Probing and Modulating Interactions of Drops, Bubbles and Particles with Implications for Chemical Engineering Processes

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Canada has a vast wealth of natural resources (e.g., minerals, crude oil, crude bitumen, natural gas), contributing significantly to the national economy. The interactions of liquid drops, gas bubbles and solid particles in complex fluid environment, particularly in the presence interface-active species (e.g., surfactants, polymers, particles), play a critical role in determine the efficiency and performance of numerous engineering processes in natural resources production (e.g., mineral flotation, bitumen extraction, oil/water separation, wastewater treatment). Previous studies have mainly focused on the intermolecular and surface interactions of soft materials and particle systems with "clean" interfaces (without interface-active species) and solid substrates with homogeneous surface chemistry. In practical engineering applications, however, interface-active species are widely present at solid/oil/water/gas interfaces and in bulk fluids, while many solid surfaces show heterogeneity in surface chemistry. Quantifying the interaction forces of these deformable material systems (e.g., drops, bubbles) and solids with surface heterogeneity in the presence of interface-active species is much more challenging, but is of fundamental and practical importance, which will be the main focus of this proposed research. The long-term objective of this proposed program is to elucidate the physicochemical properties and interaction mechanisms of drops, bubbles and particles in the presence of interface-active species (e.g., surfactants, polymers, nanoparticles) at the nano- and micro-scale. The short-term objectives are to (1) quantify the intermolecular and surface forces and establish the interaction mechanisms, particularly hydrophobic interaction, of liquid drops, gas bubbles and solid particles in aqueous media, by modulating surface chemistry, nanoscale heterogeneity, interfacial molecular mobility and water chemistry, in the presence of interface-active species, and (2) elucidate the interaction mechanisms of liquid drops, gas bubbles and solid particles with slippery surfaces, towards the development of novel slippery surfaces with controlled motion manipulation of drops/bubbles/particles. The proposed research will fill the knowledge gap on the fundamental interaction mechanisms of drops, bubbles and fine solids in the presence of interface-active species, particularly on quantification of their intermolecular and surface forces, the origin of hydrophobic interactions, and how hydrophobic effects and other surface forces contribute to their interaction behaviors (e.g., assembly, aggregation, and coalescence). The proposed research will also provide new insights on how to efficiently and effectively modulate these interactions in related engineering processes and help develop new materials and surfaces towards more efficient industrial processes. The research outcomes will facilitate the sustainable development of natural resources.