Magnetically Stabilized Fluidized Bed Research Articles

Preparation of magnetic poly(ethylene glycol dimethacrylate-N-Methacryloyl-(L)-glutamic acid) particles for thrombin purification

In this study, magnetic poly(ethylene glycol dimethacrylate-N-methacryloyl-(L)-glutamic acid) (mPEGDMA-MAGA) particles were prepared by the dispersion polymerization in order to purify thrombin effectively. mPEGDMA-MAGA particles were synthesized by adding different ratios of magnetite (Fe3O4) to the medium in addition to the monomer phases EGDMA and MAGA. The characterization studies of mPEGDMA-MAGA particles were used by fourier transform infrared spectroscopy, zeta size measurement, scanning electron microscopy and electron spin resonance. mPEGDMA-MAGA particles were used in thrombin adsorption studies from aqueous thrombin solutions in both batch and magnetically stabilized fluidized bed (MSFB) system. Maximum adsorption capacity in pH 7.4 phosphate buffer solution is 964 IU/g polymer and 134 IU/g polymer in MSFB system and batch system, respectively. The developed magnetic affinity particles enabled the separation of thrombin from different patient serum samples in one step. It has also been observed that magnetic particles can be used repeatedly without significant reduction in adsorption capacity.

Immobilization of Laccase on Magnetic Chelator Nanoparticles for Apple Juice Clarification in Magnetically Stabilized Fluidized Bed.

The juice clarification, one of the key steps in juice processing, suffers from haze formation that results from residual phenolic compounds. In this study, laccase was immobilized on metal-chelated magnetic silica nanoparticles and used for continuous juice clarification in a magnetically stabilized fluidized bed (MSFB) assisted by alternating magnetic field. Furthermore, a new combination of laccase catalysis and microfiltration was developed for the juice clarification. Immobilized laccase provided high relative activity within broader ranges of pH and temperature compared to the free enzyme. Magnetic immobilized laccase exhibited the best reaction rate of 12.1 μmol g–1 min–1 for catechol oxidation under the alternating magnetic field of 400 Hz, 60 Gs. No activity loss occurred in immobilized laccase after 20 h continuous operation of juice treatment in MSFB under an alternating magnetic field. Combined with microfiltration after treatment with immobilized laccase, the color of apple juice was decreased by 33.7%, and the light transmittance was enhanced by 20.2%. Furthermore, only 16.3% of phenolic compounds and 15.1% of antioxidant activity was reduced for apple juice after the clarification. By this combination strategy, the apple juice possessed good freeze–thaw and thermal stability.

Particulate matter filtration of the flue gas from iron-ore sintering operations using a magnetically stabilized fluidized bed

This study proposes a novel process for the separation of particulate matter (PM) from the flue gas emitted from iron-ore sintering operations using a magnetically stabilized fluidized bed (MSFB) with sintered ore as a filter medium. The deactivated sintered ore can still be used as a raw material for subsequent sintering operations. Sintered ore and sintered ash samples were characterized by x-ray diffraction, x-ray fluorescence, and laser diffraction analyses. The effects of collector size (150–300, 300–450, and 450–600 μm), applied magnetic flux density (48–160 Gs), bed height (5, 7.5, and 10 cm), and gas velocity ratio (1.40, 1.51, and 1.62) on PM filtration are investigated. The experimental results indicate that PM filtration efficiency increases with increasing magnetic field strength and bed height. However, a high gas velocity ratio has negative effects on PM removal performance, while collector size has little influence. A comparative study of the MSFB for magnetic sintered ash and non-magnetic coal-fired ash filtration demonstrates that sintered ash is more effectively captured due to magnetic retention. This indicates that this technology has good prospects for the purification of flue gas from iron-ore sintering operations.

Development of a bioreactor based on magnetically stabilized fluidized bed for bioartificial liver.

Bioartificial liver (BAL) based on microcapsules has been proposed as a potential treatment for acute liver failure. The bioreactors used in such BAL are usually expected to achieve sufficient flow rate and minimized void volume for effective application. Due to the superiorities in bed pressure drop and operation velocity, magnetically stabilized fluidized beds (MSFBs) show the potential to serve as ideal microcapsule-based bioreactors. In the present study, we attempted to develop a microcapsule-based MSFB bioreactor for bioartificial liver device. Compared to conventional-fluidized bed bioreactors, the bioreactor presented here increased perfusion velocity and decreased void volume significantly. Meanwhile, the mechanical stability as well as the immunoisolation property of magnetite microcapsules were well maintained during the fluidization. Besides, the magnetite microcapsules were found no toxicity to cell survival. Therefore, our study might provide a novel approach for the design of microcapsule-based bioartificial liver bioreactors.

High-efficiency removal of NO x by a novel integrated chemical absorption and two-stage bioreduction process using magnetically stabilized fluidized bed reactors

To enhance the bioregeneration of Fe(II)EDTA and to avoid the inhibition of the components in nitrogen oxides (NOx) scrubbing solution, a novel integrated process of metal chelate absorption and two-stage bioreduction was developed. In this process, magnetically stabilized fluidized beds (MSFB) were used as the bioreactors, and the phase diagram for the MSFB operation was determined. Factors including inlet NO, O2 and SO2 concentrations, magnetic field intensity, gas flow rate and liquid circulation rate, were studied experimentally to investigate their effects on NO removal. In addition, a mathematical model for NO removal in this integrated system was developed. The results revealed that the integrated system could be steadily operated with a high NO removal efficiency and elimination capacity, even under the condition of high NO and O2 shock-loading. The established model showed that NO removal efficiency was related to the spray column property and the active Fe(II)EDTA concentration, while the latter depends on the bioregeneration of the disabled absorbent in the MSFB.

Dechlorination of polychlorinated phenols on bimetallic Pd/Fe catalyst in a magnetically stabilized fluidized bed

Dechlorination of 2,4,6-trichlorophenol was performed within a magnetically stabilized fluidized bed (MSFB), containing a palladized iron (Pd/Fe) catalyst entrapped within alginate beads. Kinetic parameters of this multistep reaction yielding phenol as a final product were preliminarily defined in a batch system using four different intermediates as substrates for Pd/Fe catalyzed dechlorination. Further work using the fluidized bed reactor provided the basis for mathematical description of the full dechlorination process both with and without the assistance of an applied magnetic field. The resulting model includes convective mass transfer in the bulk media, diffusion within the alginate beads and reaction kinetics, including catalyst deactivation caused by passivation. Very good agreement was observed between experimental data and predictions of the model. These results confirmed the benefit of using MSFB reactors for more efficient dechlorination of toxic polychlorinated phenols, as compared to fluidized bed reactors without magnetic field stabilization.

Oxidative carbonylation of phenol to diphenyl carbonate by Pd/MFe2O4 magnetic catalyst

In order to screen one suitable catalyst for magnetically stabilized fluidized bed (MSFB) reactor in the process of oxidative carbonylation of phenol to diphenyl carbonate (DPC), Pd/MFe2O4 catalysts were chosen, then prepared and characterized by XRD, H2-TPR, XPS and VSM (Vibrating Sample Magnetometer). Compared to the other metal ion doped spinel ferrite catalysts, the catalytic activity of Pd/MnFe2O4 was much higher, which the single pass yield of DPC reached 33.12% with selectivity above 99%, and TOF (turnover frequency) reached 70.56molDPC?(molPd?h)-1.The result showed that the formation of the ferrite oxygen-deficient and ion transference in the ferrites was in favor of the catalytic activity. When the support MnFe2O4 was calcinated at 500?C, the saturation magnetization of the obtained catalyst Pd/MnFe2O4 came up to 43.1 A?m2?kg-1. With good magnetic property and brilliant catalytic activity the catalyst Pd/MnFe2O4 may suite for industrial experiments in MSFB reactor in future.

Oxidative carbonylation of phenol to diphenyl carbonate by Pd/MO–MnFe2O4 magnetic catalyst

In order to screen one suitable catalyst for magnetically stabilized fluidized bed (MSFB) reactor in the process of oxidative carbonylation of phenol to diphenyl carbonate (DPC), Pd/MnFe2O4 catalysts were chosen, then prepared and characterized by XRD, H2-TPR, O2-TPD and VSM. Compared to the other metal ion doped spinel ferrite catalysts, the catalytic activity of Pd/10% PbO–MnFe2O4 was much higher, which the single pass yield of DPC reached 33.12% with selectivity above 99%, and TOF (turnover frequency) reached 70.56molDPC·(molPdh)−1. The result showed that the formation of the ferrite oxygen-deficient and ion transference in the ferrites was in favor of the catalytic activity. When the support MnFe2O4 was calcinated at 500°C, the saturation magnetization of the obtained catalyst Pd/10% PbO–MnFe2O4 came up to 37.81Am2kg−1. With good magnetic property and brilliant catalytic activity the catalyst Pd/PbO–MnFe2O4 may suite for industrial experiments in MSFB reactor in future.

Functional Magnetic Mesoporous Nanoparticles for Efficient Purification of Laccase from Fermentation Broth in Magnetically Stabilized Fluidized Bed

A magnetically stabilized fluidized bed (MSFB) with the Cu(2+)-chelated magnetic mesoporous silica nanoparticles (MMSNPs-Cu(2+)) was established to purify laccase directly from the fermentation broth of Trametes versicolor. The MMSNPs-Cu(2+) particles in the MSFB maintained a stable bed expansion of two to threefold at a flow rate of 120-180 cm/h. At the optimal magnetic field intensity of 120 Gs, both the maximal Bodenstein number and the smallest axial dispersion coefficient were achieved, which resulted in a stable fluidization stage. The dynamic binding capacity of laccase in the MSFB decreased from 192.5 to144.3 mg/g when the flow velocity through the bed increased from 44.2 to 69.8 cm/h. The MSFB with MMSNPs-Cu(2+) achieved efficient laccase purification from the fermentation broth with 62.4-fold purification of laccase and 108.9 % activity yield. These results provided an excellent platform for the application of these magnetic mesoporous nanoparticles integrated with the MSFB in developing novel protein purification process.

Motion behavior of particles in air–solid magnetically stabilized fluidized beds for separation

In order to study the settling mechanism of particles in an air–solid magnetically stabilized fluidized bed (MSFB) for separation, we carried out free settling and quasi-zero settling tests on the tracing particles. The results show that the main resistance forces as the tracing particles settled in an air–solid MSFB were motion resistance force and yield force. The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles. The acceleration decreased from 3022.62cm/s2 to zero in 0.1s, and in the end, the particles stopped in the air–solid MSFB. The yield force on particles increased with increasing the magnetic field intensity, resulting in decrease of the quasi-zero settling displacement. However, the yield force on particles decreased with increasing the fluidized air velocity, leading to increase of the quasi-zero settling displacement. When the structure and operating parameters of the air–solid MSFB were set up, the yield stress on particles stopped in an air–solid MSFB was a function of diameter and density of particles. The settling displacements of equal diameter particles increased with increasing their densities, and the settling displacements of equal density particles increased with increasing their diameters.

Enhanced phenol degradation in coking wastewater by immobilized laccase on magnetic mesoporous silica nanoparticles in a magnetically stabilized fluidized bed

The immobilized laccase on magnetic mesoporous silica nanoparticles has been developed for efficient phenol degradation. The degradation rate of phenol by the immobilized laccase was 2-fold higher than that of the free laccase, and the immobilized laccase retained 71.3% of its initial degradation ability after 10 successive batch treatments of coking wastewater. The phenol degradation in the coking wastewater was enhanced in a continuous treatment process by the immobilized laccase in a magnetically stabilized fluidized bed (MSFB) because of good mixing and mass transfer. The degradation rate of phenol maintained more than 99% at a flow rate of less than 450mLh−1 and decreased slowly to 91.5% after 40h of the continuous operation in the MSFB. The present work indicated that the immobilized laccase on magnetic mesoporous supports together with the MSFB provided a promising avenue for the continuous enzymatic degradation of phenolic compounds in industrial wastewater.

Local heat transfer properties in co- and counter-current G–L–S magnetically stabilized fluidized beds

Heat transfer coefficients were measured by immersed probes in co- and counter-current G–L–S magnetically stabilized fluidized beds (MSFBs) using air, water and nickel-alloy particles as the gas, liquid and solid phases. Influences of major factors, including magnetic field intensity, superficial gas and liquid velocities, liquid viscosity and surface tension, on heat-transfer properties were studied experimentally, indicating that both co- and counter-current G–L–S MSFB can provide relatively uniform radial distribution of heat transfer coefficients under appropriate operation conditions, thus controlling operation temperature for highly exothermic multi-phase reaction systems. Two correlations were provided to estimate accurately heat transfer properties in both co- and counter-current G–L–S MSFB systems, with an average error of less than 10%.

Development of the magnetic beads for dye ligand affinity chromatography and application to magnetically stabilized fluidized bed system

Magnetic poly(2-hydroxyethylmethacrylate) [mPHEMA] beads were prepared by suspension polymerization of HEMA in the presence of Fe 3O 4 nano-powder. Cibacron Blue F3GA was covalently immobilized to the mPHEMA beads via nucleophilic substitution reaction between chloride of its triazine ring and hydroxyl groups of HEMA under alkaline conditions. The mPHEMA/Cibacron Blue F3GA beads (100–140 μm in diameter) carrying 68.3 μmol Cibacron Blue F3GA per gram polymer were used for β-casein adsorption studies. Adsorption studies were performed under different conditions in a batch system (i.e., pH, β-casein initial concentration, temperature, and ionic strength) and then in a magnetically stabilized fluidized bed (MSFB) system. The swelling ratio of the mPHEMA was 62.1%. The maximum adsorption capacity for batch system was 20.2% lower as compared to the value obtained in MSFB. The mPHEMA/Cibacron Blue F3GA beads could be repeatedly applied for β-casein adsorption without significant losses in the adsorption capacity.

Application of Magnetically Stabilized Fluidized Beds for Cell Suspension Filtration from Aqueous Solutions

A magnetically stabilized fluidized bed (MSFBs) utilizing a transverse magnetic field was used to retain cells from cell suspension. The magnetic field permits bed expansion without mixing of the magnetic particles. The bed porosity increased by 75% when the magnetic field intensity increases to 110 mT. The effect of the magnetic field, suspension flow rate, bed height, initial concentration, and pH on the breakthrough curves was studied. According to the experimental results, increasing the initial concentration, flow rate, and pH leads to early breakthrough and inefficient deposition. Additionally, increasing the field intensity and bed height delays the breakthrough point.

Intensified recovery of copper in solution: Cementation onto iron in fixed or fluidized bed under electromagnetic field

This work deals with the cementation of copper ions onto iron shots, within a fixed bed or fluidized bed, associated with an electromagnetic field. The influence of several parameters is studied: flowrate (5–45 L min −1 corresponding to a 1.4 × 10 −2 to 1.3 × 10 −1 m s −1 superficial velocity), temperature (20–40 °C), initial concentration of Cu(II) (50–10,000 ppm), pH (1.5–4.5), bed height (20–45 cm). Moreover, the influence of a movable and alternated electromagnetic field is also investigated. Cementation results and the hydrodynamic characterization of the reactor have been coupled through a process modeling in order to determine apparent mass transfer coefficients. These coefficients (ranging from 2.2 × 10 −5 to 2.3 × 10 −4 m s −1) are used as a comparison criterion to quantify the influence of each operating parameters. This work points out an enhancement of copper recovery when the electromagnetic field leads to a magnetically stabilized fluidized bed (MSFB).

Separation of yeast cells from aqueous solutions using magnetically stabilized fluidized beds

To separate Saccharomyces cerevisiae cells from aqueous solutions using magnetically stabilized fluidized beds (MSFB) that utilize a horizontal magnetic field, and to study the effect of some parameters, such as bed porosity and height, liquid flow rate and inlet concentration on cell removal efficiency and breakthrough curves. The separation process was conducted in an MSFB under the effect of horizontal magnetic field. The magnetic particles used consist of a ferromagnetic core of magnetite (Fe3O4) covered by a stable layer of activated carbon to adsorb the yeast cells from the suspension. The yeast cell concentration in the effluent was determined periodically by measuring the absorbance at 610 nm. The effect of the magnetic field intensity on the bed porosity and consequently the exit-normalized cell concentration from the bed was studied. It was found that bed porosity increased by 75%, and the normalized cell concentration in the bed effluent decreased by 30%, when the magnetic field intensity was increased from 0 to 110 mT. In addition, increasing the magnetic field intensity and bed height delayed the breakthrough point, and allowed efficient cell removal. These results demonstrate an improved method to separate cells of low concentration from cell suspension. This study allows the continuous separation of yeast cells from aqueous solutions in an MSFB. The removal efficiency is affected by different parameters including the bed height, flow rate and initial concentration. The removal efficiency reaches 82%, and could be improved by varying the operational parameters. The results obtained in this investigation show that the MSFB using horizontal fields represents a potential tool for the continuous separation of cell suspension from aqueous solution. This study will contribute to a better understanding of the hydrodynamic parameters on the separation efficiencies of the cell.

Synthesis of tentacle type magnetic beads as immobilized metal chelate affinity support for cytochrome c adsorption

Magnetic poly(2-hydroxyethylmethacrylate) (mPHEMA) beads with an average diameter of 100–140 μm were produced by suspension polymerization in the presence of magnetite particles (i.e. Fe 3O 4). Specific surface area and average pore size of the magnetic beads was found to be 50 m 2/g and 819 nm, respectively. Ester groups in the mPHEMA structure were converted to imine groups by reacting with poly(ethyleneimine) (PEI) in the presence of NaH. Amino (–NH 2) content of PEI-attached mPHEMA beads was determined as 102 mg PEI/g. Then, Cu 2+ ions were chelated on the magnetic beads in the range of 20–793 μmol Cu 2+/g. Cytochrome c (cyt c) adsorption was performed on the metal chelating beads from aqueous solutions containing different amounts of cyt c at different pHs, Cu 2+ loadings and temperatures. Cyt c adsorption on the mPHEMA/PEI beads was 4.6 mg/g. Cu 2+ chelation increased the cyt c adsorption significantly (40.1 mg/g). Adsorption capacity increased with Cu 2+ loading and then reached a saturation value. Cyt c adsorption decreased with increasing temperature. Cyt c molecules could be reversibly adsorbed and eluted ten times with the magnetic adsorbents without noticeable loss in their cyt c adsorption capacity. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. In the last part of this article, cyt c adsorption experiments were performed in a magnetically stabilized fluidized bed (MSFB) system at optimum conditions determined from the batch experiments. The adsorption capacity decreased significantly from 46.8 to 15.4 mg/g polymer with the increase of the flow-rate from 0.5 to 4.0 ml/min. The resulting magnetic chelator beads possessed excellent long-term storage stability.

Thiobacillus thioparus immobilized by magnetic porous beads: Preparation and characteristic

Novel Fe 3O 4/poly(styrene (St)–acrylic acid (AA)) magnetic porous beads (MPBs) were fabricated by a seed swelling process using magnetite particles as seeds. The porous beads were characterized with scanning electron microscopy (SEM). Magnetic properties of the MPBs were obtained by electron spin resonance (ESR) and vibrating-sample magnetometer (VSM). All the observations indicated that the beads were ferromagnetic. Thiobacillus thioparus was immobilized to the porous carrier at up to 9.3 × 10 9 cells/g MPBs. Compared with active carbon (AC) and agar as carriers, MPB as a carrier of immobilized Thiobacillus cells is the most efficient in removal of sulfide. Effects of the size of MPBs and surface carboxyl content on cell immobilization efficiency were investigated and the optimal pH and the temperature for the immobilized cells were determined. T. thioparus immobilized on MPB had a good storage stability. Continuous operation of a magnetically stabilized fluidized bed (MSFB) filled with MPB-immobilized T. thioparus at a flow rate of 160 ml/min resulted in the sulfide oxidizing rate of 8.64 kg S m −3 d −1.

Chlorophenol dehalogenation in a magnetically stabilized fluidized bed reactor

AbstractAromatic halocarbons are often present in contaminated aquifers, surface waters, wastewater streams, soils, and hazardous wastes. The dehalogenation of p‐chlorophenol as a model compound in both the aqueous phase and in slurries of contaminated solids using a magnetically stabilized fluidized bed (MSFB) reactor is discussed. Composite palladium‐iron (Pd/Fe) media are employed as both catalyst and sacrificial reactant for the reductive dechlorination of p‐chlorophenol. Calcium alginate beads impregnated with Pd/Fe granules are fluidized in a recirculating aqueous stream containing either dissolved p‐chlorophenol or a slurry of soil contaminated with this chlorocarbon. Magnetic stabilization of the fluidized bed allows substantially higher rates of mass transfer than would otherwise be achievable, and allows circulation of contaminated solids while fluidization media are retained. Anoxic conditions are sustained under a nitrogen purge and the solution pH of 5.8 is maintained by active control to minimize surface fouling by hydroxides, and to minimize mass‐transfer resistances resulting from the surface accumulation of hydrogen bubbles. A model of this process is described and the resulting predictions are compared to the experimentally derived data. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Small-sized dense magnetic pellicular support for magnetically stabilized fluidized bed adsorption of protein

A small-sized dense magnetic pellicular support (MPS) for magnetically stabilized fluidized bed (MSFB) adsorption of protein has been fabricated by introducing magnetic colloids and glass beads during the emulsification of 4% agarose solution. The MPS was identified with a mean density of 1.40 g/ml and a size range of 70– 130 μ m . The support has a good magnetization property with little residual magnetization after the field was removed. After cross-linking and reducing, the MPS was coupled with diethylaminoethyl (DEAE) groups to create an anion exchanger DEAE–MPS. The fluidization behavior of the support was examined in an MSFB with transverse magnetic field and the results were compared with those obtained in expanded bed. As a result, an optimum field intensity of 250 Gs was found to give the lowest axial dispersion of the MSFB. At the optimum field intensity, BSA adsorption at 208 and 283 cm/h showed that the dynamic binding capacity in MSFB was about 60% higher than that in expanded bed mode. It was attributed to the reduced backmixing in the MSFB compared to that in expanded bed. The results indicate that the dense MPS is promising for MSFB protein adsorption at elevated flow rates.