ZrO2-coated TiO2 powder was prepared using zirconium tetra-n-butoxide through the sol-gel method. Specific surface area and photocatalytic activity of ZrO2-coated TiO2 powder was measured. Crystalline phase of ZrO2-coated TiO2 powder was investigated. Specific surface area, crystalline phase and catalytic activity depended on amount of ZrO2-coated. The photocatalytic activity of TiO2 powder was decreased with increasing heat-treatment temperature at the range from 400°C to 800°C. The photocatalytic activity of 1 mass% ZrO2-coated TiO2 powder was higher than that of uncoated TiO2 powder after the heattreatment at 400°C, 600°C and 800°C, respectively. It is considered that sintering of heated TiO2 powder is depressed by coated ZrO2.
Roman concrete in Somma-Vesuviana Ruins was investigated. Internal concrete consists of the cementitious material and a big aggregate of the size from 100 to about 200 mm, and the surface concrete is composed of the cementitious material and the aggregate of the size of 30 mm or less. Big aggregates were a yellow tuff and black tuff, and the brick was used as a small aggregate. In a black tuff, Leucite, Orthoclase, and Biotite are included. In a yellow tuff, the XRD peak of Leucite and Biotite are strong, and the XRD peak of Orthoclase has become small. In the XRD pattern of brick, the peak of Orthoclase and the halo of 20-35° of the amorphous material appeared greatly. Mortar was composed of calcite and amorphous SiO2. Therefore, it was presumed for pozzolann cement that consisted of the lime or slaked lime and the volcanic ash to have been used. Carbonated concrete using pozzolann cement in the air or underground remained in the soil at a long term of 1500 years or more. The possibility for concrete to have the long-term durability was suggested.
Calcium silicate hydrates were synthesized using batch mixtures with Ca/Si molar ratio of 0.4-1.0 under hydrothermal conditions at 180-190°C. Acid resistance was evaluated by measuring the dissolved amounts of the heat-treated products at 800-1100°C when treated with hydrochloric acid solution of pH 2. Xonotlite was formed from the batch mixture with a Ca/Si molar ratio of 1.0, it transform to β-wollastonite by heat treatment, and it was found that the formed β-wollastonite easily dissolved in hydrochloric acid solution of pH 2. 1.1 nm tobermorite was formed from the batch mixture with Ca/Si molar ratio of 0.4 and 0.6, and it transformed to β-wollastonite at temperature above 1000°C, and heat-treated products hardly dissolved in hydrochloric acid solution of pH 2. β-wollastonite was formed from 1.1 nm tobermorite by heat treatment as a phase transition product with excess silica content. It was suggested that the excess silica content was deposited on the surface of β-wollastonite and it improved the acid resistance of heat-treated product.
This paper reports on the formation of gypsum dihydrate by hydration of II-anhydrous gypsum using sulfuric acid formed of sulfur oxidizing bacteria. The gypsum dihydrate formed by hydrating II-anhydrous gypsum in the medium including sulfur oxidizing bacteria. pH of the medium decreased with progress of the days and was about 1 after 15 days. Number of bacteria multiplied to about 30 times in 15 days. The concentration of sulfuric acid formed by sulfur oxidizing bacteria was approximately 0.12 mol·dm-3. In addition, it tended to be equal to the S6 medium using the sodium thiosulfate-ammonia system medium. In the case of adding II-anhydrous gypsum in the S6 medium, the hydration of II-anhydrous gypsum was slow until around 10 days, but was suddenly worse in after 12 days. The change in the average particle size of formed gypsum dihydrate was a tendency similar to relationship time and formation ratio of gypsum dihydrate, maximum particle size was approximately 85μm. The shape of formed gypsum dihydrate was plate-like or needle-like crystal. The hydration of II-anhydrous gypsum in sodium thiosulfate system medium was equal to that of the S6 medium.
A field determination method was developed for water-leachable arsenic in soil by ultrasonic extraction and Molybdenum Blue colorimetry. The extraction of arsenic from 2.0 g of soil sample with 20 ml of water was performed by ultrasonication (46 kHz, 18 W) for 30 min. The extraction was repeatable within a relative standard deviation of 10%. The water-leachable concentrations of arsenic were comparable to those obtained by the shaking extraction (6 h) used in Notification 46 of Environmental Agency of Japan. Absorbance of molybdenum blue was measured at 630 nm with a band width of 25 nm by a laboratory-made portable colorimeter with an RGB light-emitting diode. Detection limits with and without the enrichment by MIBK extraction was 0.006 mg/l and 0.012 mg/l, respectively. The proposed method was applicable for soil samples containing 0.01 to 25 mg/l of arsenic.