有机物污染场地浅层异位固化稳定化试验研究

以某化工企业有机物污染浅层土为对象,应用4种固化药剂进行固化稳定化修复对比研究。通过现场异位固化稳定化结合室内无侧限抗压强度、毒性浸出等试验,讨论了固化剂组份、龄期对其物理力学性质和浸出特性影响,并对比分析了其固化稳定化效果及机理。结果表明:随着养护时间增长,修复土p H值、毒性浸出溶液的有机物浓度降低,其中pH值由0 d的12.76~13.11降至28 d时的12.11~12.69,而有机物浸出浓度14d降幅在65%~100%间;干密度及无侧限抗压强度qu则稳步提高,其中干密度28 d增幅达14.4%~23.2%,而强度最大增加到122 k Pa。固化剂3和4修复污染土干密度较大,28 d密度超过1.37 g/cm~3,密实作用明显;添加固化剂会立即显著增大污染土pH值,其中固化剂4(电石渣+凹凸棒土)各龄期pH值明显大于其他剂型;各固化剂对不同有机污染物的稳定效果有所差别,但均能有效固化稳定化苯胺、2-氯酚、萘、苯、甲苯、邻-二甲苯;就污染物总体固化稳定化效果而言,含活性炭组分的固化剂1效果最为突出,其总稳定率接近100%;含水泥组分的固化剂2,3对土体的增强作用较好,其28 d强度可达109 k Pa以上。相较其他药剂,固化剂4在成本、能耗及污染物排放方面表现最优,且能较好满足场地修复对有机物稳定率及强度的要求,综合效果最佳,为优选的最佳剂型。

Experimental study on ex-situ S/S for shallow soil of organically contaminated site

4 kinds of binders are utilized to remedy the organically contaminated soil. The effects of curing age and binder type on physico-mechanical and environmental safety properties of the stabilized soils as well as the remediation efficiencies and mechanisms are studied by analyzing the results of ex-situ S/S and laboratory tests, such as unconfined compression strength tests and toxicity characteristic leaching procedure. The results show that with the increasing age, pH of soil and organic concentrations of leachate decrease while the dry densities and q_u increase steadily. The dry densities of soil remedied by binders No. 3 and No. 4 are higher than those by other binders and over 1.38 g/cm³ after 28 days. The pH values of soil greatly increase with the addition of binders and are the highest for binder No. 4 (calcium carbide residue + attapulgite). 4 kinds of binders have different remediation effects on organic contaminants owing to different organic types, and they all have high removal efficiencies for aniline, 2-chlorophenol, naphthalene, benzene, methylbenzene and o-Xylene. In point of the overall effectiveness, activated carbon-based binder No. 1 is the best because its total removal efficiency approaches 93%. The q_u of soils stabilized by cement-based binders No. 2 and No. 3 is higher than that of other binders and over 109 kPa after 28 days. Binder No. 4 is optimum for the re-use of organically contaminated soil because of its low cost, low energy consumption, low pollutant emission, high q_u and total removal efficiency.