Biochemical Leaching of Metals from Indian Ocean Nodules

Bioleaching of valuable metals from Indian Ocean poly-metallic nodules was carried out using a pure culture of Aspergillus niger. Parameters such as pH, pulp density (PD), particle size, time were optimised for the bio-recovery of metals. At pH 4.5, 35 °C temperature and 5%
PD and in 30 days the biorecovery of the metals was found to be 97% Cu, 98% Ni, 86% Co, 91% Mn and 32% Fe whereas
in control experiment 4.9% Cu, 8.2% Ni, 27% Co, 6.3% Mn and 7.1% Fe were dissolved. The interesting aspect of this investigation is that a good amount of leached metals are
adsorbed on fungal mycelia which can be recovered by acid wash. Fall in pH rom 7 to 4.6 and rise in Eh from 140 mV to 380 mV indicated that A.niger followed indirect leach-ing mechanism by releasing some organic acids which in turn converted higher oxides to lower oxide phases as
identified by XRD phase analyses.