Modeling colloid deposition on a protein layer adsorbed to iron-oxide-coated sand

Abstract

Our recent study reported that conformation change of granule-associated Bovine Serum Albumin (BSA) may influence the role of the protein controlling colloid deposition in porous media (Flynn et al., 2012). The present study conceptualized the observed phenomena with an ellipsoid morphology model, describing BSA as an ellipsoid taking a side-on or end-on A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT5 conformation on granular surface, and identified the following processes: (1) at low adsorbed concentrations, BSA exhibited a side-on conformation blocking colloid deposition; (2) at high adsorbed concentrations, BSA adapted to an end-on conformation promoted colloid deposition; (3) colloid deposition on the BSA layer may progressively generate end-on molecules (sites) by conformation change of side-on BSA, resulting in sustained increasing deposition rates. Generally, the protein layer lowered colloid attenuation by the porous medium, suggesting the overall effect of BSA was inhibitory at the experimental time scale.A mathematical model was developed to interpret the ripening curves. Modelling analysis identified the site generation efficiency of colloid as a control on the ripening rate (declining rate in colloid concentrations), and this efficiency was higher for BSA adsorbed from a more dilute BSA solution.

Deposition Kinetics of Colloidal Manganese Dioxide onto Representative Surfaces in Aquatic Environments: The Role of Humic Acid and Biomacromolecules

“…The observed greater deposition was independent of the collector surface type (i.e., negative silica, magnetite, and positive alumina in present study), revealing a more effective hinderance of colloidal MnO 2 mobility by BSA when deposited onto environmental surfaces. This finding was consistent with the previous observation of enhanced colloid deposition by absorbed BSA. − To deepen the understanding of this deposition behavior, the representative values of r f for BSA, MnO 2 colloids, and MnO 2 colloids in the presence of BSA deposited onto the three surfaces at different electrolyte concentrations are presented in Table S4. The values of r f for BSA were obtained, indicating that BSA could be absorbed onto the three surfaces, consistent with results reported before. − However, the simultaneous deposition of BSA was not the origin of the greater depositional behavior of MnO 2 colloids, supported by the higher value of | r f , MnO 2 colloids+BSA | than the value of | r f ,BSA |+| r f , MnO 2 colloids | when IS > 10 mM.…”

“…We attributed this observed enhancement of MnO 2 colloidal deposition in the presence of BSA to the effects of: (1) the attractive interactions generated fromthe adsorption of BSA on hydrophilic collector surfaces, , and (2) more effective colloid in the deposition system originated from less aggregation due to the high steric repulsion induced by BSA molecules. , Jeyachandran et.al showed that the relatively hydrophilic BSA can strongly adsorbed on hydrophilic collector surfaces (i.e., silica, magnetite and alumina) used in present study. , The absorption of BSA on the surfaces approaching/reaching saturation can generate attractive deposition sites for colloids, and therefore increased the deposition rate. Previous publications have proposed that the specific conformation of absorbed BSA on particulate colloids may alter the nature and magnitude of surface interaction forces exerted by a BSA molecule , and also exposed its attractive regions for particulate colloid deposition . In addition, BSA proteins have the strongest effect with respect to retarding the MnO 2 aggregation rate in the Na + solutions relative to HA and alginate due to the steric repulsion (Table S1).…”

“…63,64 The absorption of BSA on the surfaces approaching/reaching saturation can generate attractive deposition sites for colloids, 56 and therefore increased the deposition rate. Previous publications have proposed that the specific conformation of absorbed BSA on particulate colloids may alter the nature and magnitude of surface interaction forces exerted by a BSA molecule 54,65 and also exposed its attractive regions for particulate colloid deposition. 56 In addition, BSA proteins have the strongest effect with respect to retarding the MnO 2 aggregation rate in the Na + solutions relative to HA and alginate due to the steric repulsion (Table S1).…”