Preferential positioning and phase exposure of granular particles at hydrophobic liquid-water interface

Significance Statement

Granular materials such as limestone and sand have been observed to exhibit an aptitude to aggregate with a hydrophobic phase, such as oil, thereby capturing substantial amounts of oil that floats on water surfaces. This unique phenomenon of selective positioning of the granular materials at the non-colloidal scale at the hydrophobic liquid-water interfaces is yet to be exhaustively studied and reported in the existing scientific literature. Consequently, it has therefore attracted profound interest as the comprehension of the granular particle behavior is needed for the possibility of utilizing readily available granular materials for capturing oil and curbing the mobility of floating oils as a treatment method.

In a recent paper published in Journal of Cleaner Production Daria Boglaienko and Berrin Tansel from the Department of Civil and Environmental Engineering at Florida International University proposed to analyze the observed variations in the positioning and behavior of the natural granular particles of limestone and quartz at the hydrophobic liquid-water interfaces. They also aimed at evaluating the dominant force impact on the particles behavior.

Foremost, experiments were carried out using dyed quartz and limestone particles with a 0.2-millimeter diameter for the fine particles and 0.5 millimeter for the medium sized particles. The researchers then used particles of different colors so that positioning of the particles with different sizes could be visually observed in the hydrophobic liquid water systems. They then selected silicon oil, tetradecane and crude oil for use as the hydrophobic liquid. Eventually, the researchers analyzed the behavior of the particles at the hydrophobic liquid and water interfaces through the application of the electrostatic image force theory.

By comparing theoretical and empirical results obtained, the researchers observed that the theoretical results did not support the assumption that the particle positioning at the liquid interface can be theoretically linked to gravitational force. The limestone which has active surface properties was observed to possess higher surface charge hence was able to cross the tetradecane-water interface abandoning the non-reactive tetradecane phase. They also observed that the zeta potentials of the aqueous limestone decreased upon addition of crude oil which explains why the limestone particles were held at the crude oil-water interface. These helped them conclude that the polar fractions of crude oil affected the surface charge and zeta potential of a particle.

The empirical observations have directed that the effects of the charge differences are more significant than the effect of the size difference in determining the position of a particle in a hydrophobic liquid, hydrophobic liquid-water interface and water phase. It is therefore important to note that slight differences in material composition affects surface characteristics thereby resulting in differences in the preferential positioning of the particles. The phenomenon presented here is of high interest and presents a new oil spills treatment technique which is inexpensive, simple and environmentally friendly.

Preferential positioning and phase exposure of granular particles at hydrophobic liquid-water interface - renewable global energy innovations

About The Author

Dr. Berrin Tansel is a professor in the Civil and Environmental Engineering Department at Florida International University (FIU). She has over 30 years of experience in environmental engineering, water quality management, physical-chemical treatment methods, contaminant-surface interactions and water infrastructure. She has received her PhD degree in environmental engineering from University of Wisconsin-Madison.

Dr. Tansel is an elected Fellow of the American Society of Civil Engineers (ASCE) and Environmental and Water Resources Institute (EWRI). She is a Diplomate of American Academy of Water Resources Engineers, and Board Certified Environmental Engineer by the American Academy of Environmental Engineers. She is a registered professional engineer in the State of Florida, USA. She has published over 200 journal papers, book chapters, technical reports and two books. Dr. Tansel is the editor in chief of the Journal of Environmental Management.

About The Author

Daria Boglaienko received her PhD in Civil Engineering (with specialization in Environmental), Florida International University. She holds two Master’s Degrees: from National Technical University in Ukraine and from Florida International University, where she got Outstanding academic achievement award. Her overall research experience can be characterized as one with a broad interdisciplinary focus. She studied benefits of alternative energy sources with a specialization on biogas production in waste treatment and anaerobic digestion processes. For her second master’s thesis she integrated several important aspects of a cover crop study to clarify mycorrhizal status of a plant, to investigate the benefits after its incorporation into soil, and to assess and prove its economic value.

Daria’s dissertation research was on floating crude oil capture and encapsulation using granular materials. She analyzed oil-particle aggregation from different perspectives, proposing and developing recommendations for a new environmentally friendly and inexpensive method to capture floating oils. Daria received Outstanding doctoral award in Civil Engineering and Worlds Ahead Graduate award from Florida International University.

Reference

Daria Boglaienko, Berrin Tansel. Preferential positioning and phase exposure of granular particles at hydrophobic liquid-water interface. Journal of Cleaner Production volume 142 (2017) pages 2629-2636.

Department of Civil and Environmental Engineering, Florida International University, Miami, FL, USA.

 

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