Study on Bioleaching of Sulfur in Iron Ore by Mixed Culture

Abstract

Iron ore is the raw material for steel production, in addition to iron and slag major component, still contains sulfur and phosphorus compounds and other harmful elements, is the potential adverse effects of factors constitute the steel product quality and environment. Sulfur in iron ores into the steel products will not only produce "heat brittle" phenomenon, but also in the sintering process by roasting produce sulfur dioxide into the air, causing damage to the atmosphere and ecological environment. A typical of the high sulfur iron ore from Inner Mongolia, China, iron grade of 53.06% and sulfur content is 2.76%, the main metal mineral in the ore is magnetite, followed by magnetic pyrite, pyrite and siderite, otherwise a small amount of copper mineral chalcopyrite, bornite. In this work, a mixed culture composed by Sulfobacillus thermotolerans, Leptospirillum ferriphilum and Ferroplasma acidiphilum was used to leach the sulfur in iron ore samples, we investigated the leaching rate of sulfur under different initial pH, temperature and pulp density conditions. The results showed that under the condition of the initial pH of 1.8, the temperature was 33 °C, and pulp density 15%, after 7 days of oxidation, we got a yield of 80.16% product in which iron grade of 62.31% and sulfur content is 0.17%. Compared with original sample, sulfur content decreased 95.06%, iron grade increased by 9.25%, and iron recovery was 94.13%. From the results it can be concluded that this microbial process for high sulfur iron ore lead to a significant effect of sulfur reduction and substantial increase in iron grade.