Van Caneghem Jo, Verbinnen Bram, Cornelis Geert, de Wijs Joost, Mulder Rob, Billen Pieter, Vandecasteele Carlo
KU Leuven - Campus Group T, Andreas Vesaliusstraat 13, 3000 Leuven, Belgium.
KU Leuven - Campus Group T, Andreas Vesaliusstraat 13, 3000 Leuven, Belgium; KU Leuven - Department of Chemical Engineering, Willem de Croylaan 46, 3001 Leuven, Belgium.
Waste Manag. 2016 Aug;54:162-8. doi: 10.1016/j.wasman.2016.05.007. Epub 2016 May 20.
The leaching of Sb from waste-to-energy (WtE) bottom ash (BA) often exceeds the Dutch limit value of 0.32mgkg(-1) for recycling of BA in open construction applications. From the immobilization mechanisms described in the literature, it could be concluded that both Ca and Fe play an important role in the immobilization of Sb in WtE BA. Therefore, Ca and Fe containing compounds were added to the samples of the sand fraction of WtE BA, which in contrast to the granulate fraction is not recyclable to date, and the effect on the Sb leaching was studied by means of batch leaching tests. Results showed that addition of 0.5 and 2.5% CaO, 5% CaCl2, 2.5% Fe2(SO4)3 and 1% FeCl3 decreased the Sb leaching from 0.62±0.02mgkgDM(-1) to 0.20±0.02, 0.083±0.044, 0.25±0.01, 0.27±0.002 and 0.29±0.02mgkgDM(-1), respectively. Due to the increase in pH from 11.41 to 12.53 when 2.5% CaO was added, Pb and Zn leaching increased and exceeded the respective leaching limits. Addition of 5% CaCO3 had almost no effect on the Sb leaching, as evidenced by the resulting 0.53mgkgDM(-1) leaching concentration. This paper shows a complementary enhancement of the effect of Ca and Fe, by comparing the aforementioned Sb leaching results with those of WtE BA with combined addition of 2.5% CaO or 5% CaCl2 with 2.5% Fe2(SO4)3 or 1% FeCl3. These lab scale results suggest that formation of romeites with a high Ca content and formation of iron antimonate (tripuhyite) with a very low solubility are the main immobilization mechanisms of Sb in WtE BA. Besides the pure compounds and their mixtures, also addition of 10% of two Ca and Fe containing residues of the steel industry, hereafter referred to as R1 and R2, was effective in decreasing the Sb leaching from WtE BA below the Dutch limit value for reuse in open construction applications. To evaluate the long term effect of the additives, pilot plots of WtE BA with 10% of R1 and 5% and 10% of R2 were built and samples were submitted to leaching tests at regular intervals over time. The Sb leaching from untreated WtE BA was just below or above the Dutch limit value. The Sb leaching from the pilot plots of BA with additives first remained stable around 0.13mgkg(-1) but had a tendency to slightly increase after 6months, indicating the need for further research on the effect of weathering, and more specifically of carbonation, on Sb leaching from WtE BA.
在能源回收（WtE）底灰（BA）中，锑的浸出量常常超过荷兰规定的0.32mgkg⁻¹这一限值，该限值适用于在露天建筑应用中回收BA。从文献中描述的固定化机制可以得出结论，钙和铁在WtE BA中锑的固定化过程中都起着重要作用。因此，将含钙和铁的化合物添加到WtE BA砂粒部分的样品中（与颗粒部分不同，砂粒部分迄今为止不可回收利用），并通过批量浸出试验研究其对锑浸出的影响。结果表明，添加0.5%和2.5%的CaO、5%的CaCl₂、2.5%的Fe₂(SO₄)₃和1%的FeCl₃后，锑的浸出量分别从0.62±0.02mgkgDM⁻¹降至0.20±0.02、0.083±0.044、0.25±0.01、0.27±..002和0.29±0.02mgkgDM⁻¹。添加2.5%的CaO时，pH值从11.41升高到12.53，铅和锌的浸出量增加并超过了各自的浸出限值。添加5%的CaCO₃对锑的浸出几乎没有影响，浸出浓度为0.53mgkgDM⁻¹即可证明。通过将上述锑浸出结果与同时添加2.5%的CaO或5%的CaCl₂以及2.5%的Fe₂(SO₄)₃或1%的FeCl₃的WtE BA的结果进行比较，本文展示了钙和铁效应的互补增强。这些实验室规模的结果表明，高钙含量的钙锑矿的形成以及极低溶解度的锑酸铁（红锑铁矿）的形成是WtE BA中锑的主要固定化机制。除了纯化合物及其混合物外，添加10%的钢铁行业的两种含钙和铁的残渣（以下简称R1和R2）也能有效降低WtE BA中的锑浸出量，使其低于荷兰规定的在露天建筑应用中再利用的限值。为了评估添加剂的长期效果，建造了添加10%的R1以及5%和10%的R2的WtE BA试验田，并随着时间的推移定期对样品进行浸出试验。未经处理的WtE BA的锑浸出量略低于或高于荷兰限值。添加添加剂的BA试验田的锑浸出量最初在0.13mgkg⁻¹左右保持稳定，但6个月后有略微增加的趋势，这表明需要进一步研究风化作用，更具体地说是碳酸化作用，对WtE BA中锑浸出的影响。
