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Metal Release and Speciation Changes during Wet Aging of Coal Fly Ashes

机译：粉煤灰湿老化过程中的金属释放和形态变化

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摘要

Introduction of coal fly ash into aquatic systems poses a potential environmental hazard because of its heavy metal content. Here we investigate the relationship between solid phase transformations, fluid composition, and metal release and speciation during prolonged wet aging of a class C and class F coal fly ash. The class C ash causes rapid alkalinization of water that is neutralized over time by CO_2 uptake from air and calcite precipitation. The resulting aqueous metal concentrations are below regulatory limits with the exception of Cr; solubility constraints suggest this is released as chromate. Limited As release is accompanied by no change in solid-phase speciation, but up to 35% of the Zn in the ash dissolves and reprecipitates in secondary phases. Similar processes inhibit Ba and Cu release. In contrast, the class F ash causes rapid acidification of water and initially releases substantial quantities of As, Se, Cr, Cu, Zn, and Ba. Arsenic concentrations decline during aging because of adsorption to the iron oxide-rich ash; this is aided by As(III) oxidation. Precipitation processes lower Ba and Cr concentrations during aging. Se, Cu, and Zn concentrations remain elevated during wet aging and solid-phase Zn speciation is not affected by ash-water reactions. Total metal contents were poor predictors of metal release, which is predominantly controlled by metal speciation and the effects of ash-water reactions on fluid pH. While contact with atmospheric gases has little effect on class F ash, carbonation of class C ash inhibits metal release and neutralizes the alkalinity produced by the ash.
机译：由于粉煤灰中的重金属含量高，将粉煤灰引入水生系统会对环境造成潜在危害。在这里，我们研究了C级和F级粉煤灰的长时间湿老化过程中固相转变，流体成分以及金属释放与形态之间的关系。 C类灰烬会导致水快速碱化，并随着时间的流逝而被空气中的CO_2吸收和方解石沉淀所中和。除Cr外，所得的水金属浓度均低于规定的限值。溶解度限制表明这是作为铬酸盐释放的。有限的释放不会伴随着固相形态的变化，但是灰分中高达35％的Zn会在第二相中溶解并重新沉淀。类似的过程会抑制Ba和Cu的释放。相反，F类灰分会导致水快速酸化，并最初释放大量的As，Se，Cr，Cu，Zn和Ba。在老化过程中，砷的浓度会下降，这是因为吸附到了富含氧化铁的灰烬中。这是由As（III）氧化辅助的。沉淀过程会降低时效过程中的Ba和Cr浓度。在湿法老化过程中，Se，Cu和Zn的浓度保持升高，并且固相锌的形成不受灰水反应的影响。总金属含量不能很好地预测金属的释放，金属释放主要受金属形态和灰水反应对流体pH值的影响控制。虽然与大气中的气体接触对F类灰几乎没有影响，但C类灰的碳酸化抑制了金属的释放并中和了由灰产生的碱度。

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  • 来源
    《Environmental Science & Technology》 |2012年第21期|11804-11812|共9页
  • 作者

    Jeffrey G. Catalano; Brittany L. Huhmann; Yun Luo; Elizabeth H. Mitnick; Adam Slavney; Daniel E. Giammar;

  • 作者单位

    Department of Earth and Planetary Sciences, Washington University, Saint Louis, Missouri 63130, United States;

    Department of Earth and Planetary Sciences, Washington University, Saint Louis, Missouri 63130, United States,Department of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa 52242;

    Department of Earth and Planetary Sciences, Washington University, Saint Louis, Missouri 63130, United States,Department of Energy, Environmental, and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, United States,Gemological Institute of America, Carlsbad, California 92008;

    Department of Earth and Planetary Sciences, Washington University, Saint Louis, Missouri 63130, United States;

    Department of Earth and Planetary Sciences, Washington University, Saint Louis, Missouri 63130, United States;

    Department of Energy, Environmental, and Chemical Engineering, Washington University, Saint Louis, Missouri 63130, United States;

  • 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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