标题：EXPERIMENTAL STUDY THE EFFECT OF SULFATE AND RETENTION TIME ON SOLUBLE AL CONCENTRATION AND SPECIES OF PRECIPITATES DURING NaOH NEUTRALIZATION OF AL-BEARING ACID MINE DRAINAGE
摘要：The effects of the SO_4~(2-) on the concentration of soluble Al and species of precipitates during Al- bearing acid mine drainage (AMD) treatment with NaOH was investigated. The results showed that SO_4~(2-) affected Al concentration and the content of S in the formed precipitates during AMD neutralization. In short retention time (<=30 minutes), SO_4~(2-) has little effect on Al concentration and solution was approximately in equilibrium with amorphous Al(OH)_3. When retention time became longer (48 hour), Al concentration decreased and solution was no longer in equilibrium with amorphous Al(OH)_3. X-ray diffraction (XRD) analysis showed that crystalline Al(OH)_3 (gibbsite) particles were not detected in precipitates. Thermogravimetric analysis (TGA) and SEM analysis showed the proportion of S in precipitates increased with time and initial SO_4~(2-) concentration. These results indicated that Al ions were immediately precipitated due to the formation of amorphous Al(OH)3 after the addition of NaOH. In retention time, Al concentration ions and suspended Al-solids combined with SO_4~(2-) ions to form Al-SO_4~(2-) precipitates and made Al concentration decrease. The combination of SO_4~(2-) ions with Al-ions to form Al-SO_4~(2-) precipitates lead to the Al concentration in solution less than the solubility of amorphous Al(OH)_3 after long retention time.
关键词：Al-bearing acid mine drainage;aluminum speciation;X- ray diffraction;Thermogravimetric analysis;Mineql+ model;amorphous
