► Activated carbon coated with magnetite nanoparticles was synthesized from biomass. ► Nano magnetization achieved in a single step process and well characterized. ► Adsorbent showed better ...superparamagnetism compared to reported elsewhere. ► New nano magnetite adsorbent effectively removed toxic hexavalent chromium. ► Continuous column reactor was designed and the parameters evaluated.
Activated carbon prepared from corn cob biomass, magnetized by magnetite nanoparticles (MCCAC) was used for the adsorption of hexavalent chromium from aqueous solution. The adsorbent was characterized by SEM, TEM, XRD, VSM, surface functionality and zero-point charge. The iron oxide nanoparticles were of 50nm sizes and the saturation magnetization value for the adsorbent is 48.43emu/g. Adsorption was maximum at pH 2. Isotherm data were modeled using Langmuir, Freundlich and Temkin isotherm. The prepared MCCAC had a heterogeneous surface. The maximum monolayer adsorption capacity was 57.37mg/g. Kinetic studies were carried out and the data fitted the pseudo second-order equation. The mechanism of the adsorption process was studied by incorporating the kinetic data with intraparticle diffusion model, Bangham equation and Boyd plot. The adsorption was by chemisorption and the external mass transfer was the rate-determining step. A micro column was designed and the basic column parameters were estimated.
In the present investigation an attempt was made to degrade organic pollutants in the textile effluent by homogeneous and heterogeneous Fenton systems. Experiments were carried out under the batch as ...well as under the continuous operating conditions. The effect of time, pH, H2O2 concentration, FeSO4.7H2O concentration and the mass of mesoporous activated carbon on the degradation of organics in the wastewater were critically examined. The kinetic constants and the thermodynamic parameters for the oxidation of organics in wastewater were determined. The quantitative removal of COD, BOD and TOC from the wastewater was evaluated. The degradation of organics in textile wastewater was confirmed through FT-IR, UV–Visible spectroscopy, and cyclic voltammetry.
Schematic flow diagram for integrated homogenous and heterogeneous Fenton oxidation of textile wastewater. Display omitted
► Mesoporous activated carbon was used as a heterogeneous catalyst in this study. ► COD was removed excess in this study over homogeneous Fenton oxidation by 30%. ► The mesoporous activated carbon enhances the rate of the oxidation reaction. ► This process involves minimum sludge production and low electrical energy input. ► The mesoporous activated carbon was active even after 18 cycles in this study.
In the present study,
Juglans regia
shells were used to prepare activated carbon by acid treatment method.
J
.
regia
shell-based activated carbon was used for the adsorption of two synthetic dyes ...namely, a basic dye malachite green and an acid dye amido black 10B. The prepared adsorbent was crushed and sieved to three different mesh sizes 100, 600 and 1,000 μm. The adsorbent was characterized by scanning electron microscopy, surface acidity and zero-point charge. Batch experiments were carried out by varying the parameters like initial aqueous phase pH, adsorbent dosage and initial dye concentration. The equilibrium data were tested with Langmuir, Freundlich, Redlich–Peterson and Sips isotherm at three different temperatures 293, 300 and 313 K and it was found that the Freundlich isotherm best fitted the adsorption of both the dyes. Kinetic data were tested with pseudo first-order model and pseudo second-order model. The mechanism for the adsorption of both the dyes onto the adsorbent was studied by fitting the kinetic data with intraparticle diffusion model and Boyd plot. External mass transfer was found to be the rate-determining step. Based on the ionic nature of the adsorbates, the extent of film diffusion and intraparticle diffusion varied; both being system specific. Thermodynamic parameters were also calculated. Finally, the process parameters of each adsorption system were compared to develop the understanding of the best suitable system.
In the present article, an attempt has been made to synthesize binary Cu-20 wt.% Mo immiscible alloy by mechanical alloying of pure elemental Cu and Mo powders. The aforesaid alloy was prepared by ...commercial planetary ball mill (PBM) and indigenous dual drive planetary ball mill (DDPBM). Both the milling techniques resulted in homogenous distribution of fine and hard Mo particles in soft copper matrix. The crystallite size of the alloy milled in DDPBM exhibited a minimum value of 12 nm after 40 h of milling which was confirmed using XRD and TEM. Further, the mechanically alloyed powders were cold pressed and sintered at different temperatures between 900 and 1050 °C for 1 h. The sintered Cu-20wt.%Mo alloy showed a good combination of coefficient of thermal expansion, electrical conductivity and hardness in spite of having a density 93%.
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•We report synthesis of Cu-20wt.%Mo immiscible alloy by mechanical alloying.•Nanocrystalline structure (<20 nm) of powder is found.•The optimum sintering temperature is found to be 1000 °C.•We find fine and uniform distribution of Mo in Cu matrix.•Bulk density, electrical conductivity and CTE of sintered specimens are reported.
Growth factors are essential in cellular signaling for migration, proliferation, differentiation and maturation. Sustainable delivery of therapeutic as well as functional proteins is largely required ...in the pharmacological and regenerative medicine. Here we have prepared chitosan nanoparticles (CNP) and incorporated growth factors such as epidermal growth factor (EGF) and fibroblast growth factor (FGF), either individually or in combination, which could ultimately be impregnated into engineered tissue construct. CNP was characterized by Fourier transform infrared (FTIR) spectroscopy, Zeta sizer and high resolution transmission electron microscope (HRTEM). The particles were in the size range of 50–100
nm with round and flat shape. The release kinetics of both EGF and FGF incorporated CNP showed the release of growth factors in a sustained manner. Growth factors incorporated nanoparticles did not show any toxicity against fibroblasts up to 4
mg/ml culture medium. Increased proliferation of fibroblasts
in vitro evidenced the delivery of growth factors from CNP for cellular signaling. Western blotting results also revealed the poor inflammatory response showing less expression of proinflammatory cytokines such as IL-6 and TNFα in the macrophage cell line J774 A-1.
The highly convoluted interface separating the turbulent and non-turbulent regions in a turbulent mixing layer is experimentally investigated using the particle image velocimetry (PIV) technique. The ...mixing layer was generated using a fine screen/mesh in one half of the test section of a low-speed wind tunnel. The PIV data, which were acquired with high spatial resolution in the self-similar regime of the flow, allow us to identify the turbulent/non-turbulent interface (TNTI) using a suitable threshold value of the absolute spanwise vorticity,
$|\unicodeSTIX{x1D714}_{z}|$
. The threshold values for the top and bottom interfaces of the mixing layer are found to be different, and the probability density function (PDF) of the interface position for both the interfaces is found to follow the Gaussian distribution. Interestingly, the PDF of the interface orientation reveals two clear peaks, and this is attributed to the sustained large-scale motions in a mixing layer, compared to the other free-shear flows, as is also substantiated by further analyses such as the linear stochastic estimation and the conditional analysis of the transverse velocity profile. The linear stochastic analysis also shows the presence of large vorticity structures of the order of the Taylor microscale at the mean TNTI location in a mixing layer. Furthermore, the present work reveals that, using the spanwise component of vorticity alone, we can experimentally identify and estimate the thickness of the viscous superlayer from the conditional profiles of the diffusion term and the correlation coefficient of the dissipation and the diffusion terms in the enstropy transport equation. The present value of the viscous superlayer thickness of
$5\unicodeSTIX{x1D702}$
–
$6\unicodeSTIX{x1D702}$
(where
$\unicodeSTIX{x1D702}$
is the Kolmogorov length scale) compares well with the values reported in the literature for other shear flows. Although both the interfaces are found to behave like a fractal with a dimension of 1.3 in two dimensions, one can find dominant length scales of the order of the thickness of the viscous superlayer, the thickness of the TNTI and the width of the mixing layer from the pre-multiplied power spectra of the autocorrelation functions of the interface curvature, the normal velocity and the interface position, along the TNTI, respectively. In addition, we find that the TNTI characteristics do not show significant dependence on the velocity ratios and
$Re_{\unicodeSTIX{x1D706}}$
considered in the present study. Furthermore, the conditional transverse velocity profiles indicate that the entrainment characteristics for the upper and lower TNTIs may be asymmetric in nature.
Computed Tomography (CT) is one of the effective imaging modality in medical sciences that assist in diagnosing various pathologies inside the human body. Despite considerable advancement in ...acquisition speed, signal to noise ratio and image resolution of computed tomography imaging technology, CT images are still affected by noise and artifacts. A tradeoff between the amount of noise reduced and conservation of genuine image details has to be made in such a way that it enhances the clinically relevant image content. Therefore, noise reduction in medical images is an important and challenging task, as it helps to improve the performance of other image processing procedures such as segmentation or classification to perform better diagnosis by clinicians. Different techniques have been suggested in the literature on denoising of CT images, and each technique has its own presumptions, benefits, and drawbacks. To the best of our knowledge, no survey paper was found in the literature that compares the performance of various denoising techniques for CT images. This study aims to compare the capabilities of several notable and contemporary denoising techniques in the presence of different types of noise present in abdominal CT images. This comparative analysis helps to determine the most suitable denoising technique for practitioners and researchers that can be used in real life scenarios. Furthermore, the advantages and disadvantages of considered denoising methods have also been discussed along with some recommendations for further research in this area.
An experimental study on localized secondary instability of unsteady streamwise streaks in bypass boundary layer transition under an elevated level of free-stream turbulence has been carried out ...mainly using the particle image velocimetry (PIV) technique. Simultaneous orthogonal dual-plane PIV measurements were performed for a concurrent examination of the transitional flow features in both wall-normal and spanwise planes. These quantitative and simultaneous visualizations clearly show the wall-normal view of a low-speed streak undergoing sinuous/varicose motion in the spanwise plane. An oscillating shear layer in the wall-normal plane is found to be associated with the sinuous/varicose streak oscillation in the spanwise plane. Further, these measurements indicate that a localized secondary instability wavepacket can originate near the boundary layer edge. The time-resolved PIV measurements in the wall-normal plane clearly show how an instability develops on a lifted-up inclined shear layer and leads to flow breakdown. The estimated wavelength and convection velocity of such instabilities are found to compare well with those calculated from the one-dimensional linear stability analysis of the spatially averaged velocity profiles associated with the lifted-up shear layers. The time-resolved PIV measurements in the spanwise plane also facilitate quantitative visualizations of sinuous and varicose instabilities. These measurements experimentally confirm that a varicose instability at the juncture of an incoming high-speed streak and a downstream low-speed streak can eventually lead to the formation of lambda structures. The estimated convection velocity, wavelength and growth rate of these instabilities are found to be consistent with the numerical results reported in the literature. Moreover, the streak secondary instability is found to be apparent in the velocity contours, while the estimated streak amplitude is approximately 30 % of the free-stream velocity.
Responses of a geometry-induced separation bubble (GISB) and a pressure-induced separation bubble (PISB) at enhanced levels of free-stream turbulence (FST) have experimentally been investigated for a ...comparative study using the particle image velocimetry (PIV) technique. The outlines of separation bubbles based on the dividing streamlines are self-similar for different levels of FST and Reynolds numbers. The spectral analyses of the time-resolved PIV data show that the vortex shedding frequency of a separated shear layer remains unchanged for the GISB cases even with an enhanced level of FST. In contrast, it is different for the PISB cases. We propose a criterion that determines whether the frequency will remain the same even for the cases with FST. Linear stability analyses reveal that the inviscid-inflectional instability dominates the transition process, and the linear stages of transition are not completely bypassed even at an enhanced level of FST. The most amplified frequencies, while scaling with the displacement thickness and the boundary layer edge velocity, collapse in a single curve for all the cases. Furthermore, measurements in the spanwise plane show that the streamwise velocity streak/Klebanof mode at an enhanced level of FST is not a general flow feature for all types of separation bubbles. However, at an enhanced level of FST for the PISB case, the boundary layer streaks are found to distort the two-dimensional vortex structure associated with the Kelvin–Helmholtz instability, eventually leading to a three-dimensional $\varLambda$-like structure in the spanwise plane.
•TiO2 NPs cytotoxicity at low exposure levels (≤1μg/mL) to freshwater algae.•ROS generation, NP adsorption and internalization contributors to toxicity.•Observational evidence of genotoxicity by ...nanoparticles in an algal cell.•Reduced bioavailability thus detoxification of NPs by microalgae.•Possible role of EPS in detoxification.
In the current study, two aspects concerning (i) the cytotoxicity potential of TiO2 nanoparticles (NPs) toward freshwater algal isolate Scenedesmus obliquus and (ii) the potential detoxification of NPs by the microalgae were assessed under light (UV-illumination) and dark conditions at low exposure levels (≤1μg/mL), using sterile freshwater as the test medium. The statistically significant reduction in cell viability, increase in reactive oxygen species production and membrane permeability (light vs. dark) suggested photo-induced toxicity of TiO2 NPs. The electron micrographs demonstrated adsorption of the NPs onto the cell surface and substantiated their internalization/uptake. The fluorescence micrographs and the confocal laser scanning (CLSM) images suggested the absence of a definite/intact nucleus in the light treated cells pointing toward the probable genotoxic effects of NPs. In a separate three cycle experiment, a continuous decrease in the cytotoxicity was observed, whereas, at the end of each cycle only fresh algae were added to the supernatant containing NPs from the previous cycle. The decreasing concentrations of the NPs in the subsequent cycles owing to agglomeration–sedimentation processes exacerbated by the algal interactions played a crucial role in the detoxification. In addition, the exo-polymeric substances produced by the cells could have rendered the available NPs less reactive, thereby, enhancing the detoxification effects.
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