Kazuhiko Sekiguchi

Synergistic effects of high-frequency ultrasound on photocatalytic degradation of aldehydes and their intermediates using TiO2 suspension in water

The degradation of model substances, benzaldehyde (C(6)H(5)CHO) and formaldehyde (HCHO), were investigated under various conditions, namely, ultrasound (US) irradiation, TiO(2) photocatalysis with UV irradiation (UV/TiO(2)), and the combination of sonophotocatalysis and UV irradiation (US/UV/TiO(2)), in order to clarify the synergistic effects between US and UV/TiO(2). US and UV/TiO(2) primarily contribute to the degradation of highly hydrophobic and hydrophilic substances, respectively. However, the degradation rate was found to depend on the chemical properties and concentration of not only the substances initially present, but also their decomposition intermediates. Here, the essential information for accurately evaluating the synergistic effects on reaction rate under US/UV/TiO(2) conditions is reported, with a focus on the behavior of decomposition intermediates.

Effect of ultrasonic frequency on size distributions of nanosized mist generated by ultrasonic atomization

Ultrasonic atomization is used to produce fine liquid mists with diameter ranges below 100nm. We investigated the effect of the frequency on the size distribution of ultrasonic mist. A bimodal distribution was obtained for the mist generated by ultrasonic atomization with a wide-range particle spectrometer. The peak diameter decreased with increasing frequency, and the number concentration of the mist increased in the smaller range. We determined the relation between the size distribution of the mist and the ultrasonic frequency, and we proposed a generation mechanism for the ultrasonic nanosized mist based on the amount of water vapor around the liquid column. Increasing the power intensity and density by changing the surface diameter of the ultrasonic oscillator affected the number concentration and size distribution of the nanosized mist. Using this technique, the diameter of the mist can be controlled by changing the frequency of the ultrasonic transducer.

Decolorization of Wastewater Produced in a Pyrolysis Process by Ozone: Enhancing the Performance of Ozonation

This paper shows the results of color removal from a wastewater produced in a plastic pyrolysis process by ozonation. The influence of parameters such as temperature, reactor geometry, UVA, ozone input, and finally spraying of wastewater on performance enhancement of the decolorization process will be discussed. Due to the long residence time of O3 molecules in the gaseous phase, recycling and spraying the wastewater in a pre-filled ozone chamber show a remarkable effect on decreasing the decolorization process time. At the end of this paper, an application of “micro-bubble producer” in this field, and its advantages will be introduced.

Degradation of organic gases using ultrasonic mist generated from TiO2 suspension.

The photocatalytic degradation of organic gases with mist particles that were formed by ultrasonic atomization of a TiO(2) suspension was performed with three different ultraviolet light sources. Three aromatic volatile organic compounds (VOCs; toluene, p-xylene, and styrene) and aldehydes (formaldehyde and acetaldehyde) were chosen as model organic gases for the degradation experiment. Under UV(365) irradiation, toluene was decomposed by a photocatalytic reaction on the surface of mist particles. Under UV(254+185) irradiation, the removal efficiency and mineralization ratio of the VOC gases were higher than those under UV(365) or UV(254) irradiation. Under UV(254+185) irradiation, it was found that VOC gases were immediately degraded and converted to water-soluble intermediates by not only direct photolysis but also oxidation by OH radical, since the removal efficiency of several organic gases depended on the reaction rate with OH radical and the primary effect of generated ozone was to complete the mineralization of the intermediates. On the other hand, water-soluble aldehyde gases were rapidly trapped by mist particles before reaction on their surface. Furthermore, water-soluble intermediates that formed via the decomposition of VOC gases were completely trapped in the mist and were not detected at the reactor exit. Therefore, notable secondary particle generation was not observed, even under UV(254+185) irradiation. Based on these results as well as the size distribution of the mist droplets, it was found that primarily submicron-scale droplets contributed to the photocatalytic reaction. Lastly, we propose a mechanism for the degradation of organic gaseous pollutants on the surface of mist particles.

Size distribution and sources of 37 toxic species of particulate polycyclic aromatic hydrocarbons during summer and winter in Baoshan suburban area of Shanghai, China

The objectives of this study were to assess the size-segregated distribution and sources of 37 different species of particulate polycyclic aromatic hydrocarbons (PAHs) in a suburban area of Shanghai metropolitan City, China. The ambient particulate sampling was carried out on the rooftop of a five-stories building in Baoshan campus of Shanghai University. An Andersen high-volume air sampler was employed to collect ambient size-segregated particulate matter during summer of August to September and winter of November to December 2015. The high toxic PAHs were determined by a gas chromatography mass spectrometry. The concentrations of total PAHs in suspended particulate matter (SPM) and PM1.1 (suspended particulate matter below 1.1μm in diameter) in the suburban area of Shanghai were 4.58-14.5ng/m(3) and 1.82-8.56ng/m(3), respectively in summer, and 43.6-160ng/m(3) and 23.2-121ng/m(3), separately in winter. 1,8-Naphthalic anhydride (1,8-NA) showed the highest concentration among 37 different species of PAHs in the suburban area of Shanghai. The concentrations of high molecular PAHs (e.g. 5-6 ring PAHs) followed a nearly unimodal size distribution with the highest peaks in PM1.1. The diagnostic ration qualitatively indicated that PAHs in SPM of Shanghai were mainly derived from motor-vehicle or petroleum combustion in summer and from coal and biomass combustion in winter. According to the calculated toxicity equivalency factors based on the methods of Nisbet and Lagoy and the potency equivalency factors (PEF) recommended by U.S. EPA, the highest contributors in the total carcinogenicity of the PAHs in SPM and PM1.1 were dibenzo[a,h]pyrene (46.2% and 45.0% in summer), benzo[a]pyrene (44.4% and 43.8% in winter) and benz[j]aceanthrylene (80.2% and 83.1% in summer and 83.1% and 84.0% in winter), respectively. Therefore, benzo[a]pyrene seemed to be a lower contributor than other carcinogenic PAHs.

Behavior Of Suspended Particulate Matter Emitted From Combustion Of Agricultural Residue Biomass Under Different Temperatures

There are large quantities of waste rice husk and straw estimated around 3.9 million tons as biomass waste every year in Japan. Air pollutants emitted from exhaust gases of rice husk incineration lead to environmental damage, not only because of the influence on global environment and climate, when released into the atmosphere, but also on human health due to local air pollution. Therefore, it is necessary to effectively utilize waste rice husk and straw to reduce air pollutants. In recent years, there has been an increasing demand on the utilization of unused biomass instead of fossil oil fuel in combustors for farminggreenhouses heating during the winter season. The increasing demand will increase the running costs. In general, since these combustors are small in size, there is a lack of regulations or laws (e.g. The Air Pollution Control Act and The Waste Disposal and Public Cleaning Law) in operation for their air pollution control. So far, small size combustors are characterized by their simplicity of structure and low costs. However, they emit visible black carbon (elemental carbon) due to their poor combustion performance. In this study, we investigated that the possibility of the substitution of fossil fuel by waste rice husk and rice straw in laboratory model combustion experiments. We evaluated the emission behavior of harmful air pollutants emitted from rice husk and straw combustion by measuring carbonaceous and ionic composition of suspended particulate matter in the exhaust gases. From the analytical results we found that particulate mass concentrations reduced substantially at high temperature combustion. From the results of our study, it can be suggested that stable combustion performance under suitable conditions

Combined sonochemical and short-wavelength UV degradation of hydrophobic perfluorinated compounds

Perfluorochemicals (PFCs), which are common in the aquatic environment, are toxic substances that have high chemical and heat resistance because of their strong C-F bonds. We investigated the effect of ultrasonication and short-wavelength UV irradiation on the degradation of perfluorooctane, perfluoropropionic acid, and perfluorooctanoic acid, which are examples of hydrophobic, hydrophilic, and intermediate PFCs, respectively. The results confirmed that ultrasonication was more effective for decomposing hydrophobic PFCs and UV irradiation was more effective for decomposing hydrophilic PFCs. Therefore, defluorination of the degradation intermediates was improved by a combination of ultrasonication and UV irradiation. Our results can be applied to the decomposition treatment of PFCs that have various levels of water solubility in the aquatic environment.

Characterization of suspended particulate matter emitted from waste rice husk as biomass fuel under different combustion conditions

There are large quantities of waste rice husk, e.g. around 3 million tons are estimated as biomass waste every year in Japan. Air pollutants emitted from exhaust gases of rice husk incineration lead to very important environmental damage, not only because of the influence on global environment and climate, when released into the atmosphere, but also on human health due to local air pollution. Therefore, it is necessary to effectively utilize waste rice husk and to reduce air pollutants. In recent years, there is an increasing demand on the utilization of unused biomass instead of fossil oil fuel in combustors for farminggreenhouses heating during the winter season. This increase in the demand will increase the running costs. In general, since these combustors are small in size, there is lack of regulations or laws (e.g. the air pollution control act and the waste disposal and public cleaning law) in operation for their air pollution control. So far, small size combustors are characterized by their simplicity of structure and the low costs; therefore, they emit visible black carbon (elemental carbon) due to their poor combustion performance. In this study, we investigated if fossil fuel can be substituted by waste rice husk in laboratory model combustion experiments. We evaluated the emission behavior of harmful air pollutants emitted from rice husk combustion by measuring carbonaceous and ionic composition of suspended particulate matter in the exhaust gases. From the analytical results we found that particulate mass concentrations can be reduced substantially at high temperature combustion. Fine particle size distribution is different with combustion conditions (e.g. smoldering combustion, flaming combustion). Ionic composition is mainly

The Behavior Of Suspended Particulate Matter Emitted From The Combustion Of Agricultural Residue Biomass Under Different Temperatures

There are large quantities of waste rice husk and straw estimated around 3.9 million tons as biomass waste every year in Japan. Air pollutants emitted from exhaust gases of rice husk incineration lead to environmental damage, not only because of the influence on global environment and climate, when released into the atmosphere, but also on human health due to local air pollution. Therefore, it is necessary to effectively utilize waste rice husk and straw to reduce air pollutants. In recent years, there has been an increasing demand on the utilization of unused biomass instead of fossil oil fuel in combustors for farminggreenhouses heating during the winter season. The increasing demand will increase the running costs. In general, since these combustors are small in size, there is a lack of regulations or laws (e.g. The Air Pollution Control Act and The Waste Disposal and Public Cleaning Law) in operation for their air pollution control. So far, small size combustors are characterized by their simplicity of structure and low costs. However, they emit visible black carbon (elemental carbon) due to their poor combustion performance. In this study, we investigated that the possibility of the substitution of fossil fuel by waste rice husk and rice straw in laboratory model combustion experiments. We evaluated the emission behavior of harmful air pollutants emitted from rice husk and straw combustion by measuring carbonaceous and ionic composition of suspended particulate matter in the exhaust gases. From the analytical results we found that particulate mass concentrations reduced substantially at high temperature combustion. From the results of our study, it can be suggested that stable combustion performance under suitable conditions Energy and Sustainability IV 315 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and The Environment, Vol 176,

Investigation of condensation reaction during phenol liquefaction of waste woody materials

The liquefaction of waste woody materials in the presence of phenol and acid catalyst is a promising method for converting waste woody materials into phenolic resin. The condensation reaction during the liquefaction process is a major problem for its practical application. The effects of various reaction conditions on the extent of the condensation reaction were investigated. The residue content, molecular weight distributions and phenol concentration were measured to investigate the condensation reaction. As a result, it was observed that the intense reaction conditions caused fast liquefaction and led to a remarkable condensation reaction. It was also found that the residue content began to increase at an earlier reaction time when a more remarkable condensation reaction occurred. These results indicated that the condensation reaction was one of the causes for too much degradation of liquefi ed wood molecules under intense liquefaction. The phenol concentrations in the liquefaction products were measured to investigate their effect on the condensation reaction. It was shown that the phenol concentration was 8% lower at the end of the reaction when the condensation reaction was high. It was indicated that the drop in phenol concentration suppressed the liquefaction and promoted the condensation reaction. The addition of methanol during the liquefaction process suppressed the condensation reaction. The residue content was 11% when 50% methanol was added, while it reached 66% when methanol was not added. This can be because methanol reduced the bound phenol, which could be a reaction site of condensation