Biocoagulation and Its Potential Application for Graphite Bioprocessing
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
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.
Description
Keywords
Mineral Sciences, Mineral, Science and Technology, Graphite Industry, Graphite