Efficient degradation of organic pollutants by novel titanium dioxide coupled bismuth oxide nanocomposite: Green synthesis, kinetics and photoactivity.

Herein, a green and facile methodology was used for the structural design of semiconductor nanomaterials and employed as efficient photocatalyst to resolve the environmental issues of water pollutants. Titanium oxide coupled with bismuth oxide (TiO2@Bi2O3) nanocomposite was synthesized by employing the seed extract of Sapindus mukorossi (commonly found plant in India) and subsequently used for the elimination of toxic, and persistence industrial pollutants namely bisphenol A (BPA) and methylene blue (MB). Microscopic and spectroscopic techniques revealed particle size of synthesized nanocomposite found less than 50 nm along with high crystallinity. Appearance of stretching vibrations at 459 cm-1 for Bi-O-Ti in the IR spectra of nanocomposite has established the coupling of TiO2 with Bi2O3. The parameters of degradation were optimized by varying the pollutant concentration, catalytic amount and pH in the presence of natural sunlight. The nanocomposite TiO2@Bi2O3 showed maximum degradation (MB: 94% and BPA: 91%) at a minimum concentration of pollutant (50 mgL-1) with catalyst amount (35 mg), neutral pH and reduces half-life of pollutants (BPA: 1h, MB: 0.5h). Owing of higher surface area (80 m2g-1), lower band gap (2.5 eV), and more negative zeta potential value (-40.3 mV) results into excellent photocatalytic properties. The breakage of S-N conjugated system in MB results into rapid degradation as compare to BPA. The degradation followed first-order kinetics and Langmuir adsorption in both the cases. Presence of active radicals during the photocatalysis process was responsible for quick degradation and strongly supported by scavenger analysis. GC-MS analysis revealed the degradation of toxic pollutants into safer metabolites and finally mineralized. Multiple times (n = 8) reusability of green photocatalyst advocated sustainability and appropriate for industrial applications.

Activated carbon modified titanium dioxide/bismuth trioxide adsorbent: One-pot synthesis, high removal efficiency of organic pollutants, and good recyclability.

Considerable endeavors have focused on tightly combining adsorption with photocatalysis in designing composite materials for environmental pollution treatment. Recent advances in coupling titanium dioxide/bismuth trioxide (TiO2/Bi2O3) with activated carbon (AC) show significantly enhanced photocatalytic performance but face critical limitations including low adsorption capacity and multi-step synthesis. In this work, we introduce a one-pot synthesis of activated carbon modified TiO2/Bi2O3 composite materials (TiO2/Bi2O3/AC). Thanks to the integrated adsorbent/photocatalyst system, TiO2/Bi2O3/AC shows a drastically enhanced removal efficiency for sulfamethazine (>81%), far beyond the corresponding value of the reported AC/TiO2/Bi2O3 adsorbent (<40%). Notably, the removal rates of other typical pollutants including tetracyclines, methyl orange, and rhodamine B are as high as >98%. Furthermore, TiO2/Bi2O3/AC obtains >80% of its adsorption rate for the fifth cycle after simple photo-regeneration without any other post-treatments. Kinetic analysis and photoelectric characterization are carried out to provide insight into adsorption mechanism. Therefore, this work demonstrates a considerable potential to design and construct other multifunctional adsorbents with advanced performance.

Synthesis and Evaluation of Properties of an Additive Based on Bismuth Titanates for Cement Systems.

The development of modern building materials science involves the process of designing innovative materials that exhibit unique characteristics, such as energy efficiency, environmental friendliness, self-healing ability, and photocatalytic properties. This can be achieved by modifying cement with nano- and fine-dispersed additives that can give the material new properties. Such additives include a number of compounds based on the TiO2-Bi2O3 system. These compounds have photocatalytic activity in the near-UV and visible range of the spectrum, which can serve to create photocatalytic concretes. Here, the purpose of this scientific study was to synthesize compounds based on the TiO2-Bi2O3 system using two methods in order to identify the most optimal variant for creating a composite material and determine its properties. Within the framework of this article, two methods of obtaining a photocatalytically active additive based on the TiO2-Bi2O3 system are considered: the solid-state and citrate-based methods. The photocatalytic, mechanical and structural properties of composites containing the synthesized additive are investigated. In this study, it was found that for the creation of photocatalytic concretes, it is advisable to use cement compositions with a bismuth titanate content of 3-10 wt.%. of the cement content, regardless of the method of obtaining the additive. However, the most optimal composition is one containing 5 wt.% of the synthesized additive. It is noted that compositions containing 5% by weight of bismuth titanate demonstrate photocatalytic activity and also show an increase in strength on the first day of hardening by 10% for the solid-state method and 16% for the citrate method.

Dimensional-matched two dimensional/two dimensional TiO2/Bi2O3 step-scheme heterojunction for boosted photocatalytic performance of sterilization and water splitting.

A Step-scheme (S-scheme) heterojunction can regulate the directional migration of powerful photogenerated carriers and realize high photocatalytic activity. Herein, we propose a novel dimensional matched S-scheme photocatalyst comprising of two-dimensional (2D) TiO2 nanosheets and 2D Bi2O3 nanosheets for environmental and energy applications, such as water sterilization and water splitting. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance, in-situ irradiated XPS and theoretical calculations provided strong evidence that the photocarrier migration in the TiO2/Bi2O3 composite followed the S-scheme mode, which efficiently prevented the recombination of powerful photocarriers, thereby enabling the heterojunction with a strong redox ability for producing abundant reactive oxygen species. The tight and large 2D/2D interface minimized the distance of photocarrier migration to further extend the lifetime of useful photocarriers (active radicals for sterilization and photoelectrons for H2 generation). The 2D/2D TiO2/Bi2O3 heterojunction demonstrated an improved photocatalytic antibacterial performance with complete inactivation of 4.63 × 107 CFU mL-1Escherichia coli cells within 6 h in water. In addition, the heterojunction displayed a H2 generation rate of 12.08 mmol h-1g-1 through water splitting process. This study provides a potential bifunctional photocatalyst for minimizing the adverse impact of pollution on the environment.