Photocatalytic degradation of endocrine disruptor compounds under simulated solar light

Nanostructured titanium materials with high UV-visible activity were synthesized in the collaborative project Clean Water FP7. In this study, the efficiency of some of these catalysts to degrade endocrine disruptor compounds, using bisphenol A as the model compound, was evaluated. Titanium dioxide P25 (AEROXIDE® TiO2, Evonik Degussa) was used as the reference. The photocatalytic degradation was carried out under the UV part of a simulated solar light (280–400 nm) and under the full spectrum of a simulated solar light (200 nm-30 μm). Catalytic efficiency was assessed using several indicators such as the conversion yield, the mineralization yield, by-product formation and the endocrine disruption effect of by-products. The new synthesized catalysts exhibited a significant degradation of bisphenol A, with the so-called ECT-1023t being the most efficient. The intermediates formed during photocatalytic degradation experiments with ECT-1023t as catalyst were monitored and identified. The estrogenic effect of the intermediates was also evaluated in vivo using a ChgH-GFP transgenic medaka line. The results obtained show that the formation of intermediates is related to the nature of the catalyst and depends on the experimental conditions. Moreover, under simulated UV, in contrast with the results obtained using P25, the by-products formed with ECT-1023t as catalyst do not present an estrogenic effect.We are grateful for the funding of the European Commission through the Clean Water Project which is a Collaborative Project (Grant Agreement number 227017) co-funded by the Research DG of the European Commission within the joint RTD activities of the Environment and NMP Thematic Prioritie

Influence of electrolyte co-additives on the performance of dye-sensitized solar cells

The presence of specific chemical additives in the redox electrolyte results in an efficient increase of the photovoltaic performance of dye-sensitized solar cells (DSCs). The most effective additives are 4-tert-butylpyridine (TBP), N-methylbenzimidazole (NMBI) and guanidinium thiocyanate (GuNCS) that are adsorbed onto the photoelectrode/electrolyte interface, thus shifting the semiconductor's conduction band edge and preventing recombination with triiodides. In a comparative work, we investigated in detail the action of TBP and NMBI additives in ionic liquid-based redox electrolytes with varying iodine concentrations, in order to extract the optimum additive/I2 ratio for each system. Different optimum additive/I2 ratios were determined for TBP and NMBI, despite the fact that both generally work in a similar way. Further addition of GuNCS in the optimized electrolytic media causes significant synergistic effects, the action of GuNCS being strongly influenced by the nature of the corresponding co-additive. Under the best operation conditions, power conversion efficiencies as high as 8% were obtained

Two-Functional Direct Current Sputtered Silver-Containing Titanium Dioxide Thin Films

The article reports on structure, mechanical, optical, photocatalytic and biocidal properties of Ti–Ag–O films. The Ti–Ag–O films were reactively sputter-deposited from a composed Ti/Ag target at different partial pressures of oxygen on unheated glass substrate held on floating potentialUfl. It was found that addition of ~2 at.% of Ag into TiO2film has no negative influence on UV-induced hydrophilicity of TiO2film. Thick (~1,500 nm) TiO2/Ag films containing (200) anatase phase exhibit the best hydrophilicity with water droplet contact angle (WDCA) lower than 10° after UV irradiation for 20 min. Thick (~1,500 nm) TiO2/Ag films exhibited a better UV-induced hydrophilicity compared to that of thinner (~700 nm) TiO2/Ag films. Further it was found that hydrophilic TiO2/Ag films exhibit a strong biocidal effect under both the visible light and the UV irradiation with 100% killing efficiency ofEscherichia coliATCC 10536 after UV irradiation for 20 min. Reported results show that single layer of TiO2with Ag distributed in its whole volume exhibits, after UV irradiation, simultaneously two functions: (1) excellent hydrophilicity with WDCA < 10° and (2) strong power to killE. colieven under visible light due to direct toxicity of Ag

New Insights into the Mechanism of Visible Light Photocatalysis

ABSTRACT: In recent years, the area of developing visible-lightactive photocatalysts based on titanium dioxide has been enormously investigated due to its wide range of applications in energy and environment related fields. Various strategies have been designed to efficiently utilize the solar radiation and to enhance the efficiency of photocatalytic processes. Building on the fundamental strategies to improve the visible light activity of TiO2-based photocatalysts, this Perspective aims to give an insight into many contemporary developments in the field of visible-light-active photocatalysis. Various examples of advanced TiO2 composites have been discussed in relation to their visible light induced photoconversion efficiency, dynamics of electron− hole separation, and decomposition of organic and inorganic pollutants, which suggest the critical need for further development of these types of materials for energy conversion and environmental remediation purposes

Recent developments of TiO2 photocatalysis involving advanced oxidation and reduction reactions in water

Advanced nanostructures of titanium dioxide are intensively investigated for environmental protection. The latest developments in the field pay special attention to innovative and highly performing titania materials (anatase/rutile mixed-phase nanocomposites, anion-doped core-shell nanostructures, self-organized nanotubes, photonic crystals and their modifications with graphene oxide and metal nanoparticles) with original functionalities and tailored properties (visible light activated photocatalysts-VLA), the elucidation of the corresponding mechanisms involving interaction of light with matter at the nanoscale and resulting photoinduced electron transfer reactions. These materials are also considered as key components for the design and fabrication of devices (photocatalytic reactors) for efficient degradation and/or transformation of emerging environmental contaminants. The presence of a TiO2 photocatalyst on the asymmetric membrane surface and pores insures simultaneous pollutant retention and photodegradation, permitting continuous long-term device operation without fouling, practical absence of concentrated retentate and cost effective production of clean water. Focusing on recent investigations of our group concerning the use of innovative titania nanostructured photocatalysts, the present work attempts to explore novel trends and present perspectives of TiO2 photocatalysis inside and outside the well-established frame of advanced oxidation processes (AOPs), expanding the field borders by including advanced reduction processes (ARPs) and relating technological applications (ARTs). © 2018 Elsevier Ltd

Low viscosity highly conductive ionic liquid blends for redox active electrolytes in efficient dye-sensitized solar cells

Mixtures of ionic liquids were prepared and used for the development of composite redox electrolytes electrolytes by blending a standard low viscosity ionic liquid solvent (EMimDCA, 1-ethyl-3methylimidazolium dicyanamide) with various iodide-based ionic liquids based on the methylimidazolium cation (DMII, EMII, PMII, BMII and HMII). The novel electrolytes based on the [CnC1im]I/EMimDCA double salt ILs show interesting physicochemical properties including low viscosity (10-110 MPa s) and high diffusion coefficient of triiodides (DI3-, 5-10 ¿ 10-7 cm2/s), respectively, characteristics that promiss increased performance in DSC devices. Their electrochemical properties along with the conductivity were also tuned and optimized; values as high as and 2-4 mS/cm were estimated for the conductivity. Solar cells based on these composite electrolytes attained efficiencies over 4% under 1 sun with the highest being 5.5%, attained by EMimDCA-DMII mixture. Quite notably, these efficiencies further increased up to 6.5%, when the cells were illuminated by 0.1 sun

Al-pillared acid-activated montmorillonite modified electrodes

The role of acid activation of the montmorillonite matrix before pillaring and the effect of calcination temperature on the efficiency of Al-pillared acid-activated clay modified electrodes have been investigated. The electrochemical behaviour of untreated and pillared montmorillonites was compared with that of two pillared acid-activated montmorillonites. The pillared acid-activated montmorillonite modified electrodes present better electroactivity than the modified electrodes of the conventional pillared montmorillonite towards cationic and anionic redox active species. Mild acid activation of the montmorillonite matrix and a calcination temperature up to 500 °C lead to modifying materials that efficiently concentrate the cationic species. Lower calcination temperatures reverse the electrode activity. For anionic redox active species the best electroactivity was observed for pillared acid-activated montmorillonite films corresponding to a medium acid activation. In that case, a dependence of the electrochemical response on the pH was confirmed. The mechanism responsible for the observed cationic electroactivity was investigated and the behaviour of the Al-pillared acid-activated montmorillonite modified electrodes was attributed to the particular structure as well as the enhanced meso-external surface area and acidity of the clay films