2. Thesis and Dissertations
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Item Hydroxypropyl-Β-Cyclodextrin Modified Nickel Ferrite Nanocomposites For Removal Of Pharmaceutical Pollutants(National Institute of Technology Karnataka, Surathkal, 2022) C K, Smitha; B, Raj MohanThe growth of the pharmaceutical companies has been a boon to the mankind in myriad ways. However, the consequences due to the excess usage of these pharmaceutical compounds in our day-to-day life have resulted in irreplaceable damage to the ecosystem. Researchers have used nanocomposite-based systems for the removal of a wide range of pharmaceutical pollutants from the aqueous systems. Among them the magnetic based silica system has gained momentum due to its ease of synthesis and wide applicability. Nickel ferrite-based silica nanocomposites attached to cysteine and nickel ferrite-based silica nanocomposites attached to aminosilanes were both optimised for their size and morphology. Cysteine coated and amine coated nanocomposites revealed a particle size of 130-150 nm and 50- 100 nm. The physiochemical properties of the nanocomposites were evaluated using different characterization techniques such as TEM, FESEM, XRD, FTIR and TGA. The adsorption studies were performed on both the nanocomposites which revealed a higher adsorption potential of 97.01%, 94.12% and 70.13% for IBF, ACE and STR respectively for aminosilane coated nanocomposite. The nanocomposites revealed a good removal efficiency of ~90% up to 4 cycles with reduction in removal efficiency during the 5th cycle. Hence, aminosilane coated nanocomposites were further grafted with hydroxypropyl- -cyclodextrin to determine the removal efficiency post grafting. The hydroxypropyl- -cyclodextrin grafted nanocomposites (14 mg /L) revealed a very good removal efficiency of 98.01 %, 98.89 %, 98.3 % for IBF, ACE and STR respectively. The nanocomposites also showed good reusability of ~92% for up to 5 cycles thus exhibiting higher pollutant removal in comparison to aminosilane coated nickel ferrite-based silica nanocomposites. The adsorption kinetics for the adsorption seemed to follow pseudo second order reaction kinetics. Also, the Langmuir model of adsorption seemed to fit well with the experimental data confirmation monolayer adsorption process.Item Corrosion Inhibition Studies of GA9 Magnesium Alloy in Chloride and Sulphate Media(National Institute of Technology Karnataka, Surathkal, 2020) Shetty, Sudarshana.; Shetty, A Nityananda.; Nayak, JagannathaThe corrosion behaviour of GA9 magnesium alloy in two different media, namely, sodium chloride and sodium sulphate in different concentrations and temperatures have been studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The effect of pH of the medium on the corrosion behaviour of GA9 magnesium alloy have also been studied in both the media. The results revealed a trend of higher corrosion rate associated with higher medium concentration, lower pH and higher temperature. The corrosion rate in the sodium chloride medium was higher than that in the sodium sulphate medium. Four different alkyl sulfonates namely sodium dodecylbenzenesulfonate (SDBS), sodium 4-n-octylbenzenesulfonate (SOBS), sodium 2,4-dimethylbenzenesulfonate (SDMBS) and sodium benzenesulfonate (SBS) were tested as corrosion inhibitors for GA9. The results pertaining to the corrosion inhibition studies of four inhibitors in two different media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. The inhibition efficiencies of all the four inhibitors decrease with the increase in temperature and increase in the concentration of the media. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and have been documented in the thesis. The sulfonates predominately physisorbed and adsorption was in accordance with Langmuir adsorption isotherm. The studied sulfonates were found to function as mixed type inhibitors. The sulfonates were more efficient at lower temperatures in both the media. Inhibition efficiency is in the order SDBS > SOBS >SDMBS > SBS. Proposed mechanism attributed the cathodic inhibition to the blockage of the reaction spots by chemisorbed sulphonates. The anodic inhibition resulted from the compaction of the porous film by precipitated magnesium sulfonates.Item Studies on Dehumidification Potential of Clay with Additives and Impregnated With CaCl2 Composite Desiccants(National Institute of Technology Karnataka, Surathkal, 2019) Rachayya, Hiremath Chandrashekharayya.; Kadoli, RavikiranThe present work features the preparation and estimation of properties, dehumidification performance assessment and utilization of clay based composite desiccants. Transported clay suitable for pot making is used as desiccant carrier. Composite desiccant is formulated such that transported clay is heat treated (burnt clay) and impregnated with CaCl2. To improve the performance of desiccant carrier, composite desiccants were synthesized using two additives namely saw dust and horse dung. Transported clay are moulded to near spherical shape and are subjected to shadow drying and later dried at higher temperature in a furnace. The heat treatment at 500°C reveals higher weight reduction and porosity. Heat treated desiccants are then characterized by scanning electron microscopy (SEM), Brunauer Emmet Teller (BET) and X-ray diffraction (XRD) techniques. The BET test reveals that clay samples subjected to 500°C posses higher pore volume and clay-horse dung particles exhibit higher surface area. Heat treated desiccants namely clay, clay with 20% saw dust and clay with 20% horse dung are impregnated with CaCl2 solution of 50% concentration by soaking method. The SEM image and elements analysis indicated that the composite desiccant has porous surface and uniform distribution of CaCl2 due to heating at 500°C. XRD pattern indicates the porous nature of burnt clay-additives composite desiccant. The decrease in height of diffraction peaks with CaCl2 impregnation reveals the presence of CaCl2. The variation of thermo - physical properties like thermal diffusivity, specific heat, density and thermal conductivity of burnt clay with and without impregnation of CaCl2 and the effect of additives, namely, saw dust and horse dung at various percentages is investigated. Rapid transient measurement technique is used for the measurement of thermal diffusivity. Specific heat is determined by energy balance. The addition of saw dust and horse dung is seen to increase the specific heat of clay additives with CaCl2 impregnated desiccants. The packed bed performance under the influence of inlet air humidity ratio, and temperature is presented experimentally. The heat of adsorption during the process is low and the bed operates at constant temperature, one dimensional PGC mass transfer model is adopted from conservation principle. The experimental results for reduction in moisture content are compared with theoretical results.iv Adsorption - desorption experiments for moisture removal and addition from atmospheric air are conducted in vertical column in static and fluidized states. The desiccant beds are subjected to an initially set value of process air velocity, relative humidity, temperature and mass of bed. Moisture removal capacity, moisture addition capacity and heat content are the parameter indices adopted to measure the heat and mass transfer characteristics of vertical packed and fluidized bed comprising clay - additives - CaCl2 composite desiccants. On comparing packed and fluidized beds, fluidization improves dehumidification performance and results in higher desorption rates. The results of the experimental study reveals that higher adsorption rates increases the water content of desiccant particles and found to enhance the cooling effectiveness coupled with dehumidification. Irrespective of the clay composite desiccant beds, higher enthalpy of process air exiting the composite desiccant beds is associated with higher adsorptivity. A forced circulation laboratory model desiccant drying system operating in open loop was constructed and arranged. The green pea drying process is divided into two processes involving dehumidification by desiccant bed and grain drying by dehumidified process air. Moisture removal from the process air takes place by vertical packed composite desiccant bed. The grains were dried for process time of one hour. The experimental study reveals average heat content of air entering the dryer is 1.46, 2.46 and 2.38 kJ for burnt clay - CaCl2, burnt clay - horse dung - CaCl2 and burnt clay - sawdust - CaCl2 beds of mass 700 g. The drying is quite sharp during initial process time of 500 s and from then onwards drying of green peas proceeds at constant rate. Finally the potential and perspective of fabricated desiccants in dehumidification and thermal enhancement is being outlined. The key contributions of the present research work highlights the development of low cost composite desiccants using naturally available materials like clay, horse dung and saw dust. These desiccants have potential application in agriculture, HVAC industry, and water extraction from atmospheric air.Item Studies on Removal of Heavy Metals from Aqueous Solution Using Melanin Coated Matrix(National Institute of Technology Karnataka, Surathkal, 2019) Vishnu, M.; Raval, Keyur; B, Raj Mohan.The biopolymer/biopigment Melanin is known for its free radical scavenging property. Melanin obtained from the marine bacteria Pseudomonas stutzeri is used for the removal of Hg (II), As (III), As (V), Pb (II), Cr (VI) and Cu (II) from aqueous medium. The melanin produced by the bacterium is confirmed to be nanoparticle (32 ± 0.98 nm) using TEM and particle size analysis. Different characterisations such as SEM, TGA, DSC, FTIR, BET surface analysis, zeta potential analysis, XRD were conducted to understand the physio-chemical properties of melanin. The kinetic, thermodynamic and equilibrium studies were conducted to achieve the removal of 85%, 87% 92% and 95% Hg (II), Cr (VI), Pb (II) and Cu (II) respectively from water having 10 mg/L adsorbate concentration and 0.2 g/L of adsorbent loading. Trivalent and pentavalent arsenic showed ineffective binding to melanin which was resolved by functionalising melanin using iron and copper. On functionalisation, melanin could remove more than 99 % of As (III) and As (V) from aqueous medium having arsenic concentration of 10 mg/L and loading of 0.8g/L and 2g/L of Fe-melanin and Cu-melanin respectively. For effective heavy metal adsorption and effortless removal of adsorbent from the aqueous medium, melanin nanoparticles were coated on to different matrices and batch removal studies were performed. Adsorption studies using melanin immobilised N, N-diethylacrylamide hydrogel, melanin coated PVDF membrane, melanin impregnated activated carbon were conducted and found that efficient removal of heavy metals was achieved by melanin impregnated activated carbon. Continuous adsorption studies using melanin impregnated activated carbon as a fixed bed column was performed by varying the parameters such as influent flow rate, heavy metal concentration and adsorbent loading in the column. The flow rate of 0.5 mL/min, the heavy metal concentration of 1 mg/L and adsorbent loading of 100 mg were the optimised parameters for efficient heavy metal removal. Thomas model fitted well with the experimental data compared to the Adam-Bohart’s model. Efficient desorption of Hg (II), Pb (II) and Cu (II) were obtained using 3N HCl and Cr (VI) using 1N citric acid. Melanin was re-functionalised after treatment with 5N HCl, and effective reuse of melanin for removal of all heavy metals was achieved until four cycles of study.Item Studies on Corrosion Inhibition of 18% Ni M 250 Grade Maraging Steel under Weld Aged Condition in Acidic Media(National Institute of Technology Karnataka, Surathkal, 2013) B. S., Sanatkumar; Shetty, A. Nityananda; Nayak, JagannathaThe corrosion behaviour of 18 % Ni M250 grade maraging steel under weld aged conditions in two different acid media, namely, hydrochloric acid and sulphuric acid in various concentrations and temperatures have been studied by Tafel polarization and electrochemical impedance spectroscopy techniques. The corrosion rate in the sulphuric acid medium was higher than in the hydrochloric acid medium. Five organic inhibitors were synthesized and characterized using spectral and elemental analysis. The five inhibitors were 1(2E)-1-(4-aminophenyl)-3-(2-thienyl) prop-2-en-1-one (ATPI), 2-(4-chlorophenyl)-2-oxoethyl benzoate (CPOB), 2-(4- bromophenyl)-2-oxoethyl- 4-chlorobenzoate (CPOM), (E)-1-(2,4-dinitrophenyl)-2-[1- (2-nitrophenyl) ethylidene] hydrazine (DNPH) and 5-diethylamino-2-{[2-(2,4- dinitrophenyl) hydrazin-1-ylidene]methyl} - phenol (DDPM). The results pertaining to the corrosion inhibition studies of five inhibitors in two different acid media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and the results have been analysed. The adsorption of first four inhibitors on the alloy was through both physisorption and chemisorption, with predominant physisorption in both the media. The mode of adsorption for the DDPM predominantly chemisorption in both the media. The adsorption of all the five inhibitors on alloy surfaces follows Langmuir adsorption isotherm. The inhibition efficiencies of first four inhibitors decrease with the increase in temperature, the inhibition efficiency of DDPM increases with the increase in temperature.Item Compatibility of Blended Lithomargic Clay as Landfill Liner Materials(National Institute of Technology Karnataka, Surathkal, 2014) Kamatagi, Allamaprabhu S; B. M, Sunil; Nayak, SitaramThe present investigation is an experimental study on locally available lithomargic clay (shedi soil) and blended lithomargic clay as a suitable soil liner material for the effective containment of leachate in landfills. The objectives of the research work were accomplished in three phases. First phase of work deals with geotechnical characterization of test soils. Hydraulic conductivity is considered as most significant factor for performance of a clay liner. Results obtained show that the hydraulic conductivity of lithomargic clay is greater than the suggested limit of k<10-7cm/s by various waste regulatory agencies. To reduce hydraulic conductivity of lithomargic clay, it is blended with black cotton (BC) soil and bentonite at different proportion till the required hydraulic conductivity (k <10-7cm/s) was achieved. Lithomargic clay blended with 5% and 10% of a black cotton soil and, lithomargic clay blended with 5% and 7.5% of a bentonite satisfied the hydraulic conductivity requirement of liner material. Hence blend proportions were considered for further investigation. The compatibility of a clay liner on interaction with contaminant depends on its capacity to retard the migration of contaminants through sorption. In the second phase studies related to adsorption characteristics of soil samples through batch tests have been carried out. The experimental results of batch adsorption tests have been analysed using three adsorption isotherms. Adsorption coefficient of study soils shows that, adsorption of potassium, lead and nickel are more on BC soil and bentonite while lithomargic clay adsorbs more chloride and chromium. As a result blending of lithomargic clay with BC soil and bentonite, the adsorption of contaminants is found to be more in the blended soils compare to parent soil. In the third phase of the research work, the effect of interaction of leachate on behaviour of lithomargic clay and blended lithomargic clay has been studied. The hydraulic conductivity has been found to decrease in both, the natural and the blended lithomargic clay due to the leachate interaction. Blended lithomargic clays has been found to be beneficial in terms of achieving lower hydraulic conductivity, adequate strength, minimal potential to shrinkage. All these properties make blended lithomargic clay as a potential soil liner material for various geoenvironmental applications.Item Studies on corrosion inhibition of 18% Ni M 250 grade maraging steel under welded condition in acidic media(National Institute of Technology Karnataka, Surathkal, 2014) Kumar, Pradeep; Shetty, A. NityanandaThe corrosion behaviour of 18% Ni M250 grade maraging steel under welded conditions in two different acid media, namely, hydrochloric acid and sulphuric acid in various concentrations and temperatures have been studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The corrosion rate in the sulphuric acid medium was higher than in the hydrochloric acid medium. The effect of corrosion inhibition on welded maraging steel was carried out by using five inhibitors, n a m e l y , 2,5-Bis (3,4,5-trimethoxy phenyl)-1,3,4-oxadiazole (BTPO), 1-Phenyl-4-(4-nitrophenyl) thiosemicarbazide (PNPT), 3,4,5-Trimethoxy benzoicacid(3,4,5-trimethoxy-benzylidene) hydrazide (TBTBH), 2-(5-Chloro-1Hbenzoimidazol-2-yl) phenol (CBP), 2-(4-Methoxy-phenyl)-benzo[d]imidazo[2,1-b] thiazole (MPBIT). The results pertaining to the corrosion inhibition studies of five inhibitors in two different acid media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and the results have been analysed. The adsorption of all five inhibitors on the alloy was through both physisorption and chemisorption, with predominant physisorption in both the media. The adsorption of all the five inhibitors on alloy surfaces follows Langmuir adsorption isotherm. The inhibition efficiencies of all five inhibitors decrease with the increase in temperature and increase in concentration of acidic media.