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  • Author or Editor: S. Tiwari x
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Abstract  

The removal behavior of stannic and zirconium phosphates was assessed for Sr(II) ions as a function of sorptive concentration, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solutions. First order uptake of Sr(II) followed the Freundlich adsorption isotherm for the entire range of sorptive concentration (10-2 to 10-8 mol.dm-3). The study of temperature dependence showed that the endothermic and irreversible type of uptake proceeds by an ion-exchange type mechanism.

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Abstract  

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.

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Abstract  

The removal behavior of hydrous titanium oxide and sodium titanate for Cs(I) from aqueous solutions by radiotracers was studied. Batch experiments revealed that an increase in Cs concentration (10–8 to 10–2 mol·dm–3), temperature (298 to 328 K) and pH (2.50 to 10.20) apparently enhanced the uptake of Cs(I) on hydrous titanium oxide whereas a high degree of uptake of Cs(I) on sodium titanate was almost unaffected by a change in adsorption temperature (298 to 328 K) and pH (2.50 to 10.20). Both systems follow Freundlich adsorption isotherm. Uptake of Cs(I) on hydrous titanium oxide obeys first order rate law. According to thermodynamic data the uptake is endothermic and apparently irreversible in nature.

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Inorganic particulates in removal of toxic heavy metal ions

IV. Efficient removal of zinc ions from aqueous solution by hydrous zirconium oxide

Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Mishra, V. Singh and D. Tiwari

Abstract  

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.

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Terminal heat referred to as increase in temperature during grain filling, is one of the important stress factors for wheat production and is responsible for decline in wheat production in many environments worldwide. In order to meet the challenges of high temperature ahead of global warming, concerted efforts are needed to evaluate wheat genotypes for heat tolerance and develop genotypes suitable for such stressed environments. Twenty-seven advanced wheat genotypes developed for stress and normal environments by different research centres were evaluated during 2009–10 and 2010–11 under timely sown (normal) and late sown (heat stress) environments. Analysis of variance revealed that the genotypes differed significantly in grain filling duration (GFD), grain growth rate (GGR) and thousand-grain weight (TGW). Out of 27 genotypes, 16 were found to be tolerant for thousand-grain weight under late planting (heat stress) during 2009-10 but only 12 were tolerant during 2010–11. Many of the genotypes registered more reduction in thousand-grain weight during 2010–11 as compared to 2009–10; the temperatures during 2009–10 were higher. The differences in grain filling duration under two conditions during both seasons as well as difference in temperatures during first half of grain filling explain the reduction pattern in the genotypes. GFD had significant negative correlation with temperatures during post heading period and the difference in GFD under two environments had positive correlation with these temperatures. The reduction in GFD had regression of 33.3% on reduction in GGR and reduction in GGR had regression of 41.6% on reduction in TGW genotypes AKW 1071, DBW 17, HS 277, K 7903, K 9107, NW 1014 and RAJ 3765 had less sensitivity to stress environments during both years.

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Inorganic particulates in removal of toxic heavy metal ions

Part X: Removal behavior of aluminum hydroxide for Hg(II): A radiotracer study

Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Mishra, D. Tiwari, S. Prasad, R. Dubey and Manisha Mishra

Abstract  

The removal behavior of amorphous aluminum hydroxide for Hg(II) ions from aqueous solutions was investigated by employing a radiotracer technique at micro down to trace level concentrations. The batch type experiments were performed to obtain various physico-chemical parameters, viz., effect of sorptive concentration, temperature and pH. It was observed that the increase in sorptive concentration (from 1·10−8 to 1·10−2 mol·dm−3), temperature (from 303 to 333K) and pH (from 3.4 to 10.3) apparently favored the uptake of Hg(II) by this solid. Similarly, the presence of anions (six fold) viz., oxalate, phosphate, glycine and EDTA also enhanced the uptake behavior of aluminum hydroxide for Hg(II). Whereas, the added cations viz., Na+, K+, Ba2+, Sr2+, Mg2+, Cd2+ and Fe3+ more or less suppressed the removal behavior of the adsorbent. Further, the adsorption process followed the classical Freundlich adsorption isotherm and deductions of various thermodynamic data revealed that the uptake of Hg(II) on aluminum hydroxide followed the ion-exchange type mechanism and thermodynamically it was found to be endothermic in nature.

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Abstract  

The role of dead biomasses viz., mango (Mangifera indica) and neem (Azadirachta indica) bark samples are assessed in the removal behavior of, one of important fission fragments, Cs(I) from aqueous solutions employing a radiotracer technique. The batch type studies were carried out to obtain various physico-chemical data. It is to be noted that the increase in sorptive concentration (from 1.0·10−8 to 1.0·10−2 mol·dm−3), temperature (from 298 to 328 K) and pH (2.6 to 10.3) apparently favor the uptake of Cs(I) by these two bark samples. The concentration dependence data obeyed Freundlich adsorption isotherm and the uptake follows first order rate law. Thermodynamic data evaluation and desorption experiments reveal the adsorption to be irreversible and endothermic in nature proceeding through ion-exchange and surface complexation for both dead biomasses. Both bark samples showed a fairly good radiation stability in respect of adsorption uptake of Cs(I) when irradiated with a 300 mCi (Ra-Be) neutron source having an integral neutron flux of ∼3.85·106 n·cm−2·s−1 and associated with a nominal γ-dose of ∼1.72 Gy·h−1.

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Grain yield and quality under terminal heat stress (post anthesis) are the most complex traits that are influenced by environmental factors and are characterized by low heritability and large genotype × environment interactions. The present study was undertaken to determine effectiveness of selection for genotypes tolerant to heat stress using differences in 1000-grain weight (dTGW) under the optimum and late sown field condition. A Recombinant Inbred Line (RIL) mapping population derived from the heat sensitive genotype Raj 4014 and heat tolerant genotype WH730 was evaluated for the heat stress over 2 years in a replicated trial under optimum and late sown field conditions. The parental lines were screened with approximately 300 SSR (μsatellite) markers out of which about 20% showed polymorphism. These polymorphic markers were utilized for genotyping a subset that had clear contrasting variation for dTGW. The difference in TGW between the timely and late sown conditions was used as a phenotypic trait for association with markers. Analysis of the two years data under timely and late sown condition revealed parents and their RILs clearly showing variation with respect to the dTGW. Regression analysis revealed significant association of dTGW of RILs with two markers viz., Xpsp3094, and Xgwm282 with coefficients of determination (R2) values of 0.14 and 0.11, respectively.

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The aim of this study was to develop a PCR based assay for an efficient selection of Yr10 resistance gene in breeding material. The two primer pairs designed from the Yr10 gene sequence amplified specific DNA fragments in the genotypes carrying Yr10 and did not give a signal with near isogenic line and other lines containing different Yr genes. The genetic linkage of these molecular markers to Yr10 gene was tested on a segregating F 2 population derived from cross between the stripe rust resistant genotype carrying Yr10 (FLW10) and the susceptible line WH542. The data demonstrated that the markers derived from Yr10 gene sequence are completely linked to Yr10 , which will enable to combine this gene with other stripe rust resistance genes in wheat breeding programmes.

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Summary  

The present paper reports the Differential Scanning Calorimetric (DSC) study of some Ag doped Se-Te chalcogenide glasses. DSC runs were taken at different heating rates. Well-defined endothermic and exothermic peaks were obtained at glass transition and crystallization temperatures. The variation of glass transition temperature T gwith Ag concentration has been studied. It has been found that T gdecreases with increase in Ag concentration. The heating rate dependence of T gis used to evaluate the activation energy of glass transition (DE t). The value ofDE thas been found to increase with increase in Ag concentration followed by nearly constant value at higher concentrations of Ag.

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