Effect of Noble Metals (Ag, Pd, Pt) Loading over the Efficiency of TiO2 during Photocatalytic Ozonation on the Toxicity of Parabens

Abstract

Abstract:The conventional wastewater treatments are inadequate for emerging contaminants detoxification. Photocatalytic ozonation with suitable catalyst can be considered as a suitable solution on the removal of these compounds. The aim of this study was to verify the effect of Ag, Pd and Pt with different loadings (0.1, 0.5 and 1% wt %) onto TiO 2 surface for the degradation of a mixture of parabens (methyl, ethyl, propyl, butyl and benzyl) through photocatalytic ozonation. Chemical oxygen demand (COD) and total organic carbon (TOC) was also analyzed after treatments, as well as the effect of the treatment on the samples toxicity over different species, including bacteria, clams and plants. The effect of metal loading on the parabens degradation; COD and TOC removal is very dependent upon the type of noble metal used. This can be related with the different pathways influenced by the metal load. On the one hand, it can be related with the reduction of electron-hole recombination phenomenon, and, on the other hand, the trapping of electrons by the metals reduces the amount of ozonide and hydroxyl radicals produced. In terms of toxicity, apparently the best results were achieved with the intermediate noble metal load. However, the effect of noble metal load must be analyzed case to case.

Au/ZnO Hybrid Nanostructures on Electrospun Polymeric Mats for Improved Photocatalytic Degradation of Organic Pollutants

“…The presence of Au aggregates on the ZnO NPs catalyst causes a decrease of their active surface exposed towards the organic pollutants and also a less effective light penetration due to a screening effect [22,28,47]. This result is also confirmed by previous studies; as a matter of fact, there is an optimal concentration of metallic NPs for the surface modification of the metal oxide semiconductors, beyond which the photocatalytic performance declines [46,48].…”

Removal of Enteric Pathogens from Real Wastewater Using Single and Catalytic Ozonation

“…Single and catalytic ozonation were carried out in a 2 L glass reactor with a thermostatic water-bath to maintain the temperature (25 ± 1 • C) and continuous stirring using a magnetic stirrer at 700 rpm [33,34]. Moreover, when a solid catalyst was used, the size of particles used was lower than 105 µm.…”

Ozone and Photocatalytic Processes for Pathogens Removal from Water: A Review

“…This coupling leads to an improvement of hydroxyl radicals production due to the synergetic effect between ozonation and photocatalysis [141]. Ozone electrophilic character enhances photogenerated electrons to be withdrawn, which minimizes the electron-hole recombination contributing to a more effective and fast process [142,143].…”