Pyrite oxidation at circumneutral pH

摘要: Abstract Previous studies of pyrite oxidation kinetics have concentrated primarily on the reaction at low pH, where Fe(III) has been assumed to be dominant oxidant. Studies circumneutral necessitated by effective pH buffering in some systems, often implicitly that oxidant must dissolved oxygen (DO), owing diminished solubility Fe(III). In fact, Fe(III)(aq) is an but cannot sustained absence DO. The purpose this experimental study was ascertain relative roles and DO pH. rate first-order with respect ratio surface area solution volume. Direct determinations both Fe(II)(aq)> demonstrated a dramatic loss Fe(II) from phase excess for which alone could account. Based data, we concluded adsorbed onto surface. Furthermore, preferred as adsorbate Fe(III), attribute electrostatic acid-base selectivity. We also found either or reduced presence aqueous Fe(II), leads us conclude that, under most natural conditions, neither nor directly attacks present evidence suggests mechanism involves Fe( II ) giving up electrons resulting rapidly accepting pyrite. Fe is, thus, cyclically oxidized reduced, while it acts conduit traveling Oxygen transferred hydration sphere S. cycle reduction successive addition S continues until stable sulfoxy species dissociates Prior work shown lower state than sulfate (e.g., thiosulfate polythionate) may accumulate circumstances not conditions experiments reported here. these experiments, accumulation proportional oxidation.