Eddy Petit

Correlation between degradation pathway and toxicity of acetaminophen and its by-products by using the electro-Fenton process in aqueous media

The evolution of the degradation by-products of an acetaminophen (ACE) solution was monitored by HPLC-UV/MS and IC in parallel with its ecotoxicity (Vibrio fischeri 81.9%, Microtox® screening tests) during electro-Fenton (EF) oxidation performed on carbon felt. The aromatic compounds 2-hydroxy-4-(N-acetyl) aminophenol, 1,4-benzoquinone, benzaldehyde and benzoic acid were identified as toxic sub-products during the first stage of the electrochemical treatment, whereas aliphatic short-chain carboxylic acids (oxalic, maleic, oxamic, formic, acetic and fumaric acids) and inorganic ions (ammonium and nitrate) were well identified as non-toxic terminal sub-products. Electrogenerated hydroxyl radicals then converted the eco-toxic and bio-refractory property of initial ACE molecule (500xa0mL, 1xa0mM) and subsequent aromatic sub-products into non-toxic compounds after 2xa0h of EF treatment. The toxicity of every intermediate produced during the mineralization of ACE was quantified, and a relationship was established between the degradation pathway of ACE and the global toxicity evolution of the solution. After 8xa0h of treatment, a total organic carbon removal of 86.9% could be reached for 0.1xa0mM ACE at applied current of 500xa0mA with 0.2xa0mM of Fe2+ used as catalyst.

Toxicity removal assessments related to degradation pathways of azo dyes: Toward an optimization of Electro-Fenton treatment.

The degradation pathway of Acid Orange 7 (AO7) by Electro-Fenton process using carbon felt cathode was investigated via HPLC-UV and LC-MS, IC, TOC analysis and bioassays (Vibrio Fischeri 81.9% Microtox(®) screening tests). The TOC removal of AO7 reached 96.2% after 8xa0h treatment with the optimal applied current density at -8.3xa0mAxa0cm(-2) and 0.2xa0mM catalyst concentration. The toxicity of treated solution increased rapidly to its highest value at the early stage of electrolysis (several minutes), corresponding to the formation of intermediate poisonous aromatic compounds such as 1,2-naphthaquinone (NAPQ) and 1,4-benzoquinone (BZQ). Then, the subsequent formation of aliphatic short-chain carboxylic acids like acetic acid, formic acid, before the complete mineralization, leaded to a non-toxic solution after 270xa0min for 500xa0mL of AO7 (1xa0mM). Moreover, a quantitative analysis of inorganic ions (i.e. ammonium, nitrate, sulfate) produced during the course of degradation could help to verify molar balance with regard to original nitrogen and sulfur elements. To conclude, a clear degradation pathway of AO7 was proposed, and could further be applied to other persistent pharmaceuticals in aquatic environment.

Squalyl Crown Ether Self-Assembled Conjugates: An Example of Highly Selective Artificial K(+) Channels.

The natural KcsA K+ channel, one of the best-characterized biological pore structures, conducts K+ cations at high rates while excluding Na+ cations. The KcsA K+ channel is of primordial inspiration for the design of artificial channels. Important progress in improving conduction activity and K+ /Na+ selectivity has been achieved with artificial ion-channel systems. However, simple artificial systems exhibiting K+ /Na+ selectivity and mimicking the biofunctions of the KcsA K+ channel are unknown. Herein, an artificial ion channel formed by H-bonded stacks of squalyl crown ethers, in which K+ conduction is highly preferred to Na+ conduction, is reported. The K+ -channel behavior is interpreted as arising from discreet stacks of dimers resulting in the formation of oligomeric channels, in which transport of cations occurs through macrocycles mixed with dimeric carriers undergoing dynamic exchange within the bilayer membrane. The present highly K+ -selective macrocyclic channel can be regarded as a biomimetic alternative to the KcsA channel.

Evidence of solute-solute interactions and cake enhanced concentration polarization during removal of pharmaceuticals from urban wastewater by nanofiltration.

The objective of this paper is to help understanding the distinctive influence of the matrix and of the flux decline (e.g. through the cake enhanced concentration polarization (CECP) phenomenon) on the removal mechanisms of four pharmaceutically active compounds (PhACs) from wastewater treatment plant (WWTP) effluent by nanofiltration (NF). PhACs which are commonly encountered in secondary treated effluent were spiked in various matrix (real and synthetic) to investigate the separate and synergetic effects of the organic and ionic environment on PhACs rejection by two commercial membranes (NF-90 and NF-270). With pure water, rejection of NF membranes is dependent on the type of PhACs and of the permeate flux variations. Then, it appeared that the rejection of PhACs by NF-90 was poorly influenced by the type of compounds, because of the prevalence of steric mechanisms, but rather influenced by permeate flux variations and thus to fouling. For this tight NF membrane, CECP impacts PhACs rejection at the start of filtration while after a dense cake is formed, it became enhanced. On the contrary, rejections of PhACs by the NF-270 were enhanced during the filtration of the real wastewater in comparison with spiked pure water. It appeared that for loose-NF membranes, PhACs rejection is mainly governed by solute-solute interactions (EfOM-compound association) or electrostatic membrane-solute interactions. Finally, it seems that calcium concentration of the effluent is a critical parameter for the rejection of PhACs as it alters both the availability of sites for PhACs association and the fouling layer density. Rejections of the NF-270 were negatively impacted in the presence of Ca2+. Such a study has practical implications for further understanding of the fate of trace organic compounds during nanofiltration of wastewater for reuse applications.

By-Product Carrying Humidified Hydrogen: An Underestimated Issue in the Hydrolysis of Sodium Borohydride.

Catalyzed hydrolysis of sodium borohydride generates up to four molecules of hydrogen, but contrary to what has been reported so far, the humidified evolved gas is not pure hydrogen. Elemental and spectroscopic analyses show, for the first time, that borate by-products pollute the stream as well as the vessel.

Influence of volumetric reduction factor during ozonation of nanofiltration concentrates for wastewater reuse

Global population growth induces increased threat on drinking water resources. One way to address this environmental issue is to reuse water from wastewater treatment plant. The presence of pathogenic microorganisms and potentially toxic organic micropollutants does not allow a direct reuse of urban effluents. Membrane processes such reverse osmosis (RO) or nanofiltration (NF) can be considered to effectively eliminate these pollutants. The integration of membrane processes involves the production of concentrated retentates which require being disposed. To date, no treatment is set up to manage safely this pollution. This work focuses on the application of ozonation for the treatment of NF retentates in the framework of the wastewater reuse. Ozonation is a powerful oxidation process able to react and degrade a wide range of organic pollutants. Four pharmaceutical micropollutants were selected as target molecules: acetaminophen, carbamazepine, atenolol and diatrozic acid. This study highlighted that NF represents a viable alternative to the commonly used RO process ensuring high retention at much lower operating costs. Ozonation appears to be effective to degrade the most reactive pollutants toward molecular ozone but is limited for the reduction of refractory ozone pollutants due to the inhibition of the radical chain by the high content of organic matter in the retentates. The ozonation process appears to be a promising NF retentate treatment, but additional treatments after ozonation are required to lead to a zero liquid discharge treatment scheme.

Pyrene-box capsules for adaptive encapsulation and structure determination of unstable or non-crystalline guest molecules

“Pyrene-box” cages easily crystallize from aqueous solutions and readily encapsulate compounds of biological interest. These host–guest systems can be obtained under ambient conditions from 1,3,5,8-pyrenetetrasulfonate (PTS), guanidinium derivatives (G+) and biogenic guests bearing cationic groups. Out of the many examples of synthetic molecular capsules, Pyrene box cages are completely responding to the requirements of green chemistry: non-toxic, water soluble, cheap, commercially available compounds. The “Pyrene-Box” cages have been used for the in situ encapsulation of unstable or non-crystalline biogenic compounds, allowing the complete molecular structure determination of species that do not crystallize by themselves. The encapsulated guests have a reduced motional degrees of freedom which is obtained via their anchoring to the Pyrene box cages that allows at the same time to reduce a significant amount of disorder. In this highlight we discuss the recent developments of the encapsulation chemistry of the “Pyrene box” and the strategy behind its synthesis, together with further possible developments and the limitations of this biomimetic supramolecular cage system. The “Pyrene Box” shows great potential for future applications, ranging from fundamental studies of structure determination of unstable molecules to drug delivery vehicles.

Ozonation as a pretreatment process for nanofiltration brines: Monitoring of transformation products and toxicity evaluation

Considerable interest has been given to using nanofiltration (NF) in lieu of reverse osmosis for water reclamation schemes due to lower energy consumption, higher flux rates while ensuring good micropollutants rejection. The application NF results in the generation of a large concentrated waste stream. Treatment of the concentrate is a major hurdle for the implementation of membrane technologies since the concentrate is usually unusable due to a large pollutants content. This work focuses on the application of ozonation as pretreatment of urban NF concentrates, the generation of transformation products and their relative toxicity. Three pharmaceutical micropollutants largely encountered in water cycle were selected as target molecules: acetaminophen, carbamazepine and atenolol. Through accurate-mass Q-TOF LC-MS/MS analyses, more than twenty ozonation products were detected, structure proposals and formation pathways were elaborated. Attempts were made to understand the correlation between the transformation products and acute toxicity on Vibrio fischeri strain. It is the first time that an integrated study reported on the ozonation of pharmaceuticals in urban membrane concentrates, in terms of transformation products, kinetics, degradation mechanisms, as well as toxicity assessment.

Design of Phosphonated Imidazolium-Based Ionic Liquids Grafted on γ-Alumina: Potential Model for Hybrid Membranes

Imidazolium bromide-based ionic liquids bearing phosphonyl groups on the cationic part were synthesized and grafted on γ-alumina (γ-Al2O3) powders. These powders were prepared as companion samples of conventional mesoporous γ-alumina membranes, in order to favor a possible transfer of the results to supported membrane materials, which could be used for CO2 separation applications. Effective grafting was demonstrated using energy dispersive X-ray spectrometry (EDX), N2 adsorption measurements, fourier transform infrared spectroscopy (FTIR), and special attention was paid to 31P and 13C solid state nuclear magnetic resonance spectroscopy (NMR).

Assessing the Potential of Sodium 1-Oxa-nido-dodecaborate NaB11H12O for Energy Storage

In the recent years, polyborate anions have been considered as possible candidates for energy. In aqueous solutions, they have been studied as either hydrogen carriers or anodic fuels. In the solid state (as an alkali salt), they have been seen as solid electrolytes. Herein, we focus on sodium 1-oxa-nido-dodecaborate NaB11H12O, a novel possible candidate for the aforementioned applications. The compound is soluble in water, and its stability depends on pH: under acidic conditions, it readily hydrolyzes while liberating hydrogen, and under alkaline conditions, it is stable, which is a feature searched for an anodic fuel. Over bulk platinum, gold, or silver electrode, oxidation takes place. The best performance has been noticed for the silver electrode. In the solid state, NaB11H12O shows Na+ conductivity at a high temperature of up to 150 °C. All of these properties are presented in detail, and hereafter they are discussed while giving indications of what have to be developed to open up more realistic prospectives for NaB11H12O in energy.