Mohd Sobri Takriff

Visible light photocatalytic activity of Fe3+-doped ZnO nanoparticle prepared via sol–gel technique

The optical properties of a ZnO photocatalyst were enhanced with various dopant concentrations of Fe(3+). Doped ZnO nanoparticles were synthesized via a sol-gel method without the use of capping agents or surfactants and was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that ZnO has a wurtzite, hexagonal structure and that the Fe(3+) ions were well incorporated into the ZnO crystal lattice. As the Fe(3+) concentration increased from 0.25 wt.% to 1 wt.%, the crystal size decreased in comparison with the undoped ZnO. The spectral absorption shifts of the visible light region (red shift) and the band gap decreases for each Fe-ZnO sample were investigated. The photocatalytic activities of the ZnO and Fe-ZnO samples were evaluated based on the degradation of 2-chlorophenol in aqueous solution under solar radiation. The samples with a small concentration of Fe(3+) ions showed enhanced photocatalytic activity with an optimal maximum performance at 0.5 wt.%. The results indicated that toxicity removal of 2-chlorophenol at same line of degradation efficiency. Small crystallite size and low band gap were attributed to high activities of Fe-ZnO samples under various concentrations of Fe(3+) ions compared to undoped ZnO.

An overview: biomolecules from microalgae for animal feed and aquaculture

Despite being more popular for biofuel, microalgae have gained a lot of attention as a source of biomolecules and biomass for feed purposes. Algae farming can be established using land as well as sea and strategies can be designed in order to gain the products of specific interest in the optimal way. A general overview of the contributions of Algae to meet the requirements of nutrients in animal/aquaculture feed is presented in this study. In addition to its applications in animal/aquaculture feed, algae can produce a number of biomolecules including astaxanthin, lutein, beta-carotene, chlorophyll, phycobiliprotein, Polyunsaturated Fatty Acids (PUFAs), beta-1,3-glucan, and pharmaceutical and nutraceutical compounds which have been reviewed with respect to their commercial importance and current status. The review is further extended to highlight the adequate utilization of value added products in the feeds for livestock, poultry and aquaculture (with emphasis in shrimp farming).

Antimicrobial and antioxidant activities of new metal complexes derived from 3-aminocoumarin.

3-Aminocoumarin (L) has been synthesized and used as a ligand for the formation of Cr(III), Ni(II), and Cu(II) complexes. The chemical structures were characterized using different spectroscopic methods. The elemental analyses revealed that the complexes where M=Ni(II) and Cu(II) have the general formulae [ML2Cl2], while the Cr(III) complex has the formula [CrL2Cl2]Cl. The molar conductance data reveal that all the metal chelates, except the Cr(III) one, are non-electrolytes. From the magnetic and UV-Visible spectra, it is found that these complexes have octahedral structures. The stability for the prepared complexes was studied theoretically using Density Function Theory. The total energy for the complexes was calculated and it was shown that the copper complex is the most stable one. Complexes were tested against selected types of microbial organisms and showed significant activities. The free radical scavenging activity of metal complexes have been determined by measuring their interaction with the stable free radical DPPH and all the compounds have shown encouraging antioxidant activities.

Predicting flux and rejection of multicomponent salts mixture in nanofiltration membranes

Abstract This paper presents a modified Donnan-Steric-Pore model (DSPM) to predict the rejection of mixture of NaCI:Na2SO4 in nanofiltration (NF) membrane based on the extended Nernst-Planck equation with the incorporation of charge and steric effects for the transport of ions inside the membrane and incorporation of concentration polarization effect for mixture of ions/solutes. With this approach, the permeate flux can be calculated based on the concentration of ions at the membrane surface. The membrane performance was modelled using three parameters namely; effective pore radius, rp , effective ratio of embrane thickness to porosity, Δx/Ak, and the effective charge density, Xd. The simulation results shows that the model can predict the tendencies and patterns of rejection and flux reduction behaviour reasonably well for system containing NaCl:Na2SO4. The model can be used as a preliminary tool to assess the rejection capability as well as the flux behaviour of NF membranes in mixtures of solutions. For future works, the model can be improved further to account for non-ideal as well as real mixture solutions.

Methane decomposition over unsupported mesoporous nickel ferrites: effect of reaction temperature on the catalytic activity and properties of the produced nanocarbon

The thermocatalytic decomposition of methane is a promising route for the simultaneous production of COx-free hydrogen and nanocarbon. In this work, unsupported mesoporous nickel ferrites were successfully synthesized via a facile co-precipitation method and used to catalyze the decomposition of methane. The as-prepared nickel ferrites were characterized by using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption and temperature-programmed reduction analysis. The NiFe2O4 catalyst was found to be highly phase pure and porous. The porosity is resulted from the inter-aggregation of more or less spherical nickel ferrite particles. Moreover, these particles had a total specific surface area of 21 m2 g−1 with a monomodal mesoporous distribution. The catalytic performance of the catalysts was evaluated for methane decomposition at various reaction temperatures, and the dependence of the properties of the nanocarbon on reaction temperature was investigated in detail. Upon increasing the temperature from 700 °C to 900 °C, the yields of hydrogen and nanocarbon increased significantly. A maximum hydrogen yield of 68% was observed over the catalyst at 900 °C within the first 20 minutes of time on the stream. After that, its activity slightly declined, and at the end of 360 minutes, the hydrogen yield was measured to be 47%. At 700 °C and 800 °C, maximum hydrogen yields of 41% and 58% were achieved within 90 minutes of time on stream. No deactivation was observed for the catalyst at any of the temperatures tested, which was attributed to the formation of NiFe bimetallic alloys, which in turn increased the carbon diffusion rate and prevented deactivation of the catalyst. The effect of reaction temperature on the crystalline, morphological and graphitization properties of the deposited nanocarbon was studied. Metal-encapsulated carbon particles with a nano-onion-like appearance and multi-layered graphene sheets were deposited over the catalyst at 700 °C and 900 °C, respectively. Moreover, the crystallinity and graphitization degree of the deposited nanocarbon was found to increase with increasing reaction temperature.

The role of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol in the inhibition of nickel–aluminum bronze alloy corrosion: electrochemical and DFT studies

Inhibition of corrosion of nickel–aluminum bronze alloy (NAB) by use of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol (APTT) was investigated by monitoring weight loss and open-circuit potentials (OCP), and by use of electrochemical impedance spectroscopy (EIS). Quantum chemical data were calculated by use of the density functional theory (DFT) model. Results showed that APTT inhibits corrosion of NAB alloy fairly well. The efficiency of inhibition increases with increasing concentration of APTT, and adsorption of the inhibitor obeys the Langmuir adsorption isotherm model. Negative values of adsorption free energy indicate chemical adsorption is spontaneous. The theoretical study showed that sulfur and nitrogen atoms (S, N7 and N8) were the reactive sites.

Heat Transfer Enhancement of Laminar Nanofluids Flow in a Circular Tube Fitted with Parabolic-Cut Twisted Tape Inserts

Numerical investigation has been carried out on heat transfer and friction factor characteristics of copper-water nanofluid flow in a constant heat-fluxed tube with the existence of new configuration of vortex generator using Computational Fluid Dynamics (CFD) simulation. Two types of swirl flow generator: Classical twisted tape (CTT) and Parabolic-cut twisted tape (PCT) with a different twist ratio (y = 2.93, 3.91 and 4.89) and different cut depth (w = 0.5, 1.0 and 1.5 cm) with 2% and 4% volume concentration of CuO nanofluid were used for simulation. The effect of different parameters such as flow Reynolds number, twist ratio, cut depth and nanofluid were considered. The results show that the enhancement of heat transfer rate and the friction factor induced by the Classical (CTT) and Parabolic-cut (PCT) inserts increases with twist ratio and cut depth decreases. The results also revealed that the heat transfer enhancement increases with an increase in the volume fraction of the CuO nanoparticle. Furthermore, the twisted tape with twist ratio (y = 2.93) and cut depth w = 0.5 cm offered 10% enhancement of the average Nusselt number with significant increases in friction factor than those of Classical twisted tape.

Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y = 2.93) and different cut depths (w = 0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y = 2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratio y = 2.93 and cut depth w = 0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

CFD Simulation of Heat Transfer and Friction Factor Augmentation in a Circular Tube Fitted with Elliptic-Cut Twisted Tape Inserts

This paper presents the application of a mathematical model for simulation of the swirling flow in a tube induced by elliptic-cut and classical twist tape inserts. Effects of the twist ratio (.93, 3.91, and 4.89) and cut depth (, 0.8, and 1.4 cm) on heat transfer enhancement (Nu) and friction factor (f) in laminar flow are numerically investigated. The simulation is carried out using commercial CFD package (FLUENT-6.3.26) to grasp the physical behaviour of the thermal and fluid flows of a constant heat-fluxed tube fitted with elliptic-cut twist tape in the laminar flow regime for the Reynolds number ranging from 200 to 2100. The simulated results matched the literature correlations of plain tube for validation with 8% variation for Nusselt number and 10% for friction factor. The results show that the heat transfer rate and friction factor in the tube equipped with elliptic-cut twist tape (ECT) are significantly higher than those fitted with classical twist tape (CTT). Moreover the results also reveal that the Nusselt number and the friction factor in the tube with elliptic-cut twisted tape (ECT) increase with decreasing twist ratios (y) and cut depths (w).

Interstage backmixing of an aerated multistage, mechanically‐agitated, compartmented column

Interstage backmixing of an air-water system in a compartmented column was determined experimentally. The effects of impeller speed, impeller diameter and both superficial liquid velocity and superficial gas velocity through the interstage opening were investigated. Both counter current and co-current flow of air and water in the column were investigated. As air superficial velocity through the opening increased from zero, the interstage backmixing significantly decreased initially, reached a minimum, then increased slowly to a maximum after which it decreased continually with further increase in superficial gas velocity.