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A new mononuclear hexachlororhenate complex salt ((2-ppyH)2[ReCl6], where 2-ppyH+ = 2-phenylpyridinium cation) was synthesized and structurally characterized by X-ray crystallography. The hexachlororhenate complex ([ReCl6]2¯) was utilized as an efficient catalyst for the electrocatalytic dechlorination of dichloromethane (CH2Cl2). The cyclic voltammograms (CVs) in the presence of CH2Cl2 show catalytic cathodic currents in place of the reversible wave for the redox pair Re(IV)/Re(III). The controlled potential electrolysis was also employed to study the catalytic carbon–chloride (C–Cl) bond cleavage of CH2Cl2 in the presence of [ReCl6]2¯. The major electrolysis product was characterized as 1,2-dichloroethane (EDC), determined by gas chromatography–mass spectrometry (GC–MS). According to the cyclic voltammetry data, an electrocatalytic mechanism was proposed using the density functional theory (DFT, M06-L) to investigate the cleavage of the C–Cl bond in the presence of hexachlororhenate(IV). The optimized structures and the ΔG° changes (ΔG°g and ΔG°sol) for the proposed mechanism were calculated. Accordingly, the electrochemical pathway was thermodynamically feasible in both gas and solvent (acetonitrile) phases. The DFT studies suggest that the chlorine elimination proceeds through an interaction between the chlorine atom of CH2Cl2 and the five-coordinated unsaturated rhenium (III) intermediate. The transition state for the transfer of chlorine to the Re center was located with the assessed barrier energy of + 16.53 kJ mol−1 in the solvent phase.

Herein, iron– [Fe] and cobalt–oxide [Co] nanoparticles supported on carbon were synthesized through the construction of the co-assembly strategy via the mixture of carbon source resol, diglyme, triblock copolymer, and M(acac)x (M = Fe3+ and Co2+) complexes. The prepared nanocomposites possess large pore sizes, high surface areas, large pore volumes, and highly dispersed nanoparticles. The exceptional catalytic performance together with high selectivity toward alcohol and light olefin products over the [Fe] and [Co] catalysts were observed in the CH4 carbonylation reaction. The [Fe] catalyst displayed an acceptable CH4 conversion of 40% and high selectivity toward C2–C4 light olefins (>42%) and C1–C4 alcohols (>38%) while exhibiting a low CO2 production at moderate CO conversion of >52%. The CH4 conversion was lower over the [Co] catalyst, although the selectivity of alcohols stretched beyond the [Fe] catalyst (~76%), with CH4 and CO conversion of 15.40 and 31.83%, respectively. Besides alcohol, low acetic acid and ethanal (acetaldehyde) formed over the [Co] catalyst. The catalysts were also employed in the Fischer–Tropsch synthesis (FTS). The [Fe] catalyst demonstrated high FTS catalytic performance with 85% CO conversion, the high C2–C4 selectivity, and low selectivity of methane. In comparison, the [Co] catalyst exhibited high conversion of CO (>81%) and suitable selectivity toward C2–C4 and C5+ hydrocarbons.

The electrical explosion of wire (EEW) method provides a sufficiently route for large-scale preparation of nickel oxide nanopowders (NiO-NPs) with a small degree of contamination. In this study, Central composite design of the response surface methodology (RSM) was firstly employed to evaluate the average crystallite size (ACS) and average size distribution (ASD) of NiO-NPs. Twenty types of NiO-NPs were prepared by adjusting three operating parameters (wire diameter, the distance between two electrodes and the voltage) at five levels by the method of multiple variable analysis. The check experiments revealed that all the three operating parameters have significant effect on the ACS and ASD of NiO-NPs. For each response, a suitable second-order regression equation was obtained by applying analysis of variance. In addition, the results revealed acceptable agreement among experimental data and predicted results. Moreover, the optimum region for production of NiO-NPs with size below 100 nm by EEW method was obtained. Characterization of NiO p-type semiconductor in terms of size distribution, morphology, chemical composition and phase structure was carried out by TEM, SEM/EDX, XRD and BET analyses. The results nominated the EEW technique as a unique method for large-scale and economic preparation of NiO-NPs with defined structural features.

In the present paper, the effect of the external partial magnetic field is studied on the flow and heat transfer of various nanofluids in a microchannel via the incompressible preconditioned lattice Boltzmann method. The simulations are performed for various parameters such as Hartmann number (Ha) ranging from 0 to 40 and surface non-dimensional slip coefficient (B) of 0–0.03. The nanofluid volume fraction is fixed at 1%, and the results are compared with pure water. The effect of using different nanoparticles (Al2O3, CuO, Ag, and Fe) has been investigated on the Nusselt number. The acceptable results are obtained by comparing numerical and experimental data. The results generally show that using Ag and CuO nanoparticles, respectively, leads to the best and worst heat transfer rate. Eventually, the highest and lowest Nusselt numbers are from these nanoparticles, where Ag and Al2O3 give the worst and best stress rates. It is found that for a specific requirement of microchannels in heat transfer application, there would be a certain nanofluid by specific nanoparticles. This novel study opens discussion by proposing a new alternative way to improve the heat transfer in microchannel which is applicable to the systems where microchannel is used as heat sinks.

Many processes in nature (e.g., physical and biogeochemical processes in hyporheic zones, and arterial mass transport) occur near the interface of free-porous media. A firm understanding of these processes needs an accurate prescription of flow dynamics near the interface which (in turn) hinges on an appropriate description of interface conditions along the interface of free-porous media. Although the conditions for the flow dynamics at the interface of free-porous media have received considerable attention, many of these studies were empirical and lacked a firm theoretical underpinning. In this paper, we derive a complete and self-consistent set of conditions for flow dynamics at the interface of free-porous media. We first propose a principle of virtual power by incorporating the virtual power expended at the interface of free-porous media. Then by appealing to the calculus of variations, we obtain a complete set of interface conditions for flows in coupled free-porous media. A noteworthy feature of our approach is that the derived interface conditions apply to a wide variety of porous media models. We also show that the two most popular interface conditions—the Beavers–Joseph condition and the Beavers–Joseph–Saffman condition—are special cases of the approach presented in this paper. The proposed principle of virtual power also provides a minimum power theorem for a class of flows in coupled free-porous media, which has a similar mathematical structure as the ones enjoyed by flows in uncoupled free and porous media. The derived interface conditions are summarized along with a pictorial description of the problem, which pertains to the flow of an incompressible fluid in coupled free-porous media. $$\Psi $$ is the power expended density along the interface. $$\mathbf {v}_{\text {free}}$$ and $$\mathbf {v}_{\text {por}}$$ are the velocities in the free and porous regions, respectively. A superposed asterisk on a (vectorial) quantity denotes its tangential component along the interface. $$v_n$$ is the normal component of the velocity at the interface from the free region into the porous region. $$\mathbf {T}_{\text {free}}^{\text {extra}}$$ and $$\mathbf {T}_{\text {por}}^{\text {extra}}$$ , respectively, denote the extra Cauchy stresses in the free and porous regions. $$\mathbf {t}_{\text {free}}$$ and $$\mathbf {t}_{\text {por}}$$ , respectively, denote the tractions on the free and porous sides of the interface with outward normals $$\widehat{\mathbf {n}}_{\text {free}}$$ and $$\widehat{\mathbf {n}}_{\text {por}}$$ . A unit tangential vector along the interface is denoted by $$\widehat{\mathbf {s}}$$ .

Modeling flow through porous media with multiple pore-networks has now become an active area of research due to recent technological endeavors like geological carbon sequestration and recovery of hydrocarbons from tight rock formations. Herein, we consider the double porosity/permeability (DPP) model, which describes the flow of a single-phase incompressible fluid through a porous medium exhibiting two dominant pore-networks with a possibility of mass transfer across them. We present a stable mixed discontinuous Galerkin (DG) formulation for the DPP model. The formulation enjoys several attractive features. These include: (i) Equal-order interpolation for all the field variables (which is computationally the most convenient) is stable under the proposed formulation. (ii) The stabilization terms are residual-based, and the stabilization parameters do not contain any mesh-dependent parameters. (iii) The formulation is theoretically shown to be consistent, stable, and hence convergent. (iv) The formulation supports non-conforming discretizations and distorted meshes. (v) The DG formulation has improved element-wise (local) mass balance compared to the corresponding continuous formulation. (vi) The proposed formulation can capture physical instabilities in coupled flow and transport problems under the DPP model., Comment: There was a mistake in the boundedness proof in the earlier version (specifically version #1). We now rectified this mistake and improved sections 1 and 3

PurposeIn the present study, laminar steady flow of nanofluid through a trapezoidal channel is studied by using of finite volume method. The main aim of this paper is to study the effect of changes in geometric parameters, including internal and external dimensions on the behavior of heat transfer and fluid flow. For each parameter, an optimum ratio will be presented.Design/methodology/approachThe results showed that in a channel cell, changing any geometric parameter may affect the temperature and flow field, even though the volume of the channel is kept constant. For a relatively small hydraulic diameter, microchannels with different angles have a similar dimensionless heat flux, while channels with bigger dimensions show various values of dimensionless heat flux. By increasing the angles of trapezoidal microchannels, dimensionless heat flux per unit of volume increases. As a result, the maximum and minimum heat transfer rate occurs in a trapezoidal microchannel with 75° and 30 internal’s, respectively. In the study of dimensionless heat flux rate with hydraulic diameter variations, an optimum hydraulic diameter (Dh) was observed in which the heat transfer rate per unit volume attains maximum value.FindingsThis optimum state is predicted to happen at a side angle of 75° and hydraulic diameter of 290 µm. In addition, in trapezoidal microchannel with higher aspect ratio, dimensionless heat flux rate is lower. Changing side angles of the channels and pressure drop have the same effect on pressure drop. For a constant pressure drop, if changing the side angles causes an increase in the rectangular area of the channel cross-section and the effect of the sides are not felt by the fluid, then the dimensionless heat flux will increase. By increasing the internal aspect ratio (t_2/t_3), the amount of t_3 decreases, and consequently, the conduction resistance of the hot surface decreases.Originality/valueThe effects of geometry of the microchannel, including internal and external dimensions on the behavior of heat transfer and fluid flow for pressure ranges between 2 and 8 kPa.

This paper presents the numerical solution of immiscible two-phase flows in porous media, obtained by a first-order finite element method equipped with mass-lumping and flux up-winding. The unknowns are the physical phase pressure and phase saturation. Our numerical experiments confirm that the method converges optimally for manufactured solutions. For both structured and unstructured meshes, we observe the high-accuracy wetting saturation profile that ensures minimal numerical diffusion at the front. Performing several examples of quarter-five spot problems in two and three dimensions, we show that the method can easily handle heterogeneities in the permeability field. Two distinct features that make the method appealing to reservoir simulators are: (i) maximum principle is satisfied, and (ii) mass balance is locally conserved., 25 pages, 17 figures; added reference

The main approach of this study was to investigate the effect of the type of synthesis method on the improvement of catalyst performance in Fischer–Tropsch reaction. For this purpose, a series of the novel catalysts were synthesized using iron and cobalt nitrate salts, tetraethoxysilane and novolac phenolic resin by different method. These catalysts were abbreviated as M1–Co–Fe–novolac/SiO2, M2–Co–Fe–novolac/SiO2, and M3–Co–Fe–novolac/SiO2 and characterized using different techniques. The results of the Brunauer–Emmett–Teller and Fourier transform infrared techniques showed that M2–Co–Fe–novolac/SiO2 catalyst has a higher surface area than the other two ones. This catalyst was analyzed by using X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray, and temperature-programed reduction (TPR) techniques. The XRD results confirmed the appearance of suitable active phases, such as metal phase, carbide, and low oxidation state of metals. Based on TPR results, the lower reduction temperature, compared with similar samples, confirmed the high activity of the M2–Co–Fe–novolac/SiO2 catalyst. Catalytic activity and selectivity for Fischer–Tropsch reaction were investigated in the standard conditions by using catalytic tests. The high conversion percentage of CO indicated high activity of the catalyst. On the other hand, the olefin to paraffin ratio (O/P), which was a criterion for catalytic efficiency in industrial, was also acceptable.

Energy piles are used around the world to partially heat/cool buildings or de-ice pavements. Thermal conductivity of concrete is one of the key parameters which highly affects the thermal performance of energy geostructures. Application of higher thermally conductive concrete in energy piles helps to harvest more shallow geothermal energy. Besides, higher thermally conductive concrete results in more uniform temperature distribution and will significantly increase the efficiency of the geothermal bridge deck de-icing. It is expected that the thermal conductivity of the concrete depends on its age and the applied curing conditions. The thermal conductivity of concrete can progress with the progression of hydration. While the hydration process is highly dependent on the curing condition that is applied. In this study, several concrete samples are prepared and cured under different conditions (inside the humidity room, indoor, and outdoor). Then the thermal conductivity of concrete samples at different ages are measured according to ASTM D5470-17. Results show an increase in thermal conductivity of concrete cured in humidity room for the first 30 to 40 days that thermal conductivity were measured In addition comparison of thermal conductivity of the outdoor and indoor samples show the importance of the ambient temperature and relative humidity on the thermal conductivity value.

Mechanical energy is a natural energy that can be considered as a form of rich, clean, and renewable energy and it can be harvested by using piezoelectric materials. Water pollution is one of the series of threats faced by our planet and jeopardizes the ecosystem. Piezocatalysis could be a promising solution for this issue. This research focused on the sonochemical synthesis of PbTiO3 (PTO) piezocatalyst and studied the effect of synthesis parameters, operation conditions during the piezocatalysis process, and the effect of DNA as a modifier on piezocatalytic activity of PTO. Results showed that the synthesis parameters show a significant effect on the piezocatalytic activity of PTO. The origin of this effect came from the morphology, purity, and orientation of final products. Results displayed that the degradation reaction was completed during the first hour. 97.1 % of Acid Red 141 (AR141) was degraded by controlling both synthesis and operation conditions. In this research, the ultrasonic probe with a power of 100-600 W and a frequency of 18 kHz was used.

The use of the gasoline additive methyltert‐butyl ether (MTBE) has caused serious concern about groundwater and surface water contamination. In this study, UV light/ NiO nano‐photocatalyst (NiONP) system was firstly used to degradation of MTBE in contaminated water. A low‐cost and environmentally clean exploded‐wire plasma technique based on cheap solid nickel source is developed for preparation of NiONP. Optical, magnetic and physicochemical properties were successfully characterized using DRS, VSM, XRD, SEM, EDX, TEM and BET techniques. The NiONP exhibits excellent photocatalytic degradation ability of MTBE. The degradation process was monitored during the photocatalytic reaction by gas chromatography‐mass spectrometry (GC‐MS). It has been found that MTBE undergoes a series of intermediate step, which leads to form a number of intermediate products, mainly acetone, formic acid and t‐butyl formate (TBF). According to the results of the intermediates determination, a possible pathway degradation of MTBE was also proposed.

In this numerical study, laminar flow of water nanofluid/GNP–SDBS (graphene nanoplatelet–sodium dodecylbenzene sulfonate) for 0–0.1% solid nanoparticles mass fraction was investigated for Reynolds numbers of 50–1000 in 3D space via finite volume method. In the newly proposed microchannel design, the cooling fluid is moving in countercurrent in the upper and lower layers of the microchannels, and there are cavities and sinusoidal routes on the solid walls of the microchannel, and the presence of rectangular ribs on the flow centerline along the fluid path enhances mixing for cooling fluid and creates better heat transfer for warm surfaces. The results of this study show that this special design of the microchannel can have a substantial increase in Nusselt number and heat transfer so that in the considered geometry by adding solid nanoparticles mass fraction it is possible to increase average Nusselt number for each Reynolds number by approximately 20%. Also, the mixing of the fluid because of formation of secondary flows has a strong effect on making the temperature distribution uniform in the cooling fluid and solid bed (wall) of the microchannel, especially in the lower layer. The upper layer of the microchannel always has a lower temperature due to indirect contact with heat flux compared with the lower layer. In this study, by increasing Reynolds number and mass fraction of solid nanoparticles the Nusselt number is increased and heat resistance of the lower wall of the microchannel is reduced. Based on the investigation of flow field and heat transfer, the use of the proposed design of the microchannel is recommended for Reynolds number less than 300.

Different sunscreens are employed to prevent photo damage (cancer, inflammation, etc.), including ZnO. ZnO is safe when applied as micro-size particle. To overcome some visual problems of ZnO micro-size particles, this sunscreen has been introduced as nano-size particles. Unfortunately, ZnO nanoparticles have raised some health concerns, due to Zn+2 release. On the other hand, it has been shown that ZnO metallic lattice change by metal doping decreases its solubility and toxicity. Therefore, we have decided here to develop new ZnO metallic lattice to reduce its cytotoxicity. In this study, Ag+1-promoted Zn-based nanocompounds [Zn(O):Ag] were synthesized as a novel compound and were characterized. XRD analysis showed that Ag+1 ion percolates into ZnO crystalline lattice and changes its lattice properties (strength bond, vacancies, and etc.). Cell culture studies and MTT assay on human skin (HFF-1) cells exposed to UVA radiation showed that [Zn(O):Ag] was increased cells viability in the presence of UVA radiation compared to ZnO. Actually, Ag+1 ion has catalyzed photoactivity of ZnO compound. UV-blocking tests showed that UVA-absorbance of [Zn(O):Ag] has increased compared to ZnO. Dichlorofluoroscein diacetate-ROS assay and Zn+2 release experiments in the presence of cells showed that [Zn(O):Ag] has reduced Zn+2 ions release into culture medium and its toxicity. Our study shows that doped ZnO nanostructure has the potential to be applied as a safe and effective nanoparticulate sunscreen.

A novel graphitic carbon nitride g-C3N4-NiTi-layered double hydroxide heterojunction film photo-catalyst (g-C3N4-NiTi-LDH) was prepared by facile hydrothermal synthesis. The g-C3N4 and g-C3N4-NiTi-LDH film samples were characterized by AFM, SEM, EDX, PL, XRD and DRS analysis. DRS analysis indicated a significant red shift of absorption edge due to the interfacial coupling effect between g-C3N4 and NiTi-LDH. PL analysis showed an efficient inhibition of electron-hole recombination in the blended g-C3N4-NiTi-LDH. A fixed-bed photoreactor containing conjugated g-C3N4-NiTi-LDH film-coated glass was fabricated and employed to photocatalytic degradation of methyl orange (MO). As a result, the g-C3N4-NiTi-LDH film showed greater photocatalytic activity compared with pure samples of g-C3N4 and NiTi-LDH film samples. Maximum MO degradation efficiency (100%) was achieved using g-C3N4-NiTi-LDH films within 240 min.

The inhibition effect of a Schiff base with several functional groups on the corrosion of aluminum in alkaline solution is studied by experimental techniques and density function theory (DFT) calculations. The Schiff base are characterized by 1HNMR, 13CNMR, FT-IR, and CHN elemental analysis. In addition, different electrochemical and corrosion techniques such as weight loss, tafel polarization, electrochemical impedance spectroscopy (EIS) and optical microscopy images are performed to analyze the inhibiting performances. In the Tafel measurements the cathodic Tafel slopes values incurred small changes with increasing the inhibitor concentration, which revealed that the inhibitor was adsorbed on the aluminum surface. The inhibition efficiencies are calculated from weight loss measurement and electrochemical tests. The adsorption of the inhibitor onto the aluminum surface follows the Langmuir adsorption isotherm with the free adsorption energy of −8.66 kJ mol−1. The calculated adsorption energies and the amount of charge transfer obtained by DFT calculation revealed that corrosion inhibition effectively occurs with chemisorption, where new N Al bonds are formed between of N atoms in azo (–N N–) group and Al surface atoms, which is confirmed from ab initio molecular dynamics (AIMD) simulation.

The hollow Pd–PVP–Fe nanosphere and Fe–PVP nanoparticle catalysts were synthesized by thermal method. Mixing of two metallic nanocatalysts was applied in the Csp–S cross-coupling reactions between diphenyl disulfide and phenylacetylene under mild conditions in water. Results show that bi-catalytic system has higher catalytic efficiencies than their monocatalytic systems due to synergy between two catalysts. Order of adding two metallic catalysts were adjusted into the coupling reaction medium. Therefore, various bi-catalytic systems were obtained and characterized by XRD, SEM, EBSD, EDX, UV–Vis spectra, and particle size analyzer. Under special order of adding, the obtained hollow nanoshell-sphere Fe@Fe/Pd reactor showed higher catalytic activity in the coupling reaction compared to other bi-catalytic systems. The Csp–S coupling products obtained of various diaryl disulfides and phenylacetylene at presence Fe@Fe/Pd (only 7.3 × 10−5 mmol Pd) catalyst with moderate to high yields in water solvent and mild reaction conditions. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The recovered catalyst was characterized by XRD, SEM, EBSD, EDX, and UV–Vis spectra. The Fe@Fe/Pd was reused at least six repeating cycles without any loss of its high catalytic activity. Tuning morphology and chemical composition of bi-catalytic system are key mainstays of high activity of Fe@Fe/Pd in repeating cycles of cross-coupling reactions.

Graphical abstract, Highlights • The [Zn(O)/M] (M = Mg, Al, Ca, Ti) synthesize by thermal method and characterize. • The metal dopants percolate into crystal lattice of ZnO and stable it. • The [Zn(O)/M] shows very low amount of Zn+2 release into culture medium. • Intracellular reactive oxygen species generation decrease under UVA radiation. • The [Zn(O)/M] protects of human skin cells against UVA radiation., Application of ZnO nanoparticles in sunscreens exposes human skin with their adverse effects, which correlates to dissolution/translocation of free Zn+2 ions. The possibility of decreasing solubility and therefore, reducing toxicity, by structural modifications have been discussed as a solution. The present investigation has developed new metallic lattices of ZnO to reduce cytotoxicity of ZnO nanoparticles. Novel metal-promoted Zn-based nanocomposites ([Zn(O)/M], M = Mg, Al, Ca, Ti) were synthesized and their physicochemical properties and their cytotoxicity were evaluated. Solubility and release studies showed that modification of ZnO structure decreases release of Zn+2 into culture medium. XRD and UV absorbance analyses showed that metallic-dopants percolate into crystalline lattice of ZnO. This phenomenon is basic reason for stability of Zn-based network. Cell culture studies and MTT assay on human skin cells (HFF-1) exposed to UVA radiation showed that the level of protection of [Zn(O)/M] compounds were more than of [ZnO]. Dichlorofluoroscein diacetate-ROS assay and Zn+2 release experiments indicated that [Zn(O)/M] nanocomposites decreased the level of ROS generation and Zn+2 release in compared to ZnO, indicating higher safety of nanocomposites. This study shows that the synthesized Zn-based nanocomposites have potential to be used as safer and more effective sunscreens than ZnO.

An increase in temperature changes the groundwater density and viscosity, therefore, it is expected that the soil hydraulic conductivity varies with temperature. Beyond this point, thermal loading induces volumetric changes for both sand and clay and may alter soil fabric. These variations might increase or decrease the intrinsic permeability of the soil. A modified temperature-controlled triaxial permeameter cell was used in this study to elevate soil temperature from 20 °C to 80 °C. Moreover, the setup was designed to control the temperature and pressure of the permeant water injected into the specimen. The hydraulic conductivity of both Ottawa sand and Kaolin clay under different confinement stresses (69 kPa to 690 kPa) was measured. Then, intrinsic permeability was calculated considering water properties variation with temperature. The results determined that, although hydraulic conductivity increases with temperature for both Ottawa sand and Kaolin clay, the intrinsic permeability of Ottawa sand reduces by 50%, while in Kaolin clay it slightly reduces when the temperature rises from 20 °C to 80 °C. Nonetheless, analyzing volumetric changes and void ratio variations for both selected soil types show a reduction in void ratio with temperature. Reduction in the void ratio can explain the lower intrinsic permeability in Ottawa sand at the elevated temperature, however in Kaolin clay despite the higher void ratio reduction, another mechanism which is the degeneration of a part of the immobile water within the structure into the mobile water plays an important role.

Zero-valent iron-modified Degussa P25-TiO2/ZnO nanocomposites (denoted as P25/Fe0/ZnO) were designed and prepared via Fe0 impregnation of P25-TiO2/ZnO and then were employed in the visible-light photocatalytic degradation of p-nitrophenol (PNP) in the presence of [K2S2O8]. Central composite design was applied for response surface modeling (RSM) to understand the influence of selected factors (pH, [Fe0] wt% and [K2S2O8] concentration) on the degradation of PNP and to determine the interaction between the factors. The maximal PNP degradation efficiency (86.9%) was obtained with P25/1.5 wt% Fe0/ZnO at 3 mg/L of [K2S2O8] concentration and pH 7.5. In addition, the RSM showed a satisfactory correlation between the experimental and predicted values of PNP degradation. The P25/Fe0/ZnO photocatalyst performance was also examined degrading methyl orange and phenol and high degradation efficiency, 82 and 99%, was achieved, respectively. The structure, morphology, light absorption and photocatalytic properties of as-prepared P25/Fe0/ZnO were studied using TEM, BET, XRD, FTIR and DRS.

The C@POM (carbon@polyoxometalate) containing H3PMo12O40 (PMo12), H5PMo10V2O40 (PMo10V2), H6PMo9V3O40 (PMo9V3), H7PMo8V4O40 (PMo8V4), H3PW12O40 (PW), and H4SiW12O40 (SiW) were prepared from natural potato as green, and cheap catalyst support source. The C@PMo10V2 was found to be a unique, effective, and eco-friendly catalyst for selective oxidation of sulfides, using 30% aq. H2O2. C@PMo10V2 composite was characterized by X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectrophotometry, zeta sizer, and zeta potential. The XRD results show that during immobilization PMo10V2 on the carbon catalyst support (CCS), the crystallite structure of PMo10V2 and CCS was not changed. The SEM results show that PMo10V2 crystals deposited on the surface CCS rods as composite nanorod structure. A variety of sulfides, sulfur-containing model and real oil were oxidized with the C@PMo10V2/H2O2 at room temperature. Recovered catalyst show excellent activity for at least four repeating cycles.

The characterization of ultra-soft clayey soil exhibits extreme challenges due to low shear strength of such material. Hence, inspecting the non-destructive electrical impedance behavior of untreated and treated ultra-soft clayey soils gains more attention. Both shear strength and electrical impedance were measured experimentally for both untreated and treated ultra-soft clayey soils. The shear strength of untreated ultra-soft clayey soil reached 0.17 kPa for 10% bentonite content, while the shear strengths increased to 0.27 kPa and 6.7 kPa for 10% bentonite content treated with 2% lime and 10% polymer, respectively. The electrical impedance of the ultra-soft clayey soil has shown a significant decrease from 1.6 kΩ to 0.607 kΩ when the bentonite content increased from 2% to 10% at a frequency of 300 kHz. The 10% lime and 10% polymer treatments have decreased the electrical impedances of ultra-soft clayey soil with 10% bentonite from 0.607 kΩ to 0.12 kΩ and 0.176 kΩ, respectively, at a frequency of 300 kHz. A new mathematical model has been accordingly proposed to model the non-destructive electrical impedance-frequency relationship for both untreated and treated ultra-soft clayey soils. The new model has shown a good agreement with experimental data with coefficient of determination (R2) up to 0.99 and root mean square error (RMSE) of 0.007 kΩ.

This paper addresses some material level test which is done on quasi-brittle and ductile materials in the laboratory. The displacement control experimental program is composed of mortar cylinders under uniaxial compression shows quasi-brittle behavior and seemingly round-section aluminum specimens under uniaxial tension represents ductile behavior. Digital Image Correlation gives full field measurement of deformation in both aluminum and mortar specimens. Likewise, calculating the relative displacement of two points located on top and bottom of virtual LVDT, which is virtually placed on the surface of the specimen, gives us the classical measure of strain. However, the deformation distribution is not uniform all over the domain of specimens mainly due to imperfect nature of experiments and measurement devices. Displacement jumps in the fracture zone of mortar specimens and strain localization in the necking area for the aluminum specimen, which are reflecting different deformation values and deformation gradients, is compared to the other regions. Since the results are inherently scattered, it is usually non-trivial to smear out the stress of material as a function of a single strain value. To overcome this uncertainty, statistical analysis could bring a meaningful way to closely look at scattered results. A large number of virtual LVDTs are placed on the surface of specimens in order to collect statistical parameters of deformation and strain. Values of mean strain, standard deviation and coeffcient of variations for each material are calculated and correlated with the failure type of the corresponding material (either brittle or ductile). The main limiters for standard deviation and coeffcient of variations for brittle and ductile failure, in pre-peak and post-peak behavior are established and presented in this paper. These limiters help us determine whether failure is brittle or ductile without determining of stress level in the material.

In order to fully understand the thermo-hydro-mechanical behavior of the geotechnical infrastructures, the effects of temperature variations on soil properties and soil behavior have to be studied. Hydraulic conductivity, strength, volume change, moisture content, and pore pressure generation and dissipation rates depend on temperature variations. Thermal loading might induce excess pore water pressure and volumetric changes. Temperature changes in the fine-grained soils will cause expansion in water and soil particles. Since the coefficient of expansion for soil particles is much smaller than that for water, a generation of pore water pressure is expected. This thermally induced pore water pressure and then its dissipation during the relaxation period results in a time dependent consolidation. Thermal consolidation in fine grained soil is more dominant and can be irreversible in normally consolidated clay. However, the volumetric changes of highly over consolidated soil caused by temperature increment is reversible by temperature reduction. In this research, a modified consolidation testing device is used to study the effect of temperature increments (e.g., increasing step by step temperature increments to 80oC) on the consolidation of fine grained soils. In another words the effect of temperature increments during the test on the consolidation process is studied. Time of applying the heating, target temperature, and initial void ratio are parameters affecting the rate and the amount of consolidation in the samples.

The wicker-like Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) was synthesized by the external magnetic field (EMF). The Pd-based catalyst with nano and the face-centered cubic (fcc) structure was obtained at room temperature without using any additive. The resulting composite was characterized. The results show that EMF has a great influence on morphology, particle size, and crystalline structure of the Pd-PVP-Fe composite. The resulting composite (Pd-PVP-Fe), was found to be an effective catalyst for the Mizoroki–Heck reaction while is exposed to EMF with the intensity at 486 µT. The reused catalyst for at least five repeating cycles, shows excellent activity.

The catalytic activity of palladium supported on magnetic nanoparticles in the amination coupling reaction of different nitrogen containing substrates with aryl halides was investigated. C–N bond formation was achieved in moderate to excellent yields and the catalyst could be separated by magnetic decantation.

We have developed a simple and efficient catalytic protocol composed of hollow palladium-poly(N-vinylpyrrolidone)-nano zero valent iron and H5PMo10V2O40 (Mo10V2) supported on Fe2O3@SiO2 core–shell nano particles, as reusable catalytic system for Suzuki coupling reaction under ligand- and base-free conditions. These reusable solid catalysts exhibited excellent activity and the methodology is applicable to diverse substrates providing good-to-excellent yields of desired products. This method has advantages of high yields, low reaction times, elimination of ligand and base, heterogeneous catalysts, and simple methodology. In order to study the role of Fe@Si–Mo10V2 in the Suzuki coupling reaction, electron transfer property of Fe@Si–Mo10V2 and Pd–PVP–Fe by means of cyclic voltammetry measurements were investigated. Moreover, this catalytic system could be recovered in a facile manner from the reaction mixture and recycled several times without any significant loss in activity. In this study, the heterogeneity of both component of our catalytic system was investigated and the content of palladium (Pd) and Mo10V2 into filtrates was evaluated quantitatively by inductively coupled plasma atomic emission spectroscopy (ICP-AES). According to the obtained results from the ICP-AES measurements, the small amount of Pd and Mo10V2 leach have been obtained.

The present study focuses on the adsorption of disperse blue 56 dyes on the surface of ZnO-magnetic/ZSM-5 as an effective and novel adsorbent with high adsorption capacity and magnetic separation capability. The best conditions to optimize the dye removal were obtained at adsorbent dosage 0.015 g, pH 3, stirring time 15 min and initial dye concentration 10−5 M to get a maximum removal percentage (>91.0 %). The magnetization saturation value of ZnO-magnetic/ZSM-5 adsorbent is 3.2 emu/g that indicating great potential for application in magnetically separation technologies. In application point of view, it was found to act as an efficient recoverable adsorbent. The results are shown that ZnO-magnetic/ZSM-5 could be reusable 3 times without significant reduction of adsorbent activity (yield of removal >) and no obvious decreases of magnetic intensity. Kinetic and isotherm models of disperse blue 56 can be well examined using the pseudo first-order model and the Freundlich isotherm based on high R2 (0.980) and R2 (0.989), respectively. The maximum adsorption capacity of disperse blue 56 obtained based on the Langmuir model was 6.23 mg g-1. Values of Freundlich isotherm parameters (n = 2.185 and Kf = 3.300 mg/g) demonstrated that the adsorption process was a normal absorption and favourable.

In the present study, heat and fluid flow of water in a vented cavity with elliptical hot obstacle is numerically investigated using Lattice Boltzmann Method (LBM). This flow is assumed to be laminar, 2D and incompressible. The main purpose in this work is to investigate the effect of utilizing porous medium on mixed convective heat transfer in an obstructed vented cavity. The simulations are performed for Richardson number of 0.1, 1 and 10, porosity of 0.5, 0.7 and 0.9, and solid-to-fluid conductivity ratios of 10, 33.3, 66.7 and 100. The results are presented by streamlines, temperature contours, and Nusselt number curves. Results show that by increasing Richardson number, due to the dominance of natural convective heat transfer compared with that of the forced case, the heat penetration in fluid layers in all areas of the cavity is increased. Moreover, as the Richardson number increases, due to limitation of forced heat transfer, the temperature gradients in the cavity rise and the growth of thermal boundary layer becomes significant. This behavior has an undesirable effect on heat transfer of hot obstacle especially around the cavity outlet and right side of the obstacle. By decreasing the cavity porosity, the areas around the hot obstacle will experience higher heat penetration into the fluid and consequently the heat transfer is reduced. In this study, the highest Nusselt number is obtained for Richardson number of Ri=0.1 and porosity of Po=0.5 and the increase in Richardson number and porosity coefficient results in reduced Nusselt number in all areas around the hot obstacle. The porosity changes have more significant effect on heat transfer in smaller Richardson numbers. This results in Nusselt number higher about 79% in best condition at conductivity ratio of 33.33 (Ri=0.1) while it changes the Nusselt number about 17.4% at conductivity ratio of 10 (Ri=10).

The objective of this paper is twofold. First, we propose two composable block solver methodologies to solve the discrete systems that arise from finite element discretizations of the double porosity/permeability (DPP) model. The DPP model, which is a four-field mathematical model, describes the flow of a single-phase incompressible fluid in a porous medium with two distinct pore-networks and with a possibility of mass transfer between them. Using the composable solvers feature available in PETSc and the finite element libraries available under the Firedrake Project, we illustrate two different ways by which one can effectively precondition these large systems of equations. Second, we employ the recently developed performance model called the Time-Accuracy-Size (TAS) spectrum to demonstrate that the proposed composable block solvers are scalable in both the parallel and algorithmic sense. Moreover, we utilize this spectrum analysis to compare the performance of three different finite element discretizations (classical mixed formulation with H(div) elements, stabilized continuous Galerkin mixed formulation, and stabilized discontinuous Galerkin mixed formulation) for the DPP model. Our performance spectrum analysis demonstrates that the composable block solvers are fine choices for any of these three finite element discretizations. Sample computer codes are provided to illustrate how one can easily implement the proposed block solver methodologies through PETSc command line options.

A Co – Fe – resol/SiO 2 nano catalyst was prepared by a simple and cheap co - precipitation method for the Fischer – Tropsch synthesis (FTS) and characterized by X - ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed reduction (TPR), Fourier transform infrared (FT - IR), energy dispersive X - ray (EDX), and N 2 adsorption – desorption. The effect of calcination conditions was investigated and it was found that the catalyst calcined at 650 °C for 6 h is almost free of resol. The TPR spectrum showed lower reduction temperatures respect to similar Co – Fe catalysts. After the Fischer – Tropsch reaction, a sintered irregular surface with lower surface area, pore volume, and pore diameter was obtained which may be due to diffusion of reactants and products into the pores. Analysis of variance (ANOVA) for FTS was carried out by the central composite design (CCD) using response surface methodology (RSM). Four operational factors namely ; pressure, H 2 /CO molar ratio, gas hourly space velocity (GHSV), and temperature were selected for design of experiments. As GHSV increases, the CO conversion and selectivity toward light hydrocarbons (LHCs) decrease while selectivity toward heavy hydrocabons (HHCs) and alcohols (ROH) increases because the contact time between the feed and catalyst surface decreases.

A catalytic system utilizing a chelate carbene ligand containing bulk tert-butyl groups is described for palladium-catalyzed Heck and Suzuki coupling reactions. The Heck reaction focused on the coupling of different aryl bromides with mono- and 1,1-disubstituted olefins while the Suzuki reaction involved the coupling of aryl bromides and phenylboronic acid to afford the corresponding biphenyls. The catalyst system performs well with low Pd(OAc)2 levels (0.025 mol% Pd). In all cases with monosubstituted olefins, the trans-configured products were obtained, while the results of Heck reaction of 1,1-disubstituted olefins exhibited a high selectivity favoring the terminal product.

High-quality and high-active one-dimensional (1-D) Fe3O4 nanostructures were synthesized via an external magnetic field (EMF) at the intensity range 0–526 μT in aqueous solution, without using any surfactant and organic solvent at room temperature. Characterization of the products was carried out using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectrophotometry (FT-IR), a laser particle size analyzer, surface area (Brunauer–Emmett–Teller, BET), and vibrating sample magnetometer (VSM). The results show that EMF at a critical adjusted intensity has a great influence on the structural features such as the morphology, particle size, surface pore size distribution, and magnetic properties of the Fe3O4 nanostructure. The morphology changed from peg-like network structures to needle-like cage structures by an exposure synthesis treatment with EMF at an intensity of 362 μT. The catalytic activity of two nanostructures prepared in the presence and absence of EMF were compared in a tricomponents reaction (TCR) for the synthesis of trisubstituted imidazoles under electromagnetic irradiation. The best results were obtained for the catalyst produced in the presence of EMF while the tricomponent reaction was carried out in the absence of EMF. This EMF condition was used for the preparation of a series of alkyl-, aryl-, and heteroaryl-substituted imidazoles from the corresponding benzoin and benzil in aqueous solution as green reaction conditions. It was found that the catalyst can be efficiently recycled and reused for several repeating cycles without significant loss of catalytic activity.

A new method was reported for the high-yield synthesis of a mononuclear Re(I) complex, fac-[Re(phen-dione)(CO)3Cl] (where phen-dione = 1,10-phenanthroline-5,6-dione). The photochemical activity of the Re(I) complex for the photoreduction of CO2 to CO was investigated under different conditions. Density functional theory (DFT) calculations were used to evaluate the photocatalytic mechanism for the photoreduction of CO2 to CO in the presence of the Re(I) complex as a photocatalyst through a detailed comparison of two potential pathways: (I) regeneration of the initial catalyst, and (II) formation of a solvent-coordinated Re(I) complex. Although the theoretical calculations reveal that the regeneration of the initial photocatalyst through the reassociation of the Re(I) cationic intermediate with Cl− is more thermodynamically favorable than the formation of a solvent-coordinated Re(I) species, the present results show that both catalytic cycles with the inclusion of solvation effects are thermodynamically favorable.