James A. Sawada

Anion-controlled pore size of titanium silicate molecular sieves.

Titanium silicate molecular sieves contain structural units that are fundamentally different from classical aluminosilicates. In addition to ordered octahedral titanium chains, members of the zorite family contain pentagonal titanium units which project into the main adsorption channels of the framework. We report that the effective pore size of these materials can be controlled by substituting halogens at the O7 sites that cap the pentagonal pyramids projecting into the channel. The quantity and type of halogen used determines the adsorptive properties of the molecular sieve. Barium exchange stabilizes these materials over a wide temperature range (nominally 200-400 degrees C). The barium-exchanged materials do not contract appreciably with calcination, as is observed in related Molecular Gate materials, and thus halogen content can control the pore size of the materials. This new approach to pore size control may have important implications for the purification of multiple classes of compounds, including light hydrocarbons and permanent gases.

A clinoptilolite-PDMS mixed-matrix membrane for high temperature water softening.

A mixed-matrix membrane composed of polydimethylsiloxane (PDMS) as the continuous phase and clinoptilolite, a naturally occurring zeolite, as the active phase has been used to decrease the conductivity of water by more than 80% across the membrane. Testing was carried out using a cross-flow configuration at temperatures as high as 160 °C using a constant transmembrane pressure of 8 bar. The simple fabrication method for the membrane, the durability of the system under the test conditions, and a suitable flux rate make such membranes promising candidates for industrial wastewater treatment.