Andre Carlos Silva

Abstract:

The iron content in ores that will be mined is steadily decreasing. The lower grade ores require finer grinding. Metallic oxides and hydroxides such as iron oxides become electrical when dispersed in aqueous environment. The changes on the oxides surfaces and the formation of the electrically charged interface are controlled by the pH and the ionic force of the solution in which they are dispersed. The factors lead to the need of investigating the effect of dispersion on flotation, thickening, and filtration stages. This laboratory scale study aimed at contributing to a better understanding of iron ores processing addressing the dispersion of hematite pulps in the presence of dispersing or aggregating reagents. Fourteen organic and inorganic reagents were evaluated in dispersion experiments. The study of hematite dispersion in the absence of reagents showed a decrease in the dispersion degree in the pH range between 6.5 and 7.5. The additions of starch and ground corn (fuba) caused aggregation of hematite in the full pH range, while dextrin increased the dispersion degree in the alkaline range. Tannin, a natural organic reagent, not aggressive to the environment in case of disposal, increased the hematite dispersion degree even at low concentrations (150 g/t). Citric acid also increased the hematite dispersion degree. The SiO2 /Na2O ratio is a factor that may interfere in the action of sodium silicate in iron ore flotation. The sodium silicate - C112, presenting the lowest ratio, did not change significantly the dispersion degree; sodium silicate R3342, presenting the highest ratio, led to the highest dispersion degree. Sodium silicate R2252 caused an increase in the dispersion degree around pH 8.5. DismulganV3377 did not affect significantly the dispersion degree leading to results similar to those achieved in the absence of reagents. Dispersogen LFS and Polymax T10 increased the dispersion degree in the alkaline pH range. Bozefloc AE 738 may be suggested as flocculent, enhancing the aggregation at pH 10.5 at dosages of 500g/t and 1000g/t. Dispersol 589 caused a significant increase in the dispersion degree in the full pH range. At pH = 10.5, Depramin 158 led enhanced significantly the dispersion degree. In the acidic pH range the dispersion degree reached approximately 50%.