PhD Theses (Chemical Engineering)

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Bioinspired Synthesis of Metal Oxides and Sulphide Electrocatalysts for CO2 and N2 Conversion to Formate and Ammonia
(2023) Chowdhury, Anirban
This doctoral work focuses on the development of environmentally friendly processes for the synthesis of metal oxides and metal sulphide (nano)electrocatalysts. These catalysts are then utilized for the electrochemical reduction of CO2 and N2 to produce value-added chemicals in a semi-batch laboratory electrolyzer.
Protein-Surface and Protein-Ligand Interactions: Insights from Atomistic Simulations
(2024) Tiwari, Shivam
Proteins are one of the most abundant and essential class of organic molecules present in the living systems. Their role in the sustenance and growth of life is unique. However, proteins can turn toxic and unfavourable if they are displaced from their native form or present in an undesirable environment. In this thesis, we perform a computational investigation of protein's interaction with various surfaces and chemical entities in varying environments. Various roles of protein are explored in this thesis, ranging from, as a foulant in a desalination membrane, as a cell invader to toxic β plaques causing cell damage. Specifically, in the first part (first two chapters) of the thesis, the protein plays a role of a membrane foulant. We investigated the reason for differences found in fouling of reverse osmosis (RO and a forward osmosis (FO) membrane with lysozyme protein. We explained the role of hydration repulsion and electrostatic interactions in the differences found in FO and RO fouling. we studied the interaction of SARSCoV2' s spike protein (which plays a crucial role in cell entry of the CoV2 virus) with the montmorillonite surface, a clay mineral. Substantial damage to the secondary structure of spike protein is observed in the presence of a mineral surface. In the last two chapters, protein is in the form of toxic β sheets, responsible for a range of age-related dementia. Mechanism of binding and disaggregation of Aβ fibrils with a novel peptidomimetic compound was investigated. The compound showed a strong binding on Aβ fibril via hydrophobic interactions and significant destruction of the fibril's β sheet content. Finally, the interaction between A β fibrils and lipid bilayer was studied using a prodrug peptide β-Aspartyl. The study showed that β-Aspartyl inhibits the interaction between A β fibrils and lipid bilayer. The study also showed the role of π- π stacking and cation-π interactions in binding β-Aspartyl on fibrils.
Treatment of Steel Industry Wastewater by an Integrated Ozonation and Electrocoagulation Process
(2024) Das, Pranjal Pratim
The steel industry plays a crucial role in global economic growth, yet its expansion has led to increased wastewater discharge, which varies based on the unit operations used, such as blast furnaces, coke ovens, and rolling mills among others. Such wastewater often contains toxic pollutants like cyanide, phenol, oil & grease, ammonia-N, and colored compounds. Conventional treatment methods, including chemical coagulation and biological processes, sometimes fail to fully remove these contaminants, thus prompting the need for more effective solutions.
Valorization of Rice-Husk for Optimal Production of Bio-Oil, Bio-Char, And Silica Nanoparticles
(2022) Das, Sutapa
Rice husk is an agricultural waste-product whose management has yet not been standardized on a commercial-scale following sustainable norms. Ineffective waste management of this abundant biomass often leads to large amounts of rice husk being decomposed via means such as open-pit incineration. This severely impacts the environment and is one of the leading causes of air pollution, notable mostly in the region of North India. Over the decades, different processes have been adapted to tackle this issue. One of the thermochemical techniques, pyrolysis, offers immense potential towards converting this biomass to several value-added products. This thesis employs the usage of slow pyrolysis to achieve the conversion of rice husk to bio-oil, bio-char and silica nanoparticles. In order to optimize the overall process towards maximizing the product yield, an optimization scheme, namely, Response Surface Methodology (RSM) has been employed which helps determine the ranges for the different process variables - temperature, gas holding time and gas flow rate. Extensive characterization of the process and the products have been carried out. Slow pyrolysis has been performed under inert (N2) and reactive environments (CO2) to understand the effect of ambient conditions of the product profile. For instance, bio-char, displayed adsorbent features such as high porosity, surface area, and hydrophilicity when generated under CO2 environment, while under N2 environment, it possessed a high carbon content, thus highlighting its usage as a soil conditioner for improving soil fertility. Bio-oil, on the other hand, was also obtained and its physico-chemical characterization revealed potential for usage as a fuel. It was subjected to different upgradation techniques such as solvent-exchange and catalytic-upgradation in presence of bio-char. Thus, the latter technique also presented itself as another route towards utilization of organic modifiers for improving bio-oil properties. Silica nanoparticles (SI NP), were also generated using the rice husk as a feedstock. These particles were obtained as a result of calcination process involving bio-char. SI NP could themselves be modified and applied as a membrane, using natural cotton substrate, for effectively separating oil from an oil-water mixture. Thus, in a nutshell, this thesis aims to highlight the effectiveness of the slow pyrolysis process by utilizing the abundant biomass for obtaining the diverse collection of valuable products.
Crystallization, Separation, Extraction, and Quantification on a Microfluidic Platform
(2022) Singh, Sunil Kumar
The primary focus of the thesis is to explore, design and develop a microfluidic platform for the efficient resolution of enantiomers, surfactant separation, dye extraction, and Hemoglobin quantification. A flexible μ-reactor and a μ-crystallizer are fabricated for the continuous production of diastereomer salt crystals from racemic α-phenylethylamine (I) where optically active L-(+)-tartaric acid (II) is used as a resolving agent. Moreover, a Y-shape microchannel was fabricated and thin copper sheet electrodes were placed across the channel to separate both anionic and cationic surfactant simultaneously from its mixture under the influence of ultra-low electric voltage. It was found that separation efficiency solely depends on the residence time of the fluid. Furthermore, liquid-liquid extraction was investigated to transfer a component transfer from one liquid phase to another liquid phase under the presence of an applied external electric field in a microchannel. With this, we explored interfacial instability in the presence of an external electric field inside the microchannel for the extraction of methylene blue dye from the aqueous phase using N-amyl alcohol. Additionally, we attempt to develop a simple, low-cost, easy to use point of care (PoC) device based on the spectrophotometric principle for the quantification of Hemoglobin (Hb) on a microfluidic platform. The specific interactions of Methylene Blue (MB) with Hb in the presence of CDs show a unique characteristic optical feature, and the same is exploited for the quantitative estimation of Hb.
Studies on Energy and Environmental Applications of Ravenna Grass (Saccharum ravennae) Biomass
(2024) Dhara, Simons
The Ph.D. thesis focuses on the utilization of Saccharum ravennae grass as a biofuel source and for environmental applications. Bioethanol production involved optimizing sugar yields using enzymatic hydrolysis with various pretreatment methods, including CCD RSM for alkaline lignin extraction , which were targeted as the first two objectives of the thesis . Thereafter, the last two objectives of the thesis affirmed the utilization of the extracted lignin with the PSf membranes for Cr(VI), Pb 2+2+, and dye removal from
Studies on Development of Bio-based Biodegradable Polymers and Their Efficacy as Biomaterials
(2023) Chethana, M
Exhaustion of non-renewable resources and increasing concern towards the non-biodegradability of conventional polymers demands research for alternative, bio-based and biodegradable polymers having comparable properties. Recently, research in the field of sustainable polymers is highly focused on the use of renewable wastes generated from agriculture, food, and the meat industry for the development of biodegradable biomaterials. The biomaterials prepared from these renewable wastes find their applications in the field of medicine and help to restore biological functions. Polyhydroxybutyrate (PHB) is a biodegradable biomaterial of bacterial origin produced intracellularly as an energy reserve in a stress-induced condition which has a potential application in drug delivery. Poly(latic acid) (PLA) is another class of bio-based polymer produced by the polymerization of lactide predominantly used in biomedical applications and packaging. Prodigiosin is a bacterial pigment used as a remedy for cancer treatment, and nanocellulose is a bionanomaterial suitable for high-performance applications. In this perspective, the current study extensively deals with the utilization of waste sorghum stalks consisting of fermentable sugars, cellulose, and hemicellulose for the production of biomaterials such as PHB and nanocellulose. Prodigiosin is produced from Serratia nematodiphila isolated from river water, and metal-free PLA is synthesized using prodigiosin as a metal-free catalyst. Over the assessment, the juice from agricultural waste sorghum stalks consisting of ~60 g/L of fermentable sugar is used as an inexpensive carbon source for the production of PHB. The minimal media supplemented with sorghum juice is used for the optimization and production of PHB. The optimized conditions yielded the maximum productivity of ~8.2 g/L of PHB within 24 h of cultivation. The fed-batch operation with dO2 controlled strategy maximized the productivity four-folds in comparison to the batch operation. It was able to obtain PHB with a molecular weight of ~400 KDa and recovery of ~94% using solvent extraction. The characterization of the produced
Extraction of Dietary Bioactive Components from Sea Buckthorn Leaves and Whole Berries using Organic Solvent and Supercritical CO2, and Its Application in the Synthesis of Silver Nano Particles
(2023) Tadesse, Abebe Moges
The berries and leaves of Hippophae salicifolia have nutritional and bioactive characteristics, with the leaves being more nutritious and physiologically active than the berries. Vitamin C was the most abundant phytonutrient in the berries, whereas the leaves had the highest total soluble sugar concentration. The berries and mixture of leaves were successively extracted using n-hexane, chloroform, ethyl acetate, acetone, methanol, and water. Total phenolic content (TPC) was highest in the leaves-methanol extract (157.97 ± 2.09 mg GAE/g) and berries-aqueous extract (48.45 ± 1.94 mg GAE/g). Berries-aqueous and leaves-methanol extracts showed excellent global antioxidant scores. Further, extraction of polyphenolic compounds from H. salicifolia leaves using supercritical carbon dioxide (SC-CO2) was optimized to achieve maximum yield of extraction, TPC and antioxidant activity. Under optimized condition. the experimental data showed good agreement with the predicted values. SC-CO2 extraction was more selective for the extraction of ferulic acid, myricetin, and quercetin. SC-CO2 extracts demonstrated notable antibacterial activity. In addition, process variables (pressure, temperature, and CO2 flow rate) for oil extraction from H. salicifolia berries using SC-CO2 were optimized with the objective to achieve maximum oil yield, β-carotene, and total tocopherol contents. CO2 flow rate had a maximum effect on oil yield, while pressure showed a significant influence on β-carotene and total tocopherol contents of oil. The optimum extraction condition was 27.02 MPa pressure, 48.46 °C temperature, 16.45 g/min CO2 flow rate. The oils extracted using solvent and SC-CO2 extraction contained 92.72 and 91.42% UFA. SC-CO2 extracted oil had higher TPC and antioxidant activity than solvent extracted oil. SC-CO2 extracted oil exhibited lower thermal stability and higher resistance to mechanical stress. Finally, silver nanoparticles (Ag NPs) were synthesized using methanol and aqueous extracts of H. salicifolia leaves and berries. Phenolics, proteins, benzenes, and sulforaphane are responsible for converting Ag+ to Ag0. Ag NPs were spherical with an average particle size of 7.87 ± 2.9 nm to 13.86 ± 5 nm. Ag NPs synthesized using aqueous extracts were smaller than those synthesized using methanol. Whereas Ag NPs produced from methanolic extract of leaves exhibited the highest antioxidant and antibacterial activity.
Characterization of Mineral-Based Colloidal Microbubble and Its Subsequent Application in Separation of Fine Mineral Particles
(2022) Ruby, Kumari
Ionic Microbubbles are miniature gas bubbles of less than 100 μm in diameter, which are surrounded by charged ions. Fine bubbles are used in many environmental and industrial processes for solid-liquid separations. They have been used for treatment techniques, removal of pulp fiber, separation of fine particles, protein recovery, deinking of waste water, etc. The important characteristics of microbubbles are their large specific area and small buoyancy; therefore, effective dissolution of gas-phase and high adsorption rate is expected. Microbubbles are the type of bubbles, which consists of gas inside their core, they are separated from each other, so they cannot agglomerate, having a size range of micrometers, usually 1-100 micrometer. There is a lack of research to explore the characteristics of microbubbles in the presence and absence of micro-nano particles and their efficiency in removing them. This work aimed to examine the stability of microbubbles generated with surface-active agents with and without particles. The drainage kinetic study was done for the microbubbles generated in the presence of particles with and without salt for assessing the stability of the microbubble. The effects of some primary parameters on entrainment of particles of ZnO, Al2O3, etc., in a flotation column using microbubbles for enunciating the feasibility of the microparticle separation by microbubble.
Studies on Functionalization of Poly(lactic acid) for Textile Applications
(2022) Hazarika, Doli
The idea of a sustainable environment has led to a path to reduce utilization of fossil fuel-based petroleum products. Enough evidence shows that synthetic fibers, and other plastics do not degrade fully in waste water treatment plants, landfills, and the environment. Sustainable polymers have facile degradation pathways and, in many cases, can be obtained from renewable resources, making them promising alternatives to conventional plastics. Poly(lactic acid),(PLA) is one of the most widely studied sustainable polymers that possess several properties that are comparable to conventional polymers. The present work is a systematic, descriptive study of PLA-based composites in the field of textiles. The reinforcement phase of textile materials developed in this work consists of hybrid materials with modified structure and shape such that resulting products are non-toxic, ecological, and biodegradable. Material selection while designing sustainable products also plays an important role in the engineering field. The hybrid materials are a combination of two materials (organic and inorganic) that can offer benefits to conventional textiles with functional characteristics in order to develop smart textiles for waste water treatment as well as healthcare applications. The combination of organic and inorganic parts deals with both strong (covalent, ionic covalent bond) and weaker (hydrogen, electrostatic, and van der Waals force) interactions. Nanotechnology in textile design is currently based on electrospun polymeric nanofabric to obtain functional properties like high hydrophobicity, high hydrophilicity, self-cleaning ability, dye degradability, shrinkage free characteristic, shimmer, antibacterial, and antiviral properties. The smart components are added to the substrate during The smart components are added to the substrate during fiber spinning, fabric formation level, or during finishing level. PLA functionalization has been fiber spinning, fabric formation level, or during finishing level. PLA functionalization has been carried out by carried out by in situ in situ incorporation of nanohybrid fillersincorporation of nanohybrid fillers during polymerization followed by during polymerization followed by electrospinning to obtain the multifunctional properties for application in waste water treatment electrospinning to obtain the multifunctional properties for application in waste water treatment for a sustainable environment. The thesis also discusses the functionalization finishing approach for a sustainable environment. The thesis also discusses the functionalization finishing approach by obtaining a polymerby obtaining a polymer--hybhybrid composite solution where electrospun fabric is impregnated into rid composite solution where electrospun fabric is impregnated into this solution for application in the the healthcare sector. The choice of a hybrid solution will lead this solution for application in the the healthcare sector. The choice of a hybrid solution will lead to a shimmery nanofinish layer over electrospun PLA nanofabric to tune the properties.to a shimmery nanofinish layer over electrospun PLA nanofabric to tune the properties. Further, Further, for PLA nanofabric, as the big challenge is to achieve dyeing, stability, and superhdrophilicity, for PLA nanofabric, as the big challenge is to achieve dyeing, stability, and superhdrophilicity, the introduction of stereocomplexity on subsequent annealing can be a novel approach using the introduction of stereocomplexity on subsequent annealing can be a novel approach using nanonano--metal oxide to overcome such problems. The modificatmetal oxide to overcome such problems. The modification of crystallization behaviour of ion of crystallization behaviour of highly hydrophobic PLA nanofabric by the incorporation of nanohybrid fillers into the highly hydrophobic PLA nanofabric by the incorporation of nanohybrid fillers into the electrospun solution has also been investigated in this work. The presence of biopolymer electrospun solution has also been investigated in this work. The presence of biopolymer nanocrystals with metal oxide acting as nuclenanocrystals with metal oxide acting as nucleating agent results in the change in crystallization ating agent results in the change in crystallization behaviour. behaviour.
Hydrodynamics of Jet-driven Liquid-liquid Inverse Droplet Flow and its Application for Separation of Organic Contaminants
(2022) Sangtam, Bongliba T
Over the years, the research on the liquid-liquid plunging jet extraction column has drawn significant interest among the scientific fraternity because of its numerous applications, including fine chemical synthesis, recovery of fuel in nuclear plants, acid mixing, ink-jet, and liquid metal transfer (Asadollahzadeh et al., 2016; Gao et al., 2016; Hu et al., 2009; Tadrist et al., 1991). Various researchers have used different columns for the liquid-liquid extraction process such as Kühni column, rotating disc contactor, static mixer, and jet extraction column. Jet mixers have several advantages compared to mechanical mixers because they have low maintenance, low cost, low energy consumption, and shorter mixing time. The jet system has a higher liquid mixing and mass-transfer operation for mixing the liquid-liquid phase. For the past years, the jet device has been employed for wastewater treatment and acid extraction, but the studies were found to be limited. The jet device was used to extract copper ions, and it was discovered that the rate of copper extraction was 7 to 8 times higher than in the CSTR (Dehkordi, 2002a). Suresh et al. (2005) used liquid-liquid jet extraction system and separated uranium and thorium. They have stated that the ejector-type jet device can provide a high extraction efficiency. The various parameters such as liquid-liquid entrainment, drop size and its distribution, axial dispersion coefficient, extraction efficiency, and overall mass transfer play a significant role in designing and modeling of liquid-liquid extraction column. These parameters have an immense impact on selectivity and conversion in chemical engineering applications. Based on the literature, the jet-driven extraction column is gaining popularity for generating interfacial area, intense mass-transfer operations such as gas adsorption, liquid liquid extraction, etc. However, there is a scarcity of studies on hydrodynamics and mass
Experimental Investigations of Flow Behavior in Pulsed Plate Columns Using Radioactive Particle Tracking
(2024) Premsagar, Pillajetti
This thesis investigates the hydrodynamic behavior in Pulsed Plate Columns, which play a crucial role in liquid-liquid extraction processes across diverse industries, including mineral processing, pharmaceuticals, and the nuclear fuel cycle. A pulsed sieve plate extraction column is a vertically oriented separation device that employs alternating fluid pulses to improve component extraction. This is achieved by generating uniform dispersion of droplets from a disperse phase, leading to increased interfacial area for efficient mass transfer. The column utilizes an internal sieve-like plate as a contact stage, facilitating effective separation of compounds through enhanced interaction. Despite their broad applications, there needs to be more experimental data for the local hydrodynamics in these columns. This research is motivated by the aforementioned gap, explicitly focusing on the quantification of mixing. This quantification is achieved by measuring velocity fluctuations within the pulsed plate column under various geometrical and operational parameters. The employment of the Radioactive Particle Tracking (RPT) technique is highlighted in the investigation of a pulsed sieve plate extraction column. The velocity measurements are executed using the RPT, which involves choosing a unit cell zone between two consecutive plates far away from the column's inlet and exit. In this technique, a radioactive particle functions as a tracer, tracking the fluid's movement. The particle's position is recorded over time through six scintillation detectors. Preceding this investigation, studies for optimizing the resolution and sensitivity of detectors are conducted. The application of the RPT technique is then carried out, and the Monte Carlo reconstruction algorithm is employed to measure the Lagrangian track. This track provides valuable insights into the local velocity field within the column.
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.
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.
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.
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.
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
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.
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.
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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