Effect of Salinity on the Oxidative Activity of Acidophilic Bacteria during Bioleaching of a Complex Zn/Pb Sulphide Ore

H. Deveci

Karadeniz Teknik Universitesi, Maden Muh. Bolumu, 61080 Trabzon, Turkey

Received 3 April 2002; accepted 10 July 2002


The presence of some anions and cations at certain levels in the bioleaching environment may exert an inhibitory effect on the growth and hence leaching activity of a bacterial culture. In this respect, the quality of process water available with particular reference to salinity can be of prime importance for the application or development of a bioleaching process for a particular feed at an operation site.
The current study investigates the extent to which salinity up to 8% Cl- (~80 g/l) affects the bioleaching activity of mesophilic, moderately and extremely thermophilic strains of bacteria during the bioleaching of a complex Zn/Pb sulphide ore. The results indicated that salinity can adversely influence the “optimum” bioleaching activity of mesophiles and moderate thermophiles; the extent being dependent upon the strain (and type) of bacteria and the concentration of chloride. The mesophilic WJM strain was found to oxidise the complex ore at concentrations of up to 0.8% Cl- (~8 g/l) without any significant effect on the extraction of zinc while the limited extraction of zinc by DSM 583 strain occurred at 0.2% Cl-. It was noted that mesophiles can be adapted to tolerate 0.8-1% Cl- (~8-10 g/l) in solution. The bioleaching ability of the strains of moderate themophiles was adversely influenced even at 0.2% Cl- (~2 g/l). On the other hand, the extreme thermophiles were shown to perform well under saline conditions up to 5% Cl- (~50 g/l). This probably indicates the halophilic peculiarity of the extreme thermophiles compared with the mesophiles and the moderate thermophiles.

Keywords: Acidophilic bacteria; Bioleaching; Chloride

* Corresponding author
   E-mail : hdeveci@ktu.edu.tr