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Release of colloids from primary minimum contact under unfavorable conditions by perturbations in ionic strength and flow rate

Abstract:

Colloid release from surfaces in response to ionic strength and flow perturbations has been mechanistically simulated. However, these models do not address the mechanism by which colloid attachment occurs, at least in the presence of bulk colloid-collector repulsion (unfavorable conditions), which is a prevalent environmental condition. We test whether a mechanistic model that pbkp_redicts colloid attachment under unfavorable conditions also pbkp_redicts colloid release in response to reduced ionic strength (IS) and increased fluid velocity (conditions thought prevalent for mobilization of environmental colloids). The model trades in mean-field colloid-collector interaction for discrete representation of surface heterogeneity, which accounts for a combination of attractive and repulsive interactions simultaneously, and results in an attached colloid population (in primary minimum contact with the surface) having a distribution of strengths of attraction. The model moderates equilibrium separation distance by inclusion of steric interactions. By using the same model parameters to quantitatively pbkp_redict attachment under unfavorable conditions, simulated release of colloids (for all three sizes) from primary minimum attachment in response to perturbations qualitatively matched experimental results, demonstrating that both attachment and detachment were mechanistically simulated. © 2014 American Chemical Society.