Abstract:Extraction / Te ^ / Tc^ / Tetraphenyl arsonium chloride
SummaryExtraction of TE VII an( j TCIV from nitric acid is investigated as function of tetraphenyl arsonium chloride concentration in the organic phase (chloroform). The ratio Kj/c 0 (distribution coefficient divided by the concentration of tetraphenyl arsonium chloride in the organic phase) was found to be approximately constant. Tc vl1 can be separated from 3 M HN0 3 by extraction with > 0.1 M tetraphenyl arsonium chloride in chloroform whereas Tc'V is … Show more
“…At lower pH the efficiency drops slightly. This decrease in extraction at lower pH is consistent with results from other extraction methods (such as ion pairing). − 3 Effect of pH on extraction efficiency. 2 and bulk ReO 4 - concentrations are 3 mM.…”
Section: Resultssupporting
confidence: 83%
“…This decrease in extraction at lower pH is consistent with results from other extraction methods (such as ion pairing). [17][18][19][20] Effect of the MO 4 -: Host Mole Ratio. The relative concentrations of host and MO 4were varied to determine (1) the mole ratio at which the extraction efficiency becomes saturated (no longer increases significantly) and (2) whether there are effects of competition as the target guest concentration is lowered.…”
Section: Resultsmentioning
confidence: 99%
“…The problem of 99 Tc in the environment is not new. Methods for removing 99 TcO 4 - from aqueous media that have been reported are primarily based on solvent extraction and ion exchange. − Previous methods have used tributyl phosphate, an extractant, and ion-pairing agents such as tetraorganoammonium, -phosphonium, and -arsonium salts, , Primene JMT, and triphenyltetrazolium chloride, utilizing extracting solvents such as chloroform, heptane, and toluene, with varying degrees of success. Unfortunately most of the solvents used in extractions are environmentally unsafe, posing an additional disposal issue, and the ion-pairing salts are not selective for pertechnetate.…”
Technetium-99 (beta-, t(1/2) = 2.15 x 10(5) years) is produced in a 6% fission yield from fission reactors. Technetium-99 continues to be of major concern at various nuclear sites because of its mobility in its most common chemical form during the reprocessing cycle and in the environment. Under these oxic aqueous environments the chemical form of Tc is typically Tc(VII)O4-, which is difficult to remove. Methods for pertechnetate removal to date have mixed results and pose further environmental concerns. Utilization of new cyclotriveratrylene host materials for the extraction of pertechnetate from 0.9% saline into nitromethane has shown high selectivity and efficiency. A deep-cavity host, tris[cyclopentadienyliron(II) arene]cyclotriguiasylene (2), has shown >95% extraction of pertechnetate and perrhenate into nitromethane from saline in the presence of competing anions, outperforming previously reported materials.
“…At lower pH the efficiency drops slightly. This decrease in extraction at lower pH is consistent with results from other extraction methods (such as ion pairing). − 3 Effect of pH on extraction efficiency. 2 and bulk ReO 4 - concentrations are 3 mM.…”
Section: Resultssupporting
confidence: 83%
“…This decrease in extraction at lower pH is consistent with results from other extraction methods (such as ion pairing). [17][18][19][20] Effect of the MO 4 -: Host Mole Ratio. The relative concentrations of host and MO 4were varied to determine (1) the mole ratio at which the extraction efficiency becomes saturated (no longer increases significantly) and (2) whether there are effects of competition as the target guest concentration is lowered.…”
Section: Resultsmentioning
confidence: 99%
“…The problem of 99 Tc in the environment is not new. Methods for removing 99 TcO 4 - from aqueous media that have been reported are primarily based on solvent extraction and ion exchange. − Previous methods have used tributyl phosphate, an extractant, and ion-pairing agents such as tetraorganoammonium, -phosphonium, and -arsonium salts, , Primene JMT, and triphenyltetrazolium chloride, utilizing extracting solvents such as chloroform, heptane, and toluene, with varying degrees of success. Unfortunately most of the solvents used in extractions are environmentally unsafe, posing an additional disposal issue, and the ion-pairing salts are not selective for pertechnetate.…”
Technetium-99 (beta-, t(1/2) = 2.15 x 10(5) years) is produced in a 6% fission yield from fission reactors. Technetium-99 continues to be of major concern at various nuclear sites because of its mobility in its most common chemical form during the reprocessing cycle and in the environment. Under these oxic aqueous environments the chemical form of Tc is typically Tc(VII)O4-, which is difficult to remove. Methods for pertechnetate removal to date have mixed results and pose further environmental concerns. Utilization of new cyclotriveratrylene host materials for the extraction of pertechnetate from 0.9% saline into nitromethane has shown high selectivity and efficiency. A deep-cavity host, tris[cyclopentadienyliron(II) arene]cyclotriguiasylene (2), has shown >95% extraction of pertechnetate and perrhenate into nitromethane from saline in the presence of competing anions, outperforming previously reported materials.
“…An aliquot sample was removed from the aqueous solution and added to equivalent volumes of chloroform containing 0.05 mol L −1 tetraphenylarsonium chloride. The organic phase removes TcO 4 − very efficiently leaving Tc(IV)-species in the aqueous phase [9]. Two to three consecutive extractions were carried out to secure complete removal of TcO 4 − from the solution before determining the concentration of Tc(IV) in the aqueous phase, if the TcO 4 − /Tc(IV) ratio was less than 20.…”
The deep geological disposal of the high level radioactive wastes is expected to be a safe disposal method in most countries. The long-lived fission product
“…Cyclohexanone [9,10], MEK [4,11] and TPAC [12,13] have been used for purification of Tc in radiochemical Measurement by ICP-MS For very low-level ^^Tc measurements by ICP-MS, a good linearity is necessary between ®'Tc concentrations and counting rates at m/z 99. Satisfactory linearity was confirmed in the ränge examined from 0 to 15pgml~' (1 mBq equals 1.6 pg), which would encounter in analyses of environmental samples.…”
Section: Recovery Of Tc In Various Steps Of Proceduresmentioning
An analytical procedure using inductively coupled plasma mass spectrometry (ICP-MS) was developed for determination of very low-level in seawater. Technetium in seawater was reduced and coprecipitated with iron hydroxide. The reduction of Tc by K2S2O5 at pH 4 was rapid and quantitative, and its coprecipitation with iron hydroxide at pH 9 was quantitative. A repetitive coprecipitation method using the same iron as coprecipitater showed no decrease of Tc recovery. Recovery of Tc in various steps of the procedure was examined, i.e., solvent extraction, anion and cation exchange. Background counting rate, with reference to ICP-MS, was extensively examined for various kinds of acids and reagents. The procedure developed showed good recovery for '^Tc and low background counting rate at m/z 99 by ICP-MS. The detection limit was about 40 times lower than the conventional radioanalytical method. The present procedure was applied to determination of "Tc concentration in coastal seawater.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
