Photoactive polymer–nanoclay hybrid photosensitizer for oxidation of phenol in aqueous media with the visible light

Heterogeneous photosensitization for water reuse in cellars: evaluation of silica, spongin, and chitosan as carrier material

Photosensitization, a powerful oxidation reaction, offers significant potential for wastewater treatment in the context of industrial process water reuse. This environmentally friendly process can be crucial in reducing water consumption and industrial pollution. The ultimate goal is to complete process water reuse, creating a closed-loop system that preserves the inherent value of water resources. The photosensitized oxidation reaction hinges on three essential components: the photosensitizer, visible light, and oxygen. In this study, we assess the performance of three distinct materials-silica, chitosan, and spongin-as carrier materials for incorporating the phthalocyanine photosensitizer (ZnPcS4) in the heterogenous photosensitization process. Among the three materials under study, chitosan emerged as the standout performer in reactor hydrodynamic performance. In the photooxidation process, the photosensitizer ZnPcS4 exhibited notable efficacy, resulting in a significant reduction of approximately 20 to 30% in the remaining COD concentration of the cellar wastewater. Chitosan demonstrated exceptional hydrodynamic characteristics and displayed a favorable response to pH adjustments within the range of 8 to 10, outperforming the other two carrier materials. To further enhance the efficiency of continuous operation, exploring methods for mitigating photosensitizer bleaching within the reaction medium and investigating the impact of different pH values on the process optimization would be prudent.

Water-Soluble Non-Ionic PEGylated Porphyrins: A Versatile Category of Dyes for Basic Science and Applications

This review arises from the need to rationalize the huge amount of information on the structural and spectroscopic properties of a peculiar class of porphyrin derivatives-the non-ionic PEGylated porphyrins-collected during almost two decades of research. The lack of charged groups in the molecular architecture of these porphyrin derivatives is the leitmotif of the work and plays an outstanding role in highlighting those interactions between porphyrins, or between porphyrins and target molecules (e.g., hydrophobic-, hydrogen bond related-, and coordination-interactions, to name just a few) that are often masked by stronger electrostatic contributions. In addition, it is exactly these weaker interactions between porphyrins that make the aggregated forms more prone to couple efficiently with external perturbative fields like weak hydrodynamic vortexes or temperature gradients. In the absence of charge, solubility in water is very often achieved by covalent functionalization of the porphyrin ring with polyethylene glycol chains. Various modifications, including of chain length or the number of chains, the presence of a metal atom in the porphyrin core, or having two or more porphyrin rings in the molecular architecture, result in a wide range of properties. These encompass self-assembly with different aggregate morphology, molecular recognition of biomolecules, and different photophysical responses, which can be translated into numerous promising applications in the sensing and biomedical field, based on turn-on/turn-off fluorescence and on photogeneration of radical species.

Photoelectrochemical performance of birnessite films and photoelectrocatalytic activity toward oxidation of phenol

Birnessite films on fluorine-doped tin oxide (FTO) coated glass were prepared by cathodic reduction of aqueous KMnO₄. The deposited birnessite films were characterized with X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The photoelectrochemical activity of birnessite films was investigated and a remarkable photocurrent in response to visible light was observed in the presence of phenol, resulting from localized manganese d-d transitions. Based on this result, the photoelectrocatalytic oxidation of phenol was investigated. Compared with phenol degradation by the electrochemical oxidation process or photocatalysis separately, a synergetic photoelectrocatalytic degradation effect was observed in the presence of the birnessite film coated FTO electrode. Photoelectrocatalytic degradation ratios were influenced by film thickness and initial phenol concentrations. Phenol degradation with the thinnest birnessite film and initial phenol concentration of 10mg/L showed the highest efficiency of 91.4% after 8hr. Meanwhile, the kinetics of phenol removal was fit well by the pseudofirst-order kinetic model.

Efficient photocatalytic oxidation of benzene to phenol by metal complex-clay/TiO2 hybrid photocatalyst

Synthetic saponite containing a photosensitizing metal complex was complexed with colloidal anatase and used for the visible light photocatalytic reaction of aqueous benzene to phenol.

Visible-Light-Responsive Photocatalytic Flow Reactor Composed of Titania Film Photosensitized by Metal Complex-Clay Hybrid

Synthetic saponite containing a photosensitizing metal complex, tris(2,2'-bipyridine)ruthenium(II)), in the interlayer space was complexed with anatase nanoparticles to obtain transparent hybrid film photocatalyst. The catalyst film was mounted in a flow reactor device to catalyze such photocatalytic reactions as the decomposition of aqueous acetic acid and N-alkylation of benzylamine with ethanol.