Synthetic inorganic ion-exchange materials. XXXIV. Selective separation of lithium from seawater by tin(IV) antimonate cation exchanger

Tin(IV) antimonate (SnSbA) cation exchanger showed an extremely high selectivity for lithium ions compared with other alkali metal ions. The equilibrium distribution coefficients, K_d, were determined at different concentrations of lithium and sodium ions in hydrochloric acid media by batch technique. The K_d values of lithium ions increased with decreasing concentration of lithium ions in the solution, while those of sodium ions were almost independent of sodium concentrations. This behavior can be used to good advantage for the selective separation of lithium at low concentration from sodium ions at high concentration. A successful separation of lithium ions from seawater can be achieved by a column of the SnSbA exchanger in hydrogen ion form. The SnSbA exchanged with lithium and sodium ions can be regenerated using 10 M nitric acid solution as an eluent. Therefore, the SnSbA exchanger can be used repeatedly for the separation of the lithium ions from seawater.     

Preparation of ion exchange membranes by plasma polymerization. I

Plasma polymerizations of three kinds of amines, γ-aminopropylethoxydimethylsilane (APEMS), allylamine (AA), and pyrole (PY), were investigated by IR and XPS analysis. Plasma-polymerized films were deposited on porous substrates, and ion exchange abilities of the composite membranes were measured. When APEMS were used as the monomer, the polymer retained the chemical structure of the monomer, amino groups. However, when AA and PY were used as the monomers, the plasma polymers contained a larger amount of amido structures than did the polymer of APEMS. Each membrane had ion exchange ability. In particular, the membrane prepared from APEMS showed superior ion exchange ability, anion permselectivity and conductivity, in acidic solutions. This property was attributed to the chemical structure of the polymer from APEMS retenting amino groups. The ion exchange properties of the membranes depended on the pH of the solution. In particular, the membrane of APEMS showed high membrane potential and low electric resistance only in a narrow pH region due to the weak basicity of amines and the hydrophobic property of the polymer.     

Redox reaction of tri(2-deoxy-2-L-ascorbyl)amine. Formation of a persisting free radical species in water

Electrochemical studies showed that tri(2-deoxy-2-L-ascorbyl)amine ($\text{1}$), a new compound isolated as one of the products of reaction of dehydro-L-ascorbic acid with phenylalanine (with added L-ascorbic acid) in ethanol, is oxidized in aqueous solution in two reversible one-electron transfer steps, on mercury or platinum electrode. The first step occurs through the dianion, and its product is an unusually stable blue anion radical giving a characteristic ESR signal. The product of the second step of oxidation is labile and is slowly converted into the oxidized form of di(2-deoxy-2-L-ascorbyl)amine, presumably by hydrolysis with splitting of L-ascorbic acid.     

The vapour pressures and heats of sublimation of model disperse dyes

The vapour pressures and heats of sublimation of 23 model disperse dyes have been measured by the vapour saturation method (modified transpiration method). The data obtained were in good agreement with those produced by the other investigators using the effusion method. The heats of sublimation are discussed in terms of molecular structure.     

Influence of powder characteristics of bulk substance with pharmaceutical processing

BACKGROUND: Significant changes in cardiac preload and afterload are generated by a number of factors present during the operation of high performance aircraft. These include high levels of +Gz, positive pressure breathing and anti-G straining maneuvers. Centrifuge subjects are exposed to these same factors in doses that are comparable to their operational counterparts. The question of whether such exposures produce long-term adverse effects on the heart has not been definitively answered. METHODS: In an effort to further address this issue, a longitudinal study was conducted on 18 newly recruited centrifuge panel members (7 males and 11 females) who did not have a previous history of significant high +Gz exposure. In order to document the cumulative long-term effects of high +Gz exposure and G protection measures, baseline echocardiographic studies were conducted prior to any +Gz exposure on the Dynamic Environment Simulator (DES) centrifuge. The echocardiograms were repeated after each panel member completed eight sessions of indoctrination. These follow-up echos were performed after all 18 subjects had been exposed to over 45 min (cumulative) of sustained acceleration > or = 2 G. Each subject served as his/her own control. All studies were evaluated independently by a cardiologist who was blinded to the order in which the studies were performed. Although complete echocardiographic studies were performed, only the parameters identified as significant in prior studies were evaluated. RESULTS: No significant differences were found between the initial and follow-up echo parameters. No significant differences were found between male and female responses. CONCLUSIONS: We found no significant differences in cardiac function after 45 min (cumulative) of exposure to G > or = 2 in men or women. These subjects will be monitored during a longitudinal study throughout their centrifuge subject career.