Environmentally Benign Synthesis of Alumina Based Ceramics

Researchers: Maria Fidalgo-Cortalezzi, Diane Bailey, Jerome Rose

Cross-section of a templated membrane.We have developed in collaboration with researchers in Andrew Barron's group in the Chemistry Department at Rice University an environmentally benign chemical process for producing alumina based ceramics. The focus of work to being conducted in our group is on developing and characterizing an entirely new class of ceramic membranes based on alumoxane chemistry for applications in environmental separations. Ceramic membranes are promising in applications such as treating hazardous and industrial wastes, or recovering materials during chemical production that may, due the presence of solvents or high temperatures, destroy conventional polymeric membranes. The alumoxane membranes being developed at Rice avoid the use volatile organic chemicals in membrane fabrication, reduce costs, and improve energy efficiency.

The scope of the project includes fundamental research into aqueous processing of alumina-precursors and their processing into a membrane film with desirable characteristics of thickness, pore size distribution, permeability, and surface chemistry. We hope to exploit the properties of various alumoxanes to produce membranes with a range of effective pore sizes or cutoffs and cast these materials on suitable porous supports.

We have successfully shown that the alumoxane pathway can be manipulated to produce ceramics with narrow pore size distributions. The mean of these distributions can be currently controlled within the range of approximately 10 to 50 nm. Of particular interest is the fact that mean pore sizes readily achievable by this approach are considerably smaller than those obtainable for alumina-based ceramics produced from the sol-gel method. It appears to be possible to produce membranes in the nanofiltration range without resorting to the use of zirconia- or titania-based ceramics as required to produce pores of similary small size when using the sol-gel method.

Application of the alumoxane-based approach to creating ceramic membranes will ieliminate the use of toxic solvents and reduce energy consumption. Byproducts formed from the combustion of plasticizers and binders will be minimized, and the use of acids eliminated. Thus, the process will reduce the potential for environmental release through the use of more environmentally benign feedstocks and an alternative synthetic procedure which will improve energy efficiency.

Also, due to the very versatile nature of the process, the proposed alumoxane process holds the potential for fabricating new ceramic nanofiltration and ultrafiltration membranes with enhanced specificity. Due to their stability under exposure to high temperatures, organic solvents, and oxidants, ceramic membranes are particularly well suited to separations required in less environmentally benign industrial processes in which options for pollution prevention must focus on materials recovery and reuse in the absence of suitable alternative processes.