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

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℃.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.

Adsorption behavior of Pb^(2+) and Cd^(2+) ions on bauxite flotation tailings

The adsorption behavior of Pb2+ and Cd2+ ions on bauxite flotation tailings was investigated to demonstrate the adsorptivity of the bauxite flotation tailings.The adsorption percentage of Pb2+ and Cd2+ ions as a function of adsorbent dosage,solution pH value and shaking time were determined by batch experiments.The maximum adsorption percentage of 99.93% for Pb2+ ions and 99.75% for Cd2+ ions were obtained by using bauxite flotation tailings as adsorbent.The methods,such as zeta potentials,specific surface area measurements and the analysis of adsorption kinetics,were introduced to analyze the adsorption mechanisms of the Pb2+ ions on bauxite flotation tailings.The isoelectric point of bauxite flotation tailings shifts from 3.6 to 5.6 in the presence of Pb2+ ions.The specific surface area of bauxite flotation tailings changes from 12.57 to 20.63 m2/g after the adsorption of Pb2+ ions.These results indicate that a specific adsorption of the cation species happens on the surface of bauxite flotation tailings.Adsorption data of Pb2+ ions on the surface of bauxite flotation tailings can be well described by Langmuir model,and the pseudo-second-order kinetic model provides the best correlation for the adsorption data of Pb2+ and Cd2+ ions on bauxite flotation tailings.

Distribution behavior of collector in the desilication system of bauxite flotation

The distribution behavior of the HZB collector (a kind of long chain fatty acid) in the desilication system of bauxite flotation was studied. The results show that the collector tends towards froth products in the steps of the roughing, the first cleaning and the second cleaning, while towards the tailing product in the step of the scavenging, and in each job except scavenging the collector is mainly on the surface of solids. As for the froth product in the step of the scavenging, it is mainly in solution. To the tailing products of every step, it is mainly in the respective solutions. The collector added to the flotation system is mainly taken out by the last concentrate, by which the taken one occupies 65.2% of the whole, among which, 57.8% is by solid and 7.4% by solution, respectively. And the one by the last tail occupies 34.8% of the whole, among which, 8.8% is by solid and 26.0% by solution, respectively. The sum of the collector in the solution of the last concentrate and tailing is 33.4% of the amount of addition collector, and recycling the solutions will be in favor of decreasing the dosage of collector.