title: Colloid Deposit Morphology and Clogging in Porous Media: Fundamental Insights Through Investigation of Deposit Fractal Dimension.
abstract: Experiments reveal a wide discrepancy between the permeability of porous media containing colloid deposits and the available predictive equations. Evidence suggests that this discrepancy results, in part, from the predictive equations failing to account for colloid deposit morphology. This article reports a series of experiments using static light scattering (SLS) to characterize colloid deposit morphology within refractive index matched (RIM) porous media during flow through a column. Real time measurements of permeability, specific deposit, deposit fractal dimension, and deposit radius of gyration, at different vertical positions, were conducted with initially clean porous media at various ionic strengths and fluid velocities. Decreased permeability (i.e., increased clogging) corresponded with higher specific deposit, lower fractal dimension, and smaller radius of gyration. During deposition, fractal dimension, radius of gyration, and permeability decreased with increasing specific deposit. During flushing with colloid-free fluid, these trends reversed, with increased fractal dimension, radius of gyration, and permeability. These observations suggest a deposition scenario in which large and uniform aggregates become deposits, which reduce porosity, lead to higher fluid shear forces, which then decompose the deposits, filling the pore space with small and dendritic fragments of aggregate.
authors.affiliation: University of Colorado Denver , Department of Civil Engineering, Campus Box 113, PO Box 173364, Denver, Colorado 80217-3364, United States.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Roth
authors.affiliation: Lawrence Berkeley National Laboratory , Earth Sciences Division, Mail Stop 74R316C, 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gilbert
authors.affiliation: University of Colorado Denver , Department of Civil Engineering, Campus Box 113, PO Box 173364, Denver, Colorado 80217-3364, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Mays
mesh_terms: D003102:Colloids / Q000737:chemistry*; D005374:Filtration / Q000295:instrumentation; D017709:Fractals; D009994:Osmolar Concentration; D010539:Permeability; D016062:Porosity; D012542:Scattering, Radiation
chemical_list: D003102:Colloids