Browsing by Author "Jayarathna, S.P.B.L."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Biocoagulation and Its Potential Application for Graphite Bioprocessing
    (Uva Wellassa University of Sri Lanka, 2013) Jayarathna, S.P.B.L.; Peries, C.M.; Henegamage, A.P.
    Sri Lanka is famous for Graphite industry since ancient times around the world. There are three major Graphite mines which are located in Kahatagaha, Bogala and Ragedara. Vein type graphite deposits in Sri Lanka are considered as a unique occurrence of graphite because of its high purity, extensive mineralization and restricted occurrence. Graphite with 95-99% of carbon and gangue minerals such as pyrite, chalcopyrite, calcite, biotite and feldspars are found in each structural type depending on the mode of occurrences and nature of graphite vein (Amarweeraet al., 2013). Hence, removal of impurities from the graphite can increase the economic value of graphite. Flotation cell is common in Graphite industry to upgrade its carbon grade by removing impurities and it can be used to upgrade over 80 % Graphite in Sri Lanka However, efficiency of the flotation cell separation is not effective for Graphite with small particle sizes (Karr et al., 1990). Biocoagulation is the promising method, practiced in all over the world for sorting of small sized mineral particles with the use of microorganisms (Kuyumcuet al., 2009). Therefore, this study is focused to increase the carbon recovery in Graphite through the separation of fine particles using the biocoagulation with microorganisms. Methodology Three different particle sizes (40µm, 53µm and 72µm) of graphite samples were obtained from Bogala and Kahatagaha mines. Isolation of fungi was carried out from the obtained samples using dilution plate techniques with Potato Dextrose Agar (PDA) medium. Pure cultures of the isolated fungi were obtained using single spore isolation technique with the same medium. Isolated pure fungi cultures were inoculated in to 20 ml of Potato Dextrose Broth (PDB) and incubated for 48 hours at 30 C. Then the pH values of the each fungi broth cultures were measured separately. Two grams of each different graphite samples with different particle sizes were mixed with the incubated PDB and kept with continuous mixing for the coagulation. After four days of incubation, the number of coagulates in each broth cultures was counted using the light microscope and the fungal broth culture (F3) which was given the highest coagulates number was selected for the further processing. In order to determine the carbon grade of the sample, coagulates of the selected broth culture were carefully separated out from the broth medium and washed with distilled water for three times. Then the particles with the coagulates were kept in a muffle furnace at 500 C for two hours in order to remove microbial biomass from graphite particles followed by keeping the samples again in muffle furnace at 960 C for further digestion. Initial and the final weights of the sample were measured to calculate the percentage of carbon recovery. Three replicates were maintained for each treatment and data were analyzed using ANOVA with the confidence level of 95% using MINITAB statistical software.
  • No Thumbnail Available
    Item
    Biocoagulation and its Potential Applications for Graphite Bioprocessing
    (Uva Wellassa University of Sri Lanka, 2013) Jayarathna, S.P.B.L.
    The technical relevant sorting processes like density, magnetic or electrical separation and flotation, require a narrow particle-size range for a sufficient selectivity in order to eliminate overlapping effects. Since the rapid decrease of the mass forces and increase of the surface energetic state with decreasing particle size the well-known sorting processes are not applicable to an effective separation of particle sizes smaller than 10 mm. Flotation cell is common in Graphite industry to upgrade its carbon grade and it used to upgrade over 80 % Graphite in Sri Lanka. Pyrite is a major impurity in Sri Lankan Graphite and it remove as lumps with graphite. Three fungi were isolated from Bogola graphite mine and Saccharomyces cerevisiae was used to biocoagulation process. Isolated fungi were named as Fl, F2 and F3. Ash content was analyzed to determine the carbon grade of graphite. Furthermore, biocoagulation was tested to 40 pm, 56 p,m and 72 pm particle sizes. All three fungi Fl, F2 and F3 were given over 99% carbon recovery grades. Among them, highest carbon recovery grade obtained from F1 fungus. The efficiency of biocoagulation decrease with the increment of particle size and maximum coagulation was observed in 40 pm. Key Words: Graphite, Biocoagulation, Fungi