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Guwahati, India

Gauhati University is the first public university of North-East India, located in Guwahati, Assam, India. It was established on 26 January 1948. The University is situated to the west of Guwahati City and has 239 affiliated colleges. Wikipedia.

Sen Gupta S.,B N College | Bhattacharyya K.G.,Gauhati University
RSC Advances | Year: 2014

This review deals with adsorption of metal ions, particularly those considered as hazardous, on clays and some inorganic solids and covers the publication years 2000-2013 describing and quantifying the use of isotherms to obtain the adsorption capacities of the solids. The inorganic solids in the review include clays and clay minerals, their modified forms (obtained by treatment with acids and alkalis, organic functionalization, etc.), zeolites, silica gel, soil, river sediment, activated alumina, inorganic polymers, red mud, inorganic oxides, fly ash, etc. The use of two parameter and three parameter linear isotherms are only discussed with a view to obtain quantitative description of adsorptive accumulation and separation of metal ions from aqueous solution on the solids. The extensively used isotherms are those of Freundlich, Langmuir, Dubinin-Radushkevich and Redlich-Peterson. How these isotherms are being used to obtain the adsorption capacities along with their interpretations form the bulk of the review. The review is divided into sections, each describing the use of a particular isotherm. The metal cations receiving immense importance in adsorption studies are As(iii)/As(v), Cd(ii), Cr(iii)/Cr(vi), Cu(ii), Co(ii), Pb(ii), Ni(ii), Hg(ii), and Zn(ii), and the review covers both the cationic and the anionic metal ions. A few other cations such as Mn(ii), Fe(iii), Se(v), which have not received much attention, are also covered. © 2014 the Partner Organisations.

An exact solution to the problem of MHD transient free convection and mass transfer flow of a viscous, incompressible, and electrically conducting fluid past a suddenly started infinite vertical plate taking into account the thermal diffusion as well as the thermal radiation is presented. Assuming the medium to be nonscattered and the fluid to be nongray, emitting-absorbing, and optically thin radiation limit properties, the equations governing the flow and heat and mass transfer are solved by Laplace transform technique. The expressions for the velocity field, the concentration field, the skin friction at the plate in the direction of the flow, and the coefficient of heat transfer and mass transfer from the plate to the fluid have been obtained, and their numerical values for different values of the physical parameters involved in the problem have been demonstrated in graphs and tables, and these are physically interpreted. It is found that the thermal radiation retards the fluid flow whereas the Soret effect accelerates the flow. The viscous drag on the plate is increased under the Soret and magnetic field effects whereas the thermal radiation reduces the skin friction. Further, the rate of heat transfer at the plate increases under thermal radiation effect. Also, in the presence of radiation, the Soret effect results in a steady increase in the mass flux from the fluid to the plate. © 2012 American Society of Mechanical Engineers.

Sen Gupta S.,B N College | Bhattacharyya K.G.,Gauhati University
Physical Chemistry Chemical Physics | Year: 2012

The process of adsorption is considered to be one of the best water treatment technologies around the world. Different heavy metals, due to their toxic and hazardous nature, are possibly the most widespread groundwater contaminants imposing a serious threat to human health. In this review, an attempt has been made to discuss the use of two common clay materials, namely kaolinite and montmorillonite, along with their modified forms for heavy metal removal on the basis of published reports (2008 onwards). The modifications of clays have been attempted by the process of pillaring, intercalation, acid/base activation, functionalization, etc. The adsorption of toxic metals, viz., As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, etc., has been studied predominantly. Montmorillonite and its modified forms have much higher metal adsorption capacity compared to that of kaolinite as well as modified-kaolinite. The modification often boosted the adsorption capacities of the clays, however, reverse trends are also reported in some cases. © 2012 the Owner Societies.

Kalita K.,Gauhati University
Journal of Physics G: Nuclear and Particle Physics | Year: 2011

The complete, incomplete and fission cross sections are being measured for 12,13C + 208,207Pb systems to investigate the influence of breakup at above-barrier energies which form the same compound nucleus at the same excitation energies. The α-active heavy reaction products are measured for most dominant reaction xn-channels along with fission cross sections which originate almost exclusively from the complete fusion (CF). The results from the present systems show substantial components from the incomplete fusion in addition to CF. The CF cross section is suppressed by 12 2% for 12C and 3 2% for 13C compared with the single-barrier penetration model calculations. A systematic variation of the suppression of CF for reactions of weakly bound nuclei 6,7Li, 9Be, 10,11 B and 12,13C on targets of 207,208Pb and 209Bi is being found as a function of the breakup threshold energy. © 2011 IOP Publishing Ltd.

Bhagawati N.,Gauhati University
Acta Physica Polonica B | Year: 2014

We apply a simple transformation method to construct a set of new exactly solvable potentials (ESP) which gives rise to bound state solution of the D-dimensional Schrödinger equation. The important property of such exactly solvable quantum systems is that their normalized eigenfunctions can be written in terms of recently introduced exceptional orthogonal polynomials (EOP).

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