Numerical investigation of mixing by induced electrokinetic flow in T-micromixer with conductive curved arc plate

Mixing is essential in microdevices. Therefore, increasing the mixing efficiency has a significant influence on these devices. Using conductive obstacles with special geometry can improve the mixing quality of the micromixers. In this paper, a numerical study on the mixing caused by an induced-charge electrokinetic micromixer was carried out using a conductive plate with a curved arc shape instead of a conductive flat plate or other non-conductive obstacles for Newtonian fluids. This study also explored the effect of the different radius curves, span length, the number of curved arc plates in the channel, the pattern of arrangement, concavity direction, and the orientation angle against the flow on the mixing. Furthermore, the efficiency of the T-micromixer against a flow with a low diffusion coefficient was investigated. It should be noted that the considered channel is symmetric regarding to the middle horizontal plane and an addition of flat plate reflects a formation of symmetric flow structures that do not allow to improve the mixture process. While an addition of non-symmetric curved arc plates al-lows to increase the mixing by creating vortices. These vortices were created owing to the non-uniform distribution of induced zeta potential on the curved arc plate. A rise in the span length of the curved arc plate when the radius was constant improved the mixing. When three arc plates in one concavity direction were used, the mixing efficiency was 91.86%, and with a change in the concavity direction, the mixing efficiency increased to 95.44%. With a change in the orientation angle from 0 to 25, the mixing efficiency increased by 19.2%

Display of hidden properties of flexible aerogel based on bacterial cellulose/polyaniline nanocomposites with helping of multiscale modeling

Tuning the synthesis conditions of polyaniline (PANI) such as aniline monomer’s protonation states and adding surfactants into polymerization mixture or even the existence of bacterial cellulose (BC) had a substantial influence on the final properties. To explore the relationship between components presented in the polymerization mixture, simulation tools (molecular dynamics (MD)/Monte Carlo (MC)/Density functional theory (DFT)) can be used. Herein, nanocomposite aerogels of BC/PANI were fabricated in the presence of anionic surfactants; sodium dodecyl benzene sulfonate (SDBS) or sodium dodecyl sulfonate (SDS) at two different concentrations (0.05 M and 1 M) of HCl solution. Two types of aniline monomers were considered in the polymerization mixture based on HCl solution’s concentrations including neutral and protonated aniline in 0.05 and 1 M, respectively. Various morphologies from nanobelts (with a width of 100–500 nm) and polyhedrons (with a thickness of 100–700 nm) in 0.05 M of acid solution in the presence of SDBS or SDS, respectively, were detected. Based on DFT computations it was found that electrostatic interactions and the formation of hydrogen bonds play a vital role in the interfacial interaction mechanism between both surfactants (SDBS and SDS) and different protonation forms of aniline monomers. Nevertheless, in the case of SDBS and aniline monomers (in both 0.05 and 1 M of HCl solutions), an excess interaction mechanism, namely π-π stacking, was observed, which enhanced the interaction between them and confirmed by experimental results. Therefore, the highest conductivity of 0.8 S/cm was obtained for the BC/PANI prepared with SDBS in 1 M of HCl solution. Besides, the smallest energy gap of 2.74 eV was predicted from DFT calculations for this sample that further confirmed its high electrical properties and smaller band gap at 3 nm, which was also confirmed by MD and MC

Competitive removal of heavy metal ions from squid oil under isothermal condition by CR11 chelate ion exchanger

42 Páginas; 11 Figuras; 2 TablasHeavy metal ions (HMIs) are serious threats to the environment. Sub-critical water treatment was used to mimic contamination of squid oil in aqueous, metal-soap and oil phases. Isothermal adsorption of HMIs (Cu2+, Pb2+, Cd2+ and Zn2+) was studied from aqueous phase to oil phase (493, 523, 548, and 573 K) for solutions with different initial concentration of HMIs was studied. Decomposition of glycerides into fatty acids was favored at high subcritical temperatures, with metal-soap phase showing the highest chelation ability toward Cu2+ (96%, isotherm 573 K). The removal-ability of HMIs from contaminated oil was performed by CR11 chelate ion exchanger, showing facilitated removal from metal-soap and oil phases at low temperatures compared to general-purpose PEI-chitosan bead and PEI-chitosan fiber sorbents. The chelation behavior of Pb2+ and Cd2+ was the same in the OIL, with maximum values of 5.7 × 10−3 (mol/l) and 5.0 × 10−3 (mol/l) at 573 K, respectively. By contrast, concentration of Zn2+ ion showed a slight increase with increasing temperature due to electrostatic forces between Zn2+ and active sites of glycerides in oil phase. For oil solution, the selectivity of adsorption for CR11, especially for Zn2+, was at least five-fold larger compared to PEI-chitosan bead and PEI-chitosan fiber adsorbents.Peer reviewe

Effect of adding nitrate on the performance of a multistage biofilter used for anaerobic treatment of high-strength wastewater

7 páginas, 6 figuras, 1 tabla.This laboratory research was carried out to evaluate the performance of a multistage anaerobic biofilm reactor, with six compartments and a working volume of 70 L, for the treatment of a strong synthetic nitrogenous and high-strength wastewater at an operational temperature of 26 ± 0.5 °C. Initially, the performance of the reactor was studied when subjected to an increase in the hydraulic retention time (HRT) at a constant influent COD concentration of 10,000 mg/L. Five different HRTs were studied: 0.25, 0.67, 1, 3 and 5 days, which were equivalent to 6, 16, 24, 72 and 120 h, respectively. By increasing the HRTs from 6 h to 1 day, COD and BOD removal efficiencies were increased from 63% to 84% and from 66% to 87%, respectively. Moreover, at an HRT of 3 days, COD and BOD removal efficiencies were equal, reaching 93%. In the second phase of the research, the effect of adding nitrate with a concentration of 3000 mg/L at an influent organic loading rate of 10 g COD/L d was researched on the reactor performance and the amount of biogas produced. Denitrification took place almost solely in the first three compartments of the reactor, with efficiencies of 85%, 95% and 98%, respectively. The nitrite produced was only detected in the first and second compartments at concentrations of 138 and 24 mg/L, respectively. In addition, no accumulation of nitrite was detected in the reactor. Furthermore, the denitrification caused an increase in the total volume of produced biogas from 102 to 178 L/d.The authors gratefully acknowledge the financial support of the Water Research Center of Greentech (Co., Ltd.), Shiraz and the R&D center of Anshan Corporation.Peer reviewe

Anaerobic treatment of synthetic medium-strength wastewater using a multistage biofilm reactor

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m3 day, respectively. A decrease in HRT from 24 to 16 h had no effect on COD removal efficiency. When HRT decreased to 8 h, COD removal efficiency was still 84.9%. Recirculation ratios of 0.5 and 1.0 had no effect on COD removal but other factors such as the volatile fatty acid (VFA) content were affected. The effect of toxic shock was also investigated and results showed that the main advantage of using this bioreactor lies in its compartmentalized structure.The authors gratefully acknowledge the financial support of the Water Research Center of Greentech (Co. Ltd.), Shiraz, Iran.Peer reviewe

Anaerobic treatment of synthetic medium-strength wastewater using a multistage biofilm reactor

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m3 day, respectively. A decrease in HRT from 24 to 16 h had no effect on COD removal efficiency. When HRT decreased to 8 h, COD removal efficiency was still 84.9%. Recirculation ratios of 0.5 and 1.0 had no effect on COD removal but other factors such as the volatile fatty acid (VFA) content were affected. The effect of toxic shock was also investigated and results showed that the main advantage of using this bioreactor lies in its compartmentalized structure.The authors gratefully acknowledge the financial support of the Water Research Center of Greentech (Co. Ltd.), Shiraz, Iran.Peer reviewe

Investigating the role of transreactions on degradation behavior of phenoxy/poly(trimethylene terephthalate)/clay nanocomposites using thermal analysis techniques

The properties of reactive polymer blends are strongly influenced by the interchange/exchange reactions. The effect of nanofillers on these reactions, in particular transreactions, has not yet fully understood. This work is devoted to investigate transesterification and its consequent effect on degradation behavior of phenoxy/poly(trimethylene terephthalate) (PTT) nanocomposites using thermal analysis techniques. 1H NMR results showed that the maximum extent of transreactions occurred in the blends loaded with just 1 wt.% nanoclay. A mechanism based on nanoconfinement was proposed to show how nanoclay particles affect transreactions of the blend constituents. Thermal degradation kinetic studies, using KAS isoconversion method, revealed that addition of only 1 wt.% clay improves thermal stability of the pristine blend whereas higher amount of clay accelerates degradation process. An attempt was made to establish correlations among these changes in thermal degradation behavior, the extent of transreactions and dynamic mechanical properties

The role of three-dimensional scaffolds based on polyglycerol sebacate/ polycaprolactone/ gelatin in the presence of Nanohydroxyapatite in promoting chondrogenic differentiation of human adipose-derived mesenchymal stem cells

Abstract Background Tissue engineering for cartilage regeneration has made great advances in recent years, although there are still challenges to overcome. This study aimed to evaluate the chondrogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) on three-dimensional scaffolds based on polyglycerol sebacate (PGS) / polycaprolactone (PCL) / gelatin(Gel) in the presence of Nanohydroxyapatite (nHA). Materials and methods In this study, a series of nHA-nanocomposite scaffolds were fabricated using 100:0:0, 60:40:0, and 60:20:20 weight ratios of PGS to PCL: Gel copolymers through salt leaching method. The morphology and porosity of prepared samples was characterized by SEM and EDX mapping analysis. Also, the dynamic contact angle and PBS adsorption tests are used to identify the effect of copolymerization and nanoparticles on scaffolds' hydrophilicity. The hydrolytic degradation properties were also analyzed. Furthermore, cell viability and proliferation as well as cell adhesion are evaluated to find out the biocompatibility. To determine the potential ability of nHA-nanocomposite scaffolds in chondrogenic differentiation, RT-PCR assay was performed to monitor the expression of collagen II, aggrecan, and Sox9 genes as markers of cartilage differentiation. Results The nanocomposites had an elastic modulus within a range of 0.71–1.30 MPa and 0.65–0.43 MPa, in dry and wet states, respectively. The PGS/PCL sample showed a water contact angle of 72.44 ± 2.2°, while the hydrophilicity significantly improved by adding HA nanoparticles. It was found from the hydrolytic degradation study that HA incorporation can accelerate the degradation rate compared with PGS and PGS/PCL samples. Furthermore, the in vitro biocompatibility tests showed significant cell attachment, proliferation, and viability of adipose-derived mesenchymal stem cells (ADMSCs). RT-PCR also indicated a significant increase in collagen II, aggrecan and Sox9 mRNA levels. Conclusions Our findings demonstrated that these nanocomposite scaffolds promote the differentiation of hADSCs into chondrocytes possibly by the increase in mRNA levels of collagen II, aggrecan, and Sox9 as markers of chondrogenic differentiation. In conclusion, the addition of PCL, Gelatin, and HA into PGS is a practical approach to adjust the general features of PGS to prepare a promising scaffold for cartilage tissue engineering. Graphical Abstrac