PhD Theses (Chemical Engineering)

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    Experimental and simulation studies on plasma gasification of waste feedstocks for clean energy production
    (2024) Mallick, Roni
    In the cycle of waste generation and management, the recovery of energy from solid wastes through highly efficient and low pollutant technology is a promising way. Hence, the current study focuses on clean syngas production via plasma gasification of solid waste termed as refused derived fuel (RDF), computer keyboard plastic waste (CKPW) and electrical switch waste (ESW). On a laboratory scale, several experiments are conducted to assess the impact of feed mass flow rate, feed CO2 gas flow rate and plasma torch power on the syngas concentration and yield. A 3-E analyses comprising cold gas efficiency (CGE), exergy efficiency and levelized cost of syngas (LCOS) is performed, considering all the feeds. Further, two newly emerging technologies, (a) molten carbonate fuel cell (MCFC) and (b) chemical looping reforming (CLR), are integrated with plasma gasification for hydrogen and electricity production. The simulation of the plants is performed using Aspen plus and consequently, 4-E (3-E and environmental) analyses are executed. A high-quality syngas with H2 (32.23 vol.%), CO (51.98 vol.%) content, possessing a calorific value of 16.46 MJ/m3 and CGE of 39.04% is obtained for CKPW at the plasma power of 2 kW. However, with parameters of 30 g/10 min, 0.4 lpm and 0.75 kW, a higher CGE of 49.90% and exergy efficiency of 48.30% are achieved using RDF feed. While the lowest LCOS value of 23.40 INR/kWh is estimated for CKPW feed. The proximate and ultimate analysis of oil obtained from CKPW feed showed properties similar to diesel, with high C (90.8 wt.%), H (6.8 wt.%) and LHV (39.13 MJ/kg), and low O (0.46 wt.%) content. Whereas, the residue of RDF has high ash content of 13.95 wt.%. Ash contains a good amount of Ti, Ba, Ca, Si, Al, etc., which can find applications in healthcare, paints, dye-casting and the cement industry after enrichment.
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    Detailed Investigation of Pyrolysis Mechanism of Indian Oil Shale
    (2022) Baruah, Bhargav
    Pervasive requirement and utilization of reliable and readily available energy sources have led to the progressive depletion of conventional fossil fuel reserves. This has brought the unconventional fossil fuel reserves into focus. The unconventional petroleum resources are proven to hold a huge reserve around the world. One such resource is oil shale. Oil shale is a finely grained, porous, sedimentary rock which contains organic matter known as kerogen, concealed inside a mineral matrix. Kerogen is a complex organic compound which acts as the source of production of both conventional and unconventional petroleum and natural gases. On the application of heat, kerogen converts into bitumen which further breaks down into oil and gas. The most common and suitable method for production of oil and gas from oil shales as an alternative to conventional crude oil and natural gas is by retorting or pyrolysis. During oil shale pyrolysis process, the pyrolysis parameters significantly influence the yield and composition of the produced hydrocarbons. The mineral matters present in oil shale play a significant role in retorting or pyrolysis of oil shale. Inherent minerals such as silica, carbonate, pyrite etc. can drastically govern the heat transfer in oil shale, and influence the composition of products formed during pyrolysis of oil shale as an inherent catalyst.
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    Studies on flexible electrode-based batch and continuous microbial fuel cell
    (2023) Das, Bhanupriya
    Microbial Fuel Cells (MFCs) are promising sustainable energy technology which integrate power generation with waste remediation. However, its practical application is mainly hindered by firstly, its low power density owing to poor bacterial adhesion and electron transfer efficiency between bacteria and anode. Secondly, the use of Nafion as proton exchange membrane in microbial fuel cells (MFCs) is expensive with operational issues like biofouling and fuel crossover. Therefore, the current work addresses three issues of MFCs namely, to improve its performance, reduce the cost of operation and expand its horizon to real field application. The uniqueness of the work is the validation of the experimental study with comprehensive computational model complementing the experimental studies with new information about the system assembled with the indigenous membrane components The properties of the Nafion-alternative membranes, developed from environmentally benign polymers, poly (vinyl alcohol) (PVA) crosslinked with glutaraldehyde (GA) and Chitosan (CS)have been systematically studied and its performance evaluated against the commercial membrane in real wastewater fed MFCs. The membranes developed demonstrate potential as separator in future MFCs based on its enhanced performance and low cost of installation. Another important aspect hindering the practical application of MFCs which is low power density owing to poor bacterial adhesion and electron transfer efficiency between bacteria and anode. This issue is addressed by development of flexible electrodes using conducting polymer polyaniline (PANI) with sustainable polymer polylactic acid (PLA). An elaborate analysis of the performance of the bio-based flexible anode against commercial anode in domestic wastewater fed MFCs asserts its excellent biocompatibility, outperforming the flat graphite anode in achieving maximum power density and COD removal efficiency. The knowledge gap in the area of energy harvesting using complex substrates like hospital wastewater has been addressed using the indigenous PVA membrane developed. Experimental study conducted by replacing the commercial membrane in the recirculation mode honeycomb pattern MFC displayed enhancement in power production. An attempt to delve deeper into the atomic level to investigate the proton transport mechanism across the developed PVA membrane using Classical Molecular Dynamics study is demonstrated. The proton transport mechanism forms a crucial step which is a difficult to observe experimentally. The findings of the study demonstrated presence of multi-hydrated protons observed from MD trajectories suggesting that the proton transfer in the PVA polymeric membrane system occurred via vehicular mechanism. Furthermore, an essential parameter for the MFCs operating in recirculation mode, is its operating flow rate. To this end, numerical modeling, is utilized with parallel experimental study to get deeper insight into its effect on the performance in real wastewater fed MFCs for its viability for future commercial applications. Thus, the present study is focussed on adding a new dimension to the design of sustainable anode material to enhance microbial binding and achieve high power output, besides, developing an in-depth understanding of proton transfer mechanism and flow dynamics and its effect on the performance of MFC and lastly, to indigenously develop low-cost membranes to demonstrate the enormous potential of scale-up of MFCs for wastewater treatment in the future.
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    Optofluidic planar microreactors for the production of hydrogen and oxygen from photocatalytic water splitting
    (2024) Pala, Laxmi Prasad Rao
    The escalating demand for energy from renewable sources, driven by the depletion of fossil resources and environmental concerns, underscores the importance of green energy solutions. Solar energy, an abundant and renewable resource, presents a viable option, since only 0.015% reaching Earth is capable of meeting total global energy demand. While photovoltaic cells convert solar energy to electricity, challenges in storage and distribution necessitate alternative approaches, such as converting solar energy to chemical energy, specifically hydrogen fuel. This study explores solar light utilization for chemical energy generation as a promising avenue to meet contemporary energy needs sustainably. In this study, Titanium dioxide (TiO2) thin films are fabricated using a sol-gel spin coating method, incorporating modifiers and surfactants to control film structure and porosity. Photocatalytic overall water splitting (POWS) is explored as a sustainable solution for renewable hydrogen production. An optofluidic planar microreactor is constructed for photocatalytic water splitting with Pt/TiO2 photocatalyst thin films as photocatalyst. The Pt/TiO2 film with thickness 1650±119 nm showed a highest rate of 16.35 mmol h-1 g-1 (4.7 μmol h-1 cm-2) hydrogen production at an optimum reactant flowrate of 0.3 mL min-1 under visible light irradiation. The stability study carried out for 4 cycles of 5 h each proved that the photocatalyst was stable and the film was well adhered to the glass substrate. Another optofluidic planar microreactor, utilizing IrO2/TiO2 films, is developed for oxygen production through water splitting under visible light. An oxygen evolution rate of 3.99 mmol h-1 g-1 (1.84 μmol h-1 cm-2) was observed from the IrO2/TiO2 film of 3078 ± 362 nm thickness at an optimal flow rate of 0.3 mL min-1 in the presence of visible light. The stability study showed that the IrO2/TiO2 film was stable for at least 4 cycles, indicating the superior activity of the film firmly adhered to the glass substrate. The study culminates in the development of a single semiconductor-based photocatalyst, TiO2, with Pt and IrO2 as co-catalysts for overall water splitting. The 2.5IrO2/0.5Pt/TiO2 photocatalyst exhibits ideal POWS, producing hydrogen and oxygen from pure water under visible and simulated solar light (SSL). The rate of hydrogen and oxygen production were 9.73 and 5.32 μmol g-1 h-1, respectively, with a H2/O2 ratio of 1.82 under SSL with intensity 101.4 mW cm-2. The research provides insights into catalyst properties, scalability, and integrated systems for large-scale hydrogen production, contributing to the advancement of renewable energy and photocatalysis.
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    Removal and Recovery of Surfactants by Foam Fractionation
    (2022) Kumar, Awadh Kishor
    Surfactants are used in many industries, and they are integrally related to many consumer products. However, at the same time, they contaminate water. The environmental fate of the surfactants is considerably important due to their effects on the health of human beings and animals. They are of interest because of their increasingly ubiquitous domestic and industrial use, and the difficulty in removing them by the traditional treatment methods. The removal of of different types of surfactant by foam fractionation has been practiced for water/wastewater treatment. This process and its applications in water/wastewater treatment have been discussed in the Chapter 1 of this thesis. Chapter 2 of this thesis focuses on the materials and experimental methods
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    Experimental and Modeling Study on the Absorption of CO2 in Novel Activated Amine Solvent
    (2022) Ramesh, Tellagorla
    The increasing concentration of carbon dioxide (CO2) in the atmosphere has had a negative impact on the environment over the previous few decades and has been a focus of global attention. CO2 capture, one of the most important greenhouse gases (GHG), is now a critical stage in the functioning of electric power plants, petroleum refineries, chemical fertiliser plants, coal gasifiers, cement plants, and steel mills. Gas scrubbing with activated aqueous alkanolamine solutions has recently emerged as the most reliable post-combustion CO2 collection retrofit option.
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    Hydrodynamic Study of a Sidewall Nozzle Assisted Gas-Solid Fluidized Bed
    (2022) Rawat, Jitendra Singh
    The progress of new chemical technologies is moving faster in the design of the unconventional reactor system to upgrade the oid technologies and to solve new tasks. There are several tasks that need to be addressed for enhancement of the selectivity of the product in a distributed feeding of reactants along with the reactor height. One of such reaction is, thermal denitration of ammonium di-uranate (ADU), which thermally decompose the ammonium nitrate into nitrogen and water vapor. The reaction is carried out in a filuidized bed maintained at 350 °C. In this reactor, the side streams of ADU (reactants) are injected at higher velocity through multiple pneumatic nozzles. At the surtace of the hot solid ammonium nitrate decomposes into nitrogen and water vapor. It is observed that fraction of ammonium nitrate bypasses the reactor without any decomposition. This affect the performance of the reactor and overall process. The extent of bypassing depends on nozzle diameter, flowrate, nozzle configuration, solid flow feld and solid distribution. Therefore, it is vital to study the effect of above mentioned parameters on the behavior of sidewall nozzle injected fluidized bed reactor.
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    Corrosion inhibition of steel in acidic media using bio-waste extract: Experimental and theoretical consideration
    (2023) Pal, Abhradip
    This thesis discusses chemical processes, types, economic effects, and remedies of corrosion as background studies. The thesis focuses on finding green corrosion inhibitors from various bio-wastes, such as solid waste from tea factories (food-industrial waste), purple rice bran (agro-byproduct), banana flower bract, and onion peel (kitchen waste). The corrosion inhibition efficiency was determined in acidic media (HCl and H2SO4) on boiler-quality steel. The main objectives were (a) Extraction and characterization of green corrosion inhibitors, (b) Electrochemical kinetic study of inhibitors using potentiodynamic polarization on boiler quality study in acidic media to find out their corrosion rate and corrosion current, (c) Study on inhibition mechanism using electrochemical impedance spectroscopy, (d) Adsorption kinetics to find the type of adsorption, (e) Theoretical studies of inhibitory molecules identified in the extract. The entire work of this thesis has been divided into four significant chapters as follows:
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    Extraction of bioactive compounds from Ficus auriculata leaves and its application
    (2023) Baite, Thangsei Nengneilhing
    Gallic acid is a well-known antioxidant ascribed to various beneficial health effects and is found in a variety of plants. In this work, firstly, gallic acid was extracted from Ficus auriculata leaves using ultrasound-assisted extraction, and the process parameters were optimized. Maximum extraction was obtained after 30 min at 50% sonication level, 1:10 g/mL solid to solvent ratio and pH 8 at 50 °C. 50% methanol resulted in highest extraction followed by alkaline water and 50% ethanol where gallic acid content in the extract was found to be 329.46 mg/L, 312.92 mg/L and 183.74 mg/L, respectively. Secondly, the gallic acid (antioxidant) rich leaf extract of F. auriculata was then incorporated into polyvinyl alcohol (PVA) and utilized as a coating to delay the ripening of green bananas. The weight loss was higher in the uncoated group than in any coated fruits. The reduction in titratable acidity and the increase in total soluble sugars was slower in all the coated samples, as compared to the uncoated ones. The fruits without any treatment attained complete maturity on the 9th day. The fruits coated with pure PVA as well as 10% extract incorporated PVA remained acceptable till day 15, while the ones with 1% and 5% of extract reached full ripeness on the18th day. Thirdly, the extracted gallic acid was used as the active ingredient for the preparation of antioxidant formulations. The free-flowing formulations were formed into tablets using a hand-operated pellet maker. All the tablets had disintegration times below 15 min, which meet the standards of the Indian Pharmacopeia. The formulations were found to be stable at pH 2.5 and 8.5, signifying a good stability in the gastrointestinal tract. Finally, lignin was extracted from the waste leaves of F. auriculata obtained after separation of gallic acid and incorporated into PVA films. Lignin addition improved the UV-shielding, thermal, antioxidant and mechanical property of PVA films. The prepared films showed a much better performance than commercial packaging films in inhibiting mold growth during storage of preservative – free bread storage. The bread samples packed with commercial package showed signs of mold growth on the 3rd day while the growth was completely inhibited till 15th day for PVA film containing 1% lignin. The pure PVA film and the ones containing 3% and 5% of lignin inhibited growth till the 12th and 9th day, respectively. Findings from the current study shows that safe, cheap and eco – friendly biomaterials can inhibit the growth of spoilage microorganisms and thus potentially be used in food packaging.
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    Real-Time Monitoring and Optimization of the Oil and Gas Well Drilling Process
    (2022) Senthil, S
    Fossil fuel has been serving the world's energy needs for a century. The depletion of fossil fuels from conventional resources has forced the drilling industry to explore complex oil fields. Multiple downhole complications could arise during the drilling operation. Few of them are contagious to the life of the drilling floor workers, such as kick events, oil spills and blowouts. In addition to the above risks, techno-economical sustainability also hampers the process of exploring unconventional reservoirs. A typical drilling plan is made based on the geotechnical survey report and historical data of the exploratory well of the same oil field. However, the uncertainties and deviations from the anticipated downhole conditions are often encountered during drilling, leading to complications in drilling. In such situations, the new process parameters suggested by the experts may not be the optimum for the newly encountered downhole condition. The sub-optimal drilling process may often result in more energy consumption and time for the completion of the well. Therefore, optimization of drilling parameters and monitoring of downhole conditions should work parallelly to achieve energy-efficient drilling of oil and gas wells. This approach is demonstrated by developing a decision support system (DSS) for oil and gas well drilling. The developed DSS can 1) detect critical drilling problems in real-time and take preventive measures, 2) suggest the best search range of process parameters for optimal drilling operation from the historical data, and 3) do real-time optimization for the dynamic wellbore conditions, 4)The developed model can predict the spatial variation of cutting concentration, which was required for real-time root cause analysis. Two case studies were conducted to validate the model, and the model was able to predict drill string washout, cutting accumulation, and mud pump failures before they occurred.
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    Studies on the Synthesis of Bacterial Cellulose and its Utilization in Value-Added Chemical Transformation and Biomedical Applications
    (2023) Das, Munmi
    The fabrication of BC and BCNCs is a promising technology as it opens dimensions with multiple application possibilities with the “waste to wealth” strategy. The impregnation of biodegradable polymers, such as PCL into the BC network resulted in the presence of polymer layers on the surface as well as inside the pores of the BC matrix indicating a good fiber-matrix interaction. These fabricated BC and BCP composite membranes were biocompatible and nontoxic to BHK-21 cells even after 72 h, allowing cell proliferation. Electrospun nanofibrous dressings based on lidocaine hydrochloride loaded bacterial cellulose/ polycaprolactone (BCP) revealed their cytocompatible nature. The utilization of BCNCs can aid in the reduction of carbon dioxide that is responsible for global warming and climate change. The strategic functionalization of BCNCs through the sustainable approach avoids the utilization of harmful chemicals. BCNC templated catalysts, are one of the versatile nanomaterials developed in this work, with potential application as biocatalysts in value-added chemical transformation. On the other hand, 5-Hydroxymethyl-2-furfural (HMF) is considered an important platform chemical among other intermediates derived from biomass. In this study, we have used mesoporous BCNC templated zirconium phosphate as a catalyst for the conversion of furfural into HMF. The catalyst was synthesized using a wet-precipitation method and was characterized using powder XRD, FT-IR spectroscopy, FETEM, BET and FESEM. The as-prepared BCNC templated catalyst showed mesoporous structure with high surface area and exhibited excellent catalytic activity as compared to pristine ZrP for the formation of HMF, from furfural. Also, the HrP-immobilized BCNC hydrogel exhibited good self-healing properties and was reused efficiently for 6 cycles with greater than 50% of its original activity retained even after 60 days, which facilitated their application as promising biomaterials. Therefore, this doctoral thesis focuses on the utilization of BC and its functionalization for development of polymeric scaffolds, biocatalysts, as well as their advanced applications as biosensors, in biotechnological applications.
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    Experimental and Molecular Modeling Insights on the Thermolytic Dehydrogenation of Amine Boranes with Ionic Liquids and Deep Eutectic Solvents
    (2022) Mishra, Dhirendra Kumar
    The scientific community has identified hydrogen energy as a potential fuel for the foreseeable future. The hunt for hydrogen storage materials capable of storing hydrogen efficiently while remaining compact and lightweight is one of the most difficult tasks facing the emerging hydrogen economy. Using solid chemical hydrides with high gravimetric and volumetric hydrogen densities, it may be possible to overcome the difficulties associated with hydrogen storage. The solid-phase nature of these hydrogen storage devices provides key advantages such as ease of discharge, a greater kinetic, and controlled release of hydrogen equivalents at moderate temperatures.
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    Studies on Utilisation of Agro-Waste for Fabrication of Sustainable Bio-Composites
    (2023) Bhattacharjee, Sayan Kumar
    This doctoral thesis focuses on the valorisation of agricultural waste in the form of rice straw and the fabrication of different polymeric bio-composites and nanocomposites. Other value-added products in the nanometres range were chemically synthesized from RS, i.e., nano-silica (NS), cellulose nanocrystal where these nanofillers are incorporated in various thermoplastic biopolymer matrix, i.e., Poly (lactic acid), Poly (butylene succinate). However, in the melt extrusion process at higher temperatures, miscibility and the phase separation between the polymer matrix and these nanofillers is still challenging for the scientific community as these tend to aggregate due to small size effects, high surface energy, and relatively poor interaction between the filler and the polymer matrix which in turn decreases the mechanical property of the composites. Various compatibilisers and cross-linking agents were incorporated into the systems to improve the miscibility during melt processing. This thesis also investigates the influence of different nanofiller content on the thermal, mechanical, and rheological properties of the bio-composites and nanocomposites. The structure-properties relationship of the composites was explored in terms of the mechanical properties, thermal properties, crystallisation behaviour, and rheological properties, which have been summarized in six different chapters and explained in detail in subsequent sections.
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    Synthesis of Bio-lubricant Base Stocks From Waste Oil
    (2022) Paul, Atanu Kumar
    Lubricants are oils that are often used in machines to reduce friction. Most lubricants and functional fluids in the present day are made entirely from petrochemical or mineral sources. Rising concerns about the environmental effects of mineral-based lubricants have prompted research into biodegradable lubricants. Vegetable oils have excellent biodegradability and rheological properties at higher operating temperatures, but poor cold flow characteristics Several methods have been attempted to solve these technological challenges, including altering fatty acid structure and genetic modification. Bio-lubricant base stocks derived from waste soybean cooking oil and its methyl esters are ideal for hydraulic and transmission applications as an alternative to traditional lubricants. Three modelling methods, namely, Response Surface Methodology (RSM), Artificial Neural Network (ANN), and Genetic Algorithm (GA) have been applied to optimise the process parameters to maximise the product yield. Additionally, thermal degradation kinetics of the prepared product have also been attempted in this study.
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    Rheology and Microstructure of Shear Thickening Suspensions
    (2022) Prabhu, T Ajeeth
    The thesis focuses on the experiments studies on rheology and microstructure of discontinuous shear thickening suspensions. In the current study, we present a systematic rheological study on the fumed silica suspensions to understand the effect of fluid and particle parameters on the critical shear rate and shear thickening ratio. A careful sample preparation method was adopted to disperse the fumed silica particles in polyethylene glycol solution, and we achieved discontinuous shear thickening at low particle concentration. It was observed that the critical shear rate in shear thickening suspension is strongly influenced by both carrier fluid and particle concentration. However, the shear thickening ratio is mainly influenced by the particle parameters and the contact forces between the particles. Increasing the amount of smaller particles in the suspension significantly decreases the maximum viscosity and shifts the onset of shear thickening to higher values of critical shear rates with a much smaller shear thickening ratio. Further, a possible mechanism has been proposed based on the influence of carrier fluid and particle size distribution to explain the rheological behavior of shear thickening suspension. Experiments to determine the role of additives on the behavior of shear thickening fluids (STF) were also carried out. This involved preparing shear thickening suspensions with the addition of fillers to the fumed silica particles for a given weight fraction and a carrier fluid. Addition of Graphene oxide particles exhibited higher relative viscosities, whereas the addition of Multi-walled carbon nanotubes (MWCNT) and Mica particles showed a decrease in the shear thickening ratio and an increase in critical shear rate. Finally, we report experimental studies on rheology and microstructure in discontinuous shear thickening of fumed silica suspensions using Rheo-Microscopy experimental setup. The formation of particle clusters was observed after the critical shear rate, and their size increase during the shear thickening. At higher shear rates, these clusters were found to break down due to strong shear forces, and a continuous decrease in viscosity was observed. The suspension viscosity and the first normal stress difference (N1) variation with the shear rate showed similar dependence. The sign of the first normal stress difference was negative during shear thickening, which is consistent with the hydrodynamic model of cluster formation. The oscillatory shear measurements were also performed, and the samples displayed strain thickening similar to shear thickening. Finally, the similarity between the steady and dynamic shear rheology at high strain amplitudes was observed using the modified Cox-Merz rule.
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    Optofluidic Microreactor for the Photocatalytic Hydrogen Generation via Water Splitting Reaction
    (2023) Rambabu, Ponnala
    The hydrogen (H2) is the most viable future energy carrier due to its high gravimetric energy density and non-polluting nature. The direct conversion of solar to green H2 via photocatalytic water splitting has a great potential and the optofluidic microreactors (OFMRs) are highly useful in this regard. The OFMRs in photocatalysis enables the concurrent and fine control of fluid flow, photon harvesting, and reaction with the shorter transfer path lengths, which in turn improve the photocatalytic reaction performance. However, due to complex and expensive fabrication, these devices are not well established in practical applications. In this study, we describe a simple, rapid, and inexpensive method to fabricate microchannels with various geometries on the glass substrate and tested them for the production of green H2 via photocatalytic water splitting after coating with a sustainable photocatalyst. The adhesive tape as mask resulted in deeper channels (up to 550 μm), and higher etch factor (1.2) as compared to those obtained with UV photolithography. The semi-circular shaped microchannel with sharp edges and without any wall irregularities was obtained with adhesive tape as mask and using 49% HF solution as chemical etchant at room temperature for 120 min.
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    Synthesis and Performance Evaluation of a Novel Natural Surfactant–Polymer Assembly for Enhanced Oil Recovery
    (2022) Machale, Jinesh Subhash
    A significant amount of oil (i.e., 60–70%) remains trapped in the reservoirs after the conventional primary and secondary methods of oil recovery. Enhanced oil recovery (EOR) is, therefore, necessary to recover the major fraction of unrecovered trapped oil from the reservoir to meet the present-day energy demands. The chemical method of EOR involves the injection of alkali, surfactant, polymer, and a combination of alkali–surfactant–polymer solution in the reservoir with the objective of achieving a reduction in interfacial tension and matching the mobility between oil and water for more recovery of oil. The success of this method depends on the effective synergy between the chemical additives.
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    Noise-activated dynamics of DNA through nanoporous gel
    (2023) Deb, Aniruddha
    Gel electrophoresis is a widely used protocol in molecular biology and biochemistry for separating and analyzing biomolecules based on their size, charge or other physical properties. However, conventional gel electrophoresis techniques suffer from limitations such as time-consuming process and the need for specialized equipments. In Chapter 2 of this dissertation, we have demonstrated noise activated gel electrophoresis, a phenomenon in which the addition of noise in the form of voltage pulses combined with bias voltage can improve the separation efficiency and sensitivity of gel electrophoresis. We also have discussed the theoretical foundations of modified Langevin equation supporting our experimental results. Noise activated gel electrophoresis offers the potential for reducing the reliance on high voltages and extended separation times, making it a promising alternative for rapid and efficient biomolecule analysis. Furthermore, the integration of noise assisted gel electrophoresis with other analytical techniques holds the potential for developing novel approaches in genomics, proteomics and clinical diagnostics. With ongoing research and advancements noise activated gel electrophoresis is poised to revolutionize the field of bio-molecular separations and analysis enabling faster characterization of biological samples. In Chapter 3 of this dissertation, experimental analysis explained that noise applied in a direction orthogonal to the bias direction, it is feasible that the macromolecule will choose the path that uses least amount of energy in the energy landscape. Instead of immediately crossing the barrier's apex, the molecule might seek for the neighbourhood’s lowest barrier height and use the least energy-consuming route to avoid the energy loss incurred by the apex-crossing. In Chapter 4, we explored how, in an electrophoretic environment, the adhesive engagement of a soft deformable macromolecule within the gel matrix leads to a sub-critical rupture generating faster translocation due to the existence of asymmetric vibration in the form of ramp pulses. Chapter 5 illustrated how, utilizing an external noise assisted gel electrophoretic platform, Aptamer-AuNP band mobility can be increased, allowing biologists to detect particular pathogens quickly for correct antibiotic prescription and additional counseling. This study also aimed to develop an aptasensor based on the surface plasmon resonance (SPR) of gold nanoparticles that generates a straightforward colorimetric output.
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    Synthesis and characterization of poly(lactic acid) based antimicrobial bio-nanocomposites for potential food packaging applications
    (2023) Boro, Udangshree
    "Biopolymers or biodegradable polymers have gained enormous attention worldwide as an alternative to synthetic plastic mainly due to their biodegradability, non-toxic, and renewable resources. Among different biopolymers, poly(lactic acid) (PLA) is the most widely used material in food packaging applications. However, like other biopolymers, PLA has limitations, such as poor thermal, mechanical, and barrier properties compared to synthetic non-degradable plastics. But, storage and transporting any product, especially food, requires a strong, tough material that can withstand any harsh conditions encountered during transportation and storage. Moreover, packaging should preserve food quality, prolonging the product's shelf life. Given the above, the present doctoral work aims to synthesise poly(lactic acid) based bio-nanocomposites by incorporating different nanoparticles/antimicrobial additives with enhanced physiochemical properties for potential food packaging applications. The ltrasound-assisted solvent casting method is used to synthesize PLA-based antimicrobial bio-nanocomposites with four different nanoparticles/ additives viz. ZnO nanoflowers, functionalized ZnO, ZnO@HNT and CEO/alkali-treated HNT. The ZnO nanoflowers were synthesized via a facile sonochemical method with Zn(NO3)2·6H2O as a precursor in different molar concentrations (0.025, 0.05, 0.075 and 0.1 M). The physiochemical characterization of the nanocomposites revealed excellent thermal, optical and mechanical properties at a very low loading of ZnO (0.5 wt%). The second chapter reported the synthesis and surface modification of ZnO nanoparticles with 3-aminopropyltrimethoxysilane coupling agent (APTMS). Thereafter, the nanocomposites of PLA with surface-modified ZnO were synthesized by ultrasoundassisted solvent casting method. The third chapter reported the synthesis of nanocomposites of PLA with ZnO@HNT by using an ultrasound-assisted solvent casting method. The nanocomposite film PZH2 (consisting 2 wt% ZnO@HNT) showed the best properties compared to PLA. Moreover, a packaging test was performed on cut apples for 6 days storage period to evaluate the potential efficacy of nanocomposite films for food packaging
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    Sustainable and Green Composite Functional Hydrogels: Synthesis, Characterization and Performance Evaluation
    (2023) Ingtipi, Kajal
    "Hydrogels are the most versatile multifaceted polymer material which is widely applied in biomedical devices, bioelectronics, drug delivery, water remediation, and recently as fire retardants. The demand for low carbon footprint encourages the world to develop environmentally friendly and sustainable hydrogels. To achieve sustainability, the idea of valorizing waste biomass to formulate biomass-based hydrogel has become the primary focus of many researches. In this thesis, we have tried to valorize extracted components of Arundo donax namely, cellulose and lignin to formulate biomass-based hydrogels. The lignin extracted was irregular shaped and difficult to disperse in water. This particular problem was resolved by reducing the size of the lignin particles. Two different methods were opted to synthesize nano sized lignin particles. In the first method, lignin was ultrasonicated to produce nano sized lignin (10 to 50 nm). In the second method acetone‒water cosolvent method (coprecipitation) was opted to produce core and shell structured spherical lignin particles (50‒200 nm). These lignin particles were doped in PVA‒Chitosan (CS) and PVA‒xanthan gum (XG) blends respectively to formulate biopolymer based hydrogels. These lignin particles act as reinforcements and substantially improved the elastic moduli (G′) of the formulated hydrogels. Ultrasonicated lignin was further utilized to disperse multiwalled carbon nanotubes (MWCNT) in water and incorporated in PVA‒CS blend to developed physically crosslinked conducting hydrogel. The conductivity of the formulated hydrogel was determined by electrochemical impedance spectroscopy (EIS) measurement. The conductivity of the formulated hydrogel was estimated at around 8.22 mS cm-1 for 1% MWCNT incorporation. The spherical lignin obtained as a result of the coprecipitation method was doped in basified PVA‒XG and crosslinked by Na2B4O7. This hydrogels was regenerated on cotton fabric to obtain PVA‒XG‒LNP hydrogel coating which substantially reduced the flammability of cotton cloth. Cellulose, another component extracted from biomass is extremely susceptible to fire. To improve its fire retardancy cellulose hydrogel was formulated by dissolving cellulose in NaOH/Urea mixture and crosslinking it with methylene bisacrylamide (MBA). To further improve the fire retardancy kaolin was added to the hydrogel matrix. The cellulose hydrogels were regenerated on cotton fabric to impart fire retardancy to cotton fabric. The efficacy of fire retardancy was validated by performing a cone calorimetry test (CCT), vertical flammability test (VFT), open fire test (OFT), and measuring the limiting oxygen index (LOI). Further, the swelling and water retention ability of the fire retardant hydrogels were measured to check the water encapsulating and retaining potency. The network parameter of the hydrogels (mesh size, crosslinking density, and molecular weight between crosslinks) was also estimated using the results from the swelling test and elastic moduli (estimated by rheological studies). The results state that incorporation of 20% v/v LNPs in 2% w/v NaOH PVA‒XG solution and 0.4% w/v Na2B4O7 crosslinker induced substantial crosslinking and hence increment in moduli and reduction in swelling ability and water retention ability was observed. Similarly, the incorporation of 2% w/v kaolin and a high amount of MBA followed similar findings. Performing thermal analysis of the hydrogels confirmed that the hydrogel formulated were highly thermally stable and high char producing (34.61 wt.% for PVA‒XG‒20% v/v LNPs hydrogel and 63 wt% for 2% w/v kaolin incorporated cellulose hydrogel). All these results postulate the successful synthesis of biomass extracted component based hydrogel and its application as conducting hydrogel and hydrogel fire retardants"