Thesis & Dissertations

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3d Printing of Biodegradable Poly (Butylene Adipate – Co – Terephthalate) / Hydroxyapatite Nanocomposites
(Department of Chemestry, 2020) Acharya, Arun
In this work, the hydroxyapatite (HA) biomaterial from a bio-waste namely the buffalo bone was prepared in simple and environmentally friendly way. It was characterized by Fourier Transform InfraRed (FTIR), X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX) and Scanning Electron Microscope (SEM) analyses. The average sizes of the nanoparticles were found in the range 8-41 nm as calculated by Debye-Sherrer’s formula. FTIR spectra confirmed the presence of major functional groups (PO4 vi 3- and OH - ) in prepared HA samples, with small additional peaks of carbonate ion (CO3 2- ). The SEM micrograph showed the formation of small rod-like crystals in the agglomerated particles were presented in as-dried HA powders with size ranges from 1.75 to 2.72 μm. In addition, the micrographs show morphologies for all samples with fine particles and pore size details ranges from 31.3nm to 101nm provides good agreement to be used in a biomedical application. To make the nanocomposite, HA was macroscopically uniformly distributed over poly(butylene adipate-co-terephthalate) (PBAT) by solvent casting method with the help of magnetic stirrer. By using nanocomposite, the filament for 3D printer was prepared by Noztek machine. Finally, button like structure was prepared by using 3D printer and it was investigated by water adsorption, Biodegradibility and anti-microbial test. The addition of HA brought improvements in stiffness of PBAT, due to high interactions between the carbonyl groups of the polymer matrix and the hydroxyl groups of HA. As the percentage of HA in composite increased, the water absorption percentage of nano-composite also increased. Also, degradation test showed that weight loss percentage gone to decrease with increased percentage of HA in composite. Therefore, this biomaterial has great potential for applications in regenerative medicine as a support for bone growth. Keywords: Hydroxyapatite (HA), Crystallinity, Porous, 3D Printing, Solvent Casting, Biodegradability, Water Absorption, Hydrophilicity
Adsorption Behaviour of Chromium(Vi) onto Surface Modified Sugarcane Waste
(Department of Chemistry, 2009) Wagle, Deepak
An effective chemically modified adsorbent based on sugarcane wastehas been prepared by treating with concentrated sulphuric acid in 2:1weight:volume ratio. Thus prepared adsorbent has been found to be effective in theadsorption of chromium from aqueous medium. The efficacy of the adsorbentin the removal of chromium was evaluated by batch adsorption method. Theeffect of initial concentration, contact time and pH of the solution wasinvestigated. The maximum adsorption capacity onto this adsorbent wasfound to be 195 mg/g at their optimal pH 1 at which unmodified bagasse hasonly 58 mg/g. The characterization of adsorbent was done by determiningsurface area and Boehm’s titration method. Freundlich isotherm and pseudo-second order kinetic model gave better explanation of the adsorption process.
Adsorption of Arsenic(III) Using Iron(III)-Loaded Modified Sugarcane Begasse
(Department of Chemistry, 2009) Aacharya, Sabita
Arsenic is a toxic element and may be found in natural water as well as industrial wastes. Leaching of As from industrial wastes into ground water may cause significant contamination which requires proper treatment before its use as a drinking water. The chemistry of As and its natural occurrence in some water resources combine to create a potent, widespread human health risk, requiring management and removal from drinking water. The present study describes the removal of As(III) from water. Of the available conventional techniques, adsorption is the most versatile and effective separation technique and utilizes agricultural and natural waste as adsorbent. The study mainly focuses on the removal of As(III) on Fe(III) loaded modified Sugarcane begasse in batch studies as a function of pH, dosage of adsorbent and contact time. Kinetics revealed that the uptake of As(III) ion by rapid and equilibrium time was independent of initial As(III) concentration and the adsorption process followed a pseudo second-order kinetics equation. The As(III) was strongly dependent on pH and dosage of adsorbent. The adsorption isotherm best fit the Langmuir equation as compared to Freundlich.
Adsorption of Cd (II) From Aqueous Solution by Activated Charcoal Derived from Lapsi Seeds
(Department of Chemistry, 2009) Lamsal, Nirma
The potential and effectiveness of activated carbon derived from carbonization of Lapsi (Choerospondias axillaris) seed for adsorptive removal of cadmium (II) was examined by adsorption technique. The carbon obtained from Lapsi seed was chemically modified by treating with 1:1 HNO3 at 60o C. Boehm method was used to estimate the oxygen containing acidic functional groups. The acidic functional group, specific surface area and adsorptive capacity all greatly increased with chemical treatment with nitric acid. The specific surface area of the charcoal, after chemical treatment, increased to 600 m2/g from 45 m2/g. The ash, moisture and carbon contained in modified charcoal were found to be 3.5%, 0.2 % and 96.3 % respectively. The performance of the adsorbent was in par with commercial activated charcoal. Various parameters such as contact time, adsorbent dose, pH and metal ion concentrations on adsorption were studied, optimized and applied in the present study. The maximum adsorption capacity of charcoal to adsorb Cd(II) was found to be 12.53 mg/g at optimum pH of 6 and equilibrium was attained within 150 minutes. The adsorption of cadmium followed pseudo second order kinetic model and the rate constant of the process was found to be 1.73x10-3 g mg-1 min-1. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich isotherm.
Adsorptive Removal of Fe (II) From Aqueous Solution by Functionalized Sugarcane Bagasse
(Department of Chemistry, 2010) Acharya, Mahendra
In the present study, adsorption of Fe(II) onto different biosorbents prepared from sugarcane bagasse, i.e, raw sugarcane bagasse, charred sugarcane bagasse and phosphoric acid modified charred sugarcane bagasse has been studied by batch equilibration method under different experimental conditions. Effects of pH, Fe(II) concentration, and contact time on the adsorption of divalent iron ion were investigated. The concentration of Fe(II) ion in the test solution was determined spectrophotometrically. Maximum adsorption was observed at pH 2.5 for all the adsorbents at the optimum contact time of 9 hour, 7 hour, and 4 hour respectively for RSB, CSB and PCSB. Maximum adsorption capacity (qmax) value for the RSB, CSB and PCSB was found to be 50.5, 111.4 and 175 mg/g respectively. Adsorption of the Fe(II) ion on all the adsorbents followed Langmuir isotherm more strictly than Freundlich isotherm. The results shows that studied adsorbents may be attractive low cost alternative for the treatment of wastewater in lower concentration of iron.
Adsorptive Separation of Heavy Metals onto Xanthated Apple Waste From Aqueous Solution
(Department of Chemistry, 2006) Bashyal, Deepak
Biosorption is potentially an attractive technology for the treatment of wastewater retaining heavy metals in aqueous solution. This study investigated the feasibility of chemically modified apple waste as a novel type of biosorbent for lead, cadmium, zinc and Iron removal from aqueous medium. Xanthated apple waste as a biosorbent was prepared by simple chemical reaction with carbon disulphide under alkaline condition. The maximum exchangeable cations of the H V + -form xanthated apple waste (XAWgel) were as high as 2.52 mol/kg. The effect of pH, sorption kinetics, effect of competitive ion and isotherm were studied by batch method. The significant effect of pH was in the range of 3 to 6. Time dependency experiments for the metal ions uptake showed the biosorption rate was fast initially for 2h, followed by slow attainment of equilibrium. Sorption isotherm test showed that equilibrium sorption data were better represented by Langmuir model than the Freundlich model, and the maximum adsorption capacity of Pb(II), Cd(II), Zn(II) and Fe(III) were found to be 250, 192.30, 123.45 and 62.89 mg/g respectively. The pseudo first-order, pseudo second-order, and secondorder models were used to analyze the kinetic data. The good correlation coefficient was obtained for pseudo second-order kinetic model. XAW-gel was found to be more efficient than the conventionally used adsorbent activated carbon and other most of the biosorbent. Based on the result, a judicious choice of modification strategy for raw apple waste precursors can produce adsorbent with active xanthated surface functional groups and appears to be a promising biosorbent for removal of heavy metals from aqueous water.
Biological and Phytochemical Studies on Some Medicinal Orchids of Nepal
(Department of Chemistry, 2012) Marasini, Ramesh
Biological and phytochemical screenings of some orchid species growing in Nepal were studied. The ethanolic extracts of orchid species were tested against both gram positive and gram negative standard bacterial strains viz. Vibrio cholerae, Staphylococcusaureus, Klebsiella pneumoniae, Bacillus subtilis and Escherichia coli. All orchid extracts showed good bacterial Zone of Inhibition(ZOI) against Staphylococcus aureus. The crude extracts of Pholidota imbricata and Coelogyne cristatawere shown highest activity against Vibrio cholerae (ZOI -14 mm) and Staphylococcus aureus(ZOI –14 mm) respectively. The MIC and MBC value of the extracts of Pholidota imbricata and Coelogyne cristata were found to be 62.5 mg/ml and 31.25 mg/ml, 125 mg/ml and 250 mg/ml respectively. Only Pholidota imbricata and Pholidota articulata extracts were shown fairly good activity but all others extracts were shown very less activity or even failed to show any activity against fungal organisms viz.Candida albicans, Rhizopus stolonifer and Mucor spp. From the ethanolic extracts of orchid species, phytocon stituents detected qualitatively were Alkaloids, Terpenoides, Flavonoides, Tannins, Reducing sugars and Cynonogenicglycosides.
Biological and Phytochemical Studies on Heartwood of Acacia catechu of Nepal
(Department of Chemistry, 2011) Subedi, Yagya Prasad
Biological and Phytochemical screening of heartwood of Acacia catechu was studied. Phytocostituents found were Sterols, Flavones Aglycones, Tannins and Polyphenols. The column chromatography of diethyl ether fractions result in the isolation of β-Sitosterol (Ac1), Quercetin (Ac4), (+) Catechin (Ac6). Other four compounds Ac2, Ac3, Ac5, Ac7 whose work is on progress, were also isolated. Antibacterial screening, antifungal screening and brine shrimp bioassay of different fractions showed that hexane, chloroform, diethyl ether, ethyl acetate and methanol fraction were biologically active. In brine shrimp bioassay only diethyl ether, ethyl acetate, and methanol fraction showed activity.
Biological Studies of Some Selected Medicinal Plants from Kathmandu Valley and Isolation of Chemical Compounds
(Department of Chemestry, 2021) Kapali, Junu
The aim of this study is to investigate the phytochemical and biological properties of some selected medicinal plants from Kathmandu valley and isolation of phytoconstituents from active plant extract. The methanolic extracts of Ageratina Adenophora, Cupressus sempervirens and Lantana camara aerial parts were analyzed for their phytochemical analysis, toxicity test, antioxidant activity, total phenolic and total flavonoid content, antidiabetic properties and isolation of chemical constituents from active plant fraction and FTIR analysis. The toxicity test was studied by brine shrimp lethality test. The antioxidant potential was evaluated by DPPH radical scavenging assay. The amount of total phenolic and flavonoid was estimated with the Folin-Ciocalteu reagent and aluminium chloride method, respectively. The α amylase enzyme inhibition activity was performed to evaluate the inhibition percentage for each extract. The phytochemical analysis showed the presence of various secondary metabolites like alkaloids, flavonoids, carotenoids, coumarins, glycosides, polyphenol, carbohydrate, saponin, tannins, terpenoids, quinones, and volatile oil & fats. The methanolic extracts of Ageratina adenophora was found to be cytotoxic against brine shrimp as shown by its LC50 value of 833.68 µg/mL. The methanolic extracts of Lantana camara (106.179 ± 11.390 µg/mL) showed the strongest DPPH radical scavenging activity as its IC50 values were close to standard ascorbic acid (17.456 ± 0.822 µg/mL). Lantana camara showed the highest phenolic (10.2 ± 0.343 mg GAE/g) and flavonoid content (1.872 ± 0.16 mg QE/g) respectively. In addition, Ageratina adenophora methanolic extracts were found to inhibit enzymatic activity of α-amylase under in-vitro starch digestion bioassay with the IC50 value of 1.843 ± 0.007 mg/mL. The FTIR measurement revealed the presence of C=O, O-H and C-H stretching bands at the functional group region. Keywords: Phytochemical, antioxidant, phenolic, flavonoid, antidiabetic, αamylase.
Chemical Analysis, Biological Activities, and Green Synthesis of Silver Nanoparticles Using Bioactive RHUS Chinensis Mill Extracts
(Department of Chemistry, 2023) Bhusal, Manisha
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Comparative Study on Determination of Percentage Purity and Essential Elements on Rock Salt Samples of Different Origins
(Department of Chemistry, 2019) Pandeya, Saraswati
Black and white rock salts are one of the highly used ingredients in daily meal and different types of food industries. Black rock salt is called as bire noon and white rock salt is called as sinde noon in Nepali. These rock salts are being highly used in herbal formulations too. Rock salts of Indian and Tibetan origins are primarily found in Nepalese market. Salt of Nepalese origin, available from Mustang district, is also sold in market. Majority of these salt samples are found to be sold in unprocessed form. Hence, it is likely that these samples may have different level of toxic impurities. Salt containing high amount of essential elements is considered to be of high nutritional value. Therefore, information on level of toxic impurities and essential elements in the salt samples is an important task to know nutritional value of any salt. However, such information on salts of Nepalese market is not available in literature. The amount of sodium in the black salt sample determined potentiometrically was found to be in the range of 30-37mg/100mg of salt sample. In white salt samples, relatively lower amount of sodium in the range of 23-35mg/100g was obtained. Iron was detected in all the collected white and black rock salt samples. The amount of iron in the black and white salt samples was found to be in the range 12-24 and 7-14 ppm, respectively. This tells that black salt is better source of iron than white salt. The low level of magnesium was found two black salt samples only, whereas it was detected in nine white salt samples in the range of 0.1-5 ppm. On the other hand calcium in not detected in all the white and black salt samples. The preliminary AAS measurement in few selected samples showed that Hg and As beyond the WHO safe limit. This study showed that white and black salt is a good source of sodium and iron.
Corrosion Behavior of Sputter- Deposited W-Cr-(4-15)Ni Alloys in Nacl and Naoh Solutions
(Central Department of Chemistry, 2008) Kharel, Pom Lal
The synergistic effect of chromium addition in the sputter-deposited amorphous or nanocrystalline W-Cr-(4-15)Ni alloys is studied in 0.5 M NaCl and alkaline NaOH solutions at 25oC, open to air using immersion tests and electrochemical measurements. In 0.5 M NaCl solution, the addition of chromium to W-Cr-(4-15)Ni alloys containing 42-75 at % chromium increases the corrosion resistance and makes the open circuit potential more noble so as to show higher corrosion resistance than those of alloy-constituting elements (that is, tungsten, chromium and nickel). The corrosion rates of all the examined W-Cr-(4-15)Ni alloys are almost same (that is, about 2-3 x 10-3 mm/y) and are about one order of magnitude lower than that of tungsten and even lower than that of chromium metal after prolonged immersion in 0.5 M NaCl solution. In 1 M NaOH solution, the corrosion rates of the W-Cr-(4-15)Ni alloys (about 2-5 x 10-3 mm/y) are about two orders of magnitude lower than that of tungsten and nearly one order of magnitude lower than that of chromium metal. The open circuit potential of the W-Cr-(4-15)Ni alloys is generally increased with increasing chromium content in different concentrations of NaOH solutions. The open circuit potentials of all the examined W-Cr-(4-15)Ni alloys are in more noble direction in 0.5 M NaCl solution than that in 1 M NaOH solution. The passivity of the W-Cr-(4-15)Ni alloys is increased with decreasing the concentration of NaOH solutions at 25oC.
Corrosion behavior of sputter-deposited W-Mo alloys in NaOH solutions
(Department of Chemistry, 2010) Khadka, Arun
The corrosion behavior of the sputter-deposited nanocrystalline WMo alloys is studied after immersion for 24-29 h in different concentrations of NaOH solutions at 25 o C, open to air by using corrosion tests and open circuit potential measurements. Molybdenum metal acts synergistically with tungsten in enhancing the corrosion resistance of the sputter-deposited W-Mo alloys so as to show the lower corrosion rates than those of alloyconstituting elements (that is, tungsten and molybdenum) after immersion for 24-29 h in NaOH solutions. In general, the open circuit potentials of all the examined W-Mo alloys are shifted to the more positive (noble) direction with increasing the molybdenum content in the alloys. The stability of the spontaneous passive films of the binary W-Mo alloys is decreased with increasing the concentrations of NaOH solutions. However, the corrosion rates of all the examined W-Mo alloys are almost independent of concentrations of NaOH solutions (that is, 0.01 M, 0.1 M and 1 M NaOH).
Development of Green Corrosion Inhibitor from Natural Products of Nepal
(Department of Chemistry, 2020) Karki, Nabin
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Development of Low Cost Passive Sampling Diffusion Tubes for Spatial Monitoring of NO 2, SO 2 and 0 2 In Kathmandu Valley
(Faculty of Chemistry, 2012) Byanju, Rejina Maskey
The work embodied in this research was to find out the solution for the difficulties often encountered by the resource limited countries in using high cost automatic instruments for air pollution monitoring and assessment. Monitoring and assessment is an important aspect in the protection of the public from the air -pollution –induced- health- hazard by improving exposure assessment and formulating mitigations. The overall goal of this study was to develop low cost passive samplers logistically feasible and technically suitable to use for ambient NO 2 , SO 2 and O 3 monitoring in Kathmandu. Locally available polyethylene tubes were developed as diffusion tubes for ambient passive sampling. These tools were then applied to assess the spatial variability in NO 2 , SO 2 and O 3 across the Kathmandu valley The passive measurements include development of these tubes into diffusive tubes using triethanolamine (TEA) for NO 2 , SO 2 and nitrite- coated filter (GF/A filter paper) for O absorbent bases. After extraction with water, modified Griese-Saltzmann method and West- Gaeke method were used for analysis of nitrite and sulphate adduct formed due to reaction of NO 2 and SO 2 respectively . Azide modified sodium salicylate method was used for analysis of nitrate formed by the oxidation of nitrite by ozone from the air using uv visible spectrophotometer. The results were compared with ferm- badge type passive samplers from IVL-Sweden and other active methods. The detection limits of the passive sampling methods were found to be suitable for use in tested environment. The instrumental detection limits obtained from calibration curve were 0.09 µg/ml and 0.05μg/ml for NO in the range of 1.75 to 2.73 μg/m tested exposure periods. 2 – and SO 3 4 2, respectively. The detection limits of NO ; and that for SO 2 were 1.12 to 5.85μg/m Precision of the method as expressed as coefficient of variation was good enough for the monitoring of NO 2 SO 2 and O 3 viii 3 . 2 3 as were for different in ambient air of Kathmandu. The method showed strong correlation with high volume sampler and no significant difference with ferm badge –IVL samplers at p=0.05. Precision of the passive sampling method for measurement expressed as coefficient of variation (CV) was 13.3% with an overall range of 2.3-20.8% for NO 2 and it was 14.5% with an overall range of 3.4-20.2%. The results of all the exposure analysis provided a reliable ambient O 3 sampling with good precision. Precision of O 3 measurements were found to be in the range of 0.1 to 14%. The prepared diffusion tubes were suitable for 24 hour sampling in the tested environments. The tested method overestimates of 22.77% and 7.9% in compare to that of automated ozone analyzer and Ferm-IVL sampler respectively. The result was acceptable according to US National Institute of Safety and Health (Seethapathy et al., 2007) The limit of detection for developed passive sampling method was 0.011 µg/ m suitable to measure O 3 in the study area . The passive monitoring and the assessment of the quality of air prevailing in the urban Kathmandu revealed that all the three pollutants monitored NO in winter dry season were higher than in rainy season. NO 2 2 , SO and SO 2 and O 2 ix 3 3 , which was concentrations were below National Ambient Air Quality Standard (NAAQS) for both the monitoring period however, NO several points exceeded the NAAQS. Higher concentrations of NO high traffic density areas. Transportation was the major source of NO 2 were observed at the 2 pollution in the city other hand was related with the industrial emission especially due to the brick kilns and hotels. The O average of 47 µg /m 3 3 concentrations varied between 25 and 100 µg /m in the city. SO . The maximum was observed from rural site Matsygaun while minimum observed from Baudha. The pre-monsoon months specially March –May was the most vulnerable period for high concentration ozone exposure in Kathmandu valley. Key words: Diffusive, Passive sampler, Nitrogen dioxide, Sulphur dioxide, Ozone.
Effect of Cerium Ions on the Corrosion of Galvanised Steel in 0.5 M Na 2 SO 3 Solution
(Department of Chemistry, 2012) Neupane, Dharmendra
Chromate conversion coatings have been widely used in industry for a long time to improve the corrosion resistance galvanized steels. Hexavalent chromium, however, has high toxicity and carcinogenesis. Therefore, alternative and more environmentally friendly surface treatments need to be developed. Rare earth metal ions, such as cerium, is recognized as an effective corrosion inhibitor and environmentally friendly. In present study effects of Ce (III) and Ce (IV) ions on the corrosion behaviour of galvanised steel have been studied in 0.5 M Na 2 SO 3 solution. A composite coating of cerium and zinc has been prepared by pulse deposition technique and its effect on the inhibition of corrosion of galvanized steel has been evaluated in terms of E iv corr , Icorr and Tafel constants. It was found that the composite coating decreased the corrosion rate by more than 50 times. On the other hand, Ce (IV) ion was found to increase the corrosion rate due to taking part in cathodic reaction.
The Effect of Tributaries on Water Quality Parameters of Bagmati River
(Department of Chemestry, 2021) Rawal, Narendra Bahadur
Unplanned urbanization of Kathmandu city is creating many environmental issues, where worsening of Bagmati river water is one of the serious problems. The water quality of Bagmati river was characterized by collecting the real-time fine-scale data along the Bagmati river in the Kathmandu valley, using multi parameter sensor in winter season. The different physiochemical parameters viz., temperature, pH, conductivity, ORP, DO, salinity, TDS, and turbidity were monitored at 14 different locations from Gokarna to Balkhu. The spatial variation of water quality parameters revealed that the Bagmati river was comparatively less polluted between Gokarna to Tilganga and molecular oxygen present in the water was enough to decompose the organic pollutant. However, the water quality at downstream from Tinkune to Balkhu was degraded drastically making unfit for living organism. Temporal variation of water quality attributed that human activity significantly enhanced pollutants which severely degraded the water quality in the day time. The comparative study of water quality of Bagmati river and its tributaries showed that the chemical composition of the rivers were different from each other. Most of the parameters of all river water exceeded the WHO limit, ORP was positive for Bagmati river water but that was negative for other tributaries, which attributed that the tributaries of Bagmati river was highly polluted. The physiochemical parameters measured at upstream, downstream and at tributaries before mixing into the Bagmati river showed that tributaries and local pollutants from the human activities excessively loaded contaminants into the Bagmati river. The Water Quality Index (WQI) was varied between 25 to 50 for Bagmati river and its tributaries, which suggested that water quality of all rivers in the Kathmandu was bad. Keywords: Dissolved oxygen, oxidation reduction potential, pH, spatial variation, water pollution.
Electrophoretic Deposition of Oxidized Multi-Walled Carbon Nanotubes on Stainless Steel for Ethanol Sensor
(Department of Chemistry, 2023) Chaudhary, Mangal
This dissertation research describe the feasibility study and investigation of electrophoretic deposition of oxidized MWCNTs for the application in ethanol sensor. Ethanol sensors are attracting tremendous interest because of their wide spread application in industry, environmental monitoring, space exploration, biomedicine and pharmaceuticals. Ethanol sensors with high sensitivity and selectivity are required for leakage detection of explosive gases such as hydrogen and for real time detection of toxic and pathogenic gases in industries. There is also a storage demand for the ability to monitor and control our ordinary environment, especially with the increasing concern of the global warming. MWCNTs are used to obtain thin film by electrophoretic deposition. Before deposition, MWCNTs were purified and surface functionalized by concentrate nitric acid (HNO 3 ) under heating. The oxidized MWCNTs were characterized by FTIR. FTIR shows the presence of oxygenated functionalized groups as carboxylic acid and hydroxyl group on the surface of MWCNTs. The uniform electrophoretic deposition of MWCNTs are confirmed by SEM. Raman spectroscopy confirmed the deposited material was nothing other than MWCNTs. The EPD experiments were carried out by using oxidized MWCNTs on stainless steel plate at 10V at a constant time for 10 min and electrode were fixed at a distance of 1.5 cm. modification of carbon nanotubes with functional groups will greatly enhance the selectivity of the carbon nanotubes-based sensors. CNTs-based sensors have proved to work well at normal room temperature, which reduces power consumption of the device and enables the safer detection of flammable gases and alcohol. The resistance of electrophoretic deposition material was measured in closed glass chamber with digital multi-meter. Then sensitivity percentage was calculated. It was observed that the rate of % sensitivity increases with time and became saturated after certain time.
Electrophoretic Deposition of Oxidized Multi-Walled Carbon Nanotubes on Stainless Steel for LPG Sensor
(Department of Chemistry, 2023) Chaudhary, Rima
This dissertation research describes the feasibility study and investigation of Electrophoretic Deposition of oxidized MWCNTs on stainless steel for LPG sensor. Gas sensors are attracting tremendous interest because of their wide spread application in industry, environmental monitoring, space exploration, biomedicine and pharmaceuticals. Gas sensors with high sensitivity and selectivity are required for leakage detection of explosive gases such as hydrogen, and for real time detection of toxic and pathogenic gases in industries. There is also a strong demand for the ability to monitor and control our ambient environment, especially with the increasing concern of global warming. MWCNTs are used to obtain thin film by Electrophoretic Deposition. Before deposition MWCNTs were purified and surface functionalized by conc. HNO 3 . The oxidized MWCNTs were characterized by FTIR. FTIR shows the presence of oxygenated functionalized groups as carboxylic acid and hydroxyl group on the surface of MWCNTs. The uniform Electrophoretic deposition of MWCNTs are confirmed by SEM. Raman spectroscopy confirmed the deposited material was MWCNTs. The EPD experiments were carried out by using oxidized MWCNTs on stainless steel plate at 10V at a constant time of 10 min. and fix electrode distance of 1.5 cm. Modification of carbon nanotubes with functional groups will greatly enhance the selectivity of the carbon nanotubes-based gas sensors have proved to work well at room temperature, which reduces power consumption of the device and enables the safer detection of flammable gases. The resistance of Electrophoretic deposited material was measured in closed glass chamber with digital multimeter. Then % sensitivity was calculated. It was observed that the rate of sensitivity increases with time and become constant after certain time.
Functionalization of Biopolymers for the Treatment of Heavy Metals from Aqueous Medium
(Department of Chemistry, 2014) Kour (Karki), Jagjit
The industrial discharge of heavy metals into waters' course is one of the major pollution problems affecting water quality and human health. Therefore, they must be removed prior to their discharge into waste streams. For this novel cause several types of treatment methods are in use. Among them use of biowaste is emerging as the best method. Therefore different types of agricultural by-products have been explored for their efficiency in removing heavy metal ions from aqueous solution. In this regard a biomass of Desmostachya bipinnata (DB) was investigated as the potential bio-adsorbent for the removal of Cd(II), Pb(II), Cu(II) and Zn(II) from wastewater. DB is a sacrificial herb in the south Asian region particular to Hindu religion with medicinal value. It is found to be very effective in the phyto-accumulation of heavy metals from soil as well as from polluted water. This is the first adsorption studies ever performed with DB as the novel bio-sorbent in the removal of heavy metal ions. Nitrogen functional groups were grafted onto the polymeric backbone of DB with hydrazine monohydrate, dimethylamine and ethylenediamine respectively, for the better adsorption. The characterization of biopolymer was done using SEM, DRFTIR, elemental analysis, zeta potential, XRD and TG/DTA. The characterization results of biopolymer revealed to indicate proper functionalization with nitrogen groups. The effect of pH, initial concentration and contact time of the metal solution were monitored by batch method. The maximum adsorption capacities determined for Cd(II), Pb(II) Cu(II) and Zn(II) were 76.8 mg/g, 130.4 mg/g, 72.1 mg/g and 58.16 mg/g, respectively, at their optimum pH. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models. Langmuir isotherm model fitted well and the rate of adsorption followed the pseudo second order kinetic. The experiments on regeneration and reuse of biopolymers were conducted with batch method. The results indicated that more than 90% of heavy vii metals were regenerated and the biopolymers were used for six successive cycles with 90% efficiency. Thus, the adsorbents derived from DB can be used as an effective, efficient, low cost and environment friendly material for the removal of Cd(II), Pb(II), Cu(II) and Zn(II) from the aqueous medium. Keywords: Desmostachya bipinnata, Biosorption, Heavy metals, Batch experiment, Pseudo- second order kinetic model, Functionalization, Low cost, Pollution, Biosorbent.

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