Degradation of ethylparaben under simulated sunlight using photo-Fenton

Degradation of Methylparaben Using Optimal WO3 Nanostructures: Influence of the Annealing Conditions and Complexing Agent

In this work, WO₃ nanostructures were synthesized with different complexing agents (0.05 M H₂O₂ and 0.1 M citric acid) and annealing conditions (400 °C, 500 °C and 600 °C) to obtain optimal WO₃ nanostructures to use them as a photoanode in the photoelectrochemical (PEC) degradation of an endocrine disruptor chemical. These nanostructures were studied morphologically by a field emission scanning electron microscope. X-ray photoelectron spectroscopy was performed to provide information of the electronic states of the nanostructures. The crystallinity of the samples was observed by a confocal Raman laser microscope and X-ray diffraction. Furthermore, photoelectrochemical measurements (photostability, photoelectrochemical impedance spectroscopy, Mott-Schottky and water-splitting test) were also performed using a solar simulator with AM 1.5 conditions at 100 mW·cm^-2. Once the optimal nanostructure was obtained (citric acid 0.01 M at an annealing temperature of 600 °C), the PEC degradation of methylparaben (C_O 10 ppm) was carried out. It was followed by ultra-high-performance liquid chromatography and mass spectrometry, which allowed to obtain the concentration of the contaminant during degradation and the identification of degradation intermediates. The optimized nanostructure was proved to be an efficient photocatalyst since the degradation of methylparaben was performed in less than 4 h and the kinetic coefficient of degradation was 0.02 min^-1.

Removal of parabens and their chlorinated by-products by periphyton: influence of light and temperature

The extensive use of parabens as preservatives in food and pharmaceuticals and personal care products results in frequent detection of their residuals in aquatic environment. In this work, the adsorption and removal of four parabens (methyl-, ethyl-, propyl-, and butyl-paraben) and two chlorinated methyl-parabens (CMPs) by periphyton were studied. Characteristics of the periphyton were identified to explore the possible relationship between paraben removal and periphyton properties. Results showed that linear adsorption coefficients (K _d) vary from 554.4 to 808.6 L kg^-1 for the adsorption parabens and CMPs to autoclaved periphyton. The adsorption strength is positively related to the hydrophobicity of these compounds. Removal of parabens from water by periphyton was efficient with half-life (t _1/2) values estimated using first-order kinetic model ranging from 0.49 to 3.29 days, but CMPs were more persistent with t _1/2 ranging from 1.15 to 25.57 days, and t _1/2 increased with the chlorination degree. Higher incubation temperature accelerated the removal of all tested compounds, while a better removal of CMPs was observed in dark condition. Analysis of periphyton properties suggests that bacteria played a more important role in the removal of CMPs, but no specific relationship between periphyton properties and paraben removal ability can be established.

Monitoring of emerging pollutants in Guadiamar River basin (South of Spain): analytical method, spatial distribution and environmental risk assessment

Guadiamar River is located in the southwest of the Iberian Peninsula and connects two protected areas in the South of Spain: Sierra Morena and Doñana National Park. It is sited in an area affected by urban, industrial and agriculture sewage pollution and with tradition on intensive mining activities. Most of the studies performed in this area have been mainly focused on the presence of heavy metals and, until now, little is known about the occurrence of other contaminants such as emerging organic pollutants (EOPs). In this work, an analytical method has been optimized and validated for monitoring of forty-seven EOPs in surface water. The analytical method has been applied to study the distribution and environmental risk of these pollutants in Guadiamar River basin. The analytical method was based on solid-phase extraction and determination by liquid chromatography-triple quadrupole-tandem mass spectrometry. The 60 % of the target compounds were found in the analyzed samples. The highest concentrations were found for two plasticizers (bisphenol A and di(2-ethyhexyl)phthalate, mean concentration up to 930 ng/L) and two pharmaceutical compounds (caffeine (up to 623 ng/L) and salicylic acid (up to 318 ng/L)). This study allowed to evaluate the potential sources (industrial or urban) of the studied compounds and the spatial distribution of their concentrations along the river. Environmental risk assessment showed a major risk on the south of the river, mainly due to discharges of wastewater effluents.