Electro-osmotic strengthening of silts based on selected electrode materials

Electro-osmosis is considered promising in effectively strengthening silts. This has been an urgent issue for engineers as large volumes of silts are being generated each year and need to be properly disposed. Electrode material is one of the key elements for the electro-osmosis technique. Inconsistent results have been reported in the existing literature on common electrode materials. To clarify these discrepancies and to optimize the electrode material, laboratory tests were performed with four common materials, namely, iron, graphite, copper and aluminum, under three levels of voltage gradient. Observations were performed from the perspectives of the electro-osmotic effect and the ionic strength. As for the former perspective, the electro-osmotic effect was denoted by the drainage, the water content and the effective potential. The graphite electrode was found to perform better at high potentials than iron or copper. The copper electrode exhibited a rapid decrease in the effective potential and current. As for the latter perspective, contents of Fe, Cu and Al were detected in the drainage and soils. Aluminum ions were demonstrated to have higher migration capacities than iron or cupric ions. Further analysis determined that electro-osmosis relies on ions in the original soils instead of those generated by electrode reactions. In conclusion, iron is recommended as the preferable electrode material for electro-osmosis. The performance of different electrode materials is directly reflected by the voltage loss rather than by the ion migration process. The voltage loss can be attributed to various factors, such as corrosion, electrochemical passivation, gas evolution, decomposition and electrochemical potential. The results of this paper provide deep insight into the influence of the electrode material on the electro-osmotic process.