A promising bacterial strain for the biodegradation of Microcystins (MCs) was isolated from Dianchi lake in China and identified as Sphingopyxis sp. USTB-05 by the analysis of 16s rDNA. Initial MC-RR of 42.3 mg·L−1 was completely degraded by USTB-05 within 36 h, which was a relatively high biodegradation rate of MC-RR. With the cell-free extract (CE) of Sphingopyxis sp. USTB-05, MC-RR was biodegraded at a more rapid biodegradation rate compared with its strain, so that initial MC-RR of 42.3 mg·L−1 was completely biodegraded within 10 h. During the bio-reaction of MC-RR catalyzed by CE, two intermediate metabolites and a dead-end product of MC-RR were observed on HPLC profiles and all of them had similar scanning profiles in the wavelength from 200 to 300 nm, indicating that the group of Adda in all products of MC-RR remained intact.
Candida albicans PDY-07 was isolated from activated sludge under anaerobic conditions and identified as a member belonging to the genus Candida. Pure culture of C. albicans PDY-07, biodegradation of 4-chlorophenol (4-CP) was carried out under anaerobic conditions in Erlenmeyer flasks at 35°C, with an initial pH of 7.0–7.2 and a starting inoculum of 10% (by volume). The results showed that, under the above-mentioned conditions, C. albicans PDY-07 could thoroughly biodegrade 4-CP up to a concentration of 300mg·L−1 within 244h and that it had a high tolerance potential of up to 440mg·L−1 for 4-CP. With the increase in the initial concentrations of 4-CP, substrate inhibition was obviously enhanced. There was increased consumption of 4-CP, which was not assimilated by the cell for growth but was used to counteract the strong substrate inhibition. In addition, the cell growth and substrate-degradation kinetics of 4-CP as the sole source of carbon and energy for the strain in batch cultures were also investigated over a wide range of substrate concentrations (2.2–350mg·L−1), using the proposed cell growth and degradation kinetic models. The results recorded from these experiments showed that the proposed kinetic models adequately described the dynamic behavior of 4-CP biodegradation by C. albicans PDY-07.
The interaction of DNA with cationic gemini surfactant trimethylene-1,3-bis (dodecyl dimethyl-ammonium bromide) (12-3-12) and anionic surfactant sodium dodecyl sulfate (SDS) mixed system has been investigated by measuring the fluorescence, zeta potential, UV-Vis spectrum, and circular dichroism. In the absence of SDS, owing to the electrostatic and hydrophobic interactions, 12-3-12 forms micelle-like structure on the DNA chain before the micellization in bulk phase. For the mixed system of 12-3-12 and SDS, the negative charges on SDS can compete against DNA to bind with cationic 12-3-12 because of the stronger interaction between oppositely charged surfactants, and thus, the catanionic mixed micelles are formed before the formation of DNA/12-3-12 complexes. Thereafter, the positive charges on the mixed micelles bind with DNA, and thus, the change of the zeta potential from negative to positive is distinctly different from the system without SDS. Meanwhile, the existence of SDS postpones the exclusion of ethidium bromide (EB) from DNA/EB complexes. The conformation of DNA undergoes a change from native B-form to chiral ψ-phase as binding with 12-3-12 process. Upon adding SDS to the DNA/12-3-12 complex solution, however, DNA is released to the bulk and the ψ-phase returns to B-form again.
The shear-induced migration of neutrally-buoyant non-colloidal circular particles in a two-dimensional circular Couette flow is investigated numerically with a distributed Lagrange multiplier based fictitious domain method. The effects of inertia and volume fraction on the particle migration are examined. The results indicate that inertia has a negative effect on the particle migration. In consistence with the experimental observations, the rapid migration of particles near the inner cylinder at the early stage is observed in the simulation, which is believed to be related to the chain-like clustering of particles. The migration of circular particles in a plane Poiseuille flow is also examined in order to further confirm the effect of such clustering on the particle migration at early stage. There is tendency for the particles in the vicinity of outer cylinder in the Couette device to pack into concentric rings at late stage in case of high particle concentration.
A Lactobacillus brevis CGMCC 1306 isolated from fresh milk without pasteurization was found to have higher glutamate decarboxylase (GAD) activity. An effective isolation and purification procedure of GAD from a cell-free extract of Lactobacillus brevis was developed, and the procedure included four steps: 30%—90% saturation (NH4)2SO4 fractional precipitation, Q sepharose FF anion-exchange chromatography, sephacryl S-200 gel filtration, and resource Q anion-exchange chromatography. Using this protocol, the purified GAD was demonstrated to possess electrophoretic homogeneity via SDS-PAGE. The purification fold and activity recovery of GAD were 43.78 and 16.95%, respectively. The molecular weight of the purified GAD was estimated to be approximately 62 kDa via SDS-PAGE. The optimum pH and temperature of the purified GAD were 4.4 and 37°C, respectively. The purified GAD had a half-life of 50min at 45°C and the Km value of the enzyme from Lineweaver-Burk plot was found to be 8.22. 5′-pyridoxal phosphate (PLP) had little effect on the regulation of its activity.
A series of polyhydroxyalkanoate (PHA) copolymers consisting of short-chain-length (SCL) and medium-chain-length (MCL) 3-hydroxyalkanoate (3HA) monomers were synthesized in the recombinant Ralstonia eutropha PHB−4 harboring a low-substrate-specificity PHA synthase PhaC2Ps from Pseudomonas stutzeri 1317. These polyesters, whose monomer compositions varied widely in chain length, were purified and characterized by acetone fractionation, nuclear magnetic resonance (NMR), gel-permeation chromatography (GPC), and differential scanning calorimetry (DSC). This was the first time that the physical properties of PHA copolymers polymerized by PhaC2Ps were characterized. The results indicated that the variation in MCL 3HA contents did not have an obvious influence on the molecular weights of these PHA copolymers but was effective in changing their physical properties. The variation in the thermal property of PHA copolymers with 3-hydroxyoctanoate (3HO) content was also investigated in this study.
AbstractThe production of 2,3-butanediol by Klebsiella pneumoniae from glucose supplemented with different salts was studied. A suitable medium composition was defined by response surface experiments. In a medium containing glucose and (NH4)2HPO4, the strain could convert 137.0g of glucose into 52.4g of 2,3-butanediol and 8.4g of acetoin in shaking flasks. The diol yield amounted to 90% of its theoretical value and the productivity was 1—1.5g·L−1.h−1. In fed-batch fermentation, the yield and productivity of diol were further enhanced by maintaining the pH at 6.0. Up to 92.4g of 2,3-butanediol and 13.1g of acetoin per liter were obtained from 215.0g of glucose per liter. The diol yield reached 98% of its theoretical value and the productivity was up to 2.1g·L−1·h−1.
An empirical model for COD removal in a biological aerated filter (BAF) in the presence of 2,4,6-trinitrophenol (TNP) was developed, which related effluent COD to influent COD or hydraulic loading rate along the bed height. The overall reaction rate for substrate biodegradation could be described as pseudo first order. The experimental data of COD removal against reactor height were used to calculate the parameters in the empirical model. The COD concentration at different reactor height was expressed as a function of influent COD concentration and hydraulic loading rate, ln(C0/C) = 0.124H/Q0.770 and ln(C/0) = −5.63H/L0.94}, respectively, under the experimental condition. The models may be used to predict the COD removal profiles along the reactor height at different hydraulic loading rates and influent COD concentration for design, selection and sizing of BAF.
Baker's yeast number 6 was selected by screening. It showed good catalytic activity and enantioselectivity for asymmetric reduction of 2,5-hexanedione to produce (2S,5S)-2,5-hexanediol. Gas chromatography-mass spectrometry (GC-MS) revealed that the intermediate was (S)-5-hydroxyhexane-2-one. Reduction of 2,5-hexanedione proceeded in a two-step reaction. The hydroxyketone was initially formed, and this intermediate was further reduced to the diol. Factors influencing the product yield and the enantiomeric excess of the reduction of 2,5-hexandione catalyzed by baker's yeast number 6 were investigated. Higher concentration (≤100 mmol·L−1) of 2,5-hexandione did not influence 5-hydroxyhexane-2-one production, but 2,5-hexanediol production was inhibited by excess accumulation (>30 mmol·L−1) of intermediate. The optimal conditions were glucose as the co-substrate at an initial glucose concentration of 20 g·L−1, 34°C, pH 7.0 and cell concentration 60 g·L−1 (cell dry mass). Under the optimal condition and an initial substrate concentration of 30 mmol·L−1, the yield of 2,5-hexandiol was 78.7% and the enantiomeric excess of (2S,5S)-2,5-hexandiol was 94.4% for 24-h reduction.
Elementary flux mode (EFM) analysis was used in the metabolic analysis of central carbon metabolism in Saccharomyces cerevisiae based on constructed cellular network. Calculated from the metabolic model, the ethanol-producing pathway No. 37 furthest converts the substrate into ethanol among the 78 elementary flux modes. The in silico metabolic phenotypes predicted based on this analysis fit well with the fermentation performance of the engineered strains, KAM3 and KAM11, which confirmed that EFM analysis is valid to direct the construction of Saccharomyces cerevisiae engineered strains, to increase the ethanol yield.
Ultrasonically assisted extraction of isoflavones from the stem of Pueraria lobata (Willd.) Ohwi has been carried out with an ultrasonic extracting apparatus (20kHz, electrical power input to the transducer in 0—650W). The influence of the electrical power input and extraction time on the extraction yield is investigated in water, n-butanol, and 95% (by volume) and 50% (by volume) ethanol aqueous solution. The experimental results indicate that the yields of total isoflavones are higher in Ultrasonically assisted extraction than those obtained from conventional extraction. Moreover, a mathematical model is proposed, by introducing the electrical power input to index the ultrasound intensity, to describe the behavior of ultrasonically assisted extraction. It is found that the model calculations are in good agreement with the experimental data.
Corrosion and electrochemical behavior of 316L stainless steel was investigated in the presence of aerobic iron-oxidizing bacteria (IOB) and anaerobic sulfate-reducing bacteria (SRB) isolated from cooling water systems in an oil refinery using electrochemical measurement, scanning electron microscopy (SEM) and energy dispersive atom X-ray analysis(EDAX). The results show the corrosion potential and pitting potential of 316L stainless steel decrease distinctly in the presence of bacteria, in comparison with those observed in sterile medium under the same exposure time. SEM morphologies have shown that 316L stainless steel reveals no signs of pitting attack in the sterile medium. However, micrometer-scale corrosion pits were observed on 316L stainless steel surface in the presence of bacteria. The presence of SRB leads to higher corrosion rates than IOB. The interactions between the stainless steel surface, abiotic corrosion products, and bacterial cells and their metabolic products increased the corrosion damage degree of the passive film and accelerated pitting propagation.
Cationic ring opening polymerization of octamethylcyclotetrasiloxane (D4) initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments. Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance (1H-NMR) and gel permeation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarily narrow compared with that of cationic polymerizations reported elsewhere (>1.9). The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mechanism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated.
An efficient and environmentally friendly procedure was described for easy product isolation for the oxidation of cyclohexane with tert-butyl-hydroperoxide catalyzed by titanium silicalite 1 (TS-1) in ambient-temperature ionic liquid [emim]BF4. Good yield and higher selectivity of products were found in the ionic liquid compared with in molecular solvent. The research results showed 13.2% conversion of cyclohexane, 97.6% cyclohexanol and cyclohexanone selectivity were obtained in ionic liquid under mild conditions of 90°C.
Viscosities and densities for 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and N, N-dimethylformamide (DMF) binary mixtures have been measured at the temperature range from 293.15 K to 318.15 K. It is shown that the viscosities and densities decrease monotonously with temperature and the content of DMF. Various correlation methods including Arrhenius-like equation, Seddon et al.'s equation, Redlich-Kister equation with four parameters, and other empirical equations were applied to evaluate these experimental data. A model based on an equation of state for estimating the viscosity of mixtures containing ionic liquids were proposed by coupling with the excess Gibbs free energy model of viscosity, which can synchronously calculate the viscosity and the molar volume. The results show that the model gives a deviation of 8.29% for the viscosity, and a deviation of 1.05% for the molar volume when only one temperature-independent adjustable parameter is adopted. The correlation accuracy is further improved when two parameters or one temperature-dependent parameter is used.
The enrichment of chloride anion within the occluded cell (OC) for Type 304 austenitic stainless steel in low chloride concentration solution has been investigated by means of a simulated OC. The influence of the enrichment of chloride anion on stress corrosion crack (SCC) of Type 304 stainless steel has been studied. It was observed that the amount of chloride anion migration was proportional to the charge flowing through the anode. Owning to the effects of enrichment of chloride anion, low chloride concentration solution could induce SCC for Type 304 stainless steel.
Density (ρ) and viscosity (η) measurements were carried out for 4-aminobutyric acid in 0.0041, 0.0125 and 0.0207 mol·L−1 aqueous salbutamol sulphate at 308.15, 313.15 and 318.15 K. The measured values of density and viscosity were used to estimate some important parameters such as apparent molar volume Vϕ, limiting apparent molar volume
, transfer volume
, hydration number nH, second derivative of infinite dilution of partial molar volume with temperature
, viscosity B-coefficients, variation of B with temperature dB/dT, free energy of activation per mole of solvent
, activation entropy
and activation enthalpy
of the amino acids. These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.
SAPO-34 zeolite is considered to be an effective catalyst for methanol or dimethyl ether conversion to olefins. In this study, we developed the in situ synthesis technology to prepare SAPO-34 zeolite in kaolin microspheres as a catalyst for fluidized methanol or dimethyl ether to olefins process. The silicoaluminophosphate zeolite was first time reported to be synthesized in kaolin microspheres. The SAPO-34 content of synthesized catalyst was about 22% as measured by three different quantitative methods (micropore area, X-ray fluorescence and energy dispersive spectroscopy element analysis). Most of the SAPO-34 zeolites were in nanoscale size and distributed uniformly inside the spheres. The catalytic performance was evaluated in fixed bed and fluidized bed reactors. Compared with the conventional spray-dry catalyst, SAPO/kaolin catalyst showed superior catalytic activities, better olefin selectivities (up to 94%, exclusive coke), and very good hydrothermal stability. The in situ synthesis of SAPO-34 in kaolin microspheres is a facile and economically feasible way to prepare more effective catalyst for fluidized MTO/DTO (methanol to olefins/dimethyl ether to olefins) process.
To achieve higher antibiotic streptolydigin productivity through metabolic regulation, propionate was fed during the fermentation of Streptomyces lydicus AS 4.2501. The effects of propionate feeding on streptolydigin production and intracellular fluxes were investigated. The highest streptolydigin production yield of 95.10mg·L-1 was obtained when 2mmol·L-1 of sodium propionate was added at 60h of cultivation into shake-flask culture. This yield is 23.06% higher when compared to that of a batch culture without propionate supplementation. It was also found that when propionate was added, much more organic acids were excreted. Metabolic flux analysis was performed and it demonstrated that the carbon fluxes of the pentose phosphate pathway and the anaplerotic reaction were significantly increased after propionate feeding. The carbon flux from pyruvate to acetyl-CoA was determined to be 24.7, which was 12.27% higher than that in the batch culture. This study indicated that the glucose-6-phosphate and pyruvate nodes were potential bottlenecks for increasing streptolydigin productivity. Potential targets and strategies that could be manipulated through genetic and process engineering to increase the production of streptolydigin were also suggested.
A new 18-lump kinetic model for naphtha catalytic reforming reactions is discussed. By developing this model as a user module, a whole industrial continuous catalytic reforming process is simulated on Aspen plus platform. The technique utilizes the strong databases, complete sets of modules, and flexible simulation tools of the Aspen plus system and retains the characteristics of the proposed kinetic model. The calculated results are in fair agreement with the actual operating data. Based on the model of the whole reforming process, the process is optimized and the optimization results are tested in the actual industrial unit for about two months. The test shows that the process profit increases about 1000yuan·h−1 averagely, which is close to the calculated result.
This research deals with an investigation of the adsorption of two acids, namely, 5-amino-2-chlorotoluene-4-sulfonic and chlorhydric acids from their solution onto weakly basic resin. The screening of resins, kinetics, and isotherm were studied. The results indicate that the D301R is more appropriate for the removal of acids from solution. The adsorption of acids obeys Langmuir isotherm and the first-order kinetics model. Sorptive affinity of the two acids on D301R was found to be in the order of 5-amino-2-chlorotoluene-4-sulfonic acid> chlorhydric acid. Thermodynamic parameters for the adsorption of acids were calculated and discussed. The maximum removal of acids was observed around 97% and 76% at 25°C for 5-amino-2-chlorotoluene-4-sulfonic acid and chlorhydric acid, respectively.
The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor (SBR) treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed (UASB). Nitrite accumulates obviously at different initial nitrate concentrations (64.9,54.8,49.3 and 29.5 mg·L−1) and low temperatures, and the two break points on the oxidation-reduction potential (ORP) profile indicate the completion of nitrate and nitrite reduction. Usually, the nitrate reduction rate is used as the sole parameter to characterize the denitrification rate, and nitrite is not even measured. For accuracy, the total oxidized nitrogen (nitrate + nitrite) is used as a measure, though details characterizing the process may be overlooked. Additionally, batch tests are conducted to investigate the effects of C/N ratios and types of carbon sources on the nitrite accumulation during the denitrification. It is observed that carbon source is sufficient for the reduction of nitrate to nitrite, but for further reduction of nitrite to nitrogen gas, is deficient when C/N is below the theoretical critical level of 3.75 based on the stoichiometry of denitrification. Five carbon sources used in this work, except for glucose, may cause the nitrite accumulation. From experimental results and cited literature, it is concluded that Alcaligene species may be contained in the SBR activated-sludge system.
In this paper, shorter residence time (a few minutes) with high yield in the trickle bed process for peracetic acid synthesis by acetaldehyde liquid phase oxidation can be realized on the selected packing material SA-5118. For acetaldehyde in acetone with ferric ion as catalyst, the optimized process conditions were presented. The main factors influencing the yield, selectivity and conversion are residence time, temperature and acetaldehyde concentration, respectively. The temperature range checked is from 30 to 65°C. High yield of 81.53% with high selectivity of 91.84% can be obtained at higher temperature of 55°C when the residence time is 5.5min and the acetaldehyde concentration is 9.85% (by mass). And there is a critical acetaldehyde concentration point (Cccp) between 18% and 19.5% (by mass). At temperature less than 55°C, the highest yield to peracetic acid at each temperature level increases with temperature when the acetaldehyde concentration is below Cccp and decreases with temperature when the acetaldehyde concentration is above Cccp.
An acetate-tolerant mutant of Escherichia coli DH5α, DA19, was used for secretory production of human epidermal growth factor (hEGF) whose expression was under the control of phoA promoter. The recombinant cells were cultured in a chemically defined medium, and glucose was added at different specific provision rates during the growth and expression phases. It was found that pH had a significant effect on the extracellular hEGF production. The extracellular hEGF concentration was 75.5mg.L−1, 5.2-fold of the level reached at pH 7.0, even though more acetate was produced. Nitrogen source was limited in the later growth phase. Supplementation of ammonium promoted the consumption of phosphate and reduced the time to exhaust phosphate, but the extracellular hEGF production was similar to that without supplementation of ammonium.
The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS8 and 23 for the reaction temperatures of 25 and 60(C, respectively. The maximum observed sulfur removal in the present oxidative desulfurization system was 83.3%.
Decreasing the acetic acid consumption in purified terephthalic acid (PTA) solvent system has become a hot issue with common concern. In accordance with the technical features, the electrical conductivity is in direct proportion to the acetic acid content. General regression neural network (GRNN) is used to establish the model of electrical conductivity on the basis of mechanism analysis, and then particle swarm optimization (PSO) algorithm with the improvement of inertia weight and population diversity is proposed to regulate the operating conditions. Thus, the method of decreasing the acid loss is derived and applied to PTA solvent system in a chemical plant. Cases studies show that the precision of modeling and optimization are higher. The results also provide the optimal operating conditions, which decrease the cost and improve the profit.
At relatively high cellulose mass concentrations (8%, 10%, and 12%), homogeneous acetylation of cellulose was carried out in an ionic liquid, 1-allyl-3-methylimidazolium chloride (AmimCl). Without using any catalyst, cellulose acetates (CAs) with the degree of substitution (DS) in a range from 0.4 to 3.0 were synthesized in one-step. The effects of reaction time, temperature and molar ratio of acetic anhydride/anhydroglucose unit (AGU) in cellulose on DS value of CAs were investigated. The synthesized CAs were characterized by means of FT-IR, NMR, and solubility, mechanical and thermal tests. After the acetylation, the used ionic liquid AmimCl was easily recycled and reused. This study shows the potential of the homogeneous acetylation of cellulose at relatively high concentrations in ionic liquids in future industrial applications.
The hydrolysis technology and reaction kinetics for amino acids production from fish proteins in subcritical water reactor without catalysts were investigated in a reactor with volume of 400 ml under the conditions of reaction temperature from 180–320°C, pressure from 5-26 MPa, and time from 5-60 min. The quality and quantity of amino acids in hydrolysate were determined by bioLiquid chromatography, and 17 kinds of amino acids were obtained. For the important 8 amino acids, the experiments were conducted to examine the effects of reaction temperature, pressure and time on amino acids yield. The optimum conditions for high yield are obtained from the experimental results. It is found that the nitrogen and carbon dioxide atmosphere should be used for leucine, isoleucine and histidine production while the air atmosphere might be used for other amino acids. The reaction time of 30 min and the experimental temperature of 220°C, 240°C and 260°C were adopted for reaction kinetic research. The total yield of amino acids versus reaction time have been examined experimentally. According to these experimental data and under the condition of water excess, the macroscopic reaction kinetic equation of fish proteins hydrolysis was obtained with the hydrolysis reaction order of 1.615 and the rate constants being 0.0017,0.0045 and 0.0097 at 220°C, 240°C and 260°C respectively. The activation energy is 145.1 kJ·mol−1.
Iodine-sulfur (IS) thermochemical water-splitting cycle is the most promising massive hydrogen production process. To avoid the undesirable side reactions between hydriodic acid(HI) and sulfuric acid (H2SO4), it is necessary to purify the two phases formed by the Bunsen reaction. The purification process could be achieved by reverse reaction of the Bunsen reaction. In this study, the purification of the H2SO4 and HI Phases was studied. The purification proceeded in both batches and the continuous mode, the influences of operational parameters, including the reaction temperature, the flow rate of nitrogen gas, and the composition of the raw material solutions, on the purification effect, were investigated. Results showed that the purification of the H2SO4 phase was dominantly affected by the reaction temperature, and iodine ion in the sulfuric acid phase could be removed completely when the temperature was above 130°C; although, the purification effect of the HI phase improved with increasing of both the flow rate of nitrogen gas and temperature.
The esterification of free fatty acids (FFA) in waste cooking oil with methanol in the presence of Fe2(SO4)3/C (ferric sulfate/active carbon) catalyst was studied. The effects of different temperature, methanol/FFAmole ratio and amount of catalyst on the conversion of FFA were investigated. The results demonstrated that under optimal esterification conditions the final acid value of the resultant system can be reduced to ∼1 (mg KOH)·g−1 which met fully the requirements in post-treatment for efficient separation of glycerin and biodiesel. The kinetics ofthe esterification were also investigated under different temperatures. The results indicated that the rate-control stepcould be attributed to the surface reaction and the esterification processes can be well-depicted by the as-calculatedkinetic formula in the range of the experimental conditions.
Strain EDP3 was isolated from an industrial-activated sludge. It belonged to the gamma group of Proteobacteria with an identity of 97.0% to Acinetobacter calcoaceticus according to the 16S rRNA gene sequences. It can tolerate up to 1000mg.L-1 phenol at room temperature with a much longer lag phase. This indicates that higher phenol concentration has induced some physiological and genotypic changes in the bacterium. The aim of this study is, therefore, to investigate these responses to phenol concentration variations in strain EDP3. Proteome analysis is conducted by means of a two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was conducted to obtain a deeper insight into the adaptive responses inside the bacterium. Comparative analysis of the proteome profiles of strain EDP3 grown in 400mg.L-1 and 1000mg.L-1 phenol allowed us to identify that among all the proteins up-regulated under the higher phenol concentration, oxidative stress proteins were dominant. The synthesis of a heat shock protein, 60000 chaperonin GroEL, was also amplified. In addition, the expression of one membrane protein, adenosine 5'-triphosphate (ATP)-binding cassette (ABC) type sugar transporter, was found up-regulated. The inhibition of adenosine 5'-triphosphate (ATP) and RNA/protein synthesis was also observed.
In this article, poly(2-hydroxyethylmethacrylate-co-acrylamide) hydrogels were synthesized by bulk free-radical copolymerization of 2-hydroxyethylmethacrylate (HEMA) and acrylamide (AAm) for soft contact lens(SCL)-based ophthalmic drug delivery system. The copolymer was characterized with FT-IR and SEM, the swelling property of the hydrogels were studied by gravimetrical method, and chloramphenicol was used as a model drug to investigate drug release profile of the hydrogels. The results showed that poly(2-hydroxyethylmethacrylate- co-acrylamide) hydrogels were transparent and useful SCL biomaterial, the water content increased as AAm content increase and pH decrease, and in the same way, hydrogel composition affected chloramphenicol release process too. Migration rate of chloramphenicol increased as the AAm content in the hydrogels increased in the first stage of diffusion process, whereas there was no significant difference thereafter.
AbstractA two-component waterborne polyurethane (2K-WPU) was prepared by mixing water-soluble acrylic resin and hexamethylene diisocyanate biuret, and then diluted for phase inversion with water. Compared with water-soluble acrylic resin, the phase inversion of 2K-WPU occurs at lower water content. It is indicated by TEM that 2K-WPU particles show a core-shell structure, in which HDI biuret is encapsulated by hydrophilic acrylic resin. 2K-WPU emulsion with HDI biuret has larger particle size and narrower distribution index, while for 2K-WPU emulsion with HDI isocyanurate, the latex not only has large particle size, but also has two-peak distribution. FTIR shows that the reaction between HDI biuret and acrylic resin can complete in 12h. In addition, studies on effect of composition of acrylic resin on performance of 2K-WPU show that narrowing the polar difference between water-soluble acrylic resin and HDI biuret and improving the miscibility of two components are the key to prepare the transparent and high gloss films with high crosslinking density.
The shortage of petroleum has resulted in worldwide efforts to produce chemicals from renewable resources. Among these attempts, the possibility of producing acrylic acid from biomass has caught the eye of many researchers. Converting the carbohydrates first to lactic acid by fermentation and then dehydrating lactic acid to acrylic acid is hitherto the most effective way for producing acrylic acid from biomass. While the lactic acid fermentation has been commercialized since longer times, the dehydration process of lactic acid is still under development because of its low yield. Further efforts should be made before this process became economically feasible. Because of the existence of acrylic acid pathways in some microorganisms, strain improvement and metabolic engineering provides also a possibility to produce acrylic acid directly from biomass by fermentation.
Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However, the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD. Another problem with the activated sludge process is that large amount of waste activated sludge is produced, which needs further treatment. In this study, the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions, and the results were compared with those using acetic acid as the carbon source. The use of alkaline fermentation liquid not only affected the transformations of phosphorus, nitrogen, intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid. It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However, the former resulted in higher removal efficiencies for phosphorus (95%) and nitrogen (82%), while the latter showed lower ones (87% and 74%, respectively). The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency. Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source, which was responsible for its higher nitrogen removal efficiency. It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic followed by alternating aerobic-anoxic sequencing batch reactor.
The textural properties of acid-activated bentonite (AAB), which were prepared using four different concentrations of sulfuric acid, were analyzed by adsorption-desorption isotherm of nitrogen using an automated specific surface area and porosity analyzer. The total pore volume, specific surface area and average pore diameter of these four kinds of AAB show a regular changing trend, increasing first and then decreasing, the optimum of which can be achieved at a sulfuric acid concentration of 25% (sample A25). The kinetic analysis of the adsorption of β-carotene and chlorophyll in model oil solutions, namely, xylene and edible oil solution, has been investigated by using AAB. Experimental results indicated that the adsorption data fit the pseudo-second-order model well. The whole adsorption process of the two pigments on AAB was divided basically into two parts: the initial adsorption of pigments was rapid in the first 10 min, followed by a slower adsorption process till equilibrium was attained at 60 min. In addition, the amount and rate of adsorption on A25 increase synchronously with the initial pigment concentration and temperature. The results showed that the adsorption kinetics behavior of AAB with respect to the pigments is not influence by the xylene and edible oil solution.
AbstractThe present paper reports on extensive investigations using an ultrasonic treatment of WAS, to study its potential to meet one or all of four objectives: (1) reduce WAS quantities; (2) achieve a better dewaterability; (3) provoke a release of COD from the biosolids, preferably transformed into biodegradable organics and (4) possibly destroy the filamentous micro-organisms responsible for sludge bulking. The experiments are carried out in a batch reactor of volume up to 2.3L. The ultrasonic apparatus consisted of a generator, a converter and a sonotrode, supplied by Alpha Ultrasonics under the brand name of Telsonic. Three different sludge kinds were tested, at approximate concentration (DS/WAS) between 3.5 and 20g·L−1. The release of COD from the WAS-phase into the filtrate phase is a function of the specific energy-input SE with yields of about 30% achievable at SE-values of 30000 kJ·kg−1. A major fraction of the COD is transformed into biodegradable organics (BOD). The reduction of DS-fraction of the sludge is equivalent to the COD-release rates. Although the dry solids content (DS) is reduced, the dewaterability of the sludge is not improved. This reflects itself in a slightly decreased dryness of the filter cake using vacuum filtration, and in increased values of the capillary suction time (CST). This more difficult dewaterability is the result of considerably reduced floc sizes, offering an extended surface area. More surface water is bound (CST increases) and the filterability decreases due to clogging of the cake. To reach the same dryness as the untreated cake, the required dosage of poly-electrolyte increases proportionally with the level of ultrasound energy supplied. The ultrasonic reduction of filamentous WAS organisms is not conclusive and very little effect is seen at low intensities and short treatment durations. Microscopic analysis of the WAS identified the dominant presence of Actynomyces. Especially the release of COD and its transformation into BOD certainly merit further research.
Metal-loaded activated carbon fibers (ACFs) were prepared by impregnation and characterized by N2 adsorption at 77K, XRD, XPS and SEM. Their properties on SO2 removal were examined in a tubular fixed bed reactor with a model flue gas. Cobalt-loaded ACF showed the best activity among the prepared metal-loaded ACFs and a constant removal ratio of SO2 above 87% during continuous exposure to the flow of SO2/O2/H2O/N2 at 45°C for more than 216h. The characteristic of the prepared loaded-ACFs showed that the exceptional activity of Co-ACF was attributed to the high amount of active sites due to modification by loading cobalt.
Antioxidant and antimicrobial activities of Echinacea purpurea L. (Asteraceae) extracts obtained by classical and ultrasound solvent extraction were compared. The dry aerial part of plant was extracted by 70% ethanol at a solid-to-liquid ratio of 1:10 (m/v) and 25°C. The extract obtained by classical solvent extraction contained 29% larger amounts of phenolic compounds and 20% higher content of flavonoids. 2,2-diphenyl-1-picril hydrazyl radical (DPPH) scavenging reached 93.6% and the values of EC50 were (34.16±0.65) μg·ml−1 and (65.48±1.12) μg·ml−1 for the extracts obtained by the classical and ultrasound extractions, respectively. The extracts, independent of the extraction technique applied, showed a considerable growth inhibition on Candida albicans and Saccharomyces cerevisiae, while no growth inhibition zones were observed for Aspergillus niger. The diameters of inhibition zone observed for all the microorganisms were larger for extracts obtained by classical extraction than those by ultrasound extraction.
The polyphenol content, antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species (Artemisia vulgaris and Artemisia campestris) were compared. Ultrasound positively affected the yield of extractive substance and the kinetics of extraction, but the extract obtained by the classical extraction showed the highest antioxidant activities and contained higher total contents of phenolic compounds and flavonoids than the extracts obtained by two other extraction techniques. Both flavonoid aglycones (apigenin, quercetin, quercetin 3,37prime;-dimethyl ether) and flavonoid glycosides (rutin, hyperoside and kaempferol 3-rhamnoside) were identified by thin layer chromatograph (TLC) analysis in the extracts from both species. A. campestris extracts were richer in quercetin than A. vulgaris and its antimicrobial activity was also better than A. vulgaris. Extracts obtained from both species were found to be more effective on the tested yeasts than bacteria. The kinetics of the total extractive substances, such as phenolic, flavonoids and quercetin extraction, was successfully described by the model of unsteady-state diffusion.
A DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe quantum dot (QD) donors to Au nanoparticle (AuNP) acceptors is presented. CdTe QDs, 2.5nm in diameter, as energy donors, were prepared in water. Au nanoparticles, 16nm in diameter, as energy acceptors, were prepared from gold chloride by reduction. CdTe QDs were linked to 5'-NH2-DNA through 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride (EDC) as a linker, and the 3'-SH-DNA was self-assembled onto the surface of AuNPs. The hybridization of complementary double stranded DNA (dsDNA) bound to the QDs and AuNPs (CdTe-dsDNA-Au) determined the FRET distance of CdTe QDs and Au nanoparticles. Compared to the fluorescence of CdTe-DNA, the fluorescence of CdTe-DNA-Au conjugates decreased extremely, which indicated that the FRET occurred between CdTe QDs and Au nanoparticles. The fluorescence change of this conjugate depended on the ratio of Au-DNA to CdTe-DNA. When the AuNPs-DNA to QD-DNA ratio was 10:1, the FRET efficiency reached a maximum. The probe system would have a certain degree of fluorescence recovery when a complementary single stranded DNA was introduced into this system, which showed that the distance between CdTe QDs and Au nanoparticles was increased.
An adaptive state feedback predictive control (SFPC) scheme and an expert control scheme are presented and applied to the temperature control of a 1200 kt·a−1 delayed coking furnace, which is the key equipment for the delayed coking process. Adaptive SFPC is used to improve the performance of temperature control in normal operation. A simplified nonlinear model on the basis of first principles of the furnace is developed to obtain a state space model by linearization. Taking advantage of the nonlinear model, an online model adapting method is presented to accommodate the dynamic change of process characteristics because of tube coking and load changes. To compensate the large inverse response of outlet temperature resulting from the sudden increase of injected steam of a particular velocity to tubes, a monitoring method and an expert control scheme based on heat balance calculation are proposed. Industrial implementation shows the effectiveness and feasibility of the proposed control strategy.
Composition estimation plays very important role in plant operation and control. Extended Kalman filter (EKF) is one of the most common estimators, which has been used in composition estimation of reactive batch distillation, but its performance is heavily dependent on the thermodynamic modeling of vapor-liquid equilibrium, which is difficult to initialize and tune. In this paper an inferential state estimation scheme based on adaptive neuro-fuzzy inference system (ANFIS), which is a model base estimator, is employed for composition estimation by using temperature measurements in multicomponent reactive batch distillation. The state estimator is supported by data from a complete dynamic model that includes component and energy balance equations accompanied with thermodynamic relations and reaction kinetics. The mathematical model is verified by pilot plant data. The simulation results show that the ANFIS estimator provides reliable and accurate estimation for component concentrations in reactive batch distillation. The estimated states form a basis for improving the performance of reactive batch distillation either through decision making of an operator or through an automatic closed-loop control scheme.
A new version of differential evolution (DE) algorithm, in which immune concepts and methods are applied to determine the parameter setting, named immune self-adaptive differential evolution (ISDE), is proposed to improve the performance of the DE algorithm. During the actual operation, ISDE seeks the optimal parameters arising from the evolutionary process, which enable ISDE to alter the algorithm for different optimization problems and improve the performance of ISDE by the control parameters' self-adaptation. The performance of the proposed method is studied with the use of nine benchmark problems and compared with original DE algorithm and other well-known self-adaptive DE algorithms. The experiments conducted show that the ISDE clearly outperforms the other DE algorithms in all benchmark functions. Furthermore, ISDE is applied to develop the kinetic model for homogeneous mercury (Hg) oxidation in flue gas, and satisfactory results are obtained.
One-dimensional heterogeneous plug flow model was employed to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether. Longitudinal temperature and conversion profiles predicted by this model were compared to those experimentally measured in a bench scale reactor. The reactor was packed with 1.5 mm γ-Al2O3 pellets as dehydration catalyst and operated in a temperature range of 543-603 K at an atmospheric pressure. Also, the effects of weight hourly space velocity (WHSV) and temperature on methanol conversion were investigated. According to the results, the maximum conversion is obtained at 603.15 K with WHSV of 72.87 h−1.
Lanthanum alginate bead is a new, highly active adsorbent. In the present study, we investigated its adsorption performance and its adsorption mechanism. The adsorption isotherm for fluoride onto lanthanum alginate bead fits the Langmuir model well, and the maximum adsorption capacity is 197.2 mg·g−1. X-ray diffraction shows the amorphous nature of lanthanum alginate bead, which allows for better accessibility to fluoride and thus better activity. Infrared spectra of lanthanum alginate bead before and after adsorption confirm its stable skeletal structure. Scanning electron microscopy shows that the dense surface structure of the adsorbent appear cracks after adsorption. The adsorption mechanism of lanthanum alginate bead is considered as an ion exchange between F− and Cl− or OH−, as verified from the adsorbent and the solution by pH effect, energy dispersive X-ray, and ion chromatography.
The carbonaceous adsorbent was prepared from mixtures of dewatered sludge and sawdust with enhanced ZnCl2 chemical activation. Characteristics of the adsorbent were studied using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and adsorption of nitrogen. The surface analysis showed that the carbonaceous adsorbent had good specific surface and porosity (394 m2·g−1 of BET surface, 0.12 and 0.10 ml·g−1 of microporous and mesoporous volume, respectively). The oxygen functional groups such as OH, CO and CO were found on the surface by FTIR and XPS (X-ray photoelectron spectroscopy). The adsorption of elemental mercury (Hg0) on the carbonaceous adsorbent was studied in a fixed bed reactor. The dynamic adsorption capacity of carbonaceous adsorbent increased with influent mercury concentration, from 23.6 μg·g−1 at 12.58 μg·m−3 to 87.9 μg·g−1 at 72.50 μg·m−3, and decreased as the adsorption temperature increased, from 246 μg·g—1 at 25°C to 61.3 μg·g−1 at 140 °C, when dry nitrogen was used as the carrier gas. The carbonaceous adsorbent presented higher dynamic adsorption capacity than activated carbon, which was 81.2 μg·g—1 and 53.8 μg·g−1 respectively. The adsorption data were fitted to the Langmuir adsorption model. The physical and chemical adsorption were identified on the adsorbent.
Expanded bed adsorption (EBA), a promising and practical separation technique, has been widely studied in the past two decades. The development of adsorbents for EBA process is a challenging course, with the special design and preparation according to the target molecules and specific expanded bed systems. Many types of supporting matrices for expanded bed adsorbents have been developed, and their preparation methods are being consummated gradually. These matrices are activated and then coupled with ligands to form functionalized adsorbents, including ion-exchange adsorbents, affinity adsorbents, mixed mode adsorbents, hydrophobic charge induction chromatography adsorbents and others. In this review, the preparation of the matrices for EBA process is summarized, and the coupling of ligands to the matrices to prepare functionalized adsorbents is discussed as well.
The separation of hydrogen and deuterium by cryogenic adsorption was conducted, using the molecular sieve 5A as adsorbent, helium as the carrier gas in a fixed column. The breakthrough curves of hydrogen, deuterium and the mixture of two components in helium carrier gas were measured, a separation factor, approximately 2, for the hydrogen-deuterium binary mixture was obtained. The equilibrium model was built for simulation of the concentration distribution for single hydrogen, deuterium and their mixture with helium carrier in the fixed column, and the simulation compared well with the experimental results.
The adsorption of methyl orange onto ultrafine coal powder (UCP) and modified ultrafine coal powder (MUCP) from aqueous solutions were studied, in which the influence of contact time, dosage, temperature, pH, and methyl orange concentration in the solution were investigated. The adsorption kinetics of methyl orange by UCP and MUCP can be described by the Lagergren first-order and pseudo second-order kinetic models, respectively. The adsorption isotherms of methyl orange onto MUCP at 303, 313 and 323 K follow the Freundlich and Langmuir isotherm equation. Values of ΔG0 for methyl orange adsorption onto MUCP are −22.55, −23.10 and −23.79 kJ·mol−1 at 303, 313, and 323 K, respectively. The values of ΔH0 and ΔS0 are −3.74 kJ·mol−1 and 61.99 J·mol−1, respectively. The adsorption process is spontaneous and exothermic.