AMAZONIAN BAUXITE BENEFICIATION USING A REVERSE FLOTATION CIRCUIT

Amazonian bauxite is a lateritic bauxite composed of gibbsite as the main mineral (source of available alumina) associated with gangue minerals such as iron oxides, titanium oxides, quartz, and kaolinite (source of reactive silica). In Brazil, bauxite beneficiation plants seek to remove kaolinite in desliming stages using hydrocyclones. In the Bayer process, kaolinite reacts with and consumes sodium hydroxide, forming DSP (desilication product) increasing production costs and the residue generation. A sampling program was carried out at Hydro’s Paragominas Beneficiation plant for flotation testing at bench-scale. Using a flotation circuit with one rougher, one scavenger and three cleaner stages, tests were carried out at natural pH using 200 g/t of Flotinor 16939 in each flotation stage. The results showed that the addition of two cleaner stage improved the concentrate chemical quality, reducing the reactive silica grade and increasing the available alumina grade. Only rougher stage decreased the reactive silica grade from 5% to 4% and increased the available alumina from 42% to 46.5% with alumina recovery of 90.8%. The addition of cleaner I and II increased the available alumina to 49.5% decreasing the reactive silica to 2.8%. The mass recovery and alumina recovery of the circuit considering rougher, cleaner I and II were 64.8% and 72.0%, respectively. The scavenger and cleaner III stages did not bring benefits to the circuit.