Deposition of Latex Colloids at Rough Mineral Surfaces: An Analogue Study Using Nanopatterned Surfaces

Abstract

Deposition of latex colloids on a structured silicon surface was investigated. The surface with well-defined roughness and topography pattern served as an analogue for rough mineral surfaces with half-pores in the submicrometer size. The silicon topography consists of a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ∼ 5.5 under both favorable and unfavorable adsorption conditions using carboxylate functionalized colloids to study the impact of surface topography on particle retention. Vertical scanning interferometry (VSI) was applied for both surface topography characterization and the quantification of colloidal retention over large fields of view. The influence of particle diameter variation (d = 0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions was studied as a function of flow velocity. Despite electrostatically unfavorable conditions, at all flow velocities, an increased retention of colloids was observed at the rough surface compared to a smooth surface without surface pattern. The impact of surface roughness on retention was found to be more significant for smaller colloids (d = 0.3, 0.43 vs. 1, 2 μm). From smooth to rough surfaces, the deposition rate of 0.3 and 0.43 μm colloids increased by a factor of ∼2.7 compared to a factor of 1.2 or 1.8 for 1 and 2 μm colloids, respectively. For a substrate herein, with constant surface topography, the ratio between substrate roughness and radius of colloid, Rq/rc, determined the deposition efficiency. As Rq/rc increased, particle-substrate overall DLVO interaction energy decreased. Larger colloids (1 and 2 μm) beyond a critical velocity (7 × 10(-5) and 3 × 10(-6) m/s) (when drag force exceeds adhesion force) tend to detach from the surface irrespective of the impact of roughness. For polydisperse solutions, an increase in the polydispersity and flow velocity resulted in a reduction of colloid deposition efficiency due to the resulting enhanced double-layer repulsion. Quantification of surface topography variations of two endmembers of natural grain surfaces showed that half-pore depths and roughness of sedimentary quartz grains are mainly in the micrometer range. Grains with diagenetically formed quartz overgrowths, however, show surface roughness mainly in the submicrometer range. Thus, surface topography features applied in the here presented analogue study and resulting variation in particle retention can serve as quantitative analogue for particle reactions in diagenetically altered quartz sands and sandstones. The reported impact of particle polydispersity can have an important application for quantitative prediction of retention of varying types of minerals, such as different clay minerals in the environment under prevailing unfavorable conditions.

Surface Roughness Impacts on Granular Media Filtration at Favorable Deposition Conditions: Experiments and Modeling

“…Not surprisingly, when r roughness > r critical , media surface roughness enhances particle deposition, as has been widely reported. 19,22,44,45 In contrast, when r roughness < r critical , media surface roughness contributes to decreased particle deposition, relative to smooth surfaces; this may explain some reported outcomes as well. 19,21,22 To explore the applicability and validate the efficacy of the proposed framework for describing particle deposition on surfaces in response to variable media surface roughness, the framework was applied to data reported by Vanhaecke et al (1990) (upper left inset in Figure 4(b)), who systemically investigated the kinetics of Pseudomonas aeruginosa attachment on stainless steel with several levels of surface roughness.…”

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

“…For example, Chen et al (2010) coated stainless steel and aluminum alloys with zeolite to increase deposition surface roughness and increased colloid deposition by up to 50% 19 . Darbha et al (2010) reported a positive correlation between calcite surface roughness and the number of attached colloidal particles 20 ; they also found that surface roughness-enhanced particle deposition was more significant for smaller particles (0.3 μm), as compared to larger (2 μm) ones 21 . Zan et al (2008) investigated opportunities for enhancing orthopaedic stainless steel affinity to host tissue and also found that more colloidal particles attached on rough deposition surfaces than on smooth ones 22 .…”

Physiological characteristics, geochemical properties and hydrological variables influencing pathogen migration in subsurface system: What we know or not?

“…Surface roughness is proportional to the specific surface area of porous media. Higher surface roughness and specific surface area increases the active attachment sites to capture pathogens and inhibits their migration ( Morales et al, 2009 , Krishna Darbha et al, 2012 , Torkzaban and Bradford, 2016 ). For instance, crude biochar has rougher surface with the specific surface area 5 orders of magnitude larger than sand, resulting in a significantly stronger adsorption of Escherichia coli through biochar (log removal of 2.32) than sand (log removal of 0.29) ( Mohanty et al, 2014 ).…”