Application of Fe/Activated Carbon Catalysts in the Hydroxylation of Phenol to Dihydroxybenzenes

A series of Fe/activated carbon catalysts were prepared by impregnation of activated carbon with aqueous solution of ferric nitrate and employed in phenol hydroxylation to dihydroxybenzenes using hydrogen peroxide as oxidant. The samples were characterized by thermal analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), N₂-adsorption, temperature-programmed oxidation mass spectrometry (TPO-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Part of the ferric (Fe­(III)) species was reduced to ferrous (Fe­(II)) species forming Fe₃O₄ when the Fe/activated carbon catalyst was heated at 400 °C for 3 h in air. Fe₃O₄ highly dispersed on activated carbon was found to be the active phase for the target reaction. The appearance of ferrous (Fe­(II)) species greatly improved the catalytic activity. A phenol conversion of 41.3% and a yield of 36.0% to dihydroxybenzenes were obtained under the following optimal reaction conditions: catalyst amount, 0.1 g; reaction temperature, 30 °C; molar ratio of phenol/H₂O₂, 10.6/9.8; reaction time, 1 h

Table1_A novel heterozygous SIX1 missense mutation resulted in non-syndromic unilateral hearing loss.DOCX

Familial non-syndromic unilateral hearing loss (NS-UHL) is rare and its genetic etiology has not been clearly elucidated. This study aimed to identify the genetic cause of NS-UHL in a three-generation Chinese family. Detailed medical history consultation and clinical examination were conducted. Further, whole-exome sequencing (WES) was performed to identify the genetic etiology of the proband, and the variant was verified by Sanger sequencing. A novel missense mutation, c.533G>C (p.Arg178Thr), in the SIX homeobox 1 gene (SIX1) was identified in four patients and co-segregated with NS-UHL in a three-generation Chinese family as a dominant trait. Using bioinformatics analyses, we show that this novel mutation is pathogenic and affects the structure of SIX1 protein. These data suggest that mutations in SIX1 gene are associated with NS-UHL. Our study added the NS-UHL phenotype associated with SIX1, and thereby improving the genetic counseling provided to individuals with SIX1 mutations.</p

Can Silica Particles Reduce Air Pollution by Facilitating the Reactions of Aliphatic Aldehyde and NO₂?

This study investigated the heterogeneous atmospheric reactions of acetaldehyde, propanal, and butanal with NO₂ onto silica (SiO₂) clusters using a theoretical approach. By analyzing spectral features and adsorption parameters, the formation of hydrogen bonds and negative adsorption energies provide evidence that an efficient spontaneous uptake of aliphatic aldehydes onto SiO₂ could occur. The atmospheric reaction mechanisms show that when aldehydes and NO₂ react on the surface model, the H atom abstraction reaction from the aldehydic molecule by NO₂ is an exclusive channel, forming nitrous acid and acyl radicals. This study included kinetics exploring the reaction of aldehydes with NO₂ using a canonical variational transition state theory. The reaction rate constants are increased in the presence of SiO₂ between the temperatures 217 and 298 K. This may explain how aldehydes can temporarily stay on mineral particles without chemical reactions. The results suggest that silica can depress the rate at which the studied aldehydes react with NO₂ and possibly reduce air pollution generated by these atmospheric reactions

Kinetics and Mechanism of ^•OH Mediated Degradation of Dimethyl Phthalate in Aqueous Solution: Experimental and Theoretical Studies

The hydroxyl radical (^•OH) is one of the main oxidative species in aqueous phase advanced oxidation processes, and its initial reactions with organic pollutants are important to understand the transformation and fate of organics in water environments. Insights into the kinetics and mechanism of ^•OH mediated degradation of the model environmental endocrine disruptor, dimethyl phthalate (DMP), have been obtained using radiolysis experiments and computational methods. The bimolecular rate constant for the ^•OH reaction with DMP was determined to be (3.2 ± 0.1) × 10⁹ M^–1s^–1. The possible reaction mechanisms of radical adduct formation (RAF), hydrogen atom transfer (HAT), and single electron transfer (SET) were considered. By comparing the experimental absorption spectra with the computational results, it was concluded that the RAF and HAT were the dominant reaction pathways, and OH-adducts (^•DMPOH₁, ^•DMPOH₂) and methyl type radicals ^•DMP­(-H)­α were identified as dominated intermediates. Computational results confirmed the identification of transient species with maximum absorption around 260 nm as ^•DMPOH₁ and ^•DMP­(-H)­α, and these radical intermediates then converted to monohydroxylated dimethyl phthalates and monomethyl phthalates. Experimental and computational analyses which elucidated the mechanism of ^•OH-mediated degradation of DMP are discussed in detail

Synthesis and Characterization of Novel Plasmonic Ag/AgX-CNTs (X = Cl, Br, I) Nanocomposite Photocatalysts and Synergetic Degradation of Organic Pollutant under Visible Light

A series of novel well-defined Ag/AgX (X = Cl, Br, I) loaded carbon nanotubes (CNTs) composite photocatalysts (Ag/AgX-CNTs) were fabricated for the first time via a facile ultrasonic assistant deposition–precipitation method at the room temperature (25 ± 1 °C). X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption analysis, scanning electron microscopy, and ultraviolet–visible light absorption spectra analysis were used to characterize the structure, morphology, and optical properties of the as-prepared photocatalysts. Results confirmed the existence of the direct interfacial contact between Ag/AgX nanoparticles and CNTs, and Ag/AgX-CNTs nanocomposites exhibit superior absorbance in the visible light (VL) region owing to the surface plasmon resonance (SPR) of Ag nanoparticles. The fabricated composite photocatalysts were employed to remove 2,4,6-tribromophenol (TBP) in aqueous phase. A remarkably enhanced VL photocatalytic degradation efficiency of Ag/AgX-CNTs nanocomposites was observed when compared to that of pure AgX or CNTs. The photocatalytic activity enhancement of Ag/AgX-CNTs was due to the effective electron transfer from photoexcited AgX and plasmon-excited Ag(0) nanoparticles to CNTs. This can effectively decrease the recombination of electron–hole pairs, lead to a prolonged lifetime of the photoholes that promotes the degradation efficiency

Synthesis of Carbon Nanotube–Anatase TiO₂ Sub-micrometer-sized Sphere Composite Photocatalyst for Synergistic Degradation of Gaseous Styrene

The carbon nanotube (CNT)–sub-micrometer-sized anatase TiO₂ sphere composite photocatalysts were synthesized by a facile one-step hydrothermal method using titanium tetrafluoride as titanium source and CNTs as structure regulator. Various technologies including X-ray diffraction, UV–visible absorption spectra, N₂ adsorption–desorption, scanning electron microscopy, and transmission electron microscopy were employed to characterize the structure properties of the prepared composite photocatalysts. The results indicated that the composite photocatalysts consisted of CNTs wrapping around the sub-micrometer-sized anatase TiO₂ spheres with controllable crystal facets and that the aggregated particles with average diameter ranged from 200 to 600 nm. The fabricated composite photocatalysts were used to degrade gaseous styrene in this work. As expected, a synergistic effect that remarkably enhancing the photocatalytic degradation efficiency of gaseous styrene by the prepared composite photocatalysts was observed in comparison with that the degradation efficiency using pure anatase TiO₂ and the adsorption of CNTs. Similar results were also confirmed in the decolorization of liquid methyl orange. Further investigation demonstrated that the synergistic effect in the photocatalytic activity was related to the structure of the sub-micrometer-sized anatase TiO₂ spheres and the significant roles of CNTs in the composite photocatalysts. By controlling the content of CNTs, the content of TiO₂ or the temperature during the hydrothermal synthesis process, anatase TiO₂ spheres with controllable crystallite size and dominant crystal facets such as {001}, {101}, or polycrystalline could be obtained, which was beneficial for the increase in the synergistic effect and further enhancement of the photocatalytic efficiencies

Systematic Approach to In-Depth Understanding of Photoelectrocatalytic Bacterial Inactivation Mechanisms by Tracking the Decomposed Building Blocks

A systematic approach was developed to understand, in-depth, the mechanisms involved during the inactivation of bacterial cells using photoelectrocatalytic (PEC) processes with <i>Escherichia coli</i> K-12 as the model microorganism. The bacterial cells were found to be inactivated and decomposed primarily due to attack from photogenerated H₂O₂. Extracellular reactive oxygen species (ROSs), such as H₂O₂, may penetrate into the bacterial cell and cause dramatically elevated intracellular ROSs levels, which would overwhelm the antioxidative capacity of bacterial protective enzymes such as superoxide dismutase and catalase. The activities of these two enzymes were found to decrease due to the ROSs attacks during PEC inactivation. Bacterial cell wall damage was then observed, including loss of cell membrane integrity and increased permeability, followed by the decomposition of cell envelope (demonstrated by scanning electronic microscope images). One of the bacterial building blocks, protein, was found to be oxidatively damaged due to the ROSs attacks, as well. Leakage of cytoplasm and biomolecules (bacterial building blocks such as proteins and nucleic acids) were evident during prolonged PEC inactivation process. The leaked cytoplasmic substances and cell debris could be further degraded and, ultimately, mineralized with prolonged PEC treatment

HIV Prevalence and estimated incidence of MSM in sentinel surveillance surveys in Beijing, 2008–2016.

<p>HIV Prevalence and estimated incidence of MSM in sentinel surveillance surveys in Beijing, 2008–2016.</p

Trends of HIV incidence and prevalence among MSM in Beijing, 2008–20016.

<p>Trends of HIV incidence and prevalence among MSM in Beijing, 2008–20016.</p