Three types of adsorbents, hydrous aluminum oxide, composite of active carbon and hydrous aluminum oxide, and manganese dioxide added hydrous aluminum oxide, were prepared as adsorbents of lithium from sea water. Suppression of crystallization of hydrous aluminum oxide was observed in the composite adsorbent and manganese oxide added adsorbent. Of all the adsorbents prepared, amorphous ones adsorbed lithium ion selectively from lithium enriched sea water.
This paper describes fundamental research on the recovery system of potassium from concentrated brine delivered from a seawater desalination plant by using dipicrylamine (HDPA). The research involves the measurement of solbilities of KDPA and NaDPA and the reactivity of DPA with potassium in the concentrated brine. The rate of reaction between DPA and potassium, the separation of KDPA from the solution, and the recovery of KDPA were also examined. In addition, adsorption and desorption experiments of DPA salts of polyurethan were carried out. Results obtained revealed that recovery of potassium was about 90%, and that DPA in the waste brine was recovered near to 100%.
Basic zinc carbonate-activated carbon composite adsorbents were prepared under various conditions. Chemical composition of the composite adsorbents was determined by chemical analysis, X-ray diffraction, thermal analysis, and IR study. Most products revealed the same pattern of X-ray diffraction and the other properties as the basic zinc carbonate (ZnCO3·3Zn (OH)2·H2O). A new phase which had different X-ray pattern and higher decomposition temperature was found in some cases. Relating to the solubility and adsorption capacity of uranium, there was no distinct difference between this new phase and ordinary basic zinc carbonate composite adsorbents.
Mixed solution of aqueous 0.25 N NaCl and aqueous 0.25 N CaCl2was electrodialyzed using a small electrodialyzer. Cation exchange membranes were treated by a reagent of organic electrolyte with applied current or without applied current. When the membranes were treated with applied current, permselectivity coefficientTCaNadecreased remarkably, but dissociation of water occured readily on the membrane surfaces. Treatment without applied current showed a few decreases inTCaNa, but dissociation of water scarcely occured. Electric resistance of the treated membrane increased with the increase of the ratio of bivalent ions in the solution. This phenomenon was considered to depend on the increase of the electric resistance of the membrane and the reagent layer formed on the membrane surface. In order to evaluate the effects of electric field in the treatment, Nernst-Planck equation was applied and transport of reagent ions across a diffusion layer in desalted side of the membrane was examined. Consequently, it was understood that the concentration of the reagent in the reagent layer increased with the increase in current density, so that electric field enhanced the effects of the treatment.
Sea water was electrodialyzed by a filter-press type electrodialyzer (effective membrane area: 5 dm2), and cation exchange membranes were treated by means of addition of reagent continuously or intermittently into feed sea water. By the treatment,ε(=Normality of Cl--Ca2+-Mg2+in the concentrate/Normality of Cl-in the concentrate) exceeded 0.99, and permeation of bivalent cations through the membranes was prevented effectively, but at the same time voltage drop per unit cell increased with time. When the treatment was continued,ε attained was apt to decrease, and to increase ε gradually became difficult.