Flotation Fundamentals

Froth flotation is a key separation process in mineral processing. Although it is implemented in large industrial cells, its performance is governed by subprocesses that occur at the scale of bubbles, particles, and fluid interfaces. Our group investigates these flotation-relevant subprocesses under controlled conditions. We study how bubbles, particles, surfactants, collectors, frothers, salts, and ultrafine particles interact, and how these interactions determine particle attachment and detachment, froth stability, and separation selectivity.

What we study

Flotation performance depends on coupled physicochemical and hydrodynamic subprocesses at fluid interfaces. Surface chemistry, particle size, wettability, hydrodynamics, and interfacial mobility all influence whether particles collide with and attach to bubbles, whether bubbles coalesce or remain stable, and whether froths form and persist.

Rather than treating flotation only as a unit operation, we analyse the subprocesses that control its performance. This allows us to connect subprocess-level dynamics with flotation outcomes such as particle recovery, film rupture, bubble stability, froth behaviour, and reagent efficiency.

Our approach

We use controlled model experiments and complementary methods to investigate flotation subprocesses under well-defined conditions. This enables us to resolve governing mechanisms in complex multiphase systems and to provide a mechanistic basis for improved flotation technologies. Our work focuses on four main research areas:

Floatablity Measurements

We investigate how particles attach to bubbles, with particular attention to particle size, wettability, hydrophobicity, flow conditions, and chemical additives. This is especially important for fine and ultrafine particles, which are often difficult to reco­ver efficiently.

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Thin Films and Bubble–Bubble Coalescence

We study the drainage, deformation, rupture, and stabilization of thin liquid films between bubbles, and between bubbles and particles. These processes control bubble coalescence, bubble size, gas dispersion, froth lifetime, and attachment efficiency.

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Interfacial Flow

We examine how adsorbed materials such as surfactants, frothers, collectors, and particles modify flow near fluid interfaces. Interfacial mobility strongly affects film drainage, bubble–particle attachment, coalescence, and mass transfer.

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Surfactant–Particle Interactions

We investigate how surfactants, particles, and other surface-active species form mixed interfacial layers. These layers can modify surface tension, interfacial elasticity, film stability, and surface mobility, influencing key flotation subprocesses.

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From fundamentals to flotation technology

By linking interfacial mechanisms to flotation performance, our research supports the development of more selective, efficient, and sustainable flotation processes. This includes improved reagent strategies, better control of fine and ultrafine particles, and more efficient use of water, energy, and raw materials.

Sensors for flotation

Froth flotation slurries are opaque preventing optical access. We develop and adapt innovative measurement methods to gain insights on froth flotation flows and phase distributions to understand the mechanisms behind respective flotation performances.

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Particle-Bubble attachment

The efficiency of froth flotation depends on the attachment of hydrophobic particles on rising bubbles. We research the attachment process under well defined flow conditions to understand the fundamental mechanisms.

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Innovative reactor designs

A multitude of flotation cell designs exist, build to address different challenges in flotation. In collaboration with process engineering companies, we research lab-scale and pilot-scale flotation cells. Applying our advanced measurement methods we characterize properties of the fluid flow, bubble dispersion and particle motion.

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Efficient Copper Flotation in Water-Scarce Regions

ECuFlot is an international junior research group dedicated to the development of a new generation of water-efficient flotation ­techno­logies for copper reco­very. The project addresses one of the most pressing challenges in the raw-materials sector: how to secure copper supply for the energy transition while ore grades decline, fine-particle losses increase and mining regions face growing water scarcity.

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