Search Results

You are looking at 151 - 160 of 329 items for :

  • All content x
Clear All

Abstract  

The chromatographic behaviour of Hg(II), methylmercury, phenylmercury and Cu(II) on three different sorbents, strong acidic sulfobutyl cation-exchanger, weak basic aminopropyl anion-exchanger and silicagel has been studied. A dithizone solution in cetyltrimethylammonium hydrogensulfate water micellar medium was found as a useful post-column derivatization reagent for UV-VIS detection. The detection limits 1.1 ng, 2.2 ng, 6.2 ng and 1.6 ng were found in silicagel chromatographic system and dithizone detection system for Hg(II), methylmercury, phenylmercury and respectively for Cu(II).

Restricted access

Abstract  

Reduction of carbon dioxide (CO2) in the environment may avert the effects of global warming. One method to control CO2 emissions is to sequester it underground. Leakage from storage must be minimized for long-term control. Detection of leaks decreases the amount of CO2 released from storage, so onsite monitoring must be performed over large areas. Spiking the injected CO2 with an isotopic tracer can improve ground leak detection using fewer sampling stations, with greater accuracy than CO2 sensors and no interference from radon gas. The relative merits of sorbent materials, isotopic tracers, detection methods and potential interferences will be discussed.

Restricted access

Abstract  

Feasibility of using fixed bed column of conventional ion exchangers/sorbent and chemical precipitation based processes have been examined for the effective removal of the very low levels of 106Ru activity from NH4NO3 effluent generated during wet processing of rejected sintered depleted uranium fuel pellets. Based on the results, a simple process involving precipitation of cobalt sulphide along with ferric hydroxide was selected and further optimization of process variables was carried out. The optimized process has been found to be highly efficient in reducing 106Ru activity down to extremely low levels.

Restricted access

Abstract  

The potential uses of hydrous oxides in the treatment of radioactive wastes may be affected by the physical-chemical properties of these materials. The sorption behavior of trace level (less than 10-14 g/ml) 235U fission products in aqueous solutions was studied under static conditions on TiO2, MnO2 and SnO sorbents. A variety of anions, cations and neutral species of 132Te,95Zr, 99Mo and 103Ru in aqueous solutions at 1, 3, 5, 7 and 10 pH values were identified and their retention values were calculated. High voltage electrophoresis was used to establish the chemical species of these radioisotopes formed in the solution.

Restricted access

Abstract  

On-line chemistry studies of short-lived isotopes of Os and Re, as homologs of 108 (Hs) and 107 (Bh), respectively, produced in the nuclear reactions at the (LNR, Dubna) cyclotron have been carried out. It was shown, that Os and Re are not sorbed on cation exchangers, but very strongly sorbed on anion exchangers from diluted HCl solutions. Re is also retained by a TOPO containing sorbent and may be separated from Os. The possibilities of chemical species and oxidation states investigation of short-lived transactinide elements by continuous chromatography have been shown.

Restricted access

Abstract  

The results of atomic dynamics of ultrafines clusters of iron hydroxide and Fe 2 O 3 with average size 1–3nm are shown. The clusters were synthesised after chemical reaction in solution in micropores of sorbents and in topochemical reactions of thermal decomposition salts. Moessbauer spectroscopy studies are applicated. The effect of Surface Active Substance(SAS) on dynamics of clusters is observed. Thermodynamics and phemonologic models of dynamic state of cluster are considered and the probability of the coexistans solid-liquid state of cluster is discussed.

Restricted access

Abstract  

The inhibitory action of hydrazinium or amidosulfate ion, whose presence prevented the oxidation of potassium cupric ferrocyanide with nitric acid and thereby kept the distribution coefficient of Cs on the sorbent at very high values in strong nitric acid medium, was eluciated to be due to the removal of nitrous acid present as an impurity. Based on this interpretation, a number of chemicals capable of reacting with nitrous acid were found to be effective as inhibitors besides hydrazinium and amidosulfate ions. A new process for Cs separation was proposed on the basis of the result obtained.

Restricted access

Abstract  

A standard analytical technique for determination of the partial ion exchange capacity of mineral or soil for selective uptake of cesium, the specific radiocesium interception potential (SRIP) is formulated and theoretically discussed. The method is based on the determination of a retained, leached or sorbed fraction of carrier-free cesium-137 in soil contacted with 0.01M KNO3-0.01M Ag thiourea complex solution at the phase ratio solution:sorbent 10 ml:0.1 g. Reliability of the method is discussed in connection of radiocesium carrier and humic substances presence.

Restricted access

Abstract  

The effect of humic acid addition on the capacity of inorganic sorbents to sorb radioactive cesium and strontium was studied on montmorillonites in a calcium and potassium form. The Sips isotherm for humic acid sorption and multisite distribution model of ion sorption was found to suit well for the description of mobility of ions as a function of equilibrium humic acid concentration as a single variable at given pH and type of silicate. Complexation of the ions was of minor importance at the conditions investigated. Influence of humic acid on the specific radiocesium interception potential (SRIP) was also evaluated.

Restricted access

Abstract  

Radiotracer technique has been used for the investigation of adsorption of chromium (VI) traces on bismuth trioxide from aqueous solution. The effect of pH (2–10), concentration of chromate solution (10–6–10–2M) and temperature (303–323 K) has been thoroughly investigated. The influence of certain foreign ions has also been studied. The calculated kinetic and thermodynamic parameters indicate the first order rate law, spontaneity and exothermic nature of the adsorption process. Further, IR studies have established the chemical interaction between the sorbate and sorbent and a possible mechanism of the sorption process based on ligand exchange has been proposed.

Restricted access