title: Contribution of Nano- to Microscale Roughness to Heterogeneity: Closing the Gap between Unfavorable and Favorable Colloid Attachment Conditions.
abstract: Surface roughness has been reported to both increase as well as decrease colloid retention. In order to better understand the boundaries within which roughness operates, attachment of a range of colloid sizes to glass with three levels of roughness was examined under both favorable (energy barrier absent) and unfavorable (energy barrier present) conditions in an impinging jet system. Smooth glass was found to provide the upper and lower bounds for attachment under favorable and unfavorable conditions, respectively. Surface roughness decreased, or even eliminated, the gap between favorable and unfavorable attachment and did so by two mechanisms: (1) under favorable conditions attachment decreased via increased hydrodynamic slip length and reduced attraction and (2) under unfavorable conditions attachment increased via reduced colloid-collector repulsion (reduced radius of curvature) and increased attraction (multiple points of contact, and possibly increased surface charge heterogeneity). Absence of a gap where these forces most strongly operate for smaller (<200 nm) and larger (>2 μm) colloids was observed and discussed. These observations elucidate the role of roughness in colloid attachment under both favorable and unfavorable conditions.
authors.affiliation: Department of Geology and Geophysics, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Rasmuson
authors.affiliation: Department of Extractive Metallurgy, Escuela Politécnica Nacional , Quito, Ecuador.
authors.forename: Eddy
authors.initials: E
authors.lastname: Pazmino
authors.affiliation: Department of Metallurgical Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Shoeleh
authors.initials: S
authors.lastname: Assemi
authors.affiliation: Department of Geology and Geophysics, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: William P
authors.identifier: 0000-0003-3126-3877
authors.initials: WP
authors.lastname: Johnson
mesh_terms: D003102:Colloids; D005898:Glass; D057446:Hydrodynamics; D016062:Porosity
chemical_list: D003102:Colloids