Percolation bacterial leaching of rajpura dariba ore in 4-ton column
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The microorganism, Thiobacillus ferrooxidans, was isolated from Rajpura Dariba mine water as well as from the ore. After isolation, the same was cultured in 9 K medium. El51The microorganism was adapted to the high concentration of Zn by the usual technique. 1~6JThe adapted strain was inoculated to the Bacterial Film Oxidation (BACFOX), and the lixiviant was taken from the BACFOX. Rajpura Dariba ore mainly contains sphalerite, pyrite, and silica, and the trace elements were Cu, Cd, Ag, etc. The typical chemical analysis of the ore is shown in Table I. Crushed ore (10 to 12 m m in size) was loaded in a 4-ton capacity fiber-reinforced plastic (FRP)-lined column. The inner diameter and height of the column were 1 and 4 m, respectively. The lixiviant from the BACFOX was pumped to a distribution box located at the top of the column through a metering pump. The solution after percolation was collected at the bottom reservior (BACFOX). The lixiviant after the adjustment of pH was pumped to the column, and thus, the cycle continued. Every day, pH, Eh, Fe(II), Fe(IlI), acid content, etc., were analyzed. The pH and Eh were measured by a Digital CK 704 meter. The Fe(II), Fe(IIl) and acid content were analyzed volumetrically, as described in Reference 17. The Zn, Fe(total), and other trace elements were analyzed by a Varian AA-20 atomic absorption spectrophotometer. In order to interpret the leaching data, the results were presented as monthly averages. Prior to percolation leaching, the ore was washed with diluted H 2 S O 4 (pH - 1.0) at a flow rate of 0.04 1/kg of ore/day. During the entire acid washing, 54.5 kg of H2SO4 was consumed and 1.3 kg of Zn leached out. G. ROY CHAUDHURY, Scientist, L.B. SUKLA, Scientist, and R.P. DAS, Head, are with the Hydro & Electrometallurgy Division, Regional Research Laboratory, Bhubaneswar 751 013, India. R.S. SHARMA, Senior Manager, and S.C. BHANAWAT, Chemist, are with the Central Research & Development Laboratory, Hindustan Zinc Limited, Udaipur, Rajasthan, India. Manuscript submitted February 23, 1990. METALLURGICALTRANSACTIONSB
After removal of acid-consuming gangue minerals, the ore was percolated with acidified Fe2(SOa)3 bacterial solution. The flow rate and pH of the lixiviant were 0.04 1/kg of ore/day and approximately 2.0, respectively. During percolation, leaching various parameters, such as pH, Eh, Fe(II), Fe(III), acid consumption, Zn leaching rate, etc., were monitored. The monthly average of the Zn leaching rate is shown in Figure t. It was observed that the leaching rate was slow initially but increased progressively with time. The Zn leaching is mainly dependent on two chemical reactions, i.e., leaching by Fe(III) and direct microbial attack on sphalerite, and can be written as ZnS + Fe2(SO4)3 ~ ZnSO4 + 2FeSO4 + S
[1]
ZnS + 1/2 02 + H2SO4 ~ ZnSO4 + S + H 2 0 [2] The average Fe(II) and Fe(III) concentrations of the lixiviant in different months are shown in Table II. It was observed that the Zn leaching rate did not increase as the Fe(III) concentration increased, as sugges
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