Browsing by Author "Amaraweera, T.H.N.G."

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    Antibacterial Activity of Silver Deposited Vein Graphite against Waterborne Pathogenic Escherichia coil
    (Uva Wellassa University of Sri Lanka, 2018) Kumar, K.K.A.D.; Amaraweera, T.H.N.G.; Premetilake, M.M.S.N.; Wijayasinghe, H.W.M.A.C.
    The microbial contamination of drinking water is a major health problem in the world which requires an effective treatment. Silver ion (Ag+2) is used as nonspecific antibacterial factor and it acts against a very broad spectrum of bacterial species. In this study, antibacterial efficiency of Ag deposited vein graphite were studied using Escherichia coli strain. Ag was deposited on the graphite surface by reduction of Ag+2 in silver nitrate solution using reducing agent. Scanning electron microphotographs of the Ag deposited graphite reveal that the deposited silver particles are highly agglomerated or spongy voids. Although the size of silver particle agglomerates are relatively coarse, the average size of individual silver nanoparticle is around 75 nm. Antibacterial efficacy of the synthesized sample was investigated using waterborne pathogenic E. coli strain. The antibacterial test was done using prepared composite samples and samples of E. coli, using shake flask method. A commercial antibiotic (Ofloxin-200 mg) was used as the positive control. The samples were drawn periodically (1, 1.5, 2, 2.5 and 3 hours) from the flask and tested against E. coli by plate count method using standard procedures. There was a significant E. coli removal efficiency by the synthesized Ag Graphite composite compared to purified graphite and positive control (One-way ANOVA, p-value=0.00). Therefore, this study suggests that Ag- vein graphite composite could be used as an effective material in water purification, especially in removing of E. coli.
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    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.
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    Determination of the Adsorption of Solids and Some Selected Elements into Different Types of Clay Minerals for Hospital Wastewater
    (Uva Wellassa University of Sri Lanka, 2019-02) Kattange, K.G.R.D.H.; Amaraweera, T.H.N.G.; Sansfica M. Young; Yapa, Y.M.S.S.
    The hospital wastewater is a greater concern because of the hazardous and toxic nature and its direct discharge will contaminate water bodies. The main objective of this study was to remove total suspended solids and some selected elements from hospital wastewater since the previous studies show that Total Suspended Solids (TSS) of the hospital wastewater is high and the existing treatment plants are not efficient enough to remove them to meet environmental standards. This study showed that the TSS was 1534 mg l-1 and Total Dissolved Solids was 580 mg l-1. Adsorption series were prepared by adding equal weight of five different clay samples which mainly contain Montmorillonite, Kaolinite and Illite clay compositions to an equal volume (100 ml) of hospital wastewater. The clay samples were then analyzed using X Ray Diffraction pattern and for the filtrate Fourier Transform Infrared Spectroscopy was done to determine the absorption after 2, 4, and 6 weeks by filtering out 100 ml of the sample from each clay type. Total Suspended Solids were measured for the untreated sample and for the samples treated with each clay by filtering using a 45µm filter paper and taking the dry weight. Removal percentages for the sample using Illite clay for TSS and Total Dissolved Solids were 96.02% and 43.27% respectively which were reached within two weeks. As for the results the optimum clay to absorb and reduce the TSS and Total Dissolved Solids in hospital wastewater is Illite which was reached within two weeks.
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    Garnet rich mineral sand based filter media for Removal of fresh water algae
    (Uva Wellassa University of Sri Lanka, 2018) Siriwardhana, K.A.J.W.; Amaraweera, T.H.N.G.; Premathilake, M.M.S.N.
    Algal blooms have become a stigma for present day stagnant surface water bodies. Therefore, consumption of water without treatment would be harmful. Garnet granules have the ability of reduction of bed expansion and particle abrasion in multi-media filters during back flushing due to its high specific gravity and high hardness. In this study, garnet granules separated from beach sand in southwestern costal area in Sri Lanka were investigated as a filter media to remove fresh water algae. Microscopic and particle size analysis indicated that the beach sand consists predominantly of garnet, quartz and ilmenite. The garnet grains are round to elongate shaped in the size range between 1 mm and 0.15 mm. Particle size and shape of the extracted garnet are optimum for the use as water filtering medium. Garnet enrich fraction grains (1 mm — 0.15 mm) were further concentrated by density separation via panning. Algae samples from Beira Lake, Colombo were collected, in the depth at illumination level 1% from surface. Algae were grown giving nutrient, sunlight and aeration. Nutrient medium used was the Bristol solution. For varying flow rates, algae filtered through 0.50 mm and 0.15 mm sieved fractions. Parallel determination for the efficiency of the filter bed with time was done and turbidity was measured by turbidity meter. When considering the algae filtration, removal of Microcystis is efficient for 0.15 mm panned fraction. Removal of Closterium was not efficient probably due to shape of the organism. Chroococcus and Volvox, were not removed well possibly due to their small size. Removal of algae was decreasing with the time from both filter beds. The study concludes that prepared garnet filter is useful in filtering Microcystis and further modifications should be done prior to use as a filter. Keywords: Algae, Garnet, Panning, Filtration, Mineral sand
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    General Characteristics of Wastewater and Effectiveness of Existing Treatment Methods in Hospitals with Special Reference to Uva Province
    (Uva Wellassa University of Sri Lanka, 2018) Kumara, A.M.I.U.; Young, S.M.; Amaraweera, T.H.N.G.; Yapa, Y.M.S.S.
    Hospital wastewater has gained a significant attention due to release of untreated toxic chemicals and pathogens to the environment. Although, there are some treatment facilities in hospitals, most of the wastes are partially or untreated before releasing to the environment. This study thus focuses to asses and gives suggestions to improve an existing treatment plant for better function and performance and investigate a hospital that does not have a treatment plant to give suggestions. Wastewaters from Badulla hospital (n=5) and Bibile hospital (n=4) were collected weekly over a period of three weeks (total n=27) where physical (n=5), chemical (n=12) and biological (n=1) parameters were measured. The water quality after the trickling filter in Badulla hospital shows a clear drop for Five-Day Biochemical Oxygen Demand (BOD5), Total Suspended Solids and pH. The BOD5, Chemical Oxygen Demand, Total Suspended Solids and PO43- of the waters ranged between 21-108 mg L-1, 130-290 mg L-1, 290-904 mg L-1 and 11.84-16.39 mg L-1 respectively and are much higher than Central Environmental Authority standards in Sri Lanka. There were no microbes detected after the Ultraviolet (UV) plant and perhaps due to heavy use of Chlorine in spite of the UV treatment. In Bibile hospital, all discharged water outlets are open to the environment. The BOD5, PO43- and NO3- of discharged water varies within 8-98 mg L-1, 3.77-8.16 mg L-1 and 0.8014.60 mg L-1 and are much higher than accepted standards. The treatment plant at Badulla hospital is unsatisfactory to meet the requirements of the accepted standards. Thus, the treatment process of the trickling filter needs improvements in where the rock particles have to be replaced with rock particles in a varying size order. The results indicate that a treatment plant is required for the Bibile hospital with immediate effect.
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    Li2CO3-coated Sri Lankan Vein Graphite Electrode for Rechargeable Lithium- ion Battery
    (Uva Wellassa University of Sri Lanka, 2013) Manthirathna, M.A.N.C.; Wijayasinghe, H.W.M.A.C.; Amaraweera, T.H.N.G.
    High quality vein graphite, containing 95-99% of pure carbon in Sri Lanka has been identified as promising candidate as anode material in lithium ion rechargeable battery. Purification and mild oxidation have been widely used to enhance the property of the vein graphite as anode material (Balasooriya et al., 2007; Amaraweera et al., 2013). However, alkali carbonates coating which are identified as cost effective and nontoxic approach for the surface modification have not been investigated for vein graphite in Sri Lanka (Komaba et al., 2008; Zhang et al., 2003). Therefore, present work is aimed to develop low cost anode material based on Li2CO3 coating of purified vein graphite. Methodology Purified vein graphite powder less than 53µm (<53 µm) was used for this study (Amaraweera et al., 2013). Graphite powder were added into an agate motor and milled for about 2 hours by adding aqueous Li2CO3to ensurethat the graphite was completely witted. Then the surrey was dried in vacuum at 100 C. The modification of the graphite mixture was characterized by FTIR Spectroscopy D.C conductivity of graphite powder and sheet conductivity of graphite electrode was measured by four-probe and VanderPauw, methods respectively.
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    Purification of Low Grade Quartz Bearing River Sand
    (Uva Wellassa University of Sri Lanka, 2018) Kalubowila, C.N.; Garthiga, Y.; Amaraweera, T.H.N.G.; Wijayasinghe, A.
    The demand for the high-grade quartz is increasing rapidly with the advancement of semiconductor and photovoltaic industries. Therefore, it is essential to enhance the purity of low grade quartz. Quartz bearing gravel, quartzite and, river and beach sand are the major low-grade silica sand deposits in Sri Lanka. In this study, a method was investigated to remove impurities in quartz bearing river sand depending on its mode of occurrence. Microscopic analysis implies that the impurities in the silica sand are present as mineral grains, coatings, interlocking grains and inclusions. In the physical purification process, sieving was carried out to separate river sand according to the grain size. The highest weight percentage of river sand is in the size range between 0.5 and 0.15 mm. This portion consists of more than 90% of quartz. Therefore, physical separation, depending on the grain sizes, can effectively use to remove the mineral grains present as impurities in quartz grains. Panning together with scrubbing and washing was carried out to remove the clay particles, heavy minerals and other undesirable materials present in the river sand. A chemical purification of physically separated river sand was carried out by acid leaching with 5 - 30 vol. % of HCl solutions in the temperature range between 27 and 100 °C. The mineralogical analysis and X-ray diffraction analysis imply the possibilities to remove iron oxide coating from the surface of quartz grains with low concentration of HC1, at low temperature. Accordingly, this physical separation and chemical treatment process is a more effective method to purify the low-grade river sand suitable for the advanced technological applications.
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    Purification of Vein Graphite by Alkali Roasting for Anode Material in Lithium Ion Batteries
    (Uva Wellassa University of Sri Lanka, 2013) Wewegedara, W.G.C.N.; Amaraweera, T.H.N.G.; Wijayasinghe, H.W.M.A.C.
    Unique vein graphite deposits with highly crystallized and high purity graphite are present in the mineralization zone of the central highlands of Sri Lanka This graphite has been identified as a potential candidate for the lithium ion rechargeable batteries (Balasooriyaet al., 2007). Recent attention has been made towards the purification of vein graphite in order to prevent the anode ageing and decomposition of the electrolyte in lithium ion batteries (Amaraweera et al., 2013). Alkali roasting for purification of graphite has found to be a very effective method to remove sulfide and silicate impurities at low temperatures (Lu et al., 2002). Therefore, this study focused on studying the effectiveness of alkali roasting for the purification of vein graphite in Sri Lanka Methodology Graphite powder (<53 µm) from Needle Platy Graphite (NPG) and Shiny Slippery Fibrous (SSF) morphological types from Bogala and Kahatagaha mines were used for this study. The graphite was treated in aqueous solutions containing 5, 10, 15, 20, 25, 30 and 35 vol. % NaOH (Solid: liquid, 1:2) separately and roasted at 250 C under air for one hour. Then, the roasted sample was acid leached in 10 vol. % H2SO4. After that, the solid was filtered, washed to neutral and vacuum dried at 100 C for 15 hours. Minimum concentrations of NaOH for the purity enhancement were identified for each graphite type. Roasting treatments were repeated at 150 C, 200 C, and 300 C, using the data obtained previously to identify the effect of roasting temperature on purity enhancement. Carbon percentages of the treated graphite samples and untreated graphite samples were determined by heat treating at 950 C for 3 hours in Muffle Furnace, according to ASTM – C 561 and weighing the residues. Pellets of treated and untreated graphite powder (D =12 mm and L = 5 mm) prepared by cold uniaxial pressing at 100 Mpa were used to measure D.C conductivity by four-probe method at room temperature.
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    Removal of Selected Metals in Textile Wastewater Using Plant Parts of Pinus caribaea, Manihot esculenta and Gliricidia sepium
    (Uva Wellassa University of Sri Lanka, 2019-02) Gimhani, B.S.G.; Amaraweera, T.H.N.G.; Young, S.M.
    Textile industry is one of the major contributions of every nation’s economy. Metals and their compounds are indispensable to the industrial and technological development and causes a major environmental threat when released to the environment. Therefore, developing effective economical removal methods of toxic metals from industrial wastewater is important, as a replacement for costly adsorption methods of removing metal ion from textile wastewater. This research attempts to assess and compare the efficiency of low cost adsorbent materials prepared from plant parts such as roots, trunk, pith and leaves of the Pinus caribaea, Manihot escluenta and Gliricidia sepium. The removal of metal ions was carried out using synthetic textile wastewater where the effect of contact time and particle size were investigated. Textile dye contained water was added to the plant parts for three different particle sizes (<150µm, 150-500 µm and 500 µm) and remaining concentrations were measured using Atomic Adsorption Spectrophotometer after 1,3,5 and 7-day time interval. The experiment showed that the quantity of metal ions adsorbed varied with contact time, particle size and part of the plant. The order of removal of metal ions by bio sorbent is Fe2+ > Mn2+ > Cu2+ > Cd2+ > Mg2+. Furthermore, in comparison of the three plant species Gliricidia sepium pith shows the highest removal percentage for metal ions of 73.06% and plant leaves of all three shows the lowest removal percentage of 45.14% for all the metal ions used. This confirmed that the plant parts that has high content of cellulosic materials had a unique role on high adsorption of metals. The results convince the high potential of Gliricidia sepium pith as an alternative substrate behaving as an adsorbent, for removal of toxic metal ions being an economical remediation for wastewater treatment.
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    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.
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    Substitution of Rice Husk Ash for Grout Additive to Decrease Shrinkage of Cement Grouting
    (Uva Wellassa University of Sri Lanka, 2019) Anojan, K.; Amaraweera, T.H.N.G.; Christopher, W.A.P.P.; Sarathkumara, W.
    Rice husks are the protecting covering of grains of rice. They are formed from hard materials, including opaline silica and lignin, to protect the seed during the growing season. Rice milling industry generates substantial amounts of rice husk during milling of paddy, which is mostly used as a fuel in rice milling industry. Rice Husk Ash (RHA) is about 25% by weight of rice husk when burnt in boilers. Chemicals used in grouting may be replaceable with waste material from the rice milling industry when it is processed to RHA to decrease the shrinkage while increasing the strength. This study aims to substitute RHA as a grout additive in cement grouting and identify an optimum amount of RHA. First rice husk was burnt in a muffle furnace under controlled temperature which started at room temperature and was gradually increased up to 680 ℃ for about 6 hrs before it was allowed to cool down to room temperature (25 ℃). RHA sample was sieved by using 150 µm sieve. The cement: grout additive: water mixing ratio 2000:9:840 respectively. Then RHA was added replacing varying amounts of grout additive. The grout mixture was prepared manually by hand since the samples were too small to mix using a mixing machine. The proto type samples made were passed the strength tests according to the British Standard 1881. Mixing with a mixer would decrease the variation of results. According to the compressive strength, samples which contain high rice husk ash content were having a high compressive strength. Furthermore, the strength increased after 28 days was 49 MPa. Thus, the conclusion can be drawn that substitution of RHA for grout additive is possible and positive with gained strength.
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    Synthesis of Expanded Graphite using Sri Lankan Vein Graphite via Ultrasonication
    (Uva Wellassa University of Sri Lanka, 2018) Senavirathne, M.M.K.R.N.D.; Kanagaratnam, J.N.; Amaraweera, T.H.N.G.; Wijayasinghe, A.
    Sri Lankan vein graphite, which is found in highly crystallized form with high purity (95 - 99 % carbon), have already been successfully developed for the anode of the lithium ion rechargeable battery. However, for their use in future energy storage applications, such as in sodium ion batteries, modification of the vein graphite structure is essential. Hence, this study focuses on structural modification of purified vein graphite by converting into expanded graphite via solvent assistant ultrasonication. Graphite oxide was synthesized from purified vein graphite by employing improved Hummer's method and then sonicated with propylene carbonate. The dried product was heated and again subjected to sonication with the same solvent. Then the solution was centrifuged to remove any non exfolliated graphite. Finally, the solution containing Graphite Oxide (GO) particles in PC were thermally reduced to produce reduced graphite oxide (rGO-PC). X-ray diffraction of crystal phase of the resulted graphite oxide shows the existence of a broad peak at 23.19 ° (20) corresponding to an interlayer spacing of 0.38 nm. The Fourier transform infrared spectrum obtained on the synthesized GO confirm the presence of O -H, C=O, COOH and C-0 oxygen functionalities, which are then, confirm to be partly removed by the successive thermal treatment. Scanning electron microscopic images are evidence for the expanded structure with wrinkles and folded nature in contrast to the opaque and smooth structure observed in the pristine graphite. Altogether, these results confirm the successful formation of expanded graphite by the solvent assisted ultrasonication technique.
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    Synthesis of FeCl3-Graphite Composite from Vein Graphite via Solvothermal Method for Lithium-Ion Rechargeable Battery Applications
    (Uva Wellassa University of Sri Lanka, 2019) Ranasinghe, U.G.K.L.K.S.; Kanagaratnam, J.N.; Amaraweera, T.H.N.G.; Wijayasinghe, H.W.M A.C.
    Natural vein graphite is a good crystalline material with high natural purity and is used for advanced applications. Natural vein graphite has been identified as a cost effective source to produce anode material in Lithium-ion Rechargeable Batteries (LIBs). However, the electrochemical performance of anode material prepared from vein graphite has to improve further for practical LIB applications. This study focuses on synthesizing Ferric Chloride-Graphite Intercalation Compound (FeCl3-GIC) via solvothermal method to enhance the Li-ion intercalation. Anhydrous Ferric chloride was used as an intercalant into graphite layers via solvothermal method at 400 °C for 12 hours by using 50 mL autoclave. The X-Ray Diffraction patterns show the characteristic behavior of the graphite intercalation compound. Moreover, weaker peaks corresponding to the Fe2O3 and FeCl3 could also be observed in the XRD pattern indicating the existence of secondary minor phases of Fe2O3 and FeCl3 in the GICs. Scanning Electron Microscopy images evidenced for the smooth surface morphology of graphite particles after the treatment. Half-cells were assembled using the electrode fabricated from the synthesized material and Li counter electrode in an argon-filled glovebox. It shows a high specific capacity of 378 mA h g-1, which is little higher than the theoretical capacity (372 mA h g-1 for LiC6) during its first discharge. However, there is a high capacity loss after 25 cycles. The fading nature of this assembled battery could be due to the detrimental effect of Fe2O3 and unreacted FeCl3. This could be minimized by carrying out the solvothermal treatment in a vacuum environment by eliminating the O2 present inside the autoclave chamber. By doing this, the formation of Fe2O3 could be minimized and as the chamber pressure increases, the ability of FeCl3 molecules to be intercalated into the graphite layers could be enhanced.
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    Synthesis of Graphite Oxide from Kahatagaha Vein Graphite using a Localized Improved Hummers Method
    (Uva Wellassa University of Sri Lanka, 2013) Madusanka, Y.V.; Amaraweera, T.H.N.G.; Wijayasinghe, H.W.M.A.C.
    In modern world, materials, - regardless of their make, whether natural or synthetic – play a huge role. From all these materials, Graphite is taking a wide consideration of scientists as they are naturally occurring, cheap material with very interesting physical, chemical and mechanical properties. Within the range of applications of Graphite, Graphite Oxide (GO) and Graphene are more important as they are having many applications and very good potential in Nano scale materials and Nano Technology. GO has attracted much interest recently as a possible route for the large scale production and manipulation of Graphene, a material with extraordinary electrical properties. Sri Lanka has two major natural vein graphite deposits in Kahatagaha- Kolongaha and Bogala. Of the two Kahatagaha vein graphite has the highest purity that can be upgraded up to 99.97% Carbon by HCl leaching (Amaraweera et al, 2013). No researches and experiments have been conducted on Kahatagaha vein graphite which has been upgraded up to 99.97% Carbon in nano scale. The potential for value addition to Kahatagaha graphite has not yet been adequately explored. This study aims at synthesizing GO using a localized version of the Improved Hummers Method and characterization of GO to confirm the oxidation. Methodology Graphite sample, KNPG (Kahatagaha Needle-Platy Graphite) was first crushed using a hammer to obtain +10 mm chips and then the sample was milled in a disc mill for 15 minutes. The milled sample was sieved using a sieve shaker and <53 microns portion was taken for further treatments. 675 ml of 5% HCl was added to 50 g of graphite in 1000 ml beaker and it was vigorously stirred for 1.5 hours at 60 C. The solution was vacuum filtered and washed with distilled water (500 ml) and the same procedure was repeated once. Finally purified graphite was washed until the pH become neutral. KNPG achieved purity level of 99.97% Carbon. 9: 1 mixture of conc. H2SO4 (96% 360 ml) and conc. H3PO4 (85% 40 ml) were added to a mixture of 3 g of purified KNPG and 18 g of KMnO4. The mixture was stirred for 6 hours at 50 C. Then the solution was poured on to ice (200 ml) with 30% H 2O2 3 ml and then vacuum filtered through Fisherbrand filter paper. The brown product left on the filter paper was collected and washed with water (200 ml x 3) and left in a vacuum drier at 105 C for 2 hours. The hard black solid taken out from the vacuum drier was crushed using an agate mortar and pestle to obtain finer particles of 6.86 g of GO. A pellet for electrical conductivity measurements was made using 1g of GO and FTIR Spectrum for GO was taken. A tape was casted using GO for sheet resistance measurements and XRD spectrum was obtained for characterization of GO.
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    Synthesis of Silver - Graphite Composite via Ultrasonication Associated Chemical Reduction and Study of its Antibacterial Properties
    (Uva Wellassa University of Sri Lanka, 2020) Gamlath, J.G.V.I.; Swarnamali, V.M. R.; Amaraweera, T.H.N.G.; Premathilake, M.M.S.N.; Wijayasinghe, H.W.M.A.C.; Balasooriya, N. W. B.
    Graphene oxide is widely used to produce an antibacterial silver composite, but mostly required toxic chemicals for production and they are comparatively expensive. The present study was focused on synthesizing cost-effective less hazardous antibacterial composite using vein graphite and silver. Silver graphite composites can be made using various methodologies and those methods can affect the antibacterial property. Therefore, in this study, silver graphite composite was synthesized by ultrasonication associated chemical reduction method. Sri Lankan vein graphite was purified by the patented acid leaching method, then surface modified with patented mild chemical oxidation method. The silver-graphite composite was synthesized from an AgNO3 silver precursor with a concentration of 0.00025 M, 0.001 M, 0.002 M by using tri-sodium citrate as a reducing agent. X-ray Diffractometry analysis indicated that composite only consists of silver nanoparticles and carbon in pure crystalline form. The composite was characterized by Scanning Electron Microscopy. Nano-scale silver particles were seen deposited on the surface of graphite. Antibacterial efficiency of the synthesized composites was analysed using Escherichia coli and the test was carried out using the shake flask method. For positive and negative controls, modified graphite and commercial antibiotic ofloxacin were used respectively. The samples were drawn out with a one-hour time interval from 0 to 6 hours and the number of surviving colonies on Eosin Methylene Blue agar was counted after 24 hours of incubation. The removal of the Colony Forming Unit for all samples gave efficiency over 99 %. The Kruskal-Wallis test suggests that colony removal depends on the time and concentration of AgNO3 used in the synthesized composite. Therefore, this study suggested that silver-graphite composite synthesized via ultrasonication associated chemical reduction can be used for E. coli as an effective antibacterial agent. Keywords: Graphite, Silver nanoparticles, Ultrasonication, Chemical reduction, Trisodium citrate