Imogolite and allophane are nanosized aluminosilicates with high value in industrial and technological applications, however it remains unclear what factors control their formation and abundance in nature and in the lab. This work investigated the complex system of physical and chemical conditions that influence the multi-stage formation of these nanominerals. Samples were synthesized and analyzed by powder x-ray diffraction, <i>in situ </i>and <i>ex situ</i> small angle x-ray scattering, and high-resolution transmission electron microscopy. Multivariate regression analysis combined with linear combination fitting of diffraction data was used to model the influence of different synthesis conditions including concentration, hydrolysis ratio and rate, and aluminum-to-silicon elemental ratio on the particle size of the initial precipitate and on the phase abundances of the final products. The developed models describe how increasing initial Al:Si ratio, particle size, and hydrolysis ratio increased the proportion of imogolite produced, while increasing the concentration of starting reagents decreased the final proportion. The model confidences were &gt;99%, and explained 86 to 98% of the data variance.  It was determined from the models that hydrolysis ratio was the strongest control on the final phase composition. The models also were able to consistently predict experimentally derived results from other studies. These results demonstrated the ability to use this approach to understand complex geochemical systems with competing influences, as well as provided insight into the formation of imogolite and allophane, which are precursors to hydrous smectite and other more crystalline clay minerals.

Multivariate analysis of factors regulating the formation of synthetic allophane and imogolite nanoparticles

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.