2. Thesis and Dissertations
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/1/10
Browse
2 results
Search Results
Item Development of Novel Photocatalytic Reactor for Dye Wastewater Treatment(National Institute of Technology Karnataka, Surathkal, 2020) Das, Suman; Mahalingam, HariOver the years, industrial development has increased, causing a rapid increase in all form of pollution. A large amount of organic waste released into the freshwater bodies have increased water pollution several folds. In this regard, an effective environmentally friendly process for wastewater treatment is urgently needed, because sometimes it is difficult to degrade different toxic pollutants efficiently by conventional methods. Photocatalytic nanoparticles are an excellent choice for the mineralization of organic pollutants present in wastewater. The use of the photocatalyst nanoparticle into a reactor is also challenging since a light source is compulsory to activate the catalysts. In this work, TiO2, rGO, g-C3N4 and TiO2/rGO/g-C3N4 mixture in two forms: an admixture and chemically synthesized composite photocatalysts were immobilized in polystyrene films and employed as a photocatalytic film. The characterizations were done using SEMEDX, FTIR, XPS, XRD, ICP-OES, BET-Surface area analyzer, particle size analyzer, band-gap analyzer, etc. Initially, the photocatalytic performance of the prepared TiO2 polystyrene film was checked followed by (TiO2, rGO, and g-C3N4)-admixture and then TiO2/rGO/g-C3N4-chemical composite. The photocatalytic oxidation of synthetic dye wastewater (Remazol Turquoise Blue) under ultra-violet and sunlight irradiation was carried out in different types of photocatalytic reactors (batch, scaled-up a batch with recirculation, and multiphase reactors). The reactor volume was varied from 200 to 2900 mL, and the degradation of Remazol Turquoise Blue was confirmed by TOC and HPLC analysis. The optimization of photocatalytic reaction parameters (effect of catalyst loadings, pH, initial dye concentration, light source, polystyrene photocatalytic film thickness, recyclability the film, oxidizing agents, etc), as well as the reactor parameters (recirculation rate, air flow rate, diameter ratio, etc), were investigated in detail systematically. The synergistic effect of the photocatalysts was also analyzed by using the admixture of the photocatalysts, which showed a great significance in this work. The photocatalytic treatment of RTB dye under optimized conditions shows that there was more than 90% decolorization in most of the reactors after 90 min of irradiation. Amongii various reactors used in this study, the multiphase photocatalytic reactor has unique way to utilize the photocatalyst, which makes it novel and efficient. Also, the multiphase reactor showed the best performance since the observed decolourization and degradation were almost same. To make this study cost-efficient and suitable for large scale application, waste polystyrene was used as a substrate material instead of pristine polystyrene. This work presents a simple, easy, economical, and eco-friendly way to deal with the toxic organic pollutants. The photocatalytic reactors used in this work are highly efficient and can be easily scaled up for the industrial-scale application and employed for any other organic pollutant present in the water.Item Biobased synthesis of silver and titanium dioxide nanoparticles and their applications(National Institute of Technology Karnataka, Surathkal, 2016) Devadiga, Aishwarya; K, Vidya Shetty; Saidutta, M. B.Silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2-NPs) have found wide range of applicability in engineering, healthcare, consumer goods, pollution abatement and electronics. Biobased routes for their synthesis is gaining prominence, as they are safer and environmental friendly routes with low chemical footprint compared to physical and chemical routes. In the present research work, the plant sources such as leaves of Terminalia catappa and Tectona grandis Linn F leaves were selected based on their ability to synthesize AgNPs. The bacterial sources were isolated from the silver rich environment based on their ability to reduce the silver ions extracellularly and were identified as Brevundimonas vancanneytii, Leucobacter aridicollis, Enterobacter cloacae and Alcaligenes aquatilis. AgNPs could be synthesized effectively using aqueous extracts of the leaves and the cell free culture supernatants of these bacterial strains. Extracellular TiO2-NPs were also synthesized using the bacterial cell free culture supernatants. The synthesis parameters influencing the conversion of precursor ions and the morphological characteristics such as size, shape, isotropy and monodispersity of the nanoparticles being synthesized were studied and optimized. In plant based synthesis, plant bioactive components acted as reducing and capping agents, while the bacterial based synthesis was brought about by the extracellular enzymes. AgNPs and TiO2- NPs synthesized in the present research work were found to be capped with biobased moieties which imparted stability to the particles. The AgNPs exhibited antibacterial efficacy and colorimetric mercury sensing property, while the TiO2-NPs exhibited photocatalytic activity. Crystalline AgNPs synthesized with a conversion of 98.98% using the bacterial strain Alcaligenes aquatilis were of average particle size of 23±0.9 nm, isotropic, quasispherical shaped along with narrow size range and exhibited the best antibacterial property and colorimetric mercury sensing ability as compared to other AgNPs synthesized. TiO2-NPs synthesized using the cell free culture supernatant of the same bacterial strain were isotropic, monodispersed, quasi spherical shaped, and with an average size of 4.0±0.5 nm containing brookite phase of titania. They exhibited higher photocatalytic activity as compared to Degussa P-25 in terms of degradation of Acid blue and Remazol brilliant blue R dyes, with complete degradation of 50 mg/L of dyes in 120 min. Thus the process developed in the current study could harness the biobased components from the selected plant and bacterial sources for the synthesis of AgNPs and TiO2-NPs under ambient conditions with promising large scale applicability.