Fine Particle and Aerosol Technology Laboratory, Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.
Fine Particle and Aerosol Technology Laboratory, Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
J Hazard Mater. 2020 Dec 5;400:123315. doi: 10.1016/j.jhazmat.2020.123315. Epub 2020 Jun 25.
This study assesses the potential of thermal processing for detoxification of wood-combustion ashes that contain high levels of Cr and Cd. Thermal treatment (1000 °C) of bottom ash and fly ash in an oxidising gas (air) atmosphere resulted in: low volatilisation of Cd and most other heavy metals, oxidation of Cr in the ashes to Cr (VI), and, in the case of the fly ash, significantly increased leaching of Cr and Mo. Thermal treatment in a nitrogen atmosphere resulted in local reducing conditions due to oxidation of ash-derived carbon to CO (g). Thermal treatments in this atmosphere and in a reducing atmosphere consisting of 10 % H and the balance N detoxified the ashes in at least two ways: (i) by substantially removing Cd, Pb, Bi, Tl, and, in the case of the fly ash, Zn from the ashes by volatilisation; and (ii) by thermal reduction of Cr (VI) in the ashes. There was at least a 100-fold reduction in the leaching of total Cr from both the bottom ash and the fly ash following the thermal treatments in reducing conditions. Chromium only leached from the detoxified bottom ash to a significant extent in acidic conditions (pH < 4).
本研究评估了热加工对含有高浓度 Cr 和 Cd 的木材燃烧灰分进行解毒的潜力。在氧化气体（空气）气氛下对底灰和飞灰进行热处理（1000°C）导致：Cd 和大多数其他重金属的挥发性低，灰分中的 Cr 被氧化为 Cr（VI），并且在飞灰的情况下，Cr 和 Mo 的浸出明显增加。在氮气气氛下进行热处理会由于灰分中碳氧化生成 CO（g）而导致局部还原条件。在这种气氛和由 10%H 和平衡 N 组成的还原气氛下进行的热处理至少通过两种方式对灰分进行解毒：(i) 通过挥发从灰分中大量去除 Cd、Pb、Bi、Tl，并且在飞灰的情况下，通过挥发去除 Zn；(ii) 通过热还原灰分中的 Cr（VI）。在还原条件下进行热处理后，底灰和飞灰中总 Cr 的浸出量至少减少了 100 倍。只有在酸性条件（pH < 4）下，解毒后的底灰中才会大量浸出 Cr。
