Recovery of Al(iii) and Fe(iii) from Acid Mine Drainage using CaO and their Subsequent Use in Fluoride Removal from Water

Abstract

Acid mine drainage (AMD) refers to the drainage of coal mines with heavy sulphur-bearing rocks. The highly acidic nature and higher metal concentration of AMD poses a severe risk to the environment. The purpose of this study was to evaluate the potential of utilising CaO for the recovery of aluminium and iron hydroxides from AMD and their subsequent application in defluoridation. Batch experiments were caried out to determine the rate of neutralization with various CaO dosages and contact time. The results showed that optimum conditions for neutralizing AMD using CaO are 45 min of contact time and 10 g of CaO dosage, where the pH was found to range from 7.23 to 7.40. The EC ranged from 180 to 195 µS/cm, causing a higher formation of insoluble aluminium and ferric hydroxide precipitates, demonstrating that CaO effectively raises the pH of AMD when increasing the dosage. The study revealed that CaO can be used for the recovery of Al(OH)3 and Fe(OH)3. Recovery efficiencies were as high as 99.89 and 97.49% for Fe(iii) and Al(iii) respectively. The defluoridation study using the recovered metal hydroxides proved to be ineffective, as the adsorption capacity was calculated to be 0.45 mg/g. Some new methods and factors can be implemented to obtain acceptable results.