The main oxidation state is 4+, although the states 3+ and 2+ are also known, but are less stable. This element burns in the air when it’s heated up to obtain the dioxide, TiO₂, and when it is combined with halogens. It reduces the water vapor to form the dioxide and hydrogen, and it reacts in a similar way with hot concentrated acids, although it forms trichloride with chlorhydric acid. The metal absorbs hydrogen to give TiH₂, and forms the nitride, TiN, and the carbide, TiC. Other known compounds are the sulfur TiS₂, as well as the lowest oxides, Ti₂O₃ and TiO, and the sulfurs Ti₂S₃ and TiS. Salts are known in the three oxidation states.

Applications

The titanium dioxide is extensively used as a white pigment in outside paintings for being chemically inert, for its great coating power, its opacity to UV light damage and its autocleaning capacity. The dioxide was also used once as a bleaching and opicifying agent in porcelain enamels, giving them a final touch of great brightness, hardness and acid resistance. A typical lipstick contais 10% titanium.

Titaium alloys are characterized by very high tensile strength even at high temperatures, light weight, high corrosion resistance, and ability to withstand extreme temperatures. ue to these properties they are principally used in aircraft, pipes for power plants, armour plating, naval ships, spacecraft and missiles. Titanium is as strong as steel but 45% lighter.

In medicine titanium is used to make hip and knee replacements, pace-makers, bone-plates and screws and cranial plates for skull fractures. It has also been used to attach false theet.

The alkaline earth titanates have some remarkable properties. The level of dielectric constants varies from 13 for the MgTiO₃, to various milliards for solid solutions of SrTiO3 in BaTiO₃. The barium titanate also has a dielectric constant of 10.000 close to 120ºC, which is its Curie point; it has low dielectric histeresis. The ceramic transductors that contain barium titanate are favorably compared with Rochelle salt in terms of thermal stability and with quartz in terms of the strength of the effect and the capacity to form the ceramics in various forms. The compound has bee used as ultrasonic vibrations generator and as a sound detector.

Titanium in the environment

Although it is not found unbound to other elements in nature, titanuim is the ninth most abundant element in the Earth's crust (0.63% by mass) and is present in most igneous rocks and in sediments derived from them. Important titanium minerals are rutile, brookite, anatase, illmenite, and titanite. The chief mined ore, ilmenite, occurs as vast deposits of sand in Western Australia, Norway, Canada and Ukraine. Large deposits of rutile in North America and South Africa also contribute significantly to the world supply of titanium. World production of the metal is about 90.000 tonnes per year, and that of titanium dioxide is 4.3 million tonnes per year.

The titanium dioxide, TiO₂, is commonly found in a black or brownish form known as rutile. The natural forms that are less frequently found in nature are the anatasite and the brooquite. Both the pure rutile and the pure anatasite are white. The black basic oxide, FeTiO₃, is found in the natural form as the natural mineral called ilmenite; this is the main commercial source of titanium.

Health effects of titanium

There is no known biological role for titanium. There is a detectable amount of titanium in the human body and it has been estimated that we take in about 0.8 mg/day, but most passes through us without being adsorbed. It is not a poison metal and the human body can tolerate titanium in large doses.

Elemental titanium and titanium dioxide is of a low order of toxicity. Laboratory animals (rats) exposed to titanium dioxide via inhalation have developed small-localized areas of dark-colored dust deposits in the lungs. Excessive exposure in humans may result in slight changes in the lungs. 

Effects of overexposure to titanium powder: Dust inhalation may cause tightness and pain in chest, coughing, and difficulty in breathing. Contact with skin or eyes may cause irritation. Routes of entry: Inhalation, skin contact, eye contact. 

Carcinogenicity: The International Agency for Research on Cancer (IARC) has listed titanium dioxide within Group 3 (The agent is not classifiable as to its carcinogenicity to humans.) 

Environmental effects of titanium

Low toxicity. When in a metallic powdered form, titanium metal poses a significant fire hazard and, when heated in air, an explosion hazard.

No environmental effects have been reported.

Titanium and water: reaction mechanisms, environmental impact and health effects

Seawater contains 1 ppb of titanium. In phytoplankton titanium concentrations up to 30 ppm (dry mass) were discovered. River water contains only 3 ppb. In dissolved form the element in mainly present as non-ionic Ti(OH)₄.

In what way and in what form does titanium react with water?

Titanium metal contains a surface layer of titanium oxide that prevents chemical reactions. When the layer is damaged it is usually restored rapidly. This not only occurs when it comes in contact with air, but also when it comes in contact with water. This reaction forms both titanium oxide and highly flammable hydrogen gas, according to the following reaction mechanism:

Ti (s) + 2H₂O (g) -> TiO₂ (s) + 2H₂ (g)

Some titanium compounds undergo hydrolysis reactions in water, for example titanium chloride.

Solubility of titanium and titanium compounds

Titanium only reacts with water after its protective titanium oxide surface layer is destroyed. It is therefore water insoluble. Titanium compounds generally are not very water soluble. Examples include titanium carbide and titanium oxide.

Why is titanium present in water?

Titanium is a component of various types of rock, such as rutile, anatase, ilmenite, titanite and brookite, and is therefore abundant in soils. Titanium oxide and other titanium compounds are among the most stable soil components. Consequently, only small amounts of titanium end up in water from rock weathering.
The metal is durable and is not excreted by the body, because of its protective titanium oxide surface layer. Consequently, it is applied in artificial joints and pacemakers that need not be replaced within the first 20 years. The oxide layer protects against most chemicals. Titanium is also applied in chemical installations. The larger part of produced metal is applied in plane and car engines, because its stability resembles that of steel and weighs 45% less. This results in an excellent strength-weight relation. Titanium is added to alloys, for example in stainless steel production.
Its durability and non-magnetic properties cause titanium to be an option for building submarines.
A commercially significant titanium compound is titanium dioxide, which is applied as a pigment in paint, synthetics, paper, fiber and cosmetics production. However, titanium application does lead to the production of water pollutants that disable direct discharge of wastewater. Titanium carbide is applied in cutting tool production, and titanium chloride is applied as a catalyzer and basic product for artificial mist, titanium- and titanium dioxide pigments.

What are the environmental effects of titanium in water?

Titanium is not a dietary requirement. It may have a biological function, because it positively influences grain growth and nitrogen fixation by Leguminosae. Plants contain 1 ppm titanium (dry mass) on average. In soils titanium solutions dissolve rapidly. Consequently, concentrations up to 5000 ppm are tolerated. The element in non-water hazardous, whereas halogenated titanium compounds may pose a risk in water. These are toxic to small water organisms and are harmful because they alter pH values. Elementary titanium is a risk in other environmental compartments, as well.
During titanium dioxide pigment production, sulphuric acids or iron vitriol may form, depending on the process. Sulphuric acid formation in seas probably negatively influences sea ecology. This also applies to rivers and other surface waters.
The LD₅₀ value for tetra isopropyl ortho titanate is known and is 7460 mg/kg for rats at oral intake.
Titanium naturally contains five non-radioactive isotopes, and eight instable isotopes.

What are the health effects of titanium in water?

The human body contains approximately 700 mg titanium, and our daily intake is approximately 0.8 mg. Only a small part of the total daily intake is absorbed by the body. Titanium does not play a significant role in any body functions. It is relatively non-toxic, because the body can tolerate relatively high doses and it does not accumulate. Existing hazards related to titanium are ascribed to the accompanying anion. For example, titanium halogen intake causes nausea and vomiting, and acidifies the body after re-absorption. Corrosion occurs at eye or skin contact, or when it comes in contact with mucous membranes.
One health effect of titanium not related to its presence in water is breathing in titanium dioxide particles with a very small particle size, leading to lung disease.

Which water purification technologies can be applied to remove titanium from water?

Titanium is present as a cation in acidic solutions and can therefore be removed by means of ion exchange. Iron vitriol that is formed in titanium dioxide pigment production is processes to acid or oxide and can than be applied as a precipitant in water purification.