Shape and orientation of bare silica particles influence their deposition under intermediate ionic strength: A study with QCM–D and DLVO theory

Authors: GOMEZ-FLORES, ALLAN - Chonbuk National University; Bradford, Scott; HWANG, GUKHWA - Chonbuk National University; CHOI, SOWON - Chonbuk National University; TONG, MEIPING - Peking University; KIM, HYUNJUNG - Chonbuk National University

Submitted to: Colloids and Surfaces A: Physicochemical and Engineering Aspects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2020
Publication Date: 4/28/2020
Citation: Gomez-Flores, A., Bradford, S.A., Hwang, G., Choi, S., Tong, M., Kim, H. 2020. Shape and orientation of bare silica particles influence their deposition under intermediate ionic strength: A study with QCM–D and DLVO theory. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 599. https://doi.org/10.1016/j.colsurfa.2020.124921.
DOI: https://doi.org/10.1016/j.colsurfa.2020.124921

Interpretive Summary: The interaction of non-spherical microorganisms and engineered particles with surfaces is important for many environmental and industrial applications, but the role of particle shape has not yet been fully evaluated. This research experimentally and theoretically compared the interaction of spherical and bullet shaped silica particles of similar size under several different solution chemistries. Bullet shaped silica particles exhibited retention on quartz surfaces over a wider range of solution ionic strengths than spherical particles. Theoretical calculations that accounted for the particle shape were consistent with these observations, and results indicate that particle shape and orientation with the surface are important considerations under intermediate ionic strength conditions. These results will be of interest to scientists and engineers that are concerned with predicting the environmental fate of non-spherical particles like bacteria and viruses, as well as their use in industry.

Technical Abstract: Theory developed by Derjaguin, Landau, Verwey, and Overbeek (DLVO) is commonly used to interpret and predict the deposition of particles, but it was originally simplified for spherical particles. Many types of bacteria and particles in nature are not spherical. Previous literature has experimentally shown that particle shape has an effect on drug delivery, retention in porous media, self-assembly, and flotation, but the quantitative interpretation of these results has been hindered by experimental (e.g., uniform rod shaped particles and flow fields at controlled chemistries) and theoretical (e.g., consideration of rod shape particles with different surface orientations) challenges. For example, the deposition of ellipsoidal polystyrene particles has been investigated in the presence of non-DLVO interactions, due to residual poly(vinyl) alcohol, hindering the effect of shape. In our study, bare spherical and bullet-like silica particles of well-defined surface chemistry were used for deposition tests on bare silica surfaces using a Quartz Crystal Microbalance with Dissipation (QCM–D) over six ionic strengths (IS). At the same time, the DLVO theory was modified to consider particle shape and orientation of deposition. We found that particle shape had an effect on deposition at intermediate IS. A modified DLVO approach was able to interpret the deposition of bullet-like silica particles. Specifically, bullet-like silica particles of certain aspect ratio may find angles that minimize repulsive energies and overcome energy barriers so that deposition on the silica surfaces is energetically favorable. Therefore, there are conditions of water chemistry where particle shape and orientation cannot be ignored and their deposition must be systematically investigated.