RU2731706C1 - Porous block filter material for complex purification of drinking water and a method for production thereof - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to porous block filtration material for complex purification of drinking water. Filter material contains activated carbon and polymer binder. Filter material comprises activated carbon fine particles with size of 0.05–0.1 mm, a specific surface area of filter 800 m²/g, an iodine number of 800 mg/g and a static exchange capacity for copper of 0.7 mg-eq/g with following ratio of components, wt%: activated carbon 80–95, polymer binder 5–20 with pore size 5–40 mcm. Filter material is obtained by extrusion or hot pressing of mixture of powdered material with particle size of 0.05–0.1 mm from activated carbon with specific filtration surface from 900 m²/g, with an iodine value of 900 mg/g, a static copper exchange capacity of 0.8 mg-eq/g, with water content of 2–6 % and a polymer binder, and the process is carried out at a compression ratio of mixture of 12–15 % and temperature of 10–40 °C is higher than softening point of polymer binder at ratio of activated carbon : polymer binder 80–95:5–20 wt%. Porous block material is made in the form of plates, hollow bodies or granules with size of 0.3–2.0 mm. Polymer binder contains polymers from classes of polyolefins and/or polyesters and/or copolymers thereof with a melt index of 2–20 g/10 min according to ASTM D 1238 at 190 °C and load 25 kg. Porous block material is intended for use as part of pressure and gravity filter cartridges for complex purification of drinking water.

EFFECT: providing complex high-efficiency treatment of drinking water both from chlorine and organochlorine compounds and heavy metals at level of 96–99 % over a considerable consumer resource with simple technology of obtaining it.

5 cl, 2 dwg, 1 tbl, 5 ex

Description

The invention relates to filter materials, in particular, to a porous block filter material for the complex purification of drinking water and to a method for its production. The proposed porous block filter material is intended for use as part of pressure and gravity type filter cartridges used for complex purification of drinking water and can be used to improve the quality of purification of drinking water by such filters. At present, household filters for purifying drinking water from the most common toxic pollutants: chlorine, organochlorine compounds and heavy metals are widely used among the population. Water purification from all of the above pollutants is a comprehensive purification of drinking water.

In filter cartridges for the complex purification of drinking water, either granular and fiber sorbents or porous block filter materials obtained by hot pressing of mixtures of finely dispersed sorbents in the form of powders and / or finely divided fibers with a polymer binder are used as filter materials individually or in the form of mixtures. In this case, activated carbon is usually used as sorbents, which effectively removes chlorine and organochlorine compounds from water, and ion exchange resins, zeolites, aluminosilicates, silica gels, aluminum oxide, zirconium dioxide, etc., which purify water from heavy metals. Porous block filter materials, in comparison with granular or fiber sorbents, have a number of functional advantages, among which the most significant are the consistently high efficiency of water purification throughout their entire service life. This is due to the absence of voids and cracks in its volume, the formation of which is characteristic of granular or fiber sorbents when air bubbles emitted from the purified water pass through them, and through which part of the purified water passes without contact with sorbent granules, which impairs the quality of water purification in the process resource development. Another advantage of porous block filter materials is the absence in the purified water, especially in the initial period of filtration, of the smallest particles of sorbent materials, which, due to their small size, are not retained by fiber materials and mesh of filter cartridges with granular sorbents.

From the prior art porous block filter materials for filter cartridges are known, made in the form of cylindrical or other shaped carbon blocks, which are made from a mixture of fine coconut activated carbon and a polymer binder (US patents 6524477, 1997; WO 2002041970 2002; WO 2012122185, 2012). Such materials contain powdered activated carbons with a particle size of 60-80 microns and a binder in the form of a finely dispersed polymer (high-density or ultra-high molecular weight polyethylene, polypropylene, nylon, ethylene-vinyl acetate copolymer, etc.) with an activated carbon: polymer binder ratio of 1: 1 - 5: 1 by weight. Such materials are produced by extrusion, coextrusion or hot pressing methods. The presence of finely dispersed activated carbon with a larger filtration surface area in comparison with a relatively small filtration area of granular coals provides highly efficient sorption of chlorine and organochlorine compounds from the water being purified over a purification resource that exceeds the purification resource of cartridges with granular sorbents.

To ensure the purification of water from heavy metals (as a rule, lead, mercury, copper, etc.), in addition to activated carbon and a polymer binder, 20-60 wt. % fine sorbents of heavy metals or in the form of powdered inorganic materials - zeolites, aluminosilicates, silica gels, aluminum oxide, zirconium dioxide, etc. (patents US 20060000763, 2006; US 200301969603, 2003; WO 2005070182, 2005; US 6207264, 2001; US20150041390 , 2015), or cation-exchange materials in the form of crushed cation-exchange fibers or granular cation-exchange resins (patents RU 2282494, 2006; US 200301969603, 2003; US 200110042298, 2009; RU 2709315, 2019). The presence of a combination of activated carbon and a sorbent of heavy metals in the composition of porous block materials provides a comprehensive purification of water from chlorine, organochlorine compounds and heavy metals.

The closest to the claimed porous block filter material is the porous block material of the gravity filter cartridge (patent RU 2709315 C1, 2019). A porous block material is obtained by compressing a mixture of powdered initial components with heating, containing particles of activated carbon, a sorbent of heavy metals (inorganic sorbents from the classes of zeolites, aluminosilicates, silica gels, aluminum oxide, zirconium dioxide, and / or organic sorbents based on cation exchange resins and fibers) and a polymeric binder at a ratio of activated carbon: sorbent of heavy metals: polymeric binder 30 - 70:10 - 70: 5 - 20 wt. %, which ensures the efficiency of water purification from copper and lead from 92 to 98% during the resource of 350-450 liters.

However, the known porous block material, providing a high efficiency of water purification from heavy metals, does not provide a sufficiently high efficiency of water purification from chlorine and organochlorine compounds: this indicator decreases in comparison with a porous block material made from a mixture of powdered materials from activated carbon and a polymer binder. described in the same patent, from (92-96)% to (88-91)%, which is due to a decrease in the content of activated carbon in the mixture, which is a sorbent of chlorine and organochlorine compounds. In addition, the introduction of an additional finely dispersed heavy metal sorbent into the composition of a porous block material, in addition to activated carbon and a polymer binder, complicates the manufacturing technology of such a material, since it requires the introduction of additional stages of grinding, fractionation, dosing of the heavy metal sorbent and homogeneous mixing of a mixture of three components.

The technical objective of the present invention is to create a porous block material for the complex purification of drinking water, providing at the same time highly efficient water purification from chlorine, organochlorine compounds and heavy metals while providing a simple technology for its manufacture, and the development of a method for its production. The set technical problem is achieved by the proposed porous block filter material for the complex purification of drinking water, containing fine particles of activated carbon with a specific filtration surface from 800 m ² / g, iodine number from 800 mg / g, static exchange capacity for copper from 0.7 mg - eq / g and a particle size of 0.05-0.1 mm, and a polymer binder, with the following ratio of components, wt. %: activated carbon 80-95 polymer binder 5-20

The proposed porous block filter material contains pores with a size of 5-40 microns. As a polymer binder, the material contains polymers from the classes of polyolefins and / or polyesters and / or their copolymers with a melt index of 2-20 g / 10 min. according to ASTM D 1238 at 190 ° C and a load of 25 Kg.

The proposed porous block filter material for complex purification of drinking water is obtained by extrusion or hot pressing of a mixture of powdered material with a particle size of 0.05-0.1 mm from activated carbon with a specific filtration surface from 900 m ² / g, iodine number from 900 mg / g, a static exchange capacity for copper from 0.8 meq / g, with a water content of 2-6% and a polymer binder, and the process is carried out at a mixture compression ratio of 12-15% and a temperature of 10-40 ° C higher than the softening temperature polymer binder with a ratio of activated carbon: polymer binder 80-95: 5-20 wt. %. The porous block material is made in the form of plates, hollow bodies of various shapes or granular materials with a granule size of 0.3-2.0 mm.

The use of activated carbon as a universal sorbent, providing complex water purification from such dissimilar chemical compounds as chlorine, organochlorine compounds and heavy metals, has become possible due to the use of activated carbon with unique properties, combining the properties of an adsorbent that removes chlorine and organochlorine from water. compounds due to sorption in micro- and mesopores, and a cation exchanger that binds heavy metals present in water due to ion exchange or the formation of chelate complexes. The manifestation of adsorption and cation-exchange properties in such coal became possible due to the combination of a developed adsorption surface in it, which ensures the contact of purified water with sorption centers of coal, the presence of a large number of micropores responsible for the sorption of small molecules (chlorine, organochlorine compounds), the content of which is characterized by iodine number, and cation-exchange groups (carboxyl, hydroxyl and phenolic):

(Monograph "OXIDIZED COAL", Tarkovskaya I.A., Kiev, Nauk, Dumka, 1981, p. 26), the number of which is expressed by the COE _Cu indicator (static exchange capacity for copper - the amount of Cu ⁺⁺ meq absorbed at room temperature with stirring, a weighed portion of activated carbon, equal to 1 g, out of 100 cubic cm of a 1% aqueous solution of copper sulfate for 2 hours).

Activated carbons with cation exchange properties can be obtained by additional oxidation of activated carbons obtained by classical methods of roasting in an atmosphere that does not contain oxidizing agents, for example, ozonation (Impacto del tratamiento con ozono sobre las propiedades superficiales del carbonado, Ingeniare. Revista chilena de ingenieria, vol. 19 №2, 2011, pp. 174-185), treatment with peroxides or solutions of concentrated sulfuric or nitric acids ("Effect of different oxidizing agent treatments on the surface properties of activated carbons" // Carbon. 1999. V. 37, No. 8. P. 1323-1332), or by carrying out the firing (activation) process in the presence of an oxidizing agent (for example, air) at a certain temperature-time regime ("Adsorptionserscheinungen in Losungen. Uber die verchiedenen Modifikationen der aktivierten kohle". Z. phys. Chem. 1929, 140, N1 / 2, s.81-88). Another well-known method of producing activated carbons with cation-exchange properties is their grinding in an oxidizing medium ("Chemical transformations of coals during mechanical dispersion", Khrenkova TM, Dissertation for the degree of Doctor of Chemical Sciences, Moscow, 1983).

In practice, the existing commercially available activated carbons intended for the purification of drinking water differ significantly in terms of COE _{Cu ++} :

NWM DH-15B coal from NWC Carbon has COE _{Cu ++} 0.5 mEq / g Pulsorb C coal from Chemviron Carbon has COE _{Cu ++} 0.35 mEq / g Kalbon 150 * 200 coal from KALPAKA CHEMICALS (P) LTD. has COE _{Cu ++} 1.21 mEq / g, CEWC 18 × 40 6-N coal from Ceycarb has COE _{Cu ++} 1.1 mEq / g, which is apparently associated with specific technological modes of their production and different raw material.

The technical result of the proposed invention is the creation of a porous block filter material that provides a complex highly effective water purification, both from chlorine and organochlorine compounds, and from heavy metals at the level of 96-99% over a significant consumer resource, with a simple technology for its production without introducing additional stages crushing, fractionation, dosing and homogeneous mixing of an additional component - a sorbent of heavy metals, the function of which is performed by activated carbon.

To achieve the maximum contact of the purified water with the adsorbent during water purification, which ensures high efficiency of water purification, activated carbon must have a large contact surface, which is achieved by using powdered forms of activated carbon with a particle size of 0.05-0.1 mm, providing an optimal volume ratio / surface, developed specific pore surface of activated carbon (from 800 m2 / g) - if the adsorption surface of activated carbon is less than 800 m2 / g, the efficiency of sorption of chlorine, organochlorine compounds and heavy metals will be insufficient; the presence of optimal through pores in the porous block filter material, which should ensure, on the one hand, good contact of the purified water with the pores of activated carbon (for this, the pores of the material should be of the minimum size), on the other hand, a satisfactory filtration rate (for this, the pores material should be of the maximum size). That is why, in the claimed porous block material, the pore size is in the range of 5-40 microns, since when the pore size is less than 5 microns, the filtration rate becomes unsatisfactory, and when the pore size is more than 40 microns, the efficiency of water purification deteriorates. In addition to the contact surface, the efficiency of water purification from chlorine or organochlorine compounds is ensured by the presence of micropores in activated carbons, the content of which is characterized by an iodine number. When the iodine number of activated carbon in the porous block material is less than 800 mg / g, activated carbon does not provide a high cleaning efficiency from these pollutants.

Another factor affecting the efficiency of water purification by porous block materials is the outer surface of the activated carbon particles accessible for contact, which is not covered with a polymer binder melt. Usually, a polymeric binder softens and blocks from 20 to 40% of the surface of the activated carbon particles, which leads to a significant deterioration in the adsorption properties of the material. The degree of blocking of the activated carbon surface by a polymer binder depends on many factors, among which the most significant are: the ratio of activated carbon: polymer binder, the nature of the polymer binder and its softening and melting points, and the degree of compression during the formation of the mixture. The selected ratio of activated carbon: polymer binder 80-95: 5-20 wt. % is due, on the one hand, to the minimum content of the polymer binder, which provides the mechanical strength of the porous block filter material - when its content is less than 5 wt. % the material is not able to keep its shape; on the other hand, when the content of the polymer binder is more than 20 wt. % polymeric binder blocks a significant surface of activated carbon particles, which leads to a deterioration in the efficiency of water purification. The use of a polymeric binder from the class of polyolefins (for example, low-density polyethylene, high-pressure polyethylene, polypropylene) and / or polyesters (for example, polyethylene terephthalate) and / or their copolymers (for example, a copolymer of polyethylene with vinyl acetate) is due, on the one hand, to their chemical inertness and insolubility in water, on the other hand, sufficiently low softening temperatures, which make it possible to intensify the process of making a porous block material.

To ensure the maximum surface of activated carbon available for sorption, the process of making a porous block filter material is carried out at a temperature 10-40 ° C higher than the softening temperature of the polymer binder and at a compression ratio of the initial mixture of 12-15%. At a temperature lower than 10 ° C, the softening temperature of the polymer binder and a compression ratio of less than 12%, the formation of a strong block material does not occur, and at a temperature higher than 40 ° C the softening temperature of the polymer binder and a compression ratio of more than 15%, blocking a significant surface of the activated carbon as a result of the flow of molten polymer binder.

Reducing the blocking of the activated carbon surface by the binder melt in the present invention is proposed by using the initial activated carbon containing water, since when heated during the formation of a porous block material, water evaporating in the form of steam from the pores of the coal will open the surface of the activated carbon particles blocked by the polymer melt. The water content in the original activated carbon less than 2% is insufficient to unblock a significant surface area of the activated carbon coated with a polymer binder melt. Water content in excess of 6% impairs the binding of activated carbon particles into a strong blocky porous material.

Optimization of the combination of the above factors affecting the blocking of the activated carbon surface by the melt of the polymer binder (the ratio of the components of the mixture, the nature of the polymer binder, the processing temperature of the initial mixture and the degree of its compression, the water content in the initial activated carbon) makes it possible to obtain a porous block filter material with a large a part of the activated carbon surface is not blocked by the polymer melt and therefore the functional characteristics (filtration surface, iodine number, static exchange capacity for copper) are slightly less than those of the original activated carbon (no more than 10-15%).

The efficiency of cleaning from toxic metals is determined by the amount of carboxyl, hydroxyl and phenolic groups, which is characterized as a static exchange capacity, and is determined by the sorption of one of the heavy metals, for example, copper (COE _Cu ). The choice of copper for the COE indicator as a test metal is due to two reasons: firstly, for copper, the MPC value for drinking water is higher than for other heavy metals, which, when assessing the efficiency of water purification according to Russian GOST and the international NSF standard, means testing at large initial concentrations of heavy metal in purified water and, consequently, a greater load on the sorbent. Achievement of high efficiency of water purification by copper for filter material means in practice high efficiency of water purification from other heavy metals. Second, the determination of copper in water is possibly the simplest analytical method.

COE _Cu should be at least 0.7 mg-eq / g, since at lower COE _Cu values the porous block filter material does not provide high sorption efficiency for a given purification resource. The production of porous block filter material of various shapes: plates, hollow bodies and granular materials with a grain size of 0.3-2.0 mm is associated with the possibility of its use in flat gravity filter cartridges, in hollow cylinder-shaped cartridges of pressure and gravity filters, as well as as a filling medium in cartridges of gravity and pressure filters. Below are examples of the claimed porous block filter material, and in the table - the results of tests on the effectiveness of complex water purification from chlorine, chloroform and heavy metals: copper and lead. The above examples give an idea of the characteristics of the claimed porous block filter material for the complex purification of drinking water, but are not exhaustive. In the above examples 1-4, tests on the effectiveness of water purification were carried out by placing a porous block filter material in the form of a hollow cylinder (1) in a jug filter cartridge (2) (Fig. 1) or in the example 5 given - in the form of a granular material (1) in the plastic casing of the jug filter cartridge (2) (Fig. 2). In this case, in the case of tests of a porous block material in the form of a hollow cylinder, the cartridge itself, in addition to the porous block filter material, contained a fixation system with a funnel of a pitcher filter (3), and a plug of the bottom hole of the porous block filter material (4), hermetically connected to the porous block filter material. material by gluing. In examples 1-4, the dimensions of the porous block filter material were: height 75 mm, outer diameter 62 mm, wall thickness 14 mm. In example 5, the volume of granular porous block filter material was 155 cubic meters. cm.

Evaluation of the efficiency of water purification was carried out in accordance with GOST 31952-2012 “WATER-CLEANING DEVICES. General requirements for efficiency and methods of its determination ”. The determination of the pore size was carried out by the porosimetry method (gas-dynamic method). The specific surface area was determined by porosimetry (BET method). The invention is illustrated by the following non-limiting examples.

Example 1.

Porous block filter material is obtained by extrusion of a mixture containing activated carbon with a specific filtration surface of 1100 m2 / g, an iodine number of 1100 mg / g, COE _Cu 0.9 mEq / g, a water content of 5%, and a polymer binder ( low-pressure polyethylene with a softening point of 115 ° C), with a particle size of the mixture components from 0.05 to 0.1 mm at a ratio of activated carbon: polymer binder (80:20) wt. %, temperature 145 ° and compression ratio of the mixture 14%. A porous block material was obtained with a pore size of 10 to 30 μm, a specific filtration surface of 1000 m2 / g, an iodine number of 1000 mg / g, and COE _Cu 0.8 mg-eq / g. The results of testing complex water purification are presented in the table.

Example 2.

A porous block filter material is obtained by hot sintering a mixture containing activated carbon with a specific filtration surface of 1500 m2 / g, an iodine number of 1250 mg / g, COE _Cu 1.15 mEq / g, a water content of 6%, and a polymer binder (low-pressure polyethylene with a softening point of 115 ° C), with a particle size of components from 0.06 to 0.08 mm at a ratio of activated carbon: polymer binder (85: 15) wt. %, temperature 140 ° and compression ratio of the mixture 12%. The porous block material was obtained with a pore size of 5 to 20 μm, a specific filtration surface of 1250 m2 / g, an iodine number of 1150 mg / g, and COE _Cu 0.95 mEq / g. The results of testing complex water purification are presented in the table.

Example 3.

A porous block filter material is obtained by hot sintering a mixture containing activated carbon with a specific filtration surface of 1000 m2 / g, an iodine number of 1000 mg / g, COE _Cu 0.85 mEq / g, a water content of 4%, and a polymer binder (low pressure polyethylene with a softening point of 115 ° C), with a particle size of the components from 0.08 to 0.1 mm at a ratio of activated carbon: polymer binder (82:18) wt. % at a temperature of 145 ° and a compression ratio of 15%. The porous block material was obtained with a pore size of 15 to 35 μm, a specific filtration surface of 900 m2 / g, an iodine number of 850 mg / g, and COE _Cu 0.80 mg-eq / g. The results of testing complex water purification are presented in the table.

Example 4.

A porous block filter material is obtained by hot sintering a mixture containing activated carbon with a specific filtration surface of 900 m2 / g, an iodine number of 900 mg / g, COE _Cu 0.8 mEq / g, a water content of 2%, and a polymer binder (low-pressure polyethylene with a softening point of 115 ° C), with a particle size of the components from 0.08 to 0.1 mm at a ratio of activated carbon: polymer binder (80:20) wt. %, temperature 155 ° and compression ratio of the mixture 15%. A porous block material was obtained with a pore size of 20 to 40 μm, a specific filtration surface of 800 m2 / g, an iodine number of 800 mg / g, and COE _Cu 0.7 mg-eq / g. The results of testing complex water purification are presented in the table.

Example 5.

A porous block filter material is obtained by hot sintering a mixture containing activated carbon with a specific filtration surface of 1150 m2 / g, an iodine number of 1100 mg / g, COE _Cu 0.95 mEq / g, a water content of 6%, and a polymer binder (low-pressure polyethylene with a softening point of 115 ° C), with a particle size of components from 0.08 to 0.1 mm at a ratio of activated carbon: polymer binder (95: 5) wt. %, temperature 145 ° and compression ratio of the mixture 12%. A porous block material was obtained with a pore size of 10 to 20 μm, a specific filtration surface of 950 m2 / g, an iodine number of 1050 mg / g, and COE _Cu 0.85 mg-eq / g. The resulting porous block material is crushed and dispersed into granules with a size of 0.3 to 1.0 mm. The porous block material is made in the form of a plate with a diameter of 100 mm and a height of 20 mm. The results of testing complex water purification are presented in the table.

As follows from the results given in the table, the inventive porous block filter material provides high efficiency of integrated water purification during a significant service life of the filter.

Claims (6)

1. Porous block filter material for complex purification of drinking water, containing activated carbon and polymer binder, characterized in that the filter material contains fine particles of activated carbon with a size of 0.05-0.1 mm, specific filtration surface from 800 m ² / g , iodine number from 800 mg / g and static exchange capacity for copper from 0.7 mg-eq / g with the following ratio of components, wt. %: Activated carbon 80-95 polymer binder 5-20 2. A porous block filter material for complex purification of drinking water according to claim 1, characterized in that it contains pores with a size of 5-40 microns. 3. Porous block filter material for the complex purification of drinking water according to claim 1, characterized in that it contains polymers from the classes of polyolefins and / or polyesters and / or their copolymers with a melt index of 2-20 g / 10 min as a polymer binder. ASTM D 1238 at 190 ° C and a load of 25 Kg. 4. A method of obtaining a porous block filtering material for complex purification of drinking water according to claim 1 is carried out by extrusion or hot pressing of a mixture of powdered material with a particle size of 0.05-0.1 mm from activated carbon with a specific filtration surface of 900 m ² / g , iodine number from 900 mg / g, static exchange capacity for copper from 0.8 mg-eq / g, with a water content of 2-6% and a polymer binder and the process is carried out at a mixture compression ratio of 12-15% and a temperature of 10 40 ° C above the softening point of the polymer binder with the ratio of activated carbon: polymer binder (80-95) :( 5-20) wt. %. 5. A method of obtaining a porous block filter material for complex purification of drinking water according to claim 4, characterized in that the porous block material is made in the form of plates, hollow bodies of various shapes or granular materials with a granule size of 0.3-2.0 mm.

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