scholarly journals Effect of Different Radiation Sources and Noble Metal Doped onto TiO2 for Contaminants of Emerging Concern Removal

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 894 ◽  
Author(s):  
Rui C. Martins ◽  
Eva Domingues ◽  
Morgana Bosio ◽  
Margarida J. Quina ◽  
Marta Gmurek ◽  
...  
Keyword(s):  
Noble Metal ◽  
Photocatalytic Oxidation ◽  
Kinetic Constant ◽  
Contaminants Of Emerging Concern ◽  
Order Kinetic ◽  
Visible Radiation ◽  
High Production ◽  
Metal Doped ◽  
The Impact ◽  
Sunlight Radiation

Water scarcity is a worldwide problem boosted by global warming and pollution of anthropogenic origin. The contaminants of emerging concern in water sources are increasing due to the inefficiency of conventional wastewater treatments, and these should be mitigated. Advanced oxidation processes appear as suitable solutions for decontamination. The photocatalytic oxidation of the mixture of sulfamethoxazole, carbamazepine and lorazepam was investigated. TiO2 modified by Ag and TiO2 modified by Pd were used as photocatalysts to improve photoactivity. The impact of light wavelengths was examined using UVA and visible radiation as well as natural sunlight. Visible light revealed the lowest ability for decontamination in 60 min of irradiation through Ag and Pd–TiO2 photocatalytic oxidation. On the other hand, UVA and sunlight in the presence of photocatalysts were able to totally remove the contaminants. This can be related to the high production of reactive oxidative species at those conditions. The increase of the noble metal load promotes the improvement of the decontamination efficiency. The kinetic rate was analyzed for UVA and sunlight radiation for different photocatalytic conditions. The presence of a natural light source without energy costs leads to an increase in the pseudo-first-order kinetic constant. Sunlight radiation with a suitable photocatalyst can be a very good option for water decontamination.

scholarly journals Contribution of Metal Species to the Heterogeneous Photocatalytic Degradation of Natural Organic Matter

2007 ◽  
Vol 2007 ◽  
pp. 1-8 ◽  
Author(s):  
Ceyda Senem Uyguner ◽  
Miray Bekbolet
Keyword(s):  
Organic Matter ◽  
Kinetic Model ◽  
Natural Organic Matter ◽  
Photocatalytic Oxidation ◽  
Metal Species ◽  
Model Parameters ◽  
Order Kinetic ◽  
Adsorption Effect ◽  
First Order ◽  
The Impact

The role of organic matters which are high molecular weight macromolecules in natural water supplies and their subsequent removal by advanced oxidation technologies has gained importance because they posses a substantial capacity to complex dissolved metal species. The present study was conducted to evaluate the impact of aqueous Cr(VI) and Mn(II) species on the photocatalytic oxidation of humic acids as a major component of natural organic matter in aquatic systems. The photocatalytic decolorization rate of humic acid was followed by pseudo-first-order and Langmuir Hinshelwood kinetic models. The presence of aqueous Cr(VI) and Mn(II) species did not significantly alter the degradation efficiency (≤20%) in terms of first-order kinetic model. Although the impact of manganese species could be considered as insignificant, a substantial adsorption effect could be assessed as reflected by respective Langmuir-Hinshelwood kinetic model parameters.

scholarly journals Bismuth Oxyhalides for NOx Degradation under Visible Light: The Role of the Chloride Precursor

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 81
Author(s):  
Francesca Tessore ◽  
Federico Galli ◽  
Dalma Schieppati ◽  
Daria C. Boffito ◽  
Alessandro Di Michele ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Photogenerated Electron ◽  
Green Technology ◽  
Bandgap Energy ◽  
Visible Radiation ◽  
Bismuth Nanoparticles ◽  
Metallic Bismuth ◽  
Bismuth Oxyhalides ◽  
The Impact

Photocatalysis is a green technology for tackling water and air contamination. A valid alternative to the most exploited photocatalytic material, TiO2, is bismuth oxyhalides, which feature a wider bandgap energy range and use visible radiation to attain photoexcitation. Moreover, their layered structure favors the separation of photogenerated electron–hole pairs, with an enhancement in photocatalytic activity. Controlled doping of bismuth oxyhalides with metallic bismuth nanoparticles allows for further boosting of the performance of the material. In the present work, we synthesized Y%Bi-doped BiO(Cl0.875Br0.125) (Y = 0.85, 1, 2, 10) photocatalysts, using cetyltrimethylammonium bromide as the bromide source and varying the chloride source to assess the impact that both length and branching of the hydrocarbon chain might have on the framing and layering of the material. A change in the amount of the reducing agent NaBH4 allowed tuning of the percentage of metallic bismuth. After a thorough characterization (XRPD, SEM, TEM, UV-DRS, XPS), the photocatalytic activity of the catalysts was tested in the degradation of NOx under visible light, reaching a remarkable 53% conversion after 3 h of illumination for the material prepared using cetylpyridinium chloride.

scholarly journals Estimating the Impact of High-Production-Volume Chemicals on Remote Ecosystems by Toxic Pressure Calculation

2006 ◽  
Vol 40 (5) ◽  
pp. 1573-1580 ◽  
Author(s):  
Jasper V. Harbers ◽  
Mark A. J. Huijbregts ◽  
Leo Posthuma ◽  
Dik van de Meent
Keyword(s):  
Production Volume ◽  
High Production Volume ◽  
Pressure Calculation ◽  
High Production ◽  
The Impact

scholarly journals A Review of Photocatalytic Materials for Urban NOx Remediation

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 675
Author(s):  
Hugo Savill Russell ◽  
Louise Bøge Frederickson ◽  
Ole Hertel ◽  
Thomas Ellermann ◽  
Steen Solvang Jensen
Keyword(s):  
Photocatalytic Oxidation ◽  
Urban Air Pollution ◽  
Field Trials ◽  
Urban Environments ◽  
Physical Parameters ◽  
Nox Removal ◽  
Removal Efficiencies ◽  
The Impact ◽  
By Products ◽  
Photocatalytic Materials

NOx is a pervasive pollutant in urban environments. This review assesses the current state of the art of photocatalytic oxidation materials, designed for the abatement of nitrogen oxides (NOx) in the urban environment, and typically, but not exclusively based on titanium dioxide (TiO2). Field trials with existing commercial materials, such as paints, asphalt and concrete, in a range of environments including street canyons, car parks, tunnels, highways and open streets, are considered in-depth. Lab studies containing the most recent developments in the photocatalytic materials are also summarised, as well as studies investigating the impact of physical parameters on their efficiency. It is concluded that this technology may be useful as a part of the measures used to lower urban air pollution levels, yielding ∼2% NOx removal in the immediate area around the surface, for optimised TiO2, in some cases, but is not capable of the reported high NOx removal efficiencies >20% in outdoor urban environments, and can in some cases lower air quality by releasing hazardous by-products. However, research into new material is ongoing. The reason for the mixed results in the studies reviewed, and massive range of removal efficiencies reported (from negligible and up to >80%) is mainly the large range of testing practices used. Before deployment in individual environments site-specific testing should be performed, and new standards for lab and field testing should be developed. The longevity of the materials and their potential for producing hazardous by-products should also be considered.

scholarly journals Kinetic and Microhydrodynamic Modeling of Fenofibrate Nanosuspension Production in a Wet Stirred Media Mill

Pharmaceutics ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1055
Author(s):  
Gulenay Guner ◽  
Dogacan Yilmaz ◽  
Ecevit Bilgili
Keyword(s):  
Rate Constant ◽  
Kinetic Models ◽  
Multiple Linear Regression Model ◽  
Empirical Correlation ◽  
P Value ◽  
Order Kinetic ◽  
Stirrer Speed ◽  
Predictive Capability ◽  
Breakage Rate ◽  
The Impact

This study examined the impact of stirrer speed and bead material loading on fenofibrate particle breakage during wet stirred media milling (WSMM) via three kinetic models and a microhydrodynamic model. Evolution of median particle size was tracked via laser diffraction during WSMM operating at 3000–4000 rpm with 35–50% (v/v) concentration of polystyrene or zirconia beads. Additional experiments were performed at the center points of the above conditions, as well as outside the range of these conditions, in order to test the predictive capability of the models. First-order, nth-order, and warped-time kinetic models were fitted to the data. Main effects plots helped to visualize the influence of the milling variables on the breakage kinetics and microhydrodynamic parameters. A subset selection algorithm was used along with a multiple linear regression model (MLRM) to delineate how the breakage rate constant k was affected by the microhydrodynamic parameters. As a comparison, a purely empirical correlation for k was also developed in terms of the process/bead parameters. The nth-order model was found to be the best model to describe the temporal evolution; nearly second-order kinetics (n ≅ 2) was observed. When the process was operated at a higher stirrer speed and/or higher loading with zirconia beads as opposed to polystyrene beads, the breakage occurred faster. A statistically significant (p-value ≤ 0.01) MLRM of three microhydrodynamic parameters explained the variation in the breakage rate constant best (R2 ≥ 0.99). Not only do the models and the nth-order kinetic–microhydrodynamic correlation enable deeper process understanding toward developing a WSMM process with reduced cycle time, but they also provide good predictive capability, while outperforming the purely empirical correlation.

scholarly journals Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

2016 ◽  
Vol 16 (14) ◽  
pp. 9435-9455 ◽  
Author(s):  
Matthew J. Alvarado ◽  
Chantelle R. Lonsdale ◽  
Helen L. Macintyre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Visible Radiation ◽  
Submicron Aerosol ◽  
In Situ Data ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

Photodissociation of Noble Metal-Doped Carbon Clusters

2008 ◽  
Vol 112 (48) ◽  
pp. 12355-12366 ◽  
Author(s):  
B. W. Ticknor ◽  
B. Bandyopadhyay ◽  
M. A. Duncan
Keyword(s):  
Noble Metal ◽  
Carbon Clusters ◽  
Metal Doped

Bornane[2,3-b]pyrazino-fused [30]trithiadodecaazahexaphyrin. Synthesis, acid-base behavior and nickel(II) coordination ability

2017 ◽  
Vol 21 (02) ◽  
pp. 135-143
Author(s):  
Tatyana N. Lomova ◽  
Maxim S. Filatov ◽  
Mikhail K. Islyaikin
Keyword(s):  
Kinetic Constant ◽  
Macrocyclic Ligand ◽  
Racemic Mixture ◽  
Order Kinetic ◽  
Acid Base ◽  
Polydentate Ligand ◽  
Destruction Mechanism ◽  
Protonated Forms ◽  
Coordination Ability ◽  
Order Kinetic Equation

Polydentate ligand-bornane[2,3-b]pyrazino-fused [30]trithiadodecaazahexaphyrin has been synthesized by crossover condensation of the racemic mixture of (R/S)-bornane[2[Formula: see text],3[Formula: see text]-b]-2,3-dicyanopyrazine and 2,5-diamino-1,3,4-thiadiazole. Its coordination ability, acid-base behavior and stability were studied by chemical kinetics/thermodynamics, UV-vis spectrophotometry and quantum chemical DFT/B3LYP/6-31G(d,p) methods. The fourth-order kinetic equation with the kinetic constant of 3.38 × 108 s[Formula: see text].mol3.L[Formula: see text] and the association mechanism according to the Langford−Gray classification were established for the fused [30]trithiadodecaazahexaphyrin–nickel diacetate–DMF system. The stepwise protonation of macrocyclic ligand with p[Formula: see text] of -1.41 in CH2Cl2-CF3COOH mixtures at the Hammett acidity functions ([Formula: see text] changed from -2.0 to 2.0 and quantitative parameters of ligand stability in AcOH–H2SO4 mixtures was obtained. The chemical structure of protonated forms and ligand destruction mechanism have been proposed. The obtained results are of interest for development of technological regulations of complex formation and for the transition to the hetero nuclear complexes.

scholarly journals Nanophosphors-Based White Light Sources

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1048 ◽  
Author(s):  
Maura Cesaria ◽  
Baldassare Di Bartolo
Keyword(s):  
Rare Earth ◽  
White Light ◽  
Volume Ratio ◽  
Light Sources ◽  
Co Doping ◽  
New Class ◽  
Luminescence Efficiency ◽  
Metal Doped ◽  
The Individual ◽  
The Impact

Miniaturization requests and progress in nanofabrication are prompting worldwide interest in nanophosphors as white-emission mercury-free lighting sources. By comparison with their bulk counterparts, nanophosphors exhibit reduced concentration quenching effects and a great potential to enhance luminescence efficiency and tunability. In this paper, the physics of the nanophoshors is overviewed with a focus on the impact of spatial confinement and surface-to-volume ratio on the luminescence issue, as well as rare earth-activated multicolor emission for white light (WL) output. In this respect, the prominently practiced strategies to achieve WL emission are single nanophosphors directly yielding WL by means of co-doping and superposition of the individual red, green, and blue emissions from different nanophosphors. Recently, a new class of efficient broadband WL emitting nanophosphors has been proposed, i.e., nominally un-doped rare earth free oxide (yttrium oxide, Y2O3) nanopowders and Cr transition metal-doped garnet nanocrystals. In regard to this unconventional WL emission, the main points are: it is strictly a nanoscale phenomenon, the presence of an emitting center may favor WL emission without being necessary for observing it, and, its inherent origin is still unknown. A comparison between such an unconventional WL emission and the existing literature is presented to point out its novelty and superior lighting performances.

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