WO2020180277A1

WO2020180277A1 - Method for purifying aqueous solutions containing heavy metal ions

Info

Publication number: WO2020180277A1
Application number: PCT/UA2019/000026
Authority: WO
Inventors: Николай Константинович МОНАСТЫРЕВ
Original assignee: Николай Константинович МОНАСТЫРЕВ
Priority date: 2019-03-01
Filing date: 2019-03-01
Publication date: 2020-09-10

Abstract

The invention can be used in the purification of water of heavy metal ions. A reactor vessel comprises a layer of metal pellets and electrodes made of iron and/or alloys thereof. The vessel is filled with a quantity of an aqueous solution being purified, and the metal pellets are exposed to electrical pulses via the electrodes, gradually breaking down said metal pellets and producing an iron-based composition possessing high activity toward the coagulation of heavy metal ions, directly in a cavity of the reactor vessel. The aqueous solution being purified is pumped into the reactor vessel cavity from below in a continuous flow mode together with a stream of an oxygen and air mixture such that it is possible to create a fluidized pellet bed. The invention makes it possible to produce a sorbent/coagulant directly in an aqueous solution being purified within a reactor vessel.

Description

A method for purifying aqueous solutions containing heavy metal ions.

The present invention relates to means for the complex purification of industrial and rainwater effluents containing ions of heavy metals, in particular chromium, nickel, zinc, cadmium, iron, copper, using the method of electroerosive sorption-coagulation for their sorption, coagulation and removal from aqueous solutions.

A known method of water purification in order to obtain drinking water, including the operation of preliminary purification of source water from harmful and toxic substances, water cooling and subsequent removal from the water of heavy isotopes of hydrogen - deuterium and radioactive tritium - in a stream of water by selective solid condensation of these heavy isotopes in two stages: at the first stage - on the surface of a solid body cooled below 0 ° C washed by the outgoing water, and then at the second stage - on the surface of single layers of condensate - ice, which are constantly formed, while the surface temperature of each layer is maintained at the level originally set evaporator temperature, after obtaining the required ice thickness, the crystallization process is stopped and heavy oxygen isotopes ¹⁷ 0 and ¹⁸ 0 are removed, after which light water with a reduced content of heavy hydrogen and oxygen isotopes is taken, defrosting and draining of condensate is carried out, the resulting water is activated by optimizing it mineral composition and structure [Declaration patent of Ukraine N ° 51330 A for the invention, IPC 7 C02F9 / 00, Publ. 15.1 1.2002. Bul. No 1 1/2002].

The disadvantage of the described method lies in its complexity and high cost of the resulting product - purified water, which significantly limits its use for cleaning, in particular, industrial and rainwater waste from ions of heavy metals.

The closest to the proposed invention in terms of the number of essential features is a method for purifying aqueous solutions containing heavy metal ions, including 'filling the reactor vessel with a portion of the aqueous solution to be purified, placing a layer of metal granules in the cavity of the reactor vessel, exposing the granule layer to electric pulses through electrodes, which connected to the corresponding outputs of the pulse generator, the gradual destruction of the granules under the action of spark discharges between them until the formation of an aqueous solution of the required purity, which is poured from the discharge chamber into the prepared container [Shcherba A.A., Zakharchenko S.N. Application of the method of electroerosive coagulation. / In the journal: "Water and Water Treatment Technologies" - N ° 4, December 2002; from. 27-29].

The described method is not sufficiently effective, because, firstly, require repeated transmission of one portion erasable aqueous solution through the lumen of a reaction vessel, and secondly, because of the _location erasable aqueous solution of various substances recorded cases of the formation of water-soluble harmful complex compounds, the removal of which requires additional methods, for example, the method of evaporation of the resulting solution. So to remove harmful complex compounds soluble in water, single-stage evaporators are used with additional purification of the resulting condensate on ion-exchange filters [see. Monakhov A.S. Nuclear power plants and their technological equipment. - Moscow: Energoatomizdat, 1986. p. 26-38], which is not always economically feasible and affordable.

The proposed invention is based on the task of creating such a method for purifying aqueous solutions from heavy metal ions, which would be more efficient and more economical, and therefore more accessible even for small industrial enterprises.

The problem is solved in the proposed method by creating conditions for the synthesis from iron and / or its alloys of the required amount of compositions (compounds), active in relation to heavy metal ions contained in the solution, sorbents-coagulants directly in the purified aqueous solution. The increased activity of the obtained compounds can be explained, for example, by the fact that at the moments of spark discharges between iron granules in water in the presence of oxygen molecules, cavitation processes occur, accompanied by the appearance of high explosive pressures, high temperatures and high local density of electrical energy, destroying water molecules and supplied to zone of spark discharges of oxygen molecules, catalyzing the processes of obtaining iron oxides and hydroxides. Almost instantaneous evaporation-condensation of the metal leads to the production of ultra- and nanodispersed compositions of iron oxides and hydroxides with an amorphous and fine-crystalline structure of particles, with a developed surface, high chemical activity and sorption capacity. The presence of excess oxygen in the bubbling water-air mixture (relative to the amount of oxygen in the water) ensures the formation of ozone (Oz) and, as a consequence, the rapid and almost complete oxidizability of iron microparticles to higher oxides, which significantly increases the activity and sorption capacity of the resulting composition. as experiments have shown, in relation to heavy metal ions present in the treated aqueous solutions of industrial effluents. The activity of synthesized iron-containing sorbents-coagulants with respect to heavy metal ions (nickel Ni, cobalt Co, lead Pb, zinc Zn, manganese Mn, cadmium Cd, tin Sh, arsenic As, copper Cu, etc.) exceeds the activity of oxides and iron hydroxides obtained by traditional methods. At the same time, the process of coagulation of heavy metal compounds occurs with the participation of ozone almost simultaneously with the formation of compositions of active sorbents-coagulants during electroerosive dispersion (EED) of iron and steel granules in a purified aqueous solution, which makes it possible to increase the efficiency and reduce the cost of implementing the proposed method, and therefore it is more accessible to industrial enterprises than the methods of cleaning known today.

The proposed, as well as the known method of purification of aqueous solutions containing ions of heavy metals, includes filling the reactor vessel with a portion of the aqueous solution to be purified, placing a layer of metal granules in the cavity of the reactor vessel, affecting the granule layer with electric pulses through electrodes that are connected to the corresponding outputs of the generator pulses, gradual destruction of granules under the action of spark discharges between them until an aqueous solution of the required purity is formed, which is poured from the discharge chamber into a prepared container, and, according to the invention, the electrodes and a layer of metal granules are made of iron and / or its alloys, the purified aqueous solution is fed into the cavity of the reactor vessel in a flow-through mode with a pressure from the bottom together with the flow of an oxygen-air mixture with the possibility of creating a "pseudo-boiling" layer of granules, and in the process of exposing the layer of granules to electric impulses and an oxygen-air bubbling mixture, compositions based on ove iron, with a high activity to coagulate heavy metal ions contained in the purified aqueous solution, directly in the cavity of the vessel-reactor. Experiments have shown that when processing industrial and rainwater effluents containing ions of heavy metals, in particular chromium, nickel, zinc, cadmium, iron, copper, compositions in the form of ultradispersed and nanodispersed powders of iron oxides and hydroxides obtained during the implementation of the proposed method, the latter in EED zones enter into physicochemical interactions with heavy metal ions, as a result of which water-insoluble complex compounds are formed, precipitated, and therefore easily removed from the purified solutions.

The aqueous solution is fed into the dispersion zone under pressure from the bottom simultaneously with the flow of the oxygen-air mixture through a perforated grid made of dielectric material so that the layer of iron and steel granules is in a "pseudo-boiling" state. At the same time, the intensity of contacting the granules with each other and with the electrodes significantly increases, and, as a result, the number of electrical contacts between them per unit time per unit volume of the aqueous solution being purified increases, which leads to an increase in the release of the amorphous phase of metal hydroxides (coagulants), ozone Oz , radicals OH-, which intensifies the passage of chemical reactions to obtain water-insoluble complex compounds, which include chromium, nickel, zinc, cadmium, iron, copper.

To stabilize the modes of the dispersion process, the electrodes in the reactor vessel (cathode and anode) are made of carbon steel, for example, StZ grade. The dispersible layer of metal granules consists of iron and iron-based alloys. The presence of carbon steel in the cavity of the reactor vessel contributes not only to the production of coagulants, but also softens the hydrodynamic load on the vessel-reactor vessel.

In this case, iron hydroxide compounds, in which iron has a valence of +2, +3, +4 (based on oxides FeO, PerO3, ReSH, formed during the electroerosive machining of steel electrodes and iron and / or steel granules or chips, have a high coagulating ability in relation to the ions of the above heavy metals.

In the process of conducting patent information research in the preparation of this application, the authors did not find ways to purify aqueous solutions containing heavy metal ions, with the above set essential features, which proves the compliance of the proposed technical solution with the criterion of the invention "novelty".

The technical result obtained as a result of the implementation of the invention consists in creating conditions for the synthesis of the required amount of compositions (powders) from iron and / or its alloys, active against heavy metal ions contained in the solution to be purified. These compositions are synthesized directly in a purified aqueous solution. Due to their extremely high activity, the named compositions exist under EED conditions for a very short time, during which they enter into chemical reactions with the ions surrounding the EED zones ^; heavy metals and coagulate the latter. The increased activity of the resulting compositions (powders) can be explained, in particular, by the fact that at the moments of spark discharges between iron granules in water cavitation processes occur, accompanied by the occurrence of high explosive pressures, high temperatures and high local density of electrical energy, destroying water and oxygen molecules , ozone production, which catalyze the processes of obtaining iron oxides and hydroxides and their interaction with heavy metal ions.

The specified technical result has not been identified by the authors in the known technical solutions that are included in the prior art, therefore the proposed method can be recognized as meeting the criterion of the invention "inventive step".

The proposed method consists of currently known technological methods, tools and materials. It can be used in various sectors of the national economy, where it is necessary to purify aqueous solutions from heavy metal ions, therefore, it can be concluded that the proposed solution meets the criterion of the invention "industrial applicability".

The essence of the invention is explained with the help of the drawing (Fig. 1), which schematically shows an installation that implements the proposed method.

The installation that implements the proposed method contains a vessel-reactor 1 made of dielectric material. In the cavity of the reactor vessel 1, a horizontal mesh partition 2 of dielectric material is installed, on which granules 3 of metallic iron and / or its alloys are placed in a uniform layer in the form of tablets with a diameter of 8-10 mm. Two vertical electrodes 4 of different polarity, made of steel, pass through the partition 2, as well as two tubes / not shown /, one ends of which are fixed on opposite sides of the partition 2, and the second - connected to an oxygen source - an oxygen cylinder provided with a reducer / not shown /. The ends of the tubes for the outlet of oxygen are equipped with nozzles with the possibility of creating a set of oxygen bubbles directly above the plane of the partition 2 in the layer of granules 3 (not shown). The reactor vessel 1 is filled with an aqueous solution to be cleaned by 80 - 85% of the cavity volume. The volume of the layer of granules 3 of metallic iron and electrodes 4, which are in the solution to be cleaned, is 20 - 25% of the total volume of the cavity of the vessel-reactor 1. Each electrode 4 has the shape of a rectangular parallelepiped, the larger edge of which is located vertically. The free end of each electrode 4 touches the granules 3 of metallic iron, and the second end is connected to the corresponding output of the pulse generator - anode or cathode / not shown /. In the lower part of the reactor vessel 1, a fitting 5 is installed for supplying the purified aqueous solution under pressure into the cavity of the reactor vessel 1 in a flow mode with a pressure from the bottom to create a "pseudo-boiling" bed of granules 3 using a suitable pump / not shown /. In the lower part of the cavity of the reactor vessel 1, under the mesh partition 2, a pallet 6 is horizontally located - for the accumulation and removal of sediment from the reactor vessel 1 - a mixture of substances formed as a result of coagulation from the purified aqueous solution of the compounds of the above heavy metals, which is formed during the EED granules 3. In the upper part of the reactor vessel 1 there is a fitting 7 with a valve designed to control the level of the water solution to be purified in the cavity of the reactor vessel 1 by setting the valve to the speed of the solution draining in flow mode. An electrovalve connected to the control system / not shown / can be used as a fitting 7 with a gate valve. In the upper part of the reactor vessel 1, a valve 8 is installed, designed to supply new iron granules 3 to the partition 2 into the cavity of the reactor vessel 1, as well as a tube connecting the upper part of the cavity of the reactor vessel 1, not filled with the aqueous solution to be cleaned, to the atmosphere, and intended for the exit of steam during the EED of granules 3 / not shown /. The installation is provided with a control system containing a control computer with appropriate software, the proper inputs of which are connected to temperature sensors, the level of the water solution being purified and the degree of its purification, and the corresponding outputs are connected to a pump and a pulse generator (not shown). The control system is designed to maintain the stability of the installation and record the current parameters of the installation and data related to the purity of the solution that passes through the fitting 7 with a valve at the outlet from the cavity of the reactor vessel 1, and the volume of powder that accumulates on the tray 6.

Example. In the cavity of the reactor vessel 1, made of a dielectric material, in which a horizontal mesh baffle 2 made of a dielectric material is installed, granules of metallic iron in the form of tablets 8-10 mm in diameter were loaded. Granules 3 were arranged in a uniform layer on a horizontal mesh partition 2 and fed into the cavity of the reactor vessel 1 through the nozzle 5 the purified aqueous solution so that during the operation of the installation it completely covered the layer of granules 3. Two vertically arranged electrodes 4 of different polarity passed through the partition 2 made of steel (StZ), located at a distance of 200 - 250 millimeters from each other in the cavity of the vessel-reactor 1. The volume of granules 3 and electrodes 4 was approximately 25% of the total volume of the cavity of the vessel-reactor 1. Each electrode 4 had the shape of a rectangular parallelepiped and was connected to the output of the pulse generator of the corresponding polarity. A purified aqueous solution was fed into the cavity of the reactor vessel 1 from bottom to top through the nozzle 5, and oxygen from a cylinder with a reducer was fed through the tubes and a set of bubbles was created directly above the plane of the partition 2 in the granule layer 3 (not shown). Rectangular pulses with a frequency of 800 Hz and an amplitude of 400 V were applied to electrodes 4. When the pulses were transmitted between individual granules and electrodes 4, spark discharges occurred. At the moments of spark discharges between iron granules 3, cavitation processes took place in the purified aqueous solution, accompanied by the appearance of high explosive pressures, high temperatures and high local density of electrical energy, destroying water molecules and oxygen supplied to the EED zone, accompanied by the formation of ozone. These processes catalyzed the production of iron oxides and hydroxides and their interaction with heavy metal ions in solution, which led to their coagulation. With an increase in the temperature of the purified aqueous solution and a decrease in the number of granules 3, the control computer corrected the EED parameters. Due to the creation of a "pseudo-boiling" layer of iron granules, the intensity of contacting both the granules 3 with each other and the granules 3 with the electrodes 4 increased significantly, and, as a result, the number of spark contacts between them per unit time increased, which increased the productivity of the cleaning process. The aqueous solution to be cleaned was fed into the cavity of the reactor vessel 1 in a flow-through mode with a pressure from the bottom through nozzle 5 for creating a "pseudo-boiling" layer 3 of granules, and an aqueous solution heated and purified during EED through a nozzle 7 with a valve was poured from chamber 1 into a prepared container, maintaining a predetermined level of the solution to be purified in the cavity of the reactor vessel 1.

As the granules 3 were destroyed in the cavity of the reactor vessel 1, new portions of metallic iron granules were loaded through valve 8 to maintain the ratio of 20-25% of the volume of the granules and electrodes 4 to the volume of the aqueous solution. The process of supplying oxygen to the cavity of the reactor vessel 1 was carried out simultaneously with the supply of electric voltage to the electrodes 4 from the pulse generator. After loading the pallet 6 with solid sediment, the pallet was removed from the cavity of the vessel-reactor 1 and unloaded.

Table 1 shows the analysis data of the initial purified aqueous solution. TABLE 1.

Table 2 shows the analysis data of an aqueous solution that was purified in accordance with the proposed method.

TABLE 2

Due to the creation of conditions for the synthesis from iron and / or its alloys of the required amount of powders with increased activity against heavy metal ions directly in the purified aqueous solution, the proposed method turned out to be more effective and less costly compared to the prototype method and can be used as part of the technological processes for the complex treatment of industrial and rainwater effluents containing heavy metal ions, in particular chromium, nickel, zinc, cadmium, iron, copper.

List of items in the schematic drawing:

1 - reactor vessel made of dielectric material;

2 - horizontal mesh partition made of dielectric material;

3 - granules of metallic iron or its alloys; 4 - steel electrode;

5 - fitting 5 for feeding the purified aqueous solution into the cavity of the reactor vessel 1;

6 - pallet for accumulation and removal of sediment from the reactor vessel 1;

7 - a fitting with a valve for draining the purified water from the reactor vessel 1;

8 - valve for feeding new iron granules into the cavity of the reactor vessel 1.

Claims

Claim.

A method for purifying aqueous solutions containing heavy metal ions, including filling the reactor vessel with a portion of the aqueous solution to be purified, placing a layer of metal granules in the cavity of the reactor vessel, affecting the granule layer with electric impulses through electrodes that are connected to the corresponding outputs of the pulse generator, and gradually destroying the granules under the action of spark discharges between them until an aqueous solution of the required purity is formed, which is poured from the discharge chamber into a prepared container, characterized in that the electrodes and a layer of metal granules are made of iron and / or its alloys, the purified aqueous solution is fed into the cavity of the reactor vessel into flow regime with a pressure from the bottom together with the flow of an oxygen-air mixture with the possibility of creating a "pseudo-boiling" layer of granules, and in the process of affecting the granule layer with electric impulses and an oxygen-air bubbling mixture, iron-based compositions are obtained with high activity to coagulation of heavy metal ions contained in the purified aqueous solution directly in the cavity of the reactor vessel.