Study On The Mechanisms Of Contaminant Transport In Clay Under Electrical, Hydraulic And Chemical Gradients

Clay-liners are widely used in landfill for the power decontamination, low penetrability and low expense. The transport mechanisms of the contaminants are convection, dispersion, diffusion and adsorption. When a direct current electric field is applied across the soil, an electro-kinetic phenomenon is occurred. Electro-osmosis, electro-migration and electrophoresis are the main mechanisms. In this paper, the mechanisms of the contaminants are presented, it will help to know the contaminant transport rules through the clay and give a guide to choose the appropriate parameters.In this paper, the differential quadrature method is employed for the analysis of the one-dimensional advective-dispersive equation. The convergency analysis shows that the DQM computational results agree with those of the analytical solution when adopting 7-9 interpolations. The computational results indicate that DQM does have the advantage of numerical accuracy and computational efficiency in calculation of the one-dimensional transport equation. Due to the uniform matrix structure of the solution in this paper, it is convenient for comulating computational program and engineering practice. Using the obtained solutions, impacts of the main clay-liner parameters changes on contaminant distribution are discussed. The results of this paper can be used for preliminary design of landfill liners.The flows of contaminants under the influences of hydraulic, electrical and chemical gradients are a coupled process. This paper presents the coupled flow equations of contaminants and the design of a new apparatus specifically made to experimentally study on zinc ions transport in clay under coupled flows, and the concentration, water content and PH of the sample clay are measured respectively. The results show that electro-kinetic effect can prevent the transport of zinc ions through the clay.