Browsing by Author "Balasooriya, N.W.B."
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Item Antibacterial Activity of Silver Deposited Vein Graphite Against Waterborne Pathogenic Escherichia coli Synthesized by Chemical Reduction Method(Uva Wellassa University of Sri Lanka, 2019) Kumari, T.D.D.; Swarnamali, V.M.R.; Amaraweera, T.H.N.G.; Premathilake, M.M.S.N.; Wijayasinghe, H.W.M.A.C.; Balasooriya, N.W.B.Graphite is one of the common materials using for the fabrication of composite materials. Graphite oxide, graphene oxide and many other materials are used as effective antibacterial substances, but most of them are expensive and need highly toxic chemicals for the synthesis. Nowadays, silver is considered as a most effective antibacterial material. Therefore, this study was focused on synthesizing cost effective less hazardous antibacterial material using silver and graphite. Graphite sample was purified by acid leaching, followed by modifying the surface with Conc. HNO3. The silver graphite composite material was synthesized using AgNO3 as precursor and tri-sodium citrate as reducing agent. X-ray diffractometry and Scanning electron microscopy investigations of the synthesized silver graphite composite revealed that the pure crystalline nano silver particles were deposited on the graphite surface. Antibacterial efficacy of the synthesized material was investigated using waterborne pathogenic Escherichia coli. The antibacterial test was carried out against E. coli using prepared composite samples according to the shake flask test. A commercial antibiotic (Ofloxin-200 mg) was used as the positive control. The samples were drawn at times 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5 and 6 hours by counting the number of surviving bacterial colonies on Eosin Methylene Blue (EMB) Agar, using plate count method according to standard procedures. After 24 hours, the results showed that surviving bacterial colonies contained in counted petri plates of all the synthesized composites with different Ag: Graphite ratios were reduced, with the time in an efficiency of over 98%. Therefore, this study suggests that Ag-vein graphite composite synthesized via chemical reduction method can be effectively used as an antibacterial agent against E. coli.Item Purification of Surface Graphite from Passyala, Sri Lanka(Uva Wellassa University of Sri Lanka, 2015) Somarathna, R.M.U.M.; Balasooriya, N.W.B.Flake graphite occurs as isolated, flat plate-like particles disseminated in lenses or pockets in metamorphic rocks. Less frequently it occurs in massive accumulations in veins. This is the geologically most common variety of natural graphite. Surface graphite (flake graphite) deposits occur at South Western region of Sri Lanka. There were large number of shallow pits in Sri Lanka had historically been sunk in to the weathered rock or top soil and believed more than 2500 graphite pits and mines were located in the west and central highlands. Graphite exploration from Matugama, Warakapola, Passyala and Deniyaya are in progress as new sites. Even though there are various studies on Sri Lankan vein graphite, limited attention was drawn to study the distribution, chemistry, origin and geology setting of surface graphite deposits in Sri Lanka. (Wijayananda N.P.,1987).Froth Flotation is versatile mineral processing technique, that utilizes the difference in surface properties of the valuable minerals and the unwanted gangue minerals to achieve specific separations from complex ores. Graphite have non-polar surface that do not readily attach to the water dipoles. Therefore in the separation graphite can be effectively collected into the froth. (Wills B.A.,2006). considering the chemical purification, recent studies on flake graphite with alkali roasting proven that the purity can be upgraded over 95%. ( Lu, X.J., et al,2002 ) Present research was aimed to study the purification of Sri Lankan flake graphite by using both chemical and physical purification techniques. Materials and methodology Initially collected samples were crushed into chips and prepared powder samples (<250 µm) for both sample no-01(taken from Wawehena mine) and 02 (taken for Kaluaggala mine). 200g from each samples were taken into froth flotation. Separated froth was washed to remove the effect of phenol and dried at 60 C for 24 hours. 3g from each graphite sample was take into alkali roasting, mixed with 10,20,30,40,50,60 vol. % NaOH (solid: liquid, 1:2) separately and roasted at 250 C under air for one hour. The roasted sample was acid-leached in 10 vol. % H2SO4 and filtered. The residue was washed to neutral and vacuum dried at 100 C for 15 hours . (Lu, X.J., et al,2002).Carbon percentage of graphite was determined according to ASTM - 561 and weighing the residues. Both initial and froth floated graphite matrix was characterized by Fourier Transform infrared (FTIR) spectrophotometer in 500 - 4000 cm-1 region (Nicolet 6700). The electrical characterization was performed on the dense graphite pellets by four probe d.c. conductivity in air. Results and discussion Table - 4.1 shows the measured carbon content for both sample 01 and 02, before and after froth flotation. Forth flotation was able to achieve averagely 35% purity enhancement for the collected flake graphite samples. Therefore it clearly evident that the forth flotation technique is much effective as an initial purification technique before moving to the chemical or any other purification method.Item Structural and Geochemical Characteristics of Limonite ore in Dela Sri Lanka(Uva Wellassa University of Sri Lanka, 2013) Weerakoon, W.A.P.; Balasooriya, N.W.B.; Jayawardana, D.T.Limonite (FeO.OH (H2O)) is hydrated, amorphous, and non-crystalline form of iron oxide. Limonite contains around 52.86% of iron. In Sri Lanka hydrated iron oxide is present as boulders, hill capping and near-surface deposits, classified as supergene deposits, around Dela- Noragolla (Jayawardena, 1984). The objective of this research is to identify the chemical compositions, weathering grade, weathering pattern, decomposition, and provenance of Dela Limonite. There are only a limited number of detailed geochemical and mineralogical studies carried out up to date. Therefore, present research focuses on filling the gap in knowledge by identifying geochemistry with mineralogical characteristics of the limonite deposit. Each sample was homogeneously crushed. Fresh crushed samples were powdered using mortar and pestle and sieved into < 63 µm size. wave number. The most representative limonite sample (SLDL 01) was analyzed at 25 °C room temperature, obtained with 2Th/Th radiation, operating at 40 kV, 30 mA and diffraction data were compared with references. XRF analysis was carried out using Brucker hand held XRF S1 TITAN instrument for forty (40) selected major and trace elements by having 0.4008 average errors. Results and Discussions , 1100 cm , and 800 cm wave numbers showing water group, P-H bond, organic sulfate, P=O and silicate iron (Coates, 2000; Stringfellow et al, 1993). In XRD analysis minerals were verified as limonite, goethite, quartz and hematite present in the deposit. Measured XRF data are summarized in Figure 2. By comparing with UCC value, it was clearly identified that the Fe2O3, P2O5, and MnO are enriched in this deposit (Figure 3). MgO, TiO2, Cl, Co, and Ce slightly deviate from the UCC value. Al2O3, SiO2, K2O, CaO, S, V, Cr, Cu, Zn, Rb, Sr, Y, Sn have fewer amounts compared to the UCC value. Less amounts of Al2O3, SiO2, K2O, and CaO represent that insignificant amount of feldspar. Low percentage of silica in the deposit revealed that the rock formation was in mafic environments. Having very fewer amount of S and Chalcophile elements trace elements represent that there is no sulphide mineral is a source to form this deposit. Geochemically Ce, and Y are the traces, which were representing formation of apatite as a heavy mineral. By enrichment of P2O5, and fewer amount of Ca, Cl, OH, Ce and Y indicated that the apatite was present as a gangue mineral in this deposit. Item Structural Characteristics of Natural Graphite and Synthetic Graphite(Uva Wellassa University of Sri Lanka, 2012) Wevitavidana, W.V.R.T.; Amaraweera, T.H.N.G.; Balasooriya, N.W.B.Sri Lanka is famous for highly crystalline natural vein graphite. Bogala and Kahatagaha Kolongaha are main graphite mines which are situated in the central highlands. Sri Lankan natural graphite is found in various morphologies with different structural and physical characteristics such as flake, plate and fibrous graphite. Sri Lanka graphite has high purity carbon. At present graphite industry in Sri Lanka is mainly limited for pencil productions. But in other countries which are producing graphite with high quality, motivate to conduct worthy industries. China, Mexico, Canada, Brazil and Madagascar are other countries which produce graphite for world market. Sri Lanka was top of the leading supplier of natural graphite to the world market and fulfilled the 20%-35% of the total world production. High labor cost, expensive deep mining methods and high mining cost are main problems to decay production of graphite. Therefore currently Sri Lankan graphite is unable to conflict in world market. As well as the lack of modern skills are main detriments for graphite industry. Currently synthetic graphite is used instead of natural graphite to produce different kinds of products. The synthetic graphite is known as artificial, manufactured or electro graphite. A carbon product (100% pure carbon) has been subject to a further stage of heat treatment at a temperature about 2400°C. In the main, synthetic graphite is used for electrodes in lithium ion batteries, coatings, conductive fillers, rubber and plastic compounds, foundry etc. However, in Sri Lanka, there are limited work has been done to study structural characteristics of graphite. Therefore, Sri Lankan natural graphite is unable to use for some industries like electrochemical application industries. Most of graphite used for applications as powder form. As a result, rhombohedra content is increasing gradually. Certain applications need rhombohedra phases rather than hexagonal phase.