Treatment of backwater in bauxite flotation plant and optimization by using Box-Behnken design

Abstract

Abstract Flotation indexes gradually decrease with the increase of cycle time of the backwater in bauxite floatation, and discharge of backwater brings environmental risk. In this study, methods such as Fenton-oxidation, adsorption and coagulation were used in the treatment of backwater, the flotation indexes were checked after backwater treatments, and Box-Behnken design (BBD) was used in the optimization of the main operating parameters. The results reveal that flotation indexes are effectively improved after coagulation treatment by polyaluminum ferric chloride (PAFC). The optimum parameters predicted by BBD are pH 7.55, 1.09 g/L PAFC dosage and temperature of 25 °C. Under these optimum conditions, a maximum recovery of Al2O3 of 82.83% and a minimum A/S of 1.30 of tailings are gained, while the deviations are less than 3% from the predicted values. These findings encourage the application of BBD for the optimization of critical parameters in backwater treatment.