By stirring polyacrylonitrile fibers with a length of 5mm and a diameter of 5 deniers in a methanolic solution of hydroxylamine, spheres having amidoxime groups (AO-spheres) have successfully been formed. The resulting spheres have well-controlled diameters (0.8-1.3cm) and apparent densities (0.1-0.2g/cm3). The yield of AO-spheres depends on the stirring speed, the ratio of the fiber weight to the solution volume, and the fiber length. The water content and apparent density of AO-spheres are affected predominantly by the stirring time (Ts). The shape stability of AO-spheres in 1M NaOH-5% NaCl correlates with the treatment time with 1M hydroxylamine (TAO); the treatment time with the alkaline solution (TA1) for the loss of fibers less than 1wt% is less than 24h for AO-spheres obtained with TAO=2h, less than 16h for those with TAO=4h,and less than 8h for those with TAO=8h. Adsorption rates of uranium on AO-spheres from seawater exhibit constant maximums for Ts<5h and decrease with an increase in Ts>5h, due tothe greater difficulty of uranium diffusion into AO-spheres prepared under Ts>5h. The AO-spheres obtained under the condition of Ts=5h, TAO=8h, and TA1=8h show the adsorptivity toward uranium in seawater of 0.72mg/g after 21days, which is almost equal to that with nonformed AO-fibers. Uranium on AO-spheres is readily eluted with 1M HCl
A solar still using a concrete slab as a solar collector was developed. Brine was filmwisely fed into the grooves of parallel polyethylene ropes under the slab onto which a porous sheet was attached. The production of distillate depended strongly on the feed rate divided into three liquid flow rate regions: dry-out, effective, and independent. The result of simulation with respect to meniscus film flow shows that the mechanism of heat transfer is due to the surface area ratio of the sheet to the meniscus film.
The ultimate biodegradability and the biodegradation rate of various surfactants in seawater were evaluated with two test methods: one is in accordance with the OECD closed bottle method; the other is a coulometer method using an oxygen consumption measuring apparatus. Surfactants used for the biodegradation tests were linear alkylbenzenesulfonate (LAS), alkylsulfate (AS), alkyl (oxyethylene) sulfate (AES), soap, alkylpoly (oxyethylene) ether (AE), alkyl polyglycoside (AG), and “ester-amide” tertiary amine salt (EAA). The surfactants tested were ultimately biodegraded by oxidation in seawater. The biodegradation rate was in the following order, AG>AES=AS=AE≥EAA>LAS=soap. The biodegradation rate of soap has often been reported to be fast in freshwater systems, but it was found in our study that its biodegradation rate in seawater was slow. It is suggested that the coulometer method is appropriate for the evaluation of ultimate biodegradation in seawater, since this method is virtually unaffected by adverse factors, in particular such as nitrification.
We determined iodine levels in samples from the process of salt making by the ICP-AES method with a flow injection device and fluorine levels by absorptiometry using alfusone, and the following results were obtained. 1) On the analysis of fluorine in high-salinity samples, the recovery ratio with pretreatment by the distillation method was greater than 93%. 2) Fluorine was not concentrated by the ion-exchange membrane method, but iodine. The permaselectivity of iodine against chloride ion with an ion-exchange membrane was approximately one. 3) A large percentage of IO3- in seawater was deoxidized to I- by the ion-exchange membrane method. 4) The iodine content of the samples in the process of concentration were almost the same as their fluorine content.