The sulphur content in coal
and petroleum coke varies from traces to 10% or more by weight. This exists in
two
forms, inorganic and organic.
Sulfur in coal and rocks associated with coal mines like petroleum wastes can
occur as
organic sulfur, sulfate sulfur
and pyritic sulfur. On combustion of coal/coke, sulphur gets released into the
atmosphere
and contributes to the air
pollution in the form of ‘acid rain’. Organic sulphur occurs as an integral
part of the
molecular coal and the
petroleum waste matrix and is not readily accessible for microbial attack. So,
the removal of
organic sulphur from
coal/coke/petcoke while retaining its fuel value is most difficult. Chemical
processes need a
very lengthy and tedious
process involving elevated temperature and pressure, which is not feasible on a
technical
scale. On the other hand,
biological processes occur under very mild reaction conditions. Hence, the
desulphurization
of petroleum waste by
microbial technique can be achieved in an economical and simpler way. In the
present paper,
a biological process using Thiobacillus thiooxidans has been described for the
removal of total sulphur from Navanagar
petcoke sample. The results
have shown that the mean total sulphur content in the metcoke sample was 6.32%.
After
first bacterial leaching with T. thiooxidans 13.5% sulphur was removed by
the bacteria and the remaining sulphur
content in the metcoke was
5.46%. The second leaching of the previously leached petcoke sample, using T. thiooxidans
resulted into sulphur removal upto 93%.

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