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21.
Gannavarapu Venkata Vamsi Aditya Bhagavatula Padma Pujitha Nalluri Chitti Babu Paladugu Venkateswarlu 《Korean Journal of Chemical Engineering》2012,29(1):64-71
The biosorption of chromium from an aqueous solution onto Erythrina Variegata Orientalis leaf powder was investigated in batch operations. The equilibrium agitation time was 180 min. The extent of chromium biosorption
increased from 74.2% to 86.4% with decrease in biosorbent size from 150 to 45 μm for a dosage of 30 g/L. The biosorption decreased
from 99.1 (0.45 mg/g) to 45.5% (1.64 mg/g) with an increase in chromium initial concentration (C
o
) from 22.5 to 180 mg/L. The extent of biosorption was maximum at pH=3. The experimental data were well explained by Langmuir
and Redlich-Peterson isotherm models. The biosorption data followed second-order kinetics with a rate constant of 0.078 g/mg-min
for 50 g/L of 45 μm size biosorbent. The biosorption was exothermic and feasible. The biosorption was tending towards irreversibility
with increasing temperature. 相似文献
22.
Flame aerosol synthesis is one of the commonly employed techniques for producing ultra fine particles of commodity chemicals such as titanium dioxide, silicon dioxide and carbon black. Large volumes of these materials are produced in industrial flame reactors. Particle size distribution of product powder is the most important variable and it depends strongly on flame dynamics inside the reactor, which in turn is a function of input process variables such as reactant flow rate and concentration, flow rates of air, fuel and the carrier gas and the burner geometry. A coupled flame dynamics–monodisperse population balance model for nanoparticle synthesis in an aerosol flame reactor is presented here. The flame dynamics was simulated using the commercial computational fluid dynamics software CFX and the particle population dynamics was represented using a monodisperse population balance model for continuous processes that predicts the evolution of particle number concentration, particle volume and surface area. The model was tested with published experimental data for synthesis of silica nanoparticles using different burner configurations and with different reactor operating conditions. The model predictions for radial flame temperature profiles and for the effects of process variables like precursor concentration and oxygen flow rate on particle specific surface area and mean diameter are in close agreement with published experimental data. 相似文献
23.
P. Sampath Brijesh Kakarla Raghava Reddy C. Venkata Reddy Nagaraj P. Shetti Raghavendra V. Kulkarni Anjanapura V. Raghu 《化学工程与技术》2020,43(7):1240-1248
Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency. 相似文献
24.
Self‐assembled centimetre‐sized rods obtained in the oxidation of o‐phenylenediamine and aniline 下载免费PDF全文
Venkata Sai Sriram Mosali Graham A Bowmaker Melvin Gerard Paul A Kilmartin Jadranka Travas‐Sejdic Zoran D Zujovic 《Polymer International》2015,64(9):1135-1141
Morphologically well‐defined rods of approximately 1 cm in length are effectively and economically obtained by mixing ortho‐phenylenediamine (30 mmol L?1) with ammonium persulfate (12.5 mmol L?1) in an acidic solution (0.37 mol L?1 HCl) at room temperature with and without the presence of 50 mmol L?1 aniline. These self‐assembled, morphologically uniform products can be potentially scaled up and used as morphological templates to fabricate well‐defined structures of other materials such as conducting polymers. The products were characterized using Raman, UV‐visible, high‐resolution NMR (1H and 13C) and mass spectroscopies, X‐ray diffraction, scanning electron microscopy and elemental analysis. Apart from certain differences in visual appearance and in X‐ray diffractograms, other analytical data suggest that there are no structural changes upon addition of aniline into the reaction mixture. NMR and mass spectra imply that all syntheses carried out either with or without aniline result in a mixture of two products, attributed to 2,3‐phenazinediamine and 3‐aminophenazin‐2‐ol. A formation mechanism based on hydrogen bonding and π–π stacking has been proposed. © 2015 Society of Chemical Industry 相似文献
25.
In this work the role played by the presence of moisture and pH during ozone bleaching of grey cotton fabric and the design features of the ozone application chamber are reported. The results are explained with the help of a simplified model. The dyeing and resin finishing properties of ozone-bleached fabric are compared with those of hydrogen peroxide-bleached fabric. 相似文献
26.
Biswanath Mahanty Kannan Pakshirajan Veeranki Venkata Dasu 《Polycyclic Aromatic Compounds》2013,33(1):56-73
A novel method for preparation of pyrene encapsulated alginate beads for controlled release delivery of pyrene is reported in this study. Five different bead types that varied on the organic phase for pyrene delivery, presence or absence of polyvinyl alcohol (PVA) and boric acid treatment were prepared. Based on the pyrene release profile, silicone oil encapsulated in PVA-alginate bead was selected where encapsulation efficiency was more than 99% without any solvent leakage. Silicone oil encapsulation was further confirmed in microscopy observations. Pyrene release behavior from the beads was explained by a diffusion controlled first order release (R2 > 0.96). Reusability of this bead was demonstrated, where pyrene was loaded from an external medium in a non-destructive way. Application of the system was finally established in a biodegradation study using Mycobacterium frederiksbergense, where simultaneous release and removal of pyrene along with appearance of pyrene metabolites was observed. 相似文献
27.
Karna Narayana Prasanna Rani Thella Prathap Kumar Tulasi Sri Venkata Ramana Neeharika Bankupalli Satyavathi Rachapudi Badari Narayana Prasad 《European Journal of Lipid Science and Technology》2013,115(6):691-697
Kinetic studies have been carried out on the esterification of free fatty acids (FFAs) in jatropha oil with methanol in the presence of sulphuric acid catalyst at 5 and 10 wt% concentrations relative to free fatty acids (0.4–0.8 wt% relative to oil) and methanol–FFA mole ratios ranging from 20:1 to 80:1. It has been found that a 60:1 methanol–FFA mole ratio and 5 wt% catalyst at 60°C and 500 rpm or above provided a final acid value lower than 1 mg KOH/g oil within 60 min. A kinetic model has been proposed with second‐order kinetics for both the forward and backward reactions. The effect of temperature on the reaction rate constants and equilibrium constant has been determined using Arrhenius and von't Hoff equations, respectively. The heat of reaction was found to be ?11.102 kJ/mol. 相似文献
28.
Venkata Giri Kolli Shem O. Ogadhoh Steve M. Abel Francis Gadala‐Maria Thanasis D. Papathanasiou 《Polymer Engineering and Science》2002,42(2):403-412
We present the results of an investigation of particle motion behind the advancing free surface during the filling of an initially empty tube with a viscoelastic fluid. Particle motion in the vicinity of an advancing free surface (the fountain flow region) is of significance in a number of processes used to form composite materials, notably injection and compression molding. This motion determines, to a large extent, the distribution of the reinforcing phase in the molded part. We show experimentally that an isolated spherical particle moves behind the interface in characteristic orbits, remaining in close proximity to the advancing free surface. This is in stark contrast to what happens in a Newtonian fluid. In that case, the particle is deposited on the tube walls by the fountain flow and never again reaches the faster moving free surface. The particle motion behind the interface is modeled with a combination of equations that describe the advection of the particle due to convective/fountain flow and its lateral migration due to viscoelasticity. This model neglects the finite size of the particle and is thus unable to capture the full details of the observed motion. However, the qualitative agreement between the experimental results and the modeling predictions suggests that the observed particle motion is the result of the combined effect of viscoelasticity and fountain flow. 相似文献
29.
Barlev R. Nagawkar Venkata P. Kotrike Alberto Passalacqua Shankar Subramaniam 《American Institute of Chemical Engineers》2022,68(6):e17639
A mixing index based on solid volume fraction fields is developed for gas-solid flows. Conventional mixing indices are based on particle realizations of granular mixing and are applicable to experimental data or discrete element method simulations. However, these indices cannot be used as-is for multifluid models, and an index for characterizing mixing in gas-solid flows from continuous fields is needed. The performance of the new mixing index is tested in two applications. The first is a 3D simulation of the mixing of biomass and sand in a fluidized bed reactor, and the second is a 2D simulation of binary particle segregation in a fluidized bed. The simulations are performed using OpenFOAM®. The mixing index is used to quantify gas-solid mixing using solid volume fractions and solid-solid mixing using solid fractions. The formulation of conventional mixing indices is extended to be used with solid volume fractions fields, and methods for performance improvement are presented. 相似文献
30.
Venkata Sundeep Seesala Santanu Dhara 《Journal of the American Ceramic Society》2022,105(8):5131-5139
For successful osseointegration of load-bearing implants, an improved bone–implant contact area through a trabecular porous surface resulting in minimized stress shielding effect is highly desirable. We propose a novel strategy of green net shaping a ceramic dough, combined with a reticular foam replica method and gradient coating, to fabricate biomimetic porosity in a customizable ceramic dental implant for the first time. About 85 vol% porosity and 300–600-μm pore size were evident in microCT and electron microscopy of the sintered samples, suitable for bone ingrowth. Excellent integrity at the interface along with homogeneous distribution of secondary alumina phase in zirconia matrix was achieved, despite the difference in the green state powder loading between the dough and the slurry. 相似文献