Titanium Dioxide To Treat Water

Scientists have discovered that adding silicone to titanium dioxide increases its ability to degrade aerosol and water-borne viruses.

Titanium dioxide (titanium IV oxide) is a naturally occurring compound that is used as a pigment in white paint, in sunscreens, in food colouring (E171), and as a disinfectant, used to kill viruses and bacteria and decompose organics via photocatalysis.

Silicone sealant is used to join glass plates in aquaria, silicone grease and lubricants are widely used in the automotive industry, silicone is used in cookware, liquid silicone is used as a dry cleaning solvent, silicone in gel form is used in medicine, and silicones are found as ingredients in shampoos, hair conditioners and gels.

Silicones are polymers made up of silicon as well as carbon, hydrogen, oxygen and sometimes other elements. They have the general chemical formula [R₂SiO]_n, where R is an organic group. Silicone polymers have an inorganic silicon-oxygen backbone: -Si-O-Si-O-Si-O-Si- with organic side chains attached to the silicon atoms.

Silicones can be produced from the reaction between chlorosilanes and water:
nSi(CH₃)₂Cl₂ + nH₂O →[Si(CH₃)₂O]_n + 2nHCl

In places where they don't have water treatment plants, water is disinfected using the SODIS method in which water is exposed to sunlight for its heat and ultraviolet radiation, but it takes a very long time to make water safe to drink. Treating titanium dioxide with silicone before adding it to the water sample to be disinfected can drastically reduce the time taken to disinfect the water.

Reference
Huma R. Jafry, Michael V. Liga, Qilin Li, Andrew R. Barron. Simple Route to Enhanced Photocatalytic Activity of P25 Titanium Dioxide Nanoparticles by Silica Addition. Environmental Science & Technology, 2010; 101231104927031 DOI: 10.1021/es102749e

Further Reading
Pure Substances and Mixtures
Elements and Compounds
Percentage Composition
Yield
Gravimetric Analysis
Water Analysis

Study Questions

1. What is the formula for titanium dioxide?
2. Calculate the percentage of titanium in titanium dioxide.
3. Calculate the percentage of oxygen in titanium dioxide.
4. A 100g sample of crude titanium oxide ore was known to contain 70% titanium dioxide. Calculate the mass of titanium present in this ore sample.
5. One method for obtaining pure titanium dioxide is to reduce the crude ore with carbon, then oxidize it with chlorine to produce titanium tetrachloride. The titanium tetrachloride is then distilled, then oxidized in a pure oxygen flame or plasma to produce pure titanium dioxide and regenerate the chlorine. Draw a flow chart to represent this purification process.
   
6. What property of titanium dioxide makes it useful as a pigment in white paint?
7. What is the formula for chlorosilane?
8. Given the general silicone formula [R₂SiO]_{n, calculate the percentage of carbon present in each of the following silicones:}
   
• R = methyl groups
  
• R = ethyl groups
• R = propyl groups
• R = butyl groups
9. Draw a structure for a silicone in which R are methyl groups.