Instituto Nacional del Carbón (CSIC), C/Francisco Pintado Fe, no. 26, 33011 Oviedo, Spain.
J Hazard Mater. 2010 Jan 15;173(1-3):450-4. doi: 10.1016/j.jhazmat.2009.08.105. Epub 2009 Aug 31.
The aim of this work was to evaluate the stability of arsenic and selenium species retained in a lime/limestone mixture obtained by using limestone as a sorbent for gas cleaning in a coal gasification atmosphere. It was found that the stability of arsenic and selenium species produced by the gas-solid reactions with lime/limestone may be affected by their exposure to air and by their contact with water. The results confirm the conclusions of a previous work in which Ca(AsO(2))(2) and CaSe was postulated as the products of the reaction between the arsenic and selenium species present in a coal gasification atmosphere with lime/limestone. Moreover it was proved that the compounds (Ca(AsO(2))(2) and CaSe) may undergo transformations when the sorbents post-retention are stored or disposed of in air. From the results obtained by XAFS it was possible to identify the Ca(3)(AsO(4))(2) produced by the oxidation of the Ca(AsO(2))(2) on the sorbent surface. The XAFS results for selenium showed that the CaSe formed on the sorbent was transformed to form several species, but mainly elemental Se. These changes in the speciation of arsenic and selenium may explain the behavior of the sorbent post-retention during the water solubility test. Although the selenium compounds and the products that may originate from their decomposition in water are not toxic, in the case of arsenic, species like Ca(AsO(2))(2) and Ca(3)(AsO(4))(2) may lixiviate, and generate toxic arsenic compounds in solution that could pose a risk when the sorbent is finally disposed of.
本工作的目的是评估在煤气化气氛中用作气体净化吸附剂的石灰石中石灰/石灰石混合物保留的砷和硒形态的稳定性。研究发现，石灰/石灰石与气体固相反 应生成的砷和硒形态的稳定性可能受到其与空气的暴露和与水的接触的影响。研究结果证实了之前工作的结论，即 Ca(AsO(2))(2)和 CaSe 被认为是煤气化气氛中存在的砷和硒形态与石灰/石灰石反应的产物。此外，还证明了当吸附剂后保留时，化合物 (Ca(AsO(2))(2)和 CaSe)可能在储存或处置于空气中时发生转化。通过 XAFS 获得的结果表明，在吸附剂表面上，Ca(AsO(2))(2)的氧化生成了 Ca(3)(AsO(4))(2)。硒的 XAFS 结果表明，在吸附剂上形成的 CaSe 转化为形成了几种形态，但主要是元素硒。砷和硒形态的这种变化可能解释了后保留吸附剂在水溶性测试中的行为。虽然硒化合物和它们在水中分解可能产生的产物没有毒性，但在砷的情况下，像 Ca(AsO(2))(2)和 Ca(3)(AsO(4))(2)这样的物质可能会浸出，并在最终处置吸附剂时生成有毒的砷化合物，从而构成风险。
