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Synthesis and characterization of ZnO photocatalyst with different morphologies
Get PDFIn recent years, pollution by persistent organic pollutants (POPs) is becoming one of the severe environmental issues which cause damage to human health. Currently, although ozone treatment has been employed for POPs removal as an advanced treatment, it has disadvantages of high costs and production of harmful byproducts. Photocatalysts have been attracting attention as one of the innovative POPs removal methods. The photocatalyst is a semiconductor that triggers an oxidation-reduction reaction by light exposure on the particle surface and can achieve mineralization of pollutants. Although TiO2 is a typical photocatalyst, ZnO has also attracted attention because of its low costs. Many researchers reported synthesis and characterization of various ZnO particles with different particle shapes and morphologies using different synthesis methods. However, comparison of their photocatalytic activity under the same experimental condition is very limited.
Therefore, in this study, we synthesized three different ZnO particles with different particle shapes and morphologies, such as flower-like, multi-shell and rod-like, and compared their particle properties and photocatalytic activities for the same degradation target compound under the same degradation condition. Samples were synthesized by a solvothermal method using Zn(NO3)2･6H2O as raw material. The particle shape was controlled by adding appropriate structure-directing agents. The flower-like, multi-shell and rod-like samples were synthesized by adding hexamethylenetetramine, L(-)-proline and ethanolamine, respectively. The photocatalytic activity was evaluated by degrading 2,4-dinitrophenol (DNP) as a model POPs.
Morphologies of the resulting samples were observed by a scanning electron microscope.Based on the SEM observation, it was confirmed that flowerlike, multi-shell and rodlike samples were obtained as expected. The result of X-ray diffraction (XRD) shows that the peaks at 2 θ = 31°, 34°, 36°, 48°, 57°, 63°, 68°, and 69° can be attributed to ZnO. This result indicates that ZnO is successfully obtained by all the synthesis methods. The results also showed that the intensity of the strongest diffraction peak of the three samples varies depending on the ZnO samples in the following order: flower-like < multi-shell < rod-like, and the rod-like sample showed a significantly strong peak intensity among the samples (approximately 15 times larger than that of the flowerlike).
On the other hand, the BET specific surface area exhibited a different order: rod-like < multishell < flower-like, and the surface area of the flower-like ZnO was more than 5 times larger than that of the other two samples. These results showed that the strongest peak intensity in XRD measurement and the specific surface area for the three samples are in a trade-off relationship. Finally, photocatalytic activity tests were carried out using 10 ppm DNP under UV light irradiation. The DNP is widely used as an indicator of the photocatalytic activity. The treated water was sampled periodically, and the DNP concentration change as a function of time was determined by measuring the absorption at 357 nm with a UV-vis spectrophotometer. It was found that the DNP degradation fitted the first-order kinetics well for all the samples and the degradation rate was in the following order: rod-like < multi-shell < flower-like. This order is similar to the order for the specific surface area and opposite to that of the strongest peak intensity. The results suggest that the highest photocatalytic activity for DNP degradati on was in the flower-like shape where ZnO contributes a very high specific surface area and not by crystallinity of ZnO.departmental bulletin pape
Examination of dietary microalgae for larval stage in the culture of Acartia steueri
Get PDFIn aquaculture and ornamental industries, copepods are recognized as preferred live feeds for marine fish larvae over commonly used organisms such as Artemia and rotifers. Marine fish larvae fed with copepods show better survival and growth. Despite obvious advantages of copepods as the live feed, their use is still limited owing to low productivity and cost-efficiency when mass cultivated.
Copepods from the genus Acartia are good candidates for a live feed because their body size, swimming behavior, and biochemical composition are suitable for many marine fish larvae which have small mouth gapes. In addition, Acartia species produce dormant eggs which can be stored and hatched to feed fish larvae. Acartia steueri Smirnov is widely distributed in the coastal waters of the western Pacific Ocean, and is an essential food source for the larvae of commercially important fish in their natural habitats.
Different dietary microalgae affect the egg production rate, hatching success, survival rate, growth rate, and the population growth of copepods. One of the underlying bottlenecks in the intensive cultivation of copepods is fatally low survival rate during their larval stages. Calanoid copepods including genus Acartia feed on live microalgae. In the present study, in order to clarify the favorable dietary microalgae for larvae of Acartia steueri, the nauplii individuals were fed with four mono-microalgal diets and one mixed-microalgal diet to measure their survival rate.
The present study conducted two experiments. In the first experiment, the nauplii hatched within 24 hours were individually reared in 6-well plates under three diet conditions (mono-diet of Tetraselmis suecica, Rhodomonas salina and Isochrysis galbana) in April 2019. Survival rate and development stages of the copepods were measured every two days. In the second experiment, the nauplii were reared in 600 mL beakers under three diet conditions (mono-diet of T. suecica, Chaetoceros gracilis, and a mixed diet of T. suecica + C. gracilis at 1:1 carbon ratio) in April 2020. Survival rate and development stages of the copepods were measured at day 10 and day 20 during the incubation duration.
In the first experiment, the survival rate at day 20 was 26.8 ± 7.2％ when fed with T. suecica, which was the highest value among the mono-microalgal diet conditions. However, only 0.6％ of individuals fed with T. suecica were developed to the adult stage (copepodid VI). In addition, the malformation at first antennas was observed from the copepodid individuals fed with T. suecica. T. suecica is well known to be rich in amino acids but with poor fatty acid content. These results might suggest that T. suecica is the favorable diet for early developmental stages (i.e. nauplii) of the copepod A. steueri, but has a nutritional problem for the later development stages of life cycle. In the second experiment, the ratio of individuals developed until adult stages was maximized under the mixed diet condition of T. suecica and C. gracilis, and this mixed diet can be considered a favorable diet for A. steueri larvae in the present study.departmental bulletin pape
A Study on Efforts to Enhance Academic Skill Acquisition in Elementary School Education: Lessons Learned from Practice Based on Value-Creating (Soka) Pedagogy
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A Consideration on the Transition of Toddler’s “Musical Expression Activities” in Kindergarten Education: Focusing on Interviews with Kindergarten Teachers from the Middle of the Showa Period to the Latter Half of the Heisei Period
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Consideration on the Principle of "Auction of Buildings on Mortgaged Lands"
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Преподавание религии и РПЦ в системе образования современной России: 1991-2021
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Cooperative learning as the core of cooperative education: Focusing on the feature explanation of the cooperative learning workshop of the Japan Association for the Study of Cooperation in Education
Get PDFThis paper was originally written in English as a book chapter appearing in “Contemporary Global Perspectives on Cooperative Learning: Theory, Research, and Practice” edited by Neil Davidson, Barbara Mills, and Robin Gills and published by Routledge Publishing in UK. For Japanese readers’ convenience I rewrite it in Japanese.
In this paper at first the development of cooperative learning in Japan is briefly explained. Particularly two major groups of Japanese cooperative learning, Association of Practitioners and Researchers on Teaching/Learning of Individual Learners for Building Citizenship and Buzz Learning Society are introduced. Secondly, the concept of developing the workshop conducted by Japan Association for the Study of Cooperation in Education is descrived. Lastly the significance of cooperative education is discussed to ensure the benefit of the new direction “Japanese-style schooling in Reiwa”.departmental bulletin pape