Researchers from Mainz discover that liquid flow changes surface chemistry of minerals, with implications for geological sciences.
A collaborative research team from the Max Planck Institute for Polymer Research (MPIP) in Germany and the University of Namur in Belgium discovered a fundamental, yet unnoticed, phenomenon that motion of water along a mineral surface changes the charge of that surface. The researchers published their finding in Science.
The international research team in Mainz led by Mischa Bonn studied how moving water, like in riverbeds or creeks, affects mineral surfaces and their dissolution. Remarkably, water flow along fluorite and glass surfaces makes these surfaces more positively charged. In the case of fluorite, a 100-fold increase in acid concentration was required to induce similar effects in static water.
Water molecules as reporters
Surfaces of minerals acquire a charge when immersed in water, as part of the minerals can be released from the surface as charged ions. This was known, but that moving water can change the surface charge was entirely unexpected. The research team in Mainz measured the surface charge of immersed minerals using the water molecules directly at the interface as reporters.
Water molecules have a positive and a negative end, and align toward the surface, depending on the surface charge. The interfacial water molecules were interrogated by overlapping two laser pulses of different color at the liquid-mineral interface, whereby a new color can be generated that provides extremely specific information about the interfacial region.
In this manner, both the orientation (pointing up- or downwards) and the number of oriented water molecules can be directly measured, which provides direct access to the surface charge.
The experiments show that flowing a liquid in contact with minerals induces a preferential dissolution of specific mineral constituents. In the case of fluorite, negatively charged ions are preferentially dissolved while positively charged ions remain at the mineral surface. The researchers were even able to show that the sign of the surface charge can be controlled with flow, so that water molecules could be made to reorient, depending on the presence or absence of flow.
The observed phenomenon seems to be rather ubiquitous in geology. Particularly because this phenomenon occurs not only for fluorite, but also for silica surfaces – silicates constitute more than half of the minerals in the earth crust. “These new insights on the fundamentals of mineral dissolution force us to reconsider well-established theories in weathering and environmental sciences to take into account changes in surface charge in addition to well-documented surface erosion.”, explains Mischa Bonn.
Prof. Dr. Mischa Bonn | Max Planck Institute for Polymer Research
Gluing with the Laser
30.06.2015 | Laser Zentrum Hannover e.V.
Innovative Modular Process Makes Plastic Film Coating Highly Efficient
09.06.2015 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP
Continuing current carbon dioxide (CO2) emission trends throughout this century and beyond would leave a legacy of heat and acidity in the deep ocean. These...
Glacier decline in the first decade of the 21st century has reached a historical record, since the onset of direct observations. Glacier melt is a global phenomenon and will continue even without further climate change. This is shown in the latest study by the World Glacier Monitoring Service under the lead of the University of Zurich, Switzerland.
The World Glacier Monitoring Service, domiciled at the University of Zurich, has compiled worldwide data on glacier changes for more than 120 years. Together...
Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.
What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...
Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.
The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...
Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.
04.08.2015 | Event News
23.07.2015 | Event News
10.07.2015 | Event News
04.08.2015 | Information Technology
04.08.2015 | Power and Electrical Engineering
04.08.2015 | Materials Sciences