Kinetics of Neutralization of Polymetallic Mining Discharges from the Perkoa Zinc Deposit in Central-Western Burkina Faso

Oxidized and acidic mining discharges (pH between 4 and 5) from the Perkoa zinc mine in Burkina Faso consisting of waste rock, crusher rejects and mining tailings were sampled and used for neutralization tests with calcareous dolomite (for six months). The mining discharges and the calcareous dolomite were previously characterized. Columns of 60 cm length and 15 cm diameter were used for the tests. Then, 2.62 kg of calcareous dolomite was deposited on the mining discharges in each column. Two liters of deionized water are added every 15 days to each column. Samples were taken at the outlet of the columns at time intervals and then analyzed to assess the evolution of pH, electrical conductivity and contents of PHEs (Potentially Harmful Elements) over time. Following the neutralization tests on solid mining discharges, neutralization tests were also carried out on acid leachates resulting from the oxidation of these same solid mining discharges with calcareous dolomite. The results show that calcareous dolomite is very effective for the neutralization of SR (Sterile Discharges) and the precipitation of PHEs contained therein. It is also effective in buffering acidic effluents from these sterile discharges. As for other mining discharges (crusher rejects and mining residues), although calcareous dolomite is not effective in neutralizing these oxidized and acidic solid discharges, it is however effective in precipitating PHEs such as arsenic and lead. Calcareous dolomite is also effective in buffering acid leachates from these oxidized and acidic mining discharges (crusher rejects and mining tailings).