Values Of Mass Transfer Coefficient Research Articles

KINETIKA DESORPSI UREA DARI KARBON BERPORI TEROKSIDASI ASAM SULFAT SEBAGAI SLOW RELEASE FERTILIZER

Urea is an important nitrogen source for plant but the price of urea fertilizer is relatively high. Urea uptake from urea manufacture waste water and its application as fertilizer is of high interest. The purpose of this study is to find out desorption ability of urea adsorbed porous carbon to be applied as fertilizer. Theoritically, urea released from porous carbon to environment has slower rate of mass transfer compare to conventional urea fertilizer because urea molecules in porous carbon has to pass through pores of carbon during its movement out of carbon. The porous carbon as adsorbent was made from coconut shell by pyrolysis, followed by sulfuric acid oxidation treatment Oxidation treatment carried out to extent adsorption capacity as well as to give additional sulfur nutrient when applied as fertilizer. Oxidation of carbon surface was performed using sulfuric acid (50%w) to soak porous carbon followed by heating at 90oC temperature for 2 hours. Desorption was conducted by placing porous carbon into beaker contain water and the raising of urea concentration in water recorded after 3,5,10, 30, and 60 minutes. Results reveal that the value of mass transfer coefficient (kc) and effective diffusivity (De) of urea desorption from porous carbon are 0,0293 – 0,0743 cm/s and 8 x 10-10 – 5 x 10-9 cm2/s with initial concentration of urea 1000, 2000, and 4000 mg/L. Release rate of urea from porous carbon and urea prill are 0,07 ppm/s and 1,23 ppm/s. Slower release rate of urea off porous carbon than urea prill shows the promising of urea recovery using porous carbon as slow release fertilizer.

Production of Recombinant Human Asparaginase from Escherichia coli under Optimized Fermentation Conditions: Effect of Physicochemical Properties on Enzyme Activity

The recombinant human asparaginase (rhASP) plays an important role in the treatment of acute lymphoblastic leukemia. In the present work, volumetric mass transfer coefficient (kLa) values are derived from the E. coli cultivation under different agitation and aeration conditions, in order to improve the rhASP productivity. The aeration and agitation conditions were systematically optimized by the kLa. The maximum biomass (2.4 g/L) and rhASP (1.68 g/L) are achieved with the kLa of 0.024 s-1 at 1.5 lpm and 700 rpm process conditions. The kinetic properties of purified rhASP are also extensively studied and optimized for the maximal enzyme activity. The optimal pH, temperature and incubation duration conditions for accomplishing maximum enzyme activity are found to be 9.0, 40°C, and 30 min, respectively. The optimum substrate concentration and substrate specificity for the highest enzyme activity are of 0.07 M and L-asparagine, respectively. The enzyme activity (204 IU/mL) is significantly improved in the presence of sodium metal (Na+) ions and the inhibitors 2- mercaptoethanol, bromoacetic acid and urea have presented the highest inhibition rate on rhASP activity. The enzyme kinetic parameters Km and Vmax of the purified rhASP are recorded as 2.25 mM and 250 IU/mL, respectively. This work provides the extensive characteristic properties of rhASP enzyme, which enables us to place in a competition for the development of oncology drugs.

Modeling of a liquid membrane in Taylor flow integrated with lactic acid fermentation

The application of a liquid membrane in Taylor flow (LMTF) is a promising method that can be integrated with other separation or reactive processes in view of process intensification. In this work, a model for a hybrid LMTF – fermentation system was developed for lactic acid production using batch fermentation and LMTF experimental data. The hybrid model is compared to experimental data of the hybrid system. Through a sensitivity analysis of the main variables of the LMTF an optimum value of the overall volumetric mass transfer coefficient (0.0122 1/s) was achieved for lactic acid removal. This was further used for modeling the hybrid system. The fermentation time of the hybrid system is reduced by 7 h, the productivity and biomass concentration is increased by 2.578 g/(L·h) and 2.7016 g/L, respectively, as compared with a batch fermentation. In addition, the effect of the number of channels of the LMTF is modeled and its impact on productivity, fermentation time, and final biomass concentration is analyzed. It was concluded that lactic acid removal through the LMTF from the fermentation broth is an alternative to control the pH within fermenter.

Experimental study on the mass transfer performance of a horizontal pulsed column for uranium recovery from a sulfate leach liquor with Alamine 336 using mathematical model

In this investigation, the concentration profiles in both phases were determined for the uranium extraction from a sulfate solution by Alamine 336 in a horizontal pulsed column. The leach liquor solution contained uranium, iron, magnesium, manganese, aluminum, calcium and other minor elements. The optimum operating parameters for uranium extraction have been carried out at the bench scale. An organic phase with 6% (v/v) Alamine 336 and 5% (v/v) isodecanol in kerosene was chosen to examine the mass transfer performance of the extraction column. The volumetric overall mass transfer of the continuous phase, backmixing parameters and axial dispersion coefficients of two phases were calculated by using plug flow, backflow and axial dispersion models. The influence of operating parameters such as pulsation intensity and phase flow rates on these parameters was studied. The values of volumetric overall mass transfer coefficient calculated by axial dispersion are greater than those models. Because the axial mixing improves the mass transfer performance of this column. The obtained results of the pilot plant experiments showed that the mass transfer performance of this column is high for the uranium extraction from sulfate leach liquors. Furthermore, the practical and novel correlations have been determined for prediction of mass transfer parameters (such as Koca, Ec, Ed, α, β), which are closely matched with the experimental results in the horizontal pulsed column.

Application of microchemical technology in mass transfer behavior contrastive research of rare earth extraction

The solvent extraction of Sm (III) by P507 were carried out in both serpentine Y-junction and T-junction micro flow reactors to contrast the mass transfer behavior in these two kinds of reactors. Dispersed slugs were periodically observed in both reactors by a high-speed camera with the aid of microscope. Slug length and specific interface area were determined by the Scopephoto software, slug flow gradually decreased their own size and specific interface area inconspicuously affected by the variation of flow rate, whereas the values of volumetric mass transfer coefficients showed the greater positive correlation trend. The volumetric mass transfer coefficients vary between 0.007 and 0.039 s−1 in T-junction micro flow reactor, which is two orders of magnitude lower compared to Y-junction micro flow reactor (0.310 to 1.139 s−1). These studies indicate that Y-junction micro flow reactors could better enhance the solvent extraction than T-junction micro flow reactors, and the contrastive results could be a significant reference for the implementation of micro flow reaction in rare earth extraction industry.

Microplastic-Contaminant Interactions: Influence of Nonlinearity and Coupled Mass Transfer.

Microplastic particles are ubiquitously detected in the environment. Despite intensive public and scientific discussions, their potential to transport contaminants in rivers and oceans under environmental conditions is still under assessment. In the present study we measured sorption isotherms and kinetics in batch experiments using phenanthrene (as a typical hydrophobic wastewater contaminant) and microplastic particles of different sizes and materials. We observed a linear sorption isotherm for polyethylene, in contrast to nonlinear sorption of polyamide and polystyrene, which could be best described by the Freundlich and the Polanyi-Dubinin-Manes isotherms, respectively. We modeled sorption kinetics as a combination of external mass transfer governed by diffusion through an aqueous boundary layer and intraparticle diffusion within the plastic. Which of these processes controls the kinetics depends on the sorption strength, particle size, diffusion coefficients, and time. We used semi-analytical and numerical methods to simulate the coupled mass transfer for both linear and nonlinear sorption. We successfully applied the semi-analytical model to polyethylene and the numerical code to polyamide and polystyrene, reproducing the measured kinetics and obtaining reasonable values for mass transfer and intraparticle diffusion coefficients. Subsequently, we used these coefficients to estimate the transport potential and relevant time scales for microplastic-bound contaminants under environmental conditions. Environ Toxicol Chem 2019;38:1635-1644. © 2019 SETAC.

The Effect of Various Nanofluids on Absorption Intensification of CO2/SO2 in a Single-Bubble Column

Application of nanoparticles in aqueous base-fluids for intensification of absorption rate is an efficient method for absorption progress within the system incorporating bubble-liquid process. In this research, SO2 and CO2 were separately injected as single raising bubbles containing nanofluids to study the impact of nanoparticle effects on acidic gases absorption. In order to do this, comprehensive experimental studies were done. These works also tried to investigate the effect of different nanofluids such as water/Al2O3 or water/Fe2O3 or water/SiO2 on the absorption rate. The results showed that the absorption of CO2 and SO2 in nanofluids significantly increases up to 77 percent in comparison with base fluid. It was also observed that the type of gas molecules and nanoparticles determine the mechanism of mass transfer enhancement by nanofluids. Additionally, our findings indicated that the values of mass transfer coefficient of SO2 in water/Al2O3, water/Fe2O3 and water/SiO2 nanofluids are, respectively, 50%, 42% and 71% more than those of SO2 in pure water (kLSO2-water=1.45×10-4 m/s). Moreover, the values for CO2 in above nanofluids were, respectively, 117%, 103% and 88% more than those of CO2 in water alone (kLCO2-water=1.03×10-4 m/s). Finally, this study tries to offer a new comprehensive correlation for mass transfer coefficient and absorption rate prediction.

Modelling and parameter estimation of breakthrough curves for amine-modified activated carbons under pre-combustion carbon capture conditions

Pressure swing adsorption (PSA) demonstrates high potential for capturing pre-combustion carbon dioxide in Integrated Gasification Combined Cycle (IGCC) power plants, due to a binary mixture of hydrogen and carbon dioxide entering the separation process. In this work, a seven-step PSA model was developed and compared to adsorption experiments under PSA conditions (25 bar and ambient temperatures) performed with tetraethylenepentamine (TEPA) and a novel blend of monoethanolamine-monodiethanolamine (MEA-MDEA) modified activated carbons, using nitrogen and carbon dioxide mixtures. The MEA-MDEA modified activated carbon showed promising results for pre-combustion PSA processes, due to their high carbon dioxide adsorption capacity and delayed break-point of about 200 s compared to the unmodified activated carbons. A sensitivity analysis carried out for the adsorbent parameters in a seven-step PSA process showed that high mass transfer coefficient values yielded to highly purified products, specifically for the light product stream (99.4%). A sensitivity analysis of the process variables showed that purity values of the heavy stream (carbon dioxide) were over 90% when the purge pressure was reduced to 0.5 bar and the carbon dioxide feed fraction increased to 60%.

Comparative study of the batch adsorption kinetics and mass transfer in phenol-sand and phenol-clay adsorption systems

This study was aimed at evaluating the kinetics and mass transfer of phenol adsorption onto sand and clay sediments. The adsorption studies were carried out in batch mode. The results showed that the time taken to attain equilibrium in the adsorption of phenol onto sand and clay sediments are 21 and 27 h, respectively. At an equal given time, clay sediments relatively had higher adsorption of phenol than sand sediments, which can be ascribed to its large surface area and higher porosity. The kinetic data adjusted well to the pseudo-first-order and Elovich kinetic models; however, Elovich kinetic model best describe the phenol adsorption kinetics. Mass transfer models were applied to the adsorption data to evaluate the rate-limiting step in the adsorption of phenol onto the sand and clay sediments. The values of the external mass transfer coefficient and diffusion coefficient were estimated from the models. Biot number was determined using the estimated internal mass transfer (intraparticle diffusion) coefficient and the external mass transfer coefficient. From the applied models and the calculated Biot number, the results revealed that the mechanism of phenol adsorption onto sand and clay sediments was not only by intraparticle diffusion but also by film diffusion.

Evaluation of the adsorption kinetics of brilliant green dye onto a montmorillonite/alginate composite beads by the shrinking core model

Montmorillonite/alginate composite beads have been studied for adsorption of brilliant green dye in batch experiments. The geometry and features of this clay/polymer composite, in combination with the strong color of the dye, were very useful to apply and test in a simple way the shrinking core model (SCM). This model is very popular for describing adsorption in porous systems, but not in clay/polymer composite beads. The SCM describes the adsorption as a diffusion process of the adsorbate through a spherical shell. The great advantage of using the clay and the dye is that they allow observing with the naked eye or through digital photographs the progress of the front of adsorption (penetration radius) as the reaction takes place. This was never informed in the literature. The experimental changes in penetration radius and dye concentration with time were compared with SCM predictions at different initial concentrations of brilliant green. There was an excellent agreement between theory and experiments, and thus the kinetics of the process could be thoroughly evaluated. The estimated values of the parameters liquid phase mass transfer coefficient and effective diffusion coefficient in the adsorbent are kf > 0.00008 m s−1 and Dp = 5 × 10−10 m2 s−1 respectively.

Development of ammonia mass transfer coefficient models for the atmosphere above two types of the slatted floors in a pig house using computational fluid dynamics

Ammonia emissions from animal production systems are a concern due to their potential adverse effects on the environment. It is important for governments to adjust their policies to control ammonia emissions from animal production. To evaluate and quantify emission factors, process-based modelling is a cost-effective procedure, particularly due to the complex and diverse transfer chains. During the modelling process, ammonia mass transfer coefficient is one of the key parameters to be determined. However, inconsistencies are found in widely used expressions for mass transfer coefficients in ammonia volatilization models. This study used CFD simulations to derive the mass transfer coefficients above metal and concrete slatted floor in an experimental pig houses with 12 full-scale pig pens. Five ammonia mass transfer coefficient models were selected for comparison with the models derived from CFD simulations. It was noticed that the models derived from wind tunnel/flux chamber experiments usually predicted lower values of ammonia mass transfer coefficients compared to the models developed from full-scale measurements and/or numerical modelling. Care is needed to extrapolate the relationships developed under controlled laboratory conditions to the commercial barns. The results indicated also that the ammonia mass transfer coefficient relies heavily on the airflow patterns which could be affected by the ventilation systems, location of the inlet and outlets, internal partitions, floor types etc.. This makes it very difficult to present a universal ammonia mass transfer coefficient model for pig houses.

Determination of reactive mass transfer coefficients for CO2 absorption predictions

ABSTRACTAbsorption of carbon dioxide (CO2) by solvents is an important process in many practical applications such as capture of greenhouse gases from flue gas, gas processing in the chemical and petroleum industries, capture of radioactive isotopes in the nuclear cycle, etc. High pH alkaline solutions were used in this research project to capture CO2. The chemical reaction between CO2 and the hydroxyl ion is known to significantly increase the absorption rate compared to the same process without chemical reaction. The goal of this work is to study the influence of the chemical reaction on the absorption rate. For this purpose, the gas-liquid mass transfer coefficient was measured under reactive and nonreactive conditions. Reactive mass transfer coefficient values were higher than similar ones without chemical reaction. Under the operating conditions used in this work, the mass transfer process was found to be controlled by the liquid phase resistance.

Effect of pH and Gas Flow Rate on Ozone Mass Transfer of Κ-Carrageenan Solution in Bubble Column Reactor

This research was conducted to calculate the mass transfer coefficient value for ozonation reaction of κ-carrageenan solution in the bubble column reactor. Ozone gas was produced using ozone generator type corona discharge. In this study, operating conditions were regulated at ozone gas flow rate 2- 5 L min-1, pH 4-10, and temperature 29 ± 1 oC. Samples were tested every 5 minutes to determine the dissolved ozone concentration. The results showed that dissolved ozone concentrations increased with increasing ozonation time and ozone gas flow rate. However, a very high gas flow rate can increase turbulence so that the mass transfer coefficient (kLa) value decreased. In alkaline conditions, the formation of free radicals (HO*) increases so that the amount of dissolved ozone decreases. The kLa value of ozone gas in κ-carrageenan solution is slightly lower than the kLa value of the ozone gas in the water. The results of this study indicate that (kLa) ozone gas in water is 0.131 / minute while the value (kLa) in κ-carrageenan solution is 0.128 / minute.Keywords: ozone; mass transfer; pH; flowrate

Measurement of Gas-Phase Mass Transfer Coefficients in a Humidification Column through Random Packing

Packed columns are an important part of the broad selection of mass and heat transfer equipment. Nowadays, the use of packed columns is increasing, which is because of its lower pressure drop, higher capacity and higher mass transfer in comparison to tray columns. The experiential tests and the hypothetical analysis display that the chemical dehumidification of air by hygroscopic salt solutions confirms the stable reduction in humidity ratio, which is appropriate for uses to air conditioning or drying processes The mass transfer factors in the pulse were found to correspond nearly to the factors that would be achieved in the distributed bubble flow regime In the present study, parameters that affect column performance, such as, fluid retention and gas-phase mass transfer coefficient in a humidification column using random packing in towers with 0.1 m and 0.2 m diameters and 1m height, were measured Air velocity was 1.32 to 3.92 m3 per hour and liquid velocity was 10 to 70 m3 per hour. In this research, the Nakajima model was used to calculate the effective area. Thereafter, experimental values for gas-phase mass transfer coefficients were compared to Zech, Shi, Grouff, Shulman, Billet and Ondamodels The mean relative errors of these models with the present study’s experimental findings were 7%, 15%, 29%, 21%, 45% and 195%. Findings showed that by decreasing the column diameter, the gas-phase mass transfer coefficient (Kg.ae) also increases Further, the obtained retention values showed that retention in the column with a 0.1 m diameter was higher than the column with a 0.2 m column.

Intensified solvent extraction and separation of cobalt from Ni-rich leaching solution in impinging stream-rotating packed bed contactor

ABSTRACT This work describes the separation of Ni and Co from a real feed solution in chloride media with high Ni content. The extractant used was P507 (2-ethylhexyl phosphoric acid-2-ethylhexyl ester) in a laboratory scale Impinging Stream–Rotating Packed Bed (IS-RPB) contactor. Key variables including feed solution pH, extractant concentration, saponification degree, high gravity level and total volumetric flow rate of fluids amongst other variables were examined. A McCabe–Thiele diagram of the extraction stage predicted that at a total volumetric flow rate of 90 L/h, feed solution pH of 5, saponified P507 concentration of 25% and high gravity of 83, almost 99% of cobalt, would be extracted within three stages. With regard to the scrubbing results, the co-extracted nickel was scrubbed efficiently from the loaded organic solution using a mixture of 0.02 M CoCl2 and 0.5 M hydrochloric acid solution, The purified Co solution was achieved after stripping the loaded-organic phase with 1 M HCl. The maximum value of the overall volumetric mass transfer coefficient for the IS-RPB extractor was found to be 0.16 s−1 which was superior to that of conventional extractors such as mixer-settler and centrifugal extractors, providing strong confidence for its industrial application.

Mass transfer from a soluble Taylor bubble to the surrounding flowing liquid in a vertical macro tube — A numerical approach

Gas–liquid mass transfer is a phenomenon with a wide practical relevance and, besides many other possible advantages, its fundamentals can be used to enhance or regulate chemical and biological processes. In this work, the specific case of the mass transfer of oxygen from a Taylor bubble to the surrounding flowing liquid was studied using CFD techniques. This study was performed for a range of flow conditions (different Reynolds numbers) and a liquid with a viscosity (and constant Morton number) typical of bio-fluids. The flow field, gas–liquid interface and concentration field were determined simultaneously by coupling the VOF methodology with the species mass balance equation and setting a constant solute concentration at the bubble surface. The mass transfer behavior on the different hydrodynamic regions (nose, film and tail) was inspected and quantified based on local coefficients. It was possible to verify that these values increase along the nose and reach a maximum at the fully developed film region, where it tends to stabilize regardless of the bubble length (for bubble lengths between 2D and 9D). An opposite tendency was found along the bubble tail, where a decrease was verified on the local mass transfer coefficient values. Average mass transfer coefficients based on the simulation data were also determined. The comparison of these results with theoretical predictions allowed to infer that the film theory is the most adequate to describe the gas–liquid mass transfer between a Taylor bubble and the surrounding liquid.

Experimental Investigations on Solid-Liquid Mass Transfer in GLS Fluidized Beds at low Reynolds Numbers

Solid -Liquid mass transfer coefficient (K) was measured in Gas-Liquid-Solid Fluidized Beds by using the system of dissolution of benzoic acid in water. Benzoic acid pellets of various diameter- height combinations were prepared by pelletizing machine and effect of various parameters (superficial gas velocity, superficial liquid velocity, Reynolds number, particle Reynolds number based on gas and liquid velocity) on mass transfer of benzoic acid pellets in water has been studied. It was observed gas velocity plays an important role on mass transfer coefficient value. The effect of Reynolds number based on superficial gas velocity on rate of mass transfer was investigated with varying liquid velocity, bed height and pellet size. Increase in mass transfer coefficient was observed with increase in gas velocity, liquid velocity, bed height at fixed pellet size. As the pellet size decreases in one run, increase in mass transfer with increasing rate of remaining parameter was observed. Comparative study on effect of Reynolds number and particle Reynolds number along with liquid velocity, gas velocity on mass transfer has been shown that mass transfer coefficient increases with increase in Reynolds no., liquid velocity, gas velocity, bed height and with decrease particle Reynolds number.

Nano-gate opening pressures for the adsorption of isobutane, n-butane, propane, and propylene gases on bimetallic Co-Zn based zeolitic imidazolate frameworks.

In this article, zeolitic-imidazolate framework-8 (ZIF-8) and its mixed metal CoZn-ZIF-8 were synthesized via a rapid microwave method. The products were characterized by Raman spectroscopy, XPS, XRD, EDX, TEM, NanoSEM, TGA, and DSC. The gas adsorption properties of samples were determined using C3 and C4 hydrocarbons, including propane, propylene, isobutane and n-butane at a temperature of 25 °C. The adsorption equilibrium and kinetics of these gases on various ZIFs were studied. It was noted that ZIF-8 and mixed metal CoZn-ZIF-8 samples start to adsorb these gases after certain pressures which are believed to result in the opening of their nano-gates (i.e., 6-membered rings) to allow the entry of gas molecules. The nanogate opening pressure value (p0) for each ZIF towards different gases was determined by fitting adsorption equilibrium data against a modified form of the Langmuir adsorption isotherm model. It was observed that the value of p0 differs significantly for each gas and to various extents for various ZIFs. Therefore, it is possible that the distinct values of p0 afford a unique technique to separate and purify these gases at the industrial scale. The overall mass transfer coefficient values of the adsorption process were also investigated.

On the nanogate-opening pressures of copper-doped zeolitic imidazolate framework ZIF-8 for the adsorption of propane, propylene, isobutane, and n-butane

In this study, a zeolitic imidazolate framework-8 (ZIF-8) and its copper-doped variants (Cu-doped ZIF-8) were synthesized using a rapid microwave technique. The products were characterized by XRD, NanoSEM, FTIR, Raman spectra, TGA, XPS, and EDX. The gas adsorption properties of samples were performed using C3 and C4 hydrocarbons including propane, propylene, isobutane, and n-butane gases at 25 °C. Both equilibrium adsorption and kinetics were studied. It was found that ZIF-8 and Cu-doped ZIF-8 samples open their nanogates (i.e., six-membered rings) at some threshold pressures when adsorbing different gases, which it is denotes later as the gate-opening pressure (p0). The p0 value for each ZIF toward each gas was evaluated by fitting equilibrium adsorption data against a modified version of the Langmuir adsorption isotherm model. It was observed that the value of p0 differs significantly for each gas utilized, and with different extents for ZIF samples. The overall mass transfer coefficient values of adsorption process were estimated. Therefore, it is possible that the distinct values of p0 afford a unique chance to separate and purify these gases at mass production, and the best-studied adsorbent to for this purpose was Cu30%/ZIF-8.

Electrochemical degradation of Azo-dye Acid Violet 7 using BDD anode: effect of flow reactor configuration on cell hydrodynamics and dye removal efficiency

The electrochemical oxidation of synthetic textile effluent containing Azo-dye Acid Violet 7 (200 mg L−1) was investigated using planar disk electrodes placed in a one inlet–outlet (I–O) cylindrical reaction chamber. Two different I–O configurations were studied, one parallel and the other perpendicular to the electrodes. Both reactors were equipped with boron-doped diamond (BDD) anodes and titanium cathodes. The effect of cell design on the hydrodynamic characteristics and efficiency of the reactors in terms of colour and chemical oxygen demand (COD) removal was studied. Mass transfer coefficient (Km) values of 1.86 × 10−5 m s−1 and 2.56 × 10−5 m s−1 were obtained for the parallel and perpendicular I–O flow reactors, respectively, using the limiting current technique. The degradation results indicated that the colour elimination was quite efficient regardless of the type of reactor used and that complete colour removal could be reached in less than 80 min at applied current density of 30 mA cm−2 and above. However, higher COD removal efficiency was always achieved in the parallel I–O flow cell compared to perpendicular I–O flow reactor at all of the current densities studied, which can be attributed to the possibility of some stagnation in the lateral regions of the electrodes. These favour a longer contact time between the pollutants and the anode, also favouring its removal. Besides, similar electric energy consumption per g COD removal was observed during the treatment with either reactors; thus demonstrating the suitability of the parallel I–O flow cell for the efficient and economic treatment of textile effluent.