North Guwāhāti, India
North Guwāhāti, India

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Ghosh D.,Jadavpur University | Deb A.,Jadavpur University | Pal S.,Kanchrapara College | Mondal M.,S A Jaipuria College
Physica Scripta | Year: 2010

In this paper, a detailed study of the chaotic behavior of compound hadrons (pions plus protons) in π--AgBr interactions at 350 GeV c -1 has been performed with the help of the parameter 'entropy index' μq, which is a measure of the chaotic behavior in multipion production processes. This index describes the event-to-event fluctuation of factorial moments that measures the spatial fluctuation of multiplicity distribution. The analysis reveals a large value for the entropy index signifying the chaotic behavior of the produced compound hadrons in high-energy hadron-nucleus interactions. It was been observed that the multipion production process becomes less chaotic with increasing average multiplicity of the final states. The study has been further extended to pions, and the corresponding results are compared. © 2010 The Royal Swedish Academy of Sciences.

Ghosh D.,Jadavpur University | Deb A.,Jadavpur University | Pal S.,Kanchrapara College | Mondal M.,S A Jaipuria College | And 2 more authors.
Indian Journal of Physics | Year: 2012

Erraticity analysis using the gap moment method is performed using the experimental data of π --AgBr interactions at 200 and 350 GeV both for pions and compound hadrons (pions + protons). The entropy like quantity S q has been calculated at two different energies. The variation of S q with q and their dependence on multiplicity of charged particles are investigated also. The study reveals the positive indication of the presence of erratic nature of event-by-event fluctuations of gap distributions of produced pions and compound hadrons in emission angle (cos θ) space in relativistic hadron-nucleus interaction. © 2012 IACS.

Chakraborty S.,French National Center for Scientific Research | Chakraborty S.,Kanchrapara College | Bardelli F.,French National Center for Scientific Research | Bardelli F.,University of Turin | And 6 more authors.
Chemical Geology | Year: 2011

Biotite is a constituent Fe-bearing mineral of Delta subsoils in India and Bangladesh and has been hypothesized as a primary source of arsenic (As). The adsorption behavior of As onto structural Fe(II, III)-bearing biotite fractions (<50μm) was investigated in the pH range of 4-8 under a CO2-free, anoxic condition (O2<1ppmv) using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The batch experiments indicate that As adsorption is strongly pH dependent and that As(V) adsorbs more efficiently than As(III). X-ray Absorption Near-Edge Structure (XANES) spectra show no oxidation or reduction of As by biotite after reaction with As(III) or As(V) solutions for 3days. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic results suggest that As(III) forms bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C) surface complexes at pH 7.7 as indicated by average As-Fe bond distances at 3.00±0.02Å and 3.37±0.03Å respectively. The surface speciation retrieved by XPS does not provide any evidence of reduction of As(V) on biotite after 30days further confirming the thermodynamic prediction and the XANES results. This study has therefore significant environmental implications for As contaminated areas, where biotite retards the release of As into reducing groundwater. The changes in soil redox conditions and weathering of biotite may likely contribute to the occurrence of high As in groundwater. © 2010 Elsevier B.V.

Bhowmick S.,University of Girona | Bhowmick S.,Kalyani University | Chakraborty S.,Kanchrapara College | Mondal P.,Catholic University of Leuven | And 5 more authors.
Chemical Engineering Journal | Year: 2014

Montmorillonite-supported nanoscale zero-valent iron (Mt-nZVI) has been synthesized to remove inorganic arsenic (As) from aqueous solutions. BET, SEM, EDX, XRD and XPS were used to characterize the clay-supported material which consists mainly of core shell Fe(0) structure with an outer oxide/hydroxide shell. The dispersion of nZVI onto montmorillonite was found to be increased with decreasing tendency to agglomerate into larger particles. Batch experiments revealed that adsorption kinetics followed pseudo-second order rate equation with high affinity towards both As(III) and As(V) over a wide pH range (4-8) which was decreased at pH>9. The maximum adsorption capacity calculated from the Langmuir adsorption isotherm was found to be 59.9 and 45.5mgg-1 for As(III) and As(V) respectively at pH 7.0. Although the presence of competing anions like SO42-, HCO3- and NO3- did not show pronounced effect, PO43- had an inhibitory action on the adsorption. The XPS analyses of As-reacted Mt-nZVI indicated the occurrence of surface catalyzed oxidation of As(III) to As(V). The possible regeneration using 0.1M NaOH and performance of Mt-nZVI was investigated by repeating adsorption-elution process. This study has great significance for demonstrating Mt-nZVI as potential adsorbent to reduce elevated levels of As in groundwater. © 2014 Elsevier B.V.

Ghosh D.,Jadavpur University | Deb A.,Jadavpur University | Mondal M.,Sa Jaipuria College | Mondal A.,Institute of Information Technology | Pal S.,Kanchrapara College
Pramana - Journal of Physics | Year: 2012

Event-to-event fluctuation pattern of pions produced by proton and pion beams is studied in terms of the newly defined erraticity measures x(p, q), x'q andμq' proposed by Cao and Hwa. The analysis reveals the erratic behaviour of the produced pions signifying the chaotic multiparticle production in high-energy hadron-nucleus interactions (π--AgBr interactions at 350 GeV/c and p-AgBr interactions at 400 GeV/c). However, the chaoticity does not depend on whether the projectile is proton or pion. The results are compared with the results of the VENUS-generated data for the above interactions which suggests that VENUS event generator is unable to reproduce the event-to-event fluctuations of spatial patterns of final states. A comparative study of p-AgBr interactions and p-p collisions at 400 GeV/c from NA27, with the help of a quantitative parameter for the assessment of pion fluctuation, indicates conclusively that particle production process is more chaotic for hadron-nucleus interactions than for hadron-hadron interactions. © Indian Academy of Sciences.

Chakraborty S.,French National Center for Scientific Research | Chakraborty S.,Kalyani University | Chakraborty S.,Kanchrapara College | Nath B.,University of Sydney | And 2 more authors.
Journal of Hydrology | Year: 2014

The transport of arsenic (As) in groundwater is known to be considerably controlled by the adsorption behavior of aquifer sediments and changes in subsurface redox conditions. Here we report wet chemical analyses of As(III) adsorption onto oxidized, low As containing Holocene aquifer sediments from West Bengal, India. Batch experiments in an open laboratory atmosphere show that the slow removal of As(III) from aqueous solution is a resulting effect of adsorption and oxidation which is not significantly influenced by the changes in pH (6.0-9.1). The isotherm data were fitted with Freundlich and Langmuir equations and maximum adsorption density (Γmax≈0.40mmolkg-1) obtained is lower than that for As(V) at pH 7.5 (0.95mmolkg-1). The estimated distribution coefficient maxima (Kd max) values are within the ranges of Kd values previously reported in case of Holocene aquifer sediments of West Bengal, India and Bangladesh. The low adsorption capacity of oxidized Holocene aquifer sediments in this study compared to oxidized Pleistocene sediments of Bangladesh is attributed to coarser grain sizes and low abundance of Fe-oxyhydroxides and micas which act as a potential sink of As. This study has important implications for As(III) attenuation and transport in the shallow aquifers (especially around the zone of 'maximum' water table fluctuations, i.e., 10-20m depth below ground surface) when oxygen-depleted (anoxic) Holocene aquifers get in contact with oxygen (e.g., by irrigation/groundwater drawdown) and also for predicting possible future risk associated with its transport from shallow aquifers to present day "low-As" containing deeper aquifers of West Bengal, India. © 2013 Elsevier B.V.

Ghosh D.,Jadavpur University | Deb A.,Jadavpur University | Pal S.,Kanchrapara College | Alam N.,Jadavpur University
Physics of Atomic Nuclei | Year: 2014

In the present work target excitation dependence of the self-similar cascading rate has been studied in detail in the framework of Levy stable law using the experimental data of pions obtained from π−-AgBr interactions at 350 GeV/c. TheLevy indices µ measured from the analysis fulfill the requirement of the Levy stable region 0 ⩽ µ ⩽ 2. The study gives an evidence of self-similar cascading mechanism responsible for multiparticle production. The different values of µ indicate different rates of cascading for different degrees of target excitation. Moreover, the values of universal scaling exponent (ν) obtained from Ginzburg-Landau theory indicate that no clear evidence of second-order phase transition has been found in the interaction. © 2014, Pleiades Publishing, Ltd.

Saha I.,Presidency University of India | Saha I.,Sripat Singh College | Gupta K.,Presidency University of India | Chakraborty S.,Kanchrapara College | And 2 more authors.
Journal of Industrial and Engineering Chemistry | Year: 2014

This study investigates the adsorption of As(III) on β-cyclodextrin modified hydrous ferric oxide (HCC). This is characterized by XRD, FESEM, AFM, XPS, BET, surface site concentration and FTIR. The modification of hydrous ferric oxide (HFO) surface by β-cyclodextrin provides ample OH groups which in turn increase As(III) adsorption on HCC compared to HFO. The adsorption remains almost constant in pH range 3-8 which decreases at higher pH (>8) and followed monolayer and pseudo first order kinetics. It is spontaneous at 303. K with increasing entropy and decreasing enthalpy. Thus HCC is found to be more efficient adsorbent than HFO. © 2013 The Korean Society of Industrial and Engineering Chemistry.

Bhattacharya P.,Kalyani University | Bhattacharya P.,Kanchrapara College | Samal A.C.,Kalyani University | Majumdar J.,Kalyani University | And 2 more authors.
Journal of Hazardous Materials | Year: 2013

Rice is an efficient accumulator of arsenic and thus irrigation with arsenic-contaminated groundwater and soil may induce human health hazard via water-soil-plant-human pathway. A greenhouse pot experiment was conducted on three high yielding, one hybrid and four local rice varieties to investigate the uptake, distribution and phytotoxicity of arsenic in rice plant. 5, 10, 20, 30 and 40mgkg-1 dry weights arsenic dosing was applied in pot soil and the results were compared with the control samples. All the studied high yielding and hybrid varieties (Ratna, IET 4094, IR 50 and Gangakaveri) were found to be higher accumulator of arsenic as compared to all but one local rice variety, Kerala Sundari. In these five rice varieties accumulation of arsenic in grain exceeded the WHO permissible limit (1.0mgkg-1) at 20mgkg-1 arsenic dosing. Irrespective of variety, arsenic accumulation in different parts of rice plant was found to increase with increasing arsenic doses, but not at the same rate. A consistent negative correlation was established between soil arsenic and chlorophyll contents while carbohydrate accumulation depicted consistent positive correlation with increasing arsenic toxicity in rice plant. © 2012 Elsevier B.V.

Chakraborty S.,Joseph Fourier University | Chakraborty S.,Institute for Radiochemistry | Favre F.,Joseph Fourier University | Favre F.,University of Lorraine | And 7 more authors.
Environmental Science and Technology | Year: 2010

The influence of surface-bound Fe(II) on uranium oxidation state and speciation was studied as a function of time (6 min-72 h) and pH (6.1-8.5) in a U(VI)-Fe(II)-montmorillonite (Ca-montmorillonite, MONT) system under CO 2-free, anoxic (O2 <1 ppmv) conditions. The results show a rapid removal of U(VI) from the aqueous solution within 1 h under all pH conditions. U LIII-edge X-ray absorption near-edge structure spectroscopy shows that 96% of the total sorbed U(VI) is reduced at pH 8.5. However, the extent of reduction significantly decreases at lower pH values as specifically sorbed Fe(II) concentration decreases. The reduction kinetics followed by X-ray photoelectron spectroscopy during 24 h at pH 7.5 demonstrates the presence of partially reduced surface species containing U(VI) and U(IV). Thermodynamically predicted mixed valence solids like U3O 8/β-U3O7/U4O9 do not precipitate as verified by transmission electron microscopy and extended X-ray absorption fine-structure spectroscopy. This is also supported by the bicarbonate extraction results. The measured redox potentials of Fe(II)/Fe(III)-MONT suspensions are controlled by the Fe(II)/hydrous ferric oxide [HFO(s)] couple at pH 6.2 and by the Fe(II)/lepidocrocite [γ-FeOOH(s)] couple at pH 7.5. The key finding of our study is the formation of a sorbed molecular form of U(IV) in abiotic reduction of U(VI) by sorbed Fe(II) at the surface of montmorillonite. © 2010 American Chemical Society.

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