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 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 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 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 Bio-oxidation leaching of refractory gold concentrate was carried out in a typical gas-liquid-solid three-phase stirred bioreactor. The bacteria, which adhered to solid particle surfaces and spread over the liquid phase, require sufficient oxygen and nutrient of carbon and nitrogen, and then the mass transfer rate should be considered. However, the mass transfer coefficient, which could be used to evaluate the mass transfer rate, was determined by gas holdup, bubble diameter and power consumption. Therefore, a three-phase Eulerian equation with k-ε turbulence model and additional models of two bubble diameter, a torque and a mass transfer coefficient were applied in the simulation. The simulation results were validated with experimental data and used to analyze the spatial distribution of the mass transfer coefficient. The results demonstrated that the simulation and experimental data of Sauter mean bubble diameter and power number were in good agreement and the simulation results of the mass transfer coefficient were agree with the values calculated by an empirical correlation. The Davoody model can be strongly recommended for further simulation of the bubble diameter, and the gas holdup and mass transfer coefficient were very unevenly distributed in the lower zone. Hence, the lower impeller clearance should be considered.

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.

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 In this work, the vapor-liquid equilibrium experimental data for the systems of isopropyl chloroacetate + isopropanol, isopropyl chloroacetate + cyclohexane and isopropyl chloroacetate + benzene were measured by a modified Rose-type recirculating still under the pressure of 101.3 kPa. The thermodynamic consistency of the measured data was verified by the Herington and van Ness methods, respectively. The experimental data were correlated by the NRTL, Wilson, and UNIQUAC activity coefficient models, and the corresponding interaction parameters of the three models were obtained. The root-mean-square deviations between the experimental data and calculated results for the temperature and the mole fraction of the vapor phase were less than 0.58 K and 0.0066, respectively. In addition, the excess Gibbs energy was calculated for the three systems.

Abstract Due to the importance of supercritical fluid technology (SFT) in different industries, it has been the subject of intense research in recent decades. Solubility is a key concept in SFT. In fact, obtaining knowledge about the theoretical concepts of solubility and related experimental measurement methods can be useful in developing and improving the quality of research in this field. This study reviews the fundamental knowledge of solubility in supercritical fluids and investigates the significant topics in this field, including high-pressure phase behavior, experimental measurement methods, modeling, and molecular simulation of solubility.

Abstract Two deep eutectic solvents (DES) based on betaine (B) and propylene glycol (PG) in molar ratios of 1:4 and 1:5 were prepared and their physico-chemical properties were determined. Liquid-liquid equilibria at 298.15 K and atmospheric pressure were determined for 13 quasi-three-component systems with a hydrocarbon (n-hexane, n-heptane, i-octane or toluene), solute (pyridine or thiophene) and DES (B-PG 1:4 or B-PG 1:5). Experimental phase diagrams and calculated distribution ratios showed that DESs are more suitable for denitrification than for desulfurization. The equilibria in the investigated systems were described by the NRTL and UNIQUAC models, and good agreement with experiments was obtained.

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 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 CoMo/MgO catalysts with low loading of cobalt and molybdenum were prepared by incipient wetness impregnation and the sol-gel method for high yield production of carbon nanotubes (CNT). A detailed characterization of the catalysts, as-produced CNT and purified CNT, indicated a relationship between carbon nanotube properties, synthesis and purification steps. Excess of molybdenum in the catalyst caused a decrease in carbon yield and produced CNT with a lower degree of graphitization. Catalysts prepared by the sol-gel method and with higher molybdenum loading showed an improved interaction between cobalt and molybdenum, increasing the formation of CoMoO4, which was not completely removed during the purification step. The purification removed all MgO and part of the cobalt and molybdenum present in samples without significant damage to the CNT structure. An increase in sample purity could be achieved by increasing reaction time.

Abstract This work presents the processing of a high-acidity oil through sequential reactions of esterification using montmorillonite K10 and transesterification using zinc monoglycerolate. Since these solids had not been employed along with this approach beforehand, the objective of this work is to provide a general insight of the proposed process and demonstrate its technical feasibility. In this sense, the processing of a synthetic mixture containing soybean oil and lauric acid provided a reduction of the free fatty acid content from (40.8±0.1) % to (3.1±0.4) % after the esterification reaction and a fatty acid methyl ester yield of (95.4±0.2) % was obtained after the transesterification reaction. As compared to traditional homogeneous catalysts, the solid catalysts employed in this work require higher reaction times to achieve satisfactory ester yields but, on the other hand, they are less sensitive to the presence of both water and free fatty acids in the raw materials and can be easily recovered and reused. Therefore, the results accomplished may help the development of a technology for processing high-acidity fatty materials in order to obtain biodiesel, although its economic feasibility still needs a further assessment.

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.