Understanding the Mechanisms and Kinetics of Acid and Heavy Metals Release from Pyritic Wastes.
Proc Western Reg Symp on Mining & Mineral Processing Wastes Berkeley SME 1990 :9 pages
When oxidized in the presence of water, pyrite releases acid, dissolved iron, sulfate, and heat, all potentially highly deleterious. Dissolved ions contaminate any drainage from the waste management facility; the products can accelerate subsequent pyrite oxidation by an autocatalytic effect; and the dissolved iron promotes the oxidation of other sulfide minerals, which then release heavy metals that are kept in solution by the acid. Also, the differences in rest potential between ore pyrite and many other sulfides can give galvanic interactions that promote dissolution of the nonpyrite components of the waste. Unfortunately, the rate of pyrite oxidation is difficult to predict and depends, for example, on the nature of the oxidant and the presence of bacteria such as thiobacillus ferrooxidans. This paper reports work done to relate the reactivity to the semiconducting properties of ore pyrite samples from different sources. Samples were chemically characterized by electron microprobe and atomic absorption spectrophotometry. The semiconducting properties were determined from hall effect measurements. The electrochemical behavior was determined by rest potential measurements and cyclic voltammetry studies of single crystals. The results indicate that the electrochemical behavior is correlated to some extent with the composition and electrical properties, but is dominated by the proceding electrochemical history. Care should be taken in using electrochemical studies to predict the rate of acid and heavy metal release from pyritic wastes.
OP; Final Contract Report;
Proc. Western Reg. Symp. on Mining & Mineral Processing Wastes, Berkeley; SME, 1990, 9 PP.
Univ. of California - Berkeley