添加剂对蜈蚣草燃烧过程中砷迁移规律的影响

摘要

蜈蚣草是砷(As)的超富集植物,为了研究CaO、MgO以及白云石对蜈蚣草燃烧过程中砷迁移规律和赋存形态的影响,利用管式炉装置进行了一系列的实验,结果表明:3种添加剂在400～700℃温度区间固砷效果明显,MgO的固砷效果最佳、CaO其次、白云石最差.CaO和MgO的最佳固砷温度为500℃,最佳固砷效率分别为17％和14％;白云石的最佳固砷温度为700℃,最佳固砷效率为10％.燃烧温度在400～500℃时,掺混添加剂会使底灰中可溶砷的比例提高约5％,这是由于温度较低时,这3种添加剂主要是通过物理吸附对砷进行固定;而当温度超过800℃时,底灰中可溶砷的比例降低约10％,这是由于添加剂影响了底灰对砷的自固定,减少了可溶性砷化合物的形成.当温度低于700℃时,掺混添加剂会使底灰中出现少量As3+.%P.vittata is one of the hyperaccumulators of arsenic(As),a series of experiments were conducted in a horizontal tube furnace to investigate the influence of CaO,MgO and dolomite on the transformation behavior of As during the combustion of P vittata.The results showed that the As retention of CaO,MgO and dolomite was efficient during 400～700℃,and the MgO performed best,followed by CaO and dolomite.The most proper temperature of As retention of CaO and MgO was 500℃,while that was 700℃ for dolomite.It was found that the low temperature would promote the formation of soluble As when the additives were used,because the physical adsorption played the important role in low temperature zone.When the temperature exceeded 800℃,the content of soluble As in solid residue decreased,due to the influence of the additives on the self-retention of ash,where the additives would suppress the formation of soluble As compound.In addition,with the use of additives,a small amount of As3+ was found in the solid residue when the temperature was lower than 700℃.