Construction Of Biologically Productive Artificial Tidal Flats With Solidified Sea Bottom Sediments

Ago Bay is a typical enclosed coastal sea that is connected to the Pacific Ocean via a very narrow and shallow entrance. The bay has been contaminated by the practice of culturing pearls, which has been occurring for the past 110 years. To address this problem, a new technology — the Hi-Biah-System (HBS) — was introduced in 2005. This product of this system, which dewaters muddy dredged sediments and reduces them to their raw materials, was used to construct a tidal flat. The purpose of this study was to evaluate the environmental conditions of the constructed tidal flat 2 years after it was built. We monitored the physico-chemical (oxidation–reduction potential, acid volatile sulphide, loss on ignition, water content, total organic carbon, total nitrogen, chlorophyll a, and particle size) and biological characteristics of five constructed tidal flats and a natural tidal flat. At the same tidal level, the physico-chemical parameters were similar among the five constructed tidal flats and the natural one. However, the biomass and macrobenthic population were higher in the constructed flat compared to the natural one. We suggest that the muddy dredged sediments generated by the HBS could provide useful materials for enhancing the productivity of the tidal coastal environment

ナノチューブ電極を用いるCO2還元/H2生成セルの高度化

application/pdf陽極酸化法により作製した酸化チタンナノチューブを用いて、アノード電極として使用し、カソードに銅金属電極を用いて、光電気化学的還元セルを構築した。水素の光電気化学的生成に応用し、水素を製造することができた。量子効率は非常に低いが、光と酸化チタンナノチューブを用いて、水素を製造できた意義は大きい。水溶液は、ギ酸水溶液を用いた。ギ酸がホールスカベンジャーとして作用したと思われる。The TiO2 nanotube as anode electrode could be fabricated by the anodization method. The TiO2 nanotube, which was fabricated by the anodization method, could be applied into the photoelectrochemical cell. The photoelectrochemical cell using the TiO2 nanotube could produce the hydrogen with high efficiency.2018年度～2021年度科学研究費補助金(基盤研究(C))研究成果報告書18K1170

Metal and Molecular Vapor Separation Analysis for Direct Determination of Mn and Cu by Atomic Absorption Detection, Free of Background Absorption

The metal and molecular vapor separation analysis (MMVSA) of solid samples with an atomic absorption detector (AA) was investigated for the direct determination of manganese and copper in biological materials. An open column made with a molybdenum tube (i.d. 1.22 mm) with three-ring supporters was developed. Pure argon as a carrier gas flowed at a flow rate of 4.0 mL min−1. An ultrasonic agitation method was used for suspending NIST standard reference material powders in water. Manganese and copper in the biological powders were completely separated from Al, Ca, Fe, K, Mg, Na, and Zn elements by MMVSA under optimal experimental conditions. Several NIST biological samples were directly analyzed with satisfactory results. It was found that manganese and copper in biological materials without interferences from matrix elements could be directly determined after only an ultrasonic agitation of the biological powders. The advantages of the slurry sampling of MMVSA are simplicity, low cost, a high speed of analysis, and rapid calibration

ナノチューブ電極を用いるCO2還元/H2生成セルの構築

application/pdf本実験では、まず、光電気化学的還元セルの基礎的なデータを取得した。続いて、電極活性や電流効率に関するデータを得た後、スケールアップを念頭に置いて、開発したセルのCO2の光電気化学的還元とH2の光電気化学的生成に対して、還元セルシステムの最適化を図った。ナノチューブ電極の特性等を調べることができ、炭酸ガスの電気化学的還元において有意義にデータを取得することができた。Carbon dioxide (CO2) is the ultimate by-product of all processes involving oxidation of carbon compounds and its increasing presence in the atmosphere. In view of the vastness of its supply, CO2 represents a potential source of C1 feedstock for the production of chemicals and fuels. The thermodynamic stability and the relative kinetic inertness of CO2 require its preliminary activation or, alternatively, the activation or modification of the substrates. Therefore, the electrochemical method appears to become one of the very suitable methods for the conversion and reduction of CO2.2015年度～2018年度科学研究費補助金(基盤研究(C))研究成果報告書15K0060

Development of Heavy Metal-Free Photocatalytic RhB Decomposition System Using a Biodegradable Plastic Substrate

The heavy-metal-free photocatalytic system, in which carbon nitride is coated on polylactic acid (PLA) as biodegradable plastic through a simple dip coating method, was used for dye decomposition under visible light irradiation. Solvent selection, solvent concentration, and the number of coatings for dip coating were investigated to optimize the conditions for loading carbon nitride on PLA. Carbon nitride cannot be coated on PLA in water, but it can be strongly coated by decomposing the surface of PLA with ethanol or chlorobenzene to promote physical adsorption and activate surface. The number of dip coatings also affected the photocatalytic decomposition ability. The photocatalytic system was able to decompose the dye continuously in the flow method, and dye (rhodamine B) was decomposed by about 50% at a residence time of 12 min (flow rate 0.350 mL/min) for 30 h

Application of Sodium Dodecyl Sulfate/Activated Carbon onto the Preconcentration of Cadmium Ions in Solid-Phase Extraction Flow System

In the present study, activated carbon (AC) surface modified with sodium dodecyl sulfate (SDS), written as SDS/AC, was applied as an adsorbent for preconcentration and determination of trace amount of cadmium ions in environmental sample waters. The SDS modification on AC was performed at the same time, while cadmium ions were concentrated in the flow system as solid-phase extraction. After the separation and preconcentration steps, cadmium retained on SDS/AC was eluted with HNO3 and was subsequently determined by flame atomic absorption spectrometry (FAAS). The analytical parameters that influence the quantitative determination of trace cadmium, such as SDS concentration, pH and volume of sample solution, eluent conditions, and interference, were optimized. At the optimum conditions, the general matrix elements had little interference on the proposed procedure. The detection limits was 17 ng·L−1, and the relative standard deviation (RSD) for 12 experiments at 10 µg·L−1 cadmium solutions was 2.8%. The developed method was applied into the analysis of environmental samples spiked cadmium

Construction of Biologically Productive Artificial Tidal Flats with Solidified Sea Bottom Sediments

Ago Bay is a typical enclosed coastal sea that is connected to the Pacific Ocean via a very narrow and shallow entrance. The bay has been organically contaminated by the practice of culturing pearls, which has been ongoing for the past 110 years. To address this problem, a new technology — the Hi-Biah-System (HBS) —, which dewaters muddy dredged sediments and changes the muddy sediments for raw materials of tidal flat, was introduced in 2005. The solidified product from the sediments with the HBS was used to construct the tidal flat. The purpose of this study was to evaluate the environmental conditions of the constructed tidal flat 2 years after its construction. We monitored the physico-chemical (oxidation−reduction potential, acid volatile sulphide, loss on ignition, water content, total organic carbon, total nitrogen, chlorophyll a, and particle size) and biological characteristics of a constructed tidal flat (five sections) and a natural tidal flat (six points). At the same tidal level, the physico-chemical parameters were similar among the constructed and the natural tidal flats. However, the biomass and macrobenthic population were higher in the constructed flat compared to the natural one. According to the findings of this study it can be concluded that the solidified products from the sediments with the HBS could provide useful materials for constructing the tidal coastal environment

Optimization of Alachlor Photocatalytic Degradation with Nano-TiO2 in Water under Solar Illumination: Reaction Pathway and Mineralization

In the present study, the photocatalytic degradation of alachlor was investigated using TiO2 under sunlight irradiation. The effects of some operational parameters, such as photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time, were optimized. The kinetics of photodegradation was found to follow a pseudo-first-order kinetic law, and the rate constant at optimal condition is 0.245 min−1. The activation energy (Ea) is 6.4 kJ/mol. The alachlor mineralization can be completed under sunlight irradiation after 10 h. The formations of chloride, nitrate and ammonium ions are observed during the photocatalytic degradation. The eight photoproducts were identified by the GC–MS technique. The photodegradation reaction pathways are proposed based on the evidence of the detected photoproducts and the calculated frontier electron densities of the alachlor structure. The photocatalytic degradation treatment for the alachlor wastewater under solar irradiation is simple, convenient and low cost