JP5605782B2 - Improved purification method for soil contaminated with radioactive material - Google Patents

Description

  The present invention relates to a radioactive material-contaminated soil by a porous granular paper sludge carbonized fired product, which is modified so as not to adversely affect human health and food or plant safety and good growth. This relates to an improved purification method.

  A proposal regarding the treatment of radioactive materials in concentrated waste liquid of radioactive waste generated from nuclear power plants and radioactive material handling facilities, or liquid waste contained in solid used ion exchange resin, etc. is disclosed in Patent Document 1 below. Or it is described in patent document 21.

  In addition, an emergency gas treatment system is known as a facility for reducing the radioactivity released to the environment in the event of a nuclear reactor accident. This facility is a countermeasure against the events that can be considered in the safety design and evaluation of the reactor facilities among the events that may cause the reactor facilities to be in an abnormal state. It is a facility equipped with a filter that uses and collects inorganic and organic iodine with high efficiency. Proposals relating to the treatment of the above-described gas-based radioactive waste are described in the following Patent Documents 22 to 29.

  When a nuclear explosion accident actually occurs, radioactive substances such as iodine 131, cesium 134, and cesium 137 are released to the environment, and soil is contaminated in a wide area. However, as a result of investigating the following patent documents, no accidents such as meltdown and meltthrough of the reactor are assumed. Therefore, since there is no disclosure of an improved purification method for radioactive material-contaminated soil for purifying soil such as farms (fields, rice fields, etc.), houses, schools, parks, roads, and deserts contaminated with radioactive materials, The treatment of radioactive material contaminated soil is a problem.

  In the following patent document, it is described that concentrated waste liquid generated at nuclear power plants and radioactive material handling facilities and radioactive waste of solid used ion exchange resin are generally treated by chemical or physical methods. Yes. Chemical methods include treatment methods such as chemical precipitation, coprecipitation, adsorption, and extraction. Physical methods include filter removal, magnetic separation, fibrous activated carbon, ion exchange fibers, or alkali titanate fibers. There are treatment methods such as adsorption and filtration with activated carbon filters. The following patent documents do not clearly describe whether these activated carbons are in-house products of the inventors, patentees, etc., or are commercial products. Furthermore, the quality of these activated carbons is almost unknown.

  Activated carbon is generally produced from raw materials such as cereals, coconut shells, wood, coal, and peat, and is used for purification of drinking water and air, deodorization, removal of harmful chemicals, absorption of harmful gases, and the like. In order to improve the ability of the activated carbon by these specific uses, the activated carbon is impregnated with a chemical or a solution of chemical chloride. There are two methods for impregnation, impregnation dipping and spray impregnation.

  Here, activated carbon used in nuclear power plants and radioactive material handling facilities is mainly required to immerse radioactive methyl iodine 131, and either potassium iodide (KI) or triethylenediamine (TEDA), or By impregnating a solution of a mixture of KI and TEDA, the ability of activated carbon can be improved. The absorption capacity of radioactive methyl iodine 131 is described in the Regulation Guide 1.52 of the 2nd revision dated March 1978 of the US Nuclear Regulatory Commission.

JP-A-5-027094 JP-A-6-273589 Japanese Patent Laid-Open No. 8-110395 Japanese Patent Laid-Open No. 10-020090 JP-A-10-510924 JP 11-264896 A Registered Utility Model No. 3065325 JP 2000-081498 A JP 2000-098087 A JP 2002-031698 A Japanese Patent Laid-Open No. 2002-226795 Japanese Patent Laid-Open No. 2002-226796 JP 2003-033653 A JP 2004-520586 A JP 2006-078336 A JP 2006-116376 A JP 2008-0664703 A JP 2008-232773 A JP 2009-244089 A JP 2009-294017 A JP 2010-194541 A Japanese Patent Laid-Open No. 11-512181 JP 2005-147667 A JP 2006-112817 A JP 2006-112820 A JP 2006-118986 A JP 2007-057285 A JP 2008-249358 A JP 2010-127662 A Japanese Patent No. 3352019

  By the way, the paper sludge generated in the paper mill is used as pet toilet articles, fertilizer raw materials, homing agents, auxiliary fuels, cement raw materials, soil improvers, etc. with some of them intact. However, most of it is incinerated and the resulting ash is landfilled or reused. Applications of reuse include iron-making antioxidants, soil conditioners, roadbed materials, and cement raw materials.

  In Patent Document 30, a porous granular material having excellent water absorption capability obtained by squeezing paper sludge having a water content of 50 to 65% from a factory wastewater treatment sludge discharged from a recycled paper factory using waste paper as a raw material, and carbonizing and firing the paper sludge. Carbides have been found to be effective as soil improvement materials, snow melting materials, humidity control materials, adsorbents and siliceous materials, and paper sludge has been recycled. The temperature of carbonization baking is 550 to 750 ° C., and the content and pH (8 to 11) of carbon, silicic acid, aluminum, iron, calcium and magnesium in the obtained porous granular carbide are measured. However, due to the change in the composition of waste paper at that time and now, the moisture content of the paper sludge has increased to 50-85%, and the carbonization firing temperature has been raised to 1,300 ° C. The pH is 11 or more, and changes so that titanium, sodium, potassium and the like are also detected. Under any operating condition, the paper sludge is not impregnated with a solution of either KI or TEDA or a mixture of KI and TEDA.

  Both activated carbon used in the nuclear power plants and radioactive material handling facilities mentioned above, and porous granular paper sludge carbonized products made by carbonizing and baking paper sludge are treated directly into radioactive material contaminated soil and contaminated with radioactive materials. No attempt was made to improve and clean the soil.

  As mentioned above, when an accident such as meltdown or melt-through of a nuclear reactor occurs, radioactive materials such as iodine 131, cesium 134, and cesium 137 are released to the environment, or from nuclear power plants and radioactive material handling facilities. The radioactive material is spilled, so soil in fields, rice fields, houses, schools, parks, roads, etc. is contaminated with radioactive material, and food such as rice, vegetables, beans, and potatoes does not grow. Students will not be able to use facilities such as schools and parks. Therefore, there is a need for an improved purification method for radioactive material contaminated soil that does not adversely affect human health and food.

  Accordingly, the present invention provides a porous granular paper sludge carbonized fired product comprising carbonized and fired paper sludge without impregnating any one of KI and TEDA and a mixture solution of KI and TEDA. Provided is a method for improving and purifying soil contaminated with radioactive materials by use.

  In order to solve the above-mentioned problems, the present invention radioactively converts a carbonized fired product of porous granular paper sludge made by carbonizing and firing paper sludge of a paper mill using waste paper, wood chips alone or both waste paper and wood chips. This is an improved purification method for radioactive material-contaminated soil, which is sprayed or mixed with material-contaminated soil to remove radioactive material from the radioactive material-contaminated soil.

  To confirm whether the porous granular paper sludge carbonized calcined product can remove radioactive materials, the alkali equivalent value of the porous granular paper sludge carbonized calcined product, cation exchange capacity and removal to cesium in cesium chloride solution The property was measured and evaluated by a laboratory test. From these results, it was confirmed that the carbonized calcined product of the porous granular paper sludge was able to remove radioactive substances, and therefore, a field test was performed.

The present invention is characterized by the following.
(1) pH 8 or more, desirably 10 or more, alkali equivalent value 1.0 to 4.0 meq / g (NaOH), desirably 1.5 to 2.5 meq / g (NaOH), cation exchange capacity 1.0 to 4 0.0 meq / 100 g (NH ₄ ⁺ ), preferably 1.5 to 3.0 meq / 100 g (NH ₄ ⁺ ), a porous granular paper sludge carbonized product having an electric conductivity of 70 to 150 μS / cm, Generated by carbonizing and baking paper sludge from paper mills using single chips or both waste paper and wood chips, and spraying and mixing the porous granular paper sludge carbonized products to radioactive material contaminated soil Is improved from the radioactive material contaminated soil.
(2) The manufacturing process of the porous granular paper sludge carbonized fired product does not include an impregnation process of any one of KI and TEDA and a solution of a mixture of KI and TEDA.
(3) The radioactive substance-contaminated soil contains a total concentration of radioactive cesium 134 and cesium 137 of 800 Bq / kg or more.
(4) The amount of the carbonized calcined porous granular paper sludge diffused or mixed in the radioactive material contaminated soil is 0.1-6 kg / m ² (0.5-50 kg / m ³ ) (0 of dry soil 0.1 to 6% by weight), preferably 1.0 to 3.5 kg / m ² (8 to ³⁰ kg / m ³ ) (0.9 to 3.3% by weight of dry soil).
(5) The paper sludge has a moisture content of 50 to 85%, and after granulating and drying the paper sludge, the carbonization temperature is 500 to 1,300 ° C, preferably 700 to 1,200 ° C. Carbonized and fired in a firing furnace. More desirably, the carbonization is performed at 800 to 1,100 ° C.
(6) The porous granular paper sludge carbonized fired product is an absolute dry weight, combustible content (including carbon): 15 to 25%, TiO ₂ : 0.5 to 3.0%, Na ₂ O: 0.00. _{0001~0.0005%, K 2 O: 0.0001~0.0005} %, SiO 2: 15~35%, Al 2 O 3: 8~20%, Fe 2 O 3: 5~15%, CaO: 15-30%, MgO: 1-8%, other (impurities): 0.5-3.0%, the total of these is 100%, the water absorption rate according to JISC2141 is 100-160%, BET adsorption method The specific surface area is 80 to 150 m ² / g and has open cells.
(7) The porous granular paper sludge carbonized fired product has a volume void ratio of 70% or more, a void volume of 1,000 mm ³ / g or more, an average void radius of 20 to 60 μm, and a total void volume of It is a mixed material having a spherical shape, an elliptical shape, a cylindrical shape or the like in which a void having a radius of 1 μm or more is 70% or more and a major axis is 1 to 10 mm, and is black.

According to the present invention, the following effects can be obtained.
(1) When an explosion accident occurs at a nuclear power plant reactor, radioactive materials such as iodine 131, cesium 134, and cesium 137 are released to the environment, or concentrated waste liquids and solids generated at nuclear power plants and radioactive material handling facilities. Radioactive waste, such as used ion exchange resin, is discharged into the environment, and soil is contaminated in a wide area. Here, spraying or mixing a porous granular paper sludge carbonized product made by carbonizing and firing paper sludge of a paper mill using both waste paper and wood chips alone or both waste paper and wood chips to radioactive material contaminated soil The radioactive material can be removed from the radioactive material contaminated soil. Furthermore, the radioactive substance concentration in radioactive substance-contaminated soil can be made equal to or less than 800 Bq / kg by repeating spraying and mixing of the porous granular paper sludge carbonized fired product and radioactive substance-contaminated soil.
(2) Even when agricultural fields, rice fields, etc. are contaminated with radioactive substances, by using the porous granular paper sludge carbonized fired products, vegetables and cereals are equivalent to the soil before radioactive substance contamination. Harvested to a degree. And a radioactive substance density | concentration becomes 0 or 500 Bq / kg or less, and people can consume vegetables and cereals safely.
(3) Even if the soil used in houses, schools, parks, roads, etc. is contaminated with radioactive materials, the use of carbonized calcined porous granular paper sludge in the soil contaminated with radioactive materials The radioactive substance concentration can be equal to or less than 800 Bq / kg. Thereby, people's health can be protected without adversely affecting people.
(4) Even when deserts, dry land, etc. are contaminated with radioactive substances, the repeated use of carbonized calcined porous paper sludge reduces the concentration of radioactive substances in the soil contaminated with radioactive substances, resulting in greening Or, it can be improved to soil suitable for arable land.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to these.

(1) Outline of removal method of radioactive material For example, waste paper, wood chips alone or both waste paper and wood chips are used in radioactive material contaminated soil contaminated with radioactive materials such as iodine 131, cesium 134, and cesium 137. Paper sludge discharged from a paper mill is calcined and fired without impregnating any one of potassium iodide (KI) and triethylenediamine (TEDA) and a mixture of KI and TEDA. Sprinkle the porous granular paper sludge carbonized fired product, stir in a cultivator and mix. As a result, the concentration of radioactive material contained in the radioactive material contaminated soil decreases with time. If fertilizers, insecticides, etc. for vegetables, cereals, flowers, etc. are needed, spray after at least 3 days have passed since the porous granular paper sludge carbonized fired material was mixed with radioactive material-contaminated soil. To do.

(2) Radioactive material-contaminated soil According to the Japan Society of Soil Fertilizer (http://jssspn.jp/info/secretariat/4317.html), cesium 137 has spread to the whole of the earth in the 1960s as a peak by atmospheric nuclear tests, It fell to the soil. For this reason, even today, cesium 137 is present in soils all over the world, albeit in trace amounts. The total value of cesium 134 and cesium 137 is 33 Bq / kg for normal field soil and 28 Bq / kg for rice field soil. On the other hand, for this measurement result, in the case of radioactive material contaminated soil contaminated with radioactive material released by an accident at a nuclear power plant, the low value is 800 Bq / kg, and the high value is several tens of thousands Bq / kg. . The concentration of radioactive material in the soil contaminated with these radioactive materials varies with the change in weather with time. Here, when these radioactive substance contaminated soil was processed with the porous granular paper sludge carbonized fired product, the result that the radioactive substance in radioactive substance contaminated soil was removed was confirmed.

(3) Application amount of carbonized calcined product of porous granular paper sludge The calcined product of porous granular paper sludge is 0.1-6 kg / m ² (0.5-50 kg / m ³ ) 6% by weight), preferably 1.0 to 3.5 kg / m ² (8 to ³⁰ kg / m ³ ) (0.9 to 3.3% by weight of dry soil) is an appropriate application amount, but radioactive material In order to remove radioactive substances in the contaminated soil, it is desirable that at least two weeks or more elapse.

(4) Presumed mechanism of removal of radioactive material in soil contaminated with radioactive material by porous carbonized paper sludge carbonized product (4-1) Hypothesis of Japan Society of Soil Fertilizer (http://jssspn.jp/info/secretariat) /4317.html)
According to the periodic table of elements, cesium is classified as the same alkali metal as sodium and potassium, and it is known that it behaves like these elements. Soil has a property of attracting and retaining cation cesium because it has negative charge. Furthermore, since clay minerals that trap cesium exist in the soil, cesium that infiltrates the soil is strongly held by the clay mineral and is difficult to separate.

(4-2) Research results of iodide impregnated activated carbon obtained by carbonizing and firing Munetake bamboo (Chien, CC, Huang, YP, Wang, WC, Chao, JH, Wei, YY) , 2011, Efficiency of Moso banbo charcoal and activated carbon for adsorbing radioactive iodine. Clean-Soil, Air, Water, 39 (2), 103-108).
In the above study, in order to confine the volatile radioactive iodine 131 by the iodide-added activated carbon obtained by carbonizing and firing the scorpion bamboo, the iodide is first adsorbed on the surface of the activated carbon, and then moves to the position of iodine ions, where A mechanism was proposed in which body exchange occurred. Further, the adsorptivity to the surface of the iodide-added activated carbon was greatly influenced by the alkali group on the surface of the activated carbon, for example, the hydroxyl group (OH ⁻ ) and the π electron system on the bottom surface of the activated carbon group. Alkali groups were said to enhance the electrostatic interaction between the surface of activated carbon and iodide (KI).

(4-3) Presumed mechanism that KI and TEDA are not impregnated in this embodiment The activated carbon used in nuclear power plants is included in exhaust gas during daily operation or released in the event of an accident such as an explosion It removes the concentration of iodine 131 to a safe level to prevent release to the environment. According to the above Regulatory Guide 1.52 of the US Nuclear Regulatory Commission, grain and coconut shells are used as the basic raw material for activated carbon. Furthermore, in order to enhance the ability to immerse radioactive iodine 131, these activated carbons are impregnated with a solution of either potassium iodide (KI) or triethylenediamine (TEDA) or a mixture of KI and TEDA. ing. Therefore, according to the Regulatory Guide 1.52 of the US Nuclear Regulatory Commission, it was found that contamination by radioactive cesium 134 and 137 discharged by a nuclear power plant accident was not assumed.

Grains and coconut shells, which are the basic raw materials for activated carbon, are mainly composed of cellulose, hemicellulose, and lignin. Before carbonization, about 95% is organic, and the remaining 5% is inorganic. After carbonization, the organic content is 80% and the inorganic content is 20%. (Ravenendran, K., Ganesh, A., Khilar, KC, 1996, Pyrolysis charactaristics of biomass components and Biomass components. Fuel, 75 (8), 987-998). In addition, the inorganic content of plants is generally a cationic metal. For this reason, in order to immerse a large amount of radioactive iodine 131, activated carbon consisting of cereals and coconut shells is impregnated in a solution of either potassium iodide (KI) or triethylenediamine (TEDA) or a mixture of KI and TEDA. It is necessary to make it.

  On the other hand, in the present embodiment, the organic content is less than 25% and the inorganic content is 75% or more, and the constituent ratio of the components is different from the activated carbon composed of the above-mentioned grains and coconut shells. In addition, most of the inorganic content of the present embodiment is a cation metal, and it is possible to immerse an anion of iodine or to exchange ions with a cation of cesium. Therefore, in the present embodiment, it is considered unnecessary to impregnate the carbonized fired product of the porous granular paper sludge with a solution of either KI or TEDA, or a mixture thereof.

(5) Properties of carbonized fired product of porous granular paper sludge The carbonized fired product of porous granular paper sludge contains the following properties. pH: 8.0 or more, desirably 10 or more, alkali equivalent value: 1.0 meq / g or more (NaOH), desirably 1.5 to 2.5 meq / g (NaOH), cation exchange capacity: 1.0 meq / 100 g or more (NH ₄ ⁺ ) desirably 1.5 to 3.0 meq / 100 g (NH ₄ ⁺ ), electric conductivity: 70 to 150 μS / cm, Na content: 0.0003% or more, K content: 0.0003% That's it.

Moreover, the following component is contained. Absolute dry weight, combustibles (including _{carbon): 15~25%, TiO 2:} 0.5~3.0%, Na 2 O: 0.0001~0.0005%, K 2 O: 0.0001 _{~0.0005%, SiO 2: 15~35%} , Al 2 O 3: 8~20%, Fe 2 O 3: 5~15%, CaO: 15~30%, MgO: 1~8%, others ( Impurity): 0.5 to 3.0% included. Moreover, the water absorption rate by JISC2141 is 100-160%, the specific surface area by a BET adsorption method is 80-150 m < ² > / g, and it has an open cell. Note that the total content of these components is 100%.

(6) for action of the present embodiment in which the porous particulate paper sludge carbonized baked product using an estimation mechanism for removing radioactive materials radioactive pollution in soil

The porous granular paper sludge carbonized fired product contains a large amount of SiO ₂ (15-35%) and Al ₂ O ₃ (8-20%), but the permanent negative charge from the isomorphous substitution of Al ³⁺ in Si ⁴⁺ is It is insignificant. Furthermore, many exchangeable cations are presumed to be extremely present on the alkaline (OH ⁻ ) surface of the calcined product of porous granular paper sludge. (Ma, C., Eggleton, RA, 1999, Cation exchange capacity of kaolinite. Clays and Cray Minerals, 47 (2), 174-180)

The exchangeable cation of the porous granular paper sludge carbonized fired product is Ca ²⁺ , Mg ²⁺ , K ⁺ , Na ⁺ or the like. The radioactive cesium adsorbed on the surface of the carbonized calcined product of porous granular paper sludge migrates to the position of calcium and magnesium cations that are extremely present on the alkaline (OH ⁻ ) surface of the calcined product of porous granular paper sludge. Wake up. Since the porous granular paper sludge carbonized product has a high cation exchange capacity and calcium and magnesium contents, it is considered that ion exchange with radioactive cesium occurs frequently, and as a result, the radioactive cesium is greatly reduced .

(7) Carbonization and calcination of porous granular paper sludge carbonization calcination Carbonization calcination is performed by granulating paper sludge having a moisture content of 50 to 85%, then spheronizing, drying, and then dry distillation temperature 500 to 1 in a reduction carbonization furnace. , 300 ° C., preferably 700 to 1,200 ° C. More preferably, it is performed at 800 to 1,100 ° C.

(8) Porous granular paper sludge carbonized calcined product, etc. The porous granular paper sludge carbonized calcined product has a volume porosity of 70% or more, a void volume of 1,000 mm ³ / g or more, and an average void radius. It is 20 to 60 μm, and voids having a radius of 1 μm or more in the entire void volume are 70% or more, and the major axis is 1 to 10 mm. Moreover, it is a mixed substance such as a spherical shape, an elliptical shape, and a cylindrical shape, and is black. Other shapes may also be used.

(9) Characteristic evaluation method of carbonized fired product of porous granular paper sludge (9-1) pH
Add 100 ml of boiling distilled water cooled to the same temperature as room temperature to 20 g of the porous granular paper sludge carbonized fired product, stir overnight, filter with a 2G4 glass filter, and measure the pH of the glass electrode The pH of the filtrate was measured.

(9-2) Alkali equivalent value Next, 10 ml of the above filtrate was taken and colorimetric titration was performed with 0.01N hydrochloric acid to calculate an alkali equivalent value.

(9-3) Cation Exchange Capacity 125 ml of 1M / L ammonium acetate solution was added to 25 g of the porous granular paper sludge carbonized calcined product, stirred for 1 hour, then left overnight, and filtered through a 17G4 glass filter. The residue was then slowly washed 4 times with 25 ml of 1 M / L ammonium acetate solution without cracking. Thereafter, the residue was washed slowly with 25 ml of 95% ethanol 8 times without cracking. Finally, the residue was washed slowly with 25 ml of 1 M / L potassium chloride solution 8 times without cracking, the filtrate was collected and made up to 250 ml with additional 1 M / L potassium chloride solution. 20 ml of this filtrate was taken and subjected to colorimetric titration with 0.01N hydrochloric acid to determine the cation exchange capacity.

(9-4) Quantitative determination of sodium and potassium To 1 g of porous granular paper sludge carbonized fired product, 100 ml of 0.1 M / L nitric acid solution was added, stirred for 72 hours, filtered through a 1G4 glass filter, Sodium and potassium were measured with an atomic absorption photometer.

(10) Quantification of radioactive substances in soil contaminated with radioactive substances Measurement of radioactive substances such as iodine 131, cesium 134, cesium 137, etc. Conforms to the Radioactivity Measurement Manual.

  Hereinafter, although the effect of the present invention is explained using an example, the present invention is not limited to these examples. The field test was conducted in Fukushima Prefecture. In the same prefecture, radioactive materials were detected in some soils due to the nuclear power plant accident in the Great East Japan Earthquake that occurred on March 11, 2011.

[Example 1]
(1) using a radioactive contaminated Soils Fukushima Iitate vineyard (area = 324m ^2), to of which 120 m ^2, a porous particulate paper sludge carbonization was 240kg sprayed and mixed with soil swirled in cultivators . Of the remaining 204 m ² , 144 m ² was used as blank soil. Potato pods were planted in radioactive material-contaminated field soil and blank soil mixed with carbonized calcined porous paper sludge. A space of 60 m ² was provided between these soils. Table 1 shows the measurement results of radioactive substances in the soil contaminated with radioactive substances.
In all the following examples, the porous granular paper sludge carbonized fired product is indicated as PSC.

When PSC was mixed with radioactive material contaminated field soil, the concentration of radioactive material increased at that moment. As explained above, this is thought to be due to the fact that the alkali (OH ⁻ ) group on the PSC surface enhances the interaction between the trapped radioactive material and the static electricity in the soil, and the radioactive material is adsorbed on the PSC surface. . It was found that the radioactive substance concentration in the radioactive material contaminated field soil decreased with time, and that PSC had the effect of reducing the radioactive substance. When based on the day when the potato camellia was harvested (day 73), the PSC removal capacity was 9,372 Bq / day / kg.

[Example 2]
(2) Radioactive material-contaminated rice field I soil Using rice field I (area = 495 m ² ) in Iitate Village, Fukushima Prefecture, PSC 600 kg was sprayed, stirred with a cultivator and mixed with soil. Rice was cultivated in this radioactive material contaminated rice field I. Table 2 shows the measurement results of radioactive substances in the radioactive substance-contaminated rice field I soil.

  Similar to the radioactive material-contaminated field soil in Example 1, the radioactive material-contaminated rice field I soil increased in concentration of radioactive cesium on the first day, but decreased with time, and the ability to remove PSC when based on the 66th day Was 7,466 Bq / day / kg.

[Example 3]
(3) Radioactive material-contaminated rice field II soil Using rice field II (area = 495 m ² ) in Iitate-mura, Fukushima Prefecture, 1,200 kg of PSC was sprayed, stirred with a cultivator and mixed with soil. Table 3 shows the measurement results of radioactive substances in the radioactive substance contaminated rice field II soil.

  Similar to the radioactive material-contaminated field soil in Example 1, the radioactive material-contaminated rice field II soil increased with the radioactive cesium concentration on the first day, but decreased with time, and the ability to remove PSC when based on the 66th day Was 6,440 Bq / day / kg.

[Example 4]
(4) Radioactive material-contaminated rice field III soil Using rice field III (area = 2,700 m ² ) in Minamisoma City, Fukushima Prefecture, 3,600 kg of PSC was sprayed and stirred with a cultivator to mix with soil. Rice was cultivated in this radioactive material contaminated rice field III. Table 4 shows the measurement results of radioactive substances in the radioactive substance contaminated rice field III soil.

  Unlike the radioactive material-contaminated soil (field, rice field I, II) of Example 1 to Example 3, the radioactive material-contaminated rice field III soil had a reduced radioactive material concentration from the beginning of mixing with PSC, but increased with time. . This is thought to be due to changes in the concentration of radioactive materials in the soil due to changes in weather such as rain. However, in any of the examples, it was confirmed again that PCS reduces the radioactive substance. The removal ability of PSC was 908 Bq / day / kg based on the 61st day in the radioactive material contaminated rice field III soil.

  Considering the results of the above examples, the concentration of radioactive material in the radioactive material contaminated soil varies depending on the location. Regardless of this, the concentration of radioactive material when the calcined porous granular paper sludge is mixed with the radioactive material contaminated soil. Decrease. The higher the initial radioactive substance concentration, the higher the radioactive substance removal ability of the porous granular paper sludge carbonized fired product.

  The present invention uses a porous granular paper sludge carbonized fired product in soils such as fields, rice fields, schools, parks, roads, and deserts that are radioactive material contaminated areas due to accidents at nuclear power plants and radioactive material handling facilities. An improved purification method for removing radioactive material is provided. According to the present invention, the radioactive granular material sludge carbonized fired material is sprayed on the radioactive material contaminated soil, and the radioactive material in the radioactive material contaminated soil is changed with the lapse of time with a simple operation of stirring and mixing with a cultivator. Is removed. As a result, cereals grow as usual, and therefore the present invention is an effective improved purification method for eliminating adverse effects on people's health and food.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the said embodiment. The present invention can be modified in various ways without departing from the scope of the claims.

Claims (6)

pH 8 or higher, alkali equivalent value 1.0 to 4.0 meq / g (NaOH), and cation exchange capacity 1.0 to 4.0 meq / 100 g (NH ₄ ⁺ ), organic content is less than 25%, inorganic content is 75% or in which the porous particulate paper sludge carbonization product, potassium iodide (KI), triethylenediamine (TEDA), or carbonizing the paper sludge without also impregnated with either a solution of a mixture of the KI and the TEDA To generate
Dispersing or mixing the porous granular paper sludge carbonized fired product on radioactive material contaminated soil, impregnating with iodine, or performing ion exchange with cesium ,
An improved purification method for soil contaminated with radioactive material. The radioactive material-contaminated soil contains a total concentration of cesium 134 and cesium 137 of 800 Bq / kg or more.
The improved purification method for radioactive material-contaminated soil according to claim 1. The amount of the porous particulate paper sludge carbonization product diffuses or mixed with the radioactive substance contaminated soil is 0.1~6kg / m ^2,
The method for improving and purifying radioactive material-contaminated soil according to claim 1 or 2, characterized in that: The paper sludge has a moisture content of 50 to 85%, and after granulating and drying the paper sludge, it is carbonized and fired in a reducing carbonization furnace having a dry distillation temperature of 500 to 1300 ° C.
The method for improving and purifying radioactive material-contaminated soil according to any one of claims 1 to 3. The calcined product of the porous granular paper sludge is absolutely dry weight, combustible content (including carbon): 15 to 25%, TiO ₂ : 0.5 to 3.0%, Na ₂ O: 0.0001 to 0 _{.0005%, K 2 O: 0.0001~0.0005} %, SiO 2: 15~35%, Al 2 O 3: 8~20%, Fe 2 O 3: 5~15%, CaO: 15~30 %, MgO: 1 to 8%, the sum of these and impurities is 100%, the water absorption is 100 to 160%, the specific surface area by the BET adsorption method is 80 to 150 m ² / g, Have
The method for improving and purifying radioactive material-contaminated soil according to any one of claims 1 to 4. The carbonized calcined porous paper sludge has a volume porosity of 70% or more, a void volume of 1,000 mm ³ / g or more, an average void radius of 20 to 60 μm, and a radius of 1 μm in the total void volume. The above void is 70% or more, and the mixed material is spherical, elliptical, cylindrical with a major axis of 1 to 10 mm, and is black.
The method for improving and purifying radioactive material-contaminated soil according to any one of claims 1 to 5, wherein: