Diwakar Tiwari

The uptake behaviour of rice (Jaya) husk in the removal of Zn(II) ions—A radiotracer study

Sequestering of Zn(II) ions at the surface of rice husk has been studied as a function of contact time, adsorptive concentration, temperature and pH, using the radiotracer technique employing a 65Zn radiotracer. A relatively slow uptake of metal ion increasing with bulk dilution (10(-2) to 10(-7) mol/dm3) was seen, which obeys the first-order rate law and agrees well with the classical Freundlich adsorption isotherm. The removal of metal ions from the bulk increases with the increase in pH (3.2-10.2) and temperature (293-323K) and evaluation of the thermodynamic data shows that the process involved is endothermic and apparently irreversible in nature, suggesting an ion exchange mechanism along with surface complexation. On the other hand Cd(II) was not adsorbed on the surface of the rice husk at pH 6.2.

Radiotracer technique in adsorption study: Part XIV. Efficient removal of mercury from aqueous solutions by hydrous zirconium oxide

Adsorption of Hg(II) ions on synthetic hydrous zirconium oxide has been investigated as a function of contact time, Hg(II) concentration (10−3−10−8 M) and temperature (303–333 K). x-Ray diffraction studies indicated the amorphous nature of the synthesized oxide. The relative change of uptake, i.e. percentage adsorption increases from 80.3 to 98.3% with the increase in dilution (from 1.0 × 10−3 to 1.0 × 10−8 M). The kinetics of the process follows first order rate law and obeys the Freundlich isotherm over the entire range for the bulk concentration of Hg(II). The uptake of Hg(II) increase in temperature from 303 to 333 K. Pre-irradiation of adsorbent with neutrons (3.85 × 106 n/cm2/s) and γ-radiations (ca 1.72 Gy/h) has practically no effect on the extent of adsorption of Hg(II).

Biosorptive behaviour of casein for Zn2+, Hg2+ and Cr3+: effects of physico-chemical treatments

Abstract The uptake behaviour of milk protein (casein) for some heavy metal toxic ions [Zn2+, Hg2+ and Cr3+] was investigated by employing the ‘radiotracer technique’. The effects of various physico-chemical treatments were investigated in order to explain the sequestering behaviour of this biomass. In a single batch equilibrium experiment a decrease in adsorptive concentration (10−2-10−8 mol L−1) and increase in temperature (293–323 K) and pH (ca 3–10) specifically increased the uptake of the metal ions. The uptake followed a first-order rate law and obeyed the Freundlich isotherm. Changes in standard enthalpy and activation energy involved during the biosorption were deduced for these systems. Also, desorption experiments showed that no significant desorption took place.

Inorganic ion exchangers in radioactive waste management

SummaryThe uptake of indigenously synthesized amorphous stannic and zirconium phosphate was assessed for, one of the important fission fragment, cesium from aqueous solutions using a radiotracer technique. A virtual increase in sorptive concentration (from 1.0 . 10-8 to 1.0 . 10-2 mol . dm-3) and pH (from 2.4 to 10.2) and temperature (from 303 to 333 K) enhanced the uptake of cesium on stannic phosphate. However, the extremely high degree of uptake of cesium on zirconium phosphate was almost unaffected with the dilution beyond 10-5 mol . dm-3 and pH (i.e., from 2.4 to 10.2) and temperature (from 303 to 323 K). Irreversible uptake occurring for these solids follow the Freundlich adsorption isotherm and the presence of several complexing agents viz., sulphate, phosphate, glycine and EDTA did not affect appreciably the uptake of cesium on zirconium phosphate but it did affect for stannic phosphate system. Both these solids showed good radiation stability towards a 11.1 GBq Ra-Be neutron source having neutron flux ca. 3.2 . 106 n . cm-2 . s-1 and associated with a nominalg-dose of ca. 1.72 Gy/h, at least for the uptake of cesium.

Radiotracer Technique in Adsorption Study Part XV. Removal Behaviour of Barium Titanate for Mercury Ions

Adsorption of Hg(II) ions on barium titanate have been investigated over a wide range of concentration (10 10 * M), temperature (303-333 K) and pH (3.2-10.4) of the adsorptive solution using a radiotracer technique. The uptake was found to increase with increasing concentration, temperature and pH of the adsorptive solution. Kinetics of the process follows a first order rate law and agrees well with the classical Freundlich isotherm for the entire range of adsorptive concentration. Removal appears to be ion-exchange in type and thermodynamically irreversible in nature.

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.

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.