Electrochemical water treatment. Electrolysis
When a direct electric current is passed through an electrolyte, chemical reactions occur at the electrodes. This process is called electrolysis, which means the decomposition (of matter) by electricity.
In Sect. 8.1 it was indicated that an electrolyte is a liquid that, when an electric current is passed through it, undergoes a chemical reaction. The electrolyte can be a molten salt, such as molten lead(H) bromide, or an aqueous solution of an acid, base or salt.
Electric current is supplied to the electrolyte using electrodes - wire conductors, metal rods or plates that make electrical contact with the electrolyte. The negatively charged electrode is the cathode, and the positive electrode is the anode. Electrodes that do not enter into chemical reactions when in contact with electrolytes and when electric current is passed through them are called inert electrodes. Inert electrodes include graphite and platinum.
IONIC THEORY OF ELECTROLYSIS
According to this theory, the passage of direct electric current through the electrolyte is carried out with the help of ions. At the electrodes, electrons are transferred to or from ions. Therefore, the processes occurring on the electrodes can be considered as reduction or oxidation half-reactions. Thus, electrolysis is a redox process.
An oxidative half-reaction always takes place at the anode. In this reaction, anions lose electrons and are discharged, turning into neutral particles. Therefore, the anode acts as a sink for electrons from the anions.
A reduction half-reaction always occurs at the cathode. Here the cations acquire electrons and are discharged, turning into neutral particles. Therefore, the cathode acts as a source of electrons for cations.
Electrolysis of molten lead(H) bromide consists of two half-reactions:
1) bromide ions are discharged at the anode. (The equation for this half-reaction is
2Br-(g.) = Br2(g.) + 2e-
This half-reaction is an oxidation.)
2) lead ions are discharged at the cathode. (The equation for this half-reaction is:
Pb2+(sol.) + 2e- = Pb(l.)
This half-reaction is reduction.)
It should be noted that the reactions occurring at the anode and cathode in each specific system are predetermined by the polarity of the current source in the external electrical circuit. The negative terminal of the external current source (battery) supplies electrons to one of the electrodes of the electrolytic cell. This causes a negative charge on this electrode. It becomes the cathode. Since this electrode is negatively charged, it in turn causes an electrode reaction in which electrons are consumed. Thus, the reduction process takes place on this electrode. At the other electrode, electrons flow from the electrolytic cell back into the external circuit, making that electrode a positive electrode. This means that this electrode plays the role of an anode. Due to its positive charge, a reaction occurs on it, which is accompanied by the loss of electrons, i.e. oxidation.
A schematic representation of the entire electrolysis process is shown in Fig. 10.6.
The formation of an insoluble substance as a result of a chemical reaction is only one of the conditions for obtaining a colloidal solution. Another equally important condition is the inequality of the starting materials taken into the reaction. The consequence of this inequality is the limitation of the growth of particle size in colloidal solutions, which would lead to the formation of a coarsely dispersed system.
Let us consider the mechanism of formation of a colloidal particle using the example of the formation of a silver iodide sol, which is obtained by the interaction of dilute solutions of silver nitrate and potassium iodide.
AgNO 3 +KI = AgI + KNO 3
Ag + + NO 3 ¯ +K + + I ¯ = AgI ↓ + NO 3 ¯ + K +
Insoluble neutral silver iodide molecules form the core of the colloidal particle.
At first, these molecules combine in disorder to form an amorphous, loose structure, which gradually develops into a highly ordered crystalline core structure. In the example we are considering, the core is a crystal of silver iodide, consisting of a large number (m) of AgI molecules:
m - core of colloidal particle
An adsorption process occurs on the surface of the core. According to the Peskov-Fajans rule, ions that are part of the particle core are adsorbed on the surface of the cores of colloidal particles, i.e. silver ions (Ag +) or iodine ions (I –) are adsorbed. Of these two types of ions, those that are in excess are adsorbed.
Thus, if you obtain a colloidal solution in an excess of potassium iodide, then iodine ions will be adsorbed on the particles (nuclei), which complete the crystal lattice of the nucleus, naturally and firmly entering its structure. In this case, an adsorption layer is formed, which gives the core a negative charge:
Ions that are adsorbed on the surface of the nucleus, giving it a corresponding charge, are called potential-forming ions.
At the same time, there are also oppositely charged ions in the solution, they are called counterions. In our case, these are potassium ions (K +), which are electrostatically attracted to the charged nucleus (the charge value can reach I in). Some of the K+ counterions are firmly bound by electrical and adsorption forces and enter the adsorption layer. The core with a double adsorption layer of ions formed on it is called a granule.
(m . nI – . (n-x) K + ) x – (granule structure)
The remaining part of the counterions (we denote them by the number “x K +”) forms a diffuse layer of ions.
The core with adsorption and diffuse layers is called a micelle :
(m . nI –. (n-x) K + ) x – . x K + (micelle structure)
When a direct electric current is passed through a colloidal solution, the granules and counterions will move towards the oppositely charged electrodes, respectively.
The presence of the same charge on the surface of sols particles is important factor of its stability. The charge prevents particles from sticking together and becoming larger. In a stable disperse system, particles are kept in suspension, i.e. There is no precipitation of colloidal substance. This property of sols is called kinetics chemical stability.
The structure of micelles of silver iodide sol obtained in excess AgNO 3 is shown in Fig. 1a, in excess KCI - 1b .
Fig.1.5. The structure of micelles of silver iodide sol obtained in excess:
a) silver nitrate; b) potassium chloride.
Electrolysis- a redox process that occurs at the electrodes when a direct electric current is passed through a solution or molten electrolyte. In an electrolyzer, electrical energy is converted into chemical reaction energy.
Cathode (–) – negative electrode on which reduction occurs during electrolysis.
Anode (+) – positive electrode at which oxidation occurs during electrolysis.
Unlike electrolysis, in a galvanic cell, reduction occurs at the positively charged cathode, and oxidation occurs at the negatively charged anode.
In electrolysis, inert (insoluble) and active (consumable) anodes can be used. The active anode, when oxidized, sends its own ions into the solution. The inert anode is only a transmitter of electrons and does not change chemically. Graphite, platinum, and iridium are usually used as inert electrodes.
During the electrolysis of melts and solutions of electrolytes, the ions formed during their dissociation (under the influence of temperature or water) - cations (Kt n +) and anions (An m -) move, respectively, to the cathode (–) and anode (+). Then, at the electrodes, electrons are transferred from the cathode to the cation, and the anions give electrons to the anode.
Quantitatively, electrolysis is described by Faraday's two laws.
Faraday's first law: The mass of the substance released during electrolysis is proportional to the amount of electricity passing through the electrolyzer:
m = k∙ I∙τ = k∙Q ,
Where I– current strength; τ – current flow time; Q = I∙τ– amount of electricity; k– proportionality coefficient, the value of which depends on the chosen system of units (if Q = 1 Kl, then m = k).
The mass of substance released during the passage of 1 C of electricity is called electrochemical equivalent.
Faraday's II law: with the same amounts of electricity passed through the electrolyte, the number of gram equivalents of electrolysis products is the same.
To release one equivalent of any substance on the electrode, it is necessary to spend the same amount of electricity equal to Faraday constant F= 96485 C/mol. Indeed, one equivalent of a substance contains N A = 6.02322∙10 23 particles and to restore this number of singly charged ions at the cathode, it is necessary to expend the following amount of electricity:
F = N A∙ ē = 6.02322∙10 23 particles/mol ∙ 1.6021∙10 –19 C = 96485 C/mol,
where is the charge of the electron ē = 1.6021∙10 –19 Cl.
Generalizing both Faraday's laws, we can write:
Electroactivated water solutions - catholytes and anolytes can be used in agriculture, to increase plant productivity, in animal husbandry, medicine, for water disinfection and for domestic purposes. Electrochemical treatment of water includes several electrochemical processes associated with the transfer of electrons, ions and other particles in a constant electric field (electrolysis, electrophoresis, electroflotation, electrocoagulation), the main of which is water electrolysis. This article introduces the reader to the basic processes underlying the electrolysis of water.
Introduction
The phenomenon of electrochemical activation of water (ECAW) is a combination of electrochemical and electrophysical effects on water in the electric double layer (EDL) of electrodes (anode and cathode) with nonequilibrium charge transfer through the EDL by electrons and under conditions of intense dispersion of the resulting gaseous products of electrochemical reactions in the liquid. During the ECHA process, four main processes occur:
— electrolytic decomposition of water (electrolysis) due to redox reactions at the electrodes caused by an external constant electric field;
- electrophoresis - movement in an electric field of positively charged particles and ions to the cathode, and negatively charged particles and ions to the anode;
— electroflotation — the formation of gas flocculi and aggregates consisting of finely dispersed gas bubbles (hydrogen at the cathode and oxygen at the anode) and coarse water impurities;
- electrocoagulation - the formation of colloidal aggregates of particles of the deposited dispersed phase due to the process of anodic dissolution of the metal and the formation of metal cations Al 3+, Fe 2+, Fe 3+ under the influence of a constant electric field.
As a result of treating water with a direct electric current, at potentials equal to or exceeding the decomposition potential of water (1.25 V), water passes into a metastable state, characterized by anomalous values of electron activity and other physicochemical parameters (pH, Eh, ORP, electrical conductivity). The passage of a direct electric current through a volume of water is accompanied by electrochemical processes, as a result of which redox reactions occur, leading to the destruction (destruction) of water contaminants, coagulation of colloids, flocculation of coarse impurities and their subsequent flotation.
The phenomenon of electrochemical activation of water is a combination of electrochemical and electrophysical effects on water in a double electric layer of electrodes during nonequilibrium charge transfer.
Electrochemical treatment is used for clarification and decolorization of natural waters, their softening, purification from heavy metals (Cu, Co, Cd, Pb, Hg), chlorine, fluorine and their derivatives, for the purification of wastewater containing petroleum products, organic and organochlorine compounds, dyes , surfactant, phenol. The advantages of electrochemical water purification are that it allows you to adjust the values of the pH value and redox potential E h, on which the possibility of various chemical processes in water depends; increases the enzymatic activity of activated sludge in aeration tanks; reduces resistivity and improves conditions for coagulation and sedimentation of organic sediments.
In 1985, ECHA was officially recognized as a new class of physicochemical phenomena. By order of the Government of the Russian Federation dated January 15, 1998 No. VCh-P1201044, recommendations were given to ministries and departments to use this technology in medicine, agriculture, and industry.
Electrolysis of water
The main stage of electrochemical water treatment is water electrolysis. When a direct electric current is passed through water, the entry of electrons into the water at the cathode, as well as the removal of electrons from the water at the anode, is accompanied by a series of redox reactions on the surface of the cathode and anode. As a result, new substances are formed, the system of intermolecular interactions, the composition of water, including the structure of water, changes. A typical installation for electrochemical water treatment consists of a water preparation unit 1, an electrolyzer 2, a water treatment unit after electrochemical purification 3 (Fig. 1).
Some installations for electrochemical water treatment provide for preliminary mechanical purification of water, which reduces the risk of clogging the electrolytic cell with coarse impurities with high hydraulic resistance. A block for mechanical water purification is necessary if, as a result of electrochemical treatment, the water is saturated with coarse impurities, for example, flakes of metal hydroxides (Al(OH) 3, Fe(OH) 3, Mg(OH) 2) after electrocoagulation. The main element of the installation is an electrolyzer, consisting of one or several electrolysis cells (Fig. 2).
An electrolysis cell is formed by two electrodes - a positively charged anode and a negatively charged cathode, connected to different poles of a direct current source. The interelectrode space is filled with water, which is an electrolyte capable of conducting electric current. As a result of the operation of the device, electrical charges are transferred through a layer of water - electrophoresis, that is, the migration of polar particles, charge carriers - ions, to electrodes that have the opposite sign.
When a direct electric current is passed through water, the entry of electrons into the water at the cathode, as well as the removal of electrons from the water at the anode, is accompanied by a series of redox reactions on the surface of the cathode and anode.
In this case, negatively charged anions move to the anode, and positively charged cations move to the cathode. At the electrodes, charged ions lose their charge, depolarize, turning into decay products. In addition to charged ions, polar particles of various dispersions participate in electrophoresis, including coarse particles (emulsified particles, gas bubbles, etc.), but the main role in the transfer of electrochemical charges is played by charged ions with the greatest mobility. Polar particles include polar particles from aqueous impurities and water molecules, which is explained by their special structure.
The central oxygen atom, which is part of the water molecule, has a higher electronegativity than hydrogen atoms, attracts electrons to itself, giving the molecule asymmetricity. As a result, a redistribution of electron density occurs: the water molecule is polarized, taking on the properties of an electric dipole having a dipole moment of 1.85 D (Debye), with positive and negative charges at the poles (Fig. 3).
The products of electrode reactions are neutralized aqueous impurities, hydrogen and oxygen gases formed during the electrolytic destruction of water molecules, metal cations (Al 3+, Fe 2+, Fe 3+) in the case of using metal anodes made of aluminum and steel, molecular chlorine, etc. In this case, hydrogen gas is generated at the cathode, and oxygen at the anode. The water contains a certain amount of hydronium ion H 3 O +, which depolarizes on the surface of the cathode to form atomic hydrogen H:
H 3 O + + e - → H + H 2 O.
In an alkaline environment, H 3 O + is absent, but water molecules are destroyed, accompanied by the formation of atomic hydrogen H— and hydroxydione OH -:
H 2 O + e - → H + OH - .
Reactive hydrogen atoms are adsorbed on the cathode surfaces and, after recombination, form molecular hydrogen H2, which is released from water in gaseous form:
N + N → N 2.
At the same time, atomic oxygen is released at the anodes. In an acidic environment, this process is accompanied by the destruction of water molecules:
2H 2 O - 4e - →O 2 +4H +.
In an alkaline environment, the source of oxygen formation is always the hydroxide ions OH -, which move under the action of electrophoresis on the electrodes, from the cathode to the anode:
4 OH - → O 2 + 2 H 2 O + 4 e - .
The normal redox potentials of these reactions are +1.23 and +0.403 V, respectively, but the process occurs under conditions of some
overvoltage. An electrolysis cell can be considered as a generator of the above-mentioned products, some of which, entering into chemical interaction with each other and with water contaminants in the interelectrode space, provide additional chemical purification of water (electroflotation, electrocoagulation). These secondary processes do not occur on the surface of the electrodes, but in the volume of water. Therefore, in contrast to electrode processes, they are designated volumetric. They are initiated by an increase in water temperature during electrolysis and an increase in pH during the cathodic destruction of water molecules.
A distinction is made between cathodic and anodic oxidation. During cathodic oxidation, molecules of organic substances, sorbed on cathodes, accept free electrons, are reduced, transforming into compounds that are not pollutants. In some cases, the recovery process takes place in one stage:
R + H + + e - → RH, where R is an organic compound; RH is the hydrated form of the compound and is not a contaminant.
In other cases, cathodic reduction takes place in two stages: in the first stage (I), the organic molecule is converted into an anion, in the second (II), the anion is hydrated, interacting with a water proton:
R + e - → R - , (I) R - + H + → RH. (II)
A distinction is made between cathodic and anodic oxidation. During cathodic oxidation, molecules of organic substances, sorbed on cathodes, accept free electrons and are reduced.
Cathodes made of materials that require high overvoltage (lead, cadmium) make it possible, with a large expenditure of electricity, to destroy organic molecules and generate reactive free radicals - particles that have free unpaired electrons in the outer orbits of atoms or molecules (Cl*, O*, OH* , BUT*2, etc.). The latter circumstance gives free radicals the property of reactivity, that is, the ability to enter into chemical reactions with aqueous impurities and destroy them.
RH → R + H + + e - .
Anodic oxidation of organic compounds often leads to the formation of free radicals, the further transformations of which are determined by their reactivity. Anodic oxidation processes are multistage and occur with the formation of intermediate products. Anodic oxidation reduces the chemical stability of organic compounds and facilitates their subsequent destruction during bulk processes.
In volumetric oxidative processes, a special role is played by the products of water electrolysis - oxygen (O 2), hydrogen peroxide (H 2 O 2) and oxygen-containing chlorine compounds (HClO). During the electrolysis process, an extremely reactive compound is formed - H 2 O 2, the formation of molecules of which occurs due to hydroxyl radicals (OH*), which are the products of discharge of hydroxyl ions (OH-) at the anode:
2OH - → 2OH* → H 2 O 2 + 2e - , where OH* is the hydroxyl radical.
Reactions between organic substances and oxidizing agents occur over a certain period of time, the duration of which depends on the value of the redox potential of the element and the concentration of the reacting substances. As purification and contaminant concentrations decrease, the oxidation process decreases.
The rate of the oxidation process during electrochemical treatment depends on the temperature of the water being treated and the pH. During the oxidation of organic compounds, intermediate products are formed that differ from the original one both in their resistance to further transformations and in their toxicity.
The source of active chlorine and its oxygen-containing compounds generated in the electrolyzer are chlorides found in the treated water and sodium chloride (NaCl), which is introduced into the treated water before electrolysis. As a result of anodic oxidation of Cl— anions, chlorine gas Cl 2 is generated. Depending on the pH of the water, it either hydrolyzes to form hypochlorous acid HOCl, or forms hypochlorite ions ClO - . The equilibrium of the reaction depends on the pH value.
At pH = 4-5, all chlorine is in the form of hypochlorous acid (HClO), and at pH = 7, half of the chlorine is in the form of hypochlorite ion (OCl -) and half is in the form of hypochlorous acid (HClO) (Fig. 4). The mechanism of interaction of the hypochlorite ion (ClO -) with the oxidized substance is described by the following equation:
ClO - + A = C + Cl, where A is the oxidizable substance; C is an oxidation product.
Electrochemical oxidation of organic compounds with hypochlorithione (ClO -) is accompanied by an increase in the redox potential Eh, which indicates the predominance of oxidative processes. The increase in Eh depends on the ratio of the concentration of active chlorine in the interelectrode space to the content of organic impurities in water. As the amount of pollution is cleaned and the amount of pollution decreases, this ratio increases, which leads to an increase in Eh, but then this indicator stabilizes.
The amount of substance that reacted on the electrodes when passing a direct electric current according to Faraday’s law is directly proportional to the current strength and processing time:
G = AI cur τ, (1)
where A is the electrochemical equivalent of the element, g/(A⋅h); I cur—current strength, A; τ — processing time, hours. The electrochemical equivalent of an element is determined by the formula:
A = M/26.8z, (2)
where M is the atomic mass of the element, g; z is its valence. The values of electrochemical equivalents of some elements are given in table. 1.
The actual amount of substance generated during electrolysis is less than the theoretical one, calculated using formula (1), since part of the electricity is spent on heating water and electrodes. Therefore, the calculations take into account the current utilization factor η< 1, величина которого определяется экспериментально.
During electrode processes, charged particles and ions are exchanged between the electrode and the electrolyte - water. To do this, under established equilibrium conditions, it is necessary to create an electrical potential, the minimum value of which depends on the type of redox reaction and on the water temperature at 25 °C (Table 2).
The main parameters of water electrolysis include current strength and density, voltage within the electrode cell, as well as the speed and duration of water residence between the electrodes.
The voltages generated in the electrode cell must be sufficient to cause redox reactions to occur on the electrodes. The voltage value depends on the ionic composition of water, the presence of impurities in water, for example surfactants, current density (its strength per unit area of the electrode), electrode material, etc. All other things being equal, the task of choosing an electrode material is to reduction reactions on the electrodes, the required voltage was minimal, since this reduces the cost of electrical energy.
Some redox reactions are competitive - they occur simultaneously and mutually inhibit each other. Their flow can be regulated by changing the voltage in the electrolytic cell. Thus, the normal reaction potential for the formation of molecular oxygen is +0.401 V or +1.23 V; when the voltage increases to +1.36 V (the normal potential of the reaction for the formation of molecular chlorine), only oxygen will be released at the anode, and with a further increase in the potential, both oxygen and chlorine will be released simultaneously, and the release of chlorine will occur with insufficient intensity. At a voltage of about 4-5 V, the evolution of oxygen will practically stop, and the electrolytic cell will generate only chlorine.
Calculation of the main parameters of the water electrolysis process
The main parameters of water electrolysis include current strength and density, voltage within the electrode cell, as well as the speed and duration of residence of water in the interelectrode space.
The current strength I cur is a value determined depending on the required performance of the generated product [A], determined by the formula:
I cur = G/A tη, (3)
This formula is obtained by transforming formula (1) taking into account the current utilization factor η. Current density is its strength per unit area of the electrode [A/m 2 ], for example, the anode, is determined from the following expression:
i an = I cur / F an, (4)
where Fan is the anode area, m2. Current density has the most decisive influence on the electrolysis process: that is, with an increase in current density, electrode processes intensify and the surface area of the electrodes decreases, but at the same time the voltage in the electrolysis cell and, as a consequence, the entire energy intensity of the process increase. An increased increase in current density intensifies the release of electrolysis gases, leading to bubbling and dispersion of insoluble products of electrical water treatment.
As the current density increases, passivation of the electrodes also increases, which consists in blocking incoming electrons by surface deposits of the anode and cathode, which increases the electrical resistance in the electrode cells and inhibits the redox reactions occurring on the electrodes.
Anodes are passivated as a result of the formation of thin oxide films on their surfaces as a result of sorption of oxygen and other components on the anodes, which, in turn, sorb particles of aqueous impurities. Carbonate deposits are mainly formed on the cathodes, especially in the case of treating water with increased hardness. For these reasons, the current density during water electrolysis should be set to the minimum under the conditions for the stable occurrence of the necessary redox reactions during the technological process.
The length of time water remains in the interelectrode space of the electrolyzer is limited by the time required to generate the required amount of electrolysis products.
The voltage in the electrode cell [V] is determined by the formula:
V i = i an ΔK g / χ R , (5)
where i an is the current density, A/m 2 ; D—distance between electrodes (width of the interelectrode channel), m; χ R—specific electrical conductivity of water, 1/(Ohm⋅m); K g is the gas filling coefficient of the interelectrode space, usually taken K g = 1.05-1.2.
Formula (5) does not take into account the electrical resistance of the electrode due to their low values, but during passivation these resistances turn out to be significant. The width of the interelectrode channel is assumed to be minimal (3-20 mm) to ensure that it is not clogged with impurities.
The specific electrical conductivity of water χ R depends on a number of factors, among which the most significant are temperature, pH, ionic composition and ion concentration (Fig. 5). With increasing temperature, electrical conductivity χ R increases and voltage decreases (Fig. 6). The minimum value of electrical conductivity corresponds to pH = 7. In addition, during the electrolysis process, the temperature and pH of the water increase. If pH > 7, then we can expect a decrease in the specific electrical conductivity of water χ R, and at pH values< 7 удельная электропроводность воды χ R , наоборот, возрастает (рис. 5).
The specific electrical conductivity of natural waters of medium mineralization is 0.001-0.005 1/(Ohm⋅m), urban waste water is 10-0.01 1/(Ohm⋅m). During electrolysis, the specific electrical conductivity should be in the range of 0.1-1.0 1/ (Ohm⋅m). If the source water has insufficient electrical conductivity, the salt content should be increased (Fig. 7). Typically, sodium chloride (NaCl) is used for this, the doses of which are determined experimentally and most often amount to 500-1500 mg/l (8-25 mEq/l). Sodium chloride is not only convenient in terms of use and safety (storage, solution preparation, etc.), but in the presence of NaCl the passivation of the electrodes slows down. By dissociating in water, NaCl saturates the water with chlorine anions Cl - and sodium cations Na +. Chlorine ions Cl - are small in size and, penetrating through passivating deposits to the anode surface, destroy these deposits. In the presence of other anions, especially sulfate ions (SO 2-4), the depassivating effect of chlorine ions (Cl -) decreases. Stable operation of the electrolyzer is possible if the ions - Cl - make up at least 30% of the total number of anions. Sodium cations Na + as a result of electrophoresis move to the cathodes, on which hydroxide ions OH - are generated, and, interacting with the latter, form sodium hydroxide (NaOH), which dissolves carbonate deposits on the cathodes.
The power consumption [W] of the electrolyser is determined by the following relationship:
N consumption = η e I cur V e, (6)
where η e is the efficiency of the electrolyzer, usually taken η e = 0.7-0.8; I cur—current strength, A; V e is the voltage on the electrolyzer, V.
The residence time of water in the interelectrode space of the electrolyzer is limited by the time required to generate the required amount of electrolysis products, as well as the duration of the corresponding volume reactions, and is determined experimentally.
The speed of water movement in the interelectrode space is set taking into account the conditions for the removal of electrolysis products and other impurities from the electrolyzer; In addition, turbulent mixing depends on the speed of water movement, which affects the course of volumetric reactions. Like the residence time of the water, the water speed is selected based on experimental data.
To be continued.
1. Bakhir V.M., Liakumovich A.G., Kirpichnikov P.A., Spector L.E., Mamadzhanov U.D. Physical nature of the phenomena of activation of substances // Izv. Academy of Sciences of the UzSSR. Ser. tech. nauk., No1/1983.
2. Kulsky L.A. Water purification by electrocoagulation / L.A. Kulsky, P.P. Strokach, V.A. Slipchenko and others - Kyiv: Budivelnik, 1978.
3. Lipovetsky Ya.M. Electrochemical methods for purification of drinking and waste waters / Ya.M. Lipovetsky, Ya.D. Rappoport - M.: CBNTI of the Ministry of Housing and Communal Services of the RSFSR, 1985.
4. Kirpichnikov P.A., Bakhir V.M., Gamer P.U., Dobrenkov G.A., Liakumovich A.G., Fridman B.S., Agadzhanyan S.I. On the nature of electrochemical activation of media // Dokl. USSR Academy of Sciences, No. 3/1986, T. 286.
5. Bakhir V.M., Zadorozhny Yu.G. Electrochemical reactors RPE. - M.: "Hyperox", 1991.
6. Yakovlev S.V. Technology of electrochemical water purification / S.V. Yakovlev, I.G. Krasnoborodko, V.M. Rogov. — L.: L.O. Stroyizdat, 1987.
7. Bakhir V.M. Modern technical electrochemical systems for disinfection, purification and activation of water. - M.: VNIIIMT, 1999.
8. Bakhir V.M., Zadorozhny Yu.G., Leonov B.I., Panicheva S.A., Prilutsky V.I. Electrochemical activation: water purification and production of useful solutions. - M.: VNIIIMT, 2001.
9. Kulsky L.A. Handbook on properties, methods of analysis and purification of water. Part 1 / L.A. Kulsky, I.T. Goronovsky, A.M. Koganovsky and others - Kyiv: Naukova Dumka, 1980.
10. Medrish G.L. Disinfection of natural and waste waters using electrolysis / G.L. Medrish, A.A. Taisheva, D.L. Basin. - M.: Stroyizdat, 1982.
11. Volovnik G.I. Theoretical foundations of water purification / G.I. Volovnik, L.D. Terekhov. Part 1. - Khabarovsk: Publishing House DVGUPS, 2000.
12. Bakhir V.M. Electrochemical activation. Part 2. - M.: VNIIII honey. technology, 1992.
13. Babtsova N.F., Komarov I.F. Experience of using the STEL installation in the surgical department / II Int. symp. "Electr. activation”, Part 1. - M., 1999.
14. Leonov B.I., Prilutsky V.I., Bakhir V.M. Physicochemical aspects of the biological action of electrochemically activated water. - M.: VNIIIMT, 1999.
15. Bakhir V.M. Theoretical aspects of electrochemical activation / II Int. symp. "Electr. activation". Part 1. - M., 1999.
16. Toropkov V.V., Altshul E.B., Toropkova E.V. Toxicological characteristics of the drug catholyte / III Int. symp. "Electr. activation". - M., 2001.
17. Leonov B.I., Bakhir V.M., Vtorenko V.I. Electrochemical activation in practical medicine / II Int. symp. “Electrochemical activation”, Part 1. - M., 1999.
18. Toropkov V.V. Altshul E.B., Peresypkin O.I. Pharmacological effectiveness of the action of anolytes AN and ANK on the mucous membranes of the oral cavity / II Int. symp. "Electr. activation" // Abstracts, reports. and message Part 1. - M., 1999.
19. Prilutsky V.I., Bakhir V.M. Electrochemically activated water: anomalous properties, mechanism of biological action. - M.: VNIIIMT, 1997.
20. Panicheva S.A. New technologies for disinfection and sterilization of complex medical products. - M.: VNIIIMT, 1998.
1. What was observed in Oersted's experiment?
a) Interaction of two parallel conductors with current.
b) Interaction of two magnetic needles.
c) Rotation of a magnetic needle near a conductor when current is passed through it.
d) The appearance of an electric current in a coil when a magnet is placed in it.
2. How do two parallel conductors interact with each other if currents flow through them in the same direction?
a) They are attracted. b) They push off. c) The interaction force is zero. d) The correct answer is not given.
3. When a direct electric current is passed through a conductor, a magnetic field appears around it. It is detected by the location of steel filings on a sheet of paper or the rotation of a magnetic needle located near a conductor. How can this magnetic field be moved in space?
a) Transferring steel filings. b) Transfer of a magnet. c) Transfer of a conductor with current. d) The magnetic field cannot be moved.
4. How will the magnetic needles placed at points A and B inside the coil be positioned when key K is opened?
a) The same north pole to the right according to the figure.
b) The same north pole to the left according to the figure.
c) The arrows have their north poles facing each other.
d) The arrows have their south poles facing each other.
5. Why is the design of AC motors simpler than DC motors? Why are DC motors used in transport?
6. Determine the poles of the electromagnet.
7. Draw the magnetic field of currents and determine the direction of the magnetic field lines.
8. Determine the direction of the force acting on a current-carrying conductor placed in a magnetic field.
9. You have three objects - “devices”: a wooden block, two steel nails that are not attracted to each other, and a permanent magnet.
The three “black boxes” contain, respectively: a magnet, two nails and a wooden block. What instruments and in what order are best to use to find out what is in each drawer?
10. A DC electric motor consumes a current of 2 A from a 24 V source. What is the mechanical power of the motor if its winding resistance is 3 Ohms? What is its efficiency?
Determine the direction of the current in the conductor, the cross-section of which and the magnetic field are shown in Figure 1.3. What direction is the current in the conductor, the direction of the magnetic field lines of which is indicated by arrows (Fig. 3)?
5. Based on the direction of the magnetic lines of force shown in Figure 5, determine the direction of the circular current in the ring.
Electromagnetic waves arise: A. When electric charges move at a constant speed. B. With accelerated movement of electricB. Around stationary charges.
D. Around a stationary conductor through which a constant electric current passes.
D. Around a stationary charged metal plate
1. Electric current is called... A). movement of electrons. B). ordered movement of charged particles. B). ordered movement of electrons. 2.To create an electric current in a conductor, you must... A). create an electric field in it. B). create electrical charges in it. B). separate electrical charges in it. 3. What particles create electric current in metals? A). Free electrons. B). Positive ions. B). Negative ions. ^ 4. What effect of current is used in galvanometers? A. Thermal. B. Chemical. B. Magnetic. 5. The current strength in the circuit of an electric stove is 1.4 A. What electric charge passes through the cross section of its spiral in 20 minutes? A). 3200 Kl. B). 1680 Cl. B). 500 Kl. ^ 6. In which diagram (Fig. 1) is the ammeter connected to the circuit correctly? A). 1. B). 2. B). 3. 7. When an electric charge equal to 6 C passes through a conductor, 660 J of work is performed. What is the voltage at the ends of this conductor? A). 110 V. B). 220 V.V). 330V. ^ 8. In which diagram (Fig. 2) is the voltmeter connected to the circuit correctly? A). 1. B). 2. 9. Two coils of copper wire of the same cross-section have lengths of 50 and 150 m, respectively. Which of them has greater resistance and by how much? A). The first is 3 times. B). The second is 3 times. ^ 10. What is the current strength passing through a nickel wire with a length of 25 cm and a cross-section of 0.1 mm2, if the voltage at its ends is 6 V? A). 2 A. B). 10 A. B). 6 A
1. In what units is electric current measured? A. Ohm; B.J; W. W.; G.A.2. What actions always occur when electric current passes through any medium?
A. Thermal; B. Magnetic; IN. Chemical; G. Light.
4. Determine what voltage the light bulb is under if 2200 J of work is done when moving a 10 C charge.
5. Determine the resistance of section AB in the circuit shown in the figure.
6. Calculate the resistance of a nichrome wire whose length is 150 m and cross-sectional area is 0.2 mm2.
7. A copper conductor with a cross section of 3.5 mm2 and a length of 14.2 m carries a current of 2.25 A. Determine the voltage at the ends of this conductor.
8. How many electrons pass through the cross-section of a conductor in 35 s when the current in it is 16 A?
9. Determine the mass of iron wire with a cross-sectional area of 2 mm2, taken to make a resistor with a resistance of 6 ohms.
