S. P. Mishra

Radiotracer technique in adsorption studies

Hydrous manganese oxide (HMO) was synthesized and its adsorption properties with respect to Ba(II) ions investigated as a function of contact time, adsorptive concentration, temperature and pH, using a radiotracer technique. The adsorption equilibrium is achieved quickly in ca. 30 min and the steady state values of adsorption at various concentrations (10−2–10−7M) agree well with the classical Freundlich isotherm. The adsorption increases with increasing pH and reaches a maximum followed by a plateau over a fairly wide pH range. The temperature markedly affects the extent of adsorption and the process is thermodynamically found to be irreversible.

Inorganic particulates in removal of toxic heavy metal ions: IV. Efficient removal of zinc ions from aqueous solution by hydrous zirconium oxide

Adsorption behavior of zinc ions on hydrous zirconium oxide (HZO) in aqueous solution has been studied as a function of concentration (10−2–10−8M), temperature (303–333 K) and pH 3–8 of adsorptive solution applying radiotracer technique. The kinetics of adsorption follows first order rate law and agrees well with the classical Freundlich isotherm in the entire range of adsorptive concentration. The removal was found to be increasing with pH of the adsorptive solution while it was suppressed in the presence of acid concentrations. The overall process is found to be endothermic and irreversible in nature.

Rapid and efficient removal of Hg(II) from aqueous solution by potassium hexa-titanate: A radiotracer study

The adsorption of mercury(II) on potassium titanate has been studied in chloride media at different pH values, adsorbate concentrations and temperatures. Effect of different ligands and acid concentrations on the uptake was also investigated. Desoprtion studies were also done to check the reversibility of the process. Interestingly a more or less constant and high value of adsorption has been found at different temperatures, pH values and concentrations and a decrease in the uptake with an increase in the bulk acid concentration was observed.

Biosorptive behavior of some dead biomasses in the removal of Sr(85+89) from aqueous solutions

The knowledge of radioactive and stable elements partitioning to natural sediment systems is essential for modelling their environmental fate. A sequential extraction method consisting of six operationally-defined fractions has been developed for determining the geochemical partitioning of natural (U, Th, 40K) and antropogenic (Pu, 241Am, 137Cs) radionuclides in a 10 cm deep sediment sample collected in the Tyrrhenian sea (Gaeta Gulf, Italy) in front of the Garigliano Nuclear Power Plant. 137Cs and 40K were measured by gamma-spectrometry. Extraction chromatography with Microthene-TOPO (U, Th), Microthene-TNOA (Pu) and Microthene-HDEHP (Am) was used for the chemical separation of the alpha-emitters: after electrodeposition alpha-spectrometry was carried out. Some stable elements (Fe, Mn, Al, Ca, Pb, Ba, Ti, Sr, Cu, Ni) were also determined in the different fractions to get more information about the chemical association of the radionuclides.

Ion exchangers in radioactive waste management VII. Radiotracer studies on adsorption of Ba(II) and Sr(II) ions on hydrous thorium oxide

Hydrous thorium oxide (HTO) was synthesized and laboratory study was conducted to address its applicability for decontamination of barium and strontium ions from radioactive liquid wastes using radiotracer technique. The adsorption of Ba(II) and Sr(II) on HTO has been investigated as a function of pH, concentration and temperature of the adsorptive solution and the results obtained show that these parameters affect the extent of adsorption very appreciably. Pre-treatment of oxide adsorbent with neutrons and γ-radiation from a 11.1 GBq Ra−Be neutron source reduces its adsorption capacity upto 24 hours of irradiation and then enhances it on further irradiation. The nature and mechanism of adsorption are discussed.

Chemical effects of56Mn-recoils in mixed crystals of potassium permanganate with perchlorates

The chemical effects of56Mn-recoils following neutron capture produced in mixed crystals /KMnO4−LiClO4, KMnO4−NaClO4 and KMnO4−KClO4/ have been investigated. A linear increase of initial retention with the mol fraction of perchlorate was observed which is tentatively ascribed to the tendency to form species having structures similar to that of the host matrix. The ultimate chemical fate of the manganese atom also depends on the conditions of the immediate chemical environment of the atoms /e.g. Li, Na, K/ at rest in the crystal. The results are discussed in terms of retention and non-retention reactions invoking a mechanistic model involving metal and ligand-vacancy exchange, substitution and transfer reactions.

Hot atom chemistry in oxyanion targets, part II1: Recoil behaviour of56Mn in permanganates

Fractional precipitation techniques have been utilized to separate the lower valent and parent forms of56Mn in permanganate targets and an attempt is made to study a few aspects of chemical stabilization of recoil56Mn in permanganates. Ammonium permanganate, recoil behaviour of which has not been studied previously, is chosen as one of the targets along with the potassium permanganate for initial retention and also for isothermal annealing.56Mn initial retentions of about 12% and about 4% are obtained for potassium and ammonium permanganate, respectively, by activation from a Ra−Be neutron source. A usual trend for KMnO4 and the reduction of recoil fragments by ammonium ions in NH4MnO4 are seen through the isothermal annealing study.

Behaviour of energetic radioiodine atoms arising in iodate-nitrate solid solutions under /n,γ/ process

The retention and yields after neutron irradiation under standard conditions by ionizing radiation have been studied as a function of the mole fraction of nitrate in NaIO3−NaNO3 mixed-crystals. The effect of nitrate ion on the retention in solid-solution after irradiation was observed. A probable mechanism is suggested.

Removal of zinc and mercury ions from aqueous solution by hydrous ceric oxide

The present work deals with study of uptake behavior of zinc and mercury ions by hydrous ceric oxide applying a radiotracer technique. The influence of various parameters such as concentration, temperature and pH have been examined. It was observed that the amount of zinc and mercury ions adsorbed at equilibrium increases with increase of adsorptive concentration (1.0·10−7 to 1.0·10−2M), temperature (303–333K) and pH (ca. 3–10). Concentration dependence data agree well with the classical Freundlich isotherm. The radiation stability of hydrous ceric oxide was also investigated by exposing it to a 11.1 GBq (Ra−Be) source associated with γ-dose of 1.72 Gy·h−1 and also using a60Co source (4.66 kGy·h−1). Adsorption of these metal ions in the presence of some monovalent and divalent cations and complexing agents has also been included in the study.

Hot atom chemistry in oxyanion targets. Part IV1: Recoil isochronal annealing in permanganates

Investigations on isochronal annealing behaviour of /n, γ/ activated56Mn recoils in crystalline potassium and ammonium permanganates have given different results indicating a varying degree of sensitivity of the samples to recoil annealing. The presence of ammonium ion in ammonium permanganate shows the reduction of recoil species during annealing. Vand-Primak model has been utilized to deduce the kinetic behaviour by which the energy of activation is found to be 1.1 and 1.2 eV for KMnO4 and NH4MnO4, respectively. Furthermore, the present work reveals the role of defects in the transient reactions of the lattice stable precursors and hence the mechanism of the recoil reactions.