Pinaki Bhattacharya

Removal of arsenic from drinking water by chemical precipitation - a modeling and simulation study of the physical-chemical processes

A dynamic mathematical model was developed for removal of arsenic from drinking water by chemical coagulation-precipitation and was validated experimentally in a bench-scale set-up. While examining arsenic removal efficiency of the scheme under different operating conditions, coagulant dose, pH and degree of oxidation were found to have pronounced impact. Removal efficiency of 91-92% was achieved for synthetic feed water spiked with 1 mg/L arsenic and pre-oxidized by potassium permanganate at optimum pH and coagulant dose. Model predictions corroborated well with the experimental findings (the overall correlation coefficient being 0.9895) indicating the capability of the model in predicting performance of such a treatment plant under different operating conditions. Menu-driven, user-friendly Visual Basic software developed in the study will be very handy in quick performance analysis. The simulation is expected to be very useful in full-scale design and operation of the treatment plants for removal of arsenic from drinking water.

Effect of Physicochemical Parameters on the Separation of Proteins from Human Placental Extract by Using a Continuous Foam Fractionating Column

Abstract The recovery of valuable proteins (like proteolytic enzymes) from nonconventional biological sources by using modern separation techniques is becoming increasingly important because of their high commercial potential. In the present investigation, isolation of proteins from human placental extract by using the continuous foam fractionation technique is studied. The effect of different physicochemical parameters on the separation of proteins and purification of proteolytic enzymes are reported. A method for finding a quasi-equilibrium relationship between the solute concentration in the foamate and in the effluent by using the same system is described. The quasi-equilibrium curve is also presented.

Effect of pH and temperature on stability and kinetics of novel extracellular serine alkaline protease (70 kDa).

A novel extracellular serine protease (70 kDa by SDS-PAGE) was purified and characterized. This enzyme retained more than 93% of its initial activity after preincubation for 30 min at 37 °C in the presence of 25% (v/v) tested organic solvents and showed feather degradation activity. The purified enzyme was deactivated at various combinations of pH and temperature to examine the interactive effect of them on enzyme activity. The deactivation process was modeled as first-order kinetics and the deactivation rate constant (k(d)) was found to be minimum at pH 9 and 37 °C. The kinetic analysis of enzyme over a range of pH values indicated two pK values at 6.21 and at 10.92. The lower pK value was likely due to the catalytic histidine in the free enzyme and higher pK value likely reflected deprotonation of the proline moiety of the substrate but ionization of the active site serine is another possibility. Inhibition kinetic showed that enzyme is serine protease because enzyme was competitively inhibited by antipain and aprotinin as these compounds are known to be competitive inhibitors of serine protease. The organic solvent, thermal and pH tolerances of enzyme suggested that it may have potential for use as a biocatalyst in industry.

Studies on separation characteristics and pseudo-equilibrium relationship in pervaporation of benzene-cyclohexane mixtures through composite PVA membranes on PAN supports

Abstract Batch pervaporation of benzene–cyclohexane mixtures was carried out using a composite membrane—PERVAP® 2200 (Sulzer Chemtech), and the relevant separation characteristics investigated. Separation factor for this system was found to be 60–70. The effects of physico-chemical parameters like initial solute concentration and feed hold-up volume on permeate flux were studied. A new concept of ‘pseudo-equilibrium’ state in pervaporation was proposed and data of the benzene–cyclohexane system presented.

Optimization of culture condition for growth and phenol degradation by Alcaligenes faecalis JF339228 using Taguchi Methodology

Abstract The optimization of five process parameters such as pH, agitation, temperature, inoculum percentage and incubation time were optimized by Taguchi robust design method for obtaining enhanced biomass and phenol degradation by the isolated Alcaligenes faecalis JF339228 from Durgapur steel industry (DSP), India. About 18 experiments were conducted with a different combination of factors and the results obtained in terms of growth of specific bacterial strain and phenol degradation rates were processed in the Qualitek-4 software to study the main effect of individual factors. The main effect, interaction effects and optimal levels of the process factors were determined using signal-to-noise (S/N) ratio. The effect of factors has been studied for bacterial growth and phenol degradation by A. faecalis JF339228. Optimization of the said parameters has been evaluated by Taguchi method and analysed by analysis of variance. Predicted results showed enhanced process performance such as biomass (131.78%) and ...

Simulation and modeling of continuous H2 production process by Enterobacter cloacae IIT-BT 08 using different bioreactor configuration

Abstract Simulation and modeling of continuous H 2 production by Enterobacter cloacae IIT-BT 08 using different bioreactor configurations have been carried out and a suitable kinetic model for the substrate degradation has been proposed, assuming ideal plug flow, no axial dispersion, steady state and first-order substrate degradation kinetics. The degradation kinetics was investigated as a function of flow rates considering the gas hold-up in all the bioreactors. The external film diffusion model of the type J D = KN Re −(1− n ) is proposed for a tubular bioreactor and J D is found to be constant in the present system. The same model is applied to both tapered and rhomboidal bioreactors and was found to give reasonably good fit with experimental results with respect to substrate conversion. Comparison of the external mass transfer coefficient k l with the observed first-order reaction rate constant k p predicted by the model shows that the effect of external film diffusion on the observed substrate degradation rate decreases with increasing flow rates. For the present system, both substrate degradation and mass transfer steps are the limiting factor for the observed substrate degradation rate, particularly at higher dilution rates.

Rheological and Mechanical Properties of LDPE/HDPE Blends

Melt rheology and mechanical properties of binary blend of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated. Four different wt fractions of blends containing LDPE/HDPE (20/80, 40/60, 60/40, and 80/20) were prepared. Cole-Cole plots [storage melt viscosity (η′) vs. loss melt viscosity (η″)] and relation between storage melt viscosity (η′) with frequency (ω) and blend composition were constructed. Miscibility of blends was established from rheological data. Impact strength of the blends increased with increasing LDPE concentration, whereas tensile strength shows the opposite trends. Percentages of the crystallinity of the blends were calculated by both the differential scanning calorimetry and wide-angle X-ray scattering methods, which show that the percentage of crystallinity decreased with increasing LDPE concentration, but the rate of crystallization of HDPE phase was unaffected.

Multi-enzyme immobilization in eco-friendly emulsion liquid membrane reactor: a new approach to membrane formulation

Abstract Multi-enzymes (α-glucosidase and glucose oxidase) have been immobilized in emulsion liquid membranes for using such membranes as eco-friendly enzyme emulsion liquid membrane (EELM) reactors. Role of surfactant-stabilized liquid membranes as separation-concentration devices changes here to that of promising, eco-friendly reactors where product is transported to the external phase thereby eliminating the need for demulsification for subsequent recovery of product and membrane phase material for reuse. Thus tradeoffs among stability, selective permeability and ease of demulsification get significantly modified necessitating a new approach to membrane formulation. With this new approach to membrane formulation, the present investigations have been carried out. Stability aspect has been studied measuring leakage through such membranes using a tracer technique while permeability has been measured during actual enzymatic reactions inside the emulsion globules and transportation of the product outside the membranes. Effects of agitation, surfactant concentration, internal phase volume fraction, membrane phase material and non-Newtonian conversion of membrane phase on the stability of liquid membranes, as well as product generation and permeation have been investigated. In presence of carrier and additional stabilizer (polystyrene 1% by wt.), emulsion liquid membranes have been found to yield the best results with a surfactant concentration of 3.5–4 wt.% at an agitation of 300 rpm and with an internal phase volume fraction of 0.5. The findings are expected to be very useful in developing emulsion liquid membranes as efficient enzyme-encapsulating bioreactors.

De-mercurization of wastewater by Bacillus cereus (JUBT1): Growth kinetics, biofilm reactor study and field emission scanning electron microscopic analysis

Removal of mercuric ions by a mercury resistant bacteria, called Bacillus cereus (JUBT1), isolated from the sludge of a local chlor-alkali industry, has been investigated. Growth kinetics of the bacteria have been determined. A multiplicative, non-competitive relationship between sucrose and mercury ions has been observed with respect to bacterial growth. A combination of biofilm reactor, using attached growth of Bacillus cereus (JUBT1) on rice husk packing, and an activated carbon filter has been able to ensure the removal of mercury up to near-zero level. Energy dispersive spectrometry analysis of biofilm and the activated carbon has proved the transformation of Hg(2+) to Hg(0) and its confinement in the system.

Process engineering studies to investigate the effect of temperature and pH on kinetic parameters of alkaline protease production.

An in depth process engineering study on the effect of temperature and pH on kinetic parameters of alkaline protease production by Bacillus licheniformis NCIM-2042 using starch as substrate has been reported.