Innovative oxidation and kinetic studies of ferrous ion by sodium ferrate (VI) and simultaneous removal of metals from a synthetic acid mine drainage

Acid mine drainage (AMD) is considered as one of the main contaminants of watercourse in many countries that have historic or current mining activities. The oxidation process of iron in mine waste is the main cause of acidic, trace element, and sulphate-rich AMD. However, the series of reactions that convert it from one species to another is quite complex and time dependent. This study aimed at oxidizing and performing kinetics studies of the ferrous ion (Fe2+) using sodium ferrate (VI) (Na2FeO4) as well as the removing other metals from a synthetic AMD in a single dosing and mixing unit process to save time and energy consumption. Na2FeO4 was prepared using a wet chemical method. Kinetic study performed using UV-Vis spectroscopy showed a total consumption of Fe2+ during its oxidation process after 30 min with the oxidation percentage ranging between 98.32 and 99.95%. Ferric ions generated from the oxidation of Fe2+ and the self-decomposition of FeO42- ions in water played a big role as a coagulant during the metal removal process. ICP-OES results also demonstrated a complete removal of other metals from a treated synthetic AMD. Pilot-plant studies to demonstrate the suitability of the ferrate process for full-scale application in the treatment of AMD are in the planning stage.