PNNL

Artwork highlighting collaborative research conducted by PNNL and the University of Houston was featured on the cover of the November 2016 issue of Chemistry, a Wiley journal publication.

PNNL nanomaterial scientists Radha Motkuri and Pete McGrail supported the cover-worthy research project led by the University of Houston (UH) and funded by the National Science Foundation and the Welch Foundation (for UH) and the DOE Office of Energy Efficiency and Renewable Energy (for PNNL).

The cover image highlights the hierarchical nature of the research that spanned multiple scales—from studying the adhesion of atoms, ions, or molecules to a solid surface that are visible to the naked eye, to characterizing microscopic materials to determine their basic material structures and properties, and to describing molecular systems at the atom level.

The Research Represented by the Art

Zeolites are three-dimensional structures that form identical-sized pores. These pores act as sieves, adsorbing molecules that fit snugly within them and excluding those that are too big. This process can be used in separation or adsorption technologies in industry. More specifically, designing tunable zeolites with structure-varying properties can substantially affect their performance in commercial applications, said Prof. Rimer at UH.

The aluminosilicate gismondine (GIS) is a small-pore zeolite whose framework features reported activity for catalytic processes. GIS has proven to be an excellent material for ion-exchange applications, such as water softening in detergents, and has been identified as one of the most promising zeolite adsorbents.

"It is crucial that we develop versatile platforms for tailoring the properties of these zeolites using organic-free (commercially viable) approaches, while simultaneously controlling zeolite formation," said Motkuri, a nanomaterial scientist at PNNL.

The PNNL and University of Houston research team investigated synthetic methods of producing two aluminosilicate polymorphs (a solid that exists in more than one form or structure) of GIS. The team studied GIS crystallization to determine if the synthesis crystals were isostructural, meaning they have the same structure but not necessarily the same cell dimensions or same chemical composition. Thermal stability tests revealed clear differences in the structural integrity of the two GIS polymorphs. These differences may provide distinct advantages in selective adsorption of water over other gases in separations, ion exchange, and catalysis applications. The study found that controlling conditions that produce these zeolites can lead to materials that have improved properties for a diverse range of commercial processes. Processes benefitting from the selective separation of small molecules include those involving water removal (such as dehumidification in air-conditioning systems), because the small pores mean only water and no other molecules can enter into the zeolites. Other processes include the removal and recovery of organic contaminants from industrial wastewaters, gas streams, and groundwater; control of greenhouse gases; flue gas treatment; recovery of ozone-depleting chlorofluorocarbons; reduction of gas emissions; clean fuel production; and decontamination of polluted water and soil.