Effect Of Activation Parameters Research Articles

MHD nanofluid flow between porous convergent-divergent channel with velocity slip and nanoparticle aggregation

The aggregation of nanoparticles is a major phenomenon having broad consequences in many fields. In order to fully utilize the capabilities of nanoparticles in a variety of applications and to evaluate the effects that they will have on the environment and biological systems, it is crucial to comprehend and manage aggregation. To develop and improve nanoparticle-based technology, researchers are still learning more about the aggregation processes. Thus, the present study investigates the combined effects of velocity slip and nanoparticle aggregation on Heat transfer (HT) analysis of MHD nanofluid (i.e., TiO2-C2H6O2) flow between porous convergent, divergent channel. The modified Krieger–Dougarty and Maxwell–Bruggeman models were utilized for nanoparticle aggregation. The modeling is based on nonlinear PDEs such as continuity, momentum, and heat equations. These equations are transformed into a system of nonlinear ODEs using similarity transformations and then solved numerically and analytically. The analytical solution has been constructed using the ADM method. The present results in particular cases are compared to results obtained by the HAM- package and by the Runge- Kutta Fehlberg 4th–5th order (RKF-45) for validation. The effects of active parameters on the velocity, temperature, concentration, skin friction, and Nusselt numbers are investigated. It is found that nanoparticle aggregation can limit fluid velocity in converging channels by increasing flow resistance through aggregate formation. Individual nanoparticles generate friction and lower velocity, while aggregated nanoparticles boost fluid density and velocity. In addition, it is found that the magnetic field lowers skin friction and increases HT due to Lorentz force, while porosity increases friction and HT. Nanoparticle concentration inversely affects friction, increasing friction without aggregation and decreasing friction with aggregation, with the HT rate rising with increased nanoparticle concentrations.

Irreversibility of Al2O3-Ag hybrid nanoparticles in mixture base fluid on microchannel with variable viscosity, buoyancy forces, and suction/injection effects: An analytical study

The development of inherent irreversibility in the system is caused by single phase Poiseuille flow considering hybrid nanoparticles (Al2O3-Ag) and mixture fluid (water and ethylene glycol H2O50%-C2H6O250%) in the upright microchannel with unequal viscosity. Taking into account the buoyancy force, suction/injection at the walls, and the form factor and geometry of the nanoparticles. The modeling is based on nonlinear PDEs such as continuity, momentum, and heat equations, which are then transformed to a system of nonlinear ODEs using similarity transformations and solved numerically and analytically. The analytical solution was built using the Differential Transform Method (DTM), and the current results in specific cases are compared to results obtained by the HAM-based Mathematica package, the Runge-Kutta Fehlberg 4th-5th order (RKF45), and those available in literature. The effects of active parameters are investigated on the velocity and temperature, entropy generation and Bejan number. The outcomes of the present analysis reveal that the nanoparticles volume fraction, thermal radiation and Biot number acts to enhance the cooling of the system through the release of thermal energy. in addition, the enhancement in variable viscosity parameter, causes a rise in the irreversibility rate, which in turn boosts the rates of entropy generation and Bejan number. On the other hand, Irreversibility due to heat transfer is dominant in the centerline of the microchannel, while fluid friction irreversibility dominates its walls.

Removal behaviors of phenol from aqueous solution using industrial coal sludge-derived porous carbon sorbent

Porous activated carbon was prepared from industrial coal sludge (CS) by one-step pyrolysis and KHCO3 activation, and applied to remove phenol from aqueous phase. The effects of activation parameters on the characteristics of activated carbon and phenol adsorption performance were investigated. CSAC-900 (obtained at 900 °C) has abundant pores and shows three-dimensional porous structure. The adsorption process of phenol on CSAC-900 are controlled by various mechanisms, such as π-π interaction, hydrogen bond and pore filling. The isotherm fitting agrees with Langmuir model. The maximum adsorption capacity of phenol on CSAC-900 is 305.83 mg/g. The positive ΔH and negative ΔG illustrate the adsorption of phenol onto CSAC-900 is a spontaneous endothermic reaction. Compared with commercial activated carbon materials, the adsorption of phenol by CSAC-900 exhibits significant advantages in adsorption capacity and adsorption rate, and it can also be regenerated and recycled.

Thermal activation, characterization and performance evaluation of Ethiopian bentonite for sodium removal.

Bentonite is one of the clay materials that have important characteristics and is applicable to construction and for different industrial uses. Treatment of this material to enhance some of its physicochemical properties to suit the desired applicability has been a focus research area. In this work, natural bentonite from Warseisso, Afar region, Ethiopia was activated with thermal treatment. The raw and treated bentonites were then characterized using SEM, FTIR, XRD, BET, and cation exchange capacity. The effects of activation parameters (time and temperature) on its physiochemical properties and its performance for the removal of sodium ions from water were investigated. Bentonite activated for 6 h at 300 °C showed a maximum specific surface area of 81.74 m2/g while the raw one showed 57.6 m2/g. However, the cation exchange capacity value of the raw bentonite was found to be 82.1 meq/100 g while the value was reduced to 67.2 meq/100 g for treated bentonite with high specific surface area. To check the performance of the activated bentonite for desalination application, batch adsorption of sodium from synthetically produced sodium chloride solution was made. A sodium removal performance of 10% was achieved with treated bentonite at the maximum specific surface area.

Effects of activation parameters on Zeolitic imidazolate framework JUC-160-derived, nitrogen-doped hierarchical nanoporous carbon and its volatile iodine capture properties

Despite its importance in the nuclear industry, the uncontrollable use and/or accidental release of iodine in the environment pose serious threats to human health and endanger wildlife. Therefore, effective removal of radioiodine from various environmental media is necessary to circumvent its adverse effect. Herein, we report on an excellent and highly efficient capture of iodine by ZIF (JUC-160)-derived ultra-porous carbon. The ultra-porous carbon, obtained through KOH activation at high temperature, displayed unprecedented iodine capture properties with uptake capacities of 1567 mg g−1 and 821 wt.% in the aqueous and vapor phases, respectively. Various conditions including activation temperature and residency time effects on material properties and uptake performances were evaluated. The results showed that iodine uptake increased with increasing activation temperature; while activation time beyond 60 min was not favorable because the carbon materials were completely gasified. Kinetics and Isotherm fitting with the experimental data was done to assess sorption behavior of the derived carbon materials and their interactions with iodine. The results showed that chemisorption was the dominant medium through which iodine was captured as confirmed by both pseudo-second order and Langmuir models. Furthermore, the main mechanism involved in the process was mainly attributed to electron donor-acceptor interactions wherein the oxygen-containing functional groups and nitrogen active sorption sites of the carbon materials acted as electron donors. This work provides insight into optimizing KOH activation temperature and residency time for best performance of iodine adsorbents.

Synthesis of Porous Material from Coal Gasification Fine Slag Residual Carbon and Its Application in Removal of Methylene Blue.

A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared using gasification fine slag foam flotation obtained carbon residue (GFSF) as raw material and an adsorbent to carry out an adsorption test on waste liquid containing methylene blue (MB). The effects of activation parameters (GFSF/KOH ratio mass ratio, activation temperature, and activation time) on the cation exchange capacity (CEC) of GFSA were investigated. The total specific surface area and pore volume of GSFA with the highest CEC were 574.02 m2/g and 0.467 cm3/g, respectively. The degree of pore formation had an important effect on CEC. The maximum adsorption capacity of GFSA on MB was 19.18 mg/g in the MB adsorption test. The effects of pH, adsorption time, amount of adsorbent, and initial MB concentration on adsorption efficiency were studied. Langmuir isotherm and quasi second-order kinetic model have a good fitting effect on the adsorption isotherm and kinetic model of MB.

Correlation verification of process factors and harmful gas adsorption properties for optimization of physical activation parameters of PAN-based carbon fibers

In this study, the effects of activation parameters in the steam activation of polyacrylonitrile-based carbon fibers on pore formation properties were investigated. The activation temperature was used as a primary parameter, and the activation time was adjusted for each condition to obtain similar levels of activation yields. Based on the activation yield of activated carbon fibers (ACFs), the activation energy was calculated as 142.2kJ/mole. As a result of BET analysis, it was confirmed that the specific surface area and pore volume of ACFs were improved as the activation temperature was increased. The sample treated at 850̊ during 45min showed a high specific surface area (1041.9m2/g) and a pore volume (0.49cm3/g). This developed pore structures improved the gas adsorption properties of ACFs.

Ignition of Mechanically Activated Aluminum Powders Doped with Metal Oxides

AbstractUse of mechanical milling to increase micrometric powder reactivity is of interest due to several intrinsic advantages of this technique (e. g. versatility and safety). In this work, 30 μm propulsion‐grade aluminum has been activated with and without metal oxides. The powders so obtained were characterized in terms of particle size distribution, metal content, morphology, and ignition temperature. This last parameter represents a good indicator to rate the reaction properties of powders and the effects of activation parameters on the final product. All the ingredients containing metal oxides feature an enhanced reactivity as a consequence of both additives and modification of particle morphology.

Entropy generation in two phase model for simulating flow and heat transfer of carbon nanotubes between rotating stretchable disks with cubic autocatalysis chemical reaction

Entropy generation in two phase model for simulating flow and heat transfer of carbon nanotubes in water based fluid in rotating system with the effects of magnetic field, joule heating, thermal radiation, convective boundary conditions and homogeneous–heterogeneous reactions with cubic autocatalysis is examined. The governing equations of the problem are transformed into nonlinear ordinary differential equations by introducing the appropriate similarity transformations which are solved analytically by the homotopy analysis method (HAM). The effects of active parameters are depicted graphically and illustrated. Validation of the present results are shown through Table 2. The study furnishes an overview of the modifications, how they can be detected and quantified using parameters and how this information provides insight into their role in other sciences.

Facile Fabrication of Nickel/Heazlewoodite@Carbon Nanosheets and their Superior Catalytic Performance of 4‐Nitrophenol Reduction

AbstractA facile molten salt method was utilized for the synthesis of carbon anchored nickel/heazlewoodite nanoparticles (Ni/Ni3S2@C nanosheets) with potassium humate as the carbon and sulfur source and NaCl as template. The morphology, particle size and crystallinity of the products were characterized by various techniques containing TEM, FE‐SEM and XRD. Furthermore, the mesoporous Ni/Ni3S2@C own easy accessibility of active sites and high surface area (149.04 m2 g−1). Thus, the as‐prepared Ni/Ni3S2@C exhibited prominent performance for catalytic reduction of 4‐nitrophenol (4‐NP). Catalytic reduction of other nitrophenols (NPs) were also tested which can prove that the catalyst own selectivity on reduction of NPs. For durability, the property of the catalyst does not decrease obviously after five cycles. More significant correlations concerning effect of activation parameters (Ea=37.21 kJ mol−1) on 4‐NP reduction were scrutinized and discussed. Hence, we provide a facile method for fabrication of metal/metal sulfide@C which own better dispersity, small dimension and excellent catalytic performance for further studies.

Leaching behaviour of mechano-chemically activated bio-oxidised refractory flotation gold concentrates

In this paper, the leaching behaviour of mechano-chemically activated, refractory, bio-oxidised flotation gold concentrates has been investigated. In particular, the effect of activation parameters (e.g., milling time and speed, and ball to pulp ratio) and cognate physico-chemical changes on the impact of the refractory mineral components in the ore was studied. The results showed that mechano-chemical activation led to reduction in the average particle size and increased surface area and reagent consumption in tandem with remarkable mineral amorphisation of the bio-oxidised products. The gold yield increased by a maximum of ~1.8 times after 24 h of cyanide leaching, irrespective of the magnitude of milling speed, milling time, ball to pulp ratio and the degree of mineral amorphisation. Furthermore, the increase in reagent consumption was consistent with increasing mineral particle stress and exposure of reactive gangue mineral phases (e.g., sulphate minerals), a factor that least influenced the gold yield. It appears that the improvement in gold extraction efficacy was due to gold surface cleaning, creation of pores/crevices that are linked to gold sites, and disintegration of gold-gangue mineral agglomerates that encapsulated gold particles. The findings were consistent with the nature of refractoriness and necessary for understanding ways of mitigating gold refractoriness in bio-oxidised flotation concentrates.

Magnetohydrodynamics flow and heat transfer of Cu-water nanofluid through a partially porous wavy channel

In this paper, the lattice Boltzmann method is applied to investigate the effects of uniform vertical magnetic field on thermo-hydrodynamics of nanofluid in a partially porous channel. Cu-water nanofluid with constant pressure gradient is forced to flow into the channel while the top wall is heated by constant heat flux and bottom wavy wall of the channel is insulated against heat. The porous media is modeled using the Brinkman–Forchheimer model. Good agreements with the previous results verify that the selected numerical method is a capable method for simulating magnetic fluids in a porous media. The effects of active parameters, i.e. solid volume fraction of nanoparticles, pressure gradient, magnetic field and permeability of the porous layer, on thermo-hydrodynamics of flow are examined. The results reveal that the Nusselt number is an increasing function of nanoparticle volume fraction, Hartmann number, pressure gradient and Darcy number, although the effect of Darcy numbers and pressure gradient on the temperature profile are more noticeable than others.

Preparation and characterization of mesoporous activated carbons from waste watermelon rind by using the chemical activation method with zinc chloride

Waste watermelon rind was analyzed as a precursor for preparing activated carbons by using a one-step chemical activation process by zinc chloride. The effects of activation parameters, i.e., carbonization temperature, impregnation ratio, and impregnation time on the properties of the final products were tested in detail. The resultant activated carbons were characterized using elemental analysis, the Brunauer–Emmet–Teller method, pore property analysis, N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, the point of zero charge, Boehm titration method and scanning electron microscopy. The maximal Brunauer–Emmett–Teller surface area of the resultant activated carbon, produced by using the impregnation (ZnCl2/dried watermelon rind) ratio of 2/1 at the carbonization temperature of 700°C with the residence time of 60min, was 1156m2/g. Upon using the impregnation ratio of 3/1 at the carbonization temperature of 600°C with the residence time of 60min, the maximal total pore volume, which also contains the highest mesopore volume, was 1.41cm3/g.

Simulation of Ferrofluid Flow for Magnetic Drug Targeting Using the Lattice Boltzmann Method

Abstract Influence of a spatially varying magnetic field on Fe3O4-plasma nanofluid flow in a vessel as a targeted drug delivery system is investigated. Combined effects of ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) are considered in mathematic models. The lattice Boltzmann method is applied to solve the governing equations. Effects of active parameters, such as the Reynolds number and magnetic number on the flow characteristics, have been examined. Results indicate that the presence of the magnetic field affects considerably the flow field. Back flow occurs near the region where the magnetic source is located. Also, it can be found that the skin friction coefficient is a decreasing function of the Reynolds number and magnetic number.

Optimized removal of Reactive Navy Blue SP-BR by organo-montmorillonite based adsorbents through central composite design

In this study, the Montmorillonite K10 (MMT-K10) was activated by sulfuric acid, followed by modification with cetyltrimethylammonium bromide (CTAB). The central composite design (CCD) was applied to optimize the activation process of MMT-K10. The effects of activation parameters (acid concentration, temperature, and contact time) on the decolorization efficiency of MMT-K10 (R%) were studied, and the optimum conditions were defined. The optimum values of input variables were found to be 50°C (temperature), 3.6mol/L (acid concentration) and 2.2h (contact time). The predicted and experimental values of responses were in reasonable agreement with each other (R2=0.968 and adj-R2=0.940). The activated and modified MMT-K10 was characterized by FTIR, XRD, SEM and TEM techniques. The FT-IR analysis confirmed that acid-activation and modification caused the intercalation of CTAB in MMT-K10 layers and increase in specific surface area.

Preparation of activated graphene and effect of activation parameters on electrochemical capacitance

Activation parameters such as temperature and the amount of potassium hydroxide (KOH) were varied during the synthesis of activated microwave-exfoliated graphite oxide (a-MEGO) and the effects of these parameters on the specific surface area of a-MEGO and electrochemical capacitance of a-MEGO electrodes were investigated. At 800°C and a KOH/MEGO mass ratio of 6.5, a maximum specific surface area of 3100m2/g was obtained and a high specific capacitance of 172F/g (at 1A/g constant current and 3.5V maximal voltage) was measured in a two-electrode cell with a-MEGO electrodes in an organic electrolyte.

High voltage SnO2 varistors prepared from nanocrystalline powders

In this study, SnO2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 °C in comparison varistors prepared from conventional powders. Breakdown voltage and nonlinear coefficient were increased up to 24 kV/cm and 45 respectively.