By the middle of the 20th century, a term appeared in chemical science - metals of strategic importance. It meant a group of elements whose physicochemical properties made it possible to use them in the production of the military-industrial complex. We are talking about metals such as chromium, tantalum, niobium, molybdenum and tungsten. Vanadium, whose properties we will consider in this article, also rightfully occupies one of the central places among the metals used in modern mechanical engineering, ferrous metallurgy, tool and chemical production. The metal forms four oxides with oxygen, showing a valency of 2, 3, 4 and 5 in them. 5 which we will study in more detail.
Meet vanadium
In chemical science, there is a long-establishedthe rule stating that the characterization of a chemical element must begin with its position in the periodic system of D. I. Mendeleev. The chemical formula of vanadium as a simple substance is V, the serial number is 23, the atomic mass is 50, 9414. It is located in the fourth period, the fifth group and, together with niobium and tantalum, is a typical representative of refractory metals. Samples of a pure substance are plastic and have a silvery-gray color. The vanadium atom is a d-element, it has two s-electrons at the last energy level, however, those negative particles that are located at the d-sublevel of the same fourth level will also be valence.
Where is the metal found and what are its physical properties
The element itself cannot be found in its pure form in nature. But it is present as an obligatory component in polymetallic and iron ores. Earlier we talked about the plasticity and malleability of a simple substance, now we will add that the important physical properties of vanadium are high boiling and melting points, equal to 3400 ° C and 1920 ° C, respectively. Like titanium, it drastically deteriorates its physical and chemical parameters when contaminated with impurities such as nitrogen, hydrogen or oxygen. In particular, its ductility and mechanical strength are reduced, and vanadium becomes brittle.
Special chemical properties
Metal is capable of passivation, i.e. has a unique ability to withstand the action of aggressive chemical environments: solutions of acids, alkalis and s alts, forming a protective film on its surface -vanadium oxide. The crystal lattice of the element has a cubic structure. It should also be noted that the corrosion resistance of steels containing the element is very high, which allows them to be used as load-bearing fasteners for bridge supports and offshore oil drilling rigs. It is impossible to imagine modern tool production without vanadium-containing steels. Together with niobium, chromium and titanium, the element is used to alloy special alloys used in rocket science and the space industry. However, concentrated nitrate and sulfate acids, a solution of hydrogen fluoride in water, and a mixture of chloride and nitrate acids, called aqua regia, easily interact with the metal. The element vanadium as a simple substance can react with chlorine, bromine, sulfur, and the corresponding s alts are formed. With oxygen, it gives several oxides that differ greatly in their chemical properties. Consider them further.
Basic and amphoteric oxides
The metal forms two oxides, VO and V2O3, which exhibit typical basic properties. In the laboratory, monoxide is mined by the reduction reaction V2O5 fine vanadium powder. Basic oxides react with acid solutions to form the corresponding s alts. And already hydroxides can be obtained from them by carrying out an exchange reaction with alkalis. Vanadium (III) oxide is found as a component of the mineral karelianite, and is obtained in the laboratory by heating V2O5 with sulfur, coal or hydrogen. Both basic oxides have strongly pronounced reducing properties. Oxide VO2 is a typical amphoteric compound that reacts with both acids and alkalis. In a solution whose pH is less than 7, positively charged vanadyl ions VO2+ are found, giving the solution a light blue color, and polyvanadic acid s alts are formed in an alkaline medium. Vanadium (IV) oxide attracts water, i.e. is a hygroscopic substance, in reactions it behaves like a reducing agent.
Vanadium hemipentoxide
Compound whose formula is V2O5, is the most important metal oxide. It is a water-soluble orange crystalline substance that reacts with alkalis to form vanadates - s alts of metavanadic acid HVO3. It is widely used as a catalyst in the oxidation of sulfur dioxide to sulfuric anhydride in the industrial production of sulfate acid. Vanadium pentoxide has a rhombic crystal lattice and signs of amphotericity with a predominance of acidic oxide properties. In reactions it behaves as a strong oxidizing agent. The compound is used in glass technology, medicine and organic synthesis.
Methods for extracting vanadium from its compounds
We mentioned earlier that the metal is a component of iron ore. In blast furnace production, the element, together with impurities of carbon and phosphorus, passes into cast iron. When steel is smelted, vanadium oxide 5 precipitates in the composition of slag, where its content can reach 16%. Adding to ittable s alt and roasting the mixture in furnaces, a product is obtained, which is further dissolved in water. The resulting aqueous concentrate is treated with sulfate acid and V2O5 is isolated from it. To isolate pure vanadium from oxide, you can use the calciumthermy method - the reduction of metals using metallic calcium. To reduce technological costs in the reaction with vanadium pentoxide, aluminum is often used instead of calcium. The metal can also be obtained by reducing trivalent vanadium oxide with coal.
Biological role
Vanadium is present in living organisms as a trace element, which is part of the intercellular fluid of marine echinoderms. In holothurians and sea urchins, it is associated with proteins that carry out the function of transporting oxygen to cells and removing carbon dioxide. The content of the element is insignificant in the organisms of warm-blooded animals and humans, where it is in the composition of pancreatic enzymes, in neuroglia and nephrons. In plants, the trace element is involved as an enzyme in the dark phase of photosynthesis and affects the level of the chlorophyll pigment located in chloroplasts. It is also found in nodule bacteria, which are nitrogen fixers, in the tissues of higher fungi. As part of the chernozem, along with compounds of boron, copper, zinc and manganese, vanadium oxide affects soil fertility.
In our article, we studied the basic properties of vanadium and its oxides, and also considered the use of its compounds inindustry.
