Determination of Metal Adsorption Capacity of Soils for Disposal of Mining Process Solutions by Land Application

Abstract

During mining and processing of precious metals it is often necessary to dispose of treated process solutions to manage the on-site water balance. The solutions typically have elevated levels of trace metals and possibly cyanide. Land application, where solution is applied to soils at a controlled rate, can be an effective means of treatment and disposal. Treatment of the solution occurs as metals are attenuated by soils. Important mechanisms of removal include adsorption by clays, organic matter, and hydroxide and oxide minerals. Adsorption batch tests using synthetic treated mine process solution were performed on a O to 6 inch loam soil from a proposed land application area at a western U.S. precious metals mine to characterize the adsorption behavior of silver, cadmium and copper. Results of testing were used to construct adsorption isotherms to predict the maximum adsorptive potential of, and metal loads to, the soil. The results indicate that the soils were effective at reducing silver, cadmium and copper levels in the process solution and that soil had ample adsorption capacity for these metals, suggesting periodic land application of treated mining process solutions can be a safe, effective management tool.