MSc Student, Durham University, 2009-2010
PhD Student, Durham University, 2010-present
Adsorption kinetics of surfactants to solid-solution interfaces
I aim to further develop the work done by David Woods using flow cells to study the adsorption kinetics of surfactants to solid-solution interfaces
Surfactant adsorption to the liquid-solid interface is of great importance to many industrial and consumer processes; from detergency to crop spraying and drilling for oil, the understanding of how these molecules behave is crucial to their design and further efficiency improvement.
I have designed and built a new, open bench, Raman spectrometer for use in total-internal reflection (TIR) Raman spectroscopy. This design is an improvement to an existing Renishaw spectrometer adapted for TIR Raman use. The new spectrometer greatly improved time resolution and the open design allows for easy modification.
TIR Raman spectroscopy allows us to be surface-selective and measure the Raman spectrum only from very close to the interface, where the evanescent field excites molecules attached or very close to the surface. As this field decays exponentially with distance, only a small region at the interface is probed ~100 nm).
Using an in-line mixer we were then able to record adsorption and desorption isotherms on the surfaces. This technique utilised a continuously stirred tank to vary continually the concentration of solution entering the cell, hence a whole continuous range of concentrations (limited only by the time resolution) could be studied. The validity of our in-line mixer with solutions of the Raman-active molecules acetonitrile, methanol and sucrose.
The adsorption of various anionic surfactants, nonionic surfactants and cationic surfactants were investigated. Varying mixtures of nonionic and anionic surfactant adsorption on silica are covered briefly.
With the individual surfactants, we started our investigation with a plain (acid-washed) silica hemisphere, then investigated various coatings applied to silica, using the same TIR Raman technique.
My project aimed to investigate the processes by which surfactant solutions penetrate glass capillaries which have been made coated to be hydrophobic and then compare the data to models from the overflowing cylinder. By mounting the capillaries horizontally, gravitational effects can be eliminated, simplifying analysis of the data. Development of imaging techniques to view the meniscus using high speed cameras allows for accurate tracking of its progress along the capillary. Investigation of the effects of different types of surfactants and solutes; at different concentrations should help to reveal the processes by which the penetration occurs.
I enjoy badminton, squash, cycling, sailing, skiing, taking part in technical work for theatrical productions and live music events.
Personal Website: www.alexdudgeon.me.uk