Nano titanium dioxide

Titanium dioxide is one of the basic materials in everyday life. It has been widely used as white pigment in paints, cosmetics and foodstuffs. TiO2 exists in three crystalline modifications: rutile, anatase, and brookite. Generally, titanium dioxide is a semiconducting material which can be chemically activated by light. Under the influence of light the material tends to decompose organic materials. Compared with rutile and brookite, anatase shows the highest photoactivity. The TiO2 used in industrial products is almost exclusively from the rutile type.TiO2 always denotes the anatase modification. TiO2 electrodes is used to split water due to photocatalytic activity.

Nano-particulate TiO2

But TiO2 which is an n-type semiconductor has photocatalytic germicidal properties in the nano-particulate form. Photocatalytic action of titanium dioxide is used to remove organic and inorganic compounds from contaminated water and air and for the partial oxidation of organic compounds such as toluene. Photocatalyst are useful for antifouling, cleaning water, deodorization, pasteurisation, a treatment of waste water, decomposition of water, a control of algae growth, and various chemical reactions.

Process

To create disinfection or purification systems based on nanoparticulate TiO2, it has to be directly attached to a surface or to use the sol-gel process, for example, to apply a thin layer of particles on a substrates such as metal, alloys, glass, glass fibre, cellulose, plastics, ceramics and wood. The process is first to lay down on a surface an adhesive layer formed from a silica sol which is not affected by the photocatalysis. Then a layer of photocatalytic particles is deposited upto 100 nm thick using a sol containing nanoparticulate TiO2 and a silica additive which increases adhesion.

Other technologies

There are several technologies which might compete with nano TiO2 for applications in water purification based on activated charcoal and high-intensity UV light. Another nanotechnology widespered is the sol-gel process which is used to produce long nanofibres of alumina containing nano-titania particles. In this process the interstices in the fibres can be made to be of the same order as the dimensions of viruses and bacteria which can then be filtered from air or water.