TiO2-Powdered Activated Carbon (TiO2/PAC) for Removal and Photocatalytic Properties of 2-Methylisoborneol (2-MIB) in Water

Spirulina-based carbon materials as adsorbents for drinking water taste and odor control: Removal efficiency and assessment of cyto-genotoxic effects

The sensory quality of drinking water, and particularly its taste and odor (T&O) is a key determinant of consumer acceptability, as consumers evaluate water by their senses. Some of the conventional treatment processes to control compounds which impart unpleasant T&O have limitations because of their low efficiency and/or high costs. Therefore, there is a great need to develop an effective process for removing T&O compounds without secondary concerns. The primary objective of this study was to assess for the first time the effectiveness of spirulina-based carbon materials in removing geosmin (GSM) and 2-methylisoborneol (2-MIB) from water, two commonly occurring natural T&O compounds. The efficiency of the materials to remove environmentally relevant concentrations of GSM and 2-MIB (ng L-1) from ultrapure and raw water was investigated using a sensitive headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC/MS) method. Moreover, the genotoxic and cytotoxic effects of the spirulina-based materials were assessed for the first time to evaluate their safety and their potential in the treatment of water for human consumption. Based on the results, spirulina-based materials were found to be promising for drinking water treatment applications, as they did not exert geno-cytotoxic effects on human cells, while presenting high efficiency in removing GSM and 2-MIB from water.

TiO2/Karaya Composite for Photoinactivation of Bacteria

TiO₂/Karaya composite was synthesized by the sol-gel method for the photoinactivation of pathogens. This is the first time that we have reported this composite for an antimicrobial approach. The structure, morphology, and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance, and the surface area was characterized by the BET method. The XRD and EDS results showed that the TiO₂/Karaya composite was successfully stabilized by the crystal structure and pore diameter distribution, indicating a composite of mesoporous nature. Furthermore, antibacterial experiments showed that the TiO₂/Karaya composite under light was able to photoinactivate bacteria. Therefore, the composite is a promising candidate for inhibiting the growth of bacteria.

Coconut Fiber Decorated with Bismuth Vanadate for Enhanced Photocatalytic Activity

Bismuth vanadate/coconut fiber (BiVO₄/CF) composites were synthesized by coprecipitation and calcination methods. All catalysts used in this work were prepared by a simple coprecipitation method and fully characterized by means of XRD, SEM-EDS, PL, BET N₂ adsorption, zeta potential, and UV-vis DRS. Degradation of indigo carmine (IC) under visible light irradiation was tracked by the UV-vis technique. It was documented that XRD patterns of BiVO₄ and BiVO₄/CF samples retained the monoclinic structure. From SEM, the CF sheets were visualized, covering the surface of BiVO₄ particles. The specific surface area of the synthesized catalysts increased from 1.77 to 24.82 m²/g. The shift of absorption edge to a longer wavelength corresponded to a decrease in band gap energy from 2.3 to 2.2 eV. The photocatalytic degradation rate of the BiVO₄/CF composite was five times higher than that of pristine BiVO₄. Moreover, the photocatalyst can be separated and recycled with little change after the third times recycling. The improved activity of the composite resulted from the combination of the adsorption performance of the substrate CF and the photocatalytic activity of BiVO₄. In addition, the position of the specific mechanism could occur via both the active species of superoxide radical and hydroxyl radical.