Production and evaluation of floating photocatalytic composite particles formed using pickering emulsions and membrane emulsification

Floating photocatalytic composite particles were created by injecting a lipid (sunflower oil or liquefied cocoa butter) into an aqueous suspension of TiO2 nanoparticles using the process of membrane emulsification to control the (Pickering) emulsion size. The composite particle median diameters were controlled in a range from 80 to 300 μm. The composite particles floated in water and possessed photocatalytic activity, which was further enhanced by chemically incorporating silver particles into the TiO2 shell. The cocoa butter-based composite particles proved more robust and were not affected by the UV photocatalytic process. Using a combination of cocoa butter and hexane, for the core of the particles, it was possible to generate composite TiO2 and lipid particles with 36 mg of TiO2 per gram of particle. Optimal dye decolorization was achieved with a particle surface coverage of between 60 and 80%. Complete surface coverage resulted in a reduced reaction rate due possibly to reflection of the UV light.