Passive treatment of acid mine drainage from the Sidi-Kamber mine wastes (Mediterranean coastline, Algeria) using neighbouring phosphate material from the Djebel Onk mine.

Passive abiotic treatment of acid mine drainage (AMD) was investigated using phosphate mining residuals (raw low-grade phosphate ore, phosphatic limestone wastes, and phosphate mine tailings) from the Djebel Onk mine, Algeria. Laboratory batch tests were performed using the main expected lithologies of phosphate materials in contact with synthetic AMD, which had a low pH (3.08) and contained high concentrations of Fe (600 mg/L), Mn (40 mg/L), Mg (10 mg/L), Zn (20 mg/L), Cu (25 mg/L), As (50 mg/L), and sulfate (3700 mg/L). Phosphate materials were used as an oxic limestone drain to evaluate the increase in the pH of the AMD and metal removal by sorption and precipitation mechanisms. The results showed that all phosphatic lithologies were efficient in the passive treatment of AMD. The pH rapidly increased from 3.08 to 8.47 during water-rock interactions. The neutralization potential comparisons also showed that the phosphatic limestone wastes neutralized more acid than other lithologies. In addition, metals were efficiently removed (95.5% to 99.9%) by all materials. The results of batch sorption tests showed that the concentrations of metals in residual leachates did not exceed the Algerian criteria for industrial liquid effluents. Overall, these findings indicate that passive systems using phosphatic materials from the Djebel Onk mine can be effective for AMD treatment. The use of these mine wastes for passive treatment of AMD would allow the development of integrated management strategies for these residual materials in the context of sustainable development of phosphate mining.