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Claimed 11L1!.1964 (No. 886625/22-2) Class. 40s, Zoo with attachment of application No. IPC C 22d

UDC 669.174: 669.177.035.

45 (088.8) State Committee for Inventions and Discoveries of the USSR

Applicant Central Research Institute of Ferrous Metallurgy named after I.P. Bardin

METHOD FOR PRODUCING IRON BY ELECTROLYSIS

MOLTEN SALT WITH SOLUBLE ANODES

Subject of invention

Signature group ¹ 1bO

Known methods for producing iron and other metals in aqueous solutions and in molten salts, The proposed method for producing iron by electrolysis of molten salts with soluble anodes from cast iron or products of non-domain reduction of iron ore material differs from the known ones in that to obtain iron of high purity, electrolysis is carried out in molten sodium chloride with the addition of iron chloride in an amount of not more than 10 ", by weight, based on iron, at 850 - 900 C and anode and cathode current densities, respectively, up to 0.4 and 10 A / cm-.

According to the proposed method, the initial iron-containing materials in the form of lumps, briquettes, granules, chips or plates are loaded into an electrolysis cell, for example, with a ceramic lining, and subjected to electrical refining at 850 - 900 C in an atmosphere of nitrogen or other inert gas.

Powdered pure iron deposited on the cathode is periodically discharged from the bath and crushed to separate by air separation a part of the electrolyte returned to the bath. The residual electrolyte is separated from the iron by vacuum separation at 900 - 950 C or by hydrometallurgical treatment.

The advantage of the proposed method is the increased purity of iron with the content of the main element up to 99.995%. and

Method for obtaining iron by electrolysis of molten salts with soluble anodes15 from cast iron or products of non-domain reduction of iron ore material, characterized in that, in order to obtain iron of increased purity, electrolysis is carried out in molten sodium chloride with

20 with the addition of ferric chloride in an amount of not more than 10% by weight, calculated as iron, with

850 - 9 C and anode and cathode current densities, respectively, up to 0.4 and 10 A / s -.

Similar patents:

The invention relates to the field of electrochemical production of powders of platinum group metals and can be used for catalysis in the chemical industry, electrochemical energy, microelectronics

Option 1

1. Write the reaction equations: a) obtaining zinc from zinc oxide by reduction with coal; b) obtaining cobalt from cobalt (II) oxide by reduction with hydrogen; c) obtaining titanium from titanium chloride (IV) magnesium by thermal means. Disassemble the reaction as a redox reaction: designate the oxidation states of the atoms and arrange the coefficients, determining them by the electron balance method.

2. Make diagrams and equations of reactions occurring during electrolysis: a) potassium chloride melt; b) zinc bromide solution; c) iron sulfate solution (II).

3. What is the essence of metal corrosion? What types of corrosion do you know?
Corrosion is the spontaneous destruction of metals and alloys as a result of chemical, electrochemical or physico-chemical interaction with the environment.

4. A copper rivet is placed on the steel cover. What will collapse first - the lid or the rivet? Why?
A steel cover because it includes iron, and iron is a more reactive metal than copper and will corrode more quickly. Also, iron and copper form a galvanic pair, where iron is the anode, and is destroyed more quickly, into copper - the cathode, remains intact.

Option 2

1. Write the reaction equations: a) obtaining iron from iron oxide (III) by aluminothermic method; b) obtaining copper from copper (II) oxide by reduction with coal; c) obtaining tungsten from its higher oxide by reduction with hydrogen. Disassemble the reaction as a redox reaction: designate the oxidation states of the atoms and arrange the coefficients, determining them by the electron balance method.

2. Make diagrams and equations of reactions occurring during electrolysis: a) a solution of copper (II) bromide; b) sodium iodide solution; c) a solution of lead (II) nitrate.

3. What factors lead to increased corrosion of metals?

4. Why is a tin-plated (tin-plated) iron tank quickly destroyed at the site of damage to the protective layer?
Also, iron and tin form a galvanic cell, where iron is the anode, and is destroyed more quickly, while tin, the cathode, remains intact.

Option 3

1. Write the reaction equations: a) obtaining copper from copper (II) oxide by reduction with hydrogen; b) obtaining iron from iron oxide (III) by reduction with carbon monoxide (II); c) obtaining vanadium from vanadium (V) oxide by the calcium thermal method. Disassemble the reaction as a redox reaction: designate the oxidation states of the atoms and arrange the coefficients, determining them by the electron balance method.

2. Make diagrams and equations of reactions occurring during electrolysis: a) calcium chloride melt; b) potassium bromide solution; c) zinc sulfate solution.

3. What factors contribute to slowing down the corrosion of metals?
- Neutralization or deoxygenation of corrosive environments, as well as the use of various kinds of corrosion inhibitors;
- Removal of impurities from a metal or alloy that accelerate the corrosion process (elimination of iron from magnesium or aluminum alloys, sulfur from iron alloys).
- Elimination of unfavorable metal contacts or their isolation, elimination of cracks and gaps in the structure, elimination of moisture stagnation zones.

4. Which metals, upon mutual contact in the presence of an electrolyte, are destroyed faster: a) copper and zinc; b) aluminum and iron? Why?
The more active metal from a given pair will break down faster
a) zinc is a more active metal than copper;
b) aluminum is a more active metal than iron.

Option 4

1. Write the reaction equations: a) obtaining molybdenum from its higher oxide by reduction with hydrogen; b) obtaining chromium from chromium (III) oxide by aluminothermic method; c) obtaining nickel from nickel oxide (II) by reduction with coal. Disassemble the reaction as a redox reaction: designate the oxidation states of the atoms and arrange the coefficients, determining them by the electron balance method.

2. Make diagrams and equations of reactions occurring during electrolysis: a) a solution of copper (II) chloride; b) sodium iodide solution; c) nickel (II) nitrate solution.

3. List ways to combat corrosion of metals.

4. Why is zinc destroyed on a galvanized tank at the place of a scratch, and iron does not rust?
Zinc is a more active metal than iron. Also, iron and zinc form a galvanic cell, where zinc is the anode, and is destroyed more quickly, while iron, the cathode, remains intact.

In connection with the appearance of a certain gas, causing an instant burning cough. This article is the identification of this gas. The article is replete with formulas; the number of formulas is due to the non-triviality of both the electrolysis process itself and the rust itself. Chemists and chemists, help bring the article to full compliance with reality; it is your duty to take care of the "little" brothers in the event of a chemical hazard.

Let there be iron Fe 0:
- if there was no water on Earth, then oxygen would fly in - and made oxide: 2Fe + O 2 \u003d 2FeO (black). The oxide oxidizes further: 4FeO + O 2 = 2Fe 2 O 3 (red-brown). FeO 2 does not exist, these are schoolchildren's inventions; but Fe 3 O 4 (black) is quite real, but artificial: the supply of superheated steam to iron or the reduction of Fe 2 O 3 with hydrogen at a temperature of about 600 degrees;
- but there is water on Earth - as a result, both iron and iron oxides tend to turn into the base Fe (OH) 2 (white ?!. It quickly darkens in the air - is it not a point below): 2Fe + 2H 2 O + O 2 \u003d 2Fe(OH) 2 , 2FeO + H 2 O = 2Fe(OH) 2 ;
- further even worse: there is electricity on Earth - all these substances tend to turn into the base Fe (OH) 3 (brown) due to the presence of moisture and potential difference (galvanic couple). 8Fe(OH) 2 + 4H 2 O + 2O 2 = 8Fe(OH) 3 , Fe 2 O 3 + 3H 2 O = 2Fe(OH) 3 (slowly). That is, if iron is stored in a dry apartment, it rusts slowly, but holds on; increase the humidity or wet it - it will become worse, and stick it into the ground - it will be very bad.

Preparing a solution for electrolysis is also an interesting process:
- first, the analysis of the available substances for the preparation of solutions is carried out. Why soda ash and water? Soda ash Na 2 CO 3 contains Na metal, which is much to the left of hydrogen in a number of electrical potentials - which means that during electrolysis the metal will not be reduced at the cathode (in solution, but not in melt), and water will decompose into hydrogen and oxygen (in solution). There are only 3 variants of the reaction of the solution: metals much to the left of hydrogen are not reduced, weakly to the left of hydrogen they are reduced with the release of H 2 and O 2, to the right of hydrogen they are simply reduced at the cathode. Here it is, the process of copper plating of the surface of parts in a CuSo 4 solution, galvanizing in ZnCl 2, nickel plating in NiSO 4 + NiCl 2, etc.;
- to dilute soda ash in water stands in calm, slowly and without breathing. Do not tear the package with your hands, but cut it with scissors. After that, the scissors must be put in the water. Any of the four types of soda (food, soda, washing, caustic soda) takes moisture from the air; its shelf life, in fact, is determined by the time of accumulation of moisture and clumping. That is, in a glass jar, the shelf life is eternity. Also, any soda generates a sodium hydroxide solution when mixed with water and electrolysis, differing only in the concentration of NaOH;
- soda ash is mixed with water, the solution becomes bluish in color. It would seem that a chemical reaction has taken place - but not: as in the case of table salt and water, the solution does not have a chemical reaction, but only a physical one: the dissolution of a solid in a liquid solvent (water). You can drink this solution and get mild to moderate poisoning - nothing fatal. Or evaporate and get soda ash back.

The choice of anode and cathode is a whole undertaking:
- it is advisable to choose the anode as a solid inert material (so that it does not collapse, including from oxygen, and does not participate in chemical reactions) - that is why stainless steel acts as it (I read heresy on the Internet, I almost got poisoned);
- it is pure iron that is the cathode, otherwise rust will act as an excessively high resistance of the electrical circuit. To place the iron to be purified completely into the solution, you need to solder or screw it to some other iron. Otherwise, the metal of the iron holder itself will take part in the solution as a non-inert material and as a section of the circuit with the least resistance (parallel connection of metals);
- not yet specified, but there should be a dependence of the flowing current and electrolysis rate on the surface area of ​​the anode and cathode. That is, one M5x30 stainless steel bolt may not be enough to quickly remove rust from a car door (to realize the full potential of electrolysis).

Let's take an inert anode and cathode as an example: considering the electrolysis of only a blue solution. As soon as voltage is applied, the solution begins to transform to the final one: Na 2 CO 3 + 4H 2 O \u003d 2NaOH + H 2 CO 3 + 2H 2 + O 2. NaOH - sodium hydroxide - mad alkali, caustic soda, Freddy Krueger in a nightmare: the slightest contact of this dry substance with wet surfaces (skin, lungs, eyes, etc.) causes hellish pain and fast irreversible (but recoverable with a mild degree of burn ) damage. Fortunately, sodium hydroxide is dissolved in carbonic acid H 2 CO 3 and water; when the water is finally evaporated by hydrogen at the cathode and oxygen at the anode, the maximum concentration of NaOH in carbonic acid is formed. It is absolutely impossible to drink or smell this solution, it is also impossible to poke your fingers (the longer the electrolysis, the more it burns). You can clean the pipes with it, while understanding its high chemical activity: if the pipes are plastic, you can hold them for 2 hours, but if they are metal (grounded, by the way) - the pipes will start to eat: Fe + 2NaOH + 2H 2 O \u003d Na 2 + H 2 , Fe + H 2 CO 3 \u003d FeCO 3 + H 2.

This is the first of the possible causes of suffocating "gas", a physical and chemical process: saturation of air with a solution of concentrated sodium hydroxide in carbonic acid (boiling bubbles of oxygen and hydrogen as carriers). In the books of the 19th century, carbonic acid is used as a poisonous substance (in large quantities). That is why drivers installing a battery in a car get damaged by sulfuric acid (in fact, the same electrolysis): in the process of overcurrent to a highly discharged battery (the car has no current limit), the electrolyte boils for a short time, sulfuric acid comes out together with oxygen and hydrogen in the cabin. If the room is made completely airtight, due to the oxygen-hydrogen mixture (explosive gas), you can get a good blow with the destruction of the room. The video shows broads in miniature: under the action of molten copper, water decomposes into hydrogen and oxygen, and metal is more than 1100 degrees (I can imagine how the room completely filled with it stinks) ... About the symptoms of NaOH inhalation: caustic, burning sensation, sore throat, cough, shortness of breath, shortness of breath ; symptoms may be delayed. Feels like it fits perfectly.
...at the same time, Vladimir Vernadsky writes that life on Earth without carbonic acid dissolved in water is impossible.

We replace the cathode with a rusty piece of iron. A whole series of funny chemical reactions begins (and here it is, borscht!):
- rust Fe (OH) 3 and Fe (OH) 2, as bases, begin to react with carbonic acid (released at the cathode), obtaining siderite (red-brown): 2Fe (OH) 3 + 3H 2 CO 3 \u003d 6H 2 O + Fe 2 (CO3) 3, Fe (OH) 2 + H 2 CO 3 \u003d FeCO 3 + 2 (H 2 O). Iron oxides do not participate in the reaction with carbonic acid, because. there is no strong heating, and the acid is weak. Also, electrolysis does not restore iron at the cathode, because. these bases are not a solution, but the anode is not iron;
- caustic soda, as a base, does not react with bases. Necessary conditions for Fe(OH) 2 (amphoteric hydroxide): NaOH>50% + boiling in nitrogen atmosphere (Fe(OH) 2 + 2NaOH = Na2). Necessary conditions for Fe (OH) 3 (amphoteric hydroxide): fusion (Fe (OH) 3 + NaOH \u003d NaFeO 2 + 2H 2 O). Necessary conditions for FeO: 400-500 degrees (FeO + 4NaOH \u003d 2H 2 O + Na 4 FeO 3). Or maybe there is a reaction with FeO? FeO + 4NaOH = Na 4 FeO 3 + 2H 2 O - but only at a temperature of 400-500 degrees. Okay, maybe the sodium hydroxide removes some of the iron - and the rust just falls off? But here is a bummer: Fe + 2NaOH + 2H 2 O \u003d Na 2 + H 2 - but when boiling in a nitrogen atmosphere. What the hell is a solution of caustic soda without electrolysis removes rust? But he does not remove it in any way (I poured out exactly a transparent solution of caustic soda from "Auchan"). It removes grease, and in my case, with a piece of matiz, it dissolved the paint and primer (the resistance of the primer to NaOH is in its performance characteristics) - which exposed a clean iron surface, the rust simply disappeared. Conclusion: soda ash is needed only to obtain acid by electrolysis, which cleans the metal, taking rust on itself at an accelerated pace; sodium hydroxide seems to be out of business (but will react with debris in the cathode, cleaning it).

About foreign substances after electrolysis:
- the solution changed its color, became "dirty": with reacted bases Fe(OH) 3 , Fe(OH) 2 ;
- black plaque on the gland. First thought: iron carbide Fe 3 C (triiron carbide, cementite), insoluble in acids and oxygen. But the conditions are not the same: to obtain it, you need to apply a temperature of 2000 degrees; and in chemical reactions there is no free carbon to attach to iron. The second thought: one of the iron hydrides (saturation of iron with hydrogen) - but this is also not true: the conditions for obtaining are not the same. And then it came up: iron oxide FeO, the basic oxide does not react with either acid or caustic soda; and also Fe 2 O 3 . And amphoteric hydroxides are layers above the basic oxides, protecting the metal from further penetration of oxygen (they do not dissolve in water, they prevent the access of water and air to FeO). You can put the cleaned parts in citric acid: Fe 2 O 3 + C 6 H 8 O 7 \u003d 2FeO + 6CO + 2H 2 O + 2H 2 (special attention to the release of carbon monoxide and the fact that acid and metal eat on contact) - and FeO is removed with a conventional brush. And if you heat the highest oxide in carbon monoxide and do not burn out, then it will restore iron: Fe 2 O 3 + 3CO \u003d 2Fe + 3CO 2;
- white flakes in solution: some salts that are insoluble during electrolysis either in water or in acid;
- other substances: iron is initially "dirty", water is not initially distilled, dissolution of the anode.

The second of the possible causes of suffocating "gas" is a physical and chemical process: iron, as a rule, is not pure - with galvanization, a primer and other third-party substances; and water - with minerals, sulfates, etc. Their reaction during electrolysis is unpredictable, anything can be released into the air. However, my piece was so small (0.5x100x5) and the tap water (weakly mineralized) is unlikely to be the cause. Also, the idea of ​​the presence of foreign substances in the soda ash itself has disappeared: only it is indicated on the packaging in the composition.

The third possible cause of asphyxiating gas is a chemical process. If the cathode is restored, then the anode is bound to be destroyed by oxidation, if not inert. Stainless steel contains about 18% chromium. And this chromium, when destroyed, enters the air in the form of hexavalent chromium or its oxide (CrO 3 , chromic anhydride, reddish - further we will talk about it), a strong poison and a carcinogen with a delayed catalysis of lung cancer. The lethal dose is 0.08g/kg. Ignites gasoline at room temperature. Released when welding stainless steel. The horror is that it has the same symptoms as sodium hydroxide when inhaled; and sodium hydroxide already seems like a harmless animal. Judging by the description of cases of at least bronchial asthma, you need to work as a roofer for 9 years, breathing this poison; however, a clear delayed effect is described - that is, it can shoot both 5 and 15 years after a single poisoning.

How to check if chrome stood out from stainless steel (where - the question remains). The bolt after the reaction became more shiny than the same bolt from the same batch - a bad sign. As it turned out, stainless steel is such as long as chromium oxide exists in the form of a protective coating. If chromium oxide was destroyed by oxidation during electrolysis, then such a bolt will rust more intensively (free iron will react, and then chromium in the composition of untouched stainless steel will oxidize to CrO). Therefore, he created all the conditions for the rusting of two bolts: salt water and a solution temperature of 60-80 degrees. Stainless steel grade A2 12X18H9 (X18H9): it contains 17-19% chromium (and in stainless iron-nickel alloys, chromium is even higher, up to ~ 35%). One of the bolts turned red in several places, all places - in the contact zone of the stainless steel with the solution! The reddest one is along the line of contact with the solution.

And my happiness was that the current strength was then only 0.15A during electrolysis, the kitchen was closed and the window in it was open. It was clearly imprinted in my mind: to exclude stainless steel from electrolysis or to do it in an open area and at a distance (there is no stainless steel without chromium, this is its alloying element). Because stainless steel is NOT an inert anode during electrolysis: it dissolves and releases poisonous chromium oxide; sofa chemists, kill yourself against the wall until someone dies from your advice! The question remains, in what form, how much and where; but taking into account the release of pure oxygen at the anode, CrO is already precisely oxidized to the intermediate oxide Cr 3 O 2 (also poisonous, MPC 0.01 mg / m 3), and then to the higher oxide CrO 3: 2Cr 2 O 3 + 3O 2 \u003d 4CrO3. The latter remains an assumption (the necessary alkaline environment is present, but whether strong heating is needed for this reaction), but it is better to play it safe. Even blood and urine tests for chromium are difficult to do (they are not in the price lists, not even in the extended general blood test).

Inert electrode - graphite. It is necessary to go to the trolleybus depot, take pictures of the discarded brushes. Because even on aliexpress for 250 rubles per pin. And this is the cheapest of the inert electrodes.

And here is 1 more real example when a sofa electronics led to material losses. And to the right knowledge, really. As in this article. The benefits of sofa idle talk? - hardly, they sow chaos; and have to clean up after them.

I tend to the first reason for the suffocating "gas": the evaporation of a solution of sodium hydroxide in carbonic acid into the air. Because with chromium oxides, it is hose masks with mechanical air supply that are used - I would have suffocated in my miserable RPG-67, but it was noticeably easier to breathe in it at the very epicenter.
How to check for chromium oxide in the air? Start the process of water decomposition in a pure solution of soda ash on a graphite anode (pick out from a pencil, but not every pencil contains a pure graphite rod) and an iron cathode. And take a chance to inhale the air in the kitchen again after 2.5 hours. Is it logical? Almost: the symptoms of caustic soda and hexavalent chromium oxide are identical - the presence of caustic soda in the air will not prove the absence of hexavalent chromium vapor. However, the absence of odor without stainless steel will clearly give the result of the presence of hexavalent chromium. I checked, there was a smell - a phrase with hope "hooray! I breathed caustic soda, not hexavalent chromium!" can be broken into jokes.

What else was forgotten:
- how do acid and alkali exist together in one vessel? In theory, salt and water should appear. There is a very subtle point here, which can only be understood experimentally (did not check). If all the water is decomposed during electrolysis and the solution is isolated from salts in the precipitate - option 2: either a solution of caustic soda or caustic soda with carbonic acid will remain. If the latter is in the composition, the release of salt under normal conditions and the precipitation of ... soda ash will begin: 2NaOH + H 2 CO 3 \u003d Na 2 CO 3 + 2H 2 O. The problem is that it will dissolve in water right there - sorry, the taste cannot be tasted and compared with the original solution: suddenly the caustic soda has not completely reacted;
- Does carbonic acid interact with iron itself? The question is serious, because. the formation of carbonic acid occurs precisely at the cathode. You can check by creating a more concentrated solution and doing electrolysis until a thin piece of metal is completely dissolved (did not check). Electrolysis is seen as a more gentle rust removal method than acid pickling;
What are the symptoms of inhaling explosive gas? No + no smell, no color;
- Do caustic soda and carbonic acid react with plastic? Make identical electrolysis in plastic and glass containers and compare the turbidity of the solution and the transparency of the surface of the container (did not check on glass). Plastic - became less transparent in places of contact with the solution. However, these turned out to be salts, easily scraped off with a finger. So, food plastic does not react with the solution. Glass is used to store concentrated alkalis and acids.

If you inhale a lot of burning gas, regardless of whether it is NaOH or CrO 3, you need to take "unithiol" or a similar drug. And the general rule applies: no matter what poisoning occurs, no matter what strength and origin it may be, drink plenty of water in the next 1-2 days, if the kidneys allow. Task: remove the toxin from the body, and if this is not done by vomiting or expectoration, give additional opportunities to do this to the liver and urinary system.

The most annoying thing is that this is all the 9th grade school curriculum. Damn, I'm 31 years old - and I won't pass the exam ...

Electrolysis is interesting in that it turns back time:
- a solution of NaOH and H 2 CO 3 under normal conditions will lead to the formation of soda ash, while electrolysis inverts this reaction;
- iron in natural conditions is oxidized, and is restored during electrolysis;
- hydrogen and oxygen tend to combine in any way: mix with air, burn and become water, absorb or react with something; electrolysis, on the contrary, generates gases of various substances in their pure form.
The local time machine, nothing else: returns the position of the molecules of substances to their original state.

According to the reaction formulas, a solution of powdered sodium hydroxide is more dangerous when it is created and electrolyzed, but more effective in certain situations:
- for inert electrodes: NaOH + 2H 2 O = NaOH + 2H 2 + O 2 (the solution is a source of pure hydrogen and oxygen without impurities);
- reacts more intensively with organic materials, there is no carbonic acid (fast and cheap degreaser);
- if iron is taken as an anode, it will begin to dissolve at the anode and be reduced at the cathode, thickening the iron layer on the cathode in the absence of carbonic acid. This is a method of restoring the cathode material or coating it with another metal when there is no solution with the desired metal at hand. Rust removal, according to experimenters, also goes faster if iron is made the anode in the case of soda ash;
- but the concentration of NaOH in the air during evaporation will be higher (you still need to decide which is more dangerous: carbonic acid with caustic soda or moisture with caustic soda).

Earlier I wrote about education that a lot of time is wasted in school and university. This article does not change this opinion, because an ordinary person will not need matan, organic chemistry or quantum physics in life (only at work, and when I needed matan 10 years later, I learned it again, I didn’t remember anything at all). But inorganic chemistry, electrical engineering, physical laws, Russian and foreign languages ​​- this is what should be a priority (still introduce the psychology of the interaction of the sexes and the foundations of scientific atheism). Here, I did not study at the Faculty of Electronics; and then bam, locked up - and Visio learned to use, and MultiSim and some of the designations of the elements learned, etc. Even if I studied at the Faculty of Psychology, the result would be the same: I got stuck in life - bit into it - figured it out. But if at school the emphasis on natural sciences and languages ​​\u200b\u200bis been strengthened (and they explained to young people why it was strengthened), life would be easier. Both at school and at the institute in chemistry: they talked about electrolysis (theory without practice), but about the toxicity of vapors - no.

Finally, an example of obtaining pure gases (using inert electrodes): 2LiCl + 2H 2 O = H 2 + Cl 2 + 2LiOH. That is, first we poison ourselves with the purest chlorine, and then we explode with hydrogen (again, to the issue of the safety of the emitted substances). If there was a CuSO 4 solution, and the iron-metal cathode would drop out of the base and leave an oxygen-containing acid residue SO4 2-, it does not participate in the reactions. If the acid residue did not contain oxygen, it would decompose into simple substances (which is seen in the example of C 1 - , which is released as Cl 2).

(added 05/24/2016) If you need to boil NaOH with rust for their mutual reaction - why not? Nitrogen in the air is 80%. The effectiveness of rust removal will increase significantly, but then this process must definitely be done outdoors.

About metal hydrogenation (increase in brittleness): I did not find any formulas and adequate opinions on this topic. If possible, I will set up the electrolysis of the metal for several days, adding a reagent, and then I will knock with a hammer.

(added 05/27/2016) Graphite can be removed from a used salt battery. If it stubbornly resists disassembly, deform it in a vice.

(added 06/10/2016) Metal hydrogenation: H + + e - = H ads. H ads + H ads \u003d H 2, where ADS is adsorption. If a metal can, under the necessary conditions, dissolve hydrogen in itself (what a number!) - then it dissolves it in itself. The conditions for the occurrence of iron have not been found, but for steel they are described in the book of Schrader A.V. "Influence of Hydrogen on Chemical and Petroleum Equipment". In Figure 58, page 108, there is a graph of the brand 12X18H10T: at a pressure comparable to atmospheric pressure and a temperature of 300-900 degrees: 30-68 cm 3 / kg. Figure 59 shows dependencies for other steel grades. The general formula for hydrogenation of steel is: K s = K 0 e -∆H/2RT, where K 0 is the pre-exponential factor 1011l/mol s, ∆H is the heat of dissolution of steel ~1793K), R is the universal gas constant 8.3144598J/(mol ·K), T - medium temperature. As a result, at room temperature 300K we have K s = 843 l/mol. The number is not correct, you need to double-check the parameters.

(added 06/12/2016) If caustic soda does not interact with metals without high temperature, it is a safe (for metal) degreaser for pallets, pans and other things (iron, copper, stainless steel - but not aluminum, teflon, titanium, zinc).

With hydrogenation - clarifications. The pre-exponential factor K 0 lies in the range 2.75-1011l/mol·s, this is not a constant value. Calculating it for stainless steel: 10 13 C m 2/3, where C m is the atomic density of steel. The atomic density of stainless steel is 8 10 22 at / cm 3 - K 0 \u003d 37132710668902231139280610806.786 at. / cm 3 \u003d - and then everything is stuck.

If you look closely at the Schrader graphs, you can make an approximate conclusion about the hydrogenation of steel in OH (reducing the temperature by 2 times slows down the process by 1.5 times): approximately 5.93 cm 3 / kg at 18.75 degrees Celsius - but the time of penetration into the metal of such a volume is not indicated. In the book by Sukhotin A.M., Zotikov V.S. "Chemical resistance of materials. Handbook" on page 95 in table 8 shows the effect of hydrogen on the long-term strength of steels. It makes it possible to understand that the hydrogenation of steels with hydrogen at a pressure of 150-460 atmospheres changes the ultimate strength by a maximum of 1.5 times in the interval of 1000-10000 hours. Therefore, it is not necessary to consider the hydrogenation of steels during electrolysis in well as a destructive factor.

(added 06/17/2016) A good way to disassemble the battery: do not flatten the case, but open it like a tulip bud. From the positive input, piece by piece, bend down the parts of the cylinder - the positive input is removed, the graphite rod is exposed - and smoothly unscrewed with pliers.

(added 06/22/2016) The simplest batteries for disassembly are Ashanov's. And then in some models there are 8 circles of plastic to fix the graphite rod - it becomes difficult to pull it out, it starts to crumble.

(added 07/05/2016) Surprise: a graphite rod is destroyed much faster than an anode made of metal: in just a few hours. Using stainless steel as an anode is the best solution, if we forget about toxicity. The conclusion from this whole story is simple: electrolysis should be carried out only in the open air. If there is an open balcony in this role, do not open the windows, but pass the wires through the rubber door seal (just press the wires with the door). Taking into account the current during electrolysis up to 8A (Internet opinion) and up to 1.5A (my experience), as well as the maximum voltage of the PC PSU 24V, the wire must be rated for 24V / 11A - this is any wire in insulation with a cross section of 0.5mm 2.

Now about iron oxide on an already machined part. There are parts that are difficult to crawl into to erase black plaque (or an object under restoration, when you can’t rub the surface with an iron brush). When analyzing chemical processes, I came across a method for removing it with citric acid and tried it. Indeed, it also works with FeO - the plaque disappeared / crumbled for 4 hours at room temperature, and the solution turned green. But this method is considered less sparing, because. acid and metal eats up (cannot be overexposed, constant monitoring). Plus, a final rinse with a soda solution is required: either the acid residue will eat up the metal in air, and an undesirable coating will be obtained (an awl on soap). And you need to be careful: if as much as 6CO is released with Fe 2 O 3, then what is released with FeO is difficult to predict (organic acid). It is assumed that FeO + C 6 H 8 O 7 \u003d H 2 O + FeC 6 H 6 O 7 (formation of iron citrate) - but I also release gas (3Fe + 2C 6 H 8 O 7 → Fe 3 (C 6 H 5 O 7) 2 + 3H 2). They also write that citric acid decomposes in light and temperature - I can’t find the correct reaction in any way.

(added 07/06/2016) I tried citric acid on a thick layer of rust on nails - it dissolved in 29 hours. As expected: citric acid is suitable for the purification of metal. To clean thick rust: apply a high concentration of citric acid, high temperature (up to boiling), frequent stirring - to speed up the process, which is inconvenient.

A solution of soda ash after electrolysis, in practice, is difficult to regenerate. It is not clear: add water or add soda. The addition of table salt as a catalyst killed the solution completely + the graphite anode collapsed in just an hour.

Total: coarse rust is removed by electrolysis, FeO is pickled with citric acid, the part is washed with soda solution - and almost pure iron is obtained. Gas during reaction with citric acid - CO 2 (decarboxylation of citric acid), a darkish coating on iron - iron citrate (cleans easily-medium, does not perform any protective functions, soluble in warm water).

In theory, these methods of removing oxides are ideal for recovering coins. Unless weaker proportions of reagents are needed for a lower solution concentration and lower currents.

(added 07/09/2016) Conducted experiments with graphite. It is during the electrolysis of soda ash that it collapses extremely quickly. Graphite is carbon, when dissolved at the moment of electrolysis, it can react with steel and precipitate iron carbide Fe 3 C. The condition of 2000 degrees is not met, however, electrolysis is not NU.

(added 07/10/2016) When electrolyzing soda ash using graphite rods, the voltage cannot be increased above 12V. A lower value may be needed - keep an eye on the graphite breakdown time at your voltage.

(added 07/17/2016) Discovered the local rust removal method.

(added 07/25/2016) Instead of citric acid, you can use oxalic acid.

(added 07/29/2016) Steel grades A2, A4 and others are written in English letters: imported and from the word "austenitic".

(added 10/11/2016) It turns out that there is another type of rust: iron metahydroxide FeO(OH). It is formed when iron is buried in the ground; in the Caucasus, this method of rusting strip iron was used to saturate it with carbon. After 10-15 years, the resulting high-carbon steel became sabers.

Solving chemical problems
aware of Faraday's law
high school

Author's development

Among the great variety of various chemical problems, as the practice of teaching at school shows, the greatest difficulties are caused by problems for the solution of which, in addition to solid chemical knowledge, it is required to have a good command of the material of the physics course. And although far from every secondary school pays attention to solving at least the simplest problems using the knowledge of two courses - chemistry and physics, problems of this type are sometimes found at entrance exams in universities where chemistry is a major discipline. And therefore, without analyzing problems of this type in the classroom, a teacher can unintentionally deprive his student of the chance to enter a university in a chemical specialty.
This author's development contains over twenty tasks, one way or another related to the topic "Electrolysis". To solve problems of this type, it is necessary not only to have a good knowledge of the topic "Electrolysis" of the school chemistry course, but also to know Faraday's law, which is studied in the school physics course.
Perhaps this selection of tasks will not be of interest to absolutely all students in the class or is available to everyone. Nevertheless, tasks of this type are recommended to be analyzed with a group of interested students in a circle or optional class. It can be noted with confidence that problems of this type are complicated and at least not typical for a school chemistry course (we are talking about a secondary school), and therefore problems of this type can be safely included in the options for a school or district chemistry Olympiad for 10th or 11th grade.
Having a detailed solution for each problem makes development a valuable tool, especially for beginning teachers. Having analyzed several tasks with students in an optional lesson or a circle lesson, a creatively working teacher will certainly set several tasks of the same type at home and use this development in the process of checking homework, which will significantly save valuable teacher time.

Theoretical information on the problem

Chemical reactions occurring under the influence of an electric current on electrodes placed in an electrolyte solution or melt are called electrolysis. Consider an example.

In a glass at a temperature of about 700 ° C there is a melt of sodium chloride NaCl, electrodes are immersed in it. Before passing an electric current through the melt, Na + and Cl - ions move randomly, however, when an electric current is applied, the movement of these particles becomes ordered: Na + ions rush to the negatively charged electrode, and Cl - ions - to the positively charged electrode.

And he A charged atom or group of atoms that has a charge.

Cation is a positively charged ion.

Anion is a negatively charged ion.

Cathode- a negatively charged electrode (positively charged ions - cations) move towards it.

Anode- a positively charged electrode (negatively charged ions - anions) move towards it.

Electrolysis of sodium chloride melt on platinum electrodes

Total reaction:

Electrolysis of an aqueous solution of sodium chloride on carbon electrodes

Total reaction:

or in molecular form:

Electrolysis of an aqueous solution of copper(II) chloride on carbon electrodes

Total reaction:

In the electrochemical series of activity of metals, copper is located to the right of hydrogen, therefore copper will be reduced at the cathode, and chlorine will be oxidized at the anode.

Electrolysis of an aqueous solution of sodium sulfate on platinum electrodes

Total reaction:

Similarly, the electrolysis of an aqueous solution of potassium nitrate occurs (platinum electrodes).

Electrolysis of an aqueous solution of zinc sulfate on graphite electrodes

Total reaction:

Electrolysis of an aqueous solution of iron(III) nitrate on platinum electrodes

Total reaction:

Electrolysis of an aqueous solution of silver nitrate on platinum electrodes

Total reaction:

Electrolysis of an aqueous solution of aluminum sulfate on platinum electrodes

Total reaction:

Electrolysis of an aqueous solution of copper sulfate on copper electrodes - electrochemical refining

The concentration of CuSO 4 in the solution remains constant, the process is reduced to the transfer of the anode material to the cathode. This is the essence of the process of electrochemical refining (obtaining pure metal).

When drawing up schemes for the electrolysis of a particular salt, it must be remembered that:

– metal cations having a higher standard electrode potential (SEP) than that of hydrogen (from copper to gold inclusive) are almost completely reduced at the cathode during electrolysis;

– metal cations with small SEP values ​​(from lithium to aluminum inclusive) are not reduced at the cathode, but instead water molecules are reduced to hydrogen;

– metal cations, whose SEC values ​​are less than those of hydrogen, but greater than those of aluminum (from aluminum to hydrogen), are reduced simultaneously with water during electrolysis at the cathode;

- if the aqueous solution contains a mixture of cations of various metals, for example, Ag +, Cu 2+, Fe 2+, then silver will be the first to be reduced in this mixture, then copper, and the last iron;

- on an insoluble anode during electrolysis, anions or water molecules are oxidized, and anions S 2–, I –, Br – , Cl – are easily oxidized;

– if the solution contains anions of oxygen-containing acids , , , , then water molecules are oxidized to oxygen at the anode;

- if the anode is soluble, then during electrolysis it itself undergoes oxidation, i.e. it sends electrons to the external circuit: when electrons are released, the balance between the electrode and the solution is shifted and the anode dissolves.

If from the whole series of electrode processes we single out only those that correspond to the general equation

M z+ + ze=M,

then we get metal stress range. Hydrogen is also always placed in this row, which makes it possible to see which metals are able to displace hydrogen from aqueous solutions of acids, and which are not (table).

table

A range of stress metals

The equation electrode process	Standard electrode potential at 25 °С, V	The equation electrode process	Standard electrode potential at 25 °C, V
Li + + 1 e= Li0	–3,045	Co2+ + 2 e= Co0	–0,277
Rb + + 1 e= Rb0	–2,925	Ni 2+ + 2 e= Ni0	–0,250
K++1 e= K0	–2,925	Sn 2+ + 2 e= Sn0	–0,136
Cs + + 1 e= Cs 0	–2,923	Pb 2+ + 2 e= Pb 0	–0,126
Ca 2+ + 2 e= Ca0	–2,866	Fe 3+ + 3 e= Fe0	–0,036
Na + + 1 e= Na 0	–2,714	2H++2 e=H2	0
Mg 2+ + 2 e=Mg0	–2,363	Bi 3+ + 3 e= Bi0	0,215
Al 3+ + 3 e=Al0	–1,662	Cu 2+ + 2 e= Cu 0	0,337
Ti 2+ + 2 e= Ti0	–1,628	Cu + +1 e= Cu 0	0,521
Mn 2+ + 2 e=Mn0	–1,180	Hg 2 2+ + 2 e= 2Hg0	0,788
Cr 2+ + 2 e=Cr0	–0,913	Ag + + 1 e= Ag0	0,799
Zn 2+ + 2 e= Zn0	–0,763	Hg 2+ + 2 e= Hg0	0,854
Cr 3+ + 3 e=Cr0	–0,744	Pt 2+ + 2 e= Pt0	1,2
Fe 2+ + 2 e= Fe0	–0,440	Au 3+ + 3 e= Au 0	1,498
CD 2+ + 2 e= CD 0	–0,403	Au++1 e= Au 0	1,691

In a simpler form, a series of metal stresses can be represented as follows:

To solve most electrolysis problems, knowledge of Faraday's law is required, the formula expression of which is given below:

m = M I t/(z F),

where m is the mass of the substance released on the electrode, F- Faraday number, equal to 96 485 A s / mol, or 26.8 A h / mol, M is the molar mass of the element that is reduced during electrolysis, t– the time of the electrolysis process (in seconds), I- current strength (in amperes), z is the number of electrons involved in the process.

Task Conditions

1. What mass of nickel will be released during the electrolysis of a nickel nitrate solution for 1 hour at a current of 20 A?

2. At what current strength is it necessary to carry out the process of electrolysis of a solution of silver nitrate in order to obtain 0.005 kg of pure metal within 10 hours?

3. What mass of copper will be released during the electrolysis of a copper (II) chloride melt for 2 hours at a current of 50 A?

4. How long does it take to electrolyze an aqueous solution of zinc sulfate at a current of 120 A in order to obtain 3.5 g of zinc?

5. What mass of iron will be released during the electrolysis of an iron(III) sulfate solution at a current of 200 A for 2 hours?

6. At what current strength is it necessary to carry out the process of electrolysis of a solution of copper (II) nitrate in order to obtain 200 g of pure metal within 15 hours?

7. During what time is it necessary to carry out the process of electrolysis of a melt of iron (II) chloride at a current of 30 A in order to obtain 20 g of pure iron?

8. At what current strength is it necessary to carry out the process of electrolysis of a solution of mercury (II) nitrate in order to obtain 0.5 kg of pure metal within 1.5 hours?

9. At what current strength is it necessary to carry out the process of electrolysis of a sodium chloride melt in order to obtain 100 g of pure metal within 1.5 hours?

10. The potassium chloride melt was subjected to electrolysis for 2 hours at a current of 5 A. The resulting metal reacted with water weighing 2 kg. What concentration of alkali solution was obtained in this case?

11. How many grams of a 30% hydrochloric acid solution will be required for complete interaction with iron obtained by electrolysis of a solution of iron (III) sulfate for 0.5 h at current strength
10 A?

12. In the process of electrolysis of a melt of aluminum chloride, carried out for 245 min at a current of 15 A, pure aluminum was obtained. How many grams of iron can be obtained by the aluminothermic method when a given mass of aluminum interacts with iron(III) oxide?

13. How many milliliters of a 12% solution of KOH with a density of 1.111 g / ml will be required to react with aluminum (with the formation of potassium tetrahydroxyaluminate) obtained by electrolysis of an aluminum sulfate solution for 300 minutes at a current of 25 A?

14. How many milliliters of a 20% sulfuric acid solution with a density of 1.139 g / ml will be required to interact with zinc obtained by electrolysis of a zinc sulfate solution for 100 minutes at a current of 55 A?

15. What volume of nitric oxide (IV) (n.o.) will be obtained when an excess of hot concentrated nitric acid reacts with chromium obtained by electrolysis of a solution of chromium (III) sulfate for 100 minutes at a current of 75 A?

16. What volume of nitric oxide (II) (n.o.) will be obtained by reacting an excess of nitric acid solution with copper obtained by electrolysis of a copper(II) chloride melt for 50 minutes at a current of 10.5 A?

17. During what time is it necessary to carry out the electrolysis of a melt of iron (II) chloride at a current of 30 A in order to obtain the iron necessary for complete interaction with 100 g of a 30% hydrochloric acid solution?

18. How long does it take to electrolyze a nickel nitrate solution at a current of 15 A in order to obtain the nickel necessary for complete interaction with 200 g of a 35% sulfuric acid solution when heated?

19. The sodium chloride melt was electrolyzed at a current of 20 A for 30 minutes, and the potassium chloride melt was electrolyzed for 80 minutes at a current of 18 A. Both metals were dissolved in 1 kg of water. Find the concentration of alkalis in the resulting solution.

20. Magnesium obtained by electrolysis of a magnesium chloride melt for 200 min at current strength
10 A, dissolved in 1.5 l of a 25% sulfuric acid solution with a density of 1.178 g / ml. Find the concentration of magnesium sulfate in the resulting solution.

21. Zinc obtained by electrolysis of a solution of zinc sulfate for 100 min at current strength

17 A, was dissolved in 1 l of a 10% sulfuric acid solution with a density of 1.066 g/ml. Find the concentration of zinc sulfate in the resulting solution.

22. Iron obtained by electrolysis of a melt of iron(III) chloride for 70 min at a current of 11 A was powdered and immersed in 300 g of an 18% copper(II) sulfate solution. Find the mass of copper precipitated.

23. Magnesium obtained by electrolysis of a magnesium chloride melt for 90 minutes at current strength
17 A, were immersed in an excess of hydrochloric acid. Find the volume and amount of hydrogen released (n.o.s.).

24. A solution of aluminum sulfate was subjected to electrolysis for 1 hour at a current of 20 A. How many grams of a 15% hydrochloric acid solution would be required for complete interaction with the resulting aluminum?

25. How many liters of oxygen and air (N.O.) will be required for the complete combustion of magnesium obtained by electrolysis of a magnesium chloride melt for 35 minutes at a current of 22 A?

See the following numbers for answers and solutions

Making iron (read: cast iron and steel) by electrolysis rather than conventional smelting could prevent a billion tons of carbon dioxide from being released into the atmosphere each year. So says Donald Sadoway of the Massachusetts Institute of Technology (MIT), who has developed and tested a "green" way to produce iron by electrolysis of its oxides.

If the process, demonstrated in a laboratory setting, could be scaled up, it could eliminate the need for conventional smelting, which releases almost a ton of carbon dioxide into the atmosphere for every ton of steel produced.

In conventional technology, iron ore is combined with coke. The coke reacts with the iron, producing CO2 and carbon monoxide, and leaving an iron-carbon alloy, cast iron, which can then be smelted into steel.

In the Sadoway method, iron ore is mixed with a solvent - silicon dioxide and quicklime - at a temperature of 1600 degrees Celsius - and an electric current is passed through this mixture.

The negatively charged oxygen ions migrate to the positively charged anode, from where the oxygen escapes. The positively charged iron ions migrate to the negatively charged cathode, where they are reduced to iron, which collects at the base of the cell and is pumped out.

A similar process is used in the production of aluminum (and requires a decent amount of electricity), the oxide of which is so stable that it cannot actually be reduced with carbon in a blast furnace, in which, for example, pig iron is produced. And it is clear that the steel industry never had any reason to switch to the electrolysis of iron ore, since it is easily reduced by carbon.

But if governments around the world start imposing heavy taxes on greenhouse gas emissions — carbon dioxide in particular — then a new method of iron production could become more attractive. True, from laboratory installations of this kind to industrial installations, as scientists estimate, it will take 10-15 years.

The author of the work says that the biggest obstacle is to find a practical material for the anode. In experiments, he used an anode made of graphite. But, unfortunately, carbon reacts with oxygen, releasing just as much carbon dioxide into the air as normal iron smelting.

Ideal platinum anodes, for example, are too expensive for large scale production. But there may be a way out - in the selection of some resistant metal alloys that form an oxide film on their outer surface, but still conduct electricity. Conductive ceramics can also be used.

Another problem is that the new process uses a lot of electricity—about 2,000 kilowatt-hours per tonne of iron produced. So the economic and even ecological sense in a new method of iron production will appear only on the condition that this electricity will be generated in some ecological, and at the same time cheap, way, without carbon dioxide emissions. This is acknowledged by the author of the method himself.