Abstract The dynamics of rising bubbles in a liquid sodium pool plays a significant role in the estimation of the radiological source term during anticipated transients and normal operation of a fast reactor. Sodium is chemically reactive with air and water. Therefore, carrying out experiments using sodium on a reactor scale level requires extra precautions. We report an in-house experimental technique to depict the bubble dynamics along with numerical support to establish similarity behavior between water and liquid sodium, to reduce the number of experiments in sodium systems for in-depth knowledge of bubble dynamics in the case of the fast breeder reactor. In the present work, 3-D bubble dynamics is studied in the OpenFOAM platform and the validated numerical model is used to study bubble dynamics in sodium to establish similitude between the water and sodium systems. The bubble aspect ratio of 0.9 cm diameter bubbles in the sodium system is found to be in close agreement with that of 0.5 cm bubbles in the water system. Experimental and numerical findings suggest similarity of the aspect ratio between water and scaled-up sodium systems. The similarity criteria established between water and sodium are found to be very useful in conducting water-based experiments to study bubble dynamics in sodium systems.

Abstract This study reports a synthesis of copper nanoparticles (CuNP) deposited on polyethylene terephthalate (PET) filters and antibacterial evaluation of the obtained filters against Escherichia coli and Salmonella enterica. CuNP were synthesized by a two-step method involving adsorption of [Cu(OH)4]2- ions onto a PET filter and subsequent chemical reduction by ascorbic acid without using other capping agents. The synthesized CuNP were 105±26 nm (mean±SD) in size and agglomerated into clusters on the PET fibres. Increasing the immersion time of the filters in [Cu(OH)4]2- solutions yielded higher amounts of deposited CuNP. SEM images and mass measurements revealed significant changes in the PET fibre surface under the alkaline medium. Passing bacterial suspensions of E. coli and S. enterica through the CuNP-deposited PET filter reduced them by 5.55 and 2.30 log values, respectively. This method of depositing CuNP onto PET material may be further developed for a wide scope of applications, not only in antibacterial filters, but also in catalytic, packaging and biomedical fields.

Abstract In the present work, the impacts of effective parameters on the mixing of Stokes flows in a chaotic batch mixer are numerically and experimentally studied. The batch mixer consists of a container and two circular rotors where the rotors can rotate independently. To investigate the possibility of improving the mixing, the effect of non-constant speeds, contra-rotating rotors, and varying rotor speeds are studied. The results showed that varying the rotor speed while rotating in the same direction does not significantly increase mixing. However, if the rotors rotate in opposite directions, 10-times more mixing is achieved compared to the mode of rotating in the same direction. Nevertheless, given the constant speed of rotors, the flow is steady since the fluid particles have periodic movements in secondary flows, but the flow becomes chaotic and mixing is considerably increased by applying sinusoidal perturbations to the rotor speed. Nevertheless, for both modes of rotations in the same and opposite directions, the chaotic flow leads to increased mixing index in the same amount of time. Based on results, the best mixing results are achieved when the rotors rotate with sinusoidal rotational speed in opposite directions.

Abstract The selective separation of Mn(II) and Cd(II) as well as regeneration of the complexing agent were conducted by shear induced dissociation coupling with ultrafiltration (SID-UF), and the copolymer of maleic acid and acrylic acid (PMA) was used as complexing agent. At the optimal complexation conditions, pH 6 and P/M (mass ratio of polymer to metal ions) 9, both the rejections of Mn(II) and Cd(II) arrived at more than 99%. The shear stabilities of two PMA-metal complexes at different pHs were particularly investigated using rotating disk membrane and the results indicated that critical shear rates γ c of PMA-Mn complex were lower than that of PMA-Cd at the same pH. According to the difference of the shear stabilities between PMA-Mn and PMA-Cd complexes, the selective separation of Mn(II) and Cd(II) were achieved by SID-UF at 1450 rpm and 1600 rpm, and PMA was regenerated.

Abstract Coke formation inside radiant coils is one of the main problems during thermal cracking of hydrocarbons. The on-line preparation of the coating for coking inhibition is a promising technology because it provides more flexibility to the operators on site. The SiO2/S coating was prepared on the inner surface of coils in an 8-year-served GK-VI industrial cracking furnace. The effects of the coating preparation process on the operation of TLE were studied. The coking rates of the tube with and without coating preparation were evaluated by the trend change of tube metal temperature. Simulations of the coating deposition process were further carried out using the computational fluid dynamics approach. The results showed that a significant temperature increase at the outlets of TLEs during coating preparation were due to the accumulation of SiO2 and S in a loose form under the TLE operating conditions when the concentration of coating precursors was 7500 ppm (wt. %). In the three tests, coating precursors were mainly completely consumed in tubes and TLEs. For the coated tube, the run time was extended by 4-7 days because the catalytic coking was decreased. No significant changes in the distribution of products and molar yields of main products were observed. In the simulations, it was found that increasing the inlet flow rate led to a more uniform thickness and improved the mass content of sulfur in the coating. In the tube bend section, circumferential nonuniformities for the deposition were due to circumferential differences in the temperatures and mass fractions. The mass fraction of S in the coating was within the range of 0.02%-0.1%. The control step for the SiO2/S coating deposition was kinetic. Based on the simulation results, the optimized coating preparation parameters were determined, i.e., the inlet flow rate of 15t/h, the outlet temperature of 1093K and the inlet mass concentration of 3000 ppm (wt. %).

Abstract Solanum viarum Dunal belongs to the Solanaceae family and it is considered to be a grazing weed toxic to cattle. In this study, ultrasound-assisted extraction (UAE) and supercritical CO2 extraction (SFE-CO2) were applied to evaluate the extraction yield and chemical composition of fruits and roots matrices of Solanum viarum Dunal. A hydroalcoholic solution (60% ethanol/40% water, v/v) was the solvent used for UAE. For comparisons, extractions with Soxhlet and maceration were carried out. For SFE-CO2, the highest yield was obtained at 60°C and 250 bar. For UAE, the highest yield was obtained at an ultrasound intensity of 75.11 W/cm2 and pulse cycle of 0.93. The techniques seem to be efficient for the extraction of chemical compounds, indicating a large number of bioactive compounds. The major compounds are 1,2-benzenedicarboxylic acid, quinic acid, octadecenoic acid, and solasodine. The results highlight the application of UAE to recover compounds from vegetal matrices, since it presented higher yields and more chemical constituents when compared with other techniques.

Abstract Cantilever nanobiosensors have emerged as an alternative to conventional methods of analysis to monitor heavy metals, which are being highlighted by detecting substances at the micro and nanoscale through the use of sensor layers. In the present study, a new cantilever nanobiosensor was developed functionalized with urease enzyme by self-assembled monolayers for the detection of heavy metals (lead, nickel, cadmium, zinc, cobalt, and aluminum) in water. From the calibration curves, using the statistical method of Principal Component Analysis, it was possible to observe that the nanobiosensor was highly efficient in heavy metal discrimination. The nanobiosensor presented high sensitivity, good stability, and a detection limit in the ppb range during 30 days of storage. The surface characterization by scanning electron microscopy confirmed the cantilever functionalization and the sensing layer deposition. The cantilever nanobiosensor designs based on tensile surface stress measured by changes in voltage suggest the proposed mechanism of the adsorption of heavy metal by the urease enzyme. Thus, the cantilever nanobiosensor with urease enzyme was able to detect heavy metals in water and could be a promising tool for heavy metal detection.

Abstract In order to improve the adsorption capacity and selectivity of CO2/CH4 and CO2/N2, we have functionalized multi-walled carbon nanotubes (MWCNT) with 3-aminopropyltriethoxysilane (APTES). The functionalized MWCNT was characterized by Fourier transform infrared (FT-IR), energy dispersive X-ray spectroscopy (EDX) and BET analysis. CO2, CH4 and N2 adsorption at two different temperatures and P < 5 bar on the functionalized MWCNTs was investigated by the volumetric method. The selectivity of the functionalized MWCNTs for CO2/CH4 and CO2/N2 was studied and compared with MWCNTs. The functionalized MWCNTs show higher adsorption capacity of CO2 and selectivity of CO2/CH4 and CO2/N2 in comparison with the MWCNTs at different pressures. The highest CO2/CH4 and CO2/N2 selectivities for the functionalized MWCNTs were 6.78 and 26.14, respectively, at a pressure of 0.2 bar and at 298 K. Two of the most common adsorption models, the Langmuir and Sips isotherms, were used to correlate the experimental data of CO2 and CH4 adsorption on the adsorbents. The results confirm that the functionalized MWCNTs are promising materials for the separation and purification of gases.

Abstract The performance of a flat sheet polyamide nanofiltration membrane in rejection of a binary mixture of heat stable salts (acetate and sulfate) from methyl-diethanolamine (MDEA) solution was investigated. The effects of pressure and concentration of MDEA solution on rejection of acetate and sulfate ions were studied. At MDEA concentration of 20% wt. and pressure of 70 bar, 80% and 98% rejection can be obtained for acetate and sulfate ions, respectively. Membrane performance and transport coefficients were investigated using the Spiegler-Kedem-Katchalsky (SKK) model, film theory and extended Nernst-Planck (FT-ENP) model. The results of the FT-ENP model show accurate agreement with experimental results. This result can be obtained due to considering the charge repulsion of sulfate ions. For sulfate ions, both models show errors less than 1% with >R2=0.98. In the case of acetate, errors less than 3% (>R2=0.75) and 2% (>R2=0.89) were obtained for the SKK and FT-ENP models, respectively.

Abstract Oil recovery, retention index, and thermodynamic parameters of green coffee beans (GCB) and its press cake (PC) extraction using bio-based solvents were investigated. The extraction parameters investigated were temperature (35 to 55 °C), type of material (coffee beans and press cake), and type of solvent (ethanol, acetone, and ethyl acetate), at a fixed solvent to solid mass ratio (5:1) (w/w). The fatty acid profile of the ethanolic extract was assessed for both GCB and PC, and compared to the oil obtained from the mechanical pressing. It was observed that higher temperatures affected positively the extraction yields, especially when acetone and ethanol were employed, allowing a recovery up to 90% and 56.7% for GCB and PC, respectively. The solution retained in the raffinate phase from the GCB extraction was greater than that for the PC. For all operational levels, the ∆H and ∆S were positive. ∆G decreased with increasing temperature. Palmitic and linoleic acids were predominant in all types of oil. The oil obtained by pressing showed higher content of linoleic acid (45.32%), while the solvent-extracted oil from GCB had more palmitic acid (34.79%), and the PC oil presented intermediate levels of all the methyl esters.

Abstract Silica spheres coated with titania (SiO2@TiO2) were synthesized using chitosan as template. The N2 adsorption/desorption isotherms of the spheres point to meso and macroporous characteristics and the elemental mapping by EDS shows uniform distribution of Ti on the surface of the silica spheres, leading to formation of an amorphous structure (XRD). The results from the model reaction of photocatalytic degradation of methylene blue (MB) show a good stability of the spheres regarding their reuse. The tests with various additives pointed to hydroxyl radical production as the main via of MB degradation. The photocatalytic activity of the spheres in the hydroxylation of benzene to form phenol, hydroquinone and benzoquinone was assessed. The kinetic data point to the formation of phenol as the limiting step; in addition, the phenol consumption occurs by parallel and consecutive reactions producing benzoquinone.

Abstract Colloidal silica is an important biocompatible, inert and non-toxic material for imaging, therapy, and drug delivery biomedical applications. In this context, the evaluation of colloidal suspensions and their stabilities by a Fiber Optic Quasi-Elastic Light Scattering sensor is proposed. Two different silica nanoparticles were prepared and characterized by scanning electron microscopy and X-ray diffraction, being completely amorphous, with mean diameters of 125 and 159 nm and average specific weight of 1.94 g.cm-3. The nanoparticles were dispersed in deionized water in different concentrations ranging from 0 to 2% (m/m), resulting in suspensions with mean kinematic viscosity of 0.009157 cm².s-1. The sensor showed different sensitivities regarding concentrations and diameters, with an increase in the light intensity dispersion caused by the scattering. A decreasing tendency of the decay rate of the autocorrelation function of the light intensity signal was verified with the variation of pH, and this decay rate also showed an abrupt decrease with the enhancement of the ionic strength, detecting the limits of the colloidal stability. This work presents a simple and reliable methodology for the colloidal assessment in a low-cost and minimally invasive way, easily extendable for different chemical and biological systems.

Abstract We investigated the immobilization of a tetrameric Kluyveromyces lactis β-galactosidase (EC: 3.2.1.23) (KL-Gal) on Immobead 150 using different support modification strategies. Immobead support was modified using an acid solution of H2SO4:HNO3 (3:1) (Immobead-Ac) or 5 % (v/v) glutaraldehyde (Immobead-Glu). Its unmodified form (Immobead) was also tested. Immobilization yields and efficiencies were evaluated by testing protein loads from 10 to 200 mg.g-1 support. The thermal, physico-chemical, textural and catalytic properties of the supports (modified and unmodified) and their derivatives (Immobead-KL-Gal, Immobead-Ac-KL-Gal and Immobead-Glu-KL-Gal) were analyzed. The highest immobilization yields and efficiencies were achieved with a protein load of 100 mg.g-1 support. Surface and pore areas of the Immobead support were greatly decreased after modification. Michaelis constant of the immobilized β-galactosidase increased in the derivatives. Maximum velocity decreased approximately 2.8 times for Immobead-KL-Gal and Immobead-Glu-KL-Gal, and approximately 1.4 times for Immobead-Ac-KL-Gal. In batch processes, the three derivatives could be reused successfully at least 15 times, maintaining high residual enzymatic activity during the lactose hydrolysis (in both cheese whey and milk). The tetrameric K. lactis β-galactosidase immobilized on Immobead supports via the tested treatments was stabilized and is an alternative tool for lactose hydrolysis in the dairy industry.

Abstract A liquid-liquid hydrocyclone, so-called de-oiling equipment, was investigated for separation of oil droplets and wastewater in an Iranian petroleum unit. To generate the geometry and the mesh of the hydrocyclone Gambit software was used. Afterwards, by taking advantage of the Euler-Lagrangian principle, the governing equations covering the motion of fluid and that of particles in the hydrocyclone were solved. Initially, it was shown that the outcomes of CFD are in agreement with experimental data, and then 15 hydrocyclones with different overflow diameters, overflow lengths and input velocities were employed for more detailed analyses. The separation process through a hydrocyclone is counted as an economical process when ther is not only a low pressure drop inside the hydrocyclone, but also a high separation efficiency. As a result, regarding the mentioned criteria, the optimum hydrocyclone, whereby the highest performance of the hydrocyclone is exploited, was obtained by applying the 15 sets of CFD data to a Neural Network (NN) and then by optimizing the function generated by the NN by means of a Genetic Algorithm (GA). The innovation of this research work is the three-phase modeling.

Abstract This study assessed the effect of non-thermal plasma (NTP) on Nannochloropsis gaditana cell rupture and subsequent lipid extraction. Micrograph images showed that the surface of original N. gaditana cells appeared smooth and had no apparent holes, whereas after NTP the cells showed a non-uniform apparently fractured surface with many pores and large splits. Maximum lipid recovery from N. gaditana cells (~19%) for NTP-assisted rupture was observed at 10 min, similar to extraction after 10 min sonication (19.0%). The lipid recovery after both pretreatments (average 19.0%) was 2-fold higher than the control treatment (no pretreatment 9.5%). In addition, lipids from unruptured algal cells were mainly composed of ω-3polyunsaturated fatty acids (~31% of total fatty acids), while lipids after NTP were predominantly composed of saturated fatty acids (36.0% of total fatty acids), which could be advantageous for biodiesel production. This study demonstrates an alternative approach based on NTP-technology for algal cell rupture prior to lipid extraction with potential uses for algal biodiesel production.