Flask Reactor Research Articles

Selection of Leptospirillum ferrooxidans SRPCBL and development for enhanced ferric regeneration in stirred tank and airlift column reactor

Presence of Leptospirillum ferrooxidans plays significant role in ferric sulphate generation during bioleaching process. Thus, an attempt was made to select L. ferrooxidans from the polymetallic concentrate leachate and further developed it for enhanced ferric iron regeneration from the leachate in shake flask, stirred tank and column reactor. When ferric to ferrous iron ratio in the shake flask reached to 20:1, L. ferrooxidans out competed Acidithiobacillus ferrooxidans and accounted for more than 99% of the total population. The isolate was confirmed by 16S rRNA genes sequence analysis and named as L. ferrooxidans SRPCBL. When the culture was exposure to UV dose and the oxidation–reduction potential of the inoculation medium was adjusted to 400mV by ferrous:ferric iron ratio, the IOR reached to as high as 1.2g/L/h in shake flask, even with initial ferrous iron concentration of 200g/L. The chalcopyrite concentrate leachate containing 12.8, 15.7, and 42.0g/L ferrous iron, ferric iron and copper, respectively was studied for ferric iron regeneration with the developed polymetallic resistant L. ferrooxidans SRPCBL in stirred tank and a developed biofilm airlift column, the highest IOR achieved were 2.20g/L/h and 3.1g/L/h, respectively, with ferrous oxidation efficiency of 98%. The ferric regeneration ability of the developed isolate from the leachate proves useful for a two-stage metal extraction process.

Synthesis and cure kinetics of liquefied wood/phenol/formaldehyde resins

AbstractWood liquefaction was conducted at a 2/1 phenol/wood ratio in two different reactors: (1) an atmospheric three‐necked flask reactor and (2) a sealed Parr reactor. The liquefied wood mixture (liquefied wood, unreacted phenol, and wood residue) was further condensed with formaldehyde under acidic conditions to synthesize two novolac‐type liquefied wood/phenol/formaldehyde (LWPF) resins: LWPF1 (the atmospheric reactor) and LWPF2 (the sealed reactor). The LWPF1 resin had a higher solid content and higher molecular weight than the LWPF2 resin. The cure kinetic mechanisms of the LWPF resins were investigated with dynamic and isothermal differential scanning calorimetry (DSC). The isothermal DSC data indicated that the cure reactions of both resins followed an autocatalytic mechanism. The activation energies of the liquefied wood resins were close to that of a reported lignin–phenol–formaldehyde resin but were higher than that of a typical phenol formaldehyde resin. The two liquefied wood resins followed similar cure kinetics; however, the LWPF1 resin had a higher activation energy for rate constant k1 and a lower activation energy for rate constant k2 than LWPF2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Modelling of biological phenol removal in draw-fill reactors using suspended and attached growth olive pulp bacteria

The kinetics of phenol biodegradation in draw-fill suspended and attached growth reactors by olive pulp bacteria were investigated. The Haldane equation was adopted in order to describe phenol biodegradation in the draw-fill suspended-growth flask reactors. Kinetic constants of the Haldane equation obtained from batch culture experiments with phenol concentration ranging from 13 to 280 mg l −1, were μ max=0.054 h −1, K S=19.23 mg l −1, and K i=36.95 mg l −1. However, in the draw-fill experiments at the packed-bed reactor, phenol inhibitory effects were minimized increasing the inhibitory constant value K i′ at 1571 mg l −1. The model predicted phenol biodegradation in the packed-bed reactor adequately, for all initial phenol concentrations tested, apart from the highest phenol concentration of 1990 mg l −1, where clogging problems and insufficient aeration in the filter prevailed.

Aerobic biological treatment of olive mill wastewater by olive pulp bacteria

The capability of olive fruit bacteria to remove chemical oxygen demand (COD) and phenolic compounds from olive mill wastewater (OMW) using flasks and packed bed reactors was tested. Batch aerobic experiments were performed in flask reactors, with OMW at different dilutions (20%, 50%, and 100%). The maximum phenolic and dissolved COD removal reached up to 82–90% for the dilutions of 20%, 50%, and 100%, in 11, 23, and 30 days, respectively. Experiments were also conducted in a bench and a pilot-scale packed bed reactor, operated in the laboratory and at an olive mill, respectively. At 28 °C the maximum phenolic and dissolved COD removal, recorded at the bench-scale reactor, reached about 60% and 70%, respectively, for a time period of only 27 h. At the pilot-scale reactor, where the maximum daily temperature varied between 6 and 20 °C, the maximum phenolic and d-COD removal reached about 55% and 70% in 5 and 3 days, respectively. These results indicate an economically feasible method for OMW biodegradation.

Evaluation of chondrogenesis within PEGT: PBT scaffolds with high PEG content

Porous poly(ethylene glycol) terephthalate:poly (butylene terephthalate) (PEGT:PBT) scaffolds with high PEG molecular weight (1000 g/mole) and PEGT content (60%) were fabricated using two different processes-paraffin templating and compression molding-for cartilage engineering applications. This polymer composition has previously been shown to enable chondrocyte adhesion and maintain differentiated phenotype in 2D monolayer culture. The influence of 3D polymer scaffold processing on the formation of cartilaginous tissue was studied by seeding primary immature bovine chondrocytes within cylindrical scaffolds in mixed flask reactors for 3 days, followed by cultivation in culture plates for a total of 10 or 24 days. Tissue-polymer constructs were evaluated morphologically by SEM and histology, and quantitatively for cellularity, total collagen, and glycosaminoglycan content, all of which remained statistically equivalent for each time point tested, irrespective of fabrication method. These data demonstrate that the polymers engineered for this study were able to support chondrogenesis independent of scaffold fabrication process, with the influence of pore architecture lessened by the highly hydrated scaffold microenvironments induced by high PEG content.

Biological phenol removal using suspended growth and packed bed reactors

Phenol removal was studied using batch cultures of free suspended cells and attached growth processes. Indigenous bacteria from olive pulp were enriched and used as inoculum for the filter and a suspended-growth flask reactor. A pilot-scale packed bed reactor was constructed and operated for biological phenol removal from industrial wastewater. The packed bed reactor was found to be more resistant to high phenol concentrations and led to significantly higher removal rates than the suspended-growth reactor. Two different operating modes were used to investigate the optimal performance of the filter, i.e., continuous and draw-fill. The latter was found to achieve removal rates up to 12.65 g phenol/(l d), while the continuous operating mode achieved removal rates only up to 0.082 g phenol/(l d).The low operating cost combined with the high phenol removal rates indicates that the above technology may offer a feasible solution to a serious environmental problem.

A kinetic study on enzymatic hydrolysis of a variety of pulps for its enhancement with continuous ultrasonic irradiation

The enzymatic hydrolyses of various pulps as a type of cellulosic materials were examined in a stirred flask reactor to establish a simplified kinetic model for the complicated process. To enhance the saccharification of a pulp with cellulase, the reaction was also carried out in a stirred tank reactor with continuous ultrasonic irradiation. The kinetic model was proposed by regarding the reaction system as a pseudo-homogeneous one, in which sugars would be produced from a hypothetical soluble substrate whose initial concentration would correspond to the concentration of total sugar produced ultimately. The validity of the model developed was confirmed by its successful simulation of the time courses of the total sugar and glucose during the saccharification either with or without ultrasonic irradiation. It was found that the variation in property of pulp as well as the intensity of ultrasonic irradiation exerted an effect on the apparent rate constant and ultimate conversion of substrate, but no effect on the apparent Michaelis and competitive product inhibition constants. The saccharification of the pulp called NUKP under the ultrasonic irradiation proceeded as a two-stage reaction, suggesting an almost complete conversion of the pulp to sugar. A mechanism was proposed for such an enhancement effect of the ultrasonic irradiation on enzymatic hydrolysis of cellulose.

Improvement of Panax notoginseng cell culture for production of ginseng saponin and polysaccharide by high density cultivation in pneumatically agitated bioreactors.

A Panax notoginseng cell culture was successfully scaled up from shake flask to 1.0-L bubble column reactor and concentric-tube airlift reactor. High-density bioreactor batch cultivation was carried out using a modified MS medium. The maximum cell density in batch cultures reached 20.1, 21.0 and 24.1 g/L in the shake flask, bubble column and airlift reactors, respectively, and their corresponding biomass productivity was 950, 1140 and 1350 mg/(L x d) for each. The productivity of ginseng saponin was 70, 96 and 99 mg/(L x d) in the flask, bubble column and airlift reactors, respectively; and the polysaccharide productivity reached 104, 119 and 151 mg/(L x d) for each. Furthermore, a fed-batch cultivation strategy was developed on the basis of specific oxygen uptake rate (SOUR), i.e., sucrose feeding before a sharp decrease of SOUR, and the highest cell density of 29.7 g/L was successfully achieved in the airlift bioreactor on day 17 with a very high biomass productivity of 1520 mg/(L x d). The concentrations of ginseng saponin and polysaccharide reached about 2.1 and 3.0 g/L, respectively, and their productivity was 106 (saponin) and 158 mg/(L x d) (polysaccharide). This work successfully demonstrated the high-density bioreactor cultivation of P. notoginseng cells in pneumatically agitated bioreactors and the reproduction of the shake flask culture results in bioreactors. The cell density, biomass productivity, production titer and productivity of both ginseng saponin and polysaccharide obtained here were the highest that have been reported on a reactor scale for all the ginseng species.

Role of the reactor configuration in the biological detoxification of a dump site-polychlorobiphenyl-contaminated soil in lab-scale slurry phase conditions.

The biotreatability of a xenobiotic contaminated soil is frequently determined through a bioslurry treatment usually performed in lab-scale shaken baffled flasks. In this study, a 3-1 unconventional stirred tank reactor was developed and tested in the slurry-phase treatment of a soil heavily contaminated by polychlorobiphenyls (PCBs) derived from an Italian dump site, in the absence and in the presence of biphenyl and of the exogenous PCB aerobically dechlorinating co-culture ECO3. The data obtained were compared with those obtained on the same soil in experiments performed in parallel in 3-1 baffled shaken flask reactors. Considerably higher PCB removal and soil detoxification yields (determined through the Lepidium sativum germination test and the Collembola mortality test) were attained in the stirred tank reactors, which generally displayed a higher slurry-phase homogeneity and a higher availability of biphenyl- and chlorobenzoic acid-degrading bacteria compared to the corresponding shaken flask reactors. Moreover, enhanced soil PCB biodegradation and detoxification yields were observed when the developed reactor was supplemented with biphenyl and the exogenous ECO3 bacteria. In conclusion, the results of the soil biotreatability experiments commonly performed in bioslurry lab-scale reactors are significantly influenced by the reactor configuration; the use of the unconventional stirred tank reactor system developed in this work is recommended.

Modeling of Tetrachloroethylene Degradation by Anaerobic Granular Biological Activated Carbon.

A number of different methods have been used for modeling the adsorption and biotransformation of volatile organic chlorinated compounds such as tetrachloroethylene perchloroethylene (PCE). In this study, PCE was degraded by granular biological activated carbon (GBAC) in an anaerobic Erlenmeyer flask reactor. In order to study GBAC, we performed experiments in which the efficiencies of GBAC, granular activated carbon (GAC) and anaerobic sludge for the removal of PCE were compared. In this paper, we describe how PCE was microbially biotransformed and adsorbed on GBAC. The biotransformational products were trichloroethylene (TCE) and cis-1, 2-dichloroethylene (cis-1, 2-DCE), which were adsorbed by GBAC (at solid phase). Thus, the GBAC acted not only as a microbiological carrier, but was also instrumental in adsorbing PCE and the biotransformation products. Since the adsorbed PCE was biotransformed on the GBAC, we concluded that GBAC might be effective in the treatment of PCE in synthetic wastewater. The model confirmed that the GBAC was involved in the degradation of PCE under our conditions. The model confirmed that the GBAC was instrumental in treating PCE.

Devolatilization with Chemical Reaction in Polymer Solutions

Abstract It has been observed previously [1] that under the specific conditions prevailing in a reflux flask reactor, the overall rate of the transesterification reaction between an ethylene and vinyl acetate copolymer and 3-phenyl 1-propanol can be enhanced appreciably by the introduction of boiling inert hydrocarbon solvents. In the present study, the same reaction carried out under a controlled removal of vapors in a simulator emulating a non-intermeshing counter-rotating devolatilization twin screw extruder, a significant acceleration of the reaction rate has also been observed. In agreement with the previous work [1], the intrinsic reaction mechanism and the chemical equilibrium do not appear to be affected by boiling of the inert hydrocarbon solvents, nor does the additional mechanical agitation due to the rapid bubble growth contribute to the increase of the overall reaction rate. Theoretical analysis of the results confirms that the acceleration of the reaction rate originates from the localized mass transfer effect connected to the presence of the bubble vapor-liquid interface films induced by devolatilization.

Oxidation of SO2 in thin water films containing NH3

Abstract The reaction between NH 3 and SO 2 in thin water films was studied with a focus on the formation of sulfate. The reactions were conducted at 5 and 60% relative humidities or partial pressure of water vapor and at 0.04, 0.16 or 0.20 atm O 2 for temperatures between 20 and 50°C using a flow reactor and static flask reactors. In the presence of water vapor, the oxidation of SO 2 to sulfate was observed only when NH 3 was present. The product was primarily (NH 4 ) 2 SO 4 . Conversion of as much as 81% of the SO 2 to sulfate was observed after 10 min of reaction when the initial concentrations of SO 2 and NH 3 were 1 ppm and the relative humidity was 60%. Conversion was only 1–3% when NH 3 and/or water vapor were absent from the system. The surface of the reactor was found to influence the reaction by providing a place for a film of liquid water to form, and for the first several hours of reaction in the film, th e rate of sulfate formation was observed to be faster than oxidation in liquid water. In general, these results suggest that thin water films on environmental surfaces play a greater role in the deposition of atmospheric gases and the accumulation of their reaction products on surfaces than previously considered.

Parameters for the Operation of Bacterial Thiosalt Oxidation Ponds

Shake flask and pH-controlled reactor tests were used to determine the mathematical parameters for a mixed-culture bacterial thiosalt treatment pond. Values determined were as follows: K(m) and V(max) (thiosulfate), 9.83 g/liter and 243.9 mg/liter per h, respectively; K(i) (lead), 3.17 mg/liter; K(i) (copper), 1.27 mg/liter; Q(10) between 10 and 30 degrees C, 1.95. From these parameters, the required bioxidation pond volume and residence time could be calculated. Soluble zinc (0.2 g/liter) and particulate mill products and by-products (0.25 g/liter) were not inhibitory. Correlation with an operating thiosalt biooxidation pond showed the parameters used to be valid for thiosalt concentrations up to at least 2 g/liter, lead concentrations of at least 10 mg/liter, and temperatures of >2 degrees C.

Evaluation of mass transfer rate during Ziegler‐Natta propylene polymerization

AbstractMass transfer which affects the rate of propylene polymerization with titanium trichloride–triethylaluminum, has been evaluated by use of a new method developed for this heterogeneous reaction. The polymerization was carried out with the usual flask reactor equipped with a paddle stirrer; the rate of gas absorption into the polymerization slurry was proportional to stirring speed and the reciprocal of the total amount of polymers produced. It has been confirmed that the polymerization rate separated from the absorption rate is purely kinetic (propagation), and an effective physical process, such as monomer transfer through a polymer film covering the catalyst surface, no longer exists.