LEACHING COAGULANT MIXTURE FROM BAUXITE TAILINGS, A CASE STUDY AT THE BAUXITE MINE OF BAO LOC, LAM DONG
Abstract
This study aims to optimize the extraction efficiency of coagulant mixture, which is derived from the tailings of bauxite mine located at Bao Loc, Lam Dong. Sulfuric acid (H2SO4) was introduced to obtain the tailing coagulant mixtures including ferric sulfate Fe2(SO4)3 and aluminum sulfate Al2(SO4)3. The rest insoluble residues are unharmful to the environment and could be released. Response surface methodology (RSM) was employed to test the determinant parameters, including temperature, acid ratio and time for reaction. Experiment designs and regression models were performed by Design Expert 11 software and the results indicated that models were quite compatible to experimental data and the correlation coefficient R2 reached to 0.99. Results showed that temperature at 130 ℃, acid ratio at 1.2 L/kg bauxite tailings and reaction time at 2.8 hours are the optimal condition for coagulant extraction. Leaching efficiency of ferric and aluminum were 85.3% and 81.3%, respectively. Further tests on various wastewaters indicated the coagulation efficiency equivalent to the commercial alums. These data suggest the “green way” to treat bauxite tailings, limiting their impacts on the environment and point out the alternative source of coagulant for wastewater treatment.
Từ khóa: Alum, bauxite, coagulation, tailings, optimization.