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Effect of pH on Aqueous Se(IV) Reduction by Pyrite

机译：pH值对黄铁矿还原Se（IV）水溶液的影响

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摘要

Interaction of aqueous Se(lV) with pyrite was investigated using persistently stirred batch reactors under O_2-free (< 1 ppm) conditions at pH ranging from ~4.5 to ^6.6. Thermodynamic calculations, an increase in pH during the experiments, and spectro-scopic observation indicate that the reduction of aqueous Se(lV) by pyrite is dominated by the following reaction: FeS2 + 3.5HSeO3^ + 1.5H+ = 2SO42" + Fe2+ + 3.5Se(O) + 2.5H_2O. The released Fe(ll) was partitioned between the bulk solution and pyrite surface at pH ftJ 4.5 and 4.8, with the Fe + density at pyrite-solution interface about 4 orders of magnitude higher than that in the bulk solution, while iron oxyhydroxide precipitated at pH ^ 6.6, resulting in the decrease of dissolved iron. In the Se(lV) concentration range of the experiments, aqueous Se(lV) reduction rate follows the pseudofirst order which is in the form of In m^jy) = ~Mt + In mSe(jyf, where k! is apparent rate constant combining the rate constant fc and pyrite surface area to mass of solution ratio (A/M). And the aqueous Se(lV) reduction rate constant for a standard system (it) with 1 m2 pyrite surface area per lkg solution was obtained to be 1.65 x 10"4h"!,3.28 x lO^h"1, and 4.76 x lO^h"1 at pH around 4.5, 4.8, and '5.1, respectively. The positive correlation between reaction rate and pH disagrees with the theories that protons are consumed when HSeO3~ is reduced to Se°, and negative charge density on pyrite surface increases as pH increases. Thus, a ferrous iron mediated electron transfer mechanism is proposed to operate during the reduction of aqueous Se(lV) by pyrite. pH and iron concentration affect significantly on Se(lV) reaction rate and reaction product.
机译：使用持续搅拌的间歇式反应器，在无O_2（<1 ppm）条件下，pH值为〜4.5至^ 6.6，研究了Se（IV）与黄铁矿的相互作用。热力学计算，实验过程中pH的增加以及光谱观察表明，黄铁矿还原Se（IV）的水溶液主要受以下反应的影响：FeS2 + 3.5HSeO3 ^ + 1.5H + = 2SO42“ + Fe2 + + 3.5 Se（O）+ 2.5H_2O。释放的Fe（II）在pH ftJ 4.5和4.8时在本体溶液和黄铁矿表面之间分配，黄铁矿-溶液界面的Fe +密度比Fe（ll）高4个数量级。大量溶液中，羟基氧化铁在pH ^ 6.6时沉淀，导致溶解的铁减少，在实验的Se（IV）浓度范围内，Se（IV）的水溶液还原速率遵循伪一级反应，即In m ^ jy）=〜Mt + In mSe（jyf，其中k！是表观速率常数，将速率常数fc和黄铁矿表面积与溶液质量的比值（A / M）结合起来，而Se（IV）水溶液的还原率常数对于标准系统（it），每1kg溶液具有1 m2的黄铁矿表面积在大约4.5、4.8和5.1的pH下，分别为1.65×10 4英寸，3.28×10 5英寸-1和4.76×10 4英寸-1。反应速率与pH呈正相关，这与理论上的观点不符：HSeO3〜还原为Se°时质子被消耗，黄铁矿表面的负电荷密度随pH的增加而增加。因此，提出了由亚铁离子介导的电子转移机理，其在通过黄铁矿还原Se（IV）水溶液期间起作用。 pH和铁浓度对Se（IV）反应速率和反应产物有显着影响。

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  • 来源
    《Environmental Science & Technology》 |2011年第7期|p.2704-2710|共7页
  • 作者

    Mingliang Kang; Fanrong Chen; Shijun Wu; Yongqiang Yang; C. Bruggeman; L. Charlet;

  • 作者单位

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China,Graduate University of Chinese Academy of Sciences, Beijing 100049, China;

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;

    SCK.CEN, Research unit R&D Waste Disposal, Boeretang 200, B-2400 Mol, Belgium;

    Environmental Geochemistry Group, LGIT-OSUG, Grenoble University, 38041 Grenoble Cedex 9, France;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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