Biomedical subjects

Aniruddha B Pandit

Publications and source records attributed to Aniruddha B Pandit.

At least 19 recordsLinked to original sources

PubMed2007

Mapping the efficacy of new designs for large scale sonochemical reactors.

Sonochemical reactors have a great promise for many physical and chemical processing applications but its applicability at pilot or industrial scale levels is hindered by lack of novel designs which can reproduce the spectacular effects generated at the laboratory scale. The present work evaluates the efficacy of two new designs, operating at a liquid capacity of 7l. Mapping of the cavitational activity has been carried out using measurements of local pressure using hydrophone and cativational intensity using Cavitation Activity Indicator (Model IC-3, N. Deznukov, Belarus State University, Minsk, Belarus). Aim has been to identify the distribution of the cavitational activity in radial and axial directions and possibly characterizing the zones with very high and very low cavitational activity in these reactor configurations. It has been observed that the cavitational activity is substantially uniform in both the reactors unlike the conventional single transducer based reactors. The study clearly indicates the feasibility of these designs for future large scale applications.

Journal Article↗

PubMed2007

Cavitation--a novel technique for making stable nano-suspensions.

The purpose of the present study was to obtain nano-scale particles of styrene butadiene rubber. As SBR particles are elastic in nature, conventional methods of size reductions such as impacting, grinding are unable to achieve the final size. So, attempts have been made here to make the nano-particles of the SBR using cavitation technique. Both acoustic and hydrodynamic cavitation techniques have been employed and studied. Hydrodynamic cavitation has been proved to be more energy efficient than the acoustic cavitation on the basis of various parameters. The maximum production rate equivalent to 2 kg/h (solid processing) has been achieved in the newly developed hydrodynamic cavitation set-up (made in house). Similar to transient cavitation, stable cavitation has also been shown to contribute for reduction in the size of the material with very low variation in size. This technique has been proved successful for the size-reduction of the elastic material to nano-scale, thus it may also be used for the size-reduction of the other brittle and hard material by adjusting various cavitational parameters.

Butadienes↗

PubMed2006

Selective synthesis of sulfoxides from sulfides using ultrasound.

The present work aims at developing a new process to selectively synthesize sulfoxide from sulfides using ultrasound. Methyl phenyl sulfide (MPS) has been taken as a model reactant. The reaction has been carried out in ultrasonic bath with an operating frequency of 22 kHz and maximum power supply of 120 W with an actual power dissipation of approximately 40 W measured using calorimetric studies. Effect of various parameters such as presence and absence of catalyst, type of catalyst (catalysts used were sodium tungstate and ammonium molybdate), temperature, concentration of hydrogen peroxide, effect of molar ratio of MPS to H(2)O(2) has been investigated with an aim of obtaining the optimum conditions for the synthesis of sulfoxides. It was observed that the presence of catalyst is a must to achieve appreciable conversions. It was also observed that the periodic addition of stoichiometric amount of hydrogen peroxide instead of sudden addition of it (total quantity of hydrogen peroxide remains the same) gave better selectivity for sulfoxide. The maximum conversion achieved in the present work was approximately 88.42% with sulfone formation being only 0.4% indicating a 99.6% selectivity for the desired product i.e. sulfoxides.

Journal Article↗

PubMed2006

Destruction of formic acid using high frequency cup horn reactor.

Degradation of formic acid has been studied in a high frequency cup horn type reactor with an aim of understanding the effect of operating parameters on the destruction efficiency. The methodology used in the work serves as a useful guideline for the optimization exercise for the sonochemical reactors to establish a set of operating parameters at large scale operation for achieving maximum efficiency. Firstly energy efficiency of the reactor has been established as a function of the operating volume with an aim of optimization of the capacity of the reactor for maximum extent of degradation. It has been observed that maximum transfer of supplied power is obtained at 300 ml capacity and hence the actual degradation studies have been performed with this operational capacity. The effect of time of irradiation, initial concentration of the pollutant, stirrer speed, presence of sodium sulfite (to scavenge the initial dissolved oxygen) on the extent of degradation has been investigated. Maximum extent of degradation has been observed under the conditions of 500 mg/l initial concentration, 200 rpm stirrer speed and presence of initial dissolved oxygen (no sodium sulfite in the system). Process intensification studies have been carried out using sodium chloride over a range of initial concentration and it has been observed that maximum extent of degradation of formic acid is obtained at 4% NaCl concentration. Comparison has been also made with different sonochemical configurations operating at lower frequency of irradiation (typically in the range of 20-50 kHz) with an aim of comparing the efficacies of the reactor at equivalent power consumption.

Formates↗

PubMed2005

Process intensification using cavitation: optimization of oxidation conditions for synthesis of sulfone.

Cavitation can be effectively used for intensification of chemical reactions due to the production of free radicals and conditions of high temperatures and pressures locally. In the present work, use of cavitation for the intensification of the synthesis of sulfone has been explored. The oxidation of thioether or sulfide to synthesize corresponding sulfone with 30% H(2)O(2) as an oxidant was studied under acoustic cavitation and the results have been compared with the conventional approach based on the use of mechanical agitation. The aim has been also to optimize the different operating conditions viz. molar ratio of reactants to the oxidizing agent, type of the catalyst as well as its concentration, type of the solvent and the reactant concentration, so as to maximize the degree of intensification. It was observed that under the optimized conditions of sonication, the yield of sulfone was about five to six times higher as compared to the conventional approach of using mechanical agitation only.

Catalysis↗

PubMed2005

Ultrasound and enzyme assisted biodegradation of distillery wastewater.

Irradiation with ultrasound (US) and use of an enzyme (E) as pretreatment techniques were carried out to treat a complex effluent (distillery wastewater). These two techniques have been used alone as well as in combination and the efficacy of these techniques was tested by subjecting the effluent to subsequent aerobic biological oxidation (AO). When used alone, US exposure for 30 min and 2 h yielded the best COD reduction during the aerobic oxidation step (US+AO). For the enzyme when used alone, a pH value of 4.8 (corresponding to the optimum pH of the enzyme), a dose of 50 U and a pretreatment time of 24 h yielded better COD removal efficiency as compared to untreated effluent (aerobic oxidation alone). When used in combination, ultrasound followed by enzymatic pretreatment (US+E+AO) yielded the best COD removal efficiencies during aerobic oxidation as compared to the other combinations tested for the treatment of the distillery wastewater. A 4-fold increase in the initial oxidation rate was observed over the untreated batch for the integrated technique (US+E+AO). On the basis of the variation in the values of the biokinetic parameters it can be concluded that the type of pretreatment scheme affects the subsequent rate of the aerobic oxidation significantly.

Aerobiosis↗

PubMed2005

Ultrasonic atomization: effect of liquid phase properties.

Experiments have been conducted to understand the mechanism by which the ultrasonic vibration at the gas liquid interface causes the atomization of liquid. For this purpose, aqueous solutions having different viscosities and liquids showing Newtonian (aqueous solution of glycerin) and non-Newtonian behavior (aqueous solution of sodium salt of carboxy methyl cellulose) were employed. It has been found that the average droplet size produced by the pseudo-plastic liquid is less than that produced by the viscous Newtonian liquid having viscosity equal to zero-shear rate viscosity of the shear thinning liquid. The droplet size was found to increase initially with an increase in the viscosity up to a certain threshold viscosity after which the droplet size was found to decrease again. Also droplet size distribution is found to be more compact (uniform sizes) with an increasing viscosity of the atomizing liquid. The presence of the cavitation and its effect on the atomization has been semi quantitatively confirmed using energy balance and by the measurement of the droplet ejection velocities and validated on the basis of the decomposition of the aqueous KI solution. A correlation has been proposed for the prediction of droplet size for aqueous Newtonian fluids and fluids showing non-Newtonian behavior based on the dimensionless numbers incorporating the operating parameters of the ultrasonic atomizer and the liquid phase physico-chemical properties.

Journal Article↗

PubMed2005

Enhancement in biodegradability of distillery wastewater using enzymatic pretreatment.

A combined treatment technique consisting of enzymatic hydrolysis, followed by aerobic biological oxidation was investigated for the treatment of alcohol distillery spent wash. The enzyme cellulase was used for the pretreatment step with an intention of transforming the complex and large pollutant molecules into simpler biologically assimilable smaller molecules. Batch experiments were performed in order to analyze the influence of various parameters like pretreatment time, enzyme concentration and pH during the pretreatment step on the subsequent aerobic oxidation kinetics. The rate of aerobic oxidation was enhanced by 2.3 fold for the pretreated sample as compared to the untreated sample when the pH during the pretreatment step was maintained at a value of 4.8. Similarly, a two fold increase in the aerobic oxidation rate was found when the effluent was pretreated with the enzyme, without any pH control (i.e. effluent pH of 3,8). The study indicated that the enzymatic pretreatment of the effluent could be one of the successful pretreatments which can lead to enhancement of the rate of the subsequent aerobic oxidation.

Aerobiosis↗

PubMed2005

Effect of additives on ultrasonic degradation of phenol.

Sonication for phenol degradation has proved to be an attractive process over the years at least on a laboratory scale but the rates of phenol degradation under sonication have always been quite low. The present work investigates the use of simple additives such as salt and carbon tetrachloride as process intensifying parameters with an aim of reduction in the treatment times and hence the cost of operation. The intermediates formed in the degradation process have been analyzed and it has been observed that these intermediates degrade faster as compared to phenol. A hybrid technique of ozonation coupled with cavitation has also been investigated with an objective of finding the optimum conditions for the combination of ozonation and cavitation for synergistic effects. Analysis of the intermediates for the combination treatment scheme also indicates that the intermediates (hydroquinone, catechol, resorcinol, maleic acid, acetic acid, oxalic acid, formic acid, etc.) are more biodegradable prompting a possible combination of cavitation with aerobic oxidation for large scale treatment of phenol containing waste.

Carbon Tetrachloride↗

PubMed2005

A review and assessment of hydrodynamic cavitation as a technology for the future.

In the present work, the current status of the hydrodynamic cavitation reactors has been reviewed discussing the bubble dynamics analysis, optimum design considerations, design correlations for cavitational intensity (in terms of collapse pressure)/cavitational yield and different successful chemical synthesis applications clearly illustrating the utility of these types of reactors. The theoretical discussion based on the modeling of the bubble dynamics equations aims at understanding the design information related to the dependency of the cavitational intensity on the operating parameters and recommendations have been made for the choice of the optimized conditions of operating parameters. The design information based on the theoretical analysis has also been supported with some experimental illustrations concentrating on the chemical synthesis applications. Assessment of the hydrodynamic cavitation reactors and comparison with the sonochemical reactors has been done by citing the different industrially important reactions (oxidation of toluene, o-xylene, m-xylene, p-xylene, mesitylene, o-nitrotoluene, p-nitrotoluene, m-nitrotoluene, o-chlorotoluene and p-chlorotoulene, and trans-esterification reaction i.e., synthesis of bio-diesel). Some recommendations have also been made for the future work to be carried out as well as the choice of the operating conditions for realizing the dream of industrial scale applications of the cavitational reactors.

Computer Simulation↗

PubMed2005

Investigation of induction of air due to ultrasound source in the sonochemical reactors.

A detailed investigation into the phenomena of induction of air using a novel arrangement of the ultrasonic horn (tip is located just above the liquid surface) has been made with the quantification of the extent of induction in terms of the air entrainment rate and the gas-liquid mass transfer coefficient for the transfer of air into the system. The measurement of air entrainment rate was found to be quite difficult and hence focus was kept on the quantification in terms of the gas-liquid mass transfer coefficient. The effect of ultrasonic power dissipation and type of the liquid medium (water, sodium chloride and sodium laruyl sulphate [surfactant] solution) on the mass transfer coefficient has been studied and correlations have been developed for the prediction of the same. Comparison with the mechanically agitated surface aerators has enabled us to understand the controlling mechanism in the induction and subsequent distribution of the air i.e. turbulence or convective motion. The present work should open an entirely new field of research in the area of design of sonochemical gas-liquid reactors operating possibly as a combination of gas-inducing reactors and cavitational reactors.

Journal Article↗

PubMed2005

Dynamics of cavitational bubbles and design of a hydrodynamic cavitational reactor: cluster approach.

In the present work, a cavity cluster of predetermined size has been considered to study the bubble dynamics in the hydrodynamic cavitation reactor. The effect of different operating and system parameters on the cavitational intensity has been numerically investigated. The yield of any cavitationally induced physical/chemical transformations depends not only on the collapse pressure of the cavities but also on the active volume of cavitation within the reactor. Empirical correlations have been developed to predict the collapse pressure and the active volume of cavitation as a function of different operating parameters based on the bubble dynamics studies. Recommendations are made for designing a cavitational reactor on the basis of the proposed empirical correlations. This work is a first step towards the designing and optimization of hydrodynamic cavitational reactor with cluster approach.

Journal Article↗

PubMed2005

Degradation kinetics of folic acid in cowpea (Vigna catjang L.) during cooking.

Kinetics of folic acid degradation in cowpea (Vigna catjang L.) as well as in pure folic acid solutions at initial concentrations present in cowpea over a temperature range of 50-120 degrees C (isothermal conditions) followed first order reaction kinetics, where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by Arrhenius equation. The degradation was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient Eco Cooker (non-isothermal heating process). A mathematical model was developed using the isothermal kinetic parameters obtained to predict the losses of folic acid from the time-temperature data of the non-isothermal heat processing method. The results obtained indicate the folic acid degradation is of a similar order of magnitude in all the methods of cooking.

Cooking↗

PubMed2004

Sonochemical reactors: scale up aspects.

The present work deals with the discussion on the engineering aspects of the design of large-scale sonochemical reactors using the solutions of the bubble dynamics equations as well as experimentation with different reactor types and reactions. Design correlations for the collapse pressure and its relation to the cavitational yield have also been given which should assist the designers in the choice of the operating parameters for a desired cavitational effect. Some techniques for the intensification of cavitational activity (with the use of additives) with an aim of reducing the cost of operation have also been discussed. The guidelines for the future work to be carried out to remove the lacunae in the design information with an aim of developing industrial scale efficient sonochemical reactors have also been mentioned.

Journal Article↗

PubMed2004

Ultrasonic bath with longitudinal vibrations: a novel configuration for efficient wastewater treatment.

Efficacy of a novel configuration for large-scale wastewater treatment applications has been investigated using formic acid degradation as a model reaction. The reactor is first characterized using energy efficiency measurements and the optimum operating volume for maximum transfer of supplied energy and hence maximum cavitational effects has been established. Effect of initial concentration of the pollutant on the rates of degradation has been investigated. Comparison has been also made with the conventional ultrasonic horn in terms of energy efficiency and cavitational yield for the model reaction. With an aim of possible reduction in the total treatment time, some intensification studies have been undertaken considering hydrogen peroxide as an additional source of free radicals.

Journal Article↗

PubMed2004

Ultrasound pre-treatment for enhanced biodegradability of the distillery wastewater.

Studies were carried out to the find out the efficacy of the ultrasonic irradiation as a pre-treatment step for the treatment of one of the polluting industrial effluents, the distillery spentwash. Experiments were carried out on the fresh and stored effluent samples. The effect of the ultrasound exposure on the biodegradability of the effluent was monitored by carrying out its subsequent aerobic oxidation. A comparison has been made between the efficacies of the pre-treated samples with the untreated samples. The results indicate that the ultrasound seems to increase the attractiveness of the conventional aerobic oxidation process by increasing their initial rates of degradation.

Aerobiosis↗

PubMed2004

Static foam destruction: role of ultrasound.

High intensity ultrasonic vibrations were used for destabilizing the static foam structure. Ultrasonic horn as a source of ultrasonic vibration was used for the destruction of the foam. The effect of the ratio of the horn to the column diameter on the drainage and collapse rate of foam has been analyzed. Further, an empirical correlation for the initial foam collapse rate in the presence of ultrasonic horn has been developed in terms of the initial liquid hold-up, surface tension of the surfactant solution and the ratio of horn diameter to the column diameter. Efficiency of the ultrasonic horn is related to the position of the tip of the horn. Periodic supply of ultrasonic vibrations was found to be a more viable option than the continuous supply in terms of saving in energy and operating cost for defoaming using ultrasound.

Journal Article↗

PubMed2004

A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking.

The kinetics of ascorbic acid degradation in amla (Phyllanthus emblica L.) as well as in pure ascorbic acid solutions at initial concentrations present in amla over a temperature range of 50-120 degrees C (steady-state temperature) has been studied. The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by the Arrhenius equation. The activation energies were found to be 4.09 kcal/mole for amla and 4.49 kcal/mole for pure vitamin solution. The degradation kinetics of ascorbic acid was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient EcoCooker (unsteady state heating process). A mathematical model was developed using the steady-state kinetic parameters obtained to predict the losses of ascorbic acid from the time-temperature data of the unsteady state heating processing method. The results obtained indicate the ascorbic acid degradation is of a similar order of magnitude in all the methods of cooking.

Ascorbic Acid↗