亚铁盐对城市污泥中重金属的稳定化作用研究

在不同的药剂投加条件下,通过对重金属的浸出系数和形态分布分析,研究了亚铁盐对污泥中重金属的稳定化效果.结果显示,单独投加亚铁盐时会导致污泥pH值降低,投加5%的硫酸亚铁时,污泥pH值由6.5骤降至4.4,污泥中锌和镍的浸出系数分别达到了363.3%和118.3%.投加亚铁盐辅助氢氧化钙稳定化污泥,能够将污泥pH值维持在偏碱性的范围内,且重金属的浸出系数显著降低.当投加15%的硫酸亚铁和7.5%的氢氧化钙时,锌和镍的浸出系数分别为11.5%和24.1%,污泥pH值为8.4.单独投加氢氧化钙可以有效地稳定污泥中的重金属,但会显著提高污泥的pH值,不利于污泥的后续资源化.在相同pH值条件下,硫酸亚铁和氢氧化钙同时投加的稳定化效果比单独投加氢氧化钙要好.重金属的形态分析表明,锌、铜和铅的稳定态增加,但镍、总铬和镉的不稳定态增加.

Stabilization of Heavy Metals in Sewage Sludge by Using a Ferrous Iron

The stabilization of heavy metals in sewage sludge using a ferrous iron is investigated through leaching test and fractionation analysis. The results showed that FeSO₄·7H₂O was not helpful to stabilize the heavy metals in the sludge when used individually since it reduced the pH value of sludge. The pH value dropped significantly from 6.5 to 4.4, and leaching coefficients of Zinc (Zn) and Nickel (Ni) raised, respectively, to 363.3% and 118.3% when FeSO₄·7H₂O was added individually at a ratio of 5%. However, it maintained the pH value within a slight alkaline range and the leaching coefficients of heavy metals reduced significantly when combined with Ca(OH)₂ as an auxiliary agent. The pH value of sludge kept to 8.4 and leaching coefficients of Zn and Ni were reduced to 11.5% and 24.1%, for example, when 15% FeSO₄·7H₂O and 7.5% Ca(OH)₂ were added together into the sludge. Besides, when Ca(OH)₂ was used individually, the pH value of the sludge raised highly although the heavy metals were stabilized effectively. Under same pH value, combined addition of FeSO₄·7H₂O and Ca(OH)₂ promoted the stabilization of heavy metals had a better effect than individual use of Ca(OH)₂. The fractionation analysis revealed that the stable species of Zn, Cu and Pb were increased, and the instable species of Ni, Cr and Cd were also raised.