Influence of salt content on clay electro-dewatering with copper and stainless steel anodes

Abstract

The electro-dewatering technique is an effective method to reinforce soft clay. Electro-dewatering experiments were conducted to assess the impact of salt content on electro-dewatering behaviors and effects with copper and stainless steel anodes. The changes in the current, accumulated drainage volume, and electro-osmotic flow velocity reflect the “catch point” phenomenon between the copper anode and the stainless steel anode. Moreover, the higher the salt content was, the earlier the appearance of the “catch point,” which means that the effect of the copper anode was better in the early stages and then worse in the following stages than that of the stainless steel anode. Based on photographs of anode surface, SEM-EDS (Scanning electron microscopy-Energy dispersive spectrometry) and XRD (X-ray diffraction) results, we found that the copper anode surface produced green product, which observably decreased the conductivity of the copper anode and then reduced the effective electrical potential gradient. On the other hand, there were no added elements on the stainless steel anode surface after the electro-dewatering experiments, and the conductivity of the stainless steel anode was similar to its initial status. The above two points led to the appearance of the“catch point” phenomenon. The pH value of the stainless steel anode was lower than that of copper anode, and the concentration of Cl− had the opposite relationship. Because the effective electrical potential gradient of the stainless steel anode was higher than that of the copper anode after the “catch point,” the water content of the stainless steel anode was lower than that of the copper anode.