Electromigration Separation of Lithium Isotopes: The Effect of Electrode Solutions

Both lithium-6 and lithium-7 with high abundance are indispensable materials in nuclear industry. Here, an aqueous solution│organic solution│aqueous solution system was fabricated to separate lithium isotopes. The effects of species and concentration of electrolytes in the electrode solutions on the lithium ions migration and lithium isotope separation with different voltages and migration time was studied. It was found that lithium-7 was enriched in aqueous solutions on both sides at 0 V and 2 V, while lithium-7 was enriched in anode solution and lithium-6 was enriched in cathode solution at 16 V. The weakening stability of the chelate consisted of crown ether and lithium ion with increasing voltage was believed to the possible reason. Meanwhile, the variation of electrolyte in electrode solution led to notable changes in migration ratio of lithium ions and lithium isotope separation effect, which can be attributed to the different degree of both ionization and hydrolysis for various electrolytes in aqueous solutions and the different ability of H+ and NH4+ to replace Li+ of chelate in organic solutions. This work is of great significance for the selection of electrode solutions in electromigration separation of lithium isotopes and even other electrochemical systems.

IONTOVÁ VÝMĚNA V POČÁTEČNÍCH STÁDIÍCH INTERAKCE ŽIVEC–VODA

The sample of perthitic alkali feldspar (62.5 wt. % of KAlSi3O8 and 37.5 wt. % of albite, Na0,996Ca0,004Al1,004Si2,996O8) was dissolved in a special stirred batch reactor (polyethylene vessel of 5 liter volume situated horizontally and rotating at few rotations per hour). The reactor was opened to atmosphere (log PCO2 ~ -3.5) through the mouth at the vessel axis. During the experiment, pH was monitored by pH-meter with combined glass electrode. Solutions were analyzed for Si, Al (spectrophotometry), K, Na (flame AAS), and Ca (ICP-OES). The results showed a fast preferential leaching of alkaline cations with respect to both Al and Si during the early stages of experiment that was diminishing during more advanced stages of the experiment. The released cations exceeded the consumed H+ ions by the range of two up to four magnitudes. The preponderance of cations over H+ ions was especially apparent during few initial days, when the buffering by atmospheric CO2 was insufficient. Simulation of the process by the PHREEQC code covering the CO2 buffering indicated that system feldspar–water–CO2(g) was evolving near the equilibrium in open system during the period after 5th day of the experiment. The results suggested that the mechanism of feldspar dissolution during the initial stages of the process does not correspond to a simple ion exchange and that it is more complicated.

Fabricated Carbon Nanotube Electrodes Blending with Various Metal Phthalocyanines for Detection of Five Taste Models

Electrochemical characteristic of blended multiwall carbon nanotube paste electrode (CNTPE) was investigated with five basic taste models. The multiwall carbon tube was blended with metal phthalcyanine (MPc) powders including of CoPc, FePc, MgPc, MnPc and ZnPc to produce modified working electrode. Solutions with concentration of 0.1 M of potassium chloride (KCl), magnesium chloride (MgCl2), sucrose, citric and monosodium glutamate (MSG) were used as model solutions of saltiness, bitterness, sweetness, sourness and umami, respectively. Cyclic voltammograms (CV) of the fabricated electrodes were observed in range of 0.0 to 1.0 V. Blended MPc and CNTPE showed effects on electron transfer or redox reactions in some model taste solutions. The blended fabricated electrodes indicated cross-selectivity response for these five basic model solutions. However, the CV characteristics of the all fabricated blending electrodes in KCl and MgCl2 solutions are similar due to Cl- ion in both salt solutions. The measured CV of blended electrodes in the five solution models exhibit clearly different characters by mean of its symmetry and peak feature. These characters can be used to classify the distinctive feature of five tastes for electronic tongue