Acid mine drainage treatment using a process train with low grade ore, concrete waste, and limestone as treatment media

The Philippine mining industry is one of the contributors to its economy having ranked as the 5th most mineral source in the world. However, the continuous growth of mining activities has led to the environment’s vulnerability due to the harmful effects of acid mine drainage (AMD) that are left without proper disposal and treatment. This has led to the study of other alternative alkaline-generating materials that are economic and environmental to treat AMD. In past studies, batch experiments were normally done to test the effectivity of the alkaline-generating agents. However, there were some limitations determined in each agent. In this study, the effect of low-grade ore (LGO), concrete waste, and limestone in a successive process train was studied and the best process train was determined. Six full factorial analysis was performed following a constant ratio of 0.75 mL AMD/g media with a 15-minute retention time before the sampling collection. The X-ray fluorescence (XRF), X-ray diffraction (XRD), and specific surface area of each media were analyzed as well as the physicochemical properties of the initial and treated synthetic AMD including pH level, Oxidation-Reduction Potential (ORP), Electric Conductivity (EC), Total Dissolved Solids (TDS), heavy metals, and sulfates concentrations. Through the experiment, it was observed that LGO has the greatest capability in %metal and sulfates removal followed by concrete waste then limestone. On the other hand, concrete waste has the greatest capability of neutralizing AMD followed by limestone then LGO. Ranking system was utilized in which each parameter was normalized and tallied based on the DAO 2016-08 water type class C effluent standards. With this, Run 4 (Limestone-LGO-Concrete waste) was determined to be the best process train which was able to raise the pH of AMD to 8.08 and removed 38.90% Fe, 94.30% Ni, 71.76% Al, and 51.69% Sulfates. With this, it can be said that a process train is a more effective way of treating AMDs as compared to single media and that the order of the media in the treatment is also significant