RESUMO
This study explores the use of silica-coated bacterial nanocellulose (BC) scaffolds with bulk macroscopic yet nanometric internal pores/structures as functional supports for high surface area titania aerogel photocatalysts to design flexible, self-standing, porous, and recyclable BC@SiO2-TiO2 hybrid organic-inorganic aerogel membranes for effective in-flow photo-assisted removal of organic pollutants. The hybrid aerogels were prepared by sequential sol-gel deposition of the SiO2 layer over BC, followed by coating of the resulting BC@SiO2 membranes with a porous titania aerogel overlayer of high surface area using epoxide-driven gelation, hydrothermal crystallization, and subsequent supercritical drying. The silica interlayer between the nanocellulose biopolymer scaffold and the titania photocatalyst was found to greatly influence the structure and composition, particularly the TiO2 loading, of the prepared hybrid aerogel membranes, allowing the development of photochemically stable aerogel materials with increased surface area/pore volume and higher photocatalytic activity. The optimized BC@SiO2-TiO2 hybrid aerogel showed up to 12 times faster in-flow photocatalytic removal of methylene blue dye from aqueous solution in comparison with bare BC/TiO2 aerogels and outperformed most of the supported-titania materials reported earlier. Moreover, the developed hybrid aerogels were successfully employed to remove sertraline drug, a model emergent contaminant, from aqueous solution, thus further demonstrating their potential for water purification.
Assuntos
Dióxido de Silício , Titânio , Dióxido de Silício/química , Titânio/química , Biopolímeros/química , Água/químicaRESUMO
To address the problems associated with the use of unsupported nanomaterials, in general, and molybdenum disulfide (MoS2), in particular, we report the preparation of self-supported hybrid aerogel membranes that combine the mechanical stability and excellent textural properties of bacterial nanocellulose (BC)-based organic macro/mesoporous scaffolds with the excellent adsorption-cum-photocatalytic properties and high contaminant removal performance of MoS2 nanostructures. A controlled hydrothermal growth and precise tuning of the synthetic parameters allowed us to obtain BC/MoS2-based porous, self-supported, and stable hybrid aerogels with a unique morphology resulting from a molecular precision in the coating of quantum-confined photocatalytic MoS2 nanostructures (2-4 nm crystallite size) on BC nanofibrils. These BC/MoS2 samples exhibit high surface area (97-137 m2·g-1) and pore volume (0.28-0.36 cm3·g-1) and controlled interlayer distances (0.62-1.05 nm) in the MoS2 nanostructures. Modification of BC with nanostructured MoS2 led to an enhanced pollutants removal efficiency of the hybrid aerogels both by adsorptive and photocatalytic mechanisms, as indicated by a detailed study using a specifically designed membrane photoreactor containing the developed photoactive/adsorptive BC/MoS2 hybrid membranes. Most importantly, the prepared BC/MoS2 aerogel membranes showed high performance in the photoassisted in-flow removal of both organic dye (methylene blue (MB)) molecules (96% removal within 120 min, Kobs = 0.0267 min-1) and heavy metal ions (88% Cr(VI) removal within 120 min, Kobs = 0.0012 min-1), separately and/or simultaneously, under UV-visible light illumination as well as excellent recyclability and photostability. Samples with interlayer expanded MoS2 nanostructures were particularly more efficient in the removal of smaller species (CrO42-) as compared to larger (MB) dye molecules. The prepared hybrid aerogel membranes show promising behavior for application in in-flow water purification, representing a significant advancement in the use of self-supported aerogel membranes for photocatalytic applications in liquid media.