Research On Preparation Of Aluminum Oxide And Flocculant From Bauxite Tailing

Abstract:In this thesis, the aluminum and ferrum in bauxite tailing was transformed into water solution by acid leaching, then ferrum was removed by the jarosite method, the aluminum was extracted by aluminum ammonium sulfate and prepared into aluminum oxide. The waste water and the filter residue were made into flocculant.Optimal conditions for ferrum removal are as follows. The temperature is95℃and the pH=2.0, the crystal seed dosage is lOg/L and the stirring rate is300rpm for180mins. Under this condition, the Iron removal rate is95%.Optimal conditions for aluminum recoverage are as follows. The staring temperature is80℃and the A13+/NH4+molar ratio is1.2, the cooling rate is20℃/h and the final temperature is5℃, the stirring rate is300rpm. Under this condition, the aluminum recoverage is82.9%. Through secondary crystallization and calcination, the α-Al2O3was prepared, of which the component is99.73%. The main impurity are SiO2and Fe2O3and the content is0.0771%,0.0336%, respectively. The aluminum recovery is62.8%, which can be used in electronic ceramics field.The thermal decomposition of aluminum ammonium sulfate was studied by thermal analysis and the kinetics of deaminize and desulfurization were analyzed by non-isothermal multiple scan rate method. The result shows that the kinetic triplets of deaminize is E=210.48kJ/mol and logA=10.96s-1, the reaction mechanism is autocatalysis reaction; the kinetic triplets of desulfurization is E=219.64kJ/mol and logA=7.894s-1, the reaction mechanism is n-Dimensional nucleation.The waste water and the filter residue from the preparation process of Al2O3are used to synthesized flocculant. Optimal conditions are as follows. The (Al+Fe)/Si molar ratio is1:1and the pH is5.5, the aging time is1hour. Optimal conditions for dealing with waste water are pH=8and dosage is60ml/L. The flocculant has good effect for waste water which is polluted by methyl orange, xanthate or methylene blue.