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21.
Separation of lignosulfonate from its aqueous solution using supported liquid membrane 总被引:2,自引:1,他引:1
Kabita Chakrabarty Prabirkumar Saha Aloke Kumar Ghoshal 《Journal of membrane science》2009,340(1-2):84-91
This paper presents an experimental and theoretical study on facilitated transport of lignosulfonate (LS) through a flat sheet supported liquid membrane using trioctylamine (TOA) as carrier and dichloroethane as diluent. The studies were carried out with various support materials and operating conditions (viz. carrier concentration, strip phase concentration, salt concentration, etc.) and their effects on the transport of LS. The results were analyzed to identify a suitable combination of support and operating condition that would yield best performance of the supported liquid membrane (SLM) in terms of fast and efficient transport of LS. The stability of the SLM was assessed in terms of loss of liquid from the pores of membrane support. The SLM is found to be stable till 10 h. Co-transport mechanism has been adopted in this work by using NaOH as the strip phase. It was observed that extraction of LS is increased with increase in concentration of NaOH up to a limiting value of 0.5 M NaOH. Difference of salt concentration between feed and strip phase considerably affect the separation process. The diffusional resistances of organic membrane (Δorg) and aqueous solution (Δaq) calculated from the permeation model, which is again a combination of three unique mechanisms viz., diffusion through a feed aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier–complex through the organic membrane, are found to be 609.9 and 176.6 s cm−1, respectively. The values of the diffusion coefficient in the membrane (Dorg) and in the bulk organic phase (Dcomplex) are 1.67×10−9 and 6.68 × 10−8 m2s−1, respectively. The extraction of LS is about 90%. Nearly 43% of LS can be recovered at optimum condition. 相似文献
22.
Alok Chakrabarty Pradipta Purkayastha Nitin Chattopadhyay 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):256-261
The cis-skew to trans-planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution. 相似文献
23.
Kabita Chakrabarty Prabirkumar Saha Aloke Kumar Ghoshal 《Journal of membrane science》2010,346(1):37-44
This paper presents an experimental investigation on facilitated and simultaneous transport of mercury and lignosulfonate (LS) through a flat sheet supported liquid membrane (SLM) having Nylon 6,6 as support, trioctylamine (TOA) as carrier and dichloroethane as solvent. The experiments were performed at various operating conditions such as strip phase concentration, feed pH, carrier concentration and feed concentration to find the best set of parameters that would yield the maximum separation of pure mercury as well as its mixture with LS. The experiments were performed in co-transport mode using NaOH as the strip phase. It was observed that extraction of mercury as well as its mixture increases with increase in concentration of NaOH up to a certain limit 0.1 M NaOH in case of pure solution and 0.2 M NaOH in case of mixture). Feed phase pH significantly affects the mercury separation process. However, initial feed concentration does not affect the extraction process appreciably. Separation of mixture of mercury and LS behaves in a similar way as their pure solution; however the extraction is low in comparison to pure solution. The extraction of mercury from its pure solution is about 81% in 1 h. The extraction of mercury and LS from their mixture is about 52.6% and 50.2%, respectively at optimum condition and in a period of 2 h. 相似文献
24.
25.
Ronhovde P Chakrabarty S Hu D Sahu M Sahu KK Kelton KF Mauro NA Nussinov Z 《The European physical journal. E, Soft matter》2011,34(9):105
We elaborate on a general method that we recently introduced for characterizing the “natural” structures in complex physical
systems via multi-scale network analysis. The method is based on “community detection” wherein interacting particles are partitioned into an “ideal
gas” of optimally decoupled groups of particles. Specifically, we construct a set of network representations (“replicas”)
of the physical system based on interatomic potentials and apply a multiscale clustering (“multiresolution community detection”)
analysis using information-based correlations among the replicas. Replicas may i) be different representations of an identical
static system, ii) embody dynamics by considering replicas to be time separated snapshots of the system (with a tunable time
separation), or iii) encode general correlations when different replicas correspond to different representations of the entire
history of the system as it evolves in space-time. Inputs for our method are the inter-particle potentials or experimentally
measured two (or higher order) particle correlations. We apply our method to computer simulations of a binary Kob-Andersen
Lennard-Jones system in a mixture ratio of A80B20 , a ternary model system with components “A”, “B”, and “C” in ratios of A88B7C5 (as in Al88Y7Fe5 , and to atomic coordinates in a Zr80Pt20 system as gleaned by reverse Monte Carlo analysis of experimentally determined structure factors. We identify the dominant
structures (disjoint or overlapping) and general length scales by analyzing extrema of the information theory measures. We
speculate on possible links between i) physical transitions or crossovers and ii) changes in structures found by this method
as well as phase transitions associated with the computational complexity of the community detection problem. We also briefly
consider continuum approaches and discuss rigidity and the shear penetration depth in amorphous systems; this latter length
scale increases as the system becomes progressively rigid. 相似文献
26.
27.
Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due
to flow separation around a square prism at Reynolds number 2.6 × 104, blockage ratio 0.1, different height-ratios and various angles of attack. The static pressure distribution has been measured
on all faces of the square prism. The results have been presented in the form of pressure coefficient, drag coefficient for
various height-ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative
values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does
not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body
approaches towards the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack
as the height-ratio decreases. The maximum value of drag coefficient has been observed at an angle of attack nearly 50° for
the square prism at all height-ratios. The heat transfer experiments have been carried out under constant heat flux condition.
Heat transfer coefficient are determined from the measured wall temperature and ambient temperature and presented in the form
of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of
local Nusselt number has been shown with non-dimensional distance for different angles of attack. The variation of average
Nusselt number has also been shown with different angles of attack. The local as well as average Nusselt number decreases
as the height-ratio decreases for all non-dimensional distance and angle of attack, respectively, for the square prism. The
average Nusselt number for the square prism varies with the angle of attack. But there is no definite angle of attack at which
the value of average Nusselt number is either maximum or minimum. 相似文献
28.
Deeparnab Chakrabarty Nikhil R. Devanur Vijay V. Vazirani 《Mathematical Programming》2011,130(1):1-32
Determining the integrality gap of the bidirected cut relaxation for the metric Steiner tree problem, and exploiting it algorithmically, is a long-standing open problem. We use geometry to define an LP whose dual is equivalent to this relaxation. This opens up the possibility of using the primal-dual schema in a geometric setting for designing an algorithm for this problem. Using this approach, we obtain a 4/3 factor algorithm and integrality gap bound for the case of quasi-bipartite graphs; the previous best integrality gap upper bound being 3/2 (Rajagopalan and Vazirani in On the bidirected cut relaxation for the metric Steiner tree problem, 1999). We also obtain a factor \({\sqrt{2}}\) strongly polynomial algorithm for this class of graphs. A key difficulty experienced by researchers in working with the bidirected cut relaxation was that any reasonable dual growth procedure produces extremely unwieldy dual solutions. A new algorithmic idea helps finesse this difficulty—that of reducing the cost of certain edges and constructing the dual in this altered instance—and this idea can be extracted into a new technique for running the primal-dual schema in the setting of approximation algorithms. 相似文献
29.
Chakrabarty Sankalpita Offen-Polak Inbal Burshtein Tomer Y. Farber Eliyahu M. Kornblum Lior Eisenberg David 《Journal of Solid State Electrochemistry》2021,25(1):159-171
Journal of Solid State Electrochemistry - The urea oxidation reaction (UOR) is an important challenge in electrocatalysis, in the context of electrolyzers, fuel cells, medical sensing, and... 相似文献
30.
Proton and alpha particle spectra have been measured in the 12C+93Nb and 12C+58Ni reactions at E(12C)=40 and 50 MeV and in the 16O + 93Nb reaction at E(16O) =75 MeV. The spectra are compared with the statistical model calculations. The shapes of the calculated spectra are in
agreement with experimental data except for the alpha spectrum in the 12C + 93Nb reaction at 40 MeV. The observed evaporation bump is at ∼2 MeV lower energy compared to the calculated one. This discrepancy
could imply alpha particle emission from a deformed configuration before compound nucleus formation at this near Coulomb barrier
beam energy. 相似文献