RU2428249C2 - Granulated nanosorbent and method of its production - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to sorbents containing nanostructure elements and may be used for treatment of fluids with technogenic impurities. Sorbent comprises the following components in wt %: bentonitic clay -10-40, glauconite - 10-50, thermally expanded carbon - 10-60. Proposed method comprises mixing initial components, adding water to produce plastic mass, granulating said mass, and thermal treatment of produced granules. Note here that thermal treatment comprises drying granules by infrared radiation at 70-150°C and SHF-heating of granules placed in quartz ceramic casing to 1000°C.

EFFECT: reduced power consumption, higher performances.

8 cl, 1 dwg

Description

The group of inventions relates to methods and technologies for producing sorbing substances containing nanostructured elements, can be used in the purification of aqueous media from industrial pollutants (heavy metals, petroleum products, organics, pesticides, radionuclides, etc.). When implementing the proposed method receive granular nanosorbent, which is intended for use as a filtering and sorption filling, capable of replacing activated carbon, anionic-cationic resins, reverse osmosis membranes, etc.

Known methods for producing carbon sorbents based on the processing of carbon-containing raw materials (for example, peat) with subsequent granulation (Mukhin V.M., Tarasov A.V., Klushin V.N. Active coals of Russia. - M .: Metallurgy, 2000, 352 p. .). The resulting sorbents, for example, activated carbon brand SKT, are characterized by low adsorption capacity and mechanical strength.

A known sorbent and method for producing inorganic sorbents based on zirconium dioxide in granular form, which consists in the fact that the sol of hydrated zirconia (GDC) containing 2-35 mol. % alumina with respect to zirconia, is dispersed dropwise into an ammonia solution, the obtained granules are washed with water and dried at 100-900 ° C for 6 hours. The introduction of alumina into zirconia in an amount of 2-35 mol leads to a significant (almost ten times) an increase in mechanical strength at high drying temperatures (RF patent for the invention No. 1293892).

The known method allows to obtain spherical granules GDC with high mechanical strength at 200-900 ° C, which makes it possible to use sorbents in high-temperature cleaning processes. The mechanical and thermal properties of the obtained sorbent granules meet the requirements for catalysts and sorbents operating at high temperatures. However, the use of zirconium dioxide as one of the starting components significantly increases the cost of the final product, which negatively affects its consumer qualities.

A known method of producing a granular sorbent, comprising mixing a base, for example a zeolite, with a basic aluminum salt pre-heated to 30-105 ° C as a binder, molding the mass, drying and heat treatment of the obtained granules. Sorbents obtained as a result of applying the known method have high parameters of bulk and apparent density, and also have lower total porosity (AS USSR No. 494183).

However, for the implementation of the known method requires significant energy consumption, due mainly to the duration of the heat treatment of the granules, which leads to an increase in the cost of the final product.

A known method of producing granular aluminosilicate sorbents, including mixing solutions of water glass and sodium aluminate, crystallization, washing the obtained hydrogel from excess alkali, granulation and treatment with an alkaline solution, while the granular hydrogel is further subjected to treatment with 1-5% aluminum sulfate solution, followed by exposure to the solution ammonia and washing with distilled water (a.s. USSR No. 835956).

The known method is technologically difficult to implement, requires the presence of certain chemicals, which in turn also negatively affects the price characteristics of the final product.

Known granular sorbent containing thermally expanded graphite (20-90 wt.%) And a component from the clay class (2-20%), as well as a method for its production, which consists in mixing thermally expanded graphite and clay, molding a mixture (US patent No. 5607889).

The closest in technical essence to the claimed group of inventions is a granular sorbent and a method for its production, implemented when the installation for granulating glauconite. The sorbent contains glauconite and a binder - a zirconium dioxide sol. The method consists in the following: the glauconite mined in the field is dried using a drying device, sieved, quartz impurities are removed, then sieved again, separating fractions of less than 40 microns. Larger fractions are returned for re-grinding. As a binder, a sol of zirconia with a concentration of 1.3 mol / L or an aluminophosphate sol of the same concentration is used. Glauconite concentrate with a fraction of less than 40 microns, a sol of zirconium dioxide with a concentration of 1.3 mol / l and water in a ratio of 1.75: 0.5: 0.5 or an aluminophosphate sol in a ratio of 1.75: 1.0 are placed in a mixer and produced mixing them for 10-15 minutes until a homogeneous mass with a moisture content of 32-34% is obtained. The homogenized mass is granulated using a screw granulator to obtain granules in the form of cylinders or balls 2 mm in diameter. The obtained granular material is dried at a temperature of 100 ° C for 1 hour. After drying, the obtained granules are calcined for 3 hours at a temperature of 400 ° C (using a zirconia sol) or at a temperature of 600 ° C (in the case of using aluminophosphate sol). During firing, green earth changes color from dark green to brown. The obtained calcined granules are cooled, for which they are subjected to blowing (RF patent for utility model No. 71562).

When implementing the known method, a significant amount of electricity is consumed, and the use of a zirconia sol as a binder in combination with the energy expended increases the cost of the final product many times, which is economically disadvantageous, especially when organizing industrial production.

The objective of the claimed group of technical solutions is to create an economical method for producing a complex granular nanosorbent, characterized by high filtering and sorption filtration properties, based on thermally expanded carbon.

The technical result that can be obtained using the claimed group of inventions is the optimal qualitative and quantitative selection of the starting components, providing the maximum filtering and sorbing effect of nanosorbent.

The problem is solved in that the granular nanosorbent, including glauconite and a binder, additionally contains thermally expanded carbon according to the technical solution, and bentonite clay as a binder, with the following ratio of components, wt.%: Bentonite clay - 10-40, glauconite - 10- 50, thermally expanded carbon - 10-60. In addition, in the method for producing granular nanosorbent, which includes mixing the sorbent starting components followed by adding water to form a plastic mass, granulating the mass, heat treating the obtained granules with their subsequent cooling, according to the technical solution, bentonite clay, thermally expanded carbon and glauconite in the following ratio of components, wt.%: bentonite clay - 10-40, glauconite - 10-50, thermally expanded carbon - 10-60. Granulation of the mass is carried out to obtain spherical granules with a diameter of 0.5-3 mm or to obtain cylindrical granules with a diameter of 0.5-3 mm and a height of not more than 7 mm. Heat treatment includes drying granules with infrared radiation at a temperature of 70-150 ° C and microwave heating of granules previously placed in a closed thermally insulating volume of quartz ceramic to a temperature of 1000 ° C. During microwave processing, the granules are preliminarily placed in a closed thermally insulating volume, while overpressure of an inert gas in the closed volume is created, replacing the atmospheric air and residual moisture contained in the processed granules with an inert medium. The granules are cooled by blowing with an air stream at a temperature of 15-25 ° C. In the case of the manufacture of cylindrical granules after heat treatment, they are crushed, followed by sieving to isolate fractions of granules with a size of at least 0.5 mm.

The group of inventions is illustrated by the drawing, while the drawing shows a block diagram of a device with which the inventive method is implemented.

The positions in the drawing indicate:

1. hopper for glauconite;

2. hopper for bentonite clay;

3. hopper for thermally expanded carbon;

4. water tank;

5. mixer;

6. granulator;

7. infrared (IR) drying device;

8. device for firing microwave radiation;

9. cooling device;

10. filling device.

The method is as follows.

Glauconite, bentonite clay and thermally expanded carbon are used as starting components in the preparation of nanosorbent.

Glauconite in its natural structure is a greenish mineral. It is a clay mineral of variable composition with a high content of ferrous and trivalent iron, calcium, magnesium, potassium, phosphorus, and it also contains more than twenty trace elements, including copper, silver, nickel, cobalt, manganese, zinc, molybdenum, arsenic, chromium, tin, beryllium, cadmium and others. All of them are in easily removable form of exchangeable cations, which are replaced by elements in excess in the environment. This property, as well as the layered structure, explains the high sorption properties in relation to oil products, heavy metals, radionuclides. At the same time, glauconite is characterized by a low percentage of desorption (removal from liquids or solids of substances absorbed by adsorption or absorption) and prolonged action, high heat capacity, ductility, etc. Glauconite is characterized by high ion exchange capacity (up to 15 ... 20 mEq per 100 g of rock) and specific surface (up to 120 m ² / g), and as a result - a very significant absorption capacity. Being strong sorbents, glauconites absorb and transform into a state of inaccessible for plants salts of heavy metals and radionuclides (cesium-137 and strontium-90) contained in the soil.

Bentonite clay used as a binder in the preparation of nanosorbent is clay containing at least 70% of the mineral of the montmorillonite group. Montmorillonite is a highly dispersed layered aluminosilicate in which due to non-stoichiometric substitutions of cations of the crystal lattice an excess negative charge appears, which is compensated by exchange cations located in the interlayer space. This is due to the high hydrophilicity of bentonite clay. When bentonite is mixed with water, it penetrates into the interlayer space of montmorillonite, hydrates its surface and exchange cations, which causes the mineral to swell. With further dilution with water, bentonite forms a stable viscous suspension with pronounced thixotropic properties. Montmorillonite has high cation exchange and adsorption properties.

The last component used in the manufacture of nanosorbent is thermally expanded carbon, for example, high reactivity carbon (UWRS) obtained from layered carbon compounds by V. I. Petrik (patent for invention No. 2163883) can be used. USRM is chemically inert, electrically conductive, hydrophobic (contact angle of contact more than 90 degrees), resistant to aggressive environments, environmentally friendly. The carbon content is not less than 99.4%, bulk density - 0.01-0.001 g / cu. cm (depending on the manufacturing method). SPMR effectively reduces the amount of many cations, including copper (30 times), iron (3 times), ammonium (2-3 times), vanadium (5 times), manganese (2 times), phosphates (in 35 times), organic and inorganic anions, including sulfides (6 times), fluorides (5 times), nitrates (3 times), reduces the concentration of suspended particles by more than 100 times. When wetted, the UVR forms a mass with enormous hydraulic resistance, which is much higher than, say, activated carbon. In this mass, as in a very tightly woven network, even the smallest suspensions are "entangled" - purely mechanically. This means that the mass of the SPMW with a thickness of several centimeters works not only as a sorbent, retaining impurities using unsaturated interatomic carbon bonds, but also as a filter, purely mechanically retaining even the smallest impurities and suspensions. However, in addition to UWR, thermally expanded carbon of any other structure obtained as a result of the effect of the thermal expansion mechanism on graphite can be used.

All components necessary for the manufacture of nanosorbent are placed in powdered form in powdered storage tanks 1-3, equipped with dispensers. Glauconite, bentonite clay and thermally expanded carbon in powder form are mixed, while adding the necessary amount of water. The components are dosed into the mixer in the following ratio: glauconite 10-50%, bentonite clay 10-40%, thermally expanded carbon 10-60%. The ranges of percentages of the components are determined by the expected conditions for the use of nanosorbent and the required degree of filtration and sorption. So, for example, for filtration and sorption of heavy metals, the starting components are metered and mixed in the following ratio: glauconite 50%, bentonite clay 30%, thermally expanded carbon 19%, water 1%, and for filtering and sorption of oil products in the following ratio: glauconite 30 %, bentonite clay 30%, thermally expanded carbon 39%, water 1%. When solving water purification problems, various combinations of initial components are also possible. For example: for softening technology, the components are mixed in the following ratio: glauconite 40%, bentonite clay 20%, thermally expanded carbon 38%, water 2%,

to ensure sorption - glauconite 45%, bentonite clay 25%, thermally expanded carbon 27.5%, water 2.5%,

for deferrization - glauconite 30%, bentonite clay 15%, thermally expanded carbon 37%, water 3%.

Water is added in the process of mixing the components in such an amount as to ensure the formation of a plastic mass of plasticine consistency. For example, when mixing 500 g of dry starting components, about 15-16 g of water is added. Mixing is carried out in automatic mode, determining the readiness of the plastic mass visually. The thermally expanded carbon is used in a state finely divided to a finely divided fraction, and the fraction is such that the fraction of bentonite clay and glauconite is several times larger than the thermally expanded carbon fraction. When mixed with other starting components, thermally expanded carbon covers the fractions of bentonite clay and glauconite, thereby increasing the specific surface area and, hence, the sorption capacity of nanosorbent. Thus, by mixing the starting components (glauconite, bentonite clay and thermally expanded carbon) and water, a plastic mass is obtained, which is then subjected to granulation. The shape and size of the granules are also determined by the required filtration and sorption parameters of the resulting nanosorbent. Cylindrical granules are obtained with a diameter of 0.5-3 mm and a height of not more than 7 mm, and spherical granules with a diameter of 0.5-3 mm. Granulation is carried out, for example, using a horizontal single screw extruder. At the end of the granulation process, the entire plastic mass is divided into granules of a certain shape and size containing water and air. In order to dry the nanosorbent granules, that is, to remove excess moisture and air, they are subjected to heat treatment, which includes two stages. During the first stage, the granules are dried by infrared radiation at a temperature of 70-150 ° C for 5-10 minutes. It is characteristic of infrared radiation that thermal radiation, similar to ordinary light, is not absorbed by air, so all the energy from the device without loss reaches the heated object. As a result of drying the granules by means of infrared radiation, granules containing a residual moisture content of 30-50% are obtained. Then the granules are subjected to more intense and faster heat treatment, which is realized, for example, by microwave heating of the granules. For microwave heating, the granules are placed in a closed thermally insulating volume made of quartz ceramics and equipped with fittings that allow feeding inert gas into the granule placement zone, which replaces atmospheric air and moisture evaporating as a result of thermal exposure. Argon or nitrogen is used as an inert gas, with the molecules of which the carbon, which is part of the nanosorbent granules, does not react and, as a result, remains in the thermally expanded form of the granules. The radiation frequency of the microwave device is 2450 MHz, power from 1 to 10 kW. The granules are subjected to microwave irradiation for 1-3 minutes at a temperature of 700-1000 ° C. The moisture remaining in the granules evaporates, forming the porosity of the granule structure, which contributes to an increase in its specific surface, and, hence, sorption capacity. At the end of the heat treatment, the granules are cooled to ambient temperature by blowing with a directed air flow.

When granulating the plastic mass into cylindrical granules after calcining and cooling, they are crushed and sieved to separate a finer (less than 0.5 mm) fraction.

Thus, as a result of the implementation of the proposed method, a nanosorbent granular in the form of cylindrical or spherical granules is obtained, containing glauconite, thermally expanded carbon and bentonite clay as initial components as a binder starting component. The percentage ratio of the components that make up the inventive nanosorbent is determined by the scope of its application and the necessary filtration and sorption characteristics.

An example of a specific implementation.

The inventive method is implemented upon receipt of nanosorbent used in the purification of drinking water as part of the filter load of a household filter.

As the initial components used: bentonite clay - 30%, glauconite - 30%, thermally expanded carbon - 39%. With this ratio of components for the preparation of nanosorbent used 1% water. To obtain nanosorbent, the starting components were mixed until a homogeneous plastic mass capable of granulation was obtained. After mixing, the mass is granulated, giving a spherical shape to granules with a diameter of 2 mm, and subjected to infrared radiation and microwave heating at a temperature of 700 ° C for 1 minute, after which it is cooled to a temperature of 25 ° C. Chilled nanosorbent granules are packed for further sale.

Claims (8)

1. Granular nanosorbent, including glauconite and a binder, characterized in that it additionally contains thermally expanded carbon, and as a binder, bentonite clay, in the following ratio of components, wt.%: Bentonite clay - 10-40, glauconite - 10-50, thermally expanded carbon - 10-60. 2. A method of producing granular nanosorbent, including mixing the starting components with subsequent addition of water to form a plastic mass, granulating the mass, heat treatment of the obtained granules with their subsequent cooling, characterized in that bentonite clay, thermally expanded carbon and glauconite are used as starting components in the following the ratio of components, wt.%: bentonite clay - 10-40, glauconite - 10-50, thermally expanded carbon - 10-60, while the heat treatment includes drying g wound with infrared radiation at a temperature of 70-150 ° C and microwave heating of granules previously placed in a closed thermally insulating volume of quartz ceramics, to a temperature of not more than 1000 ° C. 3. The method according to claim 2, characterized in that the granulation of the mass is carried out to obtain spherical granules with a diameter of 0.5-3 mm 4. The method according to claim 2, characterized in that the granulation of the mass is carried out to obtain cylindrical granules with a diameter of 0.5-3 mm and a height of not more than 7 mm 5. The method according to claim 2, characterized in that the cooling of the granules is carried out by blowing air with a temperature of 15-25 ° C. 6. The method according to claim 4, characterized in that after the heat treatment, crushing of the cylindrical granules is carried out, followed by screening to isolate fractions of granules with a size of at least 0.5 mm. 7. The method according to claim 2, characterized in that the microwave heating of the granules previously placed in a closed insulating volume is carried out in an inert gas atmosphere. 8. The method according to claim 7, characterized in that nitrogen or argon is used as an inert gas.

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