Production and Evaluation of Floating Photocatalytic Composite Particles Formed Using Pickering Emulsions and Membrane Emulsification

Abstract

Floating photocatalytic composite particles were created by injecting a lipid (sunflower oil or liquefied cocoa butter) into an aqueous suspension of TiO 2 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 TiO 2 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 TiO 2 and lipid particles with 36 mg TiO 2 per gram of particle. Optimal dye decolourization 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.2

Advances in membrane emulsification. Part A: recent developments in processing aspects and microstructural design approaches

“…Another, more recent work on the production of Pickering emulsions with membrane technology was carried out by Holdich et al In an attempt to induce floating of TiO 2 photocatalytic particles on water, these were used to stabilise the interfaces of highly buoyant oil droplets formed via a membrane emulsification process within a dispersion cell, using a 5 and 14 µm pore size ‘Micropore Technology membranes’. TiO 2 ‐stabilised oil droplets had a span value of well below 0.8 and the apparent complete ‘enclosure’ of the oil droplets within the ‘TiO 2 shell’ could suggest that stabilisation of air (bubbles), which in turn would further enhance the buoyancy properties of the TiO 2 particles, may also be achievable …”

Design of novel starch-based Pickering emulsions as platforms for skin photoprotection

“…In addition, starch has been chemically modified to improve many aspects of pharmaceutical emulsions, such as: spreadability, oil absorption, water repellence, and heat tolerance [13]. Some UV filters, as titanium dioxide (TiO 2 ) and zinc oxide (ZnO), can be also used as SP for the stabilization of these emulsions [14]. TiO 2 has been incorporated in sunscreen formulations for N25 years, and it has been regarded as safe and effective, bringing together two of the most desirable features in pharmaceutical market.…”

Interfacial phenomena and droplet size of particle stabilized emulsions in oscillatory shear

“…This adds another degree of freedom and allows production of emulsions with high dispersed phase concentration, while maintaining control of droplet size. Although there have been number of membrane emulsification reports, most of them focused on surfactant‐stabilized emulsions with only few concerning PE, particularly using DME …”