Parthasarathi Ray

Removal of mercury from its aqueous solution using charcoal-immobilized papain (CIP).

In the present work mercury has been eradicated from its aqueous solution using papain, immobilized on activated charcoal by physical adsorption method. Operating parameters for adsorption of papain on activated charcoal like pH, amount of activated charcoal, initial concentration of papain in solution have been varied in a suitable manner for standardization of operating conditions for obtaining the best immobilized papain sample based on their specific enzymatic activity. The immobilized papain sample obtained at initial papain concentration 40.0 g/L, activated charcoal amount 0.5 g and pH 7 shows the best specific enzymatic activity. This sample has been designated as charcoal-immobilized papain (CIP) and used for further studies of mercury removal. Adsorption equilibrium data fit most satisfactorily with the Langmuir isotherm model for adsorption of papain on activated charcoal. Physicochemical characterization of CIP has been done. The removal of mercury from its simulated solution of mercuric chloride using CIP has been studied in a lab-scale batch contactor. The operating parameters viz., the initial concentration of mercury in solution, amount of CIP and pH have been varied in a prescribed manner. Maximum removal achieved in the batch study was about 99.4% at pH 7, when initial metal concentration and weight of CIP were 20.0mg/L and 0.03 g respectively. Finally, the study of desorption of mercury has been performed at different pH values for assessment of recovery process of mercury. The results thus obtained have been found to be satisfactory.

Removal of mercury (II) from aqueous solution using papain immobilized on alginate bead: Optimization of immobilization condition and modeling of removal study

Papain having the characteristics of metal binding ability is immobilized on alginate bead. Design Expert Software (Version 7.1.6) uses Response Surface Methodology (RSM) for statistical designing of operating condition for immobilization of papain on alginate bead considering concentration of papain, concentration of sodium alginate, concentration of calcium chloride and pH as numeric factors and Specific Enzymatic Activity (SEA) of immobilized papain sample as response. Immobilization using 25.96 g/L papain, 20 g/L sodium alginate and 20 g/L calcium chloride at pH 7 gives the desired product as indicated by ANOVA (Analysis of Variance). Three parameters viz., initial concentration of mercury (II), amount of AIP and pH are varied in a systematic manner. Maximum 98.88% removal of mercury (II) has been achieved within 8 min when simulated aqueous solution of mercury (II) with initial concentration of 10mg/L has been contacted with 5 g of AIP at pH 9 and at 35 degrees C in a batch contactor. A mathematical model has been developed and the value of equilibrium constant for binding of mercury (II) with AIP has been found to be 126797.3.

GAS ABSORPTION WITH INSTANTANEOUS CHEMICAL REACTION IN A FALLING FILM FOR PARALLEL AND COUNTERCURRENT FLOWS

A theoretical analysis is presented for the absorption of a gas accompanied by instantaneous chemical reaction with a dissolved reagent in a falling liquid film of liquid. The reaction occurs on a moving front inside the liquid film separating the zones containing either of the reactants. The governing equations are solved by using a coordinate transformation to immobilize the reaction front. The effects of the different system parameters on the reaction front profile, absorption rate and enhancement factor are presented for both cocurrent and countercurrent flow of the gas. In the former case the reaction front profile shows a maximum, but in the later case it is monotonic in the axial distance along the film. The enhancement factor plots exhibit maxima in both the cases.

Stoffaustausch mit chemischer Reaktion in einem laminaren rieselfilm

Es wird eine analytische Losung fur die Absorption in einem laminaren Rieselfilm mit homogener und heterogener chemischer Reaktion 1. Ordnung vorgestellt, wobei der Stofftransportwiderstand auf der Gasseite liegt. Die Losung ist eine Funktion von drei dimensionslosen ParameternBi, α undβ, welche die BiotZahl und einen homogenen bzw. heterogenen Reaktionsparameter darstellen. Es wird gezeigt, das fur feste Werte vonBi undα die Absorptionsrate (bezogen auf die Breite 1 des Rieselfilms) uber eine gewisse Lange ξ (dimensionslos) des Rieselfilms unabhangig vonβ ist, wennξ, < 0,6 ist. Die laufende Langeξ wird von der Stelle aus gemessen, an der die Absorption beginnt. Furξ ≧b 0,6 nimmt der FlusQ mitβ zu, erreicht aber einen Sattigungswert beiβ=10, wonachQ nurmehr sehr langsam anwachst. Jedoch fur ein gegebenesβ und ohne Ubergangswiderstand im Film (Bi → ∞) nimmtQ mitα fur alleξ ≧ 0 zu.An analytical solution is presented for gas absorption in a laminar falling film with first-order homogeneous and heterogeneous chemical reaction and external gas-phase mass transfer resistance. The solution depends on three dimensionless parametersBi,α andβ, wich represent the Biot number, homogeneous and heterogeneous reaction parameters, respectively. It is shown that for fixed values ofBi andα, the rate of gas absorption (per unit breadth) over a certain lengthξ; (dimensionless) along the falling film measured from the point where surface absorption begins is independent ofβ ifξ < 0.6. Forξ ≧ 0.6, this fluxQ increases withβ but reaches a saturation value atβ=10 beyond whichQ increases very slowly. But for givenβ and zero gas film resistance (Bi → ∞),Q increases withα for allξ ≧ 0.ZusammenfassungEs wird eine analytische Lösung für die Absorption in einem laminaren Rieselfilm mit homogener und heterogener chemischer Reaktion 1. Ordnung vorgestellt, wobei der Stofftransportwiderstand auf der Gasseite liegt. Die Lösung ist eine Funktion von drei dimensionslosen ParameternBi, α undβ, welche die BiotZahl und einen homogenen bzw. heterogenen Reaktionsparameter darstellen. Es wird gezeigt, daß für feste Werte vonBi undα die Absorptionsrate (bezogen auf die Breite 1 des Rieselfilms) über eine gewisse Länge ξ (dimensionslos) des Rieselfilms unabhängig vonβ ist, wennξ, < 0,6 ist. Die laufende Längeξ wird von der Stelle aus gemessen, an der die Absorption beginnt. Fürξ ≧b 0,6 nimmt der FlußQ mitβ zu, erreicht aber einen Sättigungswert beiβ=10, wonachQ nurmehr sehr langsam anwächst. Jedoch für ein gegebenesβ und ohne Übergangswiderstand im Film (Bi → ∞) nimmtQ mitα für alleξ ≧ 0 zu.

Studies on removal of lead(II) by Alginate Immobilized Bromelain (AIB)

AbstractThe work is based on augmentation of active sites of calcium alginate bead by immobilizing bromelain to remove lead(II) from simulated solution. The optimum immobilization condition as specified by response surface methodology is as follows: initial concentration of sodium alginate, bromelain, and calcium chloride are 20, 21.09, and 20 g/L, respectively, at pH 7 and 35°C and the sample, thus prepared, is termed as alginate immobilized bromelain (AIB). Maximum 99.5% lead(II) has been removed when 30 mL lead(II) solution having initial concentration of 0.0048 mmol L−1 has been treated with 5 g of AIB at pH 7 and 35°C. 77.9% lead(II) has been recovered when 1 g of spent adsorbent is stirred in 100 mL of solution having pH 2 for 30 min. The removal of lead(II) using AIB and, thereby, simultaneous inhibition of enzyme have been modeled both statistically and empirically.

Non-isothermal enhancement factor for mass transfer with instantaneous reaction in a rigid drop

Abstract Mass transfer between liquid drops and a surrounding fluid with an accompanying instantaneous chemical reaction is important in a number of industrial processes. For small drops which behave as rigid particles the coupled transport-reaction phenomenon occurs through a moving boundary mechanism. Here we present a theoretical analysis of the problem under non-isothermal conditions by considering the continuous phase diffusional resistance. The relevant transport equations are subjected to a coordinate transformation in order to immobilize the reaction front. Computed results for the enhancement factor and interfacial temperature rise are presented for a wide range of relevant system parameters. The results show enhancement factor and interfacial temperature rise maxima and some other interesting features that can be explained on a physical basis.

Selectivity behaviour of non-uniform catalysts for the consecutive reactions A → B → C

Abstract The effect of non-uniform catalytic activity distribution on product selectivity in the consecutive reaction scheme A → B → C has been investigated for a single catalyst pellet and also for a fixed bed reactor containing non-uniform catalyst pellets, taking into consideration independent variations in the catalytic activities for the reaction steps A → B and B → C and the non-zero concentration of the product B at the catalyst surface. Except with very small values of Thiele moduli, on-uniform activity distribution has a significant effect on selectivity. For a single catalyst pellet a combination of shell type catalytic activity distribution for the reaction A → B and core type distribution for B → C appears to give the best product selectivity. In a packed bed reactor the local selectivity decreases along the reactor, depending on the modified Damkohler number.

Exact analysis of laminar dispersion in non-Newtonian flow

An exact analysis is presented for dispersion of a solute in an Eyring model fluid flowing between two parallel plates under uniform pressure gradient. Using a generalised dispersion model, which is valid for all time after injection of the solute, expressions have been developed for the time-dependent longitudinal dispersion coefficient as well as of the area-mean concentration. It is observed that the dispersion coefficient markedly decreases as the fluid parameterG increases, which is attributable to the gradual flattening of the velocity profile. Consequently the concentration distribution becomes steeper at largerG. It is also established that forG<1, the extent of dispersion is practically same as in the case of Newtonian flow.ZusammenfassungEs wird eine exakte Analyse für eine Dispersion in einer „Eyring-Modellflüssigkeit“ vorgestellt, die zwischen zwei parallelen Platten unter gleichmäßigem Druckgefälle fließt. Es wurden sowohl Formeln für den zeitabhängigen Longitudinaldispersionskoeffizienten, als auch für die mittlere Umgebungskonzentration entwickelt, wobei ein allgemeines Dispersionsmodell benutzt wurde, welches für den ganzen Zeitraum nach dem Einleiten der Lösung gültig ist. Es wird beobachtet, daß der Dispersionskoeffizient deutlich abnimmt, wenn der FlüssigkeitsparameterG sich erhöht, was bezeichnend für die allmähliche Abflachung des Geschwindigkeitsprofils ist. Folglich wird die Konzentrationsverteilung mit steigendemG steiler. Es wurde bewiesen, daß für G ≦ 1 die Ausdehnung der Dispersion praktisch mit der Newtonschen Strömung identisch ist.