Immobilization of Titanium(IV) Oxide onto 3D Spongin Scaffolds of Marine Sponge Origin According to Extreme Biomimetics Principles for Removal of C.I. Basic Blue 9

Abstract

The aim of extreme biomimetics is to design a bridge between extreme biomineralization and bioinspired materials chemistry, where the basic principle is to exploit chemically and thermally stable, renewable biopolymers for the development of the next generation of biologically inspired advanced and functional composite materials. This study reports for the first time the use of proteinaceous spongin-based scaffolds isolated from marine demosponge Hippospongia communis as a three-dimensional (3D) template for the hydrothermal deposition of crystalline titanium dioxide. Scanning electron microscopy (SEM) assisted with energy dispersive X-ray spectroscopy (EDS) mapping, low temperature nitrogen sorption, thermogravimetric (TG) analysis, X-ray diffraction spectroscopy (XRD), and attenuated total reflectance⁻Fourier transform infrared (ATR⁻FTIR) spectroscopy are used as characterization techniques. It was found that, after hydrothermal treatment crystalline titania in anatase form is obtained, which forms a coating around spongin microfibers through interaction with negatively charged functional groups of the structural protein as well as via hydrogen bonding. The material was tested as a potential heterogeneous photocatalyst for removal of C.I. Basic Blue 9 dye under UV irradiation. The obtained 3D composite material shows a high efficiency of dye removal through both adsorption and photocatalysis.

Keywords: extreme biomimetics; hydrothermal synthesis; marine sponges; photocatalysis; scaffolds; spongin; titanium dioxide.

Figure 1

Mineral- and pigment-free three-dimensional spongin scaffolds isolated from Hippospongia communis demosponge.

Figure 2

Scanning electron microscopy (SEM) images. (a,b) Spongin fibers before the hydrothermal treatment in titanium(IV) butoxide (TBOT); (c,d) TiO₂ immobilized onto spongin (SpI–TiO₂) obtained through hydrothermal synthesis; (e) local energy dispersive X-ray spectroscopy (EDS) measurements. The structure remains stable even after 1 h of ultrasonic treatment.

Figure 3

N₂ adsorption/desorption isotherms of obtained materials. A_BET: Specific surface area; S_p: Mean pore diameter; V_p: Total pore volume; STP: Standard temperature and pressure.

Figure 4

Thermogravimetric (TG) curves of spongin and SpI–TiO₂ composite, showing the mass loss of samples during heating.

Figure 5

X-ray diffraction (XRD) patterns of SpI–TiO₂ composite accompanied by reference peaks characteristic of anatase and compared with a pattern recorded for purified spongin scaffold.

Figure 6

The attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectra of spongin, titania (reference sample, anatase), and SpI–TiO₂ composite obtained via hydrothermal synthesis, presented as spectra in two ranges: (a) in wavenumber range 4000–2500 cm⁻¹, and (b) in range of 2000–400 cm⁻¹.

Figure 7

Proposed mechanism of titanium dioxide immobilization onto spongin fibers involving hydrogen bonding and electrostatic interactions.

Figure 8

Photodegradation efficiency of C.I. Basic Blue 9 using (a) TiO₂ particles dispersed in the solution and (b) TiO₂ immobilized on spongin scaffolds presented as a function of quotient of dye concentration at time t (C_t) and the initial dye concentration (C₀) versus irradiation time.