S. Mishra

Bio: S. Mishra is an academic researcher from Bhabha Atomic Research Centre. The author has contributed to research in topics: Uranium & Soil test. The author has an hindex of 9, co-authored 20 publications receiving 277 citations. Previous affiliations of S. Mishra include National Institute of Radiological Sciences.

Separation studies of uranium and thorium using tetra(2-ethylhexyl) diglycolamide (TEHDGA) as an extractant

Abstract: The extraction behavior of uranium, thorium and nitric acid has been investigated for the TEHDGA/isodecyl alcohol/n-dodecane solvent system. Conditional acid uptake constant (KH) of TEHDGA/n-dodecane and the ratio of TEHDGA to nitric acid were obtained as 1.72 and 1:0.96, respectively. The extracted species of uranium and thorium in the organic phase were found to be UO2(NO3)2·2TEHDGA and Th(NO3)4·2TEHDGA. A workable separation factor (DTh/DU) of the order of 300 was observed between thorium and uranium in the nitric acid range of 0.5M to 1.5M. Similar separation factor was also achieved at higher acidity when thorium was present in large concentration compared to uranium. These results indicate that TEHDGA solvent system could be a potential candidate for separation of thorium from uranium.

Distribution and retention of Cs radioisotopes in soil affected by Fukushima nuclear plant accident

Abstract: There was a large release of radio-cesium (134Cs and 137Cs) to the atmosphere during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, and contaminated the soil, over a vast area, due to fallout activity. Therefore, studies on the behaviour of radio-cesium especially migration in soil and its retention on soil particles is very important for external dose assessment and root uptake. We have determined the sorption coefficient (K d) for Cs using the laboratory batch method in soil samples collected from a contaminated area affected by the FDNPP accident, and the effect of various soil parameters on the K d value has been studied. We have noticed that Cs sorption is mostly influenced by cation exchange process and Cs is sorbed on the surface of clay particles. From vertical depth profile of Cs in soil, it is found that most of it is retained on the top layer within a 5-cm thickness. Sequential extraction of soil using various reagents may be helpful to understand better the mechanism of Cs retention.

Aqueous Partitioning of Minor Actinides by Different Processes

Abstract: Actinide partitioning is a proposed strategy for effective mitigation of the long-term hazards associated with high-level waste (HLW). Octyl-(phenyl)–N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) and diphenyl–N,N-diisobutyl carbamoyl methyl phosphine oxide (DφCMPO) are amongst the promising extractants extensively studied since the 1980s for actinide partitioning from wastes of different origin. During the last two decades, substituted malonamide extractants such as N,N'-dimethyl-N,N'-dibutyl tetradecyl malonamide (DMDBTDMA) and N,N'-dimethyl-N,N'-dioctyl hexylethoxy malonamide (DMDOHEMA) have emerged as viable green alternatives to phosphine oxides. During the last decade, diglycolamide-based extractants such as N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (TEHDGA) have received considerable attention due to overwhelmingly favourable extraction and stripping efficiencies of minor actinides from different types of transuranium (TRU) wastes. The focus o...

Soil Contamination, Nutritive Value, and Human Health Risk Assessment of Heavy Metals: An Overview

Abstract: Globally, rapidly increasing industrialization and urbanization have resulted in the accumulation of higher concentrations of heavy metals in soils. The highly contaminated soil has therefore become unsuitable for cultivation probably because of the deleterious metal effects on the fertility of soils among various other soil characteristics. In addition, the uptake of heavy metals by agronomic crops and later on consumption of contaminated agri-foods have caused a serious threat to vulnerable human health. Considering these, a genuine attempt is made to address various aspects of metal contamination of soils. In addition, the nutritive value of some metals for bacteria and plants is briefly discussed. Here, we have also tried to understand how heavy metals risk to human health could be identified. These pertinent and highly demanding discussions are likely help to strategize the management options by policy makers/public for metal toxicity caused to various agro-ecosystems and for human health program.

Simple small molecule carbon source strategy for synthesis of functional hydrothermal carbon: preparation of highly efficient uranium selective solid phase extractant

Abstract: In this paper, simple small molecules, glyoxal and acrylonitrile, are chosen as starting materials to prepare an amidoxime-functionalized hydrothermal carbon-based solid phase extractant (HTC-AO) via a one-step hydrothermal process following a simple oximation. The resulting HTC-AO exhibits the anticipated properties, i.e., low porosity (0.01 cm3 g−1) and intraparticle diffusion coefficient (kint = 0.042 mmol g−1 min−0.5), high content of amidoxime groups (1.66 mmol g−1) and minimal undesired functional groups (typically carboxylic group: 0.07 mmol g−1; phenolic group: 0.38 mmol g−1; lactonic group: 0.01 mmol g−1). Moreover, the results of irradiation experiments under γ-ray dosages between 1 and 100 kGy indicate that HTC-AO has good radiation stability. The sorption behavior of U(VI) onto HTC-AO is investigated in detail using batch sorption experiments. A saturation U(VI) sorption capacity over that of all the uranium sorbents reported previously is found to be 1021.6 mg g−1 at pH 4.5 in single uranium solution, and a so far unreported highest uranium selectivity of 81.6% with a sorption capacity of 268.9 mg g−1 is observed at pH 2.5 in multi-ion solution. The significant outcomes in this work confirms that the “simple small molecule carbon source” strategy is practical and efficient, and may have the potential for the preparation of other types of functional materials such as highly specific catalysts, drug targeting carriers and others.