EA031763B1 - Solution demineralization method - Google Patents

Abstract

The invention is related to the field of water conditioning technologies and can be used for desalination of brackish ground water, seawater, for wastewater treatment, etc. The technical objective of the invention is development of a method for demineralization (desalting) of solutions that is able to function owing to solar heat energy. The technical result to be obtained by utilization of the invention consists in lower energy consumption for solution demineralization, which is achieved by using heat-sensitive hydrogels contacting when exposed to solar heat and heated to temperatures not exceeding 50°C. The required technical result is attained by provision of a solution demineralization method comprising a poly-electrolyte hydrogel contacting a low-molecular salt solution, wherein a contact of a heat-sensitive gel with the swollen poly-electrolyte hydrogel is performed so that a part of the solution accumulated by the poly-electrolyte hydrogel passes to the heat-sensitive hydrogel, then the heat-sensitive hydrogel is heated by solar heat to a temperature of 30 to 50°C, and the depleted solution is separated from the heat-sensitive hydrogel. The advantage of the invention as compared to the prior art is lower energy consumption for desalination of solutions such as saline ground water or sea water.

Description

The invention relates to the field of water treatment technologies and can be applied to the desalination of brackish groundwater, sea water, wastewater treatment, etc. An object of the invention is to develop a method for the demineralization (desalination) of solutions capable of functioning due to the energy of solar heat. The technical result obtained from the implementation of the invention is to reduce energy costs for demineralization of solutions, which is achieved through the use of temperature-sensitive hydrogels, contrang under the influence of solar heat when heated to temperatures not exceeding 50 ° C. The required technical result is achieved by the fact that in the method of demineralization of solutions, which includes contacting a polyelectrolyte hydrogel with a solution of a low molecular weight salt, a thermosensitive gel and a swollen polyelectrolyte hydrogel are contacted, while a part of the solution accumulated by the polyelectrolyte hydrogel is transferred to a thermosensitive hydrogel, then the temperature is heated, then the temperature is heated by heating the polyelectrolyte hydrogel. at a temperature of from 30 to 50 ° C and separate the depleted solution from the heat-sensitive of the hydrogel. The advantage of the invention in comparison with the prototype is to reduce energy costs for the desalination of solutions, such as saline groundwater or seawater.

The invention relates to the field of water treatment technologies and can be applied to the desalination of brackish groundwater, sea water, wastewater treatment, etc.

A set of chemical methods for the demineralization of water, in particular the method of demineralization of water by ion exchangers, is known. This set of processes is based on the use of chemical processes, in particular, ion exchange processes occurring during the contact of the working substance and the solution being processed (Grebenyuk VD Water desalination with ion exchangers / VD Grebenyuk, AA Mazo. Chemistry. Moscow, 1980 , pp. 228-233; Ion-exchange membrane materials: properties, modification and practical application / AB Yaroslavtsev, VV Nikonenko. Russian nanotechnologies. 2009, 4 (3), p. 44-63).

The disadvantage of this method of demineralization (desalination) of solutions is the need to use additional reagents associated with their utilization / regeneration.

Known Donnanovsky dialysis, which can also be used as a method of demineralization (desalination) solutions. Donnan dialysis is essentially a continuous ion exchange process. During dialysis, the ions of one solution are continuously exchanged for other ions of the same sign in another solution, separated from the first ion-exchange membrane. In such dialysis, the electric potential is created by the difference in the concentrations of ions passing through the membrane (Lukashev EA. Regeneration of acids in the process of donan dialysis / Lukashev E.A., Skakalskaya L.I., Mochalov E.P. Journal of Applied Chemistry. 1993, t 66, No. 8, pp. 1737-1743).

The disadvantage of this method of demineralization (desalination) solutions is the need to use an auxiliary solution with a low concentration of removed ions, which is unacceptable, for example, for the purposes of seawater desalination.

Known electrodialysis method of demineralization (desalination) solutions. This method is based on the use of two types of membranes: membranes selectively permeable to cations - cation exchangers (cation exchange) membranes, and membranes selectively permeable to anions - anion exchangers (anion exchange) membranes. A sequence of alternating cation-exchange and anion-exchange membranes is located between the two electrodes. With a sufficiently high external electric potential, the electric current transfers cations from the initial solution to the concentrate stream through the cation-exchange membrane located on the cathode side. The anions move in the opposite direction and are transferred to the concentrate stream through the anion-exchange membrane. In this case, the cations in the concentrate flow are retained by the anion-exchange membrane on the cathode side, and the anions are retained by the cation-exchange membrane on the opposite side. As a result, the initial solution is purified from the electrolyte dissolved in it by means of two concentrate flows directed in opposite directions, with the ions passing through the membranes remaining in the concentrate (Pilat B.V. Electrodialysis bases. M. Avavlon, 2004).

The main disadvantage of this method of demineralization (desalination) of solutions is the need for the cost of electricity for desalination, and the amount of energy used increases with increasing depth of purification.

There is a method of demineralization (desalination) of solutions, based on the phenomenon of reverse osmosis. When implementing this method, a high pressure created in one of the parts of the system forces the solvent (for example, water) to pass through the semi-permeable membrane from the region with the more concentrated solution to the region with the less concentrated solution, that is, in the opposite direction for osmosis. It uses a membrane that passes the solvent, but does not let at least some of the substances dissolved in it (for example, low molecular weight ions). (Mamet AP. The use of reverse osmosis in water desalination for powering steam generators of TPPs and NPPs / A.P. Mamet, Yu.A. Sitnyakovsky // Thermal Engineering. 2000, No. 7, p. 20-22).

The disadvantage of this method is the need to use high pressures (about 217 atm for filtering and desalinating drinking and brackish water and 24-70 atm for seawater), which is caused, among other things, by the significant hydrodynamic resistance of dense membranes. This leads to both significant energy costs and the need to use hydraulic equipment of increased strength.

The closest analogue in terms of the number of essential features (prototype) is the method of demineralization (desalination) of solutions, implemented in a device for filtering aqueous solutions, based on the phenomenon of redistribution of concentrations in hydrogel solution systems (SU No. 1790974, IPC V01I 24/48, 36/00 , published January 30, 1993, bulletin No. 4).

This method is also described in Budtova, T., & Suleimenov, I. (1995). Physical principles of using polyelectrolyte hydrogels for purifying and enrichment technologies. Journal of applied polymer science, 57 (13), 1653-1658, a underlying concentration redistribution effect — in Budtova, T. W., Belnikevich, N. G., Suleimenov, I. E., & Frenkel, S. Y. (1993). Concentration redistribution of low-molecular-weight salts in the presence of a strongly swelling polyelectrolyte hydrogel. Polymer, 34 (24), 5154-5156.

When implementing this method, the polyelectrolyte hydrogel is placed in a solution of low molecular weight salt (for example, desalinated sea water). The effect of the redistribution of concentrations leads to the fact that the hydrogel accumulates a solution with a lower concentration (compared to

- 1 031763 with the original one). At the same time, a solution with a higher concentration is formed in the surrounding hydrogel solution. To separate the water from the hydrogel, an electric current is passed through the hydrogel, which causes contraction of the working substance (decrease in the volume of the swollen hydrogel), followed by the separation of the lean solution.

The disadvantage of the prototype is the need to use electrical energy expended on the collapse of the hydrogel. It also leads to a relatively high consumption of the working substance, collapsing due to electrode electrochemical processes.

An object of the invention is to develop a method for the demineralization (desalination) of solutions capable of functioning due to the energy of solar heat.

The technical result obtained from the implementation of the invention is to reduce energy costs for demineralization of solutions, which is achieved through the use of temperature-sensitive hydrogels, contrang under the influence of solar heat when heated to temperatures not exceeding 50 ° C.

The required technical result is achieved by the fact that in the method of demineralization of solutions, which includes contacting a polyelectrolyte hydrogel with a solution of a low molecular weight salt, according to the invention, a temperature-sensitive gel and a swollen polyelectrolyte hydrogel come into contact, while a part of the solution accumulated by the polyelectrolyte hydrogel goes into a temperature-sensitive hydrogel, and then a heatture, then the temperature sample, then heat the hydrogel, then heat the hydrogel. solar heat at a temperature of from 30 to 50 ° C and separate the depleted solution ie heat-sensitive hydrogel.

A device that implements the method is a system that provides interrupted contact between a temperature-sensitive hydrogel and a polyelectrolyte hydrogel, as well as an interrupted contact between a temperature-sensitive hydrogel and the surface heated by direct sunlight. Interrupted contact allows the implementation of a staged mode of water demineralization, which includes the following stages:

stage swelling polyelectrolyte hydrogel in demineralizable water;

the stage of contact of the polyelectrolyte and thermosensitive hydrogels, at which the depleted solution accumulates with the thermosensitive hydrogel;

stage separation of the depleted solution from the thermosensitive hydrogel due to contact with the surface, heated by direct sunlight.

The invention is illustrated in FIG. 1, which shows a diagram of a demonstration experiment to the effect of separating a depleted solution from a polyelectrolyte hydrogel upon its contact with a temperature-sensitive one;

FIG. 2a-w, which show the general scheme of the device that implements the inventive method, including the stages.

A diagram of a demonstration experiment illustrating the effect of separating a depleted solution from a polyelectrolyte hydrogel when it is in contact with a temperature-sensitive one, which forms the basis of the proposed method (Fig. 1) contains the initial solution (1);

sample of polyelectrolyte hydrogel (2);

sample heat sensitive hydrogel (3);

test solution (4).

In a demonstration experiment, a dry polyelectrolyte hydrogel (2) is placed in the initial solution with a high concentration of low molecular weight salt (1). The gel swells in it, accumulating a solution with a concentration of less than the original. Next, the polyelectrolyte hydrogel is removed from the solution and brought into contact with heat-sensitive (3). Thermosensitive gel selects part of the solution, accumulated by polyelectrolyte gel, due to its own swelling. Next, the heat-sensitive gel is heated, as a result of which it collapses, releasing a solution with a low concentration (4).

A device that implements the inventive method (FIG. 2) contains an electronic control unit (1);

channel for supplying demineralizable solution (2);

capacity with polyelectrolyte gel (3);

upper contact grid (4);

a lattice (5), impermeable to the gel and permeable to the liquid;

capacity for heat-sensitive gel (6);

piston mechanism (7);

heated surface (8);

channel for collecting demineralized water (9).

The method is as follows.

Using the electronic control unit (1), the desalination solution is fed into (2) a container with a polyelectrolyte gel (3) (Fig. 2b). As a result, the polyelectrolyte gel swells, filling up the entire container (3), which is ensured by selecting the amount of gel in the container (3). In the swollen

- 2 031763 able gel comes in contact with the upper contact grid (4). The solution enriched in the low molecular weight component is drained from the underside of the container (3) through a grid (5), impermeable to gel and permeable to liquid (Fig. 2c).

Upon reaching the saturation level of the polyelectrolyte gel in the tank (3) with the help of an electronic control unit (1), a piston mechanism (7) is activated, which provides contact between the tank (3) and the tank filled with the heat-sensitive gel (6) through the grid (4) ( Fig. 2d).

The amount of heat-sensitive gel filling the container (6) is selected so that this one, when in contact with a saturated polyelectrolyte gel, receives from the latter a depleted solution in an amount that ensures the container (6) is completely filled (Fig. 2d).

Upon reaching the specified level of swelling of the temperature-sensitive gel in the tank (6) using an electronic control unit (1) include a piston mechanism (7), which leads to contact of the container (3) with the heated surface (8) (Fig. 2e).

Due to the contact with the heated surface (8), the thermo-sensitive gel releases demineralized water from itself, which is taken through the channel (9) (Fig. 2g). After that, using the electronic control unit (1), the piston mechanism (2) is switched on again, returning the capacity (6) to the normal position. Then the cycle repeats.

If necessary, further reduce the concentrations of the depleted solution is passed through another desalination cascade, structurally completely similar to that described above.

The advantage of the invention in comparison with the prototype is to reduce energy costs for the desalination of solutions, such as saline groundwater or seawater.

Claims (1)

CLAIM A method of demineralizing solutions, including contacting a polyelectrolyte hydrogel with a solution of a low molecular weight salt, characterized in that the temperature-sensitive gel and the swollen polyelectrolyte hydrogel are contacted, while a portion of the solution accumulated by the polyelectrolyte hydrogel is transferred to a temperature-sensitive hydrogel, then the temperature-sensitive oven has been heated. to 50 ° C and separate the depleted solution from the heat-sensitive hydrogel.