Second Pilot-Plant Bioleaching Verification of the Iron Removal from Quartz Sands

Abstract

The bioleaching processfor silicate industrial minerals using heterotrophic bacteria is a technology that has not beenapplied onindustrial scaleyet. The laboratory experimentsofiron mineral removal from quartz sands were verified during the second pilot-plant via bioleaching by usingbig bags. The composition of medium, pH, and concentration of oxygen, presence of active bacterial species, granularity and bounds of iron minerals as well as the mineralogical composition of the quartz sands were the important factors of the pilot - plant bioleaching. For industrial application, leachate permeability of big bags is very important for the release of the bacterial iron. It was observed that any inhibitory effect of the bacterial dissolution of iron during the bioleachingof quartz sands in big-bags compared with bioleaching in basins. The zeta-potential measurement of quartz sands before and after bioleaching was comparable to the surface charge of particles. Apparently, the shift reflects a loss of Fe-ions from the surface of quartz particles in leachate which leads to even more negative surface of the particles after bioleaching. In this way it was possible to remove iron from the quartz sand from 0.26% to 0.13% Fe2O3 by pilot – plant bioleaching in basins. Bioleaching resulted in a 50% decrease in Fe content of quartz sands after 83 days of bacterial treatment. The industrial washing process removed the fine fractionof Fe2O3 to 0.09%and the subsequent magnetic separation decreased Fe2O3content to 0.08%. The second pilot plant bioleaching with big bags was comparable with the first pilot plant tests and also with laboratory tests of the iron removal. This bioleaching pretreatment may be used for the removal of fine undesirable iron minerals from the surface of industrial mineralsunder the stationary solution conditions.