Organosilane Surface Treatment of Nanostructured Aggregates for Biofuel and Bioproduct Extraction

Within the past few decades the use of silica nanoparticles in medical applications has become increasingly widespread. Correspondingly, their application in fields such as electronics and energy has seen recent emerging growth. This study offers a preliminary experimental approach for the production and characterization of the efficiency of organosilane functionalized silica nanoparticle aggregates for their applications in energy production processes, with special regard to biofuel separations of isoprenoid-alcohols in photobioreactors. The production of the nanostructured aggregates occurred via a vapor-phase polymerization reaction. For each reaction that took place, two monomers were used. One of the monomers, an aromatic silane, remained constant while the second varied in chemical composition and was added at much reduced levels. The variable monomers used include alkyl silanes with carbon chains ranging from C8 to C18 in length. The reaction was allowed to take place over a 48 hr period and the resulting solids were washed in a shaker plate for ~ 5 hr to remove any unreacted monomer still on the surface. Adsorption/desorption cycling of the particles occurred after a preconditioning treatment with farnesol as the target molecule. Cycling consisted of additions of aliquots of farnesol to the nanostructured aggregates until saturation was achieved.  Desorbed oil was collected after applying pressures on the order of 50-100 psi.  It was found that the longer the chain length of the second monomer added to the reaction, the more farnesol that was needed for particle preconditioning. Additionally, it was found that only the aggregates made using the monomers with the octyl and decyl hydrocarbon chain lengths had successful cycling for up to 8 rounds with a consistent recovery of desorbed oil for the last four cycles. The aggregates made using longer alkyl chains, dodecyl and octadecyl precursors, were found to form gels with the particles after saturation and thus would not be recommended for use for farnesol extraction. As a result, the particles co-coated with either octyl or decyl-silanes are viable candidates for use in the extraction of farnesol produced within a photobioreactor.