Zinc oxide

Chemical properties

According to the pharmacopoeia, Zinc Oxide or zinc oxide is a colorless crystalline powder that is insoluble in water and ethyl alcohol. It dissolves well in diluted mineral acid and acetic acid. Under the influence of high temperature it turns yellow (due to the shift of the edge in the absorption spectrum to the blue region), sublimates at 1800 degrees Celsius. Molar mass = 81.4 grams per mole. Zinc Oxide Formula: ZnO. It has the property of absorbing carbon dioxide from the air.

What does the substance react with? According to its chemical properties, it is an amphoteric compound; it reacts with acids, forming salts, reacts with acidic and basic oxides, and forms complex compounds with alkali solutions. The oxide dissolves in ammonia solution in water, thereby forming a complex ammonia . The product reacts with metal oxides and alkali, forming zincates ; with silicon and boron oxide – silicates And borates . Zinc oxide does not react with copper, oxygen, or water. The chemical compound is obtained from the natural mineral zincite by burning vapors Zn in oxygen; during thermal decomposition hydroxide , carbonate And Zn nitrate ; using hydrothermal synthesis and oxidative roasting sulfide .

The product is widely used in the pharmaceutical and chemical industries; when creating toothpaste, cement in dentistry; the substance is added to cosmetics and tanning creams; used in the oil refining, tire and paint industries; used in the production of ceramics and glass, in electronics; added to animal feed; used to transform rust. The substance is slightly toxic. Inhalation of dust containing oxide may cause foundry fever .

pharmachologic effect

Antiseptic, drying, astringent, adsorbent.

Pharmacodynamics and pharmacokinetics

The substance has the ability, when applied to the surface of the skin and wound surface, to denature proteins and form albuminates . The product significantly reduces the severity of the exudation process, relieves inflammation and irritation. Forms a barrier film on the skin that protects it from adverse factors and has an absorbent effect.

The medicine is used in the form of powders, pastes and ointments, liniment.

Indications for use

Applications of zinc oxide:

• for prickly heat and diaper rash;
• for the treatment of superficial wounds and burns, cuts, abrasions, scratches;
• in the treatment of bedsores, trophic ulcers , streptoderma .

Contraindications

Zinc oxide cannot be used in the presence of the active ingredient.

Side effects

Itching, allergic skin rashes rarely occur, hyperemia .

Instructions for use (Method and dosage)

Zinc Oxide is used topically, externally. Depending on the dosage form and the disease, different treatment regimens are used.

Overdose

There is no information about overdose. Allergic reactions may develop.

Interaction

Zinc oxide is incompatible with ichthammol as part of an ointment.

special instructions

Preparations based on Zinc Oxide should be used in accordance with the recommendations of a doctor.

Do not allow the medicine to get into your eyes.

For children

The product can be used in the treatment of patients of all age categories.

Topic 28

Group IIB elements: zinc, cadmium, mercury

General characteristics.

The elements of this subgroup are complete electronic analogues of each other, each in its period is the last element of the d-family, they have a complete d-electron configuration, valence electrons (n-1)d 10 ns 2. The outer electron shell contains 2 electrons and 18 electrons in the previous shell. Zinc and its analogues differ from d-elements and are more similar to p-elements of longer periods.

In zinc, cadmium and mercury atoms, as well as in copper atoms, the (n-1)d sublevel is completely filled and completely stable. Removing electrons from it requires a very large expenditure of energy. Therefore, the elements in question exhibit a maximum oxidation state of +2 in their compounds. Only mercury forms compounds in which its oxidation state is +1.

A characteristic feature of the elements is their tendency to form complexes (number = 4; 6).

In contrast to the elements of the main subgroups, the elements of the zinc subgroup are more difficult to oxidize, exhibit less reactivity and exhibit weaker metallic properties.

In the subgroup from top to bottom: the atomic radius increases, the melting and boiling points decrease, electronegativity and electrode potential increase. The minimum ionization energy is observed for cadmium (8.99 eV), because The properties of mercury are affected by lanthanide compression, as a result of which its ionization energy increases to 10.43 eV (for zinc 9.39 eV).

Abundances and main minerals.

ZnS – zinc blende,

HgS – cinnabar,

ZnCO 3 – galmey,

CdS – greenockite.

Natural zinc compounds are part of polymetallic sulfide ores, which contain pyrite FeS 2, galena PbS, chalcopyrite CuFeS 2, and to a lesser extent ZnS. Mercury is a rare element and occurs in its native state.

Metal zinc, its preparation, properties and application.

A silvery-white soft metal that becomes covered with an oxide film when exposed to air. Has no polymorphic modifications, diamagnetic. The external electronic configuration of the Zn atom is 3d 10 4s 2. The oxidation state in compounds is +2. The normal redox potential of 0.76 V characterizes Zinc as an active metal and an energetic reducing agent.

To isolate zinc, the ZnS concentrate obtained after enrichment is roasted, and the resulting oxide is reduced with coal:

2ZnS + 3O 2 = 2ZnO + 2SO 2

ZnO + C = Zn + CO

Another method is to roast the ZnS containing ore and then treat it with dilute sulfuric acid:

ZnO + H 2 SO 4 = ZnSO 4 + H 2 O

The resulting solution of zinc sulfate is subjected to electrolysis.

In terms of chemical activity, the zinc subgroup is inferior to alkaline earth metals. In the subgroup, with increasing atomic mass, the chemical activity of metals decreases, as evidenced by the values ​​of standard electrode potentials (see above). Zinc is a chemically active metal, easily soluble in acids and, when heated, in alkalis:

Zn + 2HCl = ZnCl 2 + H 2 Zn + H 2 SO 4 (solution) = ZnSO 4 + H 2

These reactions occur slowly, because... the resulting atomic hydrogen covers the surface of the zinc.

Zn + 2H 2 SO 4 (conc.) = ZnSO 4 + SO 2 + H 2 O

4Zn + 10HNO 3 = 4Zn(NO 3) 2 + NH 4 NO 3 + 3H 2 O

Zn + 2NaOH + 2H 2 O = Na 2 + H 2

Metallic zinc displaces less active metals and reduces H2CrO4, HMnO4, iron (III) and tin (IV) salts:

5Zn + 2KMnO 4 + 8H 2 SO 4 (p - p) = 2MnSO 4 + 5ZnSO 4 + K 2 SO 4 + 8H 2 O

Zn + CuSO 4 = ZnSO 4 + Cu

The uses of zinc are varied. Zinc is used to make an alloy with aluminum, copper, and magnesium, which are of industrial importance. A significant portion of zinc is used to coat iron and steel products, which protect the base metal from corrosion.

Zinc oxide and hydroxide.

Zinc oxide- a loose white powder that turns yellow when heated, but becomes white again when cooled, a semiconductor. Zinc oxide is amphoteric - reacts with acids to form salts; when interacting with alkali solutions, it forms complex tritetra- and hexahydroxyzincates (Na 2, Ba 2):

ZnO + 2HCl = ZnCl 2 + H 2

ZnO + 2NaOH + 2H 2 O Na 2 + H 2

Zinc oxide dissolves in an aqueous ammonia solution, forming complex ammonia:

ZnO + 4NH 3 + H 2 O - (OH) 2

When fused with alkalis and metal oxides, zinc oxide forms zincates:

ZnO + 2NaOH Na 2 ZnO 2 + H 2 O

ZnO + CoO CoZnO 2

When fused with boron and silicon oxides, zinc oxide forms glassy borates and silicates:

ZnO + B 2 O 3 Zn(BO 2) 2

ZnO + SiO 2 ZnSiO 3

At temperatures above 1000°C it is reduced to metallic zinc by carbon, carbon monoxide and hydrogen:

ZnO + C = Zn + CO

ZnO + CO = Zn + CO 2

ZnO + H 2 = Zn + H 2 O

Does not react with water. When interacting with non-metal oxides, it forms salts, where it is a cation:

2ZnO + SiO 2 = Zn 2 SiO 4

ZnO + B 2 O 3 = Zn(BO 2) 2

It is obtained by burning zinc metal:

2Zn + O 2 = 2ZnO

during thermal decomposition of salts:

ZnCO 3 = ZnO + CO 2

Zinc oxide is used for the production of white oil paint (zinc white), in medicine and cosmetics (for the production of various ointments); A significant portion of zinc oxide is used as a rubber filler.

Zinc hydroxide– a colorless crystalline or amorphous substance. At temperatures above 125°C it decomposes:

Zn(OH) 2 = ZnO + H 2 O

Zinc hydroxide exhibits amphoteric properties and is easily soluble in acids and alkalis:

Zn(OH) 2 + H 2 SO 4 (conc) = ZnSO 4 + 2H 2 O

Zn(OH) 2 + 2NaOH = Na 2

also easily dissolves in an aqueous solution of ammonia to form tetraamminium zinc hydroxide:

Zn(OH) 2 + 4NH 3 = (OH) 2

It is obtained in the form of a white precipitate when zinc salts react with alkalis:

ZnCl 2 + 2NaOH = Zn(OH) 2 + 2NaCl

Zinc oxide has been used in medicine for centuries. Mentions of it are found in the ancient Indian medical text “Charaka Samhita”. Also, the use of zinc oxide for medical purposes is described by the Greek physician Dioscorides. Today this substance finds various uses in both pharmacology and industry.

Zinc oxide is an inorganic compound that is present in the earth's crust in the form of a mineral known as zincite. However, in order to meet most of the commercial demand for this compound, it is also synthesized artificially. Chemical formula of zinc oxide ZnO. It is a white, powdery substance that is insoluble in water and alcohol, but soluble in most acids, including hydrochloric acid (HCl).

Burning zinc in air to produce zinc oxide was a common practice among alchemists. The substance thus obtained looks very loose and resembles white tufts of wool, which is why it is called “philosophers’ wool.”

The mineral zincite may have a slightly yellowish or pinkish color due to the presence of manganese and other impurities. Zinc oxide is known to react strongly with aluminum and magnesium powder. Another interesting property of this inorganic compound is that it can absorb ultraviolet radiation. In addition, zinc oxide is known for its properties such as high thermal conductivity and the ability to have an antibacterial effect.

Application of zinc oxide in medicine

• Zinc oxide has antibacterial properties, and therefore is widely used in the treatment of a number of skin diseases. It is used externally to reduce skin irritation and treat minor burns and cuts. This substance can also be used as a remedy against dry and keratinized skin.

Zinc oxide is used in newborn care

Zinc oxide is the most widely used product for the treatment and prevention of diaper rash.
It essentially forms a protective barrier between the skin and the diaper,
thus preventing the appearance of any rashes.

• Due to its medicinal properties, it is added to baby powders, anti-dandruff shampoos, antiseptic creams and surgical tapes. Together with iron oxide, this compound is used to create sunburn liquid (calamine lotion).
• Zinc oxide is mixed with eugenol to obtain zinc oxide with eugenol, which is used in dentistry for prosthetics and tooth restoration.
• The ability to relieve itching and irritation of the skin makes zinc oxide an important ingredient in many rectal suppositories that are used to relieve irritation and discomfort from hemorrhoids.
• This substance also serves as a source of the mineral nutrient zinc, which is required for a wide range of reactions in the body. Therefore, it is added to food or vitamin supplements. As a dietary supplement, zinc oxide can also be found in vitamin- and mineral-fortified breakfast cereals. Due to the presence of fungistatic properties, it is used in the production of packaging material for meat, fish and vegetables.

Application of zinc oxide in cosmetology

• Zinc oxide is able to absorb ultraviolet radiation from the sun, and thus protect the skin from sunburn and other damage caused by UV rays.

• Zinc oxide is one of the most important ingredients in mineral cosmetics. Since the skin does not absorb it, it does not cause irritation to anyone. In addition, its use does not lead to acne and does not cause allergies.
• Among other things, zinc oxide is used in the production of deodorants and soaps. It helps eliminate unpleasant body odor and prevents the growth of bacteria. Zinc oxide also soothes the skin and protects it from irritants.

However, caution must be exercised when using zinc oxide or products containing it externally. It should not be used to treat severe burns or wounds. It is important to avoid getting zinc oxide in your eyes and mouth. Exposure to zinc oxide fumes can irritate the lungs and cause foundry fever, which has flu-like symptoms. Thus, inhaling zinc oxide vapor is dangerous, while zinc oxide itself is not toxic.

Structural formula

Russian name

Latin name for the substance Zinc oxide

Gross formula

Pharmacological group of the substance Zinc oxide

Nosological classification (ICD-10)

CAS code

Characteristics of the substance Zinc oxide

Anti-inflammatory agent for topical use. White or white with a yellowish tint, amorphous, odorless powder. Absorbs carbon dioxide from the air. Practically insoluble in water and ethanol, soluble in diluted mineral acids and acetic acid, in alkali solutions.

Pharmacology

Forms albuminates and denatures proteins. When applied to the affected surface of the skin, it reduces the severity of exudative processes, eliminates local manifestations of inflammation and irritation; has an adsorbing effect, forms a protective coating on the skin, which reduces the impact of irritating factors on it. Apply externally in the form of powder, ointment, paste, liniment.

Application of the substance Zinc oxide

Dermatitis, including diaper dermatitis (treatment and prevention), diaper rash, prickly heat; superficial wounds and burns (including sunburn, cuts, scratches), ulcerative skin lesions (including trophic ulcers), bedsores; eczema in the acute stage, herpes simplex, streptoderma.

Contraindications

Hypersensitivity.

Routes of administration

Externally.

Precautions for the substance Zinc oxide

Avoid contact with eyes.

Interactions with other active ingredients

Trade names

Zinc whitewash

Zinc oxide.

Chemical formula of the product: ZnO

Product trade names:

• Zinc white
• Zinc whitewash
• Zinc oxide
• Zinc flowers
• C.I. pigment white 4
• Oxozinc
• Zincite
• Lassar Paste

Product Description:

Zinc oxideis an inorganic compound with the formula ZnO. Zinc oxide is a white powder that is insoluble in water and is widely used as an additive in many materials and products, including rubbers, plastics, ceramics, glass, cement, lubricants, paints, ointments, adhesives, sealants, pigments, foods, batteries, ferrites , flame retardants and tape films. Although it occurs naturally as the mineral zincite, most zinc oxide obtained synthetically. Zinc whitewash is a wide-gap semiconductor of semiconductor group II-VI. Natural doping of a semiconductor due to oxygen vacancies or n-type zinc interstitial sites. This semiconductor has a number of favorable properties, including good transparency, high electron mobility, wide bandgap, and strong luminescence at room temperature. These properties are valuable in new applications for: transparent electrodes in liquid crystal displays, energy-saving or thermal windows, and electronics in the form of thin film transistors and light-emitting diodes. Zinc oxide(also called white zinc) is an amorphous white or yellowish powder, insoluble in water and alcohol, but soluble in acid And alkalis. Particles zinc oxide may be spherical, needle-shaped or spherical depending on the manufacturing process. Particle shape is important to maximize physical properties. Zinc oxide absorbs virtually all ultraviolet radiation at wavelengths below 360 nm and provides excellent protection for binders. Zinc oxide reacts with acidic components of coatings and forms zinc soaps. Zinc soaps improve the flexibility and hardness of coatings. It is used as a pigment in rubber formulation, as a white pigment in the ceramic industry, as an opaque base in cosmetics, and has other applications in the paper, paint and optical glass industries.

Zinc oxidecrystallizes in two main forms: hexagonal wurtzite and cubic galvanized blende. The wurtzite structure is the most stable under ambient conditions and therefore the most common. The shape of zinc blende can be stabilized by growing zinc oxide on substrates with a cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral, the most characteristic geometry for Zn(II). Zinc oxide transforms at relatively high pressures, about 10 GPa. Hexagonal and galvanized polymorphs do not have inversion symmetry (reflecting the crystal relative to any given point does not turn it into itself). This and other properties of lattice symmetry lead to the piezoelectricity of hexagonal and galvanized zinc white and the pyroelectricity of hexagonal zinc oxide. As with most group II-VI materials, the binding of atomic structures in zinc oxide is largely ionic (Zn 2 + -O 2 -) with corresponding radii of 0.074 nm for Zn 2+ and 0.140 nm for O 2 -. This property explains the preferential formation of the wurtzite structure rather than zinc blende, as well as strong piezoelectricity zinc oxide A. Due to polar Zn-O bonds, the zinc and oxygen planes are electrically charged. To maintain electrical neutrality, these planes are restored at the atomic level in most relative materials, but not in zinc oxide- its surfaces are atomically flat, stable and have no reconstruction. This anomaly zinc oxide not fully explained.

Zinc oxide- a relatively soft material with an approximate hardness of 4.5 on the Mohs scale. Its elastic constants are smaller than those of corresponding III-V semiconductors such as GaN. High heat capacity and thermal conductivity, low thermal expansion and high melting point zinc oxide beneficial for ceramics. Of tetrahedrally bonded semiconductors, it has been stated that zinc oxide has the highest piezoelectric tensor or at least comparable to GaN and AlN. This property makes it a technologically important material for many piezoelectric applications that require large electromechanical coupling. Zinc oxide has a relatively large direct band gap of ~3.3 eV at room temperature. Benefits associated with a larger range gap include higher breakdown voltages, the ability to withstand larger electric fields, lower electronic noise, and high-temperature, high-power operation. Gap zinc oxide can be further tuned to ~3-4 eV by doping it with magnesium oxide or cadmium oxide. Majority zinc oxide has an n-type character, even in the absence of deliberate doping. Nonstoichiometry is generally the source of n-type character, but the subject remains controversial. An alternative explanation has been proposed, based on theoretical calculations, that unintentional replacement hydrogen impurities are the cause. Controlled n-type doping is easily achieved by replacing Zn with Group III elements such as Al, Ga, In, or replacing oxygen with Group VII elements with chlorine or iodine.

In production zinc oxide There are three main methods.

1. Indirect method. In indirect or French process metal zinc melts in a graphite crucible and evaporates at temperatures above 907 °C (usually around 1000 °C). Couples zinc react with oxygen in the air, which leads to the formation of ZnO, accompanied by a drop in its temperature and bright luminescence. Particles zinc oxide transported to the cooling channel and collected in a bag. This indirect method was popularized by LeClaire (France) in 1844 and is therefore commonly known as the French process. Its product usually consists of agglomerated particles zinc oxide with an average size from 0.1 to several micrometers. By weight most zinc oxide in the world it is produced according to the French method.
2. Direct process. The direct or American process begins with a variety of contaminated zinc composites such as zinc ores or smelting furnace by-products. Precursors zinc reduced (carbothermic reduction) by heating with a carbon source such as anthracite to produce vapor zinc a, which is then oxidized, as in the case of the indirect process. Due to the lower purity of the starting material, the final product is also of lower quality in the direct process compared to the indirect process.
3. Wet chemical process . A small amount of industrial production involves wet chemical processes that begin with aqueous solutions of zinc salts from which precipitate zinc carbonate or zinc hydroxide. The solid precipitate is then calcined at temperatures around 800 °C.

There are numerous specialized methods for obtaining zinc oxide for scientific research and applications in niche areas. These methods can be classified by the resulting form of ZnO (bulk, thin film, nanowire), temperature ("low", near room temperature or "high", i.e. T ~ 1000 °C), type of process (vapor deposition or growth from solution) and other parameters. Large single crystals (many cubic centimeters) can be grown by gas transfer (vapor deposition), hydrothermal synthesis, or melt growth. However, due to the high vapor pressure zinc oxide growth from melt is problematic. It is difficult to control the growth of gas transport, leaving preference to the hydrothermal method. Thin films can be produced by chemical vapor deposition, metal vapor deposition, electrodeposition, pulsed laser deposition, sputtering, sol-gel synthesis, atomic layer deposition, sputter pyrolysis, etc. Regular white powder zinc oxide can be obtained in the laboratory by electrolysis of a solution of sodium bicarbonate with a zinc anode. Produced zinc hydroxide and hydrogen. Zinc hydroxide when heated, it decomposes to zinc oxide. Zinc oxide nanostructures can be synthesized into various morphologies, including nanowires, nanorods, tetrapods, nanoobjects, nanofibers, nanoparticles, etc. Nanostructures can be obtained using most of the above methods under certain conditions, as well as using the vapor-liquid-solid method. The synthesis is usually carried out at temperatures around 90 °C in an equimolar aqueous solution of nitrate zinc a and hexamine, the latter providing the basic environment. Some additives such as polyethylene glycol or polyethyleneimine can improve the nanofilament aspect ratio zinc oxide. Nanowire doping zinc oxide was achieved by adding other metal nitrates to the growth solution. The morphology of the resulting nanostructures can be tuned by changing parameters related to the composition of the precursors (such as zinc concentration and pH) or to the thermal treatment (such as temperature and heating rate).

Physico-chemical properties Zinc oxide.

Storage and transportation of zinc oxide:

Precautionary measures:

Keep closed. Do not swallow. Do not inhale dust. Wear appropriate protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If swallowed, seek immediate medical attention and show container or label. Keep away from incompatible substances such as acids.

Storage: Keep container tightly closed. Store container in a cool, well-ventilated area. Do not store above 25°C (77°F).

Application areas of zinc oxide:

1. Powder Applications zinc oxide are numerous, and the main ones are given below. Most applications take advantage of the oxide's reactivity as a precursor to other zinc compounds. For applications in materials science zinc oxide has a high refractive index, high thermal conductivity, binding, antibacterial and UV protective properties. Consequently, it is added to materials and products, including plastics, ceramics, glass, cement, rubber, lubricants, paints, ointments, adhesives, sealants, concrete production, pigments, foods, batteries, ferrites.
2. Rubber production. The rubber industry uses 50% to 60% zinc oxide. Zinc oxide used together with stearic acid for rubber vulcanization Additive zinc oxide also protects rubber from fungi and ultraviolet radiation.
3. Ceramic industry. The ceramics industry consumes a significant amount zinc oxide, in particular, in ceramic glazes and frit compositions.The relatively high heat capacity, thermal conductivity, and high temperature stability of zinc oxide, combined with a relatively low coefficient of expansion, are desirable properties in ceramic production.Zinc oxideaffects the melting point and optical properties of glazes, enamels and ceramic compositions.Zinc oxideAs a low expansion, secondary flow improves the elasticity of glazes, reducing temperature variation in viscosity and preventing cracking.
4. Medicine. Zinc oxide Widely used to treat various skin conditions including dermatitis, itching due to eczema, diaper rash and acne. It is used in products such as baby powder and diaper treatment barrier creams, calamine creams, anti-dandruff shampoos and antiseptic ointments . Zinc oxide can be used in ointments, creams and lotions to protect against sunburn and other skin damage caused by ultraviolet light. Many sunscreens use nanoparticles zinc oxide(along with nanoparticles titanium dioxide), because such small particles do not scatter light and therefore do not appear white. Nanoparticles zinc oxide may enhance the antibacterial activity of ciprofloxacin.
5. Tobacco industry. Zinc oxide is an integral part of cigarette filters. The filter, consisting of carbon impregnated with zinc oxide and iron oxide, removes significant amounts of hydrogen cyanide and hydrogen sulfide from tobacco smoke without affecting its aroma.
6. Food supplement. Zinc oxide added to many foods, including breakfast cereals, as a source of zinc, an essential nutrient. Zinc sulfate also used for the same purpose.
7. Production of pigments. Zinc oxide white is used as a pigment in paints and is more opaque than lithopone but less opaque than titanium dioxide It is also used in paper coatings. Chinese white is a special grade of zinc white that is used in artists' pigments. The use of white zinc (zinc oxide) as a pigment in oil painting began in the mid-18th century. It partially replaced poisonous white lead and was used by artists such as Böcklin, Van Gogh, Manet, Munch. It is also the main ingredient in mineral makeup.
8. Coatings. Paints containing powder zinc oxide, have long been used as anti-corrosion coatings for metals. They are especially effective on galvanized iron. Iron is difficult to protect because its reactivity with organic coatings results in brittleness and lack of adhesion. Based paints zinc oxide retain their flexibility and adhesion on such surfaces for many years. Plastics such as polyethylene naphthalate (PEN) can be protected by applying a zinc oxide coating. The coating reduces oxygen diffusion using PEN. Zinc oxide layers can also be used on polycarbonate (PC) in exterior applications. The coating protects the PC from solar radiation and reduces the rate of oxidation and photo-yellowing of the PC.
9. Preventing Corrosion in Nuclear Reactors . Zinc oxide, depleted in 64 Zn (an isotope of zinc with atomic mass 64), is used to prevent corrosion in pressurized water nuclear reactors. Depletion is necessary because 64 Zn is converted to radioactive 65 Zn when irradiated by reactor neutrons.
10. Methane reform . Zinc oxide used as a pretreatment step to remove hydrogen sulfide from natural gas after hydrogenating any sulfur compounds prior to the methane reformer, which can poison the catalyst.