RU2048449C1 - Method for desalting and purification of highly mineralized mine water - Google Patents

Abstract

FIELD: purification and desalting of highly mineralized water with element- by-element separation of products of purification. SUBSTANCE: method for desalting and purification of highly mineralized mine water includes stage electrochemical treatment in pulse magnetic field with step increase of frequency and decrease of amplitude of pulses from stage to stage. Current density at each stage of electrochemical treatment is established equal to (1-1,4)q_i, where q_i is specific electrode potential of one of elements with single concentration. Concentration of initial product at inlet of closed system is brought to preset value. Electrochemical treatment is carried out from element with maximum electrode potential to element with minimum electrode potential. Filtrate of the last stage is fed to inlet of closed system of stage treatment. EFFECT: higher efficiency. 3 cl, 1 dwg

Description

 The invention relates to the purification of highly mineralized wastewater from salts of various chemical elements dissolved in them and can be used for wastewater treatment of mines, quarries, galvanic drains, enterprises for the smelting of ferrous and non-ferrous metals, desalination of sea water and in other industries.

 A known method of treating wastewater from suspended and dissolved substances, including multi-stage sequential electrochemical treatment of the solution at different current densities in electroflotocoagulators equipped with blocks of various electrodes, electrocoagulation, flotation, activation and filtering of cleaning products.

 The disadvantages of this method are large energy costs and difficulties in the separation of cleaning products.

 A known method of purification of mineralized mine water, carried out by the method of electrodialysis, which is also associated with high energy consumption, is difficult to operate and does not fully provide waste-free technology.

 The purpose of the invention is the reduction of energy costs and the provision of waste-free technology by element-wise separation.

This goal is achieved by the fact that the method of desalination and purification of highly mineralized mine water, which includes supplying the initial product to the input of a closed system of stepwise electrochemical processing, changing the current density of the electrode blocks from stage to stage, coagulating and filtering the cleaning products, stepwise electrochemical processing is carried out in a pulsed electromagnetic field with a stepwise increase in frequency and a decrease in the amplitude of the field pulses from stage to stage. The current density of the electrode blocks at each stage of the electrochemical treatment is set equal to (1-1.4) q _i , where q _{i is the} specific electrode potential of one of the elements of the cleaning product at a unit concentration. The initial product is previously adjusted to a predetermined mineralization, and then fed to the input of stepwise processing. The filtrate of the last processing stage is fed to the input of a closed system of stepwise processing, which is conducted in sequence from the element with the maximum electrode potential to the element with the minimum electrode potential.

 Signs similar to those described in the characterizing part of the claims in the sources of patent and scientific and technical information were not found. Thus, the claimed method meets the criteria of the invention of "novelty."

 Comparison of the proposed solution with other technical solutions shows that in practice there are known methods of cleaning and desalination of highly mineralized mine and wastewater, including supplying the initial product to the input of a closed system of stepwise electrochemical processing with a stepwise change in the current density of electrode blocks from stage to stage, coagulation and filtering of products cleaning up. However, their use leads to relatively high energy costs for the treatment of wastewater, which makes this process expensive.

 Known purification methods do not provide waste-free technology, and most purification products, in the form of a conglomerate containing a number of elements, except purified water, are not used in the national economy. Expensive processes for cleaning mine highly mineralized waters do not pay off and are unprofitable for enterprises.

To eliminate this drawback, stepwise electrochemical processing is carried out in a pulsed electromagnetic field with a stepwise increase in frequency and a decrease in the amplitude of the field pulses from stage to stage. The current density of the electrode block at each stage of the electrochemical treatment is set equal to (1-1.4) q _i , where q _{i is the} specific electrode potential of one of the elements of the cleaning product at a unit concentration. The initial product is preliminarily adjusted to the desired mineralization, after which it is fed to the input of a closed system of stepwise processing, which is conducted in sequence from the element with the maximum electrode potential to the element with the minimum electrode potential.

 According to the proposed method, the initial highly mineralized mine water of a given concentration enters the first stage of electrochemical treatment, for example, in an electrolyzer equipped with at least a pair of electrodes, between which a predetermined current density is determined, determined experimentally and ensuring the breaking of internal bonds between ions of one of the desired elements to be extracted from source mine water. In order to provide the most effective redox reaction in solution between the electrodes to which an external voltage source is connected, one of the electrodes, for example, the anode, is received with an electrode potential lower than the electrode potential of the element to be extracted from the solution. As a result of the redox reaction of the aqueous solution between the electrodes, the desired element is restored, turning into a colloidal mass and settles to the bottom of the cell.

 To intensify coagulation of the sediment and its deposition on the bottom of the dishes, electrochemical treatment is carried out in a pulsed magnetic field. The frequency of the pulses is increased, and the amplitude is reduced from stage to stage. Electrochemical processing is carried out from an element with a large electrode potential (heavy) to an element with a lower electrode potential (lighter). First of all, less bound elements, for example silver, are extracted from the initial saline mine water, and, lastly, for example, sodium and potassium, which are strongly connected in an aqueous solution.

 The individual elements extracted from the source water in the electrolytic cells at each stage are fed to a filtration, which is carried out, for example, by centrifugation. After filtration at each stage, the solid phase of the deposited individual elements enters the individual storage hopper, and the liquid filtrate from each previous filtration stage enters the input of the subsequent stage of electrochemical treatment together with untreated water from the previous electrolyzer. The filtrate of the last stage is subjected to rapid analysis. At maximum permissible concentrations (MPC) of individual elements in purified water, it enters the catchment.

 If individual elements exceed the MPC, the treatment product (water) is fed to the input of the first stage of electrochemical treatment together with the source mine water, and the concentration of the solution is first adjusted to the specified mineralization and the total product is similarly cleaned.

 Thus, a special selection of the corresponding pairs of electrodes, current density during electrochemical treatment, taking into account the mineralization of the original mine water and the strength of the bonds of individual elements in the solution, their electrode potentials, as well as by intensifying the deposition of the desired element extracted from the solution by means of a predetermined pulsed magnetic field, is ensured minimum energy consumption for cleaning at each stage and in general for the entire technology.

 The purification products obtained at each stage in the form of oxides, hydroxides and individual elements, as well as purified water, can be successfully used in metallurgy, chemical production, light industry, etc. which gives reason to argue about non-waste technology for the treatment of highly mineralized mine water. The implementation of the obtained cleaning products pays off the preliminary capital costs of the equipment and will make it possible to profit at the enterprise. This allows us to conclude that the technical solution meets the criterion of "significant differences".

lg

B (1) где q_i стандартынй (единичный) потенциал, В;
Т 298 К абсолютная температура;
R 8,31 газовая постоянная,

;
F 96500 постоянная Фарадея, Кл/моль;
n число обменных электронов;
Ох концентрация окислительной формы;
Red концентрация восстановительной формы.PRI me R. The initial highly mineralized mine water with a total content of various elements in it up to 110 g / l and a concentration of some of them, g / l: Na + K 52; Cl 36; C 5.5: Fe 3; Mg 3; Cr 1.1; Mn 1.1; Ti 1.1; Zn 1.1; Pb 1.1; Al 1.1; Ni 0.033; Cu 0.033; Sn 0.033; Bi 0.022; Ag 0.0022; Ca 0.0011; Cd 0.0011; Zr 0.0011 is fed to the input of the first stage of a closed multi-stage, sequential electrochemical treatment carried out by, for example, electrolyzers. Each of the electrolyzers, the amount of which is determined by the number of individual chemical elements to be extracted, is equipped with at least a pair of electrodes, for example, metal. With a significant concentration in the water of ions of the same name with the immersed metal in mine water, cations from it will settle on the surface of the metal, which will be positively charged. A positively charged metal surface will attract negative ions, for example, SO ^-2 ₄ , and a double electric layer will form with a positively charged metal surface and negative of the negative anions dissolved in water. Between oppositely charged surfaces, a potential difference arises at the metal-solution interface. The formed metal solution pair is called the electrode, and the resulting potential difference is called the electrode potential. The electrode potentials of various metals immersed in solutions of different concentrations of mine water vary widely and are determined by the Nernst (Peters) formula:
E g _i +

lg

B (1) where q _{i is the} standard (unit) potential, V;
T 298 K absolute temperature;
R 8.31 gas constant,

;
F 96500 Faraday constant, C / mol;
n is the number of exchange electrons;
Oh, the concentration of the oxidizing form;
Red concentration of the reducing form.

The unit (reference) electrode potential q _i at a concentration of an element in a solution of 1 mol / L was taken as a unit of reference. The electrode unit potentials of the elements to be extracted from mine water are given below (+, 2 ⁺ valency of the element).

Unit electrode potential, B: K –2.925 Ca –2.866 Na –2.714 Mg –2.363 Al –1.622 Ti –1.628 Mn –1.180 Cr ²⁺ –0.913 Zn –0.763 Fe ²⁺ –0.440 Cd –0.403 Ca –0.277 Ni –0.250 Sn ²⁺ -0.136 Pb ²⁺ -0.126 2H 0 Bi 0.215 Cu ⁺ 0.337 Ag 0.799 Hg 0.854.

 Since the concentration of various elements and the total concentration of mine water varies widely, the electrode potential also undergoes a proportional change.

 An increase in the electrode potential corresponds to an increase in the oxidizing properties of the metal, and a decrease in the electrode potential enhances its reduction properties. Thus, potassium (K) is the easiest to give cations to the solution, is negatively charged and becomes a reducing agent.

 An electrode made of metal with a lower electrode potential will be a reducing agent with respect to the ions of all metals located after it electrode potentials. For example, aluminum will separate out iron, nickel, copper, zinc ions from a mine water solution, and silver ions as a strong oxidizing agent will restore pure silver from nitrites and silver sulfates.

The current carrier in mine water, which is a strong electrolyte, are ions of various elements. When a constant voltage source is connected to the electrodes, cations move to the cathode, and anions to the anode. Oppositely charged ions collide with each other and reduce the conductivity of the solution. In this regard, in highly concentrated mine water, not all ions participate in the creation of current and the concept of ion activity or active electrolyte concentration is introduced a:
a fC, (2) where f is the activity coefficient;
With concentration of mine water.

 Coefficient f shows the degree of difference in the activity of ions from their concentration in solution and should satisfy the value for dilute and concentrated solutions.

If there are ions of various elements in mine water, it is necessary to take into account the activity of each of them, which is associated with the complexity of the calculations. Therefore, the total concentration of all salts in a water solution is expressed in terms of the ionic strength (1) equal to the half-sum of the products of the concentration of each ion (C) by the square of its charge (n) or valency
I 0.5 (C ₁ n ₁ ² + C ₂ n ₂ ² + + C _n n _n ² ) A (3)
The number of ions of individual salts (elements) in the mine water solution is determined by the degree of electrolyte dissociation and their activity. Thus, knowing the ionic strength, it is possible to determine the ion activity coefficient. In practice, there is a rule that all substances dissociating into ions have activity coefficients independent of nature and its concentration, but dependent on the number and charges of ions.

 For the selective separation of individual elements from mine water, it is necessary for each stage of electrochemical treatment to determine the corresponding pairs of electrodes with electrode potentials sufficient to restore the desired element. As a rule, to isolate elements with high electrode potential (Ag, Cu, Ni, etc.) from mine water, electrodes with strong reducing properties (Al, Ti, Zn, Fe) are selected.

Ti²⁺+Cu^↓ (4)
Определяющими факторами выбора пары электродов, величины внешнего напряжения и плотности тока являются: искомый элемент для извлечения и его электродный потенциал, концентрация шахтной воды, электродные потенциалы пары электродов.For example, to isolate from a copper solution, titanium iron electrodes were adopted, when immersed in the solution, corresponding electrode potentials arise near them. At a unit concentration of elements in the solution, a current is established between the electrodes, which is determined by the sum of the electrode potentials of the received electrodes
q _Σ q _Ti + q _Fe = 1,628 + 0,44 2,068B
However, the magnitude of the current generated is insufficient to break the inter-element bonds in the mine water. To isolate the desired element, a constant voltage from an extraneous source is applied to the electrodes. At a certain voltage of 2-4 V (decomposition voltage), the current density through the mine water solution increases and an electrochemical reaction begins, at which, for example, titanium gives two electrodes to copper ions and it precipitates
Ti +

Ti ²⁺ + Cu ^↓ (4)
The determining factors for choosing a pair of electrodes, the magnitude of the external voltage and current density are: the desired element to extract and its electrode potential, the concentration of mine water, the electrode potentials of the pair of electrodes.

 The main requirements adopted as the basis in the proposed method for desalination and purification of mine water: reducing energy costs and ensuring waste-free technology due to the effective elementwise separation. To implement these requirements, experimentally select pairs of electrodes and establish at each stage of the electrochemical processing rational values of the current density as a function of the electrode potential of the desired element.

The results of the experiments are shown in the table on the example of extraction from mine water of copper with a large electrode potential (q _i 0.337 V), chromium with an average value q _i -0.113 V and sodium with a small electrode potential q _i -2.714 V.

As can be seen from the table, the rational value of the current density for these elements lies in the range (1-1,4) q _i (the coefficient value is determined by the resistance of the solution and the external voltage). In this case, maximum efficiency and selectivity of the selection of the desired element from the solution with minimal energy consumption is achieved. When the current density is less than (1-1.4) q _i , an effective extraction of the element from the solution is not achieved due to insufficient energy to break its ionic bonds with the solution, and the energy consumption increases due to an increase in the time of electrochemical processing. Efficient extraction of the desired elements is not achieved at a current density greater than (1-1,4) q _i , because in this case, the solution sharply increases the resistance due to collisions of the ions of the same name. Energy costs here increase due to a greater external voltage at the electrodes.

 Based on the experiments, it was found that the strongest oxidizing agents Ag, Cu, Bi, Ni, and Co are most easily released from mine water as elements that have a weak bond with water. The most difficult to isolate alkaline elements K, Ca, Na from the solution, because their activity in compounds with water is very high. In this regard, the electrochemical treatment of mine water and the separation of elements lead from elements with a large electrode potential to an element with a lower electrode potential.

 To isolate from mine water, for example, Na, mercury is taken as one of the electrodes (cathode), and graphite or iron is used as the anode. Since Na is contained in mine water in the form of a NaCl salt, during electrolysis, Cl is released at the anode, sodium at the cathode, which combines with mercury and forms sodium amalgam. The latter can be successfully used in the national economy.

 If the sodium amalgam is treated with hot water, then sodium interacts with water and highly concentrated caustic soda NaOH (up to 200-250 g / l) and hydrogen are obtained, and mercury is restored and again fed to the cathode bath.

In the process of electrochemical treatment of mine water at each stage, the desired element is formed in the form of a colloidal mass, which is slowly deposited on the bottom of the cell. In order to intensify the deposition of colloids in a solution, they are exposed to it by a pulsed magnetic field with a frequency of 30-60 kHz, under the influence of which coagulation of colloids occurs, the process of their deposition is intensified, and the whole process of electrochemical processing is accelerated. The frequency of the pulses is increased, and the amplitude is reduced to 1.6 · 10 ⁴ A / m ² at each stage. Their values are determined empirically to ensure maximum deposition rate of colloids. The mine water remaining after the previous stage enters the next stage, and the precipitate is fed to the filtration, which is carried out, for example, by centrifugation. The solid phase of the precipitate after filtration enters the accumulator, and the liquid filtrate from each previous stage enters the input of the subsequent stage of electrochemical treatment together with untreated mine water from the previous electrolyzer.

 The filtrate of the last stage of the electrochemical treatment is subjected to rapid analysis. At the maximum permissible concentration (MPC) of mineralization of purified water, it is fed to the catchment. If the water mineralization exceeds the MPC norms, the treatment product is fed to the input of the first stage of electrochemical treatment together with the source mine water. The concentration of the mine water mixture with the return filtrate is preliminarily adjusted to a predetermined value and the stepwise electrochemical processing of the total mixture is likewise conducted.

 According to experimental experiments, the claimed invention can be used for purification and desalination of highly mineralized mine water and, compared with the prototype, will allow more than 2 times to reduce the cost of the desalination process.

 The inventive method for desalination and purification of highly mineralized mine water will ensure waste-free technology due to the selective extraction of individual elements from mine water and successfully utilize the refined products, as well as obtain an economic effect.

 Desalination of highly mineralized mine water can improve the environmental situation in mining regions.

 The invention does not adversely affect the environment.

Claims (3)

1. METHOD OF DESCRIPTION AND CLEANING OF HIGH-MINERALIZED BINDING WATER containing various chemical elements, including its electrochemical treatment, characterized in that the initial water is mineralized to a predetermined degree before the electrochemical treatment, the electrochemical treatment is carried out by electrocoagulation stepwise with simultaneous separate electromagnetic field separation of elements with frequency and amplitude, respectively increasing and decreasing from stage to stage, and the current density at each stage equal to (1 1.4) q _i , where q _{i is the} standard electrode potential of the element released at this stage, the precipitate after each stage of electrocoagulation is separated from purified water, filtered, the filtrate obtained and purified water are fed to the following electrocoagulation stages .  2. The method according to claim 1, characterized in that the electrochemical treatment is carried out sequentially at the stage of separation of the elements with the maximum standard electrode potential to the stage of selection of the element and the minimum standard electrode potential. 3. The method according to p. 1, characterized in that the electrochemical treatment is carried out with increasing frequency of the pulsed electromagnetic field from stage to stage from 30 to 60 kHz and an amplitude of not more than 1.4 · 10 ⁴ A / m ² .

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