J. Rivera’s scientific contributions

Acid Mine Drainage (AMD) is an important source of pollution to the environment, characterized by a very low pH and high metal(loid)s concentration. The objective of this research was to evaluate the effect of three alkaline materials: marl, sandstone and calcareous crust on AMD neutralization and metal precipitation. To achieve this objective, a batch test was design, where a 5/10 alkaline material(g)/AMD(mL) ratio was used. In order to optimize the process, three particle sizes (2–10, 10–20 and 20−30 mm) of each material were used, and water samples were collected during the neutralization time. Due to the extreme pH of AMD used (pH < 2.5), it was necessary to carry out an AMD pretreatment, which consisted of adding 2.5 g of Ca(OH)2 per liter of AMD to raise a pH of 4. This pretreatment was essential because when AMD (pH < 4) was in contact with alkaline material a fast disintegration had place and a viscous substance was forming which prevented water rehabilitation. The results showed that the three alkaline materials reduced Fe, As, Cd, Cu, Pb and Zn concentrations in AMD, due mainly to their high carbonates content, which allowed metal(loid)s precipitation. The removal percentages were 100 % for Fe, Cu and Pb for marl, sandstone and calcareous crust, and about 60 % for Zn and Cd when sandstone was used. The optimal size particle was 20−30 mm for marl, while for sandstone with a size particle of 10−20 mm a considerable reduction of metal(loid)s in AMD was observed. Besides, the contact time required to neutralization of AMD and metal(loid)s reduction was lower for marl and sandstone than calcareous crust. Therefore, the results of this study showed that anyone of these alkaline materials could be used in AMD treatment depending on availability in the study area.