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The removal of methyl orange using coal fly ash, which is a widely available low-cost adsorbent, has been investigated. Adsorption studies for dye removal were conducted using various configurations such as batch, column and heap adsorption at various temperatures and adsorbent dosages at neutral pH. The Langmuir, Freundlich and Tempkin isotherm models were used to describe the process. The Freundlich model best represented the adsorption. Kinetic studies show the adsorption followed pseudo-second-order kinetics. Thermodynamic studies show that the process is spontaneous, endothermic and random. Column configuration was found to be the most efficient with a dye removal percentage of 99.95%, followed by heap adsorption at 99.25% removal and lastly batch configuration with 96.68% removal. Economic analysis shows that column operation would be the most effective for practical implementation.

A novel continuous flow reactive crystallization process for the in situ on-demand access of single enantiomer crystals is reported and exemplified for a chiral pharmaceutical intermediate that crystallizes as a racemic conglomerate. During this process, a nearly racemic feed suspension with a racemization catalyst is circulated through a tubular coiled milli-reactor immersed in two thermostatic baths set at different temperatures. This flow configuration enables rapid heat transfer, which in turn results in successive spatial cycles of dissolution and re-crystallization carried out at extremely short residence times, unattainable in batchwise operations. By tuning the number of cycles, residence time per cycle and feed suspension density we show that unprecedented productivities (>20 g L−1 h−1) of the preferred enantiomer at purities >98% can be attained that could easily suit industrial demand in a directly scalable process.

International audience; The dissolution kinetics of different varieties of natural gypsum samples with different porosity and content of insoluble impurities are experimentally investigated under unsaturated conditions. The main goal of this work is to verify whether and how the petrophysical and petrographic nature of gypsum influence its dissolution rate. Gypsum samples were taken from Priabonian (Ludian) and Lutetian formations located in the north-eastern suburbs of Paris, where the development of sinkholes due to gypsum dissolution is a common phenomenon. Experiments using the rotating disk technique allow us to determine the kinetic rate model parameters of each sample in pure water following the empirical rate expression derived from mixed kinetic theory. The kinetic order n shows a dispersion around a mean value n=1.2 and k, the pure dissolution rate coefficient varies according to the facies and the experimental conditions (k ≈1×10−6 to 8×10−6 mmol/cm2/s). These results are adjusted according to the specific roughness and texture of each sample, for the results to be more representative of in situ conditions. Batch experiments are also performed to evaluate the extremely low dissolution rates when the solution is close to equilibrium. The results reveal a double kinetics: far from equilibrium, the dissolution rates show that the linear behavior and the kinetic parameters are relatively close with the values found using the rotating disk method. For concentrations greater than 0.94 ± 0.02 of the equilibrium concentration Cref, the dissolution rates show a linear behavior but with greater slope depending on the texture of the mineral. No changes of the dissolution rates were observed on pure gypsum crystals when non soluble solid impurities are added. However, a small degree of uncertainty around the value of Cref show a significant effect on the parameters of the second kinetics.

The production of levan by Bacillus licheniformis NS032 in a medium based on sugar beet molasses was studied. High polysaccharide yields were produced by using diluted molasses (100–140 g/L of total sugars) with the addition of commercial sucrose up to 200 g/L of total sugars, as well as K2HPO4. A levan yield of 53.2 g/L was obtained on a medium optimized by response surface methodology, containing 62.6% of sugar originating from molasses, and 4.66 g/L of phosphate, with initial pH value of 7.2. In comparison to the media with 200 and 400 g/L sucrose, in the molasses optimized medium, the observed bacterial growth was faster, while the maximum production of polysaccharide was achieved over a shorter time interval (48 h). The polysaccharide produced in molasses medium had a weight average molecular weight of 5.82 × 106 Da, degree of branching 12.68%, viscosity of 0.24 dL/g, and based on methylation analysis and NMR data, it did not significantly differ from levan obtained in the medium with 200 g/L sucrose. © 2018 Elsevier B.V. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/2943] This is peer reviewed version of the following article: Gojgic-Cvijovic, G. D.; Jakovljevic, D. M.; Loncarevic, B. D.; Todorovic, N. M.; Pergal, M. V.; Ciric, J.; Loos, K.; Beškoski, V.; Vrvić, M. M. Production of Levan by Bacillus Licheniformis NS032 in Sugar Beet Molasses-Based Medium. International Journal of Biological Macromolecules 2019, 121, 142–151. [https://doi.org/10.1016/j.ijbiomac.2018.10.019]

A batch study was done for exploring the performance of eggshell powder (EGP) for adsorptive removal of carbaryl from aqueous solution. In the experiment, the operating factors were initial carbaryl concentration (5–20 mg L−1), solution pH (2–10), adsorbent dose (0.01–0.1 g/100 ml) and contact time (10–60 min). For optimization, evaluation of the effects and interactions of the operating factors response surface modeling was applied and the influence of the factors was checked through a two-level four factor Box–Behnken design (BBD) model. The predicted data had shown good agreement (R 2 = 0.9985) with experimental data. Furthermore, the adsorption data were best fitted with Freundlich isotherm and pseudo-second-order kinetics. Thermodynamic parameters revealed that the adsorption of process was spontaneous and endothermic. Finally it can be concluded that the EGP can be used as an alternative adsorbent for the removal of carbaryl from aqueous medium.

Serogroup C polysaccharide from Neisseria meningitidis (PS) constitutes the antigen for the respective vaccine production. In order to investigate the enhancement of the final PS concentration (Pf), as well as the overall yield factor (PS/biomass) (YP/X), 13 total cultivations distributed in 6 series (from A to F) were carried out in Frantz medium (40 L plus inoculum) in a 80L bioreactor at 35oC, 0.4 atm, 120 rpm, airflow rate of 5 L/min and KLa = 4.2 h-1. The series (A-F) correspond to different experimental conditions as follows: A) without pH and dissolved O2 controls; B) pH control at 6.5; C) pH control at 6.5 and glucose pulse at the 10th hour; D) dissolved O2 control at 10% saturation value; E) pH control at 7.4; F) dissolved O2 limitation (set rotation at 55 rpm). Concentrations of dry biomass, PS, cellular nitrogen, residual glucose, organic and inorganic nitrogen in the medium were measured. The best results were represented by series A (averages of Pf = 0.15 g/L and YP/X = 107 mg/g). The presented findings could be useful for a proper Frantz medium reformulation in order to obtain a greater amount of PS and improve the vaccine development in industrial scale-up production.

BIOTON&reg, biochar, produced by a wood biomass pyrolysis process, which is usually applied as soil amendment, was investigated for a novel application, i.e., the adsorption of lead from contaminated solutions. The experimental activity included physical and chemical characterization of BIOTON&reg, and Scanning Electron Microscope (SEM) images to highlight its internal structure. The adsorption process was investigated through batch and column experiments. Adsorption kinetics showed very rapid achievement of equilibrium conditions, i.e., 50 mg/L and 100 mg/L initial Pb concentration at 2 h and 4 h, respectively. Complete removal also occurred within the same time. The Brunauer&ndash, Emmett&ndash, Teller model was a better fit for the equilibrium data of both Pb concentrations, whereas the kinetics were best represented by the pseudo second-order model. Column tests showed that the addition of biochar as an adsorbent media within the bed significantly extended the time of breakthrough and exhaustion, with respect to the column filled with soil only. The values found for the adsorption capacity of BIOTON&reg, versus lead-containing solutions were comparable to those reported for commercial adsorbents. Therefore, BIOTON&reg, can be considered a valid option: It also offers the additional benefit of allowing the recovery of a residue, which alternately would need to be disposed of.

WOS: 000411432200001, Nanoscale zero valent iron (nZVI) and functional pumice modified nanoscale zero valent iron (P-nZVI) were successfully synthesized and used for the removal of tetracycline (TC). These materials were characterized by SEM, TEM, XRD, FTIR, BET. Different factors such as the mass ratio, dosage of adsorbent, pH, initial TC concentration and temperature were investigated. Based on these results; a possible removal mechanism was proposed including TC adsorption and TC reduction via oxidation of Fe-0 to Fe3+. In addition, isotherm and thermodynamic parameters were applied to the equilibrium data. The maximum adsorption capacity of TC by nZVI and P-nZVI was 105.46 mg/g and 115.13 mg/g, respectively. Adsorption and reduction kinetics were examined for the TC removal process. The pseudo-second-order model and pseudo-first-order model was observed for adsorption and reduction process, respectively. Finally, more than 90% of TC from aqueous solutions was removed by nZVI and P-nZVI., Scientific Research Project Fund of Cumhuriyet University [M-479], This work was supported by the Scientific Research Project Fund of Cumhuriyet University under Grant [number M-479].

Electrocoagulation (EC) was used for the removal of anthraquinone dye, Alizarin Red S (ARS) from aqueous solution, the process was carried out in a batch electrochemical cell with Al electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process were investigated. Equilibrium was attained after 10 minutes at 30 oC. Pseudo-first-order, pseudo-second-order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic of the electrocoagulation process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analyzed using six isotherm models: Langmuir, Freudlinch, Redlich–Peterson, Temkin, Dubinin–Radushkevich and Sips isotherms and it was found that the data fitted well with Dubinin–Radushkevich and Sips isotherm model. The study showed that the process depend on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (∆Go, ∆Ho and ∆So) indicated that the process is spontaneous and endothermic in nature.

In CSTRs, ferrous iron was biologically oxidized followed by crystallization of scorodite (FeAsO 4 ·2H 2 O) at pH 1.2 and 72 °C. The CSTRs were fed with 2.8 g L −1 arsenate and 2.4 g L −1 ferrous and operated at an HRT of 40 h, without seed addition or crystal recirculation. Both oxidation and crystallization were stable for periods up to 200 days. The arsenic removal efficiency was higher than 99% at feed Fe/As molar ratios between 1 and 2, resulting in effluents with 29 ± 18 mg As L −1 . Arsenic removal decreased to 40% at feed Fe/As molar ratios between 2 and 5. Microorganisms were not affected by arsenic concentrations up to 2.8 g As 5+ L −1 . The bioscorodite solid yield was 3.2 g/g arsenic removed. Bioscorodite crystals precipitated as aggregates, causing scaling on the glass wall of the reactor. The observed morphology through SE microscopy of the precipitates appeared amorphous but XRD analysis confirmed that these were crystalline scorodite. Arsenic leaching of bioscorodite was 0.4 mg L −1 after 100 days under TCLP conditions, but when jarosite had been co-precipitated leaching was higher at 0.8 g L −1 . The robustness of the continuous process, the high removal efficiency and the very low arsenic leaching rates from bioscorodite sludge make the process very suitable for arsenic removal and disposal.

The adsorption behavior of Rhodamine B dye from aqueous solutions was investigated onto the cation-exchange resin, Duolite C-20 (hydrogen form). The effects of various experimental factors; sorbent amount, contact time, dye concentration and temperature, were studied by using the batch technique. Lagergren pseudo-first-order equation shows good applicability with high correlation coefficients for all ranges of initial dye concentrations and at different temperatures. This equation was used to describe the kinetics of the dye adsorption process. The adsorption constants were evaluated by using both the Langmuir and Freundlich adsorption isotherm models. Thermodynamic parameters were obtained and it was found that the adsorption of Rhodamine B dye onto Duolite C-20 resin was an endothermic and spontaneous process at the temperatures under investigation.

A mathematical model describing the behavior of a continuous culture that degrades 1,2-dichloroethane and receives a shock loading of another compound was developed. The model takes into account possible cell death due to toxicity, growth inhibition and additional growth of cells on the second carbon source. Biodegradation is coupled to cell growth on the additional carbon source or by incomplete and unproductive degradation.The model was tested with Xanthobacter autotrophicus strain GJ10 growing on 1,2-dichloroethane in a continuous stirred tank bioreactor. Dichloromethane, dibromomethane, 1,2-dibromoethane, monofluoroacetate, monochloroacetate and monochloroacetic acid were added separately in the form of a pulse. The effects that were observed varied from low toxicity in case of dihalomethanes and chloroacetate up to severe cell death followed by culture washout in the case of monofluoroacetate and 1,2-dibromoethane. The experimental profiles were in most cases satisfactorily described with the proposed model.

8 Páginas; 3 Tabals, 1 Figura, The effect of a microwave (MW) pre-treatment on two-phase olive mill solid residue (OMSR) or alperujo with a view to enhancing its anaerobic digestibility was studied. The MW pre-treatment was carried out at a power of 800 W and at a targeted temperature of 50 °C using different heating rates and holding times. The following specific energies were applied: 4377 kJ·kg TS−1 (MW1), 4830 kJ·kg TS−1 (MW2), 7170 kJ·kg TS−1 (MW3) and 7660 kJ·kg TS−1 (MW4). The maximum methane yield, 395±1 mL CH4·g VSadded−1, was obtained for MW4. The effect of the pre-treatment on the kinetics of the process was also studied. The methane production curves generated during the batch tests showed a first exponential stage and a second sigmoidal stage for all the cases studied. In the first stage, the kinetic constant for the pre-treatment MW1 was 54.8% higher than that obtained for untreated OMSR., Impacto del pretratamiento con microondas sobre la digestión anaerobia en régimen discontinuo de residuos sólidos de almazaras de dos fases: un enfoque cinético. El efecto del pretratamiento con microondas (MW) sobre el residuo semisólido procedente de la elaboración del aceite de oliva por el sistema de dos fases o alperujo fue estudiado con el objeto de aumentar su digestibilidad anaerobia. El pretratamiento fue llevado a cabo a una potencia de 800W y a una temperatura de 50 °C empleándose distintas velocidades de calentamiento así como diferentes tiempos de espera para obtener dichas condiciones. Las siguientes energías específicas fueron aplicadas: 4377 kJ·kg TS−1 (MW1), 4830 kJ·kg TS−1 (MW2), 7170 kJ·kg TS−1 (MW3) y 7660 kJ·kg TS−1 (MW4). El máximo rendimiento 395±1 mL CH4·g SVañadidos−1 se obtuvo para MW4. El efecto del pretratamiento en la cinética del proceso también fue estudiado. Las curvas de producción de metano durante los ensayos mostraron una etapa exponencial y una sigmoidal en todos los casos. En la primera etapa, la constante cinética para MW1 fue 54.8% mayor que la obtenida para el alperujo sin pretratar., The authors wish to express their gratitude to the Ministerio de Ciencia e Innovación (project CTM2011–25762/TECNO) and Junta de Andalucía (project RNM-1970) for providing financial support. Dr. Rincón wishes to thank the Ramón y Cajal Program (RYC-2011–08783 contract) from the Spanish Economy and Competitiveness Ministry for providing financial support.

In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime.

The feasibility of reactive distillation (RD) for the reversible acetalization of glycerol with formaldehyde is evaluated through experiments and simulations. Simultaneous removal of acetal and water from the reactive zone of the RD column helps shift the reaction in the forward direction and achieve close to quantitative conversion levels. The results of laboratory-scale RD experiments performed in this study are compared with the ones predicted by simulation using the kinetics developed in the present work. Since commercial formaldehyde is available in the form of its aqueous solution, a large amount of water has to be removed to achieve substantial conversion. An experimentally validated simulator is thus used to design an appropriate RD configuration that offers minimum energy consumption. Toluene is used as an entrainer to remove water from the RD column. The process is compared with the reported indirect route of transacetalization of glycerol with methylal.

Batch experiments were carried out for conversion of cellulose to lactic acid by simultaneous saccharification and fermentation (SSF) at different pH values. Saccharification was carried out with a cellulase enzyme preparation from T. reesei and fermentation was by L. bulgaricus. A kinetic model was developed to simulate SSF by incorporating cellulase enzyme kinetics with growth kinetics of L. bulgaricus. The enzyme kinetics were fitted by a Michaelis-Menten type equation, while the growth kinetics of L. bulgaricus were represented by a cybernetic-type model incorporating lactate and undissociated lactic acid inhibition term. The saccharification of cellulose was rate-limiting above pH 5, while lactic acid fermentation was rate limiting below pH 5. The glucose concentration in the fermentation broth was lower than that in simple saccharification (SS) at all pH values. Lactic acid productivity (0.45 g/l/h) was maximum at pH 5 and was higher than that of lactic acid productivity by SS followed by fermentation The kinetic model was able to predict the performance of SSF quite well. (C) 1997 .

International audience; An experimental protocol in batch reactor was designed for the measurement of the methane yield and of the kinetics of degradation of particulate substrates. This protocol requires successive batches to be carried out until the evolution of the biogas production is reproducible from one batch to the other. The developed protocol was applied to 18 particulate substrates in order to start a data base including the methane yield and the kinetics of degradation of the organic matter. The data were used for modelling the behaviour of a co-digestion reactor treating a mixture of 5 fruits and vegetables.

International audience; Selenium is a known toxic element released in the environment by anthropogenic activities. The present study is devoted to the aqueous sorption behaviour of selenium oxyanions (selenate and selenite) on a reference oxide surface, namely rutile TiO2. Batch sorption kinetics and isotherms have been studied using different physico-chemical conditions of the solution (changes of pH and ionic strength). The sorption was favoured for both anions in acidic conditions, in agreement with a surface complexation mechanism and CD-MUSIC predictions. Spectroscopic investigations of the sorbed rutile powder were also consistent with such a mechanism. EXAFS spectra confirmed that for selenite anions, an inner-sphere mechanism was the most probable process observed. Dynamic sorption experiments using a column filled with rutile powder also substantiated that a part of the surface complexes follows the inner-sphere mechanism, but also evidenced that an outer-sphere mechanism cannot be excluded, especially for selenate anions.

In biotechnological recovery processes the instabily of the product can lead to large losses in the sequence of recovery processes needed to purify the product. As the cost of the final active product is strongly dependent on the recovery yield, this will lead to an increase in product cost. Therefore knowledge of factors that influence stability is important. This Part 2 provides the basic principles for design and operation of processes in which inactivation takes place. Simple kinetics and reactor modelling are discussed. These are applied to a number of unit operations: cell disruption, membrane filtration, drying and reversed micellar extraction. It is thus shown that the basic tools for modeling of biochemical processes provide us with the data needed for optimal process design and operation.

A mathematical model describing the behavior of a continuous culture that degrades 1,2-dichloroethane and receives a shock loading of another compound was developed. The model takes into account possible cell death due to toxicity, growth inhibition and additional growth of cells on the second carbon source. Biodegradation is coupled to cell growth on the additional carbon source or by incomplete and unproductive degradation. The model was tested with Xanthobacter autotrophicus strain GJ10 growing on 1,2-dichloroethane in a continuous stirred tank bioreactor. Dichloromethane, dibromomethane, 1,2-dibromoethane, monofluoroacetate, monochloroacetate and monochloroacetic acid were added separately in the form of a pulse. The effects that were observed varied from low toxicity in case of dihalomethanes and chloroacetate up to severe cell death followed by culture washout in the case of monofluoroacetate and 1,2-dibromoethane. The experimental profiles were in most cases satisfactorily described with the proposed model.

The aim of this research was to expose individual removals of copper, chromium, nickel, and lead from aqueous solutions via biosorption using nonliving algae species, Chara sp. and Cladophora sp. Optimum pH values for biosorption of copper (II), chromium (III), nickel (II), and lead (II) from aqueous solutions were determined to be 6, 7, 7, and 3 for Cladophora sp. and 5, 3, 5, and 4 for Chara sp. respectively. Maximum adsorption capacities of Chara sp. [10.54 for chromium (III) and 61.72 for lead (II)] and Cladophora sp. [6.59 for chromium (III) and 16.75 and 23.25 for lead (II)] for chromium (III) and lead (II) are similar. On the other hand, copper (II) and nickel (II) biosorption capacity of Cladophora sp. [ 14.28 for copper (II) and 16.75 for nickel (II)] is greater than Chara sp. [6.506 for copper (II) and 11.76 for nickel (II)]. Significantly high correlation coefficients indicated for the Langmuir adsorption isotherm models can be used to describe the equilibrium behavior of copper, chromium, nickel, and lead adsorption onto Cladophora sp. and Chara sp.

Many bacteria have been observed to stop growing below a certain substrate threshold concentration. In this study, a modification of the Monod kinetics expression has been proposed to take into account this substrate threshold concentration observed in bacterial growth. Besides the threshold concentration no additional parameters have been added to the kinetic expression and so, only the substrate threshold concentration and the half-saturation constant have to be estimated for model calibration purposes. Furthermore, for parameter estimation purposes, practical identifiability of this new function has been studied and the results have been satisfactory. The new model has been applied, as an example, to a simple anaerobic model to simulate the competition for hydrogen between sulphate reducers and methanogens in a thermophilic methanol-fed bioreactor. Oscillatory behaviour and mathematical instabilities have been avoided by using the proposed model. Parameter sensitivities have also been calculated along the simulation period in order to investigate the importance of hydrogen threshold concentration parameters.

The aim of this study was to evaluate the suitability of several mathematical functions for describing microbial growth curves. The nonlinear functions used were: three-phase linear, logistic, Gompertz, Von Bertalanffy, Richards, Morgan, Weibull, France and Baranyi. Two data sets were used, one comprising 21 growth curves of different bacterial and fungal species in which growth was expressed as optical density units, and one comprising 34 curves of colony forming units counted on plates of Yersinia enterocolitica grown under different conditions of pH, temperature and CO(2) (time-constant conditions for each culture). For both sets, curves were selected to provide a wide variety of shapes with different growth rates and lag times. Statistical criteria used to evaluate model performance were analysis of residuals (residual distribution, bias factor and serial correlation) and goodness-of-fit (residual mean square, accuracy factor, extra residual variance F-test, and Akaike's information criterion). The models showing the best overall performance were the Baranyi, three-phase linear, Richards and Weibull models. The goodness-of-fit attained with other models can be considered acceptable, but not as good as that reached with the best four models. Overall, the Baranyi model showed the best behaviour for the growth curves studied according to a variety of criteria. The Richards model was the best-fitting optical density data, whereas the three-phase linear showed some limitations when fitting these curves, despite its consistent performance when fitting plate counts. Our results indicate that the common use of the Gompertz model to describe microbial growth should be reconsidered critically, as the Baranyi, three-phase linear, Richards and Weibull models showed a significantly superior ability to fit experimental data than the extensively used Gompertz.

A new, low-cost, available sorbent, cedar cone (CC), was tested for its ability to remove basic dye Rhodamine B (RhB) from aqueous solutions. Sorption kinetics of RhB from aqueous solution on CC were studied in a batch process. In order to understand the mechanisms of RhB sorption by CC, the models of Weber and Morris and Boyd were applied. It was found that For the intraparticle diffusion model the sorption of RhB by the CC is divided into three stages: (i) the instantaneous sorption or external surface sorption, (ii) the gradual sorption stage where intraparticle diffusion is the rate limiting and (iii) the final equilibrium stage where intraparticle diffusion starts to slow down due to the extremely low sorbate concentrations left in the solutions. The effects of operating conditions such as ionic strength, contact time and solution pH were studied. The results obtained show the ability of cedar cone for the elimination of RhB in aqueous solution. The ionic strength has no effect on the kinetics of sorption. The maximum sorption (4.55 mg g-1) was obtained at pH equal to 3. The contact time was estimated for 360 min. The sorption isotherms of RhB by the CC at different temperatures were studied. It was found that the isotherms showed the shape of type L, which means that there is no strong competition between the solvent and sorbate to occupy the sorption sites.