LAUSR

Abstract Chemical oxidation of mineral coal tailings is one of the most important environmental issues during the lifetime of a mine. The presence of sulfur compounds favors the occurrence of metal acid leaching, which contaminates water with bioaccumulative metals, rendering it unsuitable for domestic and agricultural use. The biomining of residual iron present in these tailings and its transformation into high added-value by-products is economically and environmentally attractive. The extraction of residual iron from rhomboclase and its transformation into nanoparticles by Rhodococcus erythropolis ATCC 4277 free-cells in a stirred tank reactor was studied. R. erythropolis ATCC 4277 biomining capacity was improved by diminishing stirring rate and oxygen flow rate of stirred tank reactor. According to the results of the 22 full factorial design, smaller sizes of iron-based nanoparticles (