably to predict the long-term effect Cesium 137 has on the environment (Tiwari, Diwakar & Lalhmunama, Lalhmunama & Choi, S. & Lee, Senng-Mok. (2014.) Activated series: An Effective and Effective Natural Clay Material for the introduction of center from aqueous environmental. Pedosphere.24.731-742.).

Powder detergent (powder type zeolite used alone)

Before a large water tank experiment of 1 ton scale was performed, a preliminary experiment was performed in a water tank of 40L scale in order to calculate an appropriate amount of zeolite necessary for removal of radioactive cesium. As a result of preliminary experiments, in the case where turbidity and cesium removal rate were considered at the same time, cesium was most effectively removed when 2g of zeolite was charged in 40L, and thus it was selected as a basic design amount. Fig. 4 is a graph showing the results of a 40L water tank preparation experiment. The amount of zeolite required for the 1 ton scale water tank selected on this basis was 50 g.

Using the results of the preliminary experiment, 50g of zeolite powder was put in a water tank containing 1 ton of cesium-contaminated water, and then turbidity and cesium concentration were measured at various times, locations and depths. FIGS. 5a to 5f are graphs showing the change in turbidity concentration over time using a zeolite powder detergent. FIG. 5a is a graph showing the change in turbidity concentration after 1 minute using a zeolite powder type detergent, FIG. 5b is a graph showing the change in turbidity concentration after 3 minutes using a zeolite powder type detergent, FIG. 5c is a graph showing the change in turbidity concentration after 10 minutes using a zeolite powder type detergent, FIG. 5d is a graph showing the change in turbidity concentration after 60 minutes using a zeolite powder type detergent, FIG. 5e is a graph showing the change in turbidity concentration after 120 minutes using a zeolite powder type detergent, and FIG. 5f is a graph showing the change in turbidity concentration after 1440 minutes using a zeolite powder type detergent.

Referring to fig. 5a to 5f, the zeolite powder reached the bottom of the water tank within 1 minute, showing a greater tendency to settle vertically than to disperse horizontally.

Referring to fig. 6a to 6f, it was confirmed that the cesium concentration in water also exhibited a decrease along the position where the turbidity increased, and the decontamination effect was collectively exhibited in the periphery of the zeolite. It was confirmed that the above tendency was strongly exhibited between 1 minute and 3 minutes in the initial stage of the experiment, and after 3 minutes, all zeolite powder reached the bottom, and after 10 minutes, the turbidity was first homogenized, and then the cesium concentration in water was gradually homogenized. After 24 hours, the zeolite particles settled at the bottom to such an extent that recovery by peristaltic pump was difficult, at which point the final cesium removal rate was about 60%, which performed similarly at all locations.

Deeply tailored detergent

When the zeolite in the powder form was put into a water tank, it was confirmed that the vertical dispersion was dominant due to initial sedimentation and almost no horizontal dispersion was formed. When spraying a detergent over a wide area, if the horizontal dispersion is low, there is a disadvantage in that more sites are required to be invested. As ingredient for foaming, sodium bicarbonate (NaHCO)₃) And citric acid (C)₆H₈O₇) Is a component that can increase horizontal dispersion by adjusting the foaming speed, thereby adjusting the expression of zeolite.

EXAMPLE 1 preparation of Radioactive Cesium detergents (for deep layer)

As a foaming detergent, sodium bicarbonate, citric acid and zeolite as main additives were mixed at the content of the mixing ratio shown in Table 4, and ethanol (C) was used₂H₅OH) to shape them. The same amount of 50g as the result of the preliminary experiment was used for the amount of zeolite charged based on 1 ton. Based on the total mass of the detergentThe detergent was prepared by injecting ethanol in an amount of 20% for mixing and molding the zeolite and other accessory materials, placing in a preparation mold, and drying in an oven set at 40 ℃ for 2 days or more. Finally, as a result of comparing the weight of the detergent prepared, the mass loss was about 20% during the preparation and drying. The final dosage form is in the form of pellets or tablets.

Comparative examples 1 to 5 preparation of Radioactive Cesium detergents (out of depth)

Using the same method as example 1, comparative examples 1 to 5 were respectively prepared according to the composition ratios shown in table 4 below.

TABLE 4

Analysis of Dispersion in Water and stain removal tendency

In order to remove cesium from water, detergents (example 1, comparative example 1 to comparative example 5) prepared in the above different mixing ratios were put in a water tank and then observed for sedimentation and dispersion tendency, and turbidity, cesium concentration and the like at different positions and different depths of the detergent of example 1 in which dispersion tendency was most excellent were measured and shown.

Referring to fig. 7a to 7f, unlike the powder type detergent in which only vertical sedimentation occurs without horizontal dispersion, it was confirmed that the detergent began to melt around 60cm below the water surface and settled after being dispersed and dispersed significantly horizontally. Although the overall sedimentation is rapid sedimentation similar to that of the powder type detergent, it shows a much larger dispersion area in the horizontal direction than that of the powder type. At a time point of about 60 minutes after the detergent was put in, floating zeolite particles were still confirmed.

Referring to fig. 8a to 8f, in the case of the cesium concentration in water, it was confirmed that cesium was removed more rapidly at the deep position than in the case of the detergent in the powder form, and the removal rate of cesium at the deepest position reached about 80% after one day. But, in contrast, exhibits a characteristic that cesium near the water surface is hardly removed.

In the case of the detergents of comparative examples 1 to 5 prepared at a different compounding ratio from that of example 1, no significant sedimentation velocity retardation or horizontal dispersion phenomenon occurred. In the case of some detergents, no dispersion occurred until the bottom of the tank was reached, while some detergents were dispersed, but to a lesser extent.

As described above, the conventional powder type detergent is improved by selecting zeolite powder as a base material of a cesium detergent in water and then adding a chemical such as sodium bicarbonate or citric acid. The results of measuring turbidity and cesium concentration after feeding the improved detergent into the water tank showed different sedimentation, horizontal dispersion, and space removal rates as compared with the conventional zeolite powder. When zeolite detergent was put in the form of powder, the precipitation in the vertical direction was dominant over the dispersion in the horizontal direction, and the cesium concentration in water was also reduced only in the vertical direction of the zeolite precipitation. Since sedimentation is dominant, the powder reached the bottom in its entirety after 3 minutes of input, and a state of parallel distribution to the bottom was exhibited after 10 minutes.

The remaining types of detergents other than example 1 in the improved detergents of example 1 and comparative example did not undergo significant retardation of sedimentation velocity or dispersion in the horizontal direction. The soil release agent of example 1 settled vertically similarly to the powder type soil release agent, but the soil release agent was dispersed horizontally in the vicinity of about 60cm below the water surface and then settled again, and the dispersion area was significantly larger than that of the powder type soil release agent. Although the decrease in the cesium concentration in water slightly varies depending on the measurement position, the detergent of example 1 retains cesium in the vicinity of the water surface even after a long period of time, unlike the powder-type detergent in which the decrease in the cesium concentration occurs even in the vicinity of the water surface.

As described above, in consideration of the sedimentation, dispersion and cesium removal characteristics of the detergents of different types, it was judged that it is reasonable to use the detergent of example 1 for removing cesium distributed in the deep layer of the water system among the detergents improved in different mixing ratios.

Based on the experimental results, as a radioactive cesium detergent, the following detergents were determined as a custom-made detergent for decontaminating radioactive cesium of a deep water system, which contained: 30-40 weight percent zeolite; 30-40 weight percent of sodium bicarbonate; and 20-40 weight percent of citric acid.

EXAMPLE 2 preparation of Radioactive Cesium detergents (for intermediate layer)

As a foaming detergent, sodium bicarbonate, citric acid and zeolite as main additives were mixed at the content of the mixing ratio shown in Table 5, and ethanol (C) was used₂H₅OH) to shape them. The same amount of 50g as shown in the results of the preliminary experiment was used for the amount of zeolite charged based on 1 ton. The detergent was prepared by injecting ethanol for mixing and molding the zeolite and other accessory materials in an amount of about 20% of the total mass of the detergent, placing in a preparation mold, and drying in an oven set at 40 ℃ for 2 days or more. Finally, as a result of comparing the weight of the detergent prepared, the mass loss was about 20% during the preparation and drying. The final dosage form is in the form of pellets or tablets.

Comparative examples 6 to 10 preparation of Radioactive Cesium detergents (outside the middle layer)

Using the same method as example 2, comparative examples 6 to 10 were respectively prepared according to the composition ratios shown in table 5 below.

TABLE 5

Type (B)	Sodium bicarbonate	Citric acid	Zeolite
				Example 2	29	14	57
Comparative example 6	49	2	49
				Comparative example 7	48	5	48
Comparative example 8	44	11	44
				Comparative example 9	6	31	63
Comparative example 10	25	25	50

Analysis of Dispersion in Water and stain removal tendency

In order to remove cesium from water, detergents (example 2, comparative example 6 to comparative example 10) prepared in the above different mixing ratios were put in a water tank and then observed for sedimentation and dispersion tendency, and turbidity, cesium concentration and the like at different positions and different depths of the detergent of example 2 in which dispersion tendency was most excellent were measured and shown.

Referring to fig. 9a to 9f, unlike the powder type detergent in which only vertical sedimentation occurs without dispersion in the horizontal direction, the detergent shows a state of being vertically sedimented to about 30cm below the water surface, then rising to the water surface again, and then spreading downward, and unlike the powder type detergent in which all of the detergent sedimented to the bottom in less than 1 hour, a small amount of detergent particles float at the time point after 2 hours have elapsed, and thus it can be confirmed that the sedimentation delay effect occurs. Further, it was confirmed that the horizontal dispersion effect of the particles occurred also in the process of settling after floating on the water surface again.

Referring to fig. 10a to 10f, as in the case where horizontal dispersion occurs significantly, the concentration of cesium also decreases rapidly in a wide range, and although the removal rate of cesium differs depending on the depth, it is confirmed that it is up to 70%.

In the case of the detergents of comparative examples 6 to 10 prepared at a different compounding ratio from that of example 2, no significant sedimentation velocity retardation or horizontal dispersion phenomenon occurred. In the case of some detergents, no dispersion occurred until the bottom of the tank was reached, while some detergents were dispersed, but to a lesser extent.

The remaining types of detergents other than example 2 in the modified detergents of example 2 and comparative example did not undergo significant retardation of sedimentation velocity or dispersion in the horizontal direction. The detergent of example 2 settled vertically similarly to the powder detergent, but floated up again to the water surface in the vicinity of 30cm below the water surface to delay the settlement, and in this process, it was confirmed that a dispersion phenomenon in the horizontal direction also occurred. Although the decrease in the cesium concentration in water slightly varies depending on the measurement position, it shows a rapid decrease in a wide range similarly to the area where the particles are dispersed.

As described above, in consideration of the sedimentation, dispersion and cesium removal characteristics of the detergents of different types, it is considered reasonable to use the detergent of example 2 for removing cesium distributed in the middle layer portion of the aqueous system among the detergents improved at different mixing ratios.

Based on the experimental results, as a radioactive cesium detergent, the following detergents were determined as a custom-made detergent for decontaminating radioactive cesium of a middle-layer water system, which contained: 40-60 weight percent zeolite; 20 to 40 weight percent of sodium bicarbonate; and 10-20 weight percent of citric acid.

EXAMPLE 3 preparation of detergent formulation supplemented with corn starch (for the middle layer)

Corn starch (corn-starch) was added to the foaming detergent of example 3 to enhance the binding force. If the detergent also contains corn starch, the adsorbent can be adjusted to a specific dosage form, and the depth can be adjusted more easily with increasing strength. The detergent prepared without adding corn starch is shown in FIG. 11a, and the detergent prepared with adding corn starch is shown in FIG. 11 b. Example 3 was prepared for the middle layer. The composition ratio of example 3 is shown in table 6.

EXAMPLE 4 preparation of detergent formulation supplemented with corn starch (outside the middle layer)

Example 4 is a stain release agent for use outside the middle layer prepared by varying the composition ratio during the preparation of the foaming stain release agent of example 3. The composition ratio of example 4 is shown in table 6.

Comparative examples 11 to 13 preparation of detergent formulation supplemented with corn starch

Comparative examples 11 to 13 are detergents prepared by changing the composition ratio in the process of preparing an foaming detergent. The composition ratios of comparative examples 11 to 13 are shown in table 6.

TABLE 6

In water dispersion addition analysis

In order to remove cesium in water, after a 40L (length 30cm, width 30cm, depth 50cm) water tank shown in fig. 12 to 17 was filled with water at 20 ℃ to a depth of 45cm, a detergent (example 3, example 4, comparative example 11 to comparative example 13) prepared at a different mixing ratio from the above was poured from 5cm above the water surface, and then sedimentation and dispersion tendency were observed. As shown in FIGS. 11a and 11b, the adsorbent was in the form of a cylinder having a diameter of 3cm and a height of 1cm and a mass of about 10 g.

FIGS. 12a to 12d show the dispersion state of the detergent of example 3 after administration for various times. FIG. 12a shows the state of dispersion after 2 seconds from the administration of the detergent of example 3. Immediately after the detergent of example 3 was dropped to 10cm below the water surface, it was floated again and dispersed on the water surface for 3 seconds. FIG. 12b shows the state of dispersion after 8 seconds from the administration of the detergent of example 3. The detergent of example 3 settled to the bottom of the tank 8 seconds after dosing. FIG. 12c shows the state of dispersion after 20 seconds from the administration of the detergent of example 3. The detergent of example 3, which was strongly dispersed only in the vertical direction, was re-floated on the water surface 20 seconds after the administration. FIG. 12d shows the state of dispersion after 40 seconds after administration of the detergent of example 3.

The detergent of example 3 was continuously dispersed and after 40 seconds, completely dispersed throughout the entire water bath

FIGS. 13a to 13d show the dispersion state of the detergent of example 4 after administration for various times. FIG. 13a shows the state of dispersion after 2 seconds from the administration of the detergent of example 4. The detergent of example 4 settled to 5cm immediately after administration, and settled quickly although it floated again. FIG. 13b shows the state of dispersion after 5 seconds from the administration of the detergent of example 4. The detergent of example 4 settled to the bottom of the tank 5 seconds after dosing. FIG. 13c shows the state of dispersion after 20 seconds from the administration of the detergent of example 4. The detergent of example 4, which was strongly dispersed in the vertical direction and weakly dispersed in the horizontal direction, was allowed to float on the water surface again after 30 seconds of administration. FIG. 13d shows the state of dispersion after 40 seconds after administration of the detergent of example 4. The detergent of example 4 was continuously dispersed and after 35 seconds, completely dispersed throughout the water bath.

FIGS. 14a to 14c show the dispersion state of the detergent of comparative example 11 after administration for various times. FIG. 14a shows the state of dispersion after 4 seconds from the administration of the detergent of comparative example 11. The detergent of comparative example 11 settled to the bottom of the tank 4 seconds after the dosing. FIG. 14b shows the state of dispersion after 20 seconds from the administration of the detergent of comparative example 11. After the detergent of comparative example 11 reached the bottom of the water tank, the particles were dispersed in the vertical direction as the bound detergent was decomposed. FIG. 14c shows the state of dispersion after 60 seconds from the administration of the detergent of comparative example 11. In the detergent of comparative example 11, the particles that have risen to the vicinity of the water surface after dispersion settle again, and after 60 seconds, are uniformly dispersed throughout the water tank.

FIGS. 15a to 15c show the dispersion state of the detergent of comparative example 12 after administration for various times. FIG. 15a shows the state of dispersion after 2 seconds from the administration of the detergent of comparative example 12. The detergent of comparative example 12 was settled to 10cm below the water surface immediately after the dosing, and then floated again and dispersed on the water surface for 1 second. FIG. 15b shows the state of dispersion after 5 seconds from the administration of the detergent of comparative example 12. The detergent of comparative example 12 settled to the bottom of the tank 5 seconds after the dosing. FIG. 15c shows the state of dispersion after 70 seconds from the administration of the detergent of comparative example 12. The detergent of comparative example 12 was dispersed in the vertical direction and after 70 seconds, was completely dispersed.

FIGS. 16a to 16d show the dispersion state of the detergent of comparative example 13 after administration for various times. FIG. 16a shows the state of dispersion after 4 seconds from the administration of the detergent of comparative example 13. The detergent of comparative example 13 settled to 10cm below the water surface immediately after the dosing, and then floated again and dispersed on the water surface for 3 seconds. FIG. 16b shows the state of dispersion after 8 seconds from the administration of the detergent of comparative example 13. The detergent of comparative example 13 settled to the bottom of the tank after 8 seconds of administration, and then was dispersed only in the vertical direction. FIG. 16c shows the state of dispersion after 20 seconds from the administration of the detergent of comparative example 13. The detergent of comparative example 13 was allowed to float to the water surface again after 20 seconds of administration. FIG. 16d shows the state of dispersion after 60 seconds from the administration of the detergent of comparative example 13. The detergent of comparative example 13 was continuously dispersed and after 60 seconds, completely dispersed throughout the water bath.

The evaluation of the dispersion dynamic properties of example 3, example 4, and comparative examples 11 to 13 is shown in table 7 below. The dispersion dynamics were evaluated by trisecting the depth of the tank from top to bottom by 15cm into upper, middle and lower regions, and recording the regions in the order of dispersion of the detergent in the horizontal direction.

TABLE 7

	Dynamic state of dispersion	Speed of dispersion
			Example 3	Upper → middle → lower	40 seconds
Example 4	Up → down → middle	35 seconds
			Comparative example 11	Up → down → middle	60 seconds
Comparative example 12	Upper → middle → lower	70 seconds
			Comparative example 13	Upper → middle → lower	60 seconds

The dispersion rate was evaluated by recording the time when the sorbent had completely diffused throughout the water bath and dispersed. As a result of the experiment, it was judged that the middle layer detergent was applied in the manner of example 3 and the deep layer detergent was applied in the manner of example 4 to be optimal in consideration of the dynamic dispersion and the dispersion speed.

Temperature dependent in-water dispersion addition analysis

Additional experiments were performed to understand the dispersion performance according to temperature and dosage form mass of the adsorbent. Fig. 17a and 17b show the dispersion state of the detergent according to the temperature and the dosage form quality of the adsorbent.

Fig. 17a shows a state after 15 seconds from the introduction of a detergent prepared in a formulation of 10g at the same compounding ratio as in example 3 into two water tanks at different temperatures of 0c (left side) and 20 c (right side), respectively. As a result of evaluating the dispersibility of the soil release agent in a low temperature environment of 0 ℃ to 3 ℃, regardless of the mixing ratio, 10g of the soil release agent prepared was dispersed in only the vertical direction without being dispersed in the horizontal direction in a state of staying on the water surface, and the dispersion rate was remarkably lowered from that at the normal temperature.

Fig. 17b shows a state after 15 seconds from the introduction of a detergent prepared in 12g dosage form at the same compounding ratio as in example 4 into two water tanks at different temperatures of 0 ℃ (left side) and 20 ℃ (right side), respectively. As a result of evaluating the dispersion property of the detergent under a low temperature environment of 0 ℃ to 3 ℃, the detergent prepared at 12g can overcome the problem of the dispersion decrease of the detergent in the case where the detergent reaches the bottom of the water tank due to the increase in weight of the detergent formulation. That is, although the dispersion rate was slightly slower than that at ordinary temperature of 20 ℃, more prominent dispersion dynamic was observed in the same period of time than when the detergent prepared in the form of 10g was dispersed while floating on the water surface.

Industrial applicability

Claims

1. A detergent for radioactive contaminants for removing radioactive contaminants contained in contaminated water, comprising:

a zeolite;

sodium bicarbonate; and

and (4) citric acid.

2. The detergent of claim 1, wherein said detergent comprises:

30-60 weight percent zeolite;

20 to 40 weight percent of sodium bicarbonate; and

10-40 weight percent of citric acid.

3. The detergent of claim 1, wherein said detergent comprises:

40-60 weight percent zeolite;

20 to 40 weight percent of sodium bicarbonate; and

10-20 weight percent of citric acid,

the above-mentioned detergent is used for removing radioactive substances contained in the middle water system.

4. The detergent of claim 1, wherein said detergent comprises:

30-40 weight percent zeolite;

30-40 weight percent of sodium bicarbonate; and

20 to 40 weight percent of citric acid,

the above detergent is used for removing radioactive substances contained in deep water system.

5. The detergent of claim 1, wherein said detergent further comprises corn starch.

6. The detergent of claim 2, wherein said detergent comprises 5-20% by weight of corn starch.

7. The detergent according to claim 6, wherein the detergent contains zeolite, sodium bicarbonate, citric acid and corn starch in a weight ratio of 2: 1 to 2: 0.5 to 1: 0.25 to 1.

8. The detergent according to claim 7,

the weight ratio of zeolite, sodium bicarbonate, citric acid and corn starch in the detergent is 2: 1: 0.5,

9. The detergent according to claim 7,

the weight ratio of zeolite, sodium bicarbonate, citric acid and corn starch in the detergent is 2: 1: 0.5: 0.25,

10. The soil release agent of claim 1, wherein the zeolite comprises:

50-60 wt% of heulandite; and

40-50 weight percent of mordenite.

11. The detergent according to claim 1, wherein the zeolite has a specific surface area of 50m²/g～70m²Or an average pore volume of from 0.1ml/g to 0.15ml/g, or an average pore diameter of from 5nm to 15nm or a cation exchange capacity of from 60meq/100g to 120meq/100 g.

12. The detergent according to claim 1, wherein the radioactive substance is selected from the group consisting of iodine, cesium, cerium, rhodium, cobalt, strontium, radium, uranium, and plutonium.

13. A method for preparing a detergent for radioactive contaminants, characterized in that it is prepared by mixing zeolite, sodium bicarbonate and citric acid to remove radioactive contaminants contained in contaminated water.

14. The method of claim 13, wherein said detergent comprises:

30-60 weight percent zeolite;

20 to 40 weight percent of sodium bicarbonate; and

10-40 weight percent of citric acid.

15. The method of claim 13, wherein said detergent comprises:

40-60 weight percent zeolite;

20 to 40 weight percent of sodium bicarbonate; and

10-20 weight percent of citric acid,

16. The method of claim 13, wherein said detergent comprises:

30-40 weight percent zeolite;

30-40 weight percent of sodium bicarbonate; and

20 to 40 weight percent of citric acid,

17. The method of claim 13, wherein said detergent further comprises corn starch.

18. The method of claim 14, wherein the detergent comprises 5-20 wt% of corn starch.

19. The method of claim 18, wherein the detergent comprises zeolite, sodium bicarbonate, citric acid and corn starch in a weight ratio of 2: 1 to 2: 0.5 to 1: 0.25 to 1.

20. The method for producing a detergent for radioactive contaminants according to claim 19,

21. The method for producing a detergent for radioactive contaminants according to claim 19,

22. The method of claim 13, wherein said zeolite comprises:

50-60 wt% of heulandite;

and 40-50 weight percent of mordenite.

23. The method of claim 13, wherein the zeolite has a specific surface area of 50m²/g～70m²Or an average pore volume of 0.1 to 0.15ml/g, orThe average pore diameter is 5nm to 15nm or the cation exchange capacity is 60meq/100g to 120meq/100 g.

24. The method of claim 13, wherein the radioactive substance is selected from the group consisting of iodine, cesium, cerium, rhodium, cobalt, strontium, radium, uranium and plutonium.