ERI: Solubility-Boosting Effect of Lattice Impurities in Anisotropic Crystals

Rowan University, Glassboro NJ

Investigators

Abstract

Understanding particle solubility is critical for the design of industrial crystallizers, semiconductor manufacturing operations, and separation processes such as reverse osmosis desalination, where unwanted scaling is an operational challenge. It is an important design consideration in the synthesis of pharmaceuticals where control of solubility is required for optimal drug delivery. The lack of solubility control also can be a limiting factor in the formulation of food products and diet supplements. Past studies of the solubility of crystalline materials have focused on the effects of crystal lattice structure and liquid composition on solubility. These studies have largely ignored the role composition variations within individual crystals play in solubility, likely due to the difficulty of measuring these variations. This project will investigate whether compositional variations within a crystal can result in different solubilities among the crystal facets, resulting in uneven growth or dissolution within individual crystals. The research will challenge current models of crystal growth and dissolution processes and will produce new insights into how impurities are released from crystalline materials, creating new routes to extracting potentially toxic impurities from pharmaceutical products. The project will contribute to the education of ten to twenty undergraduate students and one Ph.D. student, who will gain hands-on experience with crystallization processes and analysis of crystalline materials, a skillset valued in the pharmaceutical industry but rarely found in graduates joining the U.S. workforce. This project presents a new approach to studying the effect of lattice-incorporated impurities on crystal solubility. The proposal is based on the premise that crystals can exhibit differing degrees of composition anisotropy, with certain regions being entirely responsible for hosting impurities. This motivates the research plan to investigate the effect that lattice impurities have on crystal form stability and solubility, that these properties should be studied with respect to individual crystal facets and not on powders (of crystals) as a whole. This project sets out to prove the hypothesis that a single crystal may present multiple solubility values across its lattice, and that those differences can be leveraged in the design of novel impurity separation strategies. This research project is divided in two research aims. In Aim 1, research will concentrate on characterizing anisotropy of impurities within single crystals and investigating how impurity gradients affect dissolution and growth. Aim 2 will then expand to the study of crystal suspension aging dynamics by investigating how coexisting pure and impure lattices affect the dissolution and growth behaviors during suspension aging. The research will make use of model anisotropic systems with transparent solutes and opaque impurities, where the presence and extent of anisotropy can be easily studied. The proposed research is integrated with an education plan that will provide undergraduate and graduate students with specialized skills in separation processes and materials science, as well as with experience working in multidisciplinary teams. The undergraduate students will be divided into two groups, aligned with the two Aims of the research proposal, resulting in an effective mechanism for integrating the PI’s research and education efforts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.