Simultaneous adsorption/photo catalytic degradation of turquoise blue dye by silk fibroin—TiO2-based bio-composite under visible light irradiation

Abstract

In this study, a bio-composite composed of TiO₂-incorporated bio-silica (BS), silk fibroin (SF), and polyurethane foam (PUF) was developed and evaluated as a photocatalytic material for the removal of Turquoise Blue (TB) dye. The prepared bio-composite was analyzed for its formation, surface morphology, and thermal properties using FTIR, XRD, TGA, and SEM, respectively. The amorphous nature of the composite was clearly revealed through XRD and SEM studies. Initially, the composite adsorbed a substantial amount of the dye on its surface in the dark, after which it underwent photocatalysis under light exposure. The photodegradation efficiency of the BS/SF/PUF/TiO₂ bio-composite for TB was assessed, and the results showed a significant enhancement in the photocatalytic degradation of TB compared to pure TiO₂. The degradation efficiency of BS/SF/PUF/TiO₂ reached approximately 99.96%. The high electron–hole charge separation capability was the driving force behind the consistent bandgap, which contributed to the exceptional photodegradation efficiency of the bio-composite. The bandgap of the BS/SF/PUF/TiO₂ bio-composite was determined to be 2.9 eV. The photodegradation efficiency was evaluated by varying parameters such as pH, irradiation time, catalyst dosage, and initial dye concentration. The experimental data were fitted to the Langmuir–Hinshelwood model to analyze the rate constant and explore the possible photocatalytic mechanism. This study demonstrates that the BS/SF/PUF/TiO₂ bio-composite holds significant potential as both an adsorbent and a photocatalyst for wastewater treatment, with the added advantage of being easily reusable.