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 allowed them to be used in the production of the military-industrial complex. We are talking about metals such as chromium, tantalum, niobium, molybdenum and tungsten. Vanadium, the properties of which we will consider in this article, also rightfully occupies one of the central places among the metals used in modern engineering, ferrous metallurgy, tool and chemical production. The metal forms four oxides with oxygen, exhibiting a valency of 2, 3, 4, and 5 in them. Of the greatest practical interest is the compound with the highest degree of metal oxidation, V 2 O 5 , which we will study in more detail.
Getting to know vanadium
In chemical science, there is a long-established rule stating that the characterization of a chemical element must begin with its position in the periodic system Mendeleev. The chemical formula of vanadium as a simple substance is V, the serial number is 23, and 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 the pure substance are plastic and have a silver-gray color. The vanadium atom is a d-element, has two s-electrons at the last energy level, however, those negative particles that are located on the d-sublevel of the same fourth level will also be valence.
Where does metal occur and what are its physical properties
The element itself in its pure form cannot be found in nature. But it is present as a mandatory component in polymetallic and iron ores. Earlier we talked about the ductility and malleability of a simple substance, now we add that the important physical properties of vanadium are high boiling and melting temperatures, equal to 3400 ° and 1920 ° , respectively. Like titanium, it sharply worsens its physicochemical 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
The metal is capable of passivation, i.e. It has a unique ability to withstand the action of aggressive chemical environments: solutions of acids, alkalis and salts, forming a protective film on its surface - vanadium oxide. The crystal lattice of the element has a cubic structure. We also note 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 rigs. It is impossible to imagine modern tool production without vanadium-containing steels. Together with niobium, chromium and titanium, the element is used for alloying special alloys used in rocket science and 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 vanadium element as a simple substance can react with chlorine, bromine, sulfur, and the corresponding salts are formed. With oxygen, it gives several oxides that differ greatly in their chemical properties. Let's consider them further.
Basic and amphoteric oxides
The metal forms two oxides - VO and V 2 O 3 , which exhibit typical basic properties. In the laboratory, monoxide is obtained by the reduction reaction of V 2 O 5 with finely divided vanadium powder. Basic oxides react with acid solutions to form the corresponding salts. And already, hydroxides can be obtained from them by conducting an exchange reaction with alkalis. Vanadium (III) oxide is detected as a component of the mineral Karelianite, and it is obtained in laboratory conditions by heating V 2 O 5 with sulfur, coal or hydrogen. Both basic oxides have pronounced reducing properties. VO 2 oxide is a typical amphoteric compound that reacts with both acids and alkalis. In a solution, the pH of which is less than 7, positively charged vanadyl VO 2+ ions are found , which give the solution a light blue color, and polyvanadic acid salts 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
A compound of the formula V 2 O 5 is the most important metal oxide. This is a water-soluble crystalline substance of orange color, reacting with alkalis with the formation of vanadates - salts of metavanadic acid HVO 3 . 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 the predominance of acid oxide properties. It behaves like a strong oxidizing agent in reactions. The compound is used in glassmaking technologies, medicine and in organic synthesis.
Methods for extracting vanadium from its compounds
We mentioned earlier that metal is a component of iron ore. In blast furnace production, an element, together with impurities of carbon and phosphorus, goes into cast iron. When steel is smelted , vanadium oxide 5 is deposited in the composition of the slag, where its content can reach 16%. Adding salt to it and firing the mixture in furnaces, a product is obtained, which is further dissolved in water. The resulting aqueous concentrate is treated with sulfate acid and V 2 O 5 is isolated from it. In order to isolate pure vanadium from the oxide, one can use the method of calcethermia - the reduction of metals using metallic calcium. To reduce technological costs, aluminum is often used instead of calcium in the reaction with vanadium pentoxide. Metal can also be obtained by reduction of trivalent vanadium oxide with coal.
Biological role
Vanadium is present in living organisms as a trace element that is part of the intercellular fluid of marine echinoderms. In holothurians and sea urchins, it is associated with proteins, which perform the function of transporting oxygen to the cells and removing carbon dioxide. Slightly the content of the element in the organisms of warm-blooded animals and humans, where it is a part of pancreatic enzymes, in neuroglia and nephrons. In plants, the microelement is involved as an enzyme in the dark phase of photosynthesis and affects the level of chlorophyll pigment found in chloroplasts. It is also found in nodule bacteria, which are nitrogen-fixing agents, in the tissues of higher fungi. In the composition of 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 examined the use of its compounds in industry.