1. Ph.D Theses
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Item Studies on Rotating Packed Disc Bioreactor(National Institute of Technology Karnataka, Surathkal, 2021) Kalnake, Rohit P.; Raval, Keyur.; Murthy, D. V. R.A novel rotating packed disc bioreactor (RPDB) with the maximum working volume of 65 liter is designed for biological waste water treatment. A hollow disc with radial vanes mounted on the disc was a novel design of this contactor. Stimulus-response experiments were conducted in the contactor to understand liquid mixing behavior under different operating conditions. The recycle stream was also used in the operation of the contactor. The disc design and recycle ratio had marked influence on the mixing behavior. A mathematical model was developed for the flow behavior under recycle and a good agreement was found between the model and experimental results. Moreover, the surface area available in the RPDB was about 4 times more than the surface area available in a standard rotating biological contactor (RBC) operating at similar conditions. The modified design characterized in terms of oxygen volumetric mass transfer coefficient (kLa), in the physical gas–liquid system. The oxygen volumetric mass transfer coefficients (kLa) obtained in this bioreactor are about eight times higher than the similar size of the conventional rotating biological contactors at similar operating conditions. The dimensionless empirical model is developed, by incorporating the operating parameters. In RPDB, mixed cultures of white-rot fungi (WRF), namely, P.chrysosporium and T.versicolor are used to degrade reactive black-5 (RB-5) under different rotational speeds as well as recycle ratios. Degradation mechanism of Reactive Black -5 is critically discussed and intermediate products following P.chrysosporium and T.versicolor are identified using LC-MS. The decolourization efficiency of more than 90% and chemical oxygen demand (COD) reduction of more than 85% was achieved in continuous operation. The recycle stream improved COD reduction by about 15% as compared to that without recycle. The rate of COD removal was 737.9 mg/L/h at 30 rpm and 9.75 recycle ratio in the continuous operation, which is the highest removal rate reported for a synthetic RB-5 effluent in a continuous bioreactor of size 65 liter so far in the literature.Item Thermophysical and Thermochemical Behaviour of Coal and Biomass during Chemical Looping Combustion(National Institute of Technology Karnataka, Surathkal, 2021) S, Pragadeesh K.; Regupathi, I.; D, Ruben Sudhakar.Thermal power plants burning fossil fuels are the major anthropogenic sources of carbon dioxide emissions into the atmosphere. Chemical Looping Combustion (CLC) is a promising fuel conversion technology for inherent carbon capture with a low energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC has drawbacks like loss of unconverted char and gaseous combustibles. The utilization of large solid fuel particles (in mm-sizes) potentially overcomes these problems and also reduces the energy involved in size reduction. The thermophysical and thermochemical changes involved during the conversion of these large-sized particles are large in magnitude and of greater significance. Thus, they along with the fuels’ thermochemical changes become critical inputs for the effective design of process equipment. This study is aimed at (i) gaining a qualitative understanding of the progressive thermophysical and thermochemical changes during fuel conversion and (ii) quantifying the influence of various operating parameters on the same. Thermochemical changes, namely devolatilization, char conversion, carbon transformations, and the thermophysical behaviour in terms of primary and secondary fragmentation, shrinkage, and microstructural changes are studied using single-particle experiments in fluidized bed insitu-gasification CLC conditions. Two types of Indian coals, one type of Indonesian coal and one type of carbon-neutral biomass (fuel wood), of three different sizes in the range of +8-25 mm are used in this study. Natural hematite is the oxygen carrier bed material used (in the size range of +250-425 μm), with steam as the fluidization-cum-gasification agent at 2.5 times the minimum fluidization velocity. The experiments are conducted at three different bed temperatures of 800, 875 and 950 oC. This work is comprised of six different experimental programs, viz. (i) development of a new method to determine devolatilization time in flameless FB-CLC conditions, called ‘Colour Indistinction Method (CIM)’, (ii) devolatilization and char yield experiments, (iii) experiments of primary fragmentation during devolatilization (iv) char conversion and char fragmentation (secondary) experiments, (v) char reactivity experiments using thermogravimetry, and (vi) char structural analysis using instrumental techniques. CIM is developed based on the observation of particle disappearance in the bed at the end of devolatilization and validated using standard diagnostic methods such as residual-volatile measurements and particle-centre temperature profilometry. CIM produced reliable results within the error range of -7.57 to +3.70 %. The devolatilization experiments revealed that the larger particles have a relatively lower amount of volatile release. However, increasing the bed temperature enhances the volatile release rate as well as the quantity of release (up to 12% in coals; 30% in biomass). With the decrease in sphericity (seen in flake coal particles), a maximum of 56% reduction in devolatilization time is noticed. A correlation for determining devolatilization time under the CLC environment is developed, with a coefficient of determination of 0.95. Char yield is found to be strongly influenced by operating bed temperature, but it is a weak function of particle size and shape. Shrinkage in biomass is witnessed for all sizes, with an effective reduction of 31-52% in initial particle volume. Char conversion times of fuels increase by 60 to 170% when particle size is increased by 2 to 2.5- folds, while an increase in bed temperature by 150 oC caused a reduction of 42 to 86%. It is also understood that if the fixed carbon content is higher than the ash content in fuel, intensive fragmentation occurs and brings down the char conversion time. Primary and secondary fragmentation phenomena are quantified using various indicators such as probability of fragmentation events, frequency and timing of fragmentation, number of fragments, fragmentation index and particle size distribution of fragments at different residence times. The intensity of primary fragmentation increases with the increase in particle size and bed temperature, while it decreases with the increase in compressive strength. Only a maximum of 60% of the tested particles undergo fragmentation, irrespective of fuels. High-volatile Indian coal and biomass, respectively, are the most and least susceptible fuels to primary fragmentation irrespective of particle size and bed temperature. Indian coals are found to fragment in the earlier stages of conversion, thus becoming a dominant factor in shortening the overall fuel conversion time. Unlike during devolatilization, the largest sized particles of all the tested fuels experience secondary fragmentation. Among the different bed temperatures studied, 950 oC is found to be the most favourable for char conversion and fragmentation. Regardless of fuel type and feed size, the inception of char fragmentation is noticed in the very first quarter of conversion time, indicating its substantial effect on the char conversion time, and therefore, it becomes necessary to carefully incorporate this size reduction with respect to time in the char conversion models. Percolative mode of fragmentation is noticed in the final quarter of char conversion, except for high-ash Indian coal particles. A minimum critical char size exists below which char weakening does not yield breakage, whose values vary between 4.4 and 14.2 mm, depending on fuel type and feed size. Fuel type is found to be the prime influencer of fuel conversion and comminution phenomena, followed by particle size and operating bed temperature. This study establishes that large fuel particles up to 25 mm can be used in CLC systems without any prior size reduction, except in the case of high-ash Indian coal. Isothermal char reactivity studies using TGA show that samples exhibit high reactivity if char preparation is done at low temperatures for high-volatile fuels and at high temperatures for low-volatile fuels. Peak reactivity is noticed during the initial stages of char conversion regime for all coals and in later stages for biomass samples. Char micrographs show mesoporous char formation with pore size of about 2-4 nm in all fuels, during the course of char conversion. Electron dispersive studies indicate that the high volatile Indian coal retains Ca throughout the conversion period, whereas biomass chars retain the catalytic species like K and Ca. Raman spectroscopic analyses show that graphitic carbon structures are selective towards the steam atmosphere, while defective carbon structures are relatively more selective towards CO2.Item Photocatalytic Degradation of Diclofenac using Different Mixed Oxide Catalysts(National Institute of Technology Karnataka, Surathkal, 2021) Mugunthan, E.; Saidutta, M. B.; Jagadeeshbabu, P. E.Elimination of pharmaceutical compounds and their metabolites from the aquatic systems has been a tedious process. The various photocatalytic process using TiO2 as semiconductor photocatalysts has enormous potential to cope with the challenges in the removal of pharmaceutical compounds. However, the TiO2-mediated photocatalytic water treatment suffers from the faster rate of recombination and wide bandgap energy corresponding to UV light. Coupling with other semiconductor oxides has reportedly reduced the recombination rate and drawbacks of the short excitation range. In the present work, the degradation of diclofenac in the photocatalytic system is carried out by using different mixed oxide catalysts prepared by hydrothermal method. The heterojunction mixed oxide catalysts can improve the photocatalytic activity by reducing the recombination rate of charge carriers and enhanced the excitation ability of the coupled catalysts in the visible light region. A series of mixed oxide catalysts were prepared with different molar concentrations of TiO2-SnO2, TiO2-WO3, ZnO-WO3 and TiO2-CdS and were characterized by XRD, TEM, BET surface area and UV spectrophotometric analyses. Initially, the performance of a series of TiO2-SnO2 mixed oxide catalysts was studied. The photocatalytic efficiency was analyzed in the degradation of diclofenac and the degradation kinetics were extensively investigated. The influence of various parameters such as initial drug concentration, pH and catalyst loading was also studied. The TiO2-WO3 mixed oxide catalysts were tested for its photocatalytic efficiency and the results suggested that the series of prepared mixed oxide catalysts exhibited better catalytic activity than the pure TiO2 under visible light irradiation. The diclofenac degradation using ZnO-WO3 heterojunction catalysts under visible light irradiation were evaluated and the synthesized ZnO-WO3 mixed oxide catalyst produced better performance than the individual components of the photocatalyst. Degradation of diclofenac using TiO2-CdS mixed oxides shows that the presence of the optimum amount of CdS in the coupled heterostructure exhibited higher photocatalytic efficiency under visible light. Comparing the performance of all the mixed oxide catalysts, TiO2-WO3 mixed oxide catalysts displayed the best catalytic activity among others under optimum operating conditions. Degradation experiment data of all the mixed oxide catalysts well fitted to pseudo-first-order reaction and the rate constants were determined. The photocatalytic degradation of diclofenac was greatly affected by initial pH, catalyst dosage and initial diclofenac concentration. The degradation was highly effective under the acidic condition for all the prepared coupled photocatalysts and the surface charge property of photocatalysts played an important role in the adsorption of drug diclofenac onto the catalyst surface. The degradation reaction mechanisms of the mixed oxide catalysts were studied and it must be noted that the hydroxyl radicals and photogenerated holes were the main active species in the diclofenac degradation process. The charge transfer between heterostructure photocatalysts has been confirmed by the photoluminescence studies. LCMS was used to analyze the various degradation products formed during the irradiation and it is revealed that several MS peaks corresponding to partially degraded products were observed during the course of photocatalytic degradation of diclofenac. Mainly these observed degradation products were preceded by the attack of •OH radicals and hydroxylation reactions which was further followed by decarboxylation, dechlorination and C-N cleavage reactions.Item Computational Investigation of Hydrodynamics, Mixing and Crystallization in a Batch Stirred Vessel(National Institute of Technology Karnataka, Surathkal, 2021) Falleiro, Lister Herington.; Ali, B Ashraf.In this work, the hydrodynamics, mixing and suspension quality of solids are numerically investigated using computational fluid dynamics (CFD). The transient CFD simulations are performed to obtain the flow field. Here multiple reference frame and sliding mesh approach are used to predict the flow field along with the standard k-ε turbulence model. The velocity field is analyzed spatially and temporally, and liquid circulation is calculated at various impeller speeds to find an optimum impeller speed. To improve the flow field in a batch stirred vessel, various draft tube baffle configurations are introduced. The optimum baffle system (DTB-IV) is identified that supports liquid circulation, mixing and suspension of solids in the batch stirred vessel. It is found that suspension quality is strongly dependent on the prevailing hydrodynamics in the stirred vessel. Further, the optimised baffled stirred vessel (DTB-IV) is used to carry out the cooling crystallisation process. The primary difficulty in the design and scale-up of the crystallization process is the lack of understanding of the flow field, growth and nucleation at different scales. Here, the performance of an unbaffled stirred vessel is compared with a baffled stirred vessel system. To predict crystal size distribution (CSD) in batch stirred vessel system, the population balance equation (PBE) is used. The PBE is solved using the quadrature method of moments. The PBE accounts for both the size and the number of the particles, and it is coupled with the CFD model. This coupled algorithm integrates solubility data, nucleation and growth kinetics. To examine the crystallization process in a batch stirred vessel, potassium dihydrogen phosphate – water system is chosen. This is analyzed for unbaffled and baffled batch stirred vessel to quantify the growth and nucleation rates of the crystals. Further, the effect of seed mass, its size and temperature on the crystallization process is investigated. The results showed that baffled stirred vessel is more advantageous and supports the crystallization process.Item A Study on Sintering Behaviour of Praseodymium Doped Ceria Based SOFC Electrolytes(National Institute of Technology Karnataka, Surathkal, 2021) Shajahan, Irfana.; Dasari, Hari Prasad.The present study explores the sintering kinetic behaviour of the Praseodymium doped ceria (PDC, Ce0.9Pr0.1O2) based Solid Oxide Fuel Cell (SOFC) electrolyte materials synthesized by various methods like the EDTA-citrate method, Microwave assisted co-precipitation method (using solvents like ethanol, water and iso – propyl alcohol) and room temperature co-precipitation method and are characterized by X- Ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) analysis and Dilatometer studies. By synthesis approach, the sintering temperature of the PDC electrolyte materials is drastically decreased from 1500°C to 1100°C by achieving unimodal shrinkage rate behaviour at a much lower temperature from 1460°C to 765°C and successfully achieved single-phase cubic fluorite PDC solid-solution. Two sintering models (Constant Heating Rate (CHR) method and Dorn method) were successfully implemented to identify the mechanism for early stages of sintering and found that grain boundary diffusion mechanism (m ~ 2) is dominating in PDC pellets synthesized by the MWCOP-ISP method. The effect of liquid additives such as Li, Co, Fe and Mg on the sintering kinetic behaviour of PDC pellets synthesized by MWCOP-ISP is further studied and decreased the sintering temperature from 1100°C to 850°C with the Li liquid additive as a sintering aid. The two sintering models further suggested that the Li-PDC pellets also follow the grain boundary diffusion model (m ~ 2) during the early stages of sintering. The 10PDC, 1Li-PDC, 3Li-PDC, 3Co-PDC, 3Fe-PDC and 3Mg-PDC nano-structured samples exhibited a thermal expansion co-efficient of 15.3x10-6 / °C, 18.2x10-6 / °C, 14x10-6 / °C, 15.2x10-6 / °C, 13.8x10-6 / °C and 15.7x10-6 / °C respectively.Item Synthesis and Characterization of Hollow Core-Shell Silica Nanoparticles as Drug Delivery Vector(National Institute of Technology Karnataka, Surathkal, 2021) Deepika, D.; Jagadeeshbabu, P. E.Nanodrug carriers are found to be better choice in the treatment of benign cancerous tumors which deliver small dosages of drugs specific to the diseased area. Scarcity in the emergence of new drug carriers with specific features like targeted delivery, higher drug loading capacity and biocompatibility has enhanced the research interest in them. Hollow core-shell silica nanoparticles (HCSNs) are being considered as one of the most favorable nanodrug carriers to accomplish targeted drug delivery, due to their unique properties like large surface area, tunable thickness, tunable pore diameter, low density, high chemical/thermal stability and good biocompatibility. In the present research work, we report a simple two-step method to synthesize HCSNs. HCSNs are synthesized using sacrificial template method. Polystyrene nanoparticles and funtionalized polystyrene nanoparticles (sulfonate and nitro functionalization) are used as sacrificial templates to obtain desirable morphology for the HCSNs. Polymer templates are synthesized in the first step and they are used as sacrificial templates in the second step during the synthesis of HCSNs by modified Stober method. Effect of the parameters like water-ethanol volume ratio, concentration of ammonia, concentration of cetyl trimethylammonium bromide (CTAB) and PS/tetraethyl orthosilicate (TEOS) weight ratio on morphology of HCSNs is analyzed. Further, polystyrene nanoparticles are functionalized to improve the surface charge properties by sulfonation and nitration. Functionalized PS nanoparticles are used as templates for the synthesis of HCSNs with enhanced shell thickness and pore size respectively. Effect of surface area, thickness of the silica shell and pore size on drug release from HCSNs are studied in detail using doxorubicin as a model drug. Application of HCSNs synthesized using sulfonated PS in sustained release of doxorubicin is found to be advantageous compared to the other synthesized samples. The properties of HCSNs samples synthesized using sulfonated PS such as higher shell thickness and pore size lead to higher encapsulation efficiency with sustained release of doxorubicin for 300 minutes. SPION embedded HCSNs are synthesized by sacrificial PS ii template method. Presence of SPION is an added advantage which aided radio frequency heating of the nanoparticles and allowed to study the variation of SPION concentration on the temperature rise. The release of drug from the SPION embedded HCSNs are found to be temperature dependant. The doxorubicin release kinetic profiles of HCSNs and SPION embedded HCSNs are studied using models such as zero order, first order and Higuchi model. Release kinetics showed best fit for first order model. In vitro cytotoxicity assays carried out on normal cells and cancer cells confirmed the biocompatibility of HCSNs and SPION embedded HCSNs. However, doxorubicin loaded samples achieved death of >85% of the cancer cells.Item Studies on Selective Extraction and Purification of Bioactive Compounds from Kokum (Garcinia Indica) Fruits using Alcohol Based Aqueous Two-Phase Systems(National Institute of Technology Karnataka, Surathkal, 2021) Nainegali, Basavaraj S.; Regupathi, I.; Prasanna, B. D.The bioactive compounds namely natural pigments and antioxidants are gaining high demand in the global market because of the increasing public awareness on the positive health benefits of these compounds due to their greater functional and bioactive properties and their potential applications in food, nutraceuticals, and cosmetic industries. The difficulty in the recovery from the complex natural sources and the instability due to the denaturation during the extraction and purification were inhibiting the application of these molecules in various industries. The substantial effort has been made to develop new technologies to extract and purify these bioactive compounds by retaining their native characteristics and stability. Kokum fruits (Garcinia indica) contain the important bioactive compounds like anthocyanin (ACNs), hydroxycitric acid (HCA), garcinol (GL), and isogarcinol (IGL) at a significant quantity. The simultaneous extraction of all these bioactive components in a crude extract is achieved using the aqueous mixtures of 1-propanol and ethanol as solvents. The aqueous two-phase extraction (ATPE) is explored for the first time to simultaneously partitioning the four bioactive compounds from the crude extract of kokum rinds. Alcohol-based aqueous two-phase systems (ATPSs) were proved to be suitable for the simultaneous partitioning during screening studies. The ethanol-ammonium sulphate and 1-propanol-ammonium sulphate/magnesium sulphate ATPSs are proved to be better for differential partitioning of GL and IGL into alcohol rich top phase and ACNs and HCA into the salt rich bottom phase. The effect of phase compositions and Tie Line Length (TLL) on the differential partitioning was investigated in terms of partitioning coefficient and extraction efficiency. The Response Surface Methodology (RSM) was adopted to optimize the process variables through desirability based multi-response optimization by considering the partitioning coefficients (K) and extraction efficiency (EE) of all the four bioactive compounds as responses. The ATPS consisting of 15.202 % (w/w) 1-propanol, 10.242 % (w/w) ammonium sulphate having the TLL of 28.505 % (w/w) at a crude load of 25 % (w/w) able to partition 97.39 % GL (K=370.770) and 92.38 % IGL (K=120.581) in the top phase and 99.19% ACNs (K=0.080) and 99.83% HCA (K=0.016) in the bottom phase with a purity higher than 99% by implementing the second stage ATPS. An attempt was further made to extract the bioactive compounds in the continuous extractor, Rotating Disc Contactor (RDC) with 1-propanol- ammonium sulphate ATPS. The efficacy of RDC column was analysed by studying the dispersed phase holdup, mass transfer coefficient, and recovery and separation efficiency of the bioactive compounds at different operating conditions.Item Microwave assisted Pyrolysis of Food waste to Biochar and Biofuels(National Institute of Technology Karnataka, Surathkal, 2020) Kadlimatti, Huchappa; B, Raj Mohan; M. B., SaiduttaMangalore is one of the fast growing cities of India and situated on the west coast of the Indian peninsula covering an area of 132.45 sq-km. The city is generating approximately around 312 tons of MSW per day of which 40% is the food waste (125 tons per day). At present this MSW is land filled leading to serious environmental and health problems. The given research thesis aims to (i) quantify and characterize the food waste generated in commercial and residential complexes of Mangalore city, (ii) pyrolysis of food waste with the assistance of microwave irradiation, optimization of the process parameters for better yields and (iii) characterization of the pyrolysis products using ASTM standard methods. Preliminary pyrolysis experiments were carried out to decide about the operating ranges for the pyrolysis temperature, residence time and nitrogen flow rate. Based on the thermogravimetric analysis (TGA) and preliminary pyrolysis experiments, the operating ranges for the time, nitrogen flow rate and temperature to carry out pyrolysis experiments were 25 to 35 min., 40 to 60 mL min-1 and 350 to 450 ºC respectively to design the experiments by response surface methodology (RSM). Pyrolysis yields of 30. 24 wt. % (bio-oil), 60.03 wt. % (biochar) and 9.73 wt. % (biogas) were obtained under the optimum pyrolysis conditions of 400 ºC temperature, 30 min. residence time and nitrogen flow rate of 50 mL min-1 respectively. The actual values of the operating parameters namely temperature, time and nitrogen flow rate and the responses for twenty experiments were used for the prediction of bio-oil, biochar and fixed carbon models. The regression models with 95% confidence level resulted in the high value of R2 = 95.4% with R2 adjusted = 91.2% indicated a very good or excellent fit of the data to the bio-oil model, high value of R2 = 92.9% with R2 adjusted = 86.4% indicated a very good or excellent fit of the data to the biochar model and high value of R2 = 90.3% with R2 adjusted = 81.60% indicated a very good or excellent fit of the data to the fixed carbon content model respectively. Bio-oil model was analyzed statistically by using experimental data and analysis of variance (ANNOVA). The linear terms suchvii as temperature, time and nitrogen flow rate were having the positive effect to increase the bio-oil yield when these variables are increased, whereas, square terms were having negative effect and decreased the bio-oil yield. The predicted value of the bio-oil yield was 0.02 wt. % less than the experimental value. Main functional groups as detected by the Fourier transform infrared (FTIR) analysis are alcohols, alkenes, aromatic compounds, primary and secondary amines, carboxylic acid, esters and phenols. GC-MS analysis was carried out to find the major compounds present in the bio-oil. GC-MS analysis identified 11 major compounds out of more than 500 compounds those were present in the bio-oil. Compounds such as oxygenated and non-oxygenated compounds, nitrogenated compounds and other compounds such as phosphine, methyl-, propane, 2- fluoro-, (2-hydroxyethyl) trimethylsilyl methyl sulfide, and 1,3-bis(2-hydroxymethyl) urea were identified by the GC-MS analysis. Though the heating value of the bio-oil was 23.94 MJ kg-1 it cannot be used as a bio-fuel, as it contains more water as well as nitrogenated compounds. However, bio-oil obtained can be upgraded and blended with diesel to use as a fuel through further investigation. Biochar and fixed carbon content model were analyzed statistically by using experimental data and ANNOVA. Linear and square terms were significant to effect biochar production followed by the fixed carbon content whereas the interaction terms were less significant parameters. The predicted value of the biochar was 0.05 wt. % less than experimental value, whereas, the fixed carbon content was 0.03 wt. % less than the experimental value. Biochar obtained under the minimum pyrolysis conditions of 400 ºC temperature, 30 min time and 50 mL min-1 of nitrogen flow rate at a power level of 450 W was used for characterization. Higher heating value (HHV) of the biochar was 33.35 MJ kg-1. HHV as calculated by the bomb calorimeter (33.35 MJkg-1) was higher than that of the Dulong formula (27.79 MJkg-1) value as the latter did not include the dissociation effects. HHV of the biochar was more than that of the FWS due to reduction of some higher heating value hydrocarbons.Item Metal Oxide Reinforced/Decorated Polymers as High Permittivity Dielectrics for Energy Storage Devices(National Institute of Technology Karnataka, Surathkal, 2020) Kishor Kumar, M. J.; Prasanna, B. D.; Jagannathan, T. K.High dielectric permittivity (high-k) materials are essential in fabricating energy storage devices, thin-film transistors, and piezoelectric devices. Solution-processable dielectrics are more desirable in energy storage film capacitors, and functional electronics, since they are cost-effective and can be produced in large quantities. The solution-process assisted by ultrasound is a well-known method as it provides the possibility of tuning properties of subsequent products by easily adjusting the precursor solutions. In this work, three categories of dielectrics, such as metal oxide-based dielectrics, namely, lanthanum cerium oxide (LCO), lanthanum zirconium oxide (LZO); polymer composite dielectrics, namely, polymethyl methacrylate (PMMA)- LZO and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)-LZO; anisotropic dielectrics such as polystyrene-iron oxide (PS-Fe3O4) patchy particles and lanthanum oxide-zirconium oxide (La2O3-ZrO2) dumbbell-shaped Janus particles, were fabricated at low temperatures using a sonochemical approach. In polymer composites, the main emphasis was on obtaining a uniform distribution of high-k LZO filler into a PMMA and PVDF-HFP matrix to improve their dielectric permittivity and energy storage density while lowering the dielectric loss. The effect of LZO content on dielectric properties and optimum LZO loading to achieve improved energy storage density of the films was studied. The enhanced energy storage density of 5.94 J/cm3 at 63.6 MV/m breakdown strength for PMMA-LZO and 15.8 J/cm3 at 545 MV/m for PVDF-HFP/LZO have been achieved. Further, the fundamental insights into the role of the polymer-metal oxide (PS-Fe3O4 patchy particles) and metal oxide-metal oxide (La2O3-ZrO2) interfaces on the dielectric properties have been addressed by considering experimental outcomes and computational simulations. Also, a new mechanism of charge build-up at these interfaces have been proposed. Computational outcomes reveal that the creation of interface bound-charges at the interface is predominantly responsible for the improved dielectric properties. Local morphology, dispersibility, interface area, crystallinity, and ionization of the metal oxides determine the overall dielectric permittivity of the film. Polymer-inorganic interface engineering and design open up a new area to develop hybrid materials for future energy storage systems.Item Studies on Bacterial Cellulose Production Using Industrial Wastewater(National Institute of Technology Karnataka, Surathkal, 2020) Gayathri, G.; Prasanna, B. D.; Srinikethan, G.Industrial wastewater management remains a critical environmental concern worldwide. Several new and modified methods have been implemented to manage the effluent discharge from the industries. These wastewaters predominantly contains huge amount of organic loads; which can be utilised as a nutrient source for cultivating microorganisms to obtain valuable products from the fermentation process. Bacterial Cellulose is one such useful biopolymer produced by certain class of bacterial strains. These have been extensively studied for their distinctive properties and applications. However, production of Bacterial Cellulose from wastewaters using a potential bacterial strain is still limited. Komagataeibacter saccharivorans BC1, a novel cellulose producing strain was isolated from rotten green grapes and studied for the production of Bacterial Cellulose. The strain was initially grown and optimised on standard medium for cellulose production. Later, the strain was evaluated for the production of BC in crude distillery effluent medium. 23.6% reduction in COD and 11.9% reduction in BOD value along with the production of 1.24g/L of BC were recorded. Scanning electron microscopy analysis revealed thin microfibrils with good porosity. Fourier Transform Infrared Spectroscopy studies indicated similar functional groups as that of cellulose derived from standard medium. XRD analysis revealed crystallinity index of 80.2% and crystallite size of 8.36 nm. Solid state 13C NMR analysis helped to study the structural framework of the synthesised cellulose. Further, the Bacterial Cellulose films were used to study in vitro drug release. The study demonstrated the absorption and release of the model drug for over 8 hours. The films were also assessed for their cytotoxicity activity using A549 cells and showed an IC50 value of 210µg/mL. Thus, production of a useful biopolymer from wastewater as a nutrient medium proves a sustainable approach to reuse the waste to produce a value-added product which could benefit both the environment and humanity.