Prevention of acid mine drainage by agglomeration of reactive tailings with selected binders and bactericidals

Abstract

Acid mine drainage is one of the largest environmental problems facing the mining and processing industries. Sulfide ores that are generated during the mineral dressing unit operation are the main source of acid mine drainage. With the action of oxygen and autotrophic organisms, these sulfides are oxidized to generate sulfuric acid and thus results in the dissolution of heavy metals. The acids as well as heavy metals permeate through the ground and contaminate ground water and rivers and streams. A preventive technique to control acid mine drainage by agglomeration process is found very effective in mitigation of acid mine drainage. This technique was conducted using reactive tailings agglomerated with alkaline binders. The cold bonded agglomerates, after a specified curing period, are strong and resistant to weathering. Leaching and accelerated weathering tests with agglomerates show that the dissolution of most of the heavy metals can be reduced to 100 percent. X-ray CT Scan and SEM / EDAX show that agglomerates are resistant to weathering. The long term stability and prediction of acid mine drainage potential of the tailings and agglomerates were conducted using the AC Impedance Spectroscopy technique. Results of Impedance Spectroscopy were compared with that of conventional leaching experimental results. It is indicated that impedance spectroscopy can be used to assess the reactivity of the tailings. T. ferrooxidans play an important role in the genesis of acid mine drainage. These bacteria which are indigenous to areas where pyrite occurs can accelerate the oxidation rate of sulfide mineral tailings and lead to acid generation and heavy metal dissolution. Various chemicals have been used as bactericides to inhibit T. ferrooxidans. The bactericides developed by Buckman laboratory in addition to traditional bactericides were studied in this program. Leaching tests and microscopic analyses show that the bactericides are indeed effective in controlling the activity of T. ferrooxidans.