Cationic tannins as aggregation agents in the flocculation on hematite–silica system

Abstract

ABSTRACT This study aims to evaluate the use of commercial tannin derivatives, namely, tannin 1 (CT1), tannin 2 (CT2), tannin 3 (CT3), and extract of tannin produced from angico bark, as aggregation agent in hematite–silica systems. Hematite and quartz were used in aggregation tests at dosages of 1, 10, and 100 mg/L at pH values of 6–9. The zeta potential and Jar tests were conducted in the best conditions of aggregation tests. The condensed tannin content of the commercial reagents is approximately similar, and it exceeds the content found in the extract obtained from angico bark. CT3 demonstrated superior percentages of sedimented material for both minerals at a dosage of 10 mg/L and pH 7 (97.12% and 95.68% for hematite and quartz, respectively). The aggregation agent produced from the angico bark displayed good sedimentation results for hematite (>90%); however, the results for quartz were unsatisfactory. The isoelectric point shifts to pH 8 when each mineral was conditioned with CT3. The jar test revealed higher sedimentation of the compositions for the lowest velocity gradient (60 rpm) with low turbidity values in the supernatant; however, the lowest turbidity (24.71 NTU) is observed in the sample with a higher percentage of hematite.