Resulting sorbent for purification of liquid wastes from radionuclide ions of non-ferrous and heavy metals and method thereof

 

The invention relates to zeolites derived from anthropogenic aluminosilicate raw materials, particularly components of volatile ashes of thermal power plants, and can be used in nuclear power and chemical-metallurgical industry for the purification of liquid radioactive waste and wastewater from radionuclides, ferrous ions and heavy metals. For the synthesis of the resulting sorbent use of cenospheres, ceramic selected from volatile ashes from the combustion of coal. Pre-composition of cenospheres stabilize by their separation by size, density and magnetic properties. Cenospheres, ceramic mixed with a solution of NaOH with a concentration of 1-3 M and maintained at 80-100oWith over 32-72 h in static conditions or under stirring. The sorbent contains one or more type zeolites NaX, NaA, or NaPl, which can be located both on the outer and on the inner surface of the hollow microspherical media with a diameter of 400 μm. Exchange capacity of the obtained sorbent in respect of cesium and strontium is 2 mEq/g of sorbent, a Ni, Cu, Cr, Co, Cd, Hg, Zn - about 1 mEq/g 2 s and 6 C.p. f-crystals, 2 ill., 3 table.

The invention relates to zeolites obtained from man-made al the ANO in the nuclear power and chemical-metallurgical industry for the purification of liquid radioactive waste and wastewater from radionuclides ions of non-ferrous and heavy metals.

One of the many uses of fly ash from combustion of coal is the synthesis on the basis of zeolites, which are used as sorbents for the extraction of cesium and strontium from radioactive waste and wastewater treatment for removing ammonium ions, non-ferrous and heavy metals [1-6]. The closest to the claimed invention are zeolite sorbents obtained by zeolitization fly ash according to the methods [4-6] , which is based on the interaction of fly ash with sodium hydroxide solution or potassium hydroxide under hydrothermal conditions. At the same time from the same source of raw materials depending on polyarnosti activating solution, the ratio fly ash/activating solution, temperature, pressure and reaction time receive about 13 types of zeolites with the content of the target component 20-75%, among which the most open structure and optimal cation exchange properties of zeolites NaA, NaX and NaPl. A significant drawback of these methods is the use of aluminosilicate raw materials variable chemical and mineral phase composition, which leads to non-reproducible results, and pollution target is rsny material with a grain size from 1 to 5 μm, that require additional molding with a bonding material.

The aim of the invention are resulting type zeolites NaA, NaX and/or NaPl on the glass floor media with a diameter of 400 μm. Another objective of the invention to provide a zeolite sorbent containing zeolites of type NaA, NaX and/or NaPl in the form of hollow spherical pellets without a binder material.

This goal is achieved by the fact that as a feedstock for the synthesis of zeolites using cenospheres, ceramic selected from volatile ashes from the combustion of coal. Pre-composition of cenospheres stabilize by their separation by size, density and magnetic properties. Cenospheres, ceramic mixed with a solution of NaOH with a concentration of 1-3 M and maintained at 80-100oWith over 32-72 hours under static conditions or under stirring.

The essence of the claimed invention is as follows. Cenospheres, ceramic, or hollow aluminosilicate microspheres are one of the varieties of microspherical glass-ceramic components of volatile ashes of thermal power plants, differing from the rest mass of ash low density (less than 1.0 g/cm3), larger sizes of spherical granules (50-400 μm), and chemical and myservlets of lost ash by gravity separation of ash in the aquatic environment, removal of emergent faction and its dehydration. Despite the fact that the content of cenospheres in fly ash is typically less than 1.5%, the resources of this material, accumulated in lagoons lagoons are large enough that allows to consider them as available and relatively cheap aluminosilicate raw materials for the one-step of obtaining a molded zeolites unique microspherical design, characterized by the presence of internal cavities. Depending on the conditions of synthesis of crystallization of zeolites may occur outside of cenospheres, and on the inside of their shells with maintaining a smooth outer side, which makes these sorbents are more resistant to abrasion during operation.

Gross chemical composition of cenospheres produced by the combustion of coals of different swimming pools, according to [7] varies within a wide range (wt.%): SiO2- 53-64,7; Al2About3- 20-35,7; Fe2O3- 1,54-6,37; FeO - 0,57-5,09; CaO - 0,11-4,89; MgO - 0,01-2,64; MnO - 0,03-0,06; K2On - 0,44-7,18; Na2O - 0,4-1,36; P2O5of 0.07 to 0.75; SO3- 0,06-2,46; p. p. p. - 0,22-10,86. At the same time, cenospheres, ceramic with different thermal power plants burning coal of the same basin, for example Kuznetsk, are characterized by close>O3- 4,2-5,1; Sa - 0,9-2,1; MgO - 1,0-2,6; K2O - 2,3-4,0; Na2About - 0.5 to 1.2. Further stabilization of chemical and granulometric composition can be carried out by separation of cenospheres in size, density and magnetic properties [8, 9], thus there is a separation with high iron content (10-20 wt. % (based on Fe2O3). For cenospheres separated from the volatile ashes from the combustion of Kuznetsk coal, the molar ratio of SiO2/Al2About3the greater part of cenospheres stabilized composition is in the range of 2-6, which corresponds discocrappy zeolites, including zeolite NaA, NaX and NaPl.

In Fig.1 shows a spherical pellet sorbent with a diameter of about 200 microns with external crystals of zeolites NaX and NaPl.

In Fig.2 - spherical granules of adsorbent diameter 200-160 μm with a smooth external surface and the internal arrangement of the crystals of the zeolite NaPl.

The invention is demonstrated by the following examples.

Examples 1-3. For the synthesis of zeolites using cenospheres, ceramic stabilized composition resulting from the separation of the light fraction of the fly ash from the combustion of Kuznetsk coal (concentrate cenospheres) granulometric methods classify a glass and pour the NaOH solution of a given concentration, then Teflon glass installed in the heat chamber and incubated under static conditions at a temperature and for a time specified in the table.2. Then the reaction products washed with distilled water and dried at a temperature of 120oC. the Composition of the obtained products are shown in table.2. In Fig.1 shows a micrograph resulting zeolite sorbent obtained under these conditions (according to the scanning electron microscopy).

Examples 4-6. The addition of cenospheres stabilized composition (table.3), selected as in examples 1-3, placed in a Teflon beaker and pour the NaOH solution of a given concentration, then Teflon glass installed in the heat chamber and incubated under stirring at a rotating platform with a speed of 30 rpm at a temperature and for a time specified in the table.2. Then the reaction products washed with distilled water and dried at a temperature of 120oC. the Composition of the obtained products are shown in table.2. In Fig.2 shows the micrograph resulting zeolite sorbent (according to scanning electron microscopy (SEM) obtained under these conditions.

The possibility of implementing the claimed invention is not limited to the conditions described is Olya such a product, as hydrosolidarity (HySod). Increasing the exposure time leads to recrystallization of zeolites and changing the composition of the products. In addition, obtaining spherical granules of larger size (up to 400 µm) can be achieved through the use of cenospheres of appropriate diameter.

For the obtained zeolite sorbents were measured equilibrium ion exchange capacity ratio of cations, cesium and strontium, as well as some non-ferrous and heavy metals. So, depending on the composition of the initial solution capacity of sorbents for Cs and Sr up to 2 mEq/g of sorbent, and Ni, si, Cr, Co, Cd, Hg, Zn is 1 mEq/g of sorbent, which corresponds to the known data [6].

Thus, these examples suggest the possibility of playing for producing granulated zeolites defined types (NaA, NaX, NaPl) in microspherical form without the introduction of a binding material size up to 400 mm due to the use in the synthesis of hollow aluminosilicate microspheres from volatile energy ash.

Sources of information 1. GB 2339774, 2000. Synthesis of faujasite Y-type zeolite from fly ash. C 01 39/24.

2. JP 03-45512, 1997. Production of zeolite from fly ash. C 01 B 33/34.

3. JP 03-40915, 1991. Production of pellet-shaped zeolite from fly ash. C 01 B 33/34.

4. Hollman G. G. , Steenbruggen G., Janssen-Jurkovicova, M. A two-step process for the synthesis of zeolites f5.

6. Querol X. , Umana J. C., Plana F., et al. Synthesis of zeolites from fly ash at pilot plant scale. Examples of potential applications /Fuel 80 (2001) 857.

7. Kiselstein J. L., Oaks, I. C., Specplus A. L., Parada, S., Components ashes and slags from TPPs. - M.: Energoatomizdat, 1995. - 176 S.

8. Vereshchagin T. A., Ansic N. N. etc. the Receipt of cenospheres of volatile ashes stable composition and their properties /Chemistry for sustainable development 9 (2001) 379.

9. RF application 2001112067, priority dated 03 may 2001 Method of separation of cenospheres of volatile ashes of thermal power plants. 03 IN 5/64 IN 07 IN 4/02.

Claims

1. Sorbent for purification of liquid wastes from radionuclide ions of non-ferrous and heavy metals on the basis of the components of volatile ashes from the combustion of coal containing one or more zeolites selected from a number of NaX, NaA and NaPl, wherein the zeolites are in the matrix of the hollow microspherical media with a diameter of 400 microns.

2. The sorbent under item 1, wherein the zeolites are located mainly on the outer surface of the hollow microspherical media.

3. The sorbent under item 1, wherein the zeolites are predominantly located on the inner surface of the hollow microspherical media.

4. A method of producing a sorbent under item 1, including the sodium, characterized in that use light fraction of fly ash with a density less than 1 g/cm3, mainly containing cenospheres, ceramic.

5. The method according to p. 4, characterized in that the cenospheres, ceramic mixed with 1-3 M sodium hydroxide solution and maintained at 80-100oWith over 32-72 hours

6. The method according to p. 5, characterized in that the synthesis is carried out in static conditions.

7. The method according to p. 5, characterized in that the synthesis is carried out under stirring.

8. The method according to p. 4, characterized in that the composition of cenospheres stabilize by their separation by size, density and magnetic properties.

 

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