『Abstract
　We used a mixed flow reactor system to determine the rate and infer a mechanism for arsenopyrite (FeAsS) oxidation by dissolved oxygen (DO) at 25℃ and circumneutral pH. Results indicate that under circumneutral pH (6.3-6.7), the rate of arsenopyrite oxidation, 10^-10.14±0.03 mol m^-2 s^-1, is essentially independent of DO over the geologically significant range of 0.3-17 mg L^-1. Arsenic and sulfur are released from arsenopyrite in an approximate 1:1 molar ratio, suggesting that oxidative dissolution by oxygen under circumneutral pH is congruent. Slower rates of iron release from the reactor indicate that some of the iron is lost from the effluent by oxidation to Fe(III) which subsequently hydrolyzes and precipitates. Using the electrochemical cell model for understanding sulfide oxidation, our results suggest that the rate-determining step in arsenopyrite oxidation is the reduction of water at the anodic site rather than the transfer of electrons from the cathodic site to oxygen as has been suggested for other sulfide minerals such as pyrite.』

1. Introduction
2. Materials and methods
　2.1. Preparation of arsenopyrite
　2.2. Mixed flow reactor system
　2.3. Analytical methods
　2.4. Rate calculations, error analysis, and statistical analysis
3. Results and discussion
　3.1. Arsenopyrite dissolution behavior
　3.2. Arsenopyrite oxidation kinetics
　3.3. Arsenic speciation
　3.4. Arsenopyrite oxidation reactions
　3.5. Mechanistic implications
4. Conclusions
Acknowledgments
References