http://localhost:8081/jspui/handle/123456789/15070 2025-07-18T09:17:28Z 2025-07-18T09:17:28Z Gupta, Pragya http://localhost:8081/jspui/handle/123456789/15460 2022-10-12T07:03:07Z 2022-04-01T00:00:00Z

Title: PREPARATION AND PROPERTIES OF NANOFIBRILLATED CELLULOSE BASED AEROGEL WITH PARTICULAR REFERENCE TO THERMAL SUPER INSULATION APPLICATION Authors: Gupta, Pragya Abstract: Thermal insulation is one of the most important tools to save energy, thus reducing greenhouse gas emissions. Researchers are working on active and passive energy-saving techniques. From this concept, the research was motivated to synthesize a material that will be abundantly available and does not harm the environment during processing and installation. Nanotechnological utilization of biomaterial such as wood for advanced superinsulation is an intense area of current research. The key challenges of insulation such as thermal resistance, low density, high porosity, and temperature effect on the mechanical properties have been discussed in the thesis. Low density and high strength nanofibrillated cellulose (NFC) aerogel based on pinewood were prepared by the freeze-drying method. The study was focused on reducing the thermal conductivity of the prepared aerogel along with the improvement in mechanical strength. Synthesized NFC aerogel has demonstrated high porosity (99.4%) and ultra-low density (8.1 kg/m3). Morphological analysis of aerogel by FESEM (Field emission scanning electron microscope) confirmed nano-dimensional diameter of cellulosic fibers and pore size distribution of aerogel in the range of 2-50 nm. X-ray microtomography confirmed the three-dimensional, monolithic and porous structure. The mechanical and thermal transport properties of aerogel have been tailored via controlling the concentration of NFC in the hydrogel. The synthesized aerogel acts as a thermal insulator with thermal conductivity of 25.5 mW/m K at 1.00 wt% of aerogel, which is near the thermal conductivity of air in ambient conditions. NFC aerogel would be a candidate for practical applications such as heat insulators, kinetic energy absorbers, and energy-efficient buildings. Afterward, flame retardancy and thermal insulating properties of sepiolite clay and NFC-based aerogel have been discussed. Due to the fragile characteristic of sepiolite-based aerogel, nanofibrillated cellulose has been introduced into the clay to make it a monolithic composite aerogel. The prepared hybrid aerogel has been modified with a hydrophobic precursor, i.e., Methyltrimethoxysilane (MTMS). The prepared specimens have shown the typical properties of aerogels like low density (11.5 kg/m3 to 32.5 kg/m3), high porosity (99.2 to 98.7%), and good dimensional stability. Vertical burning test along with V-0 performance, horizontal burning test, and flame penetration have confirmed its thermal shielding and flame retardancy. Apart from that, the aerogel had chances to improve its mechanical and thermal properties. For this specific requisite, many literature surveys were done based on several types of aerogel devoted to thermo-mechanical properties. The improvement was found by the in-situ synthesis of NFC / polymethylsilsesquioxane (PMSQ) aerogel. The NFC-PMSQ aerogels were prepared by optimizing precursors, surfactants, and base catalysts. The rheological premonitory of hydrogel has been performed to predict the physical properties (i.e., density, mechanical properties) of aerogel. Van-Gurp Palmen's plot of hydrogel has represented a relationship between complex modulus and phase angle. This study establishes that hydrogel's premonitory analysis could compare aerogel's physical properties without drying and further analysis. The chemical structure of the aerogel was studied by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Solidstate nuclear magnetic resonance (NMR). X-ray microtomographic analysis (XMT) confirmed the homogeneous and monolithic structure of aerogel. The lowest thermal conductivity was achieved as 23.21 mW/m K with V-0 and HBF rating through UL-94 test. The thermal performance of aerogels was cross-verified through modelling and simulation in the COMSOL multiphysics platform. The mechanical properties of aerogel were evaluated by monolithic compression test in axial and radial compression test up to 90% strain, cyclic compression loading-unloading-reloading test, and flexural test. Further, the present work emphasizes the particular application i.e., building insulation. The NFC-sepiolite-PMSQ aerogel was synthesized with improved mechanical, thermal insulation, flame resistance, etc. Conformal coating through PLA was done on the aerogel, which assisted in drastically enhancement in the aerogel properties. The aerogel holds a combination of properties such as ultralow thermal conductivity (18 mW/mK), high mechanical properties (600 kPa) at different climatic conditions, high flame retardancy and low density, etc. For a clear visualization of real field application, a small prototype of the house was prepared in the laboratory. The house was simulated for real field application. There was a 11ºC temperature difference in the middle of the room after using aerogel insulation for a long duration of time. Hence, we can save energy for cooling the room using aerogel on the exposed surface. As well as the prepared material will also protect from the environmental burden. Overall, our prepared nanofibrillated cellulose based composite has shown a candidate material for building thermal insulation.

2022-04-01T00:00:00Z Chaudhary, Mohit http://localhost:8081/jspui/handle/123456789/15184 2021-11-30T16:34:37Z 2019-10-01T00:00:00Z

Title: FLUORIDE REMOVAL FROM WATER USING NANOADSORBENTS AND MIXED MATRIX MEMBRANE Authors: Chaudhary, Mohit Abstract: Fluoride contamination in water occurs either through the natural weathering of rocks or anthropogenic activities. Wastewater from various industries like glass manufacturing, fertilizer, electroplating, and steel producing industries can also contribute excess fluoride in water bodies. In general, fluoride concentrations in industrial wastewater found to be in the range of few hundred to thousands mg/L while in groundwater, it is found only in the range of 1 to 40 mg/L. Fluoride in drinking water is not completely forbidden. At lower concentrations (0.5 to 1.5 mg/L), fluoride is beneficial for bone health but concentration more than 1.5 mg/L can have severe health effects such as dental and skeletal fluorosis. This research work deals with fluoride removal from contaminated water having very high and low fluoride content. Initially, calcium hydroxide nanorods (CHN) were synthesized through the ultrasonic-assisted chemical method to remove fluoride from wastewater having high fluoride concentration. The BET surface area, Barrett-Joyner-Halenda (BJH) surface area, pore volume and average pore diameter of CHN were found to be 367 ± 10 m2/g, 501 ± 8 m2/g, 0.54 ± 0.02 mL/g, and 4.4 ± 0.1 nm, respectively. Experimental data was applied to Freundlich, Langmuir, Temkin, and Two-step adsorption isotherm models, but neither model fits well to the experimental data. Dissolution and precipitation of calcium ions (from CHN) with fluoride ions under various experimental conditions along with the little extent of adsorption were found the main mechanism for F- removal. Batch study of fluoride removal using CHN reveals that with an initial fluoride concentration of 50–250 mg/L and fixed CHN dose of 0.12 g/L, fluoride removal was found to be 450 ± 10 mg/g within the 45 min of contact time at pH ∼6.5. The fluoride adsorption kinetic data was applied to pseudo first order and pseudo second order kinetic models. Fluoride removal follows pseudo second order kinetics in this study. Pseudosecond order rate constants at initial acidic and basic pHs of 4.5 and 9.5 were found to be 0.00041 (g/mg-min) and 0.00116 (g/mg-min), respectively. Surface complexation model was applied at equilibrium pHs of fluoride contaminated solutions, and mainly precipitation of calcium and fluoride ions was found here as a governing mechanism for removal of fluoride ions. Fluoride removal study was performed successfully using synthetic F- spiked solutions and electroplating industrial wastewater in a wide range of pHs (2–12). The aqueous solution with an initial fluoride concentration of 550 mg/L was treated with 2 g/L of CHN and 99.30 % fluoride removal was achieved. It is commonly known that nanoparticles are highly efficient fluoride adsorbents, but agglomerate easily due to their high surface activity and are difficult to separate from the ii aqueous medium after use. Mixed-metals oxyhydroxides nanoparticles were prepared into a natural polymeric matrix of chitosan to overcome such a problem of agglomeration. Hydrous mixed-metal oxyhydroxides, loaded chitosan composite (Fe-Al-Mn@chitosan) was prepared using abundantly available laterite clay and waste from the steel industry via co-precipitation method. Fe-Al-Mn@chitosan exhibited maximum F- adsorption capacity of 40±0.5 mg/g, while if only the inorganic mass fraction of composite is considered, the same value could be reached to 55±0.5 mg/g. Fluoride adsorption on Fe-Al-Mn@chitosan follows the pseudo second order kinetics with rapid adsorption. No significant effect of other competitive ions was observed on F− adsorption using Fe-Al-Mn@chitosan composite. The composite adsorbent is found to be effective in producing drinking water from fluoride contaminated groundwater. Afterward, shrinking core model is applied to predict the adsorption kinetics of fluoride ions on mixed metal oxyhydroxide and mixed metal oxyhydroxide loaded chitosan composite to investigate the effect of polymeric barrier’s resistance on mass transfer of fluoride ions from the external surface to interior pore surface of the adsorbent. For nanoparticles and nanocomposites, the reaction between adsorbate and adsorbent is much faster near the external surface than in the interior pores surfaces of the particles. Adsorption kinetic study of both adsorbents reveals that Fe-Al-Mn@chitosan composite is more efficient than mixed metal oxide nanoparticles alone. The unknown parameters of external mass transfer coefficient (Kf) and pore diffusion coefficient (De) were estimated by comparing the simulated concentration profile with the experimental data using a nonlinear optimization technique. Adsorption kinetic modeling using shrinking core model reveals that 28 % of total adsorption front radius was accessible to fluoride ions in the case of Fe-Al-Mn mixed metal oxyhydroxide while for Fe-Al- Mn@chitosan; more than 80 % of total adsorption front radius was accessible for fluoride ions. The value of De is found to be almost in the same order for both the adsorbents proving that the polymer layer provides minimum resistance barrier to the mass transfer of F- ions from external surfaces to interior pore surfaces. Further, faster and more extent of adsorption for composite is observed due to smaller particle sizes of nanoparticles present inside of composite than nanoparticles alone (due to the natural tendency of agglomeration of nanoparticles). The practical applicability of developed composite material was explored through Fe-Al- Mn@chitosan composite loaded cellulose acetate mixed matrix membrane (MMM). The compatibility of the two polymers namely chitosan and cellulose acetate, helps to obtain homogeneous dispersion of the nanoparticles inside the MMM. Fe-Al-Mn@chitosan loaded cellulose acetate-based MMM (optimum membrane: M8) showed significantly higher treatment capacity (4000 and 2000 L water per m2 for low ionic strength fluoride contaminated distilled iii and groundwater as feed, respectively) compared to performance of other MMM reported in the literature. It is commonly known that the performance of any MMM is limited by adsorption process and shows low sustenance time. This drawback of MMM has been addressed in the present study. In this study, fluoride ions rejection happened through adsorption at the initial time of operation. Subsequently, the development of negative charges on membrane surface through adsorption of F- ions might cause the electrostatic repulsion based F- rejection mechanism; as a result, MMM showed much higher fluoride rejection compared to the performance expected based on adsorption phenomenon. The infectious test reveals that the MMM membrane is less susceptible to microbial attack compared to the cellulose acetate membrane. Fluoride rejection through membrane confirms that mixed oxide nanoparticlespolymer- composite loaded MMM is capable of removing F- from water quite efficiently and has shown very interesting fluoride rejection behavior through electrostatic repulsion during ultrafiltration mode of operation.

2019-10-01T00:00:00Z Chandra, Rajesh http://localhost:8081/jspui/handle/123456789/15183 2021-11-30T16:31:34Z 2019-09-01T00:00:00Z

Title: REMEDIATION OF WASTEWATER AND BIOFUEL PRODUCTION USING MICROALGAE Authors: Chandra, Rajesh Abstract: Increasing concentrations of carbon dioxide and other harmful gases into the environment from various sources like combustion of fossil fuels and thermal power plants, etc. are posing threat to the environment continuously. Fast growing population, urbanization and industrialization have led towards increase in energy demands across the world. Increasing energy demands have drawn attention of researchers towards the development of renewable energy sources. Fuels derived from biomass like biodiesel, bioethanol and biogas, etc. could be the possible substitutes of traditional energy resources in the near future. Increasing population, urbanization and industrialization are the major factors behind different types of environmental problems with generation of huge volume of wastewaters from municipal and industrial areas. Safe disposal of these wastewaters is a tedious task. Globally the consumption of water for domestic and industrial purposes is 450 billion m3 year-1, where domestic sector alone contributes to 315 billion m3 year-1 which is 70% of total water consumption. Usually wastewater discharges from industries have high organic loading, nutrients, toxic organics (xenobiotics), and heavy metals, etc. These pollutants have serious impact on human health, aquatic life and soil microbiology. However, inorganic and organic nutrients present in the wastewaters can be used as substrate for the of growth microorganisms. Biomass obtained from such micro-organisms can be utilized in the production of value added products like biodiesel, bioethanol, pharmaceuticals and proteins, etc. Open literature indicates that significant work has been accomplished to enhance microalgal biomass and lipid production. This thesis is focused on evaluating and demonstrating potential of microalgae for remediation of wastewaters and production of biodiesel. Four freshwater microalgae namely Chlorella minutissima (C. minutissima), Scenedesmus abundans (S. abundans), Nostoc muscorum (N. muscorum) and Spirulina sp. have been used for remediation of dairy, distillery and secondary treated wastewater contaminated with phenols. Batch experiments were performed in laboratory using conical flasks as photobioreactor. Among the four microalgae species C. minutissima was found the most efficient and promising microalga for production of biodiesel. Optimum temperature and light intensity observed for C. minutissima were 27 ± 2 ℃ and 9000 lux, respectively. At these conditions C. minutissima obtained highest biomass and lipid yield of 1840 and 405.36 mg/L, respectively when grown on modified CHU-13 medium. Remediation of distillery wastewater in combination with secondary treated domestic sewage was also performed using C. minutissima. Increase in biomass and lipid yield was observed with the addition of glucose in the cultivation medium. C. minutissima iv achieved highest biomass and lipid yield of 5.23 ± 0.065 g/L and 976 mg/L, respectively, when cultivated on 25% distillery spent wash containing 20 g/L of glucose. Furthermore, remediation of secondary treated wastewater contaminated with different phenols (1,2-dihydroxy benzene, 2,4-dinitrophenol, 2,4-dichlorophenol and 2-chlorophenol) was also assessed using C. minutissima. Removal of phenols by C. minutissima and effect of different phenols on biomass and lipid yield of microalga were observed in presence and absence of additional organic carbon sources like glucose and glycerol. Highest removal of phenol (1,2-dihydroxy benzene) was achieved at 25 mg/L concentration in cultivation medium. Dairy wastewater remediation was also performed using different poly-microalgae cultures of C. minutissima, S. abundans, N. muscorum and Spirulina sp. Polyculture (C. minutissima + N. muscorum + Spirulina sp.) achieved 75.16, 61.37, 58.76, 84.48 and 84.58% removal of BOD, COD, total nitrogen (TN), total phosphorus (TP) and suspended solids (SS), respectively when cultivated on dairy wastewater diluted with 30% secondary treated domestic sewage at 12:12 h photoperiod along with biomass and lipid yield of 3.47 ± 0.07 g/L and 496.21 mg/L, respectively, in 10 days of cultivation period.

2019-09-01T00:00:00Z