The degradation of perfluorooctanoic acid (PFOA) in high-salinity wastewater remains a critical challenge, as conventional advanced oxidation processes suffer from severe scavenging of reactive species by coexisting ions. This study investigates how carrier gas composition and solution conductivity affect PFOA defluorination (50 mg/L) in a nanosecond pulsed gas-liquid interface plasma reactor. By systematically evaluating the effects of carrier gases (N2 and O2) and solution conductivities (0.01 to 22.6 mS/cm using NaCl and Na2SO4), we describe an observed shift in the dominant macroscopic controlling variable for PFOA defluorination as solution conductivity increases. At low conductivity ( 0.01 mS/cm), the defluorination rate is sensitive to the carrier gas composition: an N2 atmosphere produced roughly twice the fluoride yield of an O2 atmosphere at 240 s, consistent with a reductive contribution that may involve hydrated electrons. At high conductivity (6.2–22.6 mS/cm, NaCl or Na2SO4), the reduced liquid impedance raised the injected energy per pulse by a factor of 1.6–1.9, and the N2/O2 difference largely disappeared. Defluorination data from all four gas/salt combinations converged onto a single energy-dose curve, indicating that within the parameter range studied, cumulative energy input becomes a sufficient macroscopic descriptor of the observed defluorination rate. The underlying C–F bond cleavage remains electron-driven throughout, and the effects of ionic strength, interfacial PFOA enrichment, dissolved O2 reduction, and discharge morphology cannot be independently separated in the present experimental design. These results suggest that nanosecond pulsed plasma can maintain defluorination performance in high-salinity matrices where conventional AOPs are strongly inhibited by radical scavenging.

Waste beverages are utilized as resources in various valuable, albeit energy-consuming, waste-to-energy processes. There is a growing need for alternative cost-effective methods to harness their potential. This study explored the feasibility of employing waste beverages as feedstock for the counterpart component of a TiO2-based composite photocatalyst. Several commonly available carbonated soft drinks from the Japanese market have been investigated to achieve this goal. The investigation revealed that a mild hydrothermal treatment condition could transform all examined beverages into carbonaceous materials suitable for fabricating a core-shell structure with TiO2, resulting in a remarkably efficient visible light active photocatalyst. Notably, a pH-adjusted photocatalyst derived from Coca Cola® exhibited superior visible light photodegradability toward dye molecules and enhanced bactericidal efficacy compared to the counterpart derived from pure sucrose. The heightened visible light photocatalytic activity can be attributed to the distinctive carboxy-rich surface functional groups, based on the findings of experimental analyses and density functional theory calculations. The bidentate-type bonding of these groups with TiO2 induces a modified interfacial bond structure that facilitates the efficient transfer of photoexcited carriers. This study presents a novel avenue for the effective utilization and recycling of waste beverages, and adds value under environmentally benign conditions.

Charge separation and migration is still a big challenge for photocatalysis. Constructing heterojunction interface structure is a useful way to improve charge separation efficiency. Here, a novel glycerolate-derived n-type TiO2 with oxygen vacancies was hybridized with Co1.29Ni1.71O4 by a facial ultrasonication method to achieve such a purpose. The optimized 2.5 % Co1.29Ni1.71O4/TiO2 hybrid showed a photocatalytic hydrogen evolution rate of 1685 & mu;mol g-1 h-1 under 365 nm LED light irradiation, 26.7-fold higher than that of pure TiO2 (63 & mu;mol g-1 h-1). Besides, the hydrogen production amount kept a linear increase with the increase of irradiation time for the 2.5%Co1.29Ni1.71O4/TiO2 catalyst during a 24 h-long continuous hydrogen release test, confirming the excellent catalytic stability. Detailed characterizations demonstrated that Co1.29Ni1.71O4 nanosheet was closely contacted with TiO2 nanoparticles, which increases specific surface area and widens the light absorption window of TiO2. Moreover, Co1.29Ni1.71O4 addition facilitated highly efficient separation of photogenerated carriers and prolongs lifetimes of the excited electrons. First principles calculations confirmed that there existed strong interaction between Co1.29Ni1.71O4 and TiO2 in the composite, and electrons were directly transferred from Co1.29Ni1.71O4 to TiO2 at the interface by the Ni-O and Co-O pathway. All of these leaded to a high photocatalytic hydrogen evolution activity for the Co1.29Ni1.71O4/TiO2 composite. This work revealed Co1.29Ni1.71O4 to be a promising heterojunction counterpart material and able to promote photocatalysis through unique cross-boundary charge transfer.

Sacrifiers-promoted photocatalysis is a useful way to achieve high efficiency photoreduction and photocatalytic hydrogen production for photocatalysts of weak reductive power such as TiO2. Herein we report a new method to fabricate a unique dyadic hybrid consisting of closely compacted crystalline (anatase) and titanium glycerolate (TiG)-derived organic group-retained amorphous nanoparticles to validate adsorption-stored sacrifiers-promoted photocatalysis instead of using sacrifiers in bulk solution. It was found that ascorbic acid (AA)-modified TiG prepared at a small fraction of glycerol, characterized by peculiar cocoon/open nanocontainer-type morphologies, varieties of oxygen containing groups, and remarkably high specific surface area, is suitable for precursing such hybrids. AA can change crystallization processes and particle morphologies by terminating chain linkages in TiG structure, which increases porosity and brings about visible light responsive photocatalysis for the dyadic hybrid. Benefiting from good adsorption affinity to organic sacrifiers, the sacrifier-prestored hybrid can catalyze significantly enhanced photoreduction with good reproducibility toward dye molecules via the synergy of sacrifier enrichment and photocatalysis. AA modified TiG also exhibits good self-reducibility enabling pre-loading of highly dispersed and localized platinum nanoparticles, and the resulted dyadic hybrid facilitates photocatalytic hydrogen production of extremely higher turn-off frequency and better impurities interference-resistivity compared to the P25-based commercial catalyst.

Characteristics of polymeric- and electronic structure of graphitic carbon nitride (g-C3N4) responsible for the photocatalytic activity were analyzed with oxidation reaction of nitrogen monoxide (NO) and various kinds of spectroscopies. The photocatalytic activity per surface area was increased with increasing the preparation temperature up to 520 degrees C, and was decreased above 520 degrees C while the visible light absorbance and the relative surface area was increased with the preparation temperature up to 650 degrees C. Laser desorption/ionization mass spectrometry (LDI-MS) showed that the content of cyano group connected with tri-s-triazine unit in g-C3N4 increases with increasing the preparation temperature and that g-C3N4. with higher activity per surface area contained smaller amount of cyano group. Additionally, the degree of polymerization and the planarity of carbon-nitride layer possibly contributed for formation of mid-gap levels that increases the number of unpaired electron. The formation of the mid-gap level was not effective for the photocatalytic activity, but rather deactivated g-C3N4.

Photochemical decomposition of monoethanolamine (MEA) in the presence of graphitic carbon nitride (g-C3N4) in water under visible-light irradiation was investigated. When aqueous MEA was irradiated by visible light ( >389 nm) in the presence of either TiO2 (P25) and O-2 or g-C3N4 and argon, virtually no decomposition of MEA was observed. In contrast, when aqueous MEA was irradiated by visible light in the presence of g-C3N4 and O-2, the MEA decomposed to produce HCOOH, NO2-, NO3-, and NH3. Although metal (Ag or Pt)-loading onto g-C3N4 enhanced the photocatalytic MEA decomposition slightly, it accelerated the formation of NO2- and NO3-. After the g-C3N4 catalyzed reactions, the recovery of carbon atoms was almost completely accounted for by the remaining MEA and HCOOH formed in the reaction solution, indicating that the carbon atoms in the reacted MEA were predominantly transformed to HCOOH. (C) 2017 Elsevier B.V. All rights reserved.

Modification of graphitic carbon nitride (g-C3N4) with silver metal significantly improved the adsorption capacity and the photocatalytic degradation activity for methyl mercaptan, which is a typical sulfurous compound, under visible light. These improvements were easily obtained by the shear mixing method. The ultrafine crystallites of metallic silver were formed on surface of carbon nitride by shear mixing of HT-g-C3N4 (Hydrothermal treated g-C3N4) in aqueous solution of silver acetate. One atom of the silver captured ca. 0.6 molecule of methyl mercaptan on average, while a silver atom deposited on TiO2 captured only 0.03 molecule. The migration of silver crystallites over the g-C3N4 surface and the formation of silver thin-layer during the adsorption of methyl mercaptan were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The silver crystallite on g-C3N4 seemed to have higher mobility than that on TiO2 to form the coordination suitable for the adsorption of methyl mercaptan. This coordination of Ag also enhanced the photocatalytic degradation of methyl mercaptan to dimethyl disulfide. (C) 2016 Elsevier B.V. All rights reserved.

We developed a photocatalytic solar tower reactor for the elimination of low concentrations of volatile organic compounds (VOCs) typically emitted from small industrial establishments. The photocatalytic system can be installed in a narrow space, as the reactor is cylindrical-shaped. The photocatalytic reactor was placed vertically in the center of a cylindrical scattering mirror, and this vertical reactor was irradiated with scattered sunlight generated by the scattering mirror. About 5 ppm toluene vapor, used as representative VOC, was continuously photodegraded and converted to CO2 almost stoichiometrically under sunny conditions. Toluene removal depended only on the intensity of sunlight. The performance of the solar tower reactor did not decrease with half a year of operation, and the average toluene removal was 36% within this period.

The effect of the silica and alumina ratio (Si/Al) in HY was studied as an important parameter that determines the catalytic activity of zeolite under plasma activation. The Ag loaded on HI was in a more oxidized state at lower Si/Al ratios and in a more metallic state at higher Si/Al ratios. A substantial drop in the relative electrical resistivity occurred when Ag was supported on the HI at a Si/Al ratio of 40. A strong relationship between the propagation of surface streamers and the catalytic activity was observed when the Si/Al ratio was changed in the following order: 2.6 >15 >40. The interactions of oxygen plasma and Ag-loaded HY zeolites were clearly demonstrated via electron spin resonance (ESR) measurements of divalent silver (Ag2+) and Fe3+ cations and plasma-induced fluorescence of Ag-cation clusters. (C) 2014 Elsevier B.V. All rights reserved.

Dimethyl methylphosphonate (DMMP) removal by a continuous photocatalytic reaction system at different levels of humidity (RH) was investigated for the purpose of allowing rescue operations at disaster sites over an extended period of time when applied to gas masks or other protective gear. With a high flow rate of air (10 L/min), around 85% of the 0.17 mu mol/L DMMP was successfully eliminated by this photocatalytic reaction system regardless of relative humidity. On the other hand, the formation of intermediates on the TiO2 surface indicated that photocatalytic activity was dependent on relative humidity, and during a 5-h test period, the ratio of photocatalytic DMMP conversion reached 74.5% at 100% RH. DMMP adsorption onto the TiO2 surface was found to be quite strong; DMMP removal was observed despite low humidity and dark conditions (C) 2013 Elsevier B.V. All rights reserved.

Ethyl S-diisopropylaminoethyl methylphosphonothioate (VX) in aqueous phase was decomposed by Ag- and Au-TiO2 photocatalyst. Photocatalytic decomposition rate, r(VX), was accelerated in the order of Ag-TiO2 > Au-TiO2 > bare TiO2 as a consequence of improving charge separation and increasing partial decomposition of VX molecular structure. It was suggested that the photocatalytic decomposition of VX molecule at the Au- and Ag-TiO2 was carried out by C-N, P-S cleavage and oxygenation.

Photocatalytic activity of graphitic carbon nitride (g-C3N4) was significantly improved by an alkaline hydrothermal treatment. The specific surface area of g-C3N4 obtained by heating melamine at 550 °C was only 7.7 m2 g−1, which was too small for it to be utilized as a catalyst for air purification. By the hydrothermal treatment with NaOH solution at 90–150 °C, the surface area was increased up to 65 m2 g−1, and the oxidation rate of nitrogen oxide (NO) under visible light (380 < λ < 480 nm) was increased by 8.6 times. XRD, ESR, elemental analysis and electron microscopy showed that unstable domains of not-well-ordered carbon nitride were removed by hydrolysis to form a mesoporous structure with a higher surface area. Deactivation of g-C3N4 was not observed during the experimental period, although a small part of carbon nitride was decomposed by self-oxidation.

Photochemical decomposition of a fluorotelomer unsaturated carboxylic acid, C3F7CFCHCOOH (1), in the presence of WO3 and an electron acceptor (S2O82- or H2O2) in water under visible-light irradiation was investigated. Under an O2 atmosphere, 1 was not decomposed either by TiO2 (P25) or WO3 alone. A combination of WO3 and H2O2 also resulted in almost no decomposition of 1. In contrast, irradiation in the presence of a combination of WO3 and S2O82- (potassium salt) efficiently decomposed 1 to F−, CO2, C3F7COOH, and C2F5COOH. The decomposition of 1 was affected by the counter cation of S2O82-: the decomposition extent was higher with K2S2O8 than with (NH4)2S2O8. The decomposition of 1 was further enhanced when the reaction in the presence of WO3 and K2S2O8 was carried out under an argon atmosphere. Under O2, the amount of H2O2 formed in the reaction solution was an order of magnitude higher than the amount formed under argon. This fact suggests that the decrease in the decomposition of 1 under O2 can be ascribed to the formation of H2O2, which consumed S2O82- and SO4-.

The specific differences on TiO2 photocatalytic decomposition rates of vaporized isopropyl methylphosphonofluoridate, sarin (GB), r(GB) as a real Chemical Warfare Agent (CWA) and vaporized dimethyl methylphosphonate (DMMP), r(DMMP) as CWA simulant in gas phase have been investigated by Gas chromatography/mass spectrometry (GC/MS) analysis in ambient. The concentration of GB molecules adsorbed at the surface of TiO2 in the dark, C-GB, was 28 times larger than C-DMMP in the dark. The r(GB) was then 3.3 times faster than the r(DMMP). The results were explained by taking into account faster hydrolysis of GB molecules at the surface of TiO2 and the larger diffusion constant of GB in the gas phase than DMMP molecules. The effect of F- adsorption at the surface of TiO2 as fluoridated surface on the TiO2 photocatalysis was also studied. (c) 2013 Elsevier B.V. All rights reserved.

The TiO2 photocatalytic decomposition of ethyl-S-dimethylaminoethyl methylphosphonothiolate (VX) as a real chemical warfare agent (CWA) in liquid phase has been investigated by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. The TiO2 photocatalytic decomposition rate, rVX, was accelerated with increase in alkalinity. The several kinds of by-products such as diisopropylamine, ethyl methylphosphonic acid, oxygenated VX and partially oxidized VX were observed. On the basis of the by-products, the TiO2 photocatalysis were proposed as the P–S, C–N cleavage and oxygenation of VX molecule carried out mainly. The difference between rVX and vaporized dimethyl methylphosphonate (DMMP), rDMMP as CWA simulant was also investigated and the rVX was 30 times faster than the rDMMP. On the basis of the decomposition mechanism of VX and DMMP molecules, the results of the acceleration of rVX in alkaline condition and of the comparison of rVX and rDMMP were also discussed.

Photocatalytic degradation of organophosphorus compounds including organophosphonic and organophosphinic acids by TiO2 immobilized silica gel in a water phase was carried out. Photocatalytic degradation of parent organophosphorus compounds and formation of intermediates were observed and the photocatalytic degradation scheme for each pesticide is proposed. Overall, the photocatalytic degradation of organophosphorus compounds in aqueous phase was estimated to form organophosphoric (organophosphonic and organophosphinic) acids as intermediates of the reaction. These organophosphoric acid intermediates were selectively adsorbed onto TiO2 surface and as a result, elution of these compounds into the aqueous phase was not observed. Similarly, after photocatalytic degradation, H3PO4 was either not observed or slightly observed as the final product. Likewise, rapid adsorption of the studied parent organophosphoric acids on TiO2 surface resulted in significant reduction in the concentration of these compounds even under dark condition. Upon UV irradiation, total organic carbon (TOC) level increased, and this is indicating the elution of some organic intermediates into the aqueous phase. However, these organic intermediates were eventually degraded with the UV irradiation.

Behaviors of N and S atoms in formation of N-doped TiO2 with a wet N-doping process were analyzed to investigate the origin of photocatalytic activity under visible light. In a titanium oxyhydroxide precursor obtained by mixing titanium oxysulfate and ammonia solutions, two types of NH3 species were formed. One was directly bonded to Ti4+ (coordinated NH3, located at 400.0eV in X-ray photoelectron spectrum), which was related to photocatalytic activity on NOx removal under visible light (λ>405nm). The other was NH3 in (NH4)2SO4 (at 401.8eV), which was unnecessary for producing the activity. During heat-treatment at 400°C, roughly half amount of the coordinated NH3 was left behind in TiO2 without changing the oxidation state of nitrogen, and the other half was released from the solid phase regardless of partial O2 pressure. A local unusual structure of TiO2, e.g. crystal defects and distortion, formed by the coordination of NH3 to Ti4+ and/or the release of NH3 seems to be an origin of the visible-light activity of N-doped TiO2. A substitutional doping of nitrogen anions (N3−) into TiO2 was not essential for the activity. The amount of SO42− in N-doped TiO2 was decreased by washing of the precursor or heat-treating the photocatalyst in CO. The activity was significantly improved by decreasing the amount of SO42− in N-TiO2.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The adsorption and photocatalytic degradation of nerve agent, isopropyl methylphosphonofluoridate, Sarin (GB) as a real Chemical Warfare Agent (CWA) on powdery Titanium dioxide (TiO2) film have been investigated using Gas chromatography/mass spectrometry (GC/MS) analysis in ambient atmosphere. We found that the ability to decontaminate GB molecules on TiO2 photocatalyst can be estimated to be 42 molecules/nm2, indicating that 1g of TiO2 photocatalyst can decontaminate 3.4mmol of GB molecules as the limitation value to maintain the photocatalytic activity. We also elucidated a plausible photocatalytic decontamination mechanism of GB at the surface of TiO2 photocatalyst on the basis of the results obtained in this study.