Unit Volume Of Liquid Research Articles

Chemical engineering kinetics of p-xylene chlorination in a gas-liquid agitated reactor

This study aims at determining both the rate constants of chlorination of p-xylene with molecular chlorine and FeCl3 as a catalyst at 70 °C and 90 °C and the related chemical engineering parameters to be used in the design of an effective chemical reactor.This was accomplished by a novel approach of constructing a linear mathematical function for a gas–liquid semi-batch agitated reactor correlating all engaged physical and chemical factors. Collecting values for all the necessary parameters for the application of the function, or in the absence of them calculating them, and exploiting the intercept and slope of the linear function became possible the apparent and the catalytic reaction rate constants to be calculated. It was found that the calculated values were of the same order of magnitude as values obtained by other researchers.The parameters needed to be calculated were Henry’s constant, the diffusion coefficient of the solute A (chlorine) to the solvent B (p = xylene), DAB, and the mean liquid phase mass transfer coefficient, kl. Other parameters of chemical engineering interest were also determined, namely, the interface per unit volume of liquid, a, the thickness of the liquid film, δl, and the Hatta number, MH.Evaluating the Hatta number estimated, it was concluded that the chlorination of p-xylene with molecular chlorine is very slow at both temperatures investigated, and almost no reaction occurs in the film compared to the bulk of the liquid. Thus, to increase the overall reaction rate, a large volume of liquid is needed while the increase of agitation intensity is of no value here.Combining the rate constant ratios obtained recently for the four consecutive second-order irreversible chlorinations of p-xylene with molecular chlorine with FeCl3 as a catalyst at 70 °C and under identical conditions it was possible to determine the values of all rate constants up to the fourth chlorinated product.

A comprehensive comparison of mixing and mass transfer in shake flasks and their relationship with MAb productivity of CHO cells

The selection of highly recombinant protein (RP)-productive Chinese hamster ovary (CHO) cell lines is widely carried out in shake flasks. It is assumed that increases in the operating parameters in shake flasks lead to impairments in cell growth and RP production. These effects in cells metabolism are widely associated with high mass transfers and hydrodynamic stress. This study examined the impact of commonly used operational parameters on growth and specific productivity (qP) of two CHO cell lines differentially secreting a humanized anti-hIL8 monoclonal antibody (mAb) and cultured in 250ml flasks. The evaluated parameters are filling volume (10, 15, and 20%), shaking frequency (60 and 120 revolutions per minute -rpm-), and orbital diameter (25.4 and 19mm). The analysis of the oxygen transfer was done in terms of the measured volumetric mass transfer coefficient (kLa) and of the hydrodynamics in terms of power input per unit volume of liquid (P/V), the turbulent eddy length scale measured by the Kolmogorov's microscale of turbulence, the energy dissipation rate, the average shear stress, and the shear rate. Though almost all measured kinetic and stoichiometric parameters remained unchanged, mAb titer included, significant differences were found in maximum cell concentration, 10-45% higher in conditions with lower values of kLa and P/V. Changes in glucose metabolism contributing to qP were only shown in the higher producer cell line. Non-lethal responses to elevated oxygen transfer and shear stress might be present and must be considered when evaluating CHO cell cultures in shake flasks.

The effect of mixing and free-floating carrier media on bioaerosol release from wastewater: a multiscale investigation with Bacillus globigii.

Aeration tanks in wastewater treatment plants (WWTPs) are significant sources of bioaerosols, which contain microbial contaminants and can travel miles from the site of origin, risking the health of operators and the general public. One potential mitigation strategy is to apply free-floating carrier media (FFCM) to suppress bioaerosol emission. This article presents a multiscale study on the effects of mixing and FFCM on bioaerosol release using Bacillus globigii spores in well-defined liquid media. Bioaerosol release, defined as percentage of spores aerosolized during a 30 minute sampling period, ranged from 6.09 × 10-7% to 0.057%, depending upon the mixing mode and intensity. Bioaerosol release increased with the intensity of aeration (rotating speed in mechanical agitation and aeration rate in diffused aeration). A surface layer of polystyrene beads reduced bioaerosol released by >92% in the bench-scale studies and >74% in the pilot-scale study. This study discovered strong correlations (R2 > 0.82) between bioaerosol release and superficial gas velocity, Froude number, and volumetric gas flow per unit liquid volume per minute. The Reynolds number was found to be poorly correlated with bioaerosol release (R2 < 0.5). This study is a significant step toward the development of predictive models for full scale systems.

Preparation and characterization of open tubular ion chromatographic columns

In recent years, significant progress has been made in the area of open tubular ion chromatography (OTIC). In particular, gradient OTIC has been realized through the development of hydroxide eluent-compatible OTIC columns. This review covers the preparation and characterization of different OTIC columns, ranging from the historic silica-based columns to the newly emerging polymer-based open tubular (OT) columns. The preparation of various OTIC stationary phases, from grafted to latex agglomerated and monolayer to multilayer phases, has been briefly introduced. The characterization of electrostatic latex agglomerated OTIC columns has been extensively discussed, e. g. fluorescent ion displacement chromatography, frontal displacement chromatography, and frontal reaction chromatography have been used to measure the capacities of OT columns, and the results are compared with the theoretical calculation values. The variable αiex, defined as the number of ion-exchange equivalents per unit surface area, is used as an indicator of the capacity of OT columns, to enable a straightforward comparison between OT columns having different inner diameters (i.d.). The newly introduced column capacity parameter, γiex, defined as the stationary phase capacity per unit liquid volume present, is used to investigate the relationship between packed and OT columns when using the same stationary phase. Methods for improving the column efficiency, such as decreasing the column diameter and/or increasing the column temperature, are presented. In addition, determination of the functionalization uniformity along an OT column by (a) separately measuring the capacities of two halves of the column, (b) measuring the retention factors for several ions in successive 10 cm segments of the column in multiple injections, and (c) measuring the retention variance of a single ion in different segments of the column from a single injection, is discussed.

Scaling-up fermentation of Escherichia coli for production of recombinant P64k protein from Neisseria meningitidis

P64k is a Neisseria meningitidis high molecular weight protein present in meningococcal vaccine preparations. The lpdA gene, which encodes for this protein, was cloned in Escherichia coli and the P64k recombinant protein was expressed in E. coli K12 GC366 cells under the control of a tryptophan promoter. P64k was expressed as an intracellular soluble protein about 28% of the total cellular protein. Several scale-up criteria of fermentation processes were studied to obtain the recombinant P64k protein at the pilot production scale. The best operational conditions at a larger scale production of P64k recombinant protein were studied and compared using the four following criteria: Constant Reynold's number (Re constant), Constant impeller tip speed (n di constant), Constant power consumption per unit liquid volume (P/V constant) and Constant volumetric oxygen transfer coefficients (KLa/k constant). The highest production of the recombinant protein was achieved based on the constant KLa/k scale-up fermentation criterion, calculating the aeration rate (Q) and the impeller agitation speed (n) by iterative process, keeping constant the KLa/k value from bench scale. The P64k protein total production at the 50 l culture scale was 546 mg l-1 in comparison with the 284 mg l-1 obtained at 1.5 l bench scale. The methodology described herein, for the KLa/k scale-up fermentation criterion, allowed us to obtain the P64k protein at 50 l scale. A fermentation process for the production of P64k protein from N. meningitidis was established, a protein to be used in future vaccine formulations in humans. How to cite: Espinosa R, García J, Narciandi E, et al. Scaling-up fermentation of Escherichia coli for production of recombinant P64k protein from Neisseria meningitidis. Electron J Biotechnol 2018;33. https://doi.org/10.1016/j.ejbt.2018.03.004.

Ion exchange column capacities. Predicting retention behavior of open tubular columns coated with the same phase

We discuss the reported capacities of available packed ion exchange columns and the different methods used for their measurement. We outline basic considerations related to both packed and open tubular columns based on ion exchange latex particles.There is a large body of information covering the retention behavior of packed ion exchange columns based on ion exchange latex particles. We propose a parameter γiex, which is the ion exchange capacity of a column (packed or open tubular) per unit liquid volume present in the column (including accessible volume within pores) and show that the retention factor for any given ion is directly related to γiex. On this basis, if based on the same type of latex, the behavior of one type of column can be reasonably predicted from the known behavior of the other, even when the absolute capacities differ by more than 5 orders of magnitude.

Scaling-up fermentation of Escherichia coli for production of recombinant P64k protein from Neisseria meningitidis

Background: P64k is a Neisseria meningitidis high molecular weight protein present in meningococcal vaccine preparations. The lpdA gene, which encodes for this protein, was cloned in Escherichia coli and the P64k recombinant protein was expressed in E. coli K12 GC366 cells under the control of a tryptophan promoter. P64k was expressed as an intracellular soluble protein about 28% of the total cellular protein. Several scale-up criteria of fermentation processes were studied to obtain the recombinant P64k protein at the pilot production scale. Results: The best operational conditions at a larger scale production of P64k recombinant protein were studied and compared using the four following criteria: Constant Reynold's number (Re constant), Constant impeller tip speed (n di constant), Constant power consumption per unit liquid volume (P/V constant) and Constant volumetric oxygen transfer coefficients (KLa/k constant). The highest production of the recombinant protein was achieved based on the constant KLa/k scale-up fermentation criterion, calculating the aeration rate (Q) and the impeller agitation speed (n) by iterative process, keeping constant the KLa/k value from bench scale. The P64k protein total production at the 50 l culture scale was 546 mg l-1 in comparison with the 284 mg l-1 obtained at 1.5 l bench scale. Conclusions: The methodology described herein, for the KLa/k scale-up fermentation criterion, allowed us to obtain the P64k protein at 50 l scale. A fermentation process for the production of P64k protein from N. meningitidis was established, a protein to be used in future vaccine formulations in humans.

Computational hydrodynamic comparison of a mini vessel and a USP 2 dissolution testing system to predict the dynamic operating conditions for similarity of dissolution performance

The hydrodynamic characteristics of a mini vessel and a USP 2 dissolution testing system were obtained and compared to predict the tablet-liquid mass transfer coefficient from velocity distributions near the tablet and establish the dynamic operating conditions under which dissolution in mini vessels could be conducted to generate concentration profiles similar to those in the USP 2. Velocity profiles were obtained experimentally using Particle Image Velocimetry (PIV). Computational Fluid Dynamics (CFD) was used to predict the velocity distribution and strain rate around a model tablet. A CFD-based mass transfer model was also developed. When plotted against strain rate, the predicted tablet-liquid mass transfer coefficient was found to be independent of the system where it was obtained, implying that a tablet would dissolve at the same rate in both systems provided that the concentration gradient between the tablet surface and the bulk is the same, the tablet surface area per unit liquid volume is identical, and the two systems are operated at the appropriate agitation speeds specified in this work. The results of this work will help dissolution scientists operate mini vessels so as to predict the dissolution profiles in the USP 2, especially during the early stages of drug development.

Power Dissipation and Power Number Correlations for a Retreat-Blade Impeller under Different Baffling Conditions

Glass-lined tanks/reactors provided with a torispherical (dish) bottom and equipped with a retreat-blade impeller (RBI) are commonly used in the industrial syntheses of Active Pharmaceutical Ingredients (APIs). The power, P, dissipated by the RBI in the liquid in the tank is critical to many mixing processes, especially since the power per unit liquid volume, P/V, controls many mixing phenomena. Despite their common industrial use, limited information on P for RBIs and the corresponding nondimensional Power number, Po, is available. Here, P values for an RBI in liquids of very different viscosities at different agitation speeds and for different baffling configurations, i.e., unbaffled, partially baffled (with a single “beavertail” baffle), and fully baffled (four rectangular baffles), were measured experimentally in a scaled-down version of a typical reactor for API synthesis. The corresponding Po values were obtained for a large range of the Reynolds number, Re (1 < Re < 400,000). Po was found to vary s...

Preparation of ruthenium-loaded CNT–TiO2 nanohybrids and their catalytic performance for the selective oxidation of benzyl alcohol

CNT–TiO 2 nanohybrids were synthesized using CNTs as a substrate and isopropyl titanate as a titanium source by a hydrothermal method. The nanohybrids were characterized by SEM and XRD, and their dispersion ability as an emulsion was investigated by optical microscopy. Ruthenium was loaded onto TiO 2 and the nanohybrids by an impregnation method, and their catalytic performance was evaluated by the selective oxidation of benzyl alcohol to benzylaldehyde. The mechanism involved in the reaction was proposed. Results show that the dispersion ability of the CNT–TiO 2 nanohybrids, judged by the numbers of uniform oil droplets in water per unit liquid volume, is better than that of TiO 2 . The catalytic activity and selectivity of the Ru/CNT–TiO 2 for the selective oxidation reactions are higher than for Ru/TiO 2 , indicating that they are closely related to the dispersion ability of the catalysts as emulsions. [New Carbon Materials 2013, 28(4): 289–294]

New Correlations of Volumetric Liquid-Phase Mass Transfer Coefficients in Gas-Inducing Agitated Tank Reactors

Abstract Volumetric liquid-phase mass transfer coefficient (kLa) is one of the most important parameters for the evaluation of the performance of a gas-inducing agitated tank (GIAT). In this paper, two equations in terms of power input per unit liquid volume (P/VL) and relative gas dispersion parameter (NI/Ncd), respectively, are developed according to data in literature. They can correlate existing kLa values within ±20% of measured ones for bladed impellers with different impeller submergence to tank diameter ratios in the range of 0.5 -1.23. In order to validate these equations, the liquid phase mass transfer coefficients in a continuous GIAT equipped with a 4-blade straight impeller were measured by removal of oxygen from water. It was found that the equation in P/VL criterion could correlate kLa values within ±12% of the experimental data, and the equation in NI/Ncd criterion could correlate kLa values within ±15.6% with an exception of 26.8% for NI = 16.7 Hz.

A comprehensive comparison of mixing, mass transfer, Chinese hamster ovary cell growth, and antibody production using Rushton turbine and marine impellers

Large scale production of monoclonal antibodies has been accomplished using bioreactors with different length to diameter ratios, and diverse impeller and sparger designs. The differences in these physical attributes often result in dissimilar mass transfer, mechanical stresses due to turbulence and mixing inside the bioreactor that may lead to disparities in cell growth and antibody production. A rational analysis of impeller design parameters on cell growth, protein expression levels and subsequent antibody production is needed to understand such differences. The purpose of this study was to examine the impact of Rushton turbine and marine impeller designs on Chinese hamster ovary (CHO) cell growth and metabolism, and antibody production and quality. Experiments to evaluate mass transfer and mixing characteristics were conducted to determine if the nutrient requirements of the culture would be met. The analysis of mixing times indicated significant differences between marine and Rushton turbine impellers at the same power input per unit volume of liquid (P/V). However, no significant differences were observed between the two impellers at constant P/V with respect to oxygen and carbon dioxide mass transfer properties. Experiments were conducted with CHO cells to determine the impact of different flow patterns arising from the use of different impellers on cell growth, metabolism and antibody production. The analysis of cell culture data did not indicate any significant differences in any of the measured or calculated variables between marine and Rushton turbine impellers. More importantly, this study was able to demonstrate that the quality of the antibody was not altered with a change in the impeller geometry.

Development of microbubble aerator for waste water treatment using aerobic activated sludge

In large-scale waste water treatment plants, the aerobic biochemical reactor is the most important process, where the oxygen supply into the microorganisms often limits the overall waste water treatment rate. On the other hand, several kinds of microbubble distributors have been developed to enrich the oxygen dissolution in water. Therefore, the application of microbubbles for a waste water treatment system was investigated in this study. The oxygen absorption performance of typical microbubble generators was compared with typical bubble generators. To evaluate each bubble generator, the liquid-phase volumetric oxygen transfer coefficient, gas hold-up and power consumption per unit liquid volume were measured in a bubble column attached to each bubble generator. All the microbubble generators allowed the oxygen to dissolve faster than the typical aerators. The spiral liquid flow type microbubble generator had the highest oxygen transfer coefficient even at a low air flow rate although it used more energy than the typical distributors. To improve an industrial waste water treatment system, a novel aeration system utilizing a spiral liquid flow type microbubble generator was proposed in this study. The present system has some advantages such as compact size, portability and fast oxygen dissolution rate. To ensure the performance for organic waste water treatment, the effects of the aeration rate, dissolved oxygen concentration and device properties on the specific consumption rate of model organic waste were investigated. For the novel aeration system, the most suitable conditions to treat organic waste were found.

Simulating bubble number density of rhyolitic pumices from Plinian eruptions: constraints from fast decompression experiments

Decompression experiments of a crystal-free rhyolitic liquid with ≈ 6.6 wt. % H2O were carried out at a pressure range from 250 MPa to 30–75 MPa in order to characterize effects of magma ascent rate and temperature on bubble nucleation kinetics, especially on the bubble number density (BND, the number of bubbles produced per unit volume of liquid). A first series of experiments at 800°C and fast decompression rates (10–90 MPa/s) produced huge BNDs (≈ 2 × 1014 m−3 at 10 MPa/s ; ≈ 2 × 1015 m−3 at 90 MPa/s), comparable to those in natural silicic pumices from Plinian eruptions (1015–1016 m−3). A second series of experiments at 700°C and 1 MPa/s produced BNDs (≈ 9×1012 m−3) close to those observed at 800°C and 1 MPa/s (≈ 6 × 1012 m−3), showing that temperature has an insignificant effect on BNDs at a given decompression rate. Our study strengthens the theory that the BNDs are good markers of the decompression rate of magmas in volcanic conduits, irrespective of temperature. Huge number densities of small bubbles in natural silicic pumices from Plinian eruptions imply that a major nucleation event occurs just below the fragmentation level, at which the decompression rate of ascending magmas is a maximum (≥ 1 MPa/s).

Effect of Ultrasonic Irradiation on Chemical Reaction in Iodine Solution Decolorization Experiment

In order to investigate the region of effective chemical reaction field in a sonoreactor, the power input per unit volume of liquid and the liquid height were varied. Decolorization experiments using iodine and disodium hydrogenphosphate in a starch solution under chemical reaction rate control conditions were carried out and the effect of ultrasonic irradiation on the chemical reaction was examined. The region of the effective chemical reaction field depended on the power input per unit volume dissipated in the liquid but did not depend on the liquid height. With increasing the power input per unit volume of the liquid, the region of the effective chemical reaction field became larger and the effective chemical reaction rate increased.

Experimental determination of dissociation constant, Henry's constant, heat of reactions, SO 2 absorbed and gas bubble–liquid interfacial area for dilute sulphur dioxide absorption into water

The experimental results for dissociation constant, Henry's constant, heat of reactions and gas bubble–liquid interfacial area for absorption of dilute SO 2 (SO 2 partial pressure upto 0.963 kPa) into water in bubble column are presented. The relations between Henry's constant versus temperature and dissociation constant versus temperature have been proposed based on the present experimental investigation. The temperature dependence on gas bubble–liquid interfacial area per unit volume of liquid has examined. Result shows a very small decrease in interfacial area with increase in temperature. The experimental results are used to correlate total SO 2 absorbed at saturation as function of temperature and SO 2 partial pressure. Comparisons between experimental results and literature data have also been made at different temperatures. The reasonable fittings between the data obtained from correlation and literature data shows that the proposed correlation can be successfully used for predicting the absorption equilibria of dilute SO 2 in distilled water at different temperatures.

Comparison of mass transfer efficiency in horizontal rotating packed beds and rotating biological contactors

AbstractIn this study, the mass transfer efficiencies of a novel horizontal rotating packed (h‐RPB) bed and the conventional disc‐type rotating biological contactor (RBC) were studied at four speeds and seven submergences. Pall rings of two different sizes (25, 38 mm), superintalox saddles and a wiremesh spiral bundle were used as packings in the h‐RPB. Volumetric gas–liquid mass transfer coefficients were determined by unsteady state absorption of atmospheric oxygen in de‐aerated water. Power consumption per unit liquid volume has been found for all geometries tested. The oxygen transfer efficiency values for the h‐RPB were found to be 2–5 kg kWh−1 and for the disc RBC were found to be 1–2 kg kWh−1. The performance of the h‐RPB was also compared with other gas–liquid contactors such as surface aerators. The study proves that the h‐RPB is a energy efficient alternative to conventional contactors. Copyright © 2005 Society of Chemical Industry

The measurement of bubble diameter distributions and liquid side mass transfer coefficients in a gas-liquid agitated vessel using a real-time,high-speed image processing system

In this study, we report the measurement results of various spatial distributions, such as Sauter diameter, gas holdup ratio, and interface area per unit liquid volume, in a vessel using a real-time, high-speed image processing system developed by ourselves. We attempted to separate liquid side mass transfer coefficients, k L , from overall volumetric mass transfer coefficients, k L a, based on the results mentioned above. And we examined the relations between power consumption per unit volume, P v , and both k L and k L a in order to establish correlation equations of k L and k L a with P v , gas holdup ratio, gas superficial velocity, v s , and surface tension.

Spray Charging of Droplets in a Wet Scrubber

The experimental setup was designed to study the effect of natural charging of droplets during spraying (called spray electrification or spray charging) in a wet scrubber. The influence of nozzle material, liquid feed rate, and liquid composition on the specific charge (charge per unit volume of liquid) formed in spraying was measured. It was found that the nozzle material has no measurable effect on this specific charge. Increasing the liquid feed rate increases the specific charge significantly. Increasing solute (NaCl or NaOH) concentration increases the conductivity that decreases the formed specific charge. The same correlation between the specific charge and conductivity was also observed with real scrubbing liquids. It is proposed that the specific charge depends only on the value of liquid conductivity, not on liquid composition. The conductivity of the tested scrubbing liquids was high enough to suppress the formation of a high specific charge during spraying.

Assembly of a Thin-Falling-Film Exchanger for Laboratory Demonstrations: Calculation of the Individual Heat-Transfer Coefficient

Thin-film exchangers have a large heat-transfer area per unit liquid volume that make them very efficient for industrial use. Unfortunately, they are usually less applied for education purposes. In this work, a simple experimental device with a fluid flowing as a falling film has been assembled. In addition, an experimental guide allows students to determine the individual heat-transfer coefficient in the exchanger.