Research Areas
The Centre has two key research programs which examine the interactions between the interfaces of liquid-liquid and solid-liquid systems. Within each multidisciplinary research program there are themes that explore key fundamental issues across interfacial science and engineering.
The PFPC has key research programs in separation science, emulsion technology, mineral processing, ultrasonics, environmental waste management, water treatment, nanoscience, geopolymers and tissue engineering.
LIQUID-LIQUID SYSTEMS
- Sorption at Liquid-Liquid Interfaces
- Ultrasonics
- Emulsion Behaviour
- Surfactant & Polymer Structure in Solution
SOLID-LIQUID SYSTEMS
- Minerals - Materials & Processing
- Controlled Porous Structures
- Suspension Rheology
- Surface Forces & Spectroscopy
LIQUID-LIQUID SYSTEMS
Sorption at Liquid-Liquid Interfaces
The transfer of a solute from one phase to another, thus effecting separation, is a process of considerable interest from both a fundamental and industrial point of view. In the Sorption at Liquid-Liquid Interfaces group the research is aimed at understanding interfacial phenomena in liquid-liquid extraction.
Key research areas include:
- development of analytical techniques for the measurement of metal ion transfer across the oil/water interface
- measurement of metal ion extraction kinetics in micellar systems
- study of ionic liquids as alternatives for volatile organic carbons
- development of improved contacting equipment for two phase systems
Key contact: Geoff Stevens
top of pageUltrasonics
The Ultrasonics team investigates the use of various physical and chemical effects generated by sound waves of frequency > 20 kHz (referred to as ultrasound) for the development of various applications. Ultrasound can induce (acoustic) cavitation in liquids, which refers to the growth and collapse of microbubbles. The near-adiabatic and inertial collapse of microbubbles heats the interior of these bubbles to a few thousand degrees. In addition to the generation of these micro hot spots, the collapse of these bubbles leads to radical production and several physical effects, such as shock wave formation, turbulent flow of the liquid surrounding the cavitation bubbles and microjet formation. Sonochemistry refers to the ultrasound induced chemical reactions, where the radicals mentioned above play a major role. Cavitation is also accompanied by light emission, known as Sonoluminescence (SL).
The key themes of the Ultrasonics program include:
- Investigation of the fundamental aspects of acoustic cavitation and
- Applied ultrasonics
The ultimate goal of the ultrasonics research team is to better understand the fundamentals of the ultrasound-driven physical and chemical events for delivering economically viable ultrasonics technology for industrial processes.
Key contacts: Franz Grieser, Muthupandian Ashokkumar
Emulsion Behaviour
In almost all emulsion systems, at some point in time, interaction takes place between soft deformable surfaces. The strength of this interaction depends on a number of factors and is likely to be significant at separation distances of less than 50 nm. Access to information on the primary forces acting at such small distances requires highly sensitive measurements. Research in this part of the program addresses the issues of droplet-droplet interactions both from an experimental approach using atomic force microscopy and from detailed mathematical modelling and will advance our general understanding of emulsion behaviour and stability.
The interfacial behaviour of emulsifiers may affect the interaction between deformable interfaces due to their influence on interfacial rheology. Research studies are also underway that examine specifically this aspect and will in the longer term complement the force modelling work on droplet interactions.
The research outcomes from these studies will improve our understanding of emulsion behaviour and potentially will have important implications for a broad range of industries.
Key contacts: Geoff Stevens, Franz Grieser, Derek Chan, Ray Dagastine, Michelle Gee
Surfactant & Polymer Structure in Solution
Complex fluids are common in everyday life and include foods, detergents and paints. The essential and unifying physics of complex fluid systems is that they are liquids composed of particles and or polymers which impart complex rheological behaviour when in flow. The key physics is determined by the interparticle forces or polymer-polymer interactions and conformation which are determined by the surface forces. Understanding the relationship between the surface forces and the rheological behaviour is essential in controlling the flow behaviour of these systems and improving their production and performance in applications.
The aim of this research program is to understand the relationship between the macroscopic rheological behaviour and the molecular forces and structure of the suspensions and polymer solutions.
This understanding has implications for almost all industrial processes as most involve the flow of materials in some manner.
Key contacts: Dave Dunstan, Derek Chan, David Boger
SOLID-LIQUID SYSTEMS
Minerals – Processing and Materials
The two main research topics in the Minerals – Processing and Materials theme are geopolymers and mineral processing, the latter concentrating on hydrometallurgy, predominately of gold ores and froth flotation.
Geopolymers are inorganic polymers made under alkali conditions from silicate and aluminate rich minerals or wastes. PFPC research is directed at: gaining insight into the fundamental microstructural differences between geopolymeric binders, alkali-activated systems, and ordinary Portland cement; development of novel geopolymeric concretes; and development of a new theoretical model of the molecular structure and microstructure of geopolymers.
The Centre’s mineral processing research is focussed on enhancing the economic viability and environmental performance of metal (gold) leaching and particle separation processes (flotation). The leaching of gold from complex ores involves the use of hydrometallurgical processes dominated in industry by the use of cyanide as lixiviate. Key directions for the work are to provide a fundamental basis for the alternative use of thiosulphate for difficult to treat ores and to identify difficult to treat phases through the combined use of microscopy and electron and proton beam techniques.
Link Geopolymer Technology and Mineral Processing
Key contacts: Jannie van Deventer, John Provis
Controlled Porous Structures
Another key research activity for the Centre is the controlled manufacture of porous structures using either inorganic or organic substrates and the effect of surface modification as well as the adsorption/desorption of ions, surfactants, proteins, cells and other molecular species to these structures. The focus of the work herein is in four key topic areas.
Development of macro-porous organic substrates for tissue engineering
The objective is to not only produce a suitable interconnected scaffold structure but to make the surface of the scaffold biocompatible.
Key contacts: Geoff Stevens, Andrea O'Connor
Development of Ion Exchange and Bio-reactive Barriers for the Adsorption of Solution Species for Use in Low Temperature Conditions e.g. Antarctica
Research is focussed on extending our knowledge of the temperature dependence of the adsorption and ion exchange processes.
Key contact: Geoff Stevens
Production of Meso- and Nano- Porous Substrates
A major research focus in this area is in the development of surfactant-templated mesoporous silica materials with potential applications in bioseparations. Another focus is also in the fabrication of porous inorganic structures using templating procedures.
Link Porous Inorganic Structures Laboratory
Key contacts: Geoff Stevens, Andrea O'Connor, Michelle Gee, Sandra Kentish, Rachel Caruso
Nanostructured Interfaces
The focus is to produce particulate substrates with bio-active, light, pH or conductivity responsive surfaces. A key aim is the retention of biological activity after adsorption to a surface and manipulation of the porosity of coatings and films such that hollow encapsulated particles can potentially act as responsive reservoirs for drug delivery.
Link Nanostructured Interfaces and Materials Group
Key contact: Frank Caruso
Suspension Rheology
A large range of industries dewater suspensions through the use of thickeners, filters and centrifuges. The aim is often to recover water in an effective manner for recycling although, more frequently, the use of the process is to produce particulate suspensions and cakes of controlled rheology or dryness. A key aim of this research is predictive design and optimized operation of these processes. Research in the dewatering area brings together laboratory based techniques for the characterisation of the suspension material properties of relevance to dewatering with phenomenological models of dewatering equipment. These models are based on fundamental dewatering theory. To date, models of continuous thickening, dead end filtration, plate and frame membrane filtration and batch and continuous centrifugation have been developed. At present, the model based work is examining decanter centrifuge prediction and porous network drainage in vacuum filtration. The key activities of the laboratory based work are focussed on determining the role of shear processes in flocculation and developing techniques to measure dewatering parameters for input to models across a wide range of solids concentrations. Software tools to aid the extraction of data from simple experiments have now been commercialized. Laboratory techniques for the extraction of data are being developed and a filter device, including software, has also been commercialized. Extension of the work from the minerals and water and waste water industries to the dairy and pulp and paper industries is a logical next step.
Previous research in suspension rheology has examined the relationship between the charge characteristics of coagulated particles and the yielding behaviour of concentrated suspensions of these particles. This research was useful in elucidating the role of small dispersant type molecules and that of particle size and size distribution in controlling the yielding and flow behaviour of suspensions. Much of the work utilised a vane technique to measure the yield stress. Extension of this research to nanoparticle systems is made difficult because of the need to scale down the size of the experiments to accommodate the fact that the manufacture of nanoparticles to produce large (i.e. kilogram) quantities is either not possible or prohibitively expensive. This has required conducting oscillatory measurements in rotational rheometry devices. A key aim of this research is to extract information on not only the failure of the suspension in shear but the way in which the presence of molecules on the surface of a particle modifies the route to failure. It is expected that such effects will be amplified for nanoparticle systems.
Key contact: Peter Scales
Surface Forces & Spectroscopy
The three key research themes of the Surface Forces and Spectroscopy area are focused on atomic force microscopy, biological cell and polymeric micelle adsorption and nanomaterials (quantum dots).
Atomic Force Microscopy
The use of the Atomic Force Microscope (AFM) as a tool for measuring the interaction forces between particles and surfaces, as well as a tool for imaging, is a key research activity of the PFPC. Similar to the Centre’s research on controlled porous structures, this research also seeks to understand the surface modification of surfaces and the adsorption/desorption of ions, surfactants, proteins, cells and other molecular species to surfaces, monitored by either AFM or spectroscopic techniques. A key focus of the AFM research is to study the relationship, through modelling, between the coupling of the fluid and the cantilever when the AFM is operated in a vibrational mode. Another key project is using the AFM to simultaneously monitor forces and adsorption processes.
Key contacts: Geoff Stevens, Derek Chan, Franz Grieser, Paul Mulvaney, Ray Dagastine
Biological Systems
The three dimensional structure of adsorbed species on surfaces, whether they be polymeric, monomeric or cellular, is key to our understanding of topics such as biocompatibility, bio-activity and particulate dispersion. A key objective of this research is to develop robust spectroscopic techniques for measuring the conformation of molecules at interfaces and to relate these conformational effects to observed interaction behaviour.
Link: Polymer & Surface Interactions Group
Key contacts: Michelle Gee, Ray Dagastine
Nanomaterials
Nanomaterials have a range of potential applications, including photonics. Current research efforts in the PFPC are examining the changes in spectroscopic behaviour of quantum dots caused by coatings and particle shape effects. The utilization of quantum dots in biomedical applications, including bioassay and protein separation is also being examined.
Links: Nanoparticle Laboratory
Key contacts:Paul Mulvaney