Valuing Acid-Generating Mine Tailings

Abstract

The objective of this paper is to estimate that value of acid-generating tailings beyond what any residual mineral value lost in the tailings might indicate. Specifically, the value of sulfuric acid produced by acid-generating mine tailings will be estimated. Today, the value of sulfuric acid in a tailing effluent stream is negative and equal to the cost of using lime to neutralize the tailing stream. However, there potentially is more value in sulfuric acid if the treatment process was to focus on changes to an electrochemical process such as the Stiller process. A process circuit is proposed to treat acid tailings effluent. Leveraging the expected chemical reactions occurring in the Stiller cell, stoichiometric-based models are defined for the products (electricity, hydrogen, and metal salts) produced and materials consumed (iron anode) as a function of effluent pH and flowrates. Leveraging the Zinck and Griffith data review of acid drainage treatment operations in Canada, the models are used to estimate the value that can be captured with the proposed electrochemical acid tailings effluent process. The subsequent discussion explores the possibility of expanding the proposed circuit to that proposed in Radziszewski and Blum, a complementary means to prediction acid tailings value, challenges to development, and possible future impacts of the proposed electrochemical approach to treating acid-generating mine tailings.