Thermodynamic and electrophysical properties. Project site for the manufacture of sensitive elements of photoresistors based on cadmium sulfide output control of the parameters "Chips"

(CADMIUM) CD - chemical element 12 (IIb. ) Groups of the periodic system. Atomic number 48, the relative atomic mass of 112.41. Natural cadmium consists of eight stable isotopes: 106CD (1.22%), 108 CD (0.88%), 110 CD (12.39%), 111 CD (12.75%), 112 CD (24.07%), 113 CD (12,26 %), 114 CD (28.85%) and 116 CD (7.58%). The degree of oxidation is +2, rarely +1.

Cadmium was opened in 1817 by the German chemist Friedrich Stromeyer (

Stromeyer Friedrich. ) (1776-1835).

When checking the zinc oxide produced by one of the Schenebek factories, there was a suspicion that it contains a mysteria. When dissolving the drug in acid and passing through a solution of hydrogen sulfide, a yellow precipitate dropped, similar to arsenic sulfide, but a more thorough check showed that this element is not. For a final conclusion, a sample of suspicious zinc oxide and other zinc drugs (including zinc carbonate) from the same factory were sent by Friedrich Schtreterer, who occupied from 1802 Department of Chemistry in the University of Göttingen and the position of General Inspector of Hannover Pharmacies.

Purging zinc carbonate, the strokeer received oxide, but not white, as it should have been, but yellowish. He suggested that the painting is caused by an admixture of iron, but it turned out that there is no iron. The strokeer fully analyzed the zinc drugs and found that the yellow color appeared thanks to a new element. He was called in honor of the Zinc Ore, in which was found: Greek word

kadmeia. , "Cadmium Earth" - an ancient name of SmitstonitisZnco. 3. This word, according to legend, comes on behalf of the Phoenician Cadma, which would be the first to find a zinc stone and noticed his ability to give copper (when smelting it from ore) golden color. The hero of an ancient Greek mythology was also called: according to one of the legends, Cadm won in the heavy fight of the dragon and on his lands built a fortress for cadmium, around which the seven-radial city of the hair rose.The prevalence of cadmium in nature and its industrial extraction. Cadmium content in the earth's crust is 1.6 · 10 -5%. It is close to prevalence to antimony (2 · 10 -5%) and are twice again more than mercury (8 · 10 -6%). For cadmium, migration in hot underground waters together with zinc and other chemical elements, prone to the formation of natural sulfides. It concentrates in hydrothermal sediments. Volcanic rocks contain up to 0.2 mg of cadmium per kg, among sedimentary rocks are rich in cadmium of clay - up to 0.3 mg / kg, to a lesser degree - limestone and sandstones (about 0.03 mg / kg). The average cadmium content in the soil is 0.06 mg / kg.

Cadmium has its own minerals - Grekenit

CDS, Tatwit CDCO 3, CDO Monitis . However, they do not form their deposits. The only industrial cadmium source is ores of zinc, where it is contained at a concentration of 0.01-5%. Cadmium accumulates also in galena (up to 0.02%), chalcopyrite (up to 0.12%), pyrite (up to 0.02%), and apply (up to 0.2%). The total world cadmium resources are estimated at 20 million tons, industrial - 600 thousand tons.Characteristics of a simple substance and industrial production of metallic cadmium. Cadmium - a silver solid with a bluish gloss on fresh surface, soft, dust, driving metal, well rolled into sheets, easy to polish. Like tin sticks, cadmium chopping is published. Melts at 321.1 ° C, boils at 766.5 ° C, the density is 8.65 g / cm 3, which makes it possible to attribute it to heavy metals.

In the dry air, the cadmium is stable. In humid air, it will quickly dumps, and when heated it easily interacts with oxygen, gray, phosphorus and halogens. With hydrogen, nitrogen, carbon, silicon and boron, the cadmium does not react.

Cadmium pairs interact with water vapor with hydrogen release. Acids dissolve cadmium with the formation of salts of this metal. Cadmium restores ammonium nitrate in concentrated solutions to ammonium nitrite. It is oxidized in aqueous solution by cations of some metals, such as copper (

II) and iron (III ). With alkalis solutions, unlike zinc, the cadmium does not interact.

The main sources of cadmium are intermediate products of zinc production. Metal precipitation obtained after purification of zinc sulfate solutions by the action of zinc dust, contain 2-12% cadmium. In fractions generated during the distillation production of zinc, contains 0.7-1.1% cadmium, and in fractions obtained during the distillation cleaning of zinc - up to 40% of cadmium. Cadmium is removed from dust of lead and copper-smelting plants (it may contain up to 5% and 0.5% cadmium, respectively). Dust is usually treated with concentrated sulfuric acid, and then cadmium sulfate is leached with water.

Cadmium sponge is precipitated from cadmium sponge sulfate solutions with a cadmium sponge, then it is dissolved in sulfuric acid and the solution is purified from impurities with the action of zinc oxide or sodium carbonate, as well as ion exchange methods. Metal cadmium is isolated by electrolysis on aluminum cathodes or recovery zinc.

To remove zinc and lead, the metal cadmium is interpretable under the alkali layer. The melt is treated with aluminum to remove nickel, and ammonium chloride to get rid of Tallina. Applying additional cleaning methods, you can get cadmium with an impurity content of 10 -5% by weight.

About 20 thousand tons of Cadmium are produced per year. The volume of its production is largely associated with the scale of zinc production.

The most important area of \u200b\u200bcadmium application is the production of chemical current sources. Cadmium electrodes are used in batteries and batteries. Negative plates of nickel-cadmium batteries are made of iron grids with spongy cadmium as an active agent. Positive plates are covered with nickel hydroxide. The electrolyte is a solution of potassium hydroxide. Based on cadmium and nickel, compact batteries for managed missiles are also manufactured, only in this case are not iron, but nickel grids.

The processes occurring in the nickel-cadmium alkaline battery can be described by the total equation:

CD + 2NIO (OH) + 2H 2 O CD (OH) 2 + 2NI (OH) 2 Nickel-cadmium alkaline batteries are more reliable than lead (acid). These current sources are distinguished by high electrical characteristics, work stability, long service life. They can be charged in just one hour. However, nickel-cadmium batteries cannot be recharged without complete preliminary discharge (in this respect they are inferior to metalhydride batteries).

Cadmium is widely used to apply anticorrosive coatings on metals, especially in cases of their contact with sea water. The most important details of ships, aircraft, as well as various products designed to work in a tropical climate. Previously, iron and other metals have patched the immersion of products to the molten cadmium, now the cadmium coating is applied electrolytic.

Cadmium coatings have some benefits compared to zinc: they are more resistant to corrosion, they are easier to make them smooth and smooth. The high plasticity of such coatings ensures the tightness of the threaded connections. In addition, cadmium, in contrast to zinc, is stable in an alkaline environment.

However, the cadming has its own problems. With electrolytic application of cadmium on the steel part in the metal, hydrogen contained in the electrolyte can be penetrated. It causes the so-called hydrogen fragility in high-strength steels leading to unexpected metal destruction under load. To prevent this phenomenon in cadmium coatings, the additive of titanium is introduced.

In addition, cadmium toxic. Therefore, although the caddmitted tin is used quite widely, for the manufacture of kitchen utensils and containers for food products to use it is prohibited.

Approximately tenth of the global cadmium production is spent on the production of alloys. Cadmium alloys are mainly used as antifriction materials and solders. The alloy containing 99% cadmium and 1% nickel is used for the manufacture of bearings operating in automotive, aviation and ship engines in high temperatures. Since cadmium is not sufficiently racks to the action of acids, including organic acids contained in lubricants, sometimes cadmium-based bearing alloys are covered with indium.

Copper doping with small supplements of cadmium allows you to make more wear-resistant wires on the lines of electrical transport. Copper with the additive of cadmium is almost no electrical conductivity of pure copper, but noticeably exceeds its strength and hardness.

Cadmium is included in the low-melting alloy of Wood (Wood "S Metal) containing 50% bismuth, 25% lead, 12.5% \u200b\u200btin, 12.5% \u200b\u200bcadmium. Wood alloy can be melted in boiling water. It is curious that the first letters of the alloy components of Wood form an abbreviation wax. It was invented in 1860 not a very famous English engineer B. Wood (

B. Wood. ). Often this invention is mistakenly attributed to its namesake - the famous American physics Robert Williams Voodoo who was born only eight years later. Lightweight cadmium alloys are used as material to produce thin and complex castings, in automatic fire-fighting systems, for glass spike with metal. Solders containing cadmium are quite resistant to temperature fluctuations.

A sharp leap of demand for cadmium began in the 1940s and was associated with the use of cadmium in the nuclear industry - it turned out that it absorbs neutrons and regulating and emergency rods of atomic reactors began to make out of it. Cadmium ability to absorb neutrons strictly defined energies is used in the study of neutron beam energy spectra.

Cadmium compounds. Cadmium forms binary compounds, salts and numerous complex, including organometallic, compounds. In solutions of the molecule of many salts, in particular halides, are associated. Solutions have a weakly acid medium due to hydrolysis. Under the action of alkalis solutions, starting with pH 7-8, the main salts are deposited.

Oxide Cadmia

CDO. They are obtained by interacting with simple substances or calcining hydroxide or cadmium carbonate. Depending on the "thermal history", it can be greenish-yellow, brown, red or almost black. This is partially due to particle size, but is a greater extent the result of the defects of the crystal lattice. Above 900 ° C cadmium oxide of the fly, and at 1570 ° C completely disposed. It has semiconductor properties.

Cadmium oxide is easily dissolved with acids and poorly in alkalis, it is easily restored by hydrogen (at 900 ° C), carbon monoxide (above 350 ° C), carbon (above 500 ° C).

Cadmium oxide is used as the material of the electrodes. It is part of lubricating oils and charges for special glasses. Cadmium oxide catalyzes a number of hydrogenation and dehydrogenation reactions.

Hydroxide Cadmium

CD (Oh. ) 2 falls in the form of a white sediment from aqueous solutions of cadmium salts (II. ) When adding alkali. Under the action of very concentrated alkali solutions, it turns into hydroxococcal modes, such asNa 2 [CD (OH ) four ]. Cadmium hydroxide reacts with ammonia to form soluble complexes:CD (OH) 2 + 6NH 3 · H 2 O \u003d (OH) 2 + 6H 2 OIn addition, cadmium hydroxide proceeds to the solution under the action of alkaline elements cyanides. Above 170 ° C is decomposed to cadmium oxide. The interaction of cadmium hydroxide with hydrogen peroxide in aqueous solution leads to the formation of a diverse peroxide.

Cadmium hydroxide is used to obtain other cadmium compounds, as well as as an analytical reagent. It is part of the cadmium electrodes in current sources. In addition, cadmium hydroxide is used in decorative glasses and enamels.

Fluoride Cadmium

CDF. 2 Little soluble in water (4.06% by weight at 20 ° C), not soluble in ethanol. It can be obtained by the action of fluorine on metal or fluoroodorod to the cadmium carbonate.

Cadmium fluoride is used as an optical material. It is part of some glasses and phosphors, as well as solid electrolytes in the chemical sources of current.

Chloride Cadmia

CDCL 2 is well soluble in water (53.2% by weight at 20 ° C). Its covalent nature determines the relatively low melting point (568.5 ° C), as well as solubility in ethanol (1.5% at 25 ° C).

Cadmium chloride is obtained by interacting with cadmium with concentrated hydrochloric acid or metal chlorination at 500 ° C.

Cadmium chloride is a component of electrolytes in cadmium galvanic elements and sorbents in gas chromatography. It is part of some solutions in photographs, catalysts in organic synthesis, fluxes for growing semiconductor crystals. It is used as a drive with dyeing and tissue printing. Cadmieraganic compounds are obtained from cadmium chloride.

Bromide Cadmia

Cdbr. 2 forms scaly crystals with pearl brilliance. It is very hygroscopic, well soluble in water (52.9% by weight at 25 ° C), methanol (13.9% by weight at 20 ° C), ethanol (23.3% by weight at 20 ° C).

The cadmium bromide is obtained by metal bromination or the action of bromomotodor to the cadmium carbonate.

The cadmium bromide serves as a catalyst in organic synthesis, is a stabilizer of photoemulsions and a component of virifying compositions in the photo.

Iodide Cadmia

CDI 2 forms brilliant crystals in the form of leaves, they have a layered (two-dimensional) crystal structure. It is known to 200 politicizes of cadmium iodide, differing in the sequence of layers with hexagonal and cubic tight packaging.

Unlike other halogen, cadmium iodide is not hygroscopic. It is well soluble in water (46.4% by weight at 25 ° C). Cadmium iodide is obtained by means of heating or in the presence of water, as well as the action of iodorodor to carbonate or cadmium oxide.

Cadmium iodide serves as a catalyst in organic synthesis. It is a component of pyrotechnic compositions and lubricants.

Sulfide Cadmia CDS was probably the first connection of this element in which the industry is interested. It forms crystals from lemon yellow to orange-red. Sulfide Cadmium has semiconductor properties.

In water, this connection is practically dissolved. It is also resistant to the action of alkali solutions and most acids.

Cadmium sulfide is obtained by the interaction of cadmium and sulfur vapor, precipitation of solutions under the action of hydrogen sulfide or sodium sulfide, reactions between cadmium and seleraban compounds.

Cadmium sulfide is an important mineral dye, before it was called cadmium urace.

In the painting case, the cadmium yellow later began to apply wider. In particular, she painted passenger cars, because, in addition to other advantages, this paint was well opposed by steam smoke. As the coloring substance, cadmium sulphide was also used in textile and soap-made industries. Appropriate colloidal dispersions were used to obtain color transparent glasses.

In recent years, the pure sulfide of cadmium is displaced by cheaper pigments - cadmopone and zincadmium lithonone. Cadmontone is a mixture of cadmium sulfide and barium sulfate. It is obtained by mixing two soluble salts - cadmium sulfate and barium sulphide. As a result, a precipitate is formed containing two insoluble salts:

CDSO 4 + BAS \u003d CDS

Ї + Baso 4

Cycochadmium lithopone contains also zinc sulfide. In the manufacture of this dye, three salts are precipitate at the same time. Lithopon - cream color or ivory color.

With the addition of cadmium selenide, zinc sulfide, mercury sulfide and other compounds Cadmium sulfide gives thermally stable pigments with bright color from pale yellow to dark red.

Sulfide Cadmia attaches a flame blue color. This property is used in pyrotechnics.

In addition, cadmium sulphide is used as an active medium in semiconductor lasers. It is as follows as a material for the manufacture of photocells, solar panels, photodiodes, LEDs, luminophores.

Selenide Kadmia CDSE forms dark red crystals. It does not dissolve in water, decomposed with salt, nitric and sulfuric acids. Selenide cadmium is obtained by fusion of simple substances or gaseous cadmium and selenium, as well as precipitation of cadmium sulfate under the action of selenium, cadmium sulfide reaction with selenium acid, interaction between cadmium and selenium-organic connections.

Selenide Cadmia is a phosphor. It serves as an active medium in semiconductor lasers, is the material for the manufacture of photoresistors, photodiodes, solar panels.

Selenide Cadmia is a pigment for enamels, glazes and artistic paints. Selenide cadmium paint ruby \u200b\u200bglass. It was he, and not chromium oxide, as in Rubina, made the Ruby-red stars of the Moscow Kremlin.

Telluride Cadmia CDTE can be painted from dark gray to dark brown. It does not dissolve in water, but decomposes with concentrated acids. It is obtained by the interaction of liquid or gaseous cadmium and tellurium.

Having semiconductor properties of cadmium telluride use as X-ray detector and

g. -The emission, and mercury-cadmium telluride has been widely used (especially for military purposes) in IR detectors for heat out.

With violation of stoichiometry or impurities (for example, copper and chlorine atoms), cadmium television acquires photosensitive properties. It is used in electrophotography.

Cadmoreorganic compounds CDR 2 and CDRX (R \u003d CH 3, C 2 H 5, C 6 H 5 and other hydrocarbon radicals, x - halogens, OR, SR, etc.) are usually obtained from the corresponding Grignar reagents. They are thermally less resistant than their zinc analogs, but are generally less reactive (usually do not ignite in air). Their most important area of \u200b\u200bapplication is the preparation of acid chloride ketones.

Biological role of cadmium. Cadmium is found in the organisms of almost all animals (in ground-based about 0.5 mg per 1 kg of mass, and in marine - from 0.15 to 3 mg / kg). At the same time, it is believed to the most toxic heavy metals.

Cadmium focuses in the body mainly in the kidneys and liver, while the cadmium content in the body increases. It accumulates in the form of complexes with proteins that participate in enzymatic processes. Finding into the body from the outside, the cadmium has an inhibitory effect on a number of enzymes destroying them. Its action is based on binding a group -shh cysteine \u200b\u200bresidues in proteins and inhibition of SH-enzymes. It can also inhibit the action of zinc-containing enzymes, replacing zinc. Due to the proximity of ionic radii calcium and cadmium, it can replace calcium in bone tissue.

People are poisoned by cadmium, using water contaminated by cadmium-containing waste, as well as vegetables and grain, growing on lands located close to refineries and metallurgical enterprises. Special ability to accumulate cadmium mushrooms. According to some information, cadmium content in mushrooms can reach units, tens and even 100 and more milligrams per kg of own mass. Cadmium compounds are among harmful substances in tobacco smoke (one cigarette contains 1-2 μg of cadmium).

The classic example of chronic poisoning by cadmium is the disease for the first time described in Japan in the 1950s and the name "ITAY-ITAY". The disease was accompanied by strong pain in the lumbar region, pain in the muscles. The characteristic signs of irreversible kidney damage appeared. Hundreds of fatal outcomes "ITAY-ITAY" were recorded. The disease took a massive nature due to the high pollution of the environment in Japan at the time and specifics of the Japanese food - predominantly rice and seafood (they are able to accumulate cadmium in high concentrations). Studies have shown that the sick "ITAY-ITAI" consumed up to 600 μg of cadmium per day. In the future, as a result of measures for environmental protection, the frequency and sharpness of syndromes, similar to "ITAY-ITAY" decreased noticeably.

In the United States, the relationship was discovered between the cadmium content in the atmosphere and the frequency of deaths from cardiovascular diseases.

It is believed that without harm to health in the human body, about 1 μg of cadmium per 1 kg of own weight can be received per day. In drinking water, cadmium should not contain more than 0.01 mg / l. The antidote in the poisoning of cadmium is selenium, however, the use of products rich in this element leads to a decrease in sulfur content in the body, and in this case, cadmium becomes dangerous again.

Elena Savinkina

LITERATURE Popular Library of Chemical Elements. M., Science, 1977
Karapetyanz M.Kh., Drakin S.I. General and inorganic chemistry. M., Chemistry, 1992
Greenwood N.N., Earnshaw A. Chemistry of the Elements, Oxford: Butterworth, 1997

Traditionally, cadmium sulfide was used as a dye. It can be seen on the canvases of such great artists as Van Gogh, Claude Monet, Matisse. In recent years, interest in it is associated with the use of cadmium sulfide as a film coverage of solar panels and in photosensitive devices. This compound is characterized by good ohmic contact with many materials. Its resistance does not depend on the size and direction of the current. Due to this, the material is promising for use in optoelectronics, laser engineering, LEDs.

general description

The cadmium sulfide is an inorganic compound that is found in nature in the form of rare minerals of zinc decking and hooling. They do not represent interests for industry. The main source of cadmium sulfide is artificial synthesis.

In appearance, this connection is yellow powder. Shades can vary from lemon to orange-red. Due to its bright color and high resistance to external influences, cadmium sulphide was used as a high-quality dye. The substance has received wide availability since the 18th century.

Chemical compound formula - CDS. It has 2 structural shapes of crystals: hexagonal (Wurcite) and cubic (zinc cheating). Under the influence of high pressure, the third form is also formed, like a stone salt.

Cadmium Sulfide: Properties

The material with the hexagonal structure of the lattice has the following physicomechanical properties:

• melting point - 1475 ° C;
• density - 4824 kg / m 3;
• linear expansion coefficient - (4.1-6.5) MKK -1;
• moos hardness - 3.8;
• sublimation temperature - 980 ° C.

This connection is a direct semiconductor. When irradiated with light, its conductivity increases, which makes it possible to use the material as a photoresistor. When doping with copper and aluminum, the fluorescence effect is observed. CDS crystals can be used in solid-state lasers.

The solubility of cadmium sulfide in water is absent, in dilute acids - weak, in concentrated hydrochloric and sulfuric acid - good. It also solisits CD well.

The following chemical properties are characteristic for the substance:

• precipitated when exposed to a solution of hydrogen sulfide or alkali metals;
• when reacting with hydrochloric acid, CDCl 2 and hydrogen sulfide are formed;
• when heated in an overpressure of oxygen in the atmosphere is oxidized to sulfate or oxide (it depends on the temperature in the firing furnace).

Obtaining

Cadmium sulfide is synthesized in several ways:

• when interacting vapor cadmium and sulfur;
• in the reaction of selerarganic and cadmium-containing compounds;
• the precipitation of the solution under the influence of H 2 S or Na 2 S.

Films based on this substance are manufactured using special methods:

• chemical precipitation with the use of thiocarbamide as a source of sulfide anions;
• pulverization with subsequent pyrolysis;
• method of molecular bunch of epitaxy, at which crystals are cultivated under vacuum conditions;
• as a result of the sol-gel of the process;
• method of ionic spraying;
• anodization and electrophoresis;
• by screen printing.

For the manufacture of the pigment, the precipitated solid sulfide of cadmium was washed, calcined to obtain a hexagonal shape of the crystal lattice, and then crushed to the powdered state.

Application

Dyes based on this compound have high thermo- and light-resistance. Selenide additives, cadmium telluride and mercury sulfide allow you to change the color of the powder on green and red and purple. Pigments are used in the production of polymer products.

There are other applications of cadmium sulphide:

• detectors (recorders) of elementary particles, including gamma radiation;
• thin film transistors;
• piezoelectric converters capable of working in the GHz range;
• production of a nanowire and tubes that are used as fluorescent labels in medicine and biology.

Solar panels on cadmium sulphide

Thinkeeper solar panels are one of the last inventions in an alternative energy. The development of this industry is becoming more relevant, since the reserves of minerals serving to receive electricity are rapidly depleted. The advantages of solar cells based on cadmium sulfide are the following:

• lower material costs in their manufacture;
• an increase in the efficiency of solar energy transformation into electric (from 8% for traditional batteries to 15% at CDS / CDTE);
• the possibility of energy generation in the absence of direct rays and the use of batteries in foggy areas, in places with increased air dusting.

Films used for the manufacture of solar cells have a thickness of only 15-30 microns. They have a grainy structure, the size of the elements of which is 1-5 microns. Scientists believe that thin-film batteries in the future will be able to become an alternative to polycrystalline due to unpretentious operating conditions and long service life.

The invention can be used in inorganic chemistry. The method of obtaining crystalline sulfide of cadmium includes the premises of sulfate-generation bacteria into a synthetic medium containing metals, and the addition of nutrients comprising solutions of vitamins, salts, cofactors. DESULFOVIBRIRIC SP. DESULFOVIBRIA SP is used in cultivation. A2, and a synthetic medium containing a source of cadmium ions is a solution of cadmium chloride. Concentration of cadmium ions in a synthetic medium 150 mg / l. Aluminum foil is placed in the cultivation tank, cultivation is carried out at 28 ° C for 18 days. The sediment containing cadmium sulphide crystals are collected from the foil and from the bottom of the bottle of the cadmium sulfide. The invention allows to obtain cadmium sulphide from wastewater and liquid waste of metallurgical enterprises. 2 Il., 3 tab., 1 pr.

Figures for the Patent of the Russian Federation 2526456

The invention relates to a method for producing pure cadmium sulfide (CDS) from solutions containing metals using sulfate-generating bacteria (CRH).

The proposed method can be used to obtain pure cadmium sulphide from wastewater containing metal ions, including cadmium, and liquid waste of mining and processing metallurgical enterprises. When applying the proposed method, selective deposition of cadmium in the form of sulphides is possible. This feature allows the use of liquid waste of metallurgical enterprises and wastewater as a secondary source of raw materials to obtain cadmium sulfides. The cadmium sulfide is used in semiconductor lasers, is the material for the manufacture of photocells, solar panels, photodiodes, LEDs, phosphor, pigments for art paints, glass and ceramics. Pigments based on cadmium sulfide are valued for their good temperature stability in many polymers, such as structural plastics. When replacing part of sulfur atoms in Selenium in CDS crystals, you can get a variety of colors of dyes from green and yellow to red-purple. Cadmium sulfide is a wide semiconductor. This CDS property is used in optoelectronics, both in photodetectors and solar panels. Cadmium sulfide single crystals produce scintillators to register elementary particles and gamma radiation.

In nature, Cadmia sulfide exists in the form of Grekenit and Howlit minerals, which are found in the form of yellow raids on a sphalese sequence (ZNS) and Smithsonite. Since these minerals are not widely distributed in nature, then for industrial use and scientific and technical works, cadmium sulfide is obtained by synthesis.

Cadmium sulphides are obtained by chemical methods - heating sulfur with cadmium or transmitting hydrogen sulfide over cadmium, oxide or cadmium chloride when heated. A method is known for obtaining powdered sulphides of cadmium and lead (RF Patent, No. 2203855, C01G 11/02, C01G 21/21, 2003). The invention relates to methods for producing powder materials in molten soles. Synthesis is carried out in the molten medium. The molten medium is formed by crystal thiochea, and as a metal-containing component includes anhydrous cadmium or lead acetates. Synthesis is carried out by mixing the powders of one of these salts and thioureards at 2-4-fold molar excess of thiourea and further shutter speed at 160-180 ° C for 20-30 minutes. The practical yield of products obtained by the proposed method, over 95%. In addition, they contain an admixture of elementary sulfur (3-4 wt.%), Which, depending on the further use of the product, can be washed with an organic solvent (toluene, carbon tetrachloride, etc.). The disadvantages of this method are the energy efficiency of production, the need to use special, expensive equipment. In addition, chemical production has a negative impact on the state of the environment.

It is known the formation of cadmium sulfide crystallites on the surface of the Klebsiella Pneumonia and Clostridium ThermoaceTicum (Aiking H. et al. Detoxification of Mercury, Cadmium, and Lead in Klebsiella Aerogenes NCTC 418 Growing In Continuous Culture // Appi Environ Microbiol. 1985 Nov; 50 (5 ). - P.1262-1267; PR Smith et al. Photoophysical and photochemical Characterization of Bacterial Semiconductor Cadmium-Sulfide Particles // Journal of the Chemical Society. Faraday Transactions. - 1998, 94 (9). - PP.1235-1241 ).

CDS crystallites, synthesized on the surface of the bacteria K. Pneumonia, effectively absorb UV light, which protects the bacterium from its destructive action. Pseudomonas Aeruginosa deep sea fluorescent bacterium removes cadmium from the medium by forming CDS crystallites on a cell wall (Wang Cl et al. Cadmium Removal By A New Strain of Pseudomonas Aeruginosa in Aerobic Culture // Appl. Environ. Microbiol. - 1997, 63. - PP .4075-4078). The sizes of cadmium sulfide crystallites range from dozens of micron out of cells to tens of angstroms inside the cells or on their surface. Crystallites of cadmium sulfide are formed only under certain conditions for the transmission of unfavorable environmental conditions.

The closest in essence and achieved the result to the claimed invention is the method of removing cadmium ions of low concentrations using a bioreactor with sulfate-generating bacteria (Hiroshi H. et al. Removal of Low Concentrated Cadmium Ions Using Fixed-Bed Sulfate-Reducing Bioreactor With FS Carrier // Journal Of the Mining and Materials Processing Institute Of Japan. - 2003. - V.119, No. 9. - PP.559-563). The reduction of heavy metal ions from the water occurred in a bioreactor, using sulfate-generating bacteria immobilized on a fiber slag, which was used as a biooster. In this process, sulfate ion sulfate in liquid is biologically converted to hydrogen sulfide (H 2 S), which reacts with metal ions to form ultra-dispersed metal sulfide particles. The resulting particles are harvested on the surface of the carrier in the upper part of the reactor, as a result of which the ions of heavy metals and their sulphides are accumulated. With continuous processing of water contaminated with 6 mg / l cadmium, almost complete removal was carried out for a period of about 30 days.

The disadvantage of the known method is that its use is possible only at low concentrations of cadmium ions in the medium and the crystalline sulfide of cadmium is not formed.

The objective of the present invention is to develop a method for producing crystalline sulfide of cadmium from solutions with an increased cadmium ion content (up to 150 mg / l), not containing impurities of other metals sulfides using sulfate-generating bacteria, resistant to increased concentrations of cadmium ions.

The task is solved by placing the HDC cadmium highly resistant to the synthetic medium, simulating wastewater containing metals, with the addition of nutrients, including solutions of vitamins, salts, cofactors, lactate, sodium sulfide, with further cultivation in the thermostat and drying, but Unlike the prototype, a CADMI is used to be resistant to cadmium ions, aluminum foil is added to Wednesday, cultivation is carried out at 28 ° C for 18 days.

Cultivation is carried out in a synthetic medium (Table 1 - composition of the synthetic medium) with the introduction of nutrients that stimulate the growth of bacteria. In the synthetic medium, nutrients and bivalent cadmium are added to the synthetic environment before sowing the culture of bacteria. The composition of the nutrients and the sequence of their introduction are indicated in Table 2. All nutrients other than vitamins are autoclaved at 1 atm 30 minutes. Vitamins are sterilized by filtration using a bacterial filter (0.20 microns).

Sowing is carried out in sterile containers with nested foil, the volume of inoculum (CRP culture) in the amount of 10% of the capacity of the tank. Inoculate tanks are poured with a synthetic medium (with all feed substances added) to the top. The pH of the medium is adjusted to 7.0-7.8 NaHCO 3 solution. The vials are closed with aluminum caps, seal and placed in a thermostat at 28 ° C. The formation of cadmium sulfide crystals occurs on foil and partially at the bottom of the bottle. After cultivation, the precipitate is collected from foil and centrifugation from the bottom of the bottle and dried in air. Examples of the invention in laboratory conditions are shown below.

Clean culture of SRB Desulfovibrio Sp. A2 was cultured on a synthetic medium containing bivalent cadmium at a concentration of 150 mgcd / l and an aluminum foil. Cadmium sulfide crystals were obtained on foil and partially at a 120 ml bottle. The vials with aluminum foil were sterilized with dry heat in the sterilizer at 160 ° C 2.2 hours.

Sowing was conducted in a sterile laminar cabinet, which before this was disinfected by an ultraviolet of 30 minutes. Before sowing, the synthetic medium (Table 1) was brought to a boil and then quickly cooled under the jet of cold water to remove dissolved oxygen. In the cooled to room temperature, the medium was made (Table 2) (based on 1 L) in the following sequence: vitamins (2 ml), saline solution (10 ml), solution of cofactors (1 ml), organic substrate - lactate (1 , 6 ml), Manto 3 solution (pH was adjusted to 7.0-7.8), sodium sulfide solution (2 ml). Cadmiac (CDCL 2 × 2.5H 2 O 2 g per 100 ml of water) was added in an amount of 16.72 ml per 1 liter of the synthetic medium (there was thus the concentration of cadmium in a medium 150 mg / l).

About 50 ml of the synthetic medium with additives and 10 ml of inoculum (culture of bacteria) were introduced into the vials with foil, after which it was filled with a medium to the top. Rubber plugs were carried to the edges of the bottles using a sterile needle, which reduced the likelihood of air oxygen penetration. At the end of the sowing, the vials were closed with aluminum caps, sealed vials were sealed and the thermostat was placed at 28 ° C. Crystallization of cadmium sulfide begins after 10 days of cultivation, with cultivation of 18 days sulphide cadmium crystallizes completely. The formed precipitate was collected from foil and centrifuging from the bottom of the bottle and dried in air. Mass formed sediment - 0.38 g

The study of the formed precipitation was performed using scanning electron microscopy (Philips SEM515 with an EDAX ECON IV Analyzer). The crystalline phase was determined by X-ray phase analysis on the SHIMADZU XRD 6000 diffractometer.

The size of the crystals defined under the scanning electron microscope was 50-300 μm, Figure 1 - Microfotography (EMS) of precipitation obtained during the cultivation of desulfovibrio sp. A2 In the presence of CD ions (150 mg / l) for 18 days, and the corresponding EMFs. The precipitation obtained during the cultivation of the Desulfovibrio Sp strain. A2, contained cadmium, sulfur, iron, oxygen, carbon and sodium, while carbon and oxygen took place from a carbon substrate, on which a sample lay. The ratio of elements is represented in Table 3 - the elemental composition of precipitation obtained during the cultivation of desulfovibrio sp. A2 In the presence of CD ions (150 mg / l) for 18 days (elements C and O occasion from the substrate on which the sample lay).

When studying precipitation using X-ray phase analysis, the formation of crystalline sulfide of cadmium was shown for 18 days (Figure 2 - diffractogram of precipitation obtained during cultivation of desulfovibrio sp. A2 in the presence of an initial CD concentration (150 mg / l) for 18 days. Designations on a diffractogram : CDS - Cadmium Sulfide).

In the control precipitation obtained by incubation without adding an inoculum, the crystalline phase was not observed and the main elements were cadmium and oxygen. The method proposed by us includes the possibility of using as a synthetic medium to obtain sulfide cadmium of wastewater and liquid waste of mining and processing metallurgical enterprises.

Table 1
Reagent	Concentration, mg / l
Na 2 SO 4	4000
MGCL 2 6H 2 O	400
NaCl (25%)	0,0125*
FESO 4 * 7H 2 O	2,1
H 3 in 3	0,03
MNCL 2 * 4H 2 O	0,1
COCL 2 * 6H 2 O	0,19
NiCl 2 * 6H 2 O	0,024
CUCL 2 * 2H 2 O	0,002
ZNSO 4 * 7H 2 O	0,144
Na 2 Moo 4 * 2H 2 O	0,036
CUSO 4 * 7H 2 O	750
H 2 O.	1 L.
* - ml / l

table 2
Solution (made by the amount per 1 liter of the synthetic medium)
	Reagent	Concentration
	4-aminobenzoic acid	4 mg / l
	Biotin (vitamin H)	1 mg / l
	Nicotinic Acid (Vitamin B 5)	10 mg / l
1. Vitamins (2 ml / l)	Calcium Pantothenate (Vitamin B 3)	5 mg / l
	Pyridoxine Dihydrochloride (Vitamin B 6)	15 mg / l
	Cyancobalamin (vitamin B 12)	5 mg / l
	Tiamine (vitamin B 1)	10 mg / l
	Riboflavin (Vitamin B 2)	0.5 mg / l
	Folic acid	0.2 mg / l
	KH 2 PO 4	20 g / l
	NH 4 Cl.	25 g / l
2. Salts solution (10 ml / l)	NaCl.	100 g / l
	KCL.	50 g / l
	CaCl 2.	11.3 g / l
	H 2 O.	1 L.
3. Cofactor solution (1 ml / l)	Naoh.	4 g / l
	Na 2 SEO 3 × 5H 2 O	6 mg / l
	Na 2 WO 4 × 2H 2 O	8 mg / l
4. Lactate solution (1.6 ml / l)
	Lactat	40%
5. Na 2 S solution (2 ml / l)
	Na 2 S × 9h 2 o	4.8 g

Table 3.
Element	Weight share (WT%)	Atomic Share (AT%)
FROM	7,56	15,1
O.	2,75	4,1
Na.	0,41	0,4
S.	23,3	44,5
CD	64,7	35,4
FE.	1,28	0,5

CLAIM

The method of obtaining crystalline cadmium sulfide by placing sulfate-generating bacteria into a synthetic medium containing metals, with the addition of nutrients, which includes solutions of vitamins, salts, cofactors, characterized in that desulfovibrio sp. A2, use a synthetic medium containing a cadmium ion source - a solution of cadmium chloride, and the concentration of cadmium ions in a synthetic medium 150 mg / l, aluminum foil is placed into the cultivation container, cultivation is carried out at 28 ° C for 18 days, and The sediment containing cadmium sulphide crystals are collected from the foil and from the bottom of the bottle of the cadmium sulfide.

Sulphides of some other metals (insoluble in water), for example, iron (II), manganese, zinc do not fall out of the acidic solution, since they are soluble in dilute mineral acids, therefore, it is not hydrogen sulfide, but ammonium sulfide (or sodium).

FESO 4 + (NH 4) 2 S \u003d FES (SEPT) + (NH 4) 2 SO 4

Some insoluble sulphides are capable of dissolving in an excess of ammonium sulfide solution or ammonium polysulfide (due to the formation of complex salts), others - no.

AS 2 S 3 (precipitate) + 3 (NH 4) 2 S \u003d 2 (NH 4) 3 (Solution)

Previously, the property of sulfides fall out of the solution under the action of hydrogen sulfide or ammonium sulfide (as well as dissolved or not dissolved in the excess of sulfide solutions or monovalent cations) was actively used in analytical chemistry for high-quality analysis and separation of metal mixtures (hydrogen sulfide analysis methods). Moreover, metal cations in analytical chemistry were classified into groups depending on their behavior under the action of hydrogen sulfide, the solution of ammonium sulfide and polysulfides (of course, it was not the only sign that the cations were classified in analytical chemistry, but one of the main).

Nowadays, hydrogen sulfide analysis methods have almost lost relevance, since hydrogen sulfide is poisonous. Moreover, hydrogen sulfide is not only poisonous, but also a cunning. First, the characteristic smell of hydrogen sulfide (rotten eggs) is well totable even at low concentrations, but with a long action of hydrogen sulfide on the experimenter, the smell of hydrogen sulfide ceases to be felt. As a result, it is possible to undergo the action of hazardous concentrations of hydrogen sulfide, without even suspecting it. Previously, when working with a hydrogen sulfide was in the order of things in laboratory classes on analytical chemistry, this happened often.

During the long years, analyst chemists were able to come up with a replacement of hydrogen sulfide and sulphides (so-called nonzerogenic analysis methods). In addition, physical and chemical and instrumental analysis methods are used in analytical chemistry.

I decided to obtain any insoluble sulphides from solutions of salts of metals and hydrogen sulfide. The choice fell on copper and cadmium (there was still a thought about mercury, but I refused it, since mercury was little, and it was in the form of a metal). Experiments spent on the street. Work at home with a hydrogen sulfide is a lesson for Kamikadze. This is permissible only in the presence of a hood.

He took copper sulfate and acetate cadmium (both qualifications "h"). Salts dissolved in warm water. At first weed processing with hydrogen sulfue copper sulfate. The test tube is quickly filled with black cereal cereal cus cus. He left the test tube for a while, departed away (do not forget - the hydrogen sulfide is poisonous!). When I came, I discovered a dark porridge from a solution and a precipitate in a tube instead of liquid.

Sold after copper the gas pipe and started cadmium. On the walls above the liquid, a yellow cadmium sulfide film was rapidly formed. Soon the solution was all in flakes. Again moved away. Fifteen minutes came, discovered a porridge in a test tube with yellow-orange divorces. This is CDS Cadmium Sulfide.

Despite the toxicity of cadmium, the cadmium sulphide is still used as a pigment - due to its beautiful color, light-resistance and chemical stability. Sometimes a solid solution is used between sulfide and cadmium selenide CD (S, SE): changing the ratio of selenium and sulfur in pigment, it is possible to vary its color.

__________________________________________________

Get cadmium sulphide using hydrogen sulfide water as a precipitate. Mark the color and character of the sediment. Write the reaction equation. Drain liquid from sediment and add a diluted solution to it HCL. Is there a dissolution of the sediment? Using the values \u200b\u200bof the work of solubility, explain why zinc sulfide and sulphide cadmium differently HCL.

Experience 8. Complex Cadmium Connections

To the solution of cadmium sulfate to add a solution of ammonia to dissolve the initial precipitate for dissolving. Write the reaction equation, given that the coordination number of cadmium in the resulting complex compound is four. Write the equation of electrolytic dissociation of the obtained comprehensive compound and the expression of the constant constant of the complex ion.

Experience 9. Hydrolysis of cadmium salts

but) Touch the neutral lacmus solution with cadmium sulfate solution medium. Explain the observed phenomenon. Write the hydrolysis reaction equation in molecular and ion form.

b.) To the solution of cadmium sulfate pour sodium carbonate solution. Watch the formation of a precipitate. What kind of hydrolysis level is the resulting substance? Write molecular and ionic equations of cadmium carbonate hydrolysis reactions in steps.

Experience 10. Hydrolysis of mercury salts (II)

but) In a small amount of water, dissolve several sulfate crystals or mercury nitrates (II). Observe the formation of sediment of the main salt. Test the reaction of the medium with a lactium. Write the reaction equation.

b.) Doing the same experience, acidic pre-water diluted solution HNO 3.. Compare the results obtained. Explain the observed phenomenon.

Experience 11. Obtaining mercury oxide (I)

To solvent HG (NO 3) 2 Pour alkali solution. What's happening? Mark the color of the resulting sediment. Write the reaction equation and structural formula HG 2 O..

Experience 12. Getting Calometra

From the soluble salt of mercury (i) get a calome. Write the reaction equation.

Copper, silver, gold.

Laboratory work number 6.

purpose: 1) experimentally investigate the properties of copper and its compounds;

2) Examine the properties of silver connections.

Experience 1. Copper properties

(Work in the exhaust cabinet)

a) copper interaction with acids

To a small amount of copper chips, pour diluted and concentrated solutions of acids in separate test tubes. HCl, H 2 SO 4 and HNO 3.

Observe the occurring phenomena. Those test tubes in which the reaction did not start, heated ( caution!). Does well interact with all acids? Pay attention to the color of the solution. What ion is the presence of this coloring? Determine by the characteristic odor and the color it is distinguished as a result of the reaction of the gase.

Write the reaction equations, explain the selection of coefficients.

Make a conclusion about the rehabilitation properties of copper.

b) the interaction of copper with ions of less active metals

Using the electrochemical number of voltages of metals, determine the ions of which metals in the solutions of their salts are able to oxidate copper.

In a solution of mercury nitrate (II), lower the end of the copper wire, pre-stripped by sandpaper. What are the signs of the flow of a chemical reaction? Write the reaction equation.

Experience 2. Preparation and properties of copper hydroxide (II)

but) To obtain a precipitate of copper hydroxide (II). Mark the color and character of the sediment. Write the reaction equation.

b.) Prove experimentally that copper hydroxide (II) exhibits amphoteric properties. Write the equations of reactions in molecular and ion forms.

in) Get copper hydroxide precipitate. Liquid with a sediment shake and heat up to boil. Why changed the color of the sediment? Write the reaction equation. What conclusion can be made about thermal resistance of copper hydroxide (II)?

Experience 3. Hydrolysis of copper salts (II)

but) Test an indicator paper salt of copper (II) salt. What is the medium reaction? Write the hydrolysis reaction equation.

b.) To the sulfate solution of copper (II) pour sodium carbonate solution. What signs of the flow of a chemical reaction are observed? Write an equation for the reaction of the reaction of copper sulfate (II) with sodium carbonate with the participation of water.

Experience 4. Obtaining and properties

Comprehensive salt of copper (II)

To the solution of the sulfate of copper (II), the ammonia solution is added dropwise to dissolving the main salt dropping down at the beginning. Write the equations of reactions. What ion includes copper atoms? What is the color of the formation ion? Make the equation of electrolytic dissociation of the resulting complex salt and write the expression of the constant constant of the complex ion. Prove the experimental way that there are sulfate ions in the solution.

Using the table of the work of solubility, pick up the reagent, with which you can detect the ions of copper (II) in the solution of the complex salt.

Experience 5. silver halides

but) Get silver halides. Pay attention to the nature and color of the compounds obtained. Write the equations of reactions. Experience precipitation to HNO 3.. Why silver halides do not dissolve in HNO 3.?

b.) Get precipitation of silver halides, filter and rinse with water. Take the action on them light (better than direct sunny). Write the equations of reactions.