Hollow Silica-Encapsulated TiO2 Functionalized with pH-Responsive Poly(acrylic acid) for Photocatalytic Degradation of Bisphenol A
DOI:
https://doi.org/10.11113/jomalisc.v4.108Keywords:
titania, core-shell, photocatalysis, pH-responsive, bisphenol AAbstract
Titania (TiO2) is widely recognized as a stable and non-toxic photocatalyst, yet its performance is restricted by a wide bandgap, rapid electron–hole recombination, and insensitivity to pH variations. Direct surface modification of TiO2 with polymers further complicates applications, as the strong oxidative activity of TiO2 can degrade organic components and compromise polymer stability. In this work, core–shell nanocomposites were engineered by encapsulating TiO2 within hollow silica shells and subsequently modifying the outer surface with pH-responsive poly(acrylic acid) (PAA), forming PAA/SiO2/void/TiO2. The nanocomposites were synthesized using monomer volumes of 0.7, 1.4, and 2.1 mL, denoted as (0.7)PAA/SiO2/void/TiO2, (1.4)PAA/SiO2/void/TiO2, and (2.1)PAA/SiO2/void/TiO2, respectively. Structural and chemical analyses confirmed the successful integration of all components. 1H NMR validated the PAA structure, while FTIR and TEM revealed characteristic bands and a distinct hollow core–shell morphology with uniform TiO2 encapsulation and a stable SiO2 framework, though the PAA layer was not visible due to its organic nature. UV–vis–NIR spectroscopy revealed a bandgap of 3.6 eV, attributed to the hybrid framework. Although substantially higher activity was expected with the addition of PAA, the degradation of bisphenol A (BPA) remained relatively low. The (0.7)PAA/SiO2/void/TiO2 achieved 16% degradation under UV and 7.5% under visible light, while higher PAA loadings further reduced activity due to excessive surface coverage. Despite the lower activity, the photocatalyst exhibited pH-responsive behavior, with BPA degradation increasing from 4.4% at pH 5 to 7.5% governed by the surface functionality of PAA. These findings highlight the potential of PAA/SiO2/void/TiO2 as pH-responsive photocatalysts for emerging contaminant degradation.
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