Decomposition Of Chemicals Research Articles

Hybrid graphenic and iron oxide photocatalysts for the decomposition of synthetic chemicals

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that resist degradation, posing a significant environmental and health risk. Current methods for removing PFAS from water are often complex and costly. Here we report a simple, cost-effective method to synthesize an iron oxide/graphenic carbon (Fe/g-C) hybrid photocatalyst for PFAS degradation. This photocatalyst efficiently degrades perfluorooctanoic acid (PFOA), a common type of PFAS, achieving over 85% removal within 3 hours under ultraviolet light. The catalyst also maintains high degradation rates over extended periods, demonstrating its stability and potential for long-term use. This innovative approach offers a promising solution for addressing PFAS contamination in water, contributing to a cleaner and healthier environment.

CFD modeling of a mini-pilot scale CO2 hydrogenation to hydrocarbons reactor using both direct and indirect pathway-based kinetic model

Both indirect CO2 hydrogenation (reverse water gas shift (RWGS) followed by CO-based Fischer-Tropsch synthesis (FTS)) and direct CO2-based FTS were considered for CO2 hydrogenation, and a kinetic model for the chain-length distribution of hydrocarbon products was developed. For independent estimation, the kinetic parameters were estimated by fitting the experimental data using powder catalysts under various conditions, mainly including CO/CO2 ratios. The contribution of indirect CO2 hydrogenation (RWGS followed by CO-FTS) was more favorable than that of direct CO2-FTS, and CO2 conversion and product selectivity were significantly dependent on the temperature and hydrogen fraction. The effectiveness factor was estimated for the pellet-type catalysts, and values less than one validated the existence of mass-transfer resistance. Computational fluid dynamics (CFD) modeling was used to simulate the three-dimensional thermal behaviors of a mini-pilot-scale reactor with a substantially large diameter loaded with a pellet-type catalyst and inert materials. Both a low catalyst loading in the early stage of the reactor and the use of an additional inner cooling tube showed a stable temperature profile, with the peak temperature maintained below 350 °C (the critical temperature to prevent the thermal decomposition of chemicals) and fast heating of cold feed in the early stage. The CFD results with no inner tube showed thermal runaway in the second reactor, and the simulation with arbitrarily reduced heat of the reaction (70 % of the actual value) resulted in a peak temperature higher than 410 °C. Further quantitative analysis indicated that the no-inner-tube case's reduced heat transfer area per unit volume was responsible for its thermally unstable behavior.

АНАЛІЗ ТРИБОЛОГІЧНИХ НАНОМАТЕРІАЛІВ ДЛЯ ПІДВИЩЕННЯ ЗНОСОСТІЙКОСТІ І ДОВГОВІЧНОСТІ МЕХАНІЧНИХ КОНТАКТУЮЧИХ ПОВЕРХОНЬ ДЕТАЛЕЙ МАШИН І МЕХАНІЗМІВ НА ОСНОВІ ОНТОЛОГІЧНОЇ СИСТЕМИ ПІДТРИМКИ ПРИЙНЯТТЯ РІШЕНЬ

The object of research is tribological nanomaterials (TrNMs), which are used to improve the qualities of the mechanical contacting surfaces of mechanical components. The goal is to create Decision Support Systems (DSS) based on the ontological system when choosing the TrNM. It was carried out an analysis of existing studies and publications as to the use of TrNM, which are available on the market of Ukraine and European countries. The analysis showed that TrNMs are classified according to the friction surfaces main features and their purpose. It has been determined that the use of TrNM shows a significant technical and economic effect, as the product service life extents and also fuel consumption decreases due to the reduction of the friction coefficient. It was found that an important consideration when choosing that or another TrNM should be their sustainability, in terms of their environmentally friendly manufacturing and use on mechanical components. It is noted that there is a problem of the existing TrNM classifiers and their substantiating, since their formation lags behind the dynamics of scientific and technological progress. It was reasoned expediency of using an Ontology-Based Decision Support Systems (OBDSS) regarding the selection of TrNM for improving the performances of the mechanical components contacting surfaces. The following results were obtained. According to the analysis of the current interest modern TrNMs and their characteristics, the technologies for the TNMs applying have been considered: "KESON" with the filling of on the friction surfaces micro-valleys with the formation of anti-friction, wear-resistant and adhesive films (coatings), as well as technologies for the use of metal conditioners "Fenom", "ER", "SR3" and "Militec-1" additives, which extend the product service life without overhauls, and remetallizing agents "Lubrifilm" and "Megaforce" with their effect of "non-wear-out-ability". It was found that the main disadvantage of such TrNMs is a pollution of the environment, namely of drinking, ground and surface water. The solution to the environmental issue is possible due to the use of nanodiamonds as a specific universal nanocarbon TrNM, which has the properties of decomposition of harmful organic chemicals. Their “representatives” are "Lubrifilm Diamond Run Ln", "Nanodiamond Green Run", nano additives "Fenom Nanodiamond Green Run" (based on nanodiamonds), "Fenom Old Chap" (based on bentonite nanoparticles), "Renom Engine Nanoguard" (for motor oils) and "Renom Gear Nanoguard" (for transmission oils). To facilitate the choice of TrNM for improving the performances of the mechanical components contacting surfaces, the OBDSS is proposed. Conclusions. The scientific novelty of the obtained results is as follows: it has been created the OBDSS, which takes into account the peculiarities and characteristics of TrNM according to the customer needs, which able to narrow the search range and reduce the time for TrNM selection. The presented materials can be useful when conducting the theoretical and experimental studies on the mechanical components service life in the field of mechanical engineering.

Mammalian toxicity of trifluoroacetate and assessment of human health risks due to environmental exposures.

While trifluoroacetic acid has limited technical uses, the highly water-soluble trifluoroacetate (TFA) is reported to be present in water bodies at low concentrations. Most of the TFA in the environment is discussed to arise from natural processes, but also with the contribution from decomposition of environmental chemicals. The presence of TFA may result in human exposures. For hazard and risk assessment, the mammalian toxicity of TFA and human exposures are reviewed to assess the margin of exposures (MoE). The potential of TFA to induce acute toxicity is very low and oral repeated dose studies in rats have identified the liver as the target organ with mild liver hypertrophy as the lead effect. Biomarker analyses indicate that TFA is a weak peroxisome proliferator in rats. TFA administered to rats did not induce adverse effects in an extended one-generation study and in a developmental toxicity study or induce genotoxic responses. Based on recent levels of TFA in water and diet, MoEs for human exposures to TFA are well above 100 and do not indicate health risks.

Characterization of Tidally Accumulated Plastic Waste and the Effect on Mangrove Ecosystems at Eagle Island, Niger Delta, Nigeria

Numbere, A.O. and Aigberua, A.O., 2023. Characterization of tidally accumulated plastic waste and the effect on mangrove ecosystems at Eagle Island, Niger Delta, Nigeria. Journal of Coastal Research, 39(2), 275–283. Charlotte (North Carolina), ISSN 0749-0208. Plastic pollution has become a global problem with the proliferation of numerous plastic goods. This study hypothesized that accumulated plastic waste will have a negative effect on the mangrove ecosystem and associated organisms. The study was performed in a sand-filled and deforested mangrove forest at Eagle Island, Niger Delta. Ten soil samples (n = 10) were collected under and around accumulated plastic waste at five different georeferenced sites. Samples of fish, crab, plastic, and foil from each site were collected and sent to the laboratory for physicochemical analysis of total hydrocarbon content (THC) and heavy metals, i.e. zinc (Zn), lead (Pb), and cadmium (Cd), using the HACH DR 890 colorimeter (wavelength 420 nm) and microwave accelerated reaction system (MARS Xpress, North Carolina, U.S.A.), respectively. Furthermore, microbial analysis was completed for the soil samples. A germination experiment was conducted in the laboratory using seedlings of Rhizophora racemose and Rhizophora mangle grown in plastic and nonplastic waste soils. The results show that no significant difference occurs in THC and heavy metal concentration in surface soils, subsurface soils (F1,30 = 1.83, P = 0.186), and soils collected around plastic waste (F3,28 = 0.60, P = 0.619). In contrast, a significant difference occurs in seedling growth between the control and plastic soils (F4,200 = 65.24, P < 0.001). Microbial population showed significant difference horizontally, i.e. some distance away from plastic waste (near, middle, and far; F3,11 = 3.86, P = 0.04) but not vertically (surface vs. subsurface; F1,11 = 4.60, P = 0.055). These results indicate that chemicals in plastic waste can migrate outwardly to contaminate neighboring organisms. Thus, plastic waste should be quickly removed from the forest to prevent its decomposition and deposition of chemicals that will move up the food chain, affecting humans who consume seafood.

Shock-tube study on high-temperature CO formation during dry methane reforming

The use of natural-gas-fueled combustion engines at unusual operating conditions to provide electrical and/or chemical energy on demand emphasizes the need for fundamental research on decomposition and formation of base chemicals at these conditions. In this work, the CO formation behind reflected shock waves from the pyrolysis of CO2/CH4 mixtures was investigated for the first time in the context of engine-based dry methane reforming, to understand the interaction of CO2 and CH4 at high temperatures and to test the validity of literature reaction mechanisms. Different CO2/CH4 mixtures at atmospheric pressure and temperatures between 1900 K and 2700 K were investigated. Time-resolved CO measurements were performed by laser absorption using a quantum cascade laser.With increasing CO2 addition later reaction onset was observed, showing a reduction in the overall reactivity. Rate of production and sensitivity analyses highlight competing reactions in the pyrolysis and oxidation pathways and that the number of available H radicals is limited, which is attributed to the reduced reactivity. However, the analysis shows that CO2 is also a source for OH radicals (via CO2 + H ⇌ CO + OH), which enhance methane decomposition. The comparison with literature reaction mechanisms showed that none of the tested mechanisms can perfectly predict the time-resolved CO formation, highlighting the need for the validation of detailed kinetics models under nontypical conditions.

Consequence of hot electron of Au and PbS shell thickness on photo‒electrochemical and catalytic activity of ZnO@Au@PbS nanorods for decomposition of toxic organic chemicals and Cr(VI) reduction by UV-to-near-infrared photon harvesting

In this research work, we have synthesised ZnO@Au@PbS nanorods (NRs) with different shell thickness by a facile chemical method. On introduction of Au nanoparticles (NPs) and PbS shells, the defect emission of ZnO NRs quench and the charge separation process enriches. Under simulated solar light irradiance the photoconductivity and charge transfer efficiency also escalate with Au NPs and PbS shell along with enhancing photocatalytic degradation of organic contaminant. The excitation wavelength dependent catalytic activity confirmed the significant enrichment in photocatalytic activity owing to the synergistic influence of Au NPs and PbS coating on ZnO NRs. The effect of aqueous solution pH and PbS shell thickness on photocatalytic reduction of Cr (VI) has been also explored. The possible charge transfer mechanism during the photocatalytic activity of ZnO@Au@PbS NRs is also proposed and analysed. The catalytic activity, stability and recyclability results revealed that ZnO@Au@PbS NRs are highly favourable and reusable for the environmental remedies.

Correlation of hydrogen generation and optical emission properties of plasma in water photolysis on perovskite photocatalysts

Photocatalytic decomposition of organic materials-contained aqueous solution is assessed using a plasma discharged into the liquid directly. The correlation of H2 generation and optical emission spectroscopy is discussed in terms of photocatalytic H2 production using plasma and photocatalysts. Variations of the active species are evaluated according to the conditions of the plasma in the liquid phase. The optical emission spectra vary according to the plasma discharging conditions in the liquid phase. The intensities of the OH· peaks at 309 nm increase with the addition of ethanol or acetaldehyde in water. The highest intensities and rate of H2 evolution are observed at a 10% acetaldehyde concentration in the aqueous solution. The rates of H2 evolution in the ethanol or acetaldehyde solution correspond to the concentration of OH· in the solution. The photocatalytic reaction using liquid plasma generates hydrogen at the same time as the decomposition of the organic chemicals. The rate of hydrogen evolution in aqueous solutions containing the organic chemicals is higher than that in pure water. This is because hydrogen is further generated due to hydrogen generation by photolysis of the organic chemicals. CaTiO3 perovskite photocatalyst shows better photocatalytic activity than TiO2. Ni loading on the photocatalyst lead to an increase in H2 production.

DPV-assisted understanding of TiO2 photocatalytic decomposition of aspirin by identifying the role of produced reactive species

A TiO2/UV photocatalytic process generates various reactive species via different oxidation and reduction routes and thus the contribution of such reactive species to the decomposition of organic chemicals in water has been unclear. In this study, decomposition of acetylsalicylic acid (ASA) as a probe was performed to find the specific role of charge carriers (ecb− and hvb+) and primary active species (such as O2−, OH, HO2, and H2O2). Differential pulse voltammetry (DPV) was introduced as an in-situ fast electrochemical method to identify produced intermediates. The study revealed that hydroxyl radicals (OH) produced by reduction of oxygen with ecb− and subsequent primary reactions (reduction pathway) play the major role in the photocatalytic decomposition of ASA, in comparison to direct oxidation of OH− or ASA by hvb+ (oxidation pathway). The in-situ DPV analysis probed that sequential OH addition to the ASA aromatic ring is the favorable oxidation mechanism.

Characteristics of DC or Pulsed-Type High-Electric Field Plasma and its Application to Air Cleaning System

DC or pulsed-type high-electric field plasma (HEFP) is investigated. Here, HEFP means that no discharges take place in atmospheric environment, and strong electric field less than about $3 \times 10^{6}$ v/m is produced to accelerate free electrons to high energy for decomposition of chemicals, water vapor, or killing bacteria. In order to produce HEFP, two types of high-voltage exciter such as: 1) short rise time pulsed-type high voltages or 2) dc high voltages are used. The phenomena observed are slightly different between two types of high voltages in addition to the consumed electric power. The main purposes of the present studies are to show the typical characteristics of HEFP, including trapping of microdust particles with diameter $0.3~\mu \text{m}$ or larger, in addition to decomposition of chemicals and sterilization. The dust particles are perfectly trapped by adding HEFP with dc voltages, while in the case of pulsed HEFP, 100% trapping of dust particles was not observed at present. The decomposition of chemicals and bacteria sterilization is confirmed in both HEFP structures. These phenomena are applied to make new type of air cleaner working in the rooms such as private small rooms or hospitals with many patients staying at the same time or in the moving vehicles.

Fuel gas production from dusty tar pyrolysis

ABSTRACTDusty tar is an undesired product obtained from a coal pyrolysis/combustion system. Thermal conversion of dusty tar into fuel gas was studied with a fixed-bed reactor. It is found that C2-C5 hydrocarbons are mainly derived from the cracking of long-chain aliphatics, while CH4 from the decomposition of long-chain aliphatics and alkyl-substituted aromatic chemicals. The yield of the gas product increases monotonously, but the heating value of gas gradually decreases as temperature increases from 400 to 950°C. Decomposition of chemicals with a boiling point over 360°C contributes to 50–90% C1-C5 hydrocarbons and COx when pyrolysis temperature is lower than 600°C.

Surface Engineering of CdS Quantum Dots for Photocatalytic Applications under Direct Sunlight

AbstractThe photocatalytic ability of materials is globally studied and has many applications in the field of water purification, water splitting to produce hydrogen fuel and decomposition of toxic chemicals. Herein, we present CdS quantum dots (QDs) based efficient photocatalyst for potential photocatalytic applications by modifying its surface with different capping ligands or thin ZnO shell. For this purpose, we have prepared CdS quantum dots by passivating its surface with 3‐mercaptopropionic acid (MPA), diphenylamine (DPA) and sodium succinate (SS) as capping agents. Additionally, Zn2+ doping or thin ZnO shell was grown in‐situ on CdS cores with varied molar concentrations to observe its effect on photocatalytic activity. The study includes both the synthesis and characterization of the products along with their photocatalytic activity under direct sunlight (75000‐90000 Lux). The effect of surface passivation of CdS QDs on their photocatalytic activity is discussed in detail. We also propose the possible mechanism for degradation of methylene blue using surface engineered CdS QDs.

Coupling effects of silica fume and steel-fiber on the compressive behaviour of recycled aggregate concrete after exposure to elevated temperature

The use of recycled concrete aggregates in structural concrete is a sustainable solution to deal with the construction and demolition waste. This technology reduces serious impact on the ecological environment caused by the shortage of natural mineral resources. The aim of present study is to assess the coupling effects of silica fume and steel-fiber on the compressive performance of recycled aggregate concrete (RAC) under elevated temperatures. A total number of 90 cylindrical concrete specimens are prepared and tested under axial compression, after heating by elevated temperatures. Comprehensive studies are conducted on the temperature dependence of compressive strength, elastic modulus, and toughness. The degradation mechanisms of recycled concrete are also examined by scanning electronic microscopy (SEM) study. It has been found that the evaporation of water and the decomposition of hydro chemicals in concrete are the main reasons for the reduction of RAC compressive performance from 25 °C to 400 °C and from 400 °C to 800 °C, respectively. The compressive performance of RAC decreases with increasing temperatures, but the addition of steel fibers significantly counteracts this negative impact. Thanks to the superior coupling effect of silica fume and steel fibers, the steel-fiber RAC (SRAC) with silica fume shows excellent compressive behaviour under high temperature environment. This study provides important engineering insights into the use recycled concrete in high temperature environment.

Synthesis and characterization of TiO2 films onto AISI 304 metallic meshes and their application in the decomposition of the endocrine-disrupting alkylphenolic chemicals

This contribution describes the influence of the ratio of polyvinyl alcohol (PVA), TiO2 and wire opening of metal meshes for the construction of a structured catalyst with a uniform coating, that present high adherence and photocatalytic activity. The best coating results were observed for a PVA/TiO2 mass ratio of 0.37 and mesh opening of 546 µm. This coating exhibited a uniform distribution, high adherence and the maintenance of anatase and rutile phases. These aspects can be related to three variables: (i) the structure of the stainless-steel metal mesh, (ii) the thermal pretreatment and (iii) the amount of organic additive (PVA/TiO2 ratio) employed in the suspensions. The most important achievement of this work was the fabrication of a structured catalyst with excellent stability, without losing activity for the degradation of endocrine-disrupting nonylphenol ethoxylate (NP4EO) in synthetic solution, without poisoning of the catalytic surface. In fact, the results showed that even with a real wastewater matrix, a high photocatalytic activity for NP4EO degradation (91%) was obtained, meaning that this structured catalyst can be applied to solve serious environmental problems as the contamination by endocrine-disrupting NP4EO, without subsequent catalyst recovery and recycle steps.

Effect of pH on selective decomposition of target water contaminants onto porous TiO2 photocatalyst

Abstract Non-selectivity of TiO2-based photocatalysis is a known drawback of this technology for full scale water treatment applications. It results in significant decline in decomposition of toxic target contaminants when other non-toxic organic compounds such as natural organic matter (NOM) compete in the reaction. Previously, size exclusion of large NOM onto the mesoporous structure of TiO2 photocatalyst was proven to improve the selective decomposition of small size target chemicals. In this study, manipulation of reaction pH as a crucial parameter in governing the adsorption and decomposition of organic chemicals was combined with the size exclusion of NOM. The effects of size-based adsorption/exclusion and pH-dependent electrostatic attraction/repulsion were investigated by using humic acid as model NOM and ibuprofen and methylene blue as model target contaminants. Adsorption and decomposition of the targets were dependent on their hydrodynamic size and ionization state. Mesoporous TiO2 suppressed physical access of large NOM onto its surface while reaction pH influenced the surface charge of TiO2 and the speciation of the chemicals and thus controlled their adsorption and decomposition. The results imply that selecting a proper pH can significantly improve selective decomposition of a target onto porous TiO2 in the presence of NOM.

Sb2S3 grown by ultrasonic spray pyrolysis and its application in a hybrid solar cell.

Chemical spray pyrolysis (CSP) is a fast wet-chemical deposition method in which an aerosol is guided by carrier gas onto a hot substrate where the decomposition of the precursor chemicals occurs. The aerosol is produced using an ultrasonic oscillator in a bath of precursor solution and guided by compressed air. The use of the ultrasonic CSP resulted in the growth of homogeneous and well-adhered layers that consist of submicron crystals of single-phase Sb2S3 with a bandgap of 1.6 eV if an abundance of sulfur source is present in the precursor solution (SbCl3/SC(NH2)2 = 1:6) sprayed onto the substrate at 250 °C in air. Solar cells with glass-ITO-TiO2-Sb2S3-P3HT-Au structure and an active area of 1 cm2 had an open circuit voltage of 630 mV, short circuit current density of 5 mA/cm2, a fill factor of 42% and a conversion efficiency of 1.3%. Conversion efficiencies up to 1.9% were obtained from solar cells with smaller areas.

Effect of UV-LED wavelengths on direct photolytic and TiO2 photocatalytic degradation of emerging contaminants in water

Ultraviolet (UV) irradiation is known to be effective for chemical oxidation and disinfection of water and wastewater. Recently, light emitting diode (LED) has been recognized as a cost-effective, environmentally friendly, and sustainable source of UV to replace conventional mercury lamps, so-called UV-LED. Less is known about the effectiveness of UV-LEDs, i.e., UVA, UVB, and UVC in comparison, for the decomposition of recalcitrant organic chemicals. In this study, direct photolytic decomposition and TiO2 photocatalytic decomposition of model pharmaceuticals, including acetaminophen (ACT), diclofenac (DCF), ibuprofen (IBP), and sulfamethoxazole (SMX), was tested, and the effects of different UV-LED wavelengths on their decomposition were investigated. UV wavelength was found to be a more important parameter for the decomposition than light intensity. Shorter wavelength UV in order of UVC>UVB>UVA was more effective for the decomposition of the pharmaceuticals. Photocatalytic decomposition was much more significant than photolytic decomposition. Decomposition kinetics of the pharmaceuticals followed SMX>DCF>IBP>ACT, reflecting their molecular structures. Results on the mineralization of the pharmaceuticals also supported the observed trends for their disappearance. The investigation was resumed with microcystin-LR (MC-LR), a known lethal biological toxin often found in water resource, and the similar result to the pharmaceuticals was also observed for MC-LR. This study and the consequent results would facilitate applications of UV-LEDs for the treatment of water contaminated with recalcitrant toxic chemicals.

Decomposition of organic chemicals by zeolite-TiO2 nanocomposite supported onto low density polyethylene film under UV-LED powered by solar radiation

Zeolite-TiO2 nanocomposite was synthesized to maximize its surface area for high reactivity and then immobilized onto a low density polyethylene film to enhance its mechanical stability and application practicality. Ultraviolet light emitting diode (UV-LED) was applied instead of traditional UV lamps to activate the TiO2 composite. Photovoltaics was also introduced to utilize solar radiation as an energy source of UV-LED. The reactivity of zeolite-TiO2 nanocomposite under UV-LED powered by solar radiation was evaluated in the presence of potassium persulfate (K2S2O8) as an oxidant to decompose reactive dyes and pharmaceuticals (reactive black 5, cefiximetrihydrate, and phenazopyridine). Reactivity of various chemical, photolytic, photochemical, and photocatalytic decomposition processes and routes was in order of UV-LED≈TiO2≈zeolite≈zeolite-TiO2≈UV-LED/zeolite≈UV-LED/TiO2<K2S2O8<<TiO2/K2S2O8<zeolite-K2S2O8<UV-LED/K2S2O8<UV-LED/zeolite-TiO2<UV-LED/TiO2/K2S2O8<UV-LED/zeolite/K2S2O8<<zeolite-TiO2/K2S2O8<UV-LED/zeolite-TiO2/K2S2O8. Use of zeolite-TiO2 nanocomposite contributed to enhanced decomposition of target contaminants more significantly than any other factors such as addition of persulfate and introduction of UV-LED. Effect of persulfate concentration, absorbance spectral changes and discoloration, and reusability of zeolite-TiO2 nanocomposite were also discussed. Since all devices including UV-LED were powered by a photovoltaic module and organic decomposition was successful, the photovoltaics-powered UV-LED photoreactor was proposed as a sustainable, self-powered, and practical point-of-use decontamination system to decompose water contaminants under solar radiation.

Decomposition of Organic Chemicals in the Air and Inactivation of Aerosol-Associated Influenza Infectivity by Photocatalysis

Efficiency of photocatalysis depends on the surface area and materials, and we have prepared a porous ceramic substrate coated with nanosized-TiO2 for a photocatalytic air cleaner. The surface of the porous ceramic was coated with nano-sized TiO2 and total surface area of the board (30 × 30 × 1 cm) was 7,432 m2, being 14,864 m2 as the total area in the cleaner consisting of two boards and intervened black lamps. Eighty percent of 5 ppm acetaldehyde was decomposed and generated 8 ppm of carbon dioxide for 3 hours efficiently and continuously by passing through the TiO2-coated ceramic (5 × 10 × 1 cm) under black light. Particulate dioxins (40 pg/m3) and gaseous dioxins (16 pg/m3) were removed by 7.5 and 2.8 pg/m3 by passing through four TiO2-coated ceramic (30 × 30 × 2 cm) under black-light, indicating about 80% of dioxin was decomposed by the photocatalysis. This photocatalysis system was applied for inactivation of influenza aerosol. Influenza infection is spread efficiently by inhalation of aerosol-associated influenza virus. The aerosol-associated infectivity produced by nebulizer in a 754 liter cubic space was more than 10,000 plaque-forming units and was detectable for up to 30 minutes. The aerosol-associated infectivity of influenza virus was eliminated within five minutes by a photocatalytic air cleaner. The infectious aerosol-associated influenza would accumulate by the continuous production by cough and sneeze in the closed space, resulting in the efficient influenza infection. Thus a photocatalytic air cleaner efficiently decomposed organic chemicals including acetaldehyde and dioxins and inactivated aerosol-associated influenza virus infectivity.

Influence of Orifice Shape on Reaction Rate by Hydrodynamic Cavitation

Hydrodynamic cavitation is expected to apply to the decomposition of chemicals and the disinfection in wastewater. In this study, the effects of upstream pressure, hole diameter and shape of orifice plate on the reaction rate of I3- formation were investigated. The reaction rate increases with increasing upstream pressure of orifice plate. The reaction rates have maximum values, when hole diameters of orifice plate are 2.7 mm at the upstream pressure of 0.9 MPa gauge and 3.0 mm at 0.7 MPa gauge. The reaction rate increases in the order of triangle &lt; square &lt; hexagon &lt; circle shaped hole of orifice plate at the same hole area.