固化重金属铜镉污染底泥渗透特性试验研究

采用固化剂对含复合重金属铜镉污染底泥进行固化处理,对其渗透特性进行了研究。结果表明:在渗透液pH相同的条件下,重金属渗出量随着养护龄期的增加而减少;在相同的养护龄期条件下,Cu~(2+)在酸性条件下的渗出量大于在中性条件下的渗出量;Cd~(2+)在C—S—H凝胶固化中与HCO_3~-作用生成难溶于酸的Cd(HCO_3)_2化合物,使其渗出量较少。研究了不同污染物掺量对渗透系数k与污染物渗出总量的影响,得到Cu~(2+)掺量的质量分数小于等于0.75%,Cd~(2+)掺量的质量分数小于等于0.225%时,试样渗透系数k与污染物渗出总量同污染物掺量呈正相关;Cu~(2+)掺量的质量分数大于0.75%,Cd~(2+)掺量的质量分数大于0.225%时,其渗透系数k随着污染物掺量的增加反而减小。并通过扫描电镜分析了不同的污染物浓度对试样微观结构的影响,随着重金属浓度的提高,结构表面形成蜂窝状的重金属水化产物。

Experimental Study on the Permeability Property of Solidified Sludge Contaminated by Heavy Metal Cu and Cd

The curing agent was used to solidify the sludge contaminated by heavy metal Cu²⁺ and Cd²⁺, and its permeability property was studied. The testing results show that the amount of heavy metal in exudation fluid decreases with the increase of curing time under penetrant with the same pH value. The exudation of Cu²⁺ in acidic conditions is greater than that of neutral conditions under the same curing age. Based on the process of C-S-H gelation, Cd(HCO₃)₂ which is difficultly dissolved in acidic fluid is produced by Cd²⁺ and HCO₃^-, which leads to the few exudation amount of Cd²⁺. The effects of different amounts of heavy metals on the permeability coefficient k and the total exudation quantity of contaminants were investigated, which illustrates that the k and the total exudation concentration are positively related to the increased amount of pollutants when the mass fraction of Cu²⁺ is equal or less than 0.75% and the mass fraction of Cd²⁺ is equal or less than 0.225%. However, the k decreases with the increase of pollutant content when the mass fraction of Cu²⁺ is more than 0.75% and the mass fraction of Cd²⁺ is more than 0.225%. Besides, a scanning electron microscopy was used to analyze the effect of different pollutant concentration on the microstructure of the sample. With the increase of heavy metal concentration, on the structure surface form honeycomb heavy metal hydration products.