一般工业固废复合固化重金属污染土的力学及电化学性能

Mechanical and Electrochemical Properties of Heavy Metal Contaminated Soil Solidified by Industrial Solid Wastes

针对中国一般工业固废大量堆存问题,以工业固体废物赤泥、电石渣和磷石膏的有效利用为导向,以处理铜污染土为目的,制备复合固化剂并对铜离子污染土进行固化处理。通过研究固化土的无侧限抗压强度性能,对比分析了纯水泥固化剂与添加工业固废复合固化剂对铜污染土的固化效果。通过研究固化土的电化学阻抗谱特性,建立了固化土的等效电路模型,并着重从物理力学性能和微观结构特性揭示工业固体废物之间的相互作用效果及其对铜污染土的固化机理。结果表明:固化土的无侧限抗压强度均随龄期逐渐增大,且固化土的浸出毒性均满足国家相关标准要求。在一般工业固废作用下,固化土强度高于相应纯水泥固化土。固化土电化学Nyquist曲线在高频区随养护龄期增加逐渐出现容抗弧,且其半径逐渐增大;低频区为斜直线,且斜率随养护龄期逐渐增大。此外,固化土的强度与电化学参数R ct1之间存在良好线性关系,可采用R ct1对固化土强度的发展进行无损预测。借助微观测试手段发现固化土在养护过程中生成了凝胶物质和针状物质,水化产物的生成是固化土强度发展的主要缘由,且其对铜离子有一定的吸附、包裹和离子置换作用。

Aiming at the problem of large-scale stockpiling of general industrial solid wastes in China,guided by the effective utilization of industrial solid wastes red mud,calcium carbide slag,and phosphogypsum,and for the purpose of copper-contaminated soil,a composite curing agent was prepared to cure copper ion contaminated soil.By studying the unconfined compression strength of solidified soil,the solidification effect of pure cement curing agent and industrial solid waste composite curing agent on copper-contaminated soil were compared and analyzed.By studying the electrochemical impedance spectroscopy characteristics of solidified soil,the equivalent circuit model of solidified soil was established,and the interaction effect between industrial solid wastes and the solidification mechanism of copper-contaminated soil was revealed from the physical and mechanical properties and microstructure characteristics.The results show that the unconfined compressive strength of solidified soil increases gradually with age,and the leaching toxicity of solidified soil meets the requirements of relevant national standards.Under the action of general industrial solid waste,the strength value of solidified soil is higher than that of the corresponding pure cement solidified soil.The electrochemical Nyquist curve of solidified soil gradually appears capacitive reactance arc in the high-frequency region with the increase of curing age,and its radius gradually increases.The low-frequency area is an oblique straight line,and the slope gradually increases with the curing age.In addition,there is a good linear relationship between the strength of solidified soil and the electrochemical parameter R ct1,which can be used to predict the strength development of solidified soil non-destructively.By means of a microscopic test,it is found that gel material and needle-like material are generated in the curing process of solidified soil.The formation of hydration products is the main reason for the unconfined compression strength development of solidified soil,and it has certain adsorption,wrapping and ion replacement effects on copper ions.