Bubble-particle systems are encountered in a wide range of industrial and 
environmental applications (flotation, bioreactors, slurry bubble columns) but 
the complex dynamics and interactions make the design and operation of such 
systems particularly challenging. This collaborative project between the 
University of Birmingham and McGill University (Montreal, Canada) aims at better 
understanding bubble-particle dynamics for novel applications in recycling.

This project is in collaboration with Professor Kristian Waters at McGill 
University, with the possibility of a research placement in his laboratories 
during the PhD. The student will also benefit from association with the EPSRC 
PREMIERE Programme Grant (https://premiere.ai) and be part of the PREMIERE 
research team including researchers from Birmingham, UCL and Imperial College.

Froth flotation is an established method of separating minerals in a slurry 
based upon the relative hydrophobicity of the particles and while it has been 
used for decades in the minerals industry to recover high value materials, less 
attention has been paid to ridding water of low value ones (e.g. plastics). 
Surface active agents known as collectors are used to enhance the particle 
separation with the polar part of the molecule becoming attached to surface of 
the target particles, with the hydrophobic part forming a surface which is 
attracted to bubbles in the liquid. The target particles rise with the bubbles 
to form a froth, which overflows the cell to be recovered. To maintain stable, 
small bubbles, frothing agents known as frothers are added. The froth flotation 
principle has the potential to be used in a variety of novel applications 
outside its original use in the minerals industry, for example in the recycling 
of plastics or battery materials. However, there are many aspects of its 
operation which are still poorly understood which affect the overall efficiency 
of the process.

This project will aim at investigating:
    - the dynamics of the frothing agent with the forming bubble interfaces: how 
the surface-active molecules alter the local interfacial tension and how 
Marangoni stresses may impact the performance of the froth and the attachment of 
the particles;
    - the interaction of the particles in the wake of the bubbles, where recent 
research has shown that this may be an important feature affecting the process 
selectivity, therefore efficiency. Both are critical to understanding the 
overall potential and efficiency of separation in novel applications.

The research will involve a series of experimental work involving visualisation 
of particle and bubble dynamics in small-scale test cells and measurements of 
interfacial properties including dynamic interfacial tension. These will feed 
into a finite volume numerical model based on open-source libraries (OpenFOAM or 
Basilisk). The interfacial properties measured in the lab will be implemented 
and 3D numerical simulations of bubbly flows will be performed. The dynamics of 
the solid particles will also be coupled to the bubble dynamics and will be 
compared to the experiments in terms of flow structure, entrainment in the wake 
and adhesion to the interface. The understanding of these phenomena at reduced 
scale will help in developing empirical or data-driven models for improving 
larger scale models and the design of flotation columns.

Funding: EPSRC DTP/College studentship in support of EPSRC PREMIERE Programme 
Grant (EP/T000414/1).

Applicant: Applicants must be eligible for home fee status and should have a 
first-class degree or good 2:1 (or equivalent) in Chemical Engineering, 
Mechanical Engineering, Computing, Mathematics, or related areas. We are looking 
for an enthusiastic and self-motivated person with a keen interest in conducting 
numerical simulations, as well as experimental work in the lab.

Deadline: The position will be filled as soon as a suitable person has been 
found; hence you are encouraged to apply as soon as possible (by email to 
t.abadie@bham.ac.uk or online https://www.birmingham.ac.uk/schools/chemical-
engineering/postgraduate/phd-research.aspx). PhD Starting October 2024 or soon 
after.