Treatment of Historic, Sulphide-rich Mine Waste from Ljusnarsberg Using Alkaline By-products

Sammanfattning: Alkaline by-products were used in a leaching test to study their effect on highly weathered, sulphide-rich mine waste from Ljusnarsberg for the attempt to neutralize the leachate and immobilize trace metals through precipitation of secondary minerals. Leaching was performed at liquid/solid ratio of 0.5-20 with 10 % alkaline material. It was found that immobilization of trace elements (Cd, Pb, Zn and Cu) were successful in systems able to neutralize the mine waste. The systems with a lower pH increase (4-5) leached an increased amount of both Zn and Cd compared to the reference. Fly ashes are found to be the most effective material regarding pH and metal immobilization but are also found to have the highest increase of molybdenum and antimony, trace metals originating from the ashes. High chloride content is another concern regarding fly ashes, as high levels in the leachate would cause a concern for the nearby fresh water.