Coal from North Eastern Coal Fields of Tinsukia District of Assam was
used in tests for bacterial desulphurisation with and without chemical
treatment. The coal with 5.5 wt% of total sulphur was treated with aq
ueous NH4OH and Na2CO3. The pretreated coal was used for bacterial lea
ching with a mixed culture of Thiobacillus. Under various conditions o
f bioleaching, desulphurisation was better for the pretreated coal sam
ples (namely 35-38 wt%) than for the raw coal (namely 5-27 wt%). Howev
er, the major component (organic sulphur) of the total sulphur could n
ot be removed. The kinetics indicate the desulphurisation rate for pre
treated coal to be higher than that for the untreated coal. (C) 1998 E
lsevier Science Ltd. All rights reserved.