Flotation of carbonates from dolomitic iron ore: synthesis, characterization and application of a novel N,N-bis(2-hydroxyethyl)oleamide collector

The Brazilian dolomitic itabirites are considered marginal resources and deposited in waste rock dumps as the cationic reverse flotation circuits present limitations to remove carbonate minerals. This work proposes the synthesis and application of N,N-bis(2-hydroxyethyl)oleamide as a collector in the flotation of carbonates present in dolomitic itabirites. Hematite, quartz, calcite, and dolomite samples were characterized by XRPD and XRF, indicating high purity. The novel collector was characterized by NMR, ATR-FTIR, zeta potential and surface tension measurements, whereas its selectivity was evaluated in microflotation tests, and adsorption was studied via zeta potential and ATR-FTIR. The collector showed maximum selectivity in alkaline condition (pH 10) at 50 mg/L, at which only dolomite and calcite were recovered at 74.7 % and 78.1 %, respectively. The adsorption studies were performed at pH 10, showing that the collector adsorbs non-specifically onto dolomite and calcite, but not quartz and hematite, which is consistent with the flotation results. Microflotation tests with a mixed mineral sample in the presence of corn starch confirmed its potential to depress the carbonate minerals, requiring conditioning with collector to take place prior to the addition of depressant. This approach, followed by conditioning with etheramine showed potential to separate dolomite, calcite, and quartz from hematite.