Rates of Arsenopyrite Oxidation by Oxygen and Fe(III) at pH 1.8-12.6 and 15-45 C

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• 作者：Yunmei Yu ; Yongxuan Zhu ; Zhenmin Gao ; Christopher H. Gammons ; Denxian Li
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：September 15, 2007
• 年：2007
• 卷：41
• 期：18
• 页码：6460 - 6464
• 全文大小：471K
• 年卷期：v.41,no.18(September 15, 2007)
• ISSN：1520-5851

文摘

The oxidation rate of arsenopyrite by dissolved oxygenwas measured using a mixed flow reactor at dissolved O₂concentrations of 0.007-0.77 mM, pH 1.8-12.6, andtemperatures of 15-45 C. As(III) was the dominant redoxspecies (>75%) in the experimental system, and the As(III)/As(V) ratio of effluent waters did not change with pH.The results were used to derive the following rate lawexpression (valid between pH 1.8 and 6.4): r =10^{(-2211±57)/T}(mO₂)^0.45±0.05, where r is the rate of release ofdissolved As in mol m^-2 s^-1 and T is in Kelvin. Activationenergies (E_a) for oxidation of arsenopyrite by O₂ at pH1.8 and 5.9 are 43 and 57 kJ/mol, respectively, and theycompare to an E_a value of 16 kJ/mol for oxidation by Fe(III) at pH 1.8. Apparent As release rates passed through aminimum in the pH range 7-8, which may have beendue to oxidation of Fe²⁺ to hydrous ferric oxide (HFO) withattenuation of dissolved As onto the freshly precipitatedHFO.