The removal efficiency of moderate levels of radon from groundwater supplies was evaluated using the diffused bubble aeration
technique. An aeration system was designed, constructed and operated for that purpose. The effect of air-to-water ratio and
detention time on radon removal were evaluated through 32 runs. The possibility to reduce the radon activity in the influent
stream to the U.S. Environmental Protection Agency proposed maximum contaminant level (MCL) was verified through many alternative
combined values of both air-to-water ratios and detention times. The results showed that at detention time of 19 minutes and
air-to-water ratio of 12, the average radon removal is about 97%. The stripping constant characterizing this system was calculated
and the removal efficiency at extended values of detention time was predicted. The data obtained are site specific, being
dependent on container size, type of diffusers, temperature, and influent radon radioactivity.
Authors:Qifeng Liu, Jiali Liao, Ning Liu, Dong Zhang, Houjun Kang, Yuanyou Yang, Bing Li, Haijun Zhu, and Jiannan Jin
As an important radioisotope in nuclear industry and other fields, 241 Am is one of the most serious contamination concerns due to its high toxicity and long half-life. In order to supply useful
reference for disposal of 241Am waste with low-medium radioactivity, the adsorption and migration behavior of 241Am on aerated zone soil were investigated by the static experimental method and column experiments. The results showed that
more than 98% of the total 241Am could be adsorbed from 241Am solution of 0.32·10−7−1.1·10−7 mol/l by the soil at pH 4–9. The adsorption of 241Am on the soil was a pH-dependent process at pH<4, but for pH>4, the adsorption rate of 241Am on the soil changed minutely. The adsorption equilibrium was achieved within 24 hours and no significant effect on adsorption
of 241Am was observed at liquid-solid ratios of 50:1–500:1. The relationship between concentration of 241Am and adsorption capacities of 241Am can be described by the Freundlich adsorption equation. Adsorption of 241Am on the soil can be inhibited by humic acid, ferric hydroxide colloid, or some anions, such as citric acid anion, saturated
EDTA solution, C2O42− and CO32−. It was also noted that the adsorption rate of 241Am drops in solutions containing Eu3+ or Nd3+, even 0.5 times above the 241Am concentration. A migration distance of 8 mm for 241Am(III) is observed only in the aerated zone soil containing ferric colloid, while a migration distance of less than 2 mm
is noted in other soil samples after more than 250 days. All these results indicate that the aerated zone soil is an efficient
sorbent for 241Am and can inhibit the migration of 241Am.
Authors:Imre Czinkota, János Szanyi, Balázs Kovács, András Sebők, Ildikó Hajdok, and Márton Papp
This paper aims at determining the behavior of thermal water brought to surface and how this might impact reinjection wells and the rock during reinjection. The biggest problem is that reinjection wells are predisposed to choking. We searched for a method to examine this process, including a model for physico-chemical changes in the water—rock interaction. Two different samples of powdered rock (designated α and β) were analyzed using thermal water samples from production and reinjection wells. The pH shows significant differences between the samples from wells where free water treatment was carried out, and those from the aerated thermal waters, as well as for the rock sample. Basically, a decrease in sediment volume can be obtained by increasing the pH. The salt effect was more coherent. Its result was an interesting case of W-shaped graphs from the producing well. On the other hand there is virtually no difference between the samples with acid titration.
The present study deals with the radiolysis of tetracycline hydrochloride dissolved in aerated alkaline aqueous solutions containing 0.1, 0.5 and 1M NaOH, at 77 K, as followed by ESR. The rate constants for the reactions between the electron and physical and chemical traps which are present in these solutions are calculated. These values are kph= =9.6·1015 l·mol–1·s–1 and kch=1.3·1010 l·mol–1·s–1. The reactivity of electrons that are formed in the radiolysis of water decreases in the following proportions: physical traps: chemical traps: molecules of water: 4.8·1014: 6.5·108: 1.0. The electrons react preferentially with the solute instead of the solvent.
Authors:Vasileios Anagnostopoulos, Argyro Bekatorou, and Basil Symeopoulos
The dependence of U(VI) uptake on the temperature of cell culture, the air flow during the cultivation process and the age
of cells were studied. Saccharomyces cerevisiae, Kluyveromyces marxianus and Debaromyces hansenii were chosen as typical yeasts, which are widely used, in food industries. Our results revealed that the highest metal uptake
was obtained from exponential phase cells, which had been cultivated at the optimum temperature of growth, while the air flow
during the cultivation process, exhibited no significant effect on the metal uptake. A qualitative interpretation of bibliographic
data, concerning the metal uptake on the age of cells is proposed, assuming that qualitative changes in the cell wall structure take place, as the cells pass from exponential to stationary phase, in addition to quantitative
modifications, which have been reported in the literature. According to our interpretation, the relative abundances among
quantitative and qualitative alterations of cell wall, determine which cells (exponential or stationary) exhibit the higher
metal capacity. One type of the suggested qualitative modifications of surface constituent of cell wall, may have been caused
by a shortening of a carboxylic acid carbon chain. This type of modification implies, as prerequisite, the decrease of pKa values of cell wall carboxyl groups, with the age of cells. An evidence, supporting our approach, may be the fact that the
decrease of pKa values mentioned above, has been observed by other authors.