STUDY ON SURFACE ALTERATION BEHAVIOR DURING COLUMN BIOLEACHING

Abstract

Studying dissolution of copper during bioleaching of sulfide-bearing granite rock obtained from Malanjkhand copper mines (Hindustan Copper Ltd.), India, using electron microscopy technique is the main thrust of this investigation. The micron scale examination of metal distribution under electron microprobe at different stages of leaching was studied to interpret the chemical phenomena involved in the transformation process. Bioleaching studies were carried out in vertical columns using acidophilic microorganisms operated at ambient temperature. It was observed that leaching efficiency increased with decrease of particle size and lixiviate flow rate. The electron probe documented the morphological evolution of the granite sample before, after, and during column bioleaching. The feed sample constitutes plagioclase feldspar, orthoclase feldspar, and quartz as major phases. During 15 days of bacterial attack, several disseminated grains appear over the surface leading to surface defects or crystallographic heterogeneity. Formation of a homogenous film over the sulfide was observed after 30 days. Due to increase in grain size with a remarkable increase in thickness of product layer, it slips to the bottom of the column thereby creating barrier for microbial attack and preventing further dissolution.