Spontaneous Diffusiophoretic Microflows caused by Calcium Carbonate Artificial and Geological Systems

Open Access
Klara, Steven Scott
Area of Honors:
Chemical Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Darrell Velegol, Thesis Supervisor
  • Darrell Velegol, Honors Advisor
  • Kyle Jeffrey Magnuson Bishop, Faculty Reader
  • calcium carbonate
  • diffusiophoresis
  • microflow
  • flowfield
  • microchannel
  • electric field
  • diffusion
  • ion gradient
Diffusiophoretic flows are major factors of micro and nanochannel flows in natural rock formations, particularly ones composed of calcium carbonate. Calcium carbonate particles are sparingly soluble in water. Three different ions, Ca2+, HCO3-, and OH-, dissolve into the surrounding solution, but each of these ions has a different diffusion coefficient. The gradient created by these ions forms a compensatory electric field that can direct the flow of nearby charged particles and oil droplets. This flow is directed radially outward from the calcium carbonate particles across the surface on which the particle rests. The velocity of the pumped particles decays exponentially in relation to the distance away from the calcium carbonate. The flow fields of two separate calcium carbonate particles interfere with each other, causing the flow field to change depending on other calcium carbonate particles in the vicinity. The directionality of the flow can be changed by altering the zeta potential of the pumped particles or the surface; one such way to do this is to alter the pH of the solution. An increase in neighboring calcium carbonate pumps will lower the overall speed of the pumped particles, but increase the ultimate distance that they will travel. These flow fields are not only created by individual calcium carbonate particles synthesized in a lab, but also in geologic rock formations composed of calcium carbonate. As proven by the governing equations of both pressure-driven flow and diffusiophoretic flow, diffusiophoresis is more significant than pressure-driven flow through micro and nanochannels within geologic formations. Understanding the exact nature of these flows is important in academic research, as well as industrial application, especially within oil and gas fields. These flows may also reveal the nature behind the formation of several different geologic structures, and may provide specific insight as to how the land formations on this planet were formed.