Cationic starches as flocculants of iron ore tailing slime

Abstract

This study aimed to evaluate the use of cross-linked cationic starch and pregelatinized cationic starch as flocculants in the sedimentation of iron ore tailing slime seeking a less toxic and less expensive alternative when compared with the use of polyacrylamide. The characterization of a sample from the slimes thickener’s feed indicated the presence of hematite, quartz and kaolinite, with about 50% of the particles below 10 μm. Samples of minerals of majority presence (hematite and quartz) were used to perform aggregation tests for each cationic starch at dosages 1, 10 and 100 mg/L in the pH range 6 to 9. The pregelatinized starch had the best results for the percentage of sedimented material for both hematite and quartz in the dosages 10 mg/L at pH 7 (99% of sedimented material). Polyacrylamide showed low values of sedimented quartz (less than 50%). Jar Test assays were then performed using the slimes thickener’s feed sample and the pregelatinized starch, aiming to optimize the dosage, agitation time and sedimentation time variables. The best results in the Jar Test assays were the test using 10 mg/L dosage, 20 min of agitation and 60 min of sedimentation, and the test using 50 mg/L dosage, 10 min agitation and 10 min of sedimentation.