Determination of optimum material ratio of locally available neutralizing agents as mixed media for passive treatment of acid mine drainage

• Main Author: Pocaan, Joshua Pascual
• Format: text
• Language: English
• Published: Animo Repository 2023
• Subjects: Acid mine drainage—Purification; Neutralization (Chemistry); Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_chemeng/12; https://animorepository.dlsu.edu.ph/context/etdm_chemeng/article/1014/viewcontent/Determination_of_Optimum2_Material_Ratio_of_Locally_Available_Neut_Redacted.pdf
• Institution: De La Salle University

Acid Mine Drainage (AMD) is a problem found in different water bodies due to their low pH and high concentration of metals. Different materials have been studied to treat this, including locally available materials such as limestone, low-grade ores, concrete wastes, and fly ash. Previous studies have shown that individually, they have the potential to treat AMD due to their ability to generate alkalinity, however with some limitations. To address this, a mixed media approach on the four materials was used to increase the pH and remove metals (Fe, Cu, Al, Mn, and Ni), and sulfates. After characterization of the individual materials using SEM-EDS, XRF, and XRD, twenty (20) mixed media compositions were identified to create a statistical model following a response surface methodology mixture optimization design of experiment. A ratio of 0.75 mL of synthetic AMD per gram of media was used throughout the laboratory-scale experimental runs, following the study of Turingan et al. (2020a). Overall, runs using mixed media were able to address all parameters except for sulfates. Using this data, mixed media composition was optimized to have the treated AMD meet the Philippine effluent standards. A total of three optimized mixed media compositions were identified in wt%: (1) 43% LGO, 40% Limestone, 17% CW, (2) 44% LGO, 51% Limestone, 6% CW, and (3) 89% Limestone, 11% LGO. Overall, these mixed media compositions were able to meet effluent standards, except for sulfates which have increased in concentration. Generally, the mechanism involved in removing the pollutants is by sorption following further analysis through geochemical modelling.