酸溶液淋溶作用下重金属污染土固化体浸出特性及机理

采用KH_2PO_4—水泥复合材料对铅污染土进行固化/稳定化处理,为了研究酸雨淋溶对铅污染土固化体浸出特性的影响规律及其机理,开展了不同KH_2PO_4添加量、浸出时间和淋溶液pH对Pb浸出行为的影响规律试验研究。探讨了铅污染土固化体浸出机理。结果表明,KH_2PO_4对铅污染土有良好的稳定作用。酸溶液淋溶作用下固化体中Pb的释放行为与pH直接相关,强酸作用下Pb的溶出量大。固化体中Pb的浸出也与浸出液pH相关,强碱性有利于Pb的迁移。浸出液pH与固化体中的碱性水化产物释放量有关。对于pH=2和5溶液,Pb的累积浸出率随时间呈线性变化,而对于pH=3溶液,Pb的累积浸出率随时间呈两阶段线性变化。固化体在pH=2溶液浸泡下,Pb的释放机理为溶解控制;对于pH=3溶液浸泡,机理则为先溶解控制再表面冲刷;而对于pH=5溶液浸泡,Pb的释放机理为扩散控制。

Leaching characteristics and mechanism of heavy metal in solidified/ stabilized contaminated soil under acid solution soaking

KH₂PO₄—cement is used to soildify/stabilize the Pb contaminated soil. Leaching tests are conducted to study the leaching characteristics and mechanism of Pb in solidified bodies under acid rain soaking, and the effects of KH₂PO₄ addition, leaching time and leachate pH are took into account. The results show that KH₂PO₄ is effective to stabilize the Pb-contaminated soil. The Pb leaching is related to pH of leachant directly, and the leaching amount of Pb increases with acidity. What’s more, Pb leaching is also related to pH of leachate, and strong alkaline of leachate is conducive to the Pb mobility. For the acid solutions with pH of 2 and 5, the cumulative leaching ratio of Pb changes with time linearly, but the two-stage linear variation is founded for the acid solutions with pH of 3. pH of the leachate is in relation to the leaching amount of alkaline materials in S/S bodies. The controlling leaching mechanism of Pb changes with leachant pH, and it is presented that the leaching mechanism changes from dissolution to diffusion with the increasing leachant pH.