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In recent years, significant attention has been dedicated to converting biomass carbohydrates into alkyl levulinates (biofuel additives) in alcoholic media, in search of various cheap and active solid catalysts through relatively easy pathways and from non-dangerous precursors. The synthesis of methyl levulinate (ML) using a new Bronsted/Lewis acid sites catalyst was investigated, emphasizing the influence of three parameters (catalyst loading, the molar concentration of fructose in methanol, and reaction temperature) on the process. The synthetized catalyst, SO42−/TiO2–La2O3 coating Fe3O4, was characterized by different techniques (FT-IR, XRD, TGA, TEM-EDX, ICP-OES). The design of the ML synthesis experiment was carried out using the Box-Behnken technique, while the response surface methodology was applied to obtain the optimized process conditions. A mathematical model of the catalytic synthesis was built, based upon first principles, and the experimental time variation of the reaction mixture concentrations was used to find, through regression, the values of the constants of a newly proposed kinetic model.

Propolis, a complex bee product, is a source of numerous bioactive principles, beneficial for human health, therefore it is intensively studied. In the present work, extracts of propolis from Bihor Romanian County were studied to identify the relationship between the polyphenolic derivatives profile and their antioxidant and antimicrobial activity. Extracts were obtained using water and 25%, 50%, and 70% ethanolic solutions (w/w), at 2:1, 4:1, and 6:1 liquid: solid ratios (w/w). 21 polyphenolic derivatives were quantified by UHPLC-MS, proving that the extracts composition strongly depends on the solvent. The sum of quantified polyphenolics extracted varied between 1.5 and 91.2 mg/g propolis. The antioxidant capacity was evaluated using the free radicals 2,2’-azino-bis (3-ethylbenzothiazoline-6 sulfonic acid) diammonium salt (ABTS) and 1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging methods. Antimicrobial efficiency was tested against Gram-positive (B. subtilis), Gram-negative bacteria (E. coli), and fungi (C. albicans) by disc-diffusion method. All extracts, even the aqueous ones, demonstrated antibacterial and antifungal activity. Chemometric methods (partial least squares) and a saturation-type model were used to evaluate the contribution of various bioactive principles in building the antioxidant capacity of extracts. Both experimental and modelling results show that 50% ethanolic extracts provide a rich polyphenolics profile and ensure a good antioxidant capacity.

Fish oils with a high content of polyunsaturated fatty acids (PUFAs) are gaining increasing interest in the food and nutraceutical industry, due to their important functional properties for human beings� health improvement. The most important PUFAs have at least two double bonds placed on the carbon chain. These include ?-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahaxaneoic acid (DHA). Microencapsulation is a technique used to protect the bioactive compounds from oxidative damage, to ensure their controlled release and to activate the synergistic effect of the ingredients, if it exists. In this context, the microencapsulation process of fish oils rich in PUFAs using alginate was studied, in the presence and the absence of an ultrasonic (US) field. Both BoxBehnken design of experiment technique and the Response Surface Method were used, to investigate the influence of the process parameters and to optimize the operating conditions. The operating parameters under investigation were the sodium alginate to fish oil ratio, the calcium chloride concentration and time being the objective. The fish oil microspheres had a homogeneous round shape, a diameter of 0.12 � 0.02 mm. Physicochemical description of microcapsules was performed using modern characterization methods.

Ultrasound-assisted extraction (UAE) was applied for polyphenols extraction from Romanian propolis, followed by comparison with previous maceration work. The effects consisted not only in time reduction and extraction yield increase, but also in polyphenolics profile modification in terms of flavonoids / polyphenolic acids ratio. The operating parameters were ultrasounds (US) field exposure time (10-100 min), solvent composition (water, 25 % and 50 % ethanolic solutions, w/w), and liquid:solid ratio (2:1, 4:1 and 6:1, w:w), while keeping temperature constant. 24 polyphenolic derivatives were quantified by UHPLC-HRMS. UAE favored the extraction of pinocembrin, isorhamnetin and chrysin in water and 25 % ethanol, leading to different profiles than maceration, and further influences upon the antioxidant and antimicrobial activity. All extracts demonstrated increased antibacterial and antifungal activity compared to maceration, particularly the 50 % ethanolic extracts, which presented a three-times larger antioxidant capacity. Chemometric methods (Principal Component Analysis - PCA and Partial Least Squares Regression - PLS) and a saturation type model were used to correlate the polyphenolics profiles and antioxidant capacity. Experimental and modelling results concluded that 50 % ethanolic solutions and UAE represent the favorable operating conditions in terms of yield and extracts quality.

In this study, the SO42-/TiO2-La2O3-Fe2O3 catalyst was prepared and tested in the conversion of fructose to ethyl levulinate . The catalyst was characterized from the point of view of the textural analysis, FT-IR analysis, acid strength distribution, X-ray powder diffraction and pyridine adsorption IR spectra. The influence of the reaction parameters on the ethyl levulinate yield was study. The maximum yield of 37.95% in levulinate esters was obtained at 180 �C, 2 g catalyst and 4 h reaction time. The effect of ethyl levulinate addition to diesel-biodiesel blend in different rates, i.e, 0.5, 1, 2.5, 5 (w.t %) on density, kinematic viscosity and flash point was evaluated and compared with the European specification.

Polyunsaturated fatty acids (PUFA) have a preventive effect on high blood pressure. [...]

Recent advances and large-scale use of hybrid imaging modalities like PET-CT have led to the necessity of improving nano-drug carriers that can facilitate both functional and metabolic screening in nuclear medicine applications. In this study, we focused on the evaluation of four potential imaging nanoparticle structures labelled with the 68Ga positron emitter. For this purpose, we functionalized NHS-activated PEG-gold nanoparticles with 68Ga-DOTA-Neuromedin B, 68Ga-DOTA-PEG(4)-BBN(7-14), 68Ga-DOTA-NT and 68Ga-DOTA-Neuromedin N. In vitro binding kinetics and specific binding to human HT-29 colon carcinoma cells and DU-145 prostate carcinoma cells respectively were assessed, over 75% retention being obtained in the case of 68Ga-DOTA-PEG(4)-BBN(7-14)-AuNP in prostate tumour cells and over 50% in colon carcinoma cells. Biodistribution in NU/J mice highlighted a three-fold uptake increase in tumours at 30 min post-injection of 68Ga-DOTA-NT-AuNP and 68Ga-DOTA-PEG(4)-BBN(7-14)-AuNP compared to 68Ga-DOTA-NT and 68Ga-DOTA-PEG(4)-BBN(7-14) respectively, therewith fast distribution in prostate and colon tumours and minimum accumulation in non-targeted tissues.

Calcium alginate (CaAlg) beads were prepared using ultrasound for use in the removal of lead from natural and wastewaters by ion exchange. Ultrasound was applied in a batch mode with an ultrasonic bath or in a flow mode using an ultrasonic clamp-on device. For comparison purposes the synthesis was performed in batch mode in the absence of the ultrasound. The beads prepared using ultrasound showed a greater ion exchange capability which could be ascribed to a larger specific surface area as a result of surface roughening induced by cavitation. Scanning Electron Microscopy (SEM) images revealed that the roughening was in the form of corrugation for the product with the best ion exchange capability obtained in the flow process where preformed CaAlg droplets were subjected to ultrasound during the setting process. These beads performed 11% better for lead removal than those synthesized in the absence of ultrasound.

Bioethanol is the world’s leader biofuel and it is produced by fermentation from glucose feedstocks. The fermentation rate is quite low and any method of increasing the reaction rate is welcome. The main goal of our research is to identify the domain for microwave Specific Absorption Ratio (SAR) which leads to an increase in fermentation rate of Saccharomyces cerevisiae without affecting its viability. For this purpose, an installation was setup which allows for glucose fermentation to be carried out in the presence of microwave, with good control on SAR and on temperature of the fermentative medium. An optimum SAR domain, between 15 and 25 W kg−1, was determined, in which a significant boost of glucose fermentation manifests, with an increase in fermentation rates of up to 20%. Based on the observations made through electron and optical microscopy on cell growth and viability, we have noticed that microwave irradiation favours ethanol production of the cells, against their growth.

Glycerol acetals/ketals and their esters, produced from renewable raw materials, are highly valuable compounds, being used as oxygenated fuel additives and ecological solvents. A new method for obtaining glycerol acetal/ketal esters, difficult to synthesize using classical techniques, was developed. This method is based on the reversible reaction of 1,2-O-isopropylidene-glycerol esters (IPGEs) obtained from glycerin, by-product from biodiesel production, with low volatility aldehydes/ketones (e.g. furfural and ethyl levulinate, both obtained from lignocellulosic biomass), in the presence of a heterogeneous acid catalyst. To circumvent reaching equilibrium, the continuous removal of acetone (Ac) from the reaction mixture was done, the former being reused in the synthesis of IPGEs. The method viability was assessed by synthesis and characterization of eight new compounds from two classes: furfurylideneglycerol esters (FGEs) and ethyl levulinate glycerol ketal esters (ELGKEs). A detailed kinetic study was done throughout an experimental program, first developed in Asia 330, a modular range flow chemistry system, then in a continuous-flow process at micropilot scale.

Silver is one of the eight precious metals, along with gold and the six platinum-group metals (PGM). Most silver is obtained as a by-product of mining and refining of other metals. Fine silver is produced in electrolytic processes, using silver anodes (electrolytic refining) or inert ones (electrowinning) and an acidified silver nitrate electrolyte. Because the standards for refined silver are very high, it is necessary to control the behaviour of the impurities. Depending on the refining process parameters, it is not uncommon to find precious metals, such as palladium, platinum or even gold, dissolved in the electrolyte. In particular, palladium is very challenging because of its standard oxidation–reduction potential similar to the one of silver . The recovery of palladium and platinum from the silver refining processes is important for two reasons: to produce high quality silver and to recover the valuable precious metals. In this work, Pd and to a lesser extent Pt recovery from a silver nitrate effluent was investigated using a phosphine oxide – bearing coordinating resin (MPX-310). Laboratory scale studies, in batch and continuous modes, have shown the ability of MPX-310 to capture Pd and Pt from a matrix highly concentrated in Ag (up to 131 g l−1) and Cu (up to 70 g l−1) from industrial effluents. Moreover, adiabatic calorimetry studies were performed in order to determine the reactivity of the resin in the silver nitrate effluent and the optimal conditions where this resin can be safely used in an industrial process. Pilot scale experiments were done and the results obtained in the laboratory were confirmed.

Microwave assisted extraction is a powerful tool for natural compounds extraction from plants. The main goal of our research is to obtain a maximum extraction yield without affecting the chemical structure of the valuable natural compounds. In order to avoid the degradation of the latter, a special equipment has been developed. This equipment allows microwave heating using a slot end coaxial antenna into a microwave applicator provided with an efficient cooling system. Consequently, a high specific absorption rate (SAR) is achieved at low temperatures. A slightly non-uniform heating was observed at lower stirring rates that represents an advantage for the extraction process, keeping the extracted product without any degradation. Using this equipment, polyphenols were extracted from sea buckthorn leaves. For these extracts, total polyphenol content, chemical composition, and antioxidant capacity were determined. The extracts obtained by this procedure present higher polyphenol content with a higher antioxidant capacity than those obtained by conventional methods performed at the same temperature profile and in the same extraction cell.

A reactive extraction/back-extraction process was studied experimentally in a two-stage column. The mathematical model of the reactive extraction using a closed loop moving organic liquid membrane, based upon first principle equations, was derived as a set of Partial/Ordinary Differential Algebraic Equations (P/ODAE). The mathematical model, reduced through orthogonal collocation to a system of ODAE, was solved using a self-adaptive Runge-Kutta (RK)-type method. The mathematical model was calibrated using own batch experimental data and a modified genetic algorithm as optimizer.

The application of biopolymer-based sorbents in solving some environmental problems such as the removal and recovery of heavy metals from natural polluted water and wastewater has received lately a lot of attention due to their unique characteristics. The fundamental properties that recommend the usage of biopolymers-based sorbents for environmental remediation are: high selectivity and sorption capacity, renewability, safe manipulation, sorption capacity increase through simple physical and chemical methods, easy separation from treated water, and easy regeneration and reuse for repetitive sorption-desorption cycles. Accordingly, this research study has as purpose to present the results related to the usage of two types of alginate sorbents (calcium alginate and chitosan coated calcium alginate) in four repetitive lead(II) ions sorption-desorption cycles and to examine the influence of desorption agents on structural sorbent�s characteristics. The results obtained showed that both calcium alginate and chitosan coated calcium alginate are good stable sorbents to be used in lead(II) ions sorption-desorption cycles.

The mathematical modeling of the phenomena taking place during the electron beam flue gas treatment is a complex endeavor due to the different time scales of the processes occurring as accelerated electrons are bombarding the flue gas. The paper presents a complex kinetic model for these gas phase interactions, consisting of 1034 chemical reactions with the participation of 115 reactive species. The mathematical model couples the complex gas phase kinetics with a liquid phase kinetic model, taking into account the nucleation and condensation phenomena occurring due to the presence of sulfuric acid. The modeling results for both coupled and uncoupled gas phase kinetics are validated against a set of literature experimental data with satisfactory outcome. The work aims to identify the most important chemical reactions influencing the pollutants removal, proposing a sensitivity analysis using the concept of generated entropy. To the best of the authors’ knowledge a sensitivity analysis of this extent has not been performed for the electron beam flue gas treatment. The results of this analysis emphasize the link between the removal efficiencies of NO x and SO 2 , the importance of hydroxyl radicals and can aid in future model reduction efforts.

The aim of this work was the development and validation of a fast analytical method to determine the residual solvents content in radiopharmaceuticals such as: 18F-Fluorodeoxyglucose (18F-FDG), 18F-Fluoroestradiol (18F-FES), 18F-Fluorothymidine (18F-FLT),18F-Fluoromisonidazole (18F-FMISO). Radiopharmaceuticals are radioactive preparations for medical purposes used in nuclear medicine as tracers in diagnostic imaging and treatment of certain diseases. Positron Emission Tomography (PET) is a medical imaging technique that consists in introducing into the body of a small amount of a biologically active chemical compound labelled with a short lived positron-emitting radioisotope (18F, 11C, 68Ga). Residual solvents are critical impurities in radiopharmaceuticals that can affect labelling, stability and physicochemical properties of drugs. Therefore, the determination of these solvents is essential for quality control of radiopharmaceuticals. Validation of the control method for residual solvents by gas chromatography is referred by the European Pharmacopoeia using a special injection technique (head space). The parameters of the method, which comply with International Conference on Harmonization guidelines, are: accuracy, precision, linearity, limit of detection, limit of quantification and robustness. The proposed method (direct gas chromatography injection) proved to be linear, precise, accurate and robust. Good linearity was achieved for all the solvents and correlation coefficients (R2) for each residual solvent were found more than 0.99.

This research study deals with lead(II)/Pb 2 + removal from aqueous solutions by calcium alginate (CA) and chitosan coated calcium alginate (CCCA) as adsorbents, in batch experiments. A simple synthesis method was used to prepare both adsorbent materials. CA and CCCA were characterized using infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis (TG). The main parameters determining the quantity of lead(II) ions adsorbed are: the initial pH solution, the lead(II)ions initial concentration and the temperature. The experiments revealed that the adsorption capacity, thus, the removal efficiency are higher for CCCA compared to CA. The adsorption of lead(II) ions onto both CA and CCCA materials is an endothermic spontaneous process, as resulted from the thermodynamic experiments. Consequently, a moderate increase of temperature improves the adsorption capacity. The thermodynamic equilibrium sorption experimental data are well fitted by Freundlich adsorption isotherm for both tested adsorbents, better than Langmuir's. Accordingly, lead(II) ions adsorption onto CA and CCCA develops obeying a multilayer mechanism. The kinetic experimental data were fitted by both pseudo-first, and pseudo-second order models. The former approaches better the experimental results for both adsorbents. The mechanism involved in lead removal is a combination between ion-exchange and coordination/chelation based on experimental results.

An enhanced partition model is proposed for the distribution of 4-nitrophenol between polar quasi-immiscible solvents (water and 1-octanol). Monitoring both phases over an extend wavelengths range (200–450 nm), the presence of 4-nitrophenol and 4-nitrophenolate species in the aqueous and organic layers was emphasized. A genetic algorithm has been used to minimize the sum of squared residuals model-experiment using the non-linear equations system model resulted from mass and charge balances. Thus, improved values for the thermodynamic constants associated to partition, dissociation and dimerization equilibria occurring in both phases were found: 1-octanol dissociation constant in the aqueous phase, KOw = 3.2 × 10−13 mol∙L−1, 4-nitrophenol dissociation constant in aqueous phase, KΦw = 1.45 × 10−8 mol∙L−1, water dissociation constant in the organic phase, Kwo = 3.5 × 10−16 mol∙L−1, 1-octanol dissociation constant in the organic phase, KOo = 1.1 × 10−16 mol∙L−1, 4-nitrophenol dissociation constant in organic phase, KΦo = 2.9 × 10−10mol∙L−1, 1-octanol dimerization constant in the organic phase, KDo = 3 × 10−9 L∙mol−1 and 4-nitrophenol dimerization constant in organic phase, KDΦ = 1.4 × 10−8 L∙mol−1. Although the logarithms of calculated partition coefficients are rather similar to the values reported in the literature, in the 1.86–2.07 range, the collected experimental evidence demonstrates that the process had been oversimplified and the polar characteristics of the organic solvent had been neglected in the former studies. The enhanced partition model emphasized the nonlinear dependency of the partition coefficient upon the analyte concentrations.

Intermediates for synthetic paraffinic kerosene with structures of fatty acid methyl ester (FAME), were synthesized from algal oil extracted from Nannochloris sp. biomass. Microalgae were grown under mixotrophic conditions to improve biomass production, using glycerin as additional source of organic carbon, by-product in FAME obtaining process. Microalgae were supplementary stressed to increase the lipid productivity, by reducing the inorganic nitrogen and partially replacing it with organic nitrogen (hydrolyzed proteins from the same microalgae). Since algal oil has high free fatty acids (FFA) content, a two-step process for FAME synthesis was necessary. In the first step, FFA was esterified with methanol over SO 4 2− /TiO 2 –La 2 O 3 solid acid catalyst. The second step, i.e. methanolysis of pre-treated oil, was performed over Na 2 SiO 3 /Mg–Al-hydrotalcite (Na 2 SiO 3 /Mg–Al-HTC) heterogeneous base catalyst. The Na 2 SiO 3 /Mg–Al-HTC catalyst was synthesized and then characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), textural analysis (BET method), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence analysis (EDXRF) and Fourier transform infrared (FTIR) spectroscopy. The influences of catalyst loading and stability, methanol-to-oil molar ratio and the reaction time on the FAME yield were carefully studied. FAME producing technology was investigated first in batch and then in a continuous flow process.

Calcium alginate (CaAlg) beads were prepared using ultrasound for use in the removal of lead from natural and wastewaters by ion exchange. Ultrasound was applied in a batch mode with an ultrasonic bath or in a flow mode using an ultrasonic clamp-on device. For comparison purposes the synthesis was performed in batch mode in the absence of the ultrasound. The beads prepared using ultrasound showed a greater ion exchange capability which could be ascribed to a larger specific surface area as a result of surface roughening induced by cavitation. Scanning Electron Microscopy (SEM) images revealed that the roughening was in the form of corrugation for the product with the best ion exchange capability obtained in the flow process where preformed CaAlg droplets were subjected to ultrasound during the setting process. These beads performed 11% better for lead removal than those synthesized in the absence of ultrasound.

Nowadays, the concerns regarding cadmium pollution increased steadily, due to its serious damages to the environment and human health. Consequently, stringent limits have been set for this heavy metal ion both in industrial and drinking water. Numerous traditional and unconventional methods were applied to reach these limits. In this paper, two phosphine oxide/phosphine oxide and thiourea chelating resins MPX-310 and MPX-317 produced by Magpie Polymers - Italmatch Chemicals, Italy were comparatively evaluated with a commercial thiourea chelating resin Lewatit® MonoPlus TP 214 produced by Lanxess regarding Cd(II) removal from aqueous synthetic solutions. The physicochemical properties of the resins were studied by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TG-DSC) and X-ray Photoelectron Spectroscopy (XPS). Batch tests have been performed to assess the performance of these resins in Cd(II) removal. A value of 3–4 for pH and 600 min of contact time were determined as optimal parameters for the removal process. The experimental results also showed that the Lewatit® MonoPlus TP 214 has a higher removal capacity than MPX-317 and MPX-310 due to the presence of the thiourea and ion-exchange functional groups on the Lewatit® MonoPlus TP 214 backbone, compared with the presence of the phosphine oxide functional groups on the MPX-310 and thiourea and phosphine oxide on MPX-317. A monolayer adsorption on the homogenous adsorbent surface mechanism involved in Cd(II) removal was pointed out by the results regarding adsorption isotherms. The best fit of the pseudo-second kinetic model indicates that the sorption process goes through a mechanism that involves chemical reaction between Cd(II) and functional groups grafted on the resin's backbone. The chelating capacity of the tested resins showed that they are suitable for Cd(II) removal from aqueous synthetic solutions and industrial wastewater.

F-FDG is a glucose analog in which the hydroxyl group on the second carbon is substituted with 18 F, being used as an indicator of glucose uptake and cell viability. The aim of this work was to synthesize the 18 F-FDG and to validate the methodology for the assessment of its both radiochemical and chemical purities, according to the European Pharmacopoeia. The proposed methodology encompasses three chromatographic methods: radio-HPLC, radio-TLC and HS/GC. Radiochemical impurities may originate from radionuclide production, incomplete purification and radiolysis after synthesis. Chromatographic methods should effectively separate these species, as radioactive impurities can affect the clinical outcome of positron emission tomography imaging studies because of nonspecific uptake. Chemical impurities, on the other hand, can affect nucleophilic substitution mechanism. Keeping these contaminants at as low concentrations as possible is the key of a successful synthesis. Therefore, the determination of both type of impurities in short time is an essential step in characterizing of each batch

This work addresses the selective recovery of platinum group metals (PGMs) from aqueous streams, a critical issue within the recycling and metal refining industries aiming to lose zero of the value contained. Herein, selective PGM capture was investigated using three metal-capturing polymeric resins from different manufacturers: a special anion exchanger (Dow), an S-containing chelating resin (Lanxess), and a phosphine oxide containing coordinating resin (Magpie Polymers). The relative affinity of these different materials for the PGMs, as well as copper, was compared under various conditions. It was found that the phosphine oxide based material was the most suitable for the selective capture of PGMs from an oxidizing solution containing high concentrations of copper and counterions. Theoretical calculations using density functional theory (DFT) have shown that the most likely binding of PGMs to this material is a bidentate coordination via the phosphine oxide groups.

The treatment of flue gases with high energy electron beams for the abatement of sulfur and nitrogen oxides has been developed as an alternative to the more traditional methods of treating atmospheric pollutants (i.e. wet gas desulfurization, selective catalytic reduction). This paper proposes a new mathematical model for the complex phenomena occurring in both gas and liquid phases during the irradiation treatment, using a relatively large reaction system for the gas phase (40 chemical species and 90 chemical reactions). The continuous formation of the liquid dispersed phase is taken into account, considering it in thermodynamic equilibrium with the gas phase and neglecting the mass transfer resistances on both sides. By introducing a new approach in modeling the gas–liquid absorption phenomena (solubility based instead of Henry’s law) the mathematical model is able to predict in a more accurate manner the distribution of species between the two phases. The developed mathematical model is based on the assumption that the radiochemical yield varies inversely proportional to the magnitude of the irradiation dose employed, till a threshold value. The paper also investigates and discusses the model’s sensitivity to the operating parameters (irradiation dose, flue gas humidity, initial pollutant concentration, temperature and ammonia content). The modeling results are in good agreement with the experimental findings performed in the range of 58–62 °C, with a slight deprecation out of this range, exhibiting a mean relative deviation of 9.7 % in the case of the removal efficiency for NO and 5 % for SO2.

Feed spacers and hydrodynamics have been found relevant for the impact of biofouling on performance in reverse osmosis (RO) and nanofiltration (NF) membrane systems. The objectives of this study on biofouling development were to determine the impact of (i) linear flow velocity and bacterial cell load, (ii) biomass location and (iii) various feed spacer geometries as applied in practice as well as a modified geometry spacer. A three-dimensional mathematical model for biofouling of feed spacer channels including hydrodynamics, solute mass transport and biofilm formation was developed in COMSOL Multiphysics and MATLAB software. Results of this study indicate that the feed channel pressure drop increase caused by biofilm formation can be reduced by using thicker and/or modified feed spacer geometry and/or a lower flow rate in the feed channel. The increase of feed channel pressure drop by biomass accumulation is shown to be strongly influenced by the location of biomass. Results of numerical simulations are in satisfactory agreement with experimental data, indicating that this micro-scale mechanistic model is representative for practice. The developed model can help to understand better the biofouling process of spiral-wound RO and NF membrane systems and to develop strategies to reduce and control biofouling.

The waste resulted from fish processing industries are discarded into the environment around the world, causing environmental pollution. The main problem of fish oil extracted from waste is the high content in free fatty acids (FFA) which decrease the yield in fatty acids esters during transesterification reactions. Therefore, to correct the fish-oil properties, a new environmentally friendly heterogeneous superacid catalyst (SO42-/SnO2-ZrO2) was tested in the esterification reaction of FFA with ethanol. The catalyst was characterized by different techniques (XRD, FT-IR, FT-IR of adsorbed pyridine, BET, SEM-EDX, TGA and acidity measurements). The reaction was found to follow a Langmuir-Hinshelwood (L-H) dual-site mechanism with the novelty that both Bronsted and Lewis acid centers participate equally in the esterification reaction. The pre-treated oil was subjected to transesterification reaction with ethanol over a heterogeneous base catalyst and then, the saturated and unsaturated fractions of fatty acid ethyl esters (FAEE) were separated using a vacuum rectification unit with falling film. The saturated content can be used as biofuel, while the unsaturated FAEE are further transesterified with glycerol in order to obtain oil with high content in polyunsaturated fatty acids (PUFA). A detailed study of the intrinsic kinetic process at the surface of the superacid catalyst and a thorough mathematical model of the fixed bed reactor were written and validated by an experimental program, designed according to the D-optimal methodology.

The synthesis of TiO2 was studied in an original hydrothermal process that uses triethanolamine titanium complex Ti(TeoaH)2 as a Ti precursor and triethanolamine (TeoaH3) as a shape controller to obtain bipyramidal anatase nanoparticles. Backed-up by experimental evidence, i.e., time profiles for Ti(IV) species concentrations together with crystal shape and particle size distributions measured by dynamic light scattering and electron microscopy, a mathematical model was built. The model includes chemical reactions responsible for TiO2 generation in solution and the subsequent anatase nucleation and crystal growth. The oriented attachment mechanism was adopted to explain the build-up of crystals with equilibrium anatase structure (Wulff structure) and time-varying shape factor. This complex mathematical model was solved writing and validating an in-house software using the Matlab (Natick, MA, USA) environment. The process was simulated for a batch time of 50 h, and the results, in terms of main species con...

Isothiocyanates (ITCs) derived from plants of the order Brassicales are known for their antibacterial, anti-inflammatory or anticarcinogenic potential. Although only the free ITCs exert bioactivity, quantification in vivo is almost exclusively performed on total ITC/metabolite content. We therefore investigated in a pilot study the amount of free ITC at different steps critical for therapeutic efficacy. A sensitive and specific GC–MS/MS method for the simultaneous quantification of individual free ITC after solid-phase extraction (SPE) was developed. We show here that release of biologically active ITC from plants occurs at not only alkaline but also acidic pH. Furthermore, in human urine conversion of the ultimate, inactive mercapturic acid conjugate back into its corresponding bioactive form is increased at alkaline as compared to neutral pH. This was also observed in the urine of human volunteers, where – in correlation with the pH value – a mean of 0.16 to 1.03 μmol ITC was detected after oral application of a phytotherapeutic agent containing 30.4 μmol of the initial pro-drugs. The amounts of free ITC being necessary for bioactivity in vitro were found to be indeed achieved in vivo. These data might be helpful to better understand the beneficial effects of ITC observed in vivo.

Pareto optimization approach was used in searching for the particular successions of topologies and operating conditions for a semicontinuous water network (batch with respect to the raw materials) that minimize both the freshwater consumption and the investment and operating costs. The semicontinuous wastewater network (SWN) formed of N water-using units (WUs), each handling at most K contaminants, and one storage tank (ST) is optimized on time intervals by increasing the wastewater reuse opportunities. A single freshwater source is available and later a regeneration unit (RU) is added to the network as a fine-tuning tool in the Pareto optimization, and further its influence is discussed. The WUs are ordered simultaneously by schedule and by maximum allowable outlet concentrations of contaminants. Thus, the rules concerning the internal reuse between the overlapping WUs correspond to an oriented graph: no recycle is allowed against the ordered sequence. The differential-algebraic equations model consisting in a set of differential equations for the ST and a nonlinear system mass balance equations with restrictions for the overlapping WUs is optimized using the Matlab built in functions for both the genetic algorithms (GA) and the RK-type integrator. The topology of the SWN changes for each time interval, its optimal structure depending upon the minimum freshwater consumption and the costs. A complex synthetic case study was subjected to optimization, and several scenarios are analyzed.

The residence time distribution (RTD) approach was used to characterize the flow and mixing behavior of burners. This analysis consists of injecting an inert gaseous tracer into the feed and measuring its change in concentration at various detection points. The responses are then used to characterize the flow behavior and, thus, the local mixing in the space delimited by the injection and probe points. The outcome of this RTD analysis is a flow model that, combined with an appropriate kinetics, constitutes an efficient tool in examining the ways to reduce NOx emissions in existing installations. A replica made in plastic at a 1:1 scale of an industrial gas burner was used for cold experiments. As preliminary information, a chart of local mixing in the axial section of the burner chamber was obtained. Even though far from working conditions, cold experiments are beneficial because they reveal the existence of possible major flow disturbances, leading to imperfect or incomplete combustion, a source of NOx.

Bacterial populations conditionally display non-linear dynamic behaviour in bioreactors with steady inputs, which is often attributed to varying habitat conditions or shifting intracellular metabolic activity. However, mathematical modelling has predicted that such dynamics also might simply result from staggered birth, growth, and death events of groups of cells within the population, causing density oscillations and the cycling of live and dead cells within the system. To assess this prediction, laboratory experiments were performed on Escherichia coli strain K12-MG1655 grown in chemostats to first define fine-scale population dynamics over time (minutes) and then determine whether the dynamics correlate with live–dead cell cycles in the system. E. coli populations displayed consistent oscillatory behaviour in all experiments. However, close synchronisation between OD600 and live–dead cell oscillations (within ~33–38 min cycles) only became statistically significant (p

A water network (WN) for a batch process could be seen as a dynamic structure which changes its topology at fixed time intervals delimited by events. During each time interval, the WN could be abst...

The optimization of an integrated network of water-using (WU) and treatment (TU) units is addressed in this paper, by targeting for maximum treated water reuse as a considerably better alternative to fresh water consumption. An optimal integrated water network (WN) is an oriented graph, starting with inlet contaminant free WUs and then the other WUs ranked by a certain criteria. The outlet wastewater streams are either split to be reused by the next WUs in sequence or sent to treatment. The mathematical model of the integrated WN is based upon total and contaminant species mass balances for each and every WU/TU which is restricted with respect to the inlet and outlet contaminant concentrations. The performance of the approach is tested on a synthetic example. Several scenarios were used, the results being analyzed in connection with the reduction of fresh water consumption and the increase of internal and treated water reuse.