The rotating cylinder method was applied to investigate the mechanism of scale deposition on heat transfer surfaces. Calcium sulfate foulant was used as a representative foulant of seawater, and experimentally expected to show typical asymptotic fouling curves, asymptotic value of which decreased with an increase of fluid velocity and/or a decrease of supersaturation. A generalized fouling model was applied to estimate the mechanism of fouling formation, and verified surface process as a controlling mechanism by discussing the dependence of characteristic parameters of fouling curves on the fluid velocity. The model also suggested that the scale stiffness should depend on the temperature difference between the heated surface and the bulk solution in the case of constant surface temperature. The effectiveness of mechanical cleaning against the formed scale was quantitatively evaluated by using particle abrasion method. The removal test of the particle abrasion verified that the removing rate decreased asymptotically in inverse proportion to the overall particle load, and also that stiffness of the formed scale was more dependent on the temperature at the heated surface than on the temperature difference.
A flow injection method for the determination of fluoride ion with alfusone was studied, and the following results were obtained. 1) The linearity of calibration curve was good, and the relative standard deviation in respective ten determinations of 5mg/l of fluoride ion was 0.40%. 2) A routine sampling rate of 40 determinations per hour can be achieved with the proposed method. 3) This method can be successfully applied to the determination of fluoride ion in sea water.
Mangrove plants are distributed along coastal and estuarine areas of the sub-tropical and tropical world which include Okinawa, Japan. These are called halophytes which possess perculiar physiological mechanisms for salt control. Characteristic distribution of mangrove plants is observed as conditioned by tidal regime and salinity. Rhizophora stylosa (Japanese name: Yaeyamahirugi) is one of the mangrove species and distributed at strictly affected seawater to mangrove forest. In this study, Rhizophora stylosa was compared under different NaCl concentration of water culture. Inorganic ions and organic acids in leaves and roots parts in each cultured plant samples were analyzed, respectively. This Rhizophora stylosa grew very well at F-20 and F-50 conditions like natural growth in the mangrove forest. Leaf size was large and leaf color was also healthy green. On the other hand, at high salinity condition (F-100, 3% NaCl) leaf size of Rhizophora stylosa was small and thick. After culture, ion components of culture solution were analyzed. Concentration of K+, PO43-and NO3-ions in culture solution decreased or disappeared by absorption for plant growth. These three elements are also important for mangrove growth. Concentration of Na+and Cl-in the leaves and roots gradually increased with NaCl concentration increased in culture solution. Na+. concentration in leaf and root of F-100 was 52.34 meq and 78.30 meq, respectively. Furthermore, leaves gradually increase succulence and finally these leaves fell down for excess NaCl abandonment from plant body. Highly absorbed cations were detoxicated by organic acids in the plant. Principal organic acids found in leaves and roots were malic and oxalic acid.
A high-performance fibrous adsorbent with amidoxime group was synthesized by using a PAN fiber of 6 denier as the starting material. The activation energy of uranium adsorption was 38kJ·mol-1, and the intrinsic adsorption rate of uranium from natural seawater at 23.8°C was about 300mg of uranium per kg of dry fiber per day. The adsorbent was packed in cells of 10-mm thick honeycomb stages backed with a plastic net, and the stages were assembled into a block of 15cm height. The adsorbent was also packed in spherical shells of 20mm diam., made of a plastic net, and the balls were packed in a column of 15cm length. The honeycomb block and packed column were fixed in a cage of 80cm diam. and 15cm thickness. Then the cage was moored outside Imari bay for eight hours per day in an experimental period of five days. The amount of adsorbed uranium per unit volume of the bed showed a maximum at an optimum void fraction of the packed bed and was not much changed by the type of beds used. Pitch and roll motions were as effective as the sea current velocity for promoting penetration of seawater through the beds. The price of uranium recovered by the proposed system was estimated as ¥100,000 per kg.