The fate and impact of contaminants in a biological iron oxidation and jarosite precipitation process

摘要

Biological iron oxidation results in both soluble and precipitated ferric iron, dependent on pH conditions.Soluble ferric iron plays a well-documented role in hydrometallurgical processing. Ferric ironprecipitation, however, plays a key role in the removal of various soluble elements from solution via co-precipitation effects. This removal process reduces the soluble concentration of elements that would otherwise inhibit bioleaching microorganisms. Hydrometallurgical process solutions often contain variouscontaminant elements due to the dissolution of gangue minerals during ore processing. In this work, theeffect of a combination of often-encountered contaminants (5 g L~(-1) Mg, 2 g L~(-1) Al, 0.4 g L~(-1) Mn, 0.2 g L~(-1)Co, 0.05 g L~(-1) F and 0.05 g L~(-1) As) on ferrous iron oxidation activity at room temperature as well as thefate of the contaminants was evaluated. The results showed iron precipitation resulting in notable co-precipitation effects for F (54 %) and As (17 %), the two main elements with known severe inhibitoryeffects on bioleaching bacteria growth and activity. Other contaminant elements were precipitated to alesser extent,12 % of Mg and <1 % of Al, Cl, Co and Mn. The combined presence of these contaminantscaused a modest decrease in biological iron oxidation rate (from 1.1 to 0.9 g L~(-1) h~(-1)) and extent (from 99to 98 %) and increased the extent of iron precipitation from 16 to 23 % at an influent Fe~(2+) concentrationof 13-14 g L~(-1) and a hydraulic retention time of 13-15 h.