Unexpected effect of ozone on the paraben's mixture degradation using TiO2 supported nanotubes

Ozonation of Selected Pharmaceutical and Personal Care Products in Secondary Effluent-Degradation Kinetics and Environmental Assessment

The efficiency of ozonation depends on the water matrix and the reaction time. Herein, these factors were addressed by assessing the removal of five pharmaceutical and personal care products (PPCPs) by ozonation. The main aims were: (i) to assess the effects of the water matrix on the degradation kinetics of PPCPs, individually and in mixture, following ozonation; and (ii) to assess the ecotoxicological impact of the ozone reaction time on the treatment of a spiked municipal wastewater (MW) added the five PPCPs over several species. The degradation of the PPCPs was faster in ultrapure water, with all PPCPs being removed in 20 min, whereas in the MW, a 30 min ozonation period was required to achieve a removal close to 100%. Increasing the number of PPCPs in the water matrix did not affect the time required for their removal in the MW. Regarding the ecotoxicity assessment, Raphidocelis subcapitata and Daphnia magna were the least sensitive species, whereas Lemna minor was the most sensitive. The temporal variation of the observed effects corroborates the degradation of the added PPCPs and the formation of toxic degradation by-products. The removal of the parent compounds did not guarantee decreased hazardous potential to biological species.

Nanostructured photocatalysts for the abatement of contaminants by photocatalysis and photocatalytic ozonation: An overview

The water scarcity, the presence of different contaminants in the worldwide waters and wastewaters and their impacts should motivate their good elimination and water management. With this, photocatalysis and photocatalytic ozonation are strong solutions to obtain good quality reclaimed water, for different applications. Nanostructured supported photo-active catalysts, such as the TiO₂, WO₃ or ZnO can positively affect the performance of such technologies. Therefore, different semiconductors materials have been aroused the interest of the scientific community, mainly due to its functional properties as well as characteristics imposed by the different nanostructures. With this, this work overviews different works and perspective on the TiO₂ nanotubes and other semiconductors nanostructures, with the analysis of different works from 2001 to 2022. Aspects as the substrate effect, electrolyte nature, aspect ratio, electrolyte aging, and annealing treatment but also the effect of morphology, anodization time, applied voltage, temperature and viscosity are discussed. Modification of TiO₂ nanotubes is also presented in this paper. The main objective of this work is to present and discuss the key parameters and their effects on the anodization of different semiconductors, as well as the results obtained until today on the degradation of different contaminants by photocatalysis and photocatalytic ozonation, as well as their use on the treatment of real wastewater. TiO₂ nanotubes present unique properties and highly ordered configuration, which motivate their use on photo-driven technologies for the pollutant's abatement, even when compared to other nanostructures. However, photocatalysts with activity on the visible range and solar radiation, such as the WO₃, can present higher performance and can decrease operational costs, and must be an important source and a key to find efficient and cost-friendly solutions.

Fabrication of Efficient Gold−Nickel-Supported Titania Nanotube Electrocatalysts for Sodium Borohydride−Hydrogen Peroxide Fuel Cells

Here we report the optimization of the fabrication conditions for AuNi bimetallic catalysts supported on self-ordered titania nanotube arrays (AuNi-TiO2ntb). A series of efficient AuNi-TiO2ntb catalysts with small amounts of Au in the range of 1.74 to 15.7 μgAu·cm−2 have been fabricated by anodization, electroless Ni plating, and galvanic displacement techniques. The electrocatalytic activity of the catalysts has been evaluated for BH4− ion oxidation in an alkaline medium using cyclic voltammetry and chronoamperometry. The performance of a NaBH4-H2O2 fuel cell with Ni-TiO2ntb and AuNi-TiO2ntb anode catalysts has been investigated at different temperatures. It was found that the electrocatalytic activity of AuNi-TiO2ntbs catalysts was improved remarkably when the Ni layer of 100 and 400 nm was used for the deposition of Au crystallites. The Ni-TiO2ntb catalyst generates the maximum power density values of ca. 85–121 mW·cm−2 at a temperature of 25–55 °C, whereas the AuNi-TiO2ntb catalysts that have the Au loading of 3.07 and 15.7 μgAu·cm−2 achieve the power density values of ca. 104–147 and 119–170 mW·cm−2, respectively, at a temperature of 25–55 °C.

Degradation of aqueous methylparaben by non-thermal plasma combined with ZnFe2O4-rGO nanocomposites: Performance, multi-catalytic mechanism, influencing factors and degradation pathways

Non-thermal plasma (NTP) combined with zinc ferrite-reduced graphene oxide (ZnFe₂O₄-rGO) nanocomposites were used for the degradation of aqueous methylparaben (MeP). ZnFe₂O₄-rGO nanocomposites were prepared using the hydrothermal method, with the structure and photoelectric properties of nanocomposites then characterized. The effects of discharge power, initial MeP concentration, initial pH, and air flow rate on MeP degradation efficiency were investigated, and the multi-catalytic mechanism and MeP degradation pathways were established. Results showed that ZnFe₂O₄-rGO nanocomposites with a 10%:90% mass ratio of GO:ZnFe₂O₄ had an optimal catalytic effect. The MeP degradation efficiency of NTP combined with ZnFe₂O₄-rGO (10 wt%), was approximately 25% higher than that of NTP alone. Conditions favorable for MeP degradation included higher discharge power, lower MeP concentration, neutral pH value, and higher air flow rate. The degradation of MeP by NTP combined with ZnFe₂O₄-rGO nanocomposites followed pseudo-first-order kinetics. O₂^•-, •OH, H₂O_2, and O₃ were found to play important roles in the MeP degradation, as part of the multi-catalytic mechanism of NTP combined with ZnFe₂O₄-rGO nanocomposites. MeP degradation pathways were proposed based on the degradation intermediates detected by gas chromatography mass spectrometry, including demethylation, hydroxylation, carboxylation, ring-opening, and mineralization reactions. The prepared ZnFe₂O₄-rGO nanocomposites provide an approach for improved contaminant degradation efficiency, with reduced energy consumption in the NTP process.

Paraben Compounds—Part II: An Overview of Advanced Oxidation Processes for Their Degradation

Water scarcity represents a problem for billions of people and is expected to get worse in the future. To guarantee people’s water needs, the use of “first-hand water” or the reuse of wastewater must be done. Wastewater treatment and reuse are favorable for this purpose, since first-hand water is scarce and the economic needs for the exploration of this type of water are increasing. In wastewater treatment, it is important to remove contaminants of emerging concern, as well as pathogenic agents. Parabens are used in daily products as preservatives and are detected in different water sources. These compounds are related to different human health problems due to their endocrine-disrupting behavior, as well as several problems in animals. Thus, their removal from water streams is essential to achieve safe reusable water. Advanced Oxidation Processes (AOPs) are considered very promising technologies for wastewater treatment and can be used as alternatives or as complements of the conventional wastewater treatments that are inefficient in the removal of such contaminants. Different AOP technologies such as ozonation, catalytic ozonation, photocatalytic ozonation, Fenton’s, and photocatalysis, among others, have already been used for parabens abatement. This manuscript critically overviews several AOP technologies used in parabens abatement. These treatments were evaluated in terms of ecotoxicological assessment since the resulting by-products of parabens abatement can be more toxic than the parent compounds. The economic aspect was also analyzed to evaluate and compare the considered technologies.