Faculty Publications
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Item Synthesis and nonlinear optical characterization of copolymers containing alternating 3,4-dialkoxythiophene and 1,3,4-oxadiazolydbenzene units(2007) Udayakumar, D.; Kiran, A.J.; Vasudeva Adhikari, A.V.; Chandrasekharan, K.; Shashikala, H.D.We report the synthesis and linear and third-order nonlinear optical (NLP) characterization of two novel copolymers containing alternating 3,4-dialkoxythiophene and 1,4-bis(1,3,4-oxadiazolyl)benzene units. The copolymers were synthesized with a precursor polyhydrazide route. Both copolymers exhibited fluorescence around 430 nm under the irradiation of UV light. The NLO measurements were made with the single-beam Z-scan technique with Nd:YAG nanosecond laser pulses at 532 nm. The nonlinear refractive index of the investigated copolymers was negative, and the magnitude was as high as 10 -10 esu. The samples exhibited strong reverse saturation absorption and very good optical limiting properties at the wavelength used. The concentration dependence of third-order NLO parameters was studied. ©2007 Wiley Periodicals, Inc.Item Optimization and analysis of nickel adsorption on microwave irradiated rice husk using response surface methodology (RSM)(2009) Ganesapillai, M.G.; Iyyaswami, I.; Helen Kalavathy, M.H.; Murugesan, T.; Miranda, L.R.Background: The removal of heavy metals using adsorption techniques with low cost biosorbents is being extensively investigated. The improved adsorption is essentially due to the pores present in the adsorbent. One way of improving the porosity of the material is by irradiation of the precursor using microwaves. In the present study, the adsorption characteristics of nickel onto microwave-irradiated rice husks were studied and the process variables were optimized through response surface methodology (RSM). Result: The adsorption of nickel onto microwave-irradiated rice husk (MIRH) was found to be better than that of the raw rice husk (RRH). The kinetics of the adsorption of Ni(II) from aqueous solution onto MIRH was found to follow a pseudo-second-order model. Thermodynamic parameters such as standard Gibbs free energy (?G°), standard enthalpy (?H°), and standard entropy (?S°)were also evaluated. The thermodynamics of Ni(II) adsorption onto MIRH indicates that it is spontaneous and endothermic in nature. The response surface methodology (RSM) was employed to optimize the design parameters for the present process. Conclusion: Microwave-irradiated rice husk was found to be a suitable adsorbent for the removal of nickel(II) ions from aqueous solutions. The adsorption capacity of the rice husk was found to be 1.17 mg g-1. The optimized parameters for the current process were found as follows: adsorbent loading 2.8 g (100 mL)-1; Initial adsorbate concentration 6 mg L-1; adsorption time 210 min.; and adsorption temperature 35°C. © 2008 Society of Chemical Industry.Item An optimization study on microwave irradiated, decomposition of phenol in the presence of H2O2(2009) Prasannakumar, B.R.; Iyyaswami, I.; Murugesan, T.Background: Removal of phenol from industrial waste waters involves basic techniques namely extraction, biodegradation, photocatalytic degradation, etc. Among the available processes, the oxidation of phenols using H2O2 is a suitable alternative because of low cost and high oxidizing power. The application of an oxidation process for the decomposition of stable organic compounds in waste water leads to the total degradation of the compounds rather than transferring from one form to another. Since oxidation using Fenton's reagent ismore dependent on pH, in this present work it was proposed to use H2O2 coupled with microwave irradiation. The effects of initial phenol concentration, microwave power and the irradiation time on the amount of decomposition were studied. Results: In the present work experiments were conducted to estimate the percentage degradation of phenol for different initial concentrations of phenol (100, 200, 300, 400 and 500 mg L-1), microwave power input (180, 360, 540, 720 and 900 W) for different irradiation times. The kinetics of the degradation process were examined through experimental data and the decomposition rate follows first-order kinetics. Response surface methodology (RSM) was employed to optimize the design parameters for the present process. The interaction effect between the variables and the effect of interaction on to the responses (percentage decomposition of phenol) of the process was analysed and discussed in detail. The optimum values for the design parameters of the process were evaluated (initial phenol concentration 300 mg L-1, microwave power output 668 W, and microwave irradiation time 60 s, giving phenol degradation 82.39%) through RSM by differential approximation, and were confirmed by experiment. Conclusion: The decomposition of phenol was carried out using H2O2 coupled with microwave irradiation for different initial phenol concentrations, microwave power input and irradiation times. The phenol degradation process follows first-order kinetics. Optimization of the process was carried out through RSM by forming a design matrix using CCD. The optimized conditions were validated using experiments. The information is of value for the scale up of the oxidation process for the removal of phenol from wastewater. © 2008 Society of Chemical Industry.Item Microwave-assisted batch synthesis of Pongamia biodiesel(2010) Venkatesh Kamath, H.; Iyyaswami, I.; Saidutta, M.B.Background: The major bottleneck of biodiesel synthesis is its cost and this is mainly attributed to the feedstock material. Pongamia pinnata oil is a nonedible oil that is available in plenty in India and has negligible applications. Several methods of synthesis have been established, each having their own advantages and disadvantages. Results & discussion: Biodiesel from high-free fatty acid, nonedible, Pongamia oil was synthesized under microwave irradiation with single- and two-step methods. Experimental investigations showed that although the single-step method had a high yield (80%), the acid value of biodiesel was quite high. Hence, the two-step method seems to be a better approach as it yielded 90%, with 1:10 oil:methanol molar ratio and 1 wt% KOH. Along with a decrease in the reaction time to 4-5 min, separation time was also decreased by at least 90%. A conventional heating method was employed to compare the effects of microwave irradiation on biodiesel synthesis. Conclusion: The results indicate significant improvement in the yield, reaction time and processing time of biodiesel under microwave irradiation. The synthesis of Pongamia biodiesel under microwave irradiation could perhaps lead to cost effective and faster technology in countries such as India. © 2010 Future Science Ltd.Item Optimization of two step karanja biodiesel synthesis under microwave irradiation(2011) Venkatesh Kamath, H.; Iyyaswami, I.; Saidutta, M.B.The free fatty acid of crude karanja oil (Pongamia pinnata) was reduced and biodiesel was synthesized from pretreated oil under microwave irradiation. The process variables such as irradiation time, methanol-oil ratio and sulfuric acid concentration for pretreatment step; irradiation time, methanol-oil ratio and KOH concentration were optimized through the Box-Behnken experimental design. The free fatty acid of crude karanja oil was reduced to 1.11 ± 0.07% with an optimal combination of 190 s irradiation time (180 W), 33.83 (w/w)% methanol-oil ratio and 3.73 (w/w)% sulfuric acid concentration. An optimal combination of 150 s irradiation time, 33.4 (w/w)% methanol-oil ratio and 1.33 (w/w)% KOH concentration yielded 89.9 ± 0.3% biodiesel. The model was validated by conducting experiments at optimal design conditions. The present work confirmed that the microwave energy has a significant effect on esterification and transesterification reaction. © 2010 Elsevier B.V. All rights reserved.Item Synthesis and desalination performance of Ar+-N+ irradiated polysulfone based new NF membrane(2011) Hegde, C.; Isloor, A.M.; Padaki, M.; Wanichapichart, P.; Liangdeng, Y.In the last few years, membrane technology has gained more attention from polymer chemists throughout the globe. Nowadays, surface modification of membrane is very useful in biotechnology and food science. In the present investigation, we have synthesized polysulfone based composite nanofiltration (NF) membranes, and characterized these membranes by FT-IR, SEM and membrane performance studies. Surface plasma treatment was carried out by irradiation with argon and nitrogen beams in suitable conditions. It was observed that nitrogen beam caused surface roughness that was more severe than the Ar beam. After irradiation, water contact angle was slightly increased. For pure water permeability, flux increased linearly with the operating pressure. However, for the salt solution, the flux was decreased marginally and salt rejection increased after irradiation due to surface modification. The modification effect was characterized in terms of contact angle, AFM employed roughness measurement and dielectric property. It revealed that irradiated NF membranes showed higher salt rejection and lower flux as compared to the nonmodified membranes. Accordingly, the roughness of the membrane surface intensively affected the performance of RO membrane. © 2010 Elsevier B.V.Item Microwave-assisted batch and continuous transesterification of karanja oil: Process variables optimization and effectiveness of irradiation: Microwave-assisted transesterification of karanja oil(Springer Verlag service@springer.de, 2013) Iyyaswami, I.; Venkatesh Kamath, V.K.; Yarramreddy, S.R.; Malur Bharathaiyengar, S.The technological advancement in biodiesel production has been the focus area for last the few years and microwave-assisted biodiesel synthesis is one such promising new technology. In the present investigation, microwave irradiation was used to produce biodiesel from non-edible Karanja (Pongamia pinnata) oil in batch and continuous mode. Experiments were conducted to understand the effect of volume of the reaction mixture, irradiation time, and irradiation power on the yield of biodiesel. To increase the effectiveness of the microwave irradiation, biodiesel was synthesized in a continuous tubular reactor at two different holdup volumes. The effect of process parameters viz., irradiation time, irradiation power, and methanol to oil ratio were optimized using Box-Behnken experimental design. The effectiveness of microwave irradiation for the different process conditions have been represented through an effectiveness factor. The results reinforce the advantages of continuous processes over batch processes for the production of biodiesel. The properties of biodiesel, namely ester content, density, viscosity, acid value, and cetane index were analyzed and found to be within the limits as prescribed in ASTM D6751-09 standards. The experimental results that have been obtained in this study would be very useful in the scale-up of the microwave-assisted biodiesel process. © 2013 Springer-Verlag Berlin Heidelberg.Item Solar light induced photocatalytic degradation of Reactive Blue 220 (RB-220) dye with highly efficient Ag@TiO2 core-shell nanoparticles: A comparison with UV photocatalysis(2014) Khanna, A.; Shetty K, K.Ag core-TiO2 shell (Ag@TiO2) structured nanoparticles with Ag to TiO2 molar ratio of 1:1.7 were synthesized using one pot synthesis method and post calcination was carried out at 450°C for 3h to convert it from amorphous to crystalline form. The Ag core and TiO2 shell formation was confirmed by TEM and AFM. The particle size analysis revealed the average size of Ag@TiO2 as approximately around 30nm. EDS spectra showed the presence of O, Ag, and Ti elements. The improvement in optical properties was proved by DRS which showed significant red shift by Ag core in visible region. Ag@TiO2 exhibited better photocatalytic activity as compared to Degussa P25-TiO2, synthesized TiO2, and the Ag doped TiO2 photocatalysts under UV and solar light irradiation for degradation of Reactive Blue 220 (RB-220) dye. Higher rate of photocatalysis of RB-220 with Ag@TiO2 was obtained under solar light irradiation as compared to UV light irradiation, confirming the capability of the catalyst to absorb both UV and visible light. The kinetics of degradation of dye was found to follow modified Langmuir Hinshelwood (L-H) kinetic model. Ag@TiO2 can be recycled without much decline in the efficacy. Ag@TiO2 has been found to be the effective photocatalyst for degradation of water contaminated with azo dyes under both UV and solar light irradiations. © 2013 Elsevier Ltd.Item Influence of Sn doping on photoluminescence and photoelectrochemical properties of ZnO nanorod arrays(Kluwer Academic Publishers, 2014) Santhosh Kumar, A.S.; Huang, N.M.; Nagaraja, H.S.Herein, the nanostructured Sn containing ZnO is directly synthesized on the surface of substrate by modified sol gel approach under low-temperature condition. The samples are characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman-scattering, photoluminescence (PL) and photoelectrochemical analyses. The SEM micrographs show that the undoped and 1 at. % Sn doped films are composed of nanorods and the concentration of 2 at. % Sn doping hinders the rod-like structure's growth and modulates into granular nature. The investigations of XRD reveal that the synthesized undoped and Sn doped ZnO nanorods possess a perfect hexagonal growth habit of wurtzite zinc oxide, along the (002) direction of preference. The Raman spectra demonstrate that the vibrational mode of E1(LO), which is very weak in undoped and 1at. % Sn doped ZnO, is strongly enhanced with 2 at. % Sn doping into ZnO lattice. PL spectra show that strong UV emission in pure and 1 at. % Sn doped ZnO, while there is dominant green emission in 2 at. % Sn doped ZnO. Moreover, all the samples are photo electrochemically active and exhibit the highest photocurrent of 28 ?A for the 1 at. % Sn doped ZnO nanorod arrays in 0.2M Na2SO4 electrolyte, on light irradiation. Time dependent photoresponse tests are carried out by measuring the photocurrent under chopped light irradiation. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.Item An optimization study of microwave assisted extraction of oil from oily sludge using response surface methodology(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Kumar, B.; Raj Mohan, B.Petroleum oily sludge, a hazardous waste, generated by the refineries and at the production sites in huge quantities comprises of a mixture of petroleum hydrocarbons, asphaltenes, long chain paraffinic wax, waste water, sediments and metals. The present study is aimed to recover oil from the petroleum oily sludge using n-heptane as the solvent in microwave assisted solvent extraction process and to optimize the process variables for the recovery of oil from the oily sludge. The simultaneous effects of process variables such as irradiation time (2 - 10 minutes), solvent to sludge ratio (40 – 80 wt %), reactant volume (100 – 300 ml) and microwave power (80 – 400 W) on the recovery of oil were evaluated. A central composite design (CCD) and response surface methodology (RSM) were used for the optimization of the extraction process. Based on the CCD, quadratic model was developed to correlate the extraction process variables with the responses and the model was analysed using appropriate statistical method (ANOVA). Optimization of process variables shows that the maximum recovery of oil was about 88.6% at 100 ml of reactant volume with microwave power output of 351 W at 6.5 minutes of irradiation time with 58.99% of nheptane to sludge ratio. © 2014 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.