Abstract
The standard practice in nickel/copper operations and at the Eagle Mine is to separate chalcopyrite from pentlandite in the last flotation circuit by adding lime to suppress the pentlandite. Control of the process with lime has a series of disadvantaged side effects, including pumping lime as a slurry, excessive scaling issues, and high costs of soda ash to treat thickener overflow returning to the process water tank. By examining the oxidation difference between the minerals and the pH of the slurry, using the right oxidating agent has potential to eliminate lime from the circuit. Potassium permanganate, a common water treatment chemical, was chosen for its oxidation potential without acid pHs and its inert products after the oxidizing process. The exact chemical reaction is unknown, but it is theorized that the permanganate removes the isopropyl alcohol part of the xanthate, rendering it hydrophilic. Testing has shown it to be more effective in limiting pentlandite flotation than lime. Higher doses proved to slow down chalcopyrite flotation as well, allowing for better control of the separation process as the Eagle nickel concentrate requires at least 2% copper content for economic reasons. The savings in soda ash usage is significant.