Maybe I'm not an expert in the material, but have used/purchased it for years. My first questions would be:
What are the costs involved compared to mining?
How much can be extracted this way per day/week/month compared to mining?
What is the future like for the natural supply of TiO2 through mining? Are we running out?
How does the imminent re classification of TiO2 to a class 1B carcinogen effect plans for re-cycling it?