Bioleaching of Zinc Sulfide Concentrate in Redox-Controlled Fed-Batch Process Compared to Redox Non-controlled Batch Process

The study aims to evaluate bioleaching of zinc sulfide concentrate in controlled redox potential fed-batch mode to avoid passivation occurring in redox non-controlled bioleaching. The microorganisms used in the bioleaching study were a mixed culture of iron-oxidizing microorganisms dominated with Leptospirillum ferriphilum. The motivation for the study was to cut down the cost involved in oxygen consumption due to suppression of sulfur oxidation and activating iron oxidation activity. This innovative approach was possible by carrying out bioleaching on a fed-batch mode with redox potential-controlled bioleaching. The redox-controlled bioleaching was carried out by 100% (v/v) inoculum with high redox potential 650 mV in the reaction vessel with controlled addition of zinc sulfide concentrate maintaining the redox between 550 and 650 mV. The solid percentage of 1% (v/v) of feed material (ZnS concentrate) in the redox-controlled experiment was considered for a batch mode of redox non-controlled experiment for a potential comparative assessment of fed-batch and batch modes. The fed-batch experiment succeeded in restricting the sulfur passivation layer. The time taken by the fed-batch experiment was two times shorter than the batch experiment. The recovery percentage of Zn in redox-controlled batch mode experiment was 51.6%, while in redox-controlled fed-batch mode experiment was 69.4%, which resulted in 34.55% higher recovery in redox-controlled fed-batch bioleaching of ZnS concentrate. The fed-batch bioleaching using iron-oxidizing microorganisms with controlled redox potential restricted sulfur oxidation and was advantageous over the batch process. [GRAPHICS] .

Automated summary

The study evaluates the bioleaching of zinc sulfide concentrate in controlled redox potential fed-batch mode to prevent passivation and increase recovery rate. The use of a mixed culture of iron-oxidizing microorganisms dominated with Leptospirillum ferriphilum and the controlled addition of zinc sulfide concentrate with high redox potential resulted in a higher recovery rate compared to the traditional batch mode. This innovative approach reduces cost and improves efficiency in bioleaching.