Abstracts Category : Other

3D Hierarchically-Structured Twinned Alumina Nanosheets for Filtration and Catalysis

by Katrina Roebuck

Currently, complex nanostructures can be synthesized in two distinct forms: non-porous aggregates that maintain their structure when subject to external pressure but have poor flow characteristics, and highly porous particles or particle aggregates that are permeable to flow but collapse and stack under external pressure. The development of support materials for filtration and catalysis that maintain high throughput, resist fouling, and maintain high internal pore accessibility are therefore of great interest. In this work, our primary objective was to synthesize a nanostructure by self-assembling nanoplatelets in a hierarchical structure. We sought to develop a material that in filtration would be highly permeable to flow, and maintain its structure when subject to external pressure. As a catalyst, we desired a material that provided easy access of reactants to its internal structure, and release of products to the bulk media in order to improve the catalyst specificity. We successfully synthesized this material and determined that the concentrations of ethanol and surfactant in the synthesis mixture controlled the morphology of the nanoparticles in the hierarchically-structured material (HSM).We compared the performance of our HSM to commonly-used filtration aids during the filtration of a colloidal solution. Our HSM rapidly reduced the turbidity of the colloidal solution to <0.10 NTU at a flux that was up to 28 times higher than the fluxes obtained by the commonly-used filtration aids. Subsequently, we developed a protocol to immobilize lipase from crude porcine pancreas (cPPL), Candida rugosa (CRL), and Candida antarctica (CALB) onto the support material. We assessed the specific hydrolytic activities of immobilized crude porcine pancreas and Candida rugosa to determine the optimum synthesis conditions to produce the most effective HSM support. We determined that synthesizing our HSM in 50 vol% ethanol-water followed by a 24 h epoxysilane treatment process produced particles with the highest lipase immobilized and retained (16.7 + 0.2 mg cPPL / g support and 39.7 + 0.9 mg CRL / g support). Extended silylation of the supports beyond 24 h was found to not significantly increase enzyme immobilization. Finally, we assessed the performance of immobilized CALB on our support material in a batch reactor for the reduction of free fatty acids (FFA) in acidic oil. The immobilized enzyme produced in this work rapidly reduced the FFA content during the initial 2 to 4 h of each run and maintained the FFA content below 0.50 wt% for up to 56 h even after being reused 5 times. CALB immobilized on TAN showed high reusability with no observable reduction in immobilized catalyst activity.Les nanostructures complexes peuvent tre synthtises sous deux formes distinctes: des agrgats non poreux qui maintiennent leur structure lorsquelles sont soumises une pression externe, et des particules fortement poreuses ou des agrgats de particules permables l'coulement, mais qui s'effondrent et sempilent sous une pression