Iron Minerals Removal from Different Quartz Sands

Abstract

Quartz sand occurs in varying degrees of purity in dependence on the iron mineral composition, but only a small percentage is suitable for the glass industry after washing and magnetic separation treatment. Bioleaching in combination with washing can increase the quality of quartz sands. The addition of glucose in the leaching medium was important for the continuing leaching activity of iron by heterotrophic bacteria. The amount of bacterial iron removal was not directly proportional to the initial iron content of untreated samples. It was dependent on the mineralogical composition of the quartz sandswith kaolinite, illite encapsulated and sealed by goethite (Q1), quartz sands with phengite, kaolinite encapsulated and sealed by siderite (Q2), quartz sands with glauconite encapsulated and sealed by clinoptilolite and Fe smectite (Q3). Heterotrophic bacteria decomposed these sealed polymineral grains with the iron dissolution and caused the formation of a fine–grained fraction of mineral particles predominantly below 49μm in size. Bioleaching resulted in a 50% decrease in Fe content of Q1, in a 47% decrease in Fe content of Q2 and in a 30% decrease in Fe content of Q3 after 83 days bacterial treatment. This bioleaching pretreatment may be used for the decomposition of iron minerals sealed by silicate minerals and the removal iron surface coatings from different quartz sands. The elutriation process can removed the fine–grained iron particles bioformed after bioleaching. The reductive dissolution of iron polyminerals and washing process may have biotechnological application in the quality improvement of quartz sands.