Department of Chemical Engineering

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End date: 2009Subject: search.filters.subject.Chemical Engineering

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    Microscopic Insights of Electrochemical Switching of Poly(benzimidazobenzophenanthroline) (BBL) Thin Film: A Molecular Dynamics Study
    (ACS, 2009-04) Sarbani, Ghosh; Garg, Mohit
    Carbon nanotubes typically require the use of a dispersing or stabilizing agent to prevent significant aggregation during incorporation into a polymer matrix. These additives must be strongly associated, either covalently or physically, to achieve their purpose. In this study, multi-walled carbon nanotubes (MWNTs) were dispersed into an epoxy matrix using polyethylenimine (PEI) as a dispersant that was either covalently attached to the nanotubes or physically mixed to result in only noncovalent interaction. Epoxy composites containing covalently modified MWNTs exhibited greater storage modulus and reduced electrical conductivity.
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    Comparison of Covalently and Noncovalently Functionalized Carbon Nanotubes in Epoxy
    (Wiley, 2009-04) Etika, Krishna Chitanya
    Carbon nanotubes typically require the use of a dispersing or stabilizing agent to prevent significant aggregation during incorporation into a polymer matrix. These additives must be strongly associated, either covalently or physically, to achieve their purpose. In this study, multi-walled carbon nanotubes (MWNTs) were dispersed into an epoxy matrix using polyethylenimine (PEI) as a dispersant that was either covalently attached to the nanotubes or physically mixed to result in only noncovalent interaction. Epoxy composites containing covalently modified MWNTs exhibited greater storage modulus and reduced electrical conductivity.
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    Temperature Controlled Dispersion of Carbon Nanotubes in Water with Pyrene-Functionalized Poly(N-cyclopropylacrylamide)
    (ACS, 2009) Etika, Krishna Chitanya
    Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Poly(N-cyclopropylacrylamide), containing 5 mol % pyrene-bearing repeat units (p-PNCPA), is shown to vary the dispersion state of single-walled carbon nanotubes (SWNTs) in water. This is a thermo-responsive polymer whose conformation changes with temperature, which in turn leads to changes in the nanotube dispersion state. Cryo-TEM micrographs show that SWNTs stabilized using p-PNCPA transitions from a more exfoliated to a more bundled state as the aqueous suspension temperature is raised above the lower critical solution temperature (LCST) of the polymer (∼30 °C). Viscosity measurements on SWNT/p-PNCPA aqueous suspensions show shear thinning and near Newtonian behavior at 10 and 50 °C, respectively. Drying of these suspensions produces composites whose microstructure and electrical conductivity vary with drying temperature. This behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems.
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    The influence of synergistic stabilization of carbon black and clay on the electrical and mechanical properties of epoxy composites
    (Elsiever, 2009) Etika, Krishna Chitanya
    Studies of acetone-based suspensions suggest a synergistic stabilization of clay by carbon black (CB) that involves a haloing effect (i.e., CB surrounding clay). This unique microstructural development ultimately influences the electrical and mechanical properties of epoxy composites that contain both particles. With the addition of 0.5 wt.% clay, electrical conductivity increases by an order of magnitude for CB filled epoxy (relative to composites containing no clay), but no significant improvement is observed in storage modulus. Composites containing equal concentrations of CB and clay show reduced electrical conductivity, but significant improvement in storage modulus (relative to the composites containing equal amount (wt.%) of either CB or clay alone). Both electrical conductivity and storage modulus improve in composites containing a 1:2 clay:CB (wt/wt) ratio. This synergy between CB and clay is a useful tool for simultaneously improving the electrical and mechanical properties of solution-processed composites.
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    A Framework for Implementation of Occupational Healthand Safety Management Systems in Process Industry
    (UDYOG PRAGATI JOURNAL, 2003) Kale, Samir R.
    The paper throws light on understanding the proactive role that Occupational, Health and Safety (OH&S) plays in process related unit operations. It focuses on various hazardsoccuring in workplace of a process industry and how to mitigate this hazards through theapplication of various tools that drives OH&S with the help of real life examples. It alsodescribes the implementation stages of OH&S in a process industry. A case study has beenillustrated to understand the consequences of overlooking the safety aspects. The paper concludes that inculcating safety culture right from design to development, results in reduced accident rates and keep employers and employees safe
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    Biofiltration for removal of methyl isobutyl ketone (MIBK): Experimental studies and kinetic modelling
    (Taylor & Francis, 2009-08-26) Raghuvanshi, Smita
    The present study deals with the biofiltration of methyl isobutyl ketone (MIBK), which is considered to be a highly toxic volatile organic compound. It is released from the paint and petrochemical industries and is one of the major contributors to air pollution. The biofiltration study was carried out on a lab scale for two months in the presence of acclimated mixed culture. The performance of the biofilter column was evaluated for different inlet loads of MIBK at air flow rates ranging from 0.18 to 0.3 m3 h−1. The maximum removal efficiency of 93% was obtained after 60 days of biofilter operation for an inlet MIBK concentration of 0.45 g m−3, and a microbial concentration of 2.36 × 108 CFU g−1 of packing material was obtained. This led to a study of shock loadings for 20 days, by varying the inlet MIBK load and air flow rate after every five days, to observe the behaviour of the biofilter column in removing sudden loads of MIBK. The biokinetic constants r max and K s were obtained using the Michaelis–Menten kinetics and were found to be 1.046 g m−3 and 0.115 g m−3 h−1, respectively, with a coefficient of determination (R 2) of 0.993. The obtained experimental results were validated with the Ottengraf and Van den Oever kinetic model. The critical inlet concentration, critical inlet load and biofilm thickness were also estimated using the results obtained from the model predictions.
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    Biodegradation kinetics of methyl iso-butyl ketone by acclimated mixed culture
    (Elsiever, 2009-06-26) Raghuvanshi, Smita
    Methyl iso-butyl ketone (MIBK) is a widely used volatile organic compound (VOC) which is highly toxic in nature and has significant adverse effects on human beings. The present study deals with the removal of MIBK using biodegradation by an acclimated mixed culture developed from activated sludge. The biodegradation of MIBK is studied for an initial MIBK concentration ranging from 200–700 mg l−1 in a batch mode of operation. The maximum specific growth rate achieved is 0.128 h−1 at 600 mg l−1of initial MIBK concentration. The kinetic parameters are estimated using five growth kinetic models for biodegradation of organic compounds available in the literature. The experimental data found to fit well with the Luong model (R 2 = 0.904) as compared to Haldane model (R 2 = 0.702) and Edward model (R 2 = 0.786). The coefficient of determination (R 2) obtained for the other two models, Monod and Powell models are 0.497 and 0.533, respectively. The biodegradation rate found to follow the three-half-order kinetics and the resulting kinetic parameters are reported.
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    Experimental studies and kinetic modeling for removal of methyl ethyl ketone using biofiltration
    (Elsiever, 2009-09) Raghuvanshi, Smita
    The removal of toxic methyl ethyl ketone (MEK) is studied in a lab scale biofilter packed with mixture of coal and matured compost. The biofiltration operation is divided into 5 phases for a period of 60 days followed by shock loading conditions for three weeks. The maximum removal efficiency of 95% is achieved during phase II for an inlet concentration of 0.59 g m−3, and 82–91% for the inlet concentration in the range of 0.45–1.23 g m−3 of MEK during shock loads. The Michaelis–Menten kinetic constants obtained are 0.086 g m−3 h−1 and 0.577 g m−3. The obtained experimental results are validated using Ottengraf–van den Oever model for zero-order diffusion-controlled region to understand the mechanism of biofiltration. The critical inlet concentration of MEK, critical inlet load of MEK and biofilm thickness are estimated using the results obtained from model predictions.
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    Simulation Studies on Transient Model for Biofilter operated in Periodic Mode
    (JET, 2006) Raghuvanshi, Smita
    Biofiltration of off-gases containing Volatile Organic Compounds (VOCs) is a reliable and cost effective technology for VOCs removal. Due to many inherent advantages, most of the industries operate biofilters under the periodic conditions (highly transient). Taking the importance of such operation into account, a model is developed based on the transient conditions. In this study, a Linear Driving Force (LDF) model is used, which takes into account both mechanisms (adsorption and biodegradation) involved in biofiltration process. The rate equation is given by the modified three-parameter Monod-type expression. The results obtained from the present model are validated with the experimental data and the results obtained from earlier model reported in the literature. The simulations are also carried out to understand the influence of various important parameters such as inlet VOCs concentrations, bed height and gas velocity on the biofiltration process operated in the periodic mode.
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    Modeling and Simulation of Reduction Zone of Downdraft Biomass Gasifier: Effect of Air to Fuel Ratio
    (JET, 2007) Sheth, P.N.
    Biomass mainly in the form of wood is the oldest form of energy used by humans. Biomass generally means a relatively dry solid of natural matter that has been specifically grown or has originated as waste or residue from handling such materials. The thermochemical conversion of biomass (pyrolysis, gasification, combustion) is one of the most promising non-nuclear forms of future energy. In the present study, the model reported in literature is simulated to study the effects of pyrolysis fraction on the outlet gas concentration in a downdraft biomass gasifier. It is found that the air to fuel ratio is one of the key parameters in the reduction zone of downdraft biomass gasifier. It effects the value of pyrolysis fraction in the model, and indirectly proportional to the pyrolysis fraction. Steady state composition and temperature profiles for the reduction zone of the downdraft biomass gasifier are also predicted for various values of air to fuel ratio.