Nanostructured SiO2 fibers by electrospinning

P.C. CARACCIOLO; N.S. INCHAURRONDO

CABA

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

Asociación Argentina de Ingenieros Químicos (AAIQ)

The preparation of mesoporous SiO2 nanofibers by the coupling of the sol-gel/EISA (evaporation-induced self-assembly method) synthesis with the electrospinning process is rare in literature, since it is a challenging work which requires a sophisticated control over a wide number of parameters. The aim of this study is to obtain a mesoporous nanostructured SiO2 membrane with high specific surface area and fibrous morphology for potential use as adsorbent or catalyst in water treatment. SiO2 is nontoxic and stable in solvents and its processing in the form of membranes allows the recovery and recycling of the material, lowering costs and secondary pollution problems. In this study the following procedure was followed: (1) Preparation of a homogeneous, spinnable sol-gel precursor, (2) Electrospinning under appropriate conditions (humidity (HR), temperature, distance to collector, voltage, flow), (3) Heat treatment: membranes were dried at 60ºC for 1 h and calcined at 550ºC (2ºC/min) for 3 hs. Pluronic P123 was employed as the structure-directing agent to generate ordered mesoporosity, TEOS as SiO2 precursor, ethanol as the common solvent, and poly(vinylpyrrolidone) (PVP) to increase the viscosity. H2O/HCl was added dropwise to initiate the 30 min-prehydrolysis at room temperature. Then, the hydrolysis/condensation reaction continued for 3 hs at 80ºC under reflux. The H2O:TEOS:HCl molar ratio was fixed at 2:1:0.01, which favors the formation of fibers. S8 showed the best results with a large BET surface area of 250 m2/g, type II isotherm with hysteresis loop H4, typical of slit-shaped pores. SEM images showed randomly arranged fibers in a nonwoven network. TEM images showed fibers with disordered, worm-like mesoporous structure. The interference of the electric field and the rapid solvent evaporation during electrospinning may have a negative effect on the formation of ordered mesoporous structures. In the absence of P123 membranes were less brittle and TEM images showed smooth non-porous fibers. Further work will be performed to: i) improve structural integrity and porosity; ii) dope with transition metals to test as a catalyst or adsorbent in water treatment.