Present invention describes a biotechnological procedure to remove magnetic sulfur impurities from iron concentrate, wherein includes: to bioleach iron concentrate ores agglomerated in heaps under temperature condition between 5 and 35° C., inoculating the iron concentrate ores with Acidithiobacillus thiooxidans cultures, with an inoculum concentration 104 and 106 cel/g and addition of water supplemented with nitrogen and phosphorous source (0.01 to 0.5 g (NH4)2HPO4/L), without potassium addition, adjusting pH between 1.0 and 9.0, and a feeding rate between 5 and 15 L/h/m2; this procedure allows a removal efficiency above 80% in 21 days, with a maximum iron loss of 3%.