TiO2 Dispersion in Water: Challenges and Solutions

[Anne]

Hello fellow scientists.I am currently doing a project that requires me to make a stock solution of titanium dioxide which i will use to make different concentrations and measure absorbance and then plot a calibration curve which will be used to determine the concentration of Ti02 in an unknown sample of sunscreen product.
The problem is how do i dilute titanium dioxide powder using distilled water but according to some research i found that Ti02 is insoluble in water.Will this hinder or give incorrect readings in the measurement of absorbance.
If so how do i go about the making of the stock solution of Ti02 in order to get correct readings?

 

[Bystander]

This is probably referring to a "concentration" in a suspension/emulsion. Without specs on that it's a bit difficult to say.

 

[Anne]

I am planning to prepare the stock solution using about 20 grams of TiO2 powder and dilute with distilled water in a 50ml volumetric flask or beaker.

 

[Merlin3189]

I wonder how you will ensure even distribution, when you come to dilute it and when you are measuring absorption?
Maybe your TiO₂ is very finely ground and will stay in suspension? Perhaps you will need to check your stock bottle for any sign of settling? If it settles slowly enough, maybe a good shake just before use will ensure even dispersion?
TiO₂ is about 4x the density of water, so unless the particles are all very small (I've no idea how small), I'd expect some settling.
Do you know if sunblock manufacturers use any additives to aid dispersion and keep it in suspension?
This is a quote fom Patent US3663284 A (About which I know nothing! So I don't know whether there is any truth in it. They go on to claim methods for alleviating this problem.)

Purified grades of titanium dioxide disperse quite readily in water. In a dispersed system each solid particle is isolated from other particles by a layer of liquid. If the particles are very small and the liquid relatively viscous the particles may remain suspended for a considerable length of time. Though small, titanium dioxide particles are quite dense and in a medium such as water they tend to settle rapidly and form a hard packed sediment within less than a day's time. The sediment is hard because the particles, being independent of each other, can keep moving until they occupy the smallest possible volume. Such a sediment is almost impossible to redisperse.

Since TiO₂ is widely used, there is plenty of data about it. Eg. Horiba particle measurement , dispersion of TiO₂ for photocatalysts , (well, you can do this as well as I.)