Depression of iron oxides with corn starches

A review of the industrial utilisation of corn starches in flotation, in Brazil, is presented with emphasis on iron oxides depression in the reverse cationic flotation of itabiritic ores. The current overall consuption reaches 40,000 metric tons per yeaer, iron ores concentration representing approximately 80% of the total amount. The industrial replacement of very pure conventional starch (assaying over 98% amylose + amylopectin on a dry basis) by coarser non conventional starches (containing around 7% proteins + between 1% and 3% oil, beyond amylose + amylopectin) is discussed. Some relevant aspects of different starch types are reported, highlighting an analysis of the action of the major individual components. The experimental results from microflotation tests in a modified Hallimond tube showed that zein, the most abundant corn protein, is a hematite depressant as efficient as amylopectin and conventional corn starch. The poorest depression performance came from a non conventional starch with a high oil content.