MDS ANALYSIS OF BUBBLE ATTACHMENT
ABSTRACT
Jiaqi Jin and J.D. Miller
Department of Metallurgical Engineering, College of Mines and Earth Sciences,
University of Utah, Salt Lake City, UT 84112-0411 USA
Bubble attachment at hydrophobic surfaces is of critical importance in the flotation recovery of mineral
resources and fundamental experimental results have been reported in the literature describing the details
of film thinning, rupture, and displacement. Now, for the first time, bubble attachment phenomena are
examined using Molecular Dynamics Simulations (MDS). The simulation involves a nitrogen gas bubble
containing 900 nitrogen molecules in a water phase with 74,000 water molecules at the hydrophobic
molybdenite (001) surface. During the simulation period of 1 ns, film rupture occurs and the nitrogen gas
bubble attaches to the molybdenite (001) surface, resulting in a contact angle of about 90º. In contrast, the
film is stable at the hydrophilic quartz (001) surface and the bubble does not attach.
In this way, film thinning, rupture, and displacement are described with respect to interfacial water
structure for surfaces of different polarity. For example, details of film rupture are considered as hydrogen
bonds are broken during bubble attachment. Contact angles, determined from MD simulation after
stabilization of the three phase line of contact, are reported and these results agree well with experimental
and MDS sessile drop results. Further, the well-known Young equation is evaluated based on interfacial
energies established from MD simulation results.
Nitrogen gas bubble attached at the molybdenite (001) surface. The atoms’ color codes are as follow: green,
N; cyan, Mo; yellow, S; red, O; white, H.
KEYWORDS
MDS, Bubble attachment, Film thinning, Film rupture, Film displacement, Contact angle