An investigation was carried out on the correlation between the MFT (membrane filtration time) of seawater and the particles on the membrane filter surface. The MFT was compared with the conventional indexes of suspended solid such as the turbidity and the dry weight of the particles. The particles were analyzed by X-ray fluorescence spectroscopy, scanning electron microscopy and electron probe microanalyses. The results indicated that there were two major groups which influenced the MFT in the seawater. One was inorganic particles composed of alminosilicate compounds and diatomous which were suspended solid detectable as turbidity or dry weight. The other was assumed to be colloidal and/or soluble organics which could not be represented by such ordinary values. There was found a relatively good correlation between the turbidity and the dry weight, while the correlations between the MFT and these values were not very good, especially for the low turbidity region. The organic compound was assumed to be related to the viscous liquid matter which came from seaweed and might have a surface activity. It was considered that this surfactant might have a possibility of increasing the filtration resistance of membrane filter by adsorption. Therefore, the MFT was greatly influenced by these organic components when the turbidity of seawater was on a relatively low level. This meant that the MFT could increase even when not much suspended solid existed.
Current efficiency in an electrodialyzer is decreased by water leakage, electric permeance, permeance with concentration difference, membrane fouling, current leakage and electrolysis. And currentefficiency η* can be divided into respective influencing factor to clarify these effects on current efficiency, and η* is expressed: η*=ηq·ηH2O·ηm·η1·ηe. In this report, effects of ηq, ηH2O and ηm on η* are studied theoretically and experimentally. The results of the study have clarified that ηq is expressed as functions of and where is the ratio of flow rate of leakage to raw water and is the ratio of desalinated salt weight of leakage to raw water, that ηH2O is expressed as only a function of current density in the temperature range of 15-45°C on the condition that the concentration of the raw water and desalinated water are respectively invariable, for example, in case of desalination from seawater, ηH2O has constant value (about 0.88) in range of i>2A/dm2, and that ηm in case of non-membrane fouling is 0.96 in view of membrane transport number, but ηm in case of membrane fouling by Cl2 is 0.81 for the operation time from 15 to 17 h. Therefore, the maximum value of η* in case of desalination (500 ppm: T. D. S. concentration of desalinated water) from seawater is about 0.85.
To clarify the technical problems existing in the extraction process of uranium from sea water, uranium was extracted from natural sea water, with the granulated C-Ti-OH composite adsorbent. The adsorption of uranium from sea water was carried out by using the fixed bed that had been designed in our laboratory. The uranium recovery from the sea water was 13.9% in the adsorption process of 56 d. The adsorbed uranium was eluted from the adsorbent with 0.5 N NaHCO3-0.5 N Na2CO3 soln. at 70°C. The elution recovery was 97.4% for 35 h. The uranium contained in the eluate was concentrated twenty times as much as in the anion exchage process, and then 100 times in the solvent extraction process with oxine-chloroform and TOA-kerosene. About 0.7 g of yellow cake was prepared from natural sea water, and it was identified to be pure 2UO2·NH3·3H2O by X-ray diffraction method and X-ray fluorometry.
Granulation of the composite adsorbent which consisted of hydrous titanium oxide and activated carbon was studied with PAH as a binder and the adsorptive property for uranium from sea water was examined. The strength of the granulated composite adsorbent with PAH increased as the degree of hydrazidation and amount of addition of PAH increased. The strength of the granulated composite adsorbent in break-down test by shaking method showed 98% at 10% added PAH with the degree of hydrazidation of 73%. PAH as the binder in the granulated composite adsorbent did not inhibited the adsorption of uranium from sea water, whereas the inhibitory effect of polyvinyl alcohol as a binder was found after formalization. The rate of adsorption of uranium on the granulated composite adsorbent was inversely proportional to the radius of granular. The granulated composite adsorbent was not disintegrated in elution process of uranium with acid or alkali carbonate solutions.