Experimental Study On Remediation Of Heavy Metal Contaminated Clay By Natural Cold Energy Combined With Chemical Washing

This paper is based on the Natural Science Foundation of China "Study of transport and remediation of specific heavy metal pollutants based on freezing and thawing".Through the large-scale indoor model test,the Unilateral freeze-thaw test and freeze-thaw leaching test were carried out.The effects of air temperature and water-replenishing conditions on the moisture migration of soil during freezing and the removal of heavy metal pollutants by freeze-thaw leaching were studied.The conclusion is as follows:Unilateral freeze-thaw test:(1)The step-by-step cooling mode can be used to control the temperature gradient of soil,and then affect the change and migration of water,so as to increase the water absorption of soil.In addition,the water absorption of soil in the freezing process can be increased by increasing the water supplement layer.(2)when the frozen front moves down stably,the water replenishing rate and frost heaving rate are large.When the frozen front’s moving speed is 0.5-0.9cm/day,the water-replenishing rate is the largest.Freeze-thaw leaching test:(1)With the increase of depth,the residual amount of pollutants decreases first and then increases.(2)In the freeze-thaw leaching test,the main removal states of Pb are the reducible and the residual;the main removal states of Cd are the weak acid extraction and...